Papers for Wednesday, Jan 31 2024

Measuring the relation between star formation and galactic winds is observationally difficult. In this work we make an indirect measurement of the mass loading factor (the ratio between mass outflow rate and star formation rate) in low-mass galaxies using a differential approach to modeling the low-redshift evolution of the star-forming main sequence and mass-metallicity relation. We use the SAGA (Satellites Around Galactic Analogs) background galaxies, those spectra observed by the SAGA survey that are not associated with the main SAGA host galaxies, to construct a sample of 11925 spectroscopically confirmed low-mass galaxies from $0.01\lesssim z \leq 0.21$ and measure a auroral line metallicity for 120 galaxies. The crux of the method is to use the lowest redshift galaxies as the boundary condition of our model, and to infer a mass-loading factor for the sample by comparing the expected evolution of the low redshift reference sample in stellar mass, gas-phase metallicity, and star formation rate against the observed properties of the sample at higher redshift. We infer a mass-loading factor of $\eta_{\rm m}=0.92^{+1.76}_{-0.74}$, which is in line with direct measurements of the mass-loading factor from the literature despite the drastically different set of assumptions needed for each approach. While our estimate of the mass-loading factor is in good agreement with recent galaxy simulations that focus on resolving the dynamics of the interstellar medium, it is smaller by over an order of magnitude than the mass-loading factor produced by many contemporary cosmological simulations.

Classical gamma-ray bursts (GRBs) have two distinct emission episodes: prompt emission from ultra-relativistic ejecta and afterglow from shocked circumstellar material. While both components are extremely luminous in known GRBs, a variety of scenarios predict the existence of luminous afterglow emission with little or no associated high-energy prompt emission. We present AT 2019pim, the first secure example of this phenomenon to be identified. Serendipitously discovered during follow-up observations of a gravitational-wave trigger and located in a contemporaneous TESS sector, it is hallmarked by a fast-rising (t ~ 2 hr), luminous (M_UV,peak ~ -24.4 mag) optical transient with accompanying luminous X-ray and radio emission. No gamma-ray emission consistent with the time and location of the transient was detected by Fermi-GBM or by Konus, placing strong limits on an accompanying GRB. We investigate several independent observational aspects of the afterglow in the context of constraints on relativistic motion and find all of them are consistent with an initial Lorentz factor of Gamma_0 ~ 30-50, significantly lower than in any well-observed GRB and consistent with the theoretically-predicted "dirty fireball" scenario in which the high-energy prompt emission is stifled by pair production. However, we cannot rule out a structured jet model in which only the line-of-sight material was ejected at low-Gamma, off-axis from a classical high-Gamma jet core. This event represents a milestone in orphan afterglow searches, demonstrating that luminous afterglows with weak or no detectable gamma-ray radiation exist in nature and can be discovered by high-cadence optical surveys.

We present a new high-precision strong lensing model of PLCK G287.0$+$32.9, a massive lens galaxy cluster at $z=0.383$, with the aim to get an accurate estimation of its effective Einstein radius and total mass distribution. We also present a spectroscopic catalog containing accurate redshift measurements for 490 objects, including multiply-lensed sources and cluster member galaxies. We exploit high-quality spectroscopic data from three pointings of the VLT Multi Unit Spectroscopic Explorer, covering a central $3~\rm{arcmin}^2$ region of the cluster. We complete the spectroscopic catalog by including redshift measurements from VLT-VIMOS and KECK-DEIMOS. We identify 129 spectroscopic cluster member galaxies, with redshift values $0.360 \leq z \leq 0.405$ and $m_{\rm{F160W}} \leq 21$, and 24 photometric ones identified with a Convolutional Neural Network from ancillary HST imaging. We also identify 114 multiple images from 28 background sources, of which 84 images from 16 sources are new and the remaining ones were identified in previous work. The best-fitting lens model shows a root mean square separation value between the predicted and observed positions of the multiple images of $0.75''$, corresponding to an improvement in reconstructing the observed positions of the multiple images of a factor of $2.5$ with respect to previous models. Using the predictive power of our new lens model we find 3 new multiple images and we confirm the configuration of three systems of multiple images that were not used for the optimization of the model. The derived total mass distribution confirms this cluster to be a very prominent gravitational lens with an effective Einstein $\theta_{E} = \left( 43.41_{-0.06}^{+0.05} \right)''$, that is in agreement with previous estimates and corresponds to a total mass enclosed in the critical curve of $M_E = {3.33}_{-0.07}^{+0.02} \times{ 10^{14} M_\odot}$.

The recent discovery of ``ultra-hot'' ($P < 1$ day) Neptunes has come as a surprise: some of these planets have managed to retain gaseous envelopes despite being close enough to their host stars to trigger strong photoevaporation and/or Roche lobe overflow. Here, we investigate atmospheric escape in LTT 9779b, an ultra-hot Neptune with a volatile-rich envelope. We observed two transits of this planet using the newly-commissioned WINERED spectrograph ($R\sim68,000$) on the 6.5 m Clay/Magellan II Telescope, aiming to detect an extended upper atmosphere in the He 10830 A triplet. We found no detectable planetary absorption: in a 0.75 A passband centered on the triplet, we set a 2$\sigma$ upper limit of 0.12% ($\delta R_p/H < 14$) and a 3$\sigma$ upper limit of 0.20% ($\delta R_p/H < 22$). Using a H/He isothermal Parker wind model, we found corresponding 95% and 99.7% upper limits on the planetary mass-loss rate of $\dot{M} < 10^{10.03}$ g s$^{-1}$ and $\dot{M} < 10^{11.11}$ g s$^{-1}$ respectively, smaller than predicted by outflow models even considering the weak stellar XUV emission. The low evaporation rate is plausibly explained by a metal-rich envelope, which would decrease the atmospheric scale height and increase the cooling rate of the outflow. This hypothesis is imminently testable: if metals commonly weaken planetary outflows, then we expect that \textit{JWST} will find high atmospheric metallicities for small planets that have evaded detection in He 10830 A.

We update the publicly available weak lensing shear measurement algorithm pyRRG for the James Webb Space Telescope, and apply it to UNCOVER DR1 imaging of galaxy cluster Abell 2744. At short wavelengths (< 2.5$\mu$m), shear measurements are consistent between independent observations through different JWST bandpasses, and calibrated within 1.5% of those from the Hubble Space Telescope. At longer wavelengths, shear is underestimated by ~5%, probably due to coarser pixellisation. We model the spatially varying Point Spread Function (PSF) using WebbPSF, whose moments are within 0.05 of real stars near the centre of the mosaic, where there are sufficient stars to also generate an empirical model. We measure shear from up to 162 galaxies arcminute$^2$ to derive a map of (dark plus baryonic) mass with 12 arcsecond (55 kpc) spatial resolution. All code, catalogues and maps are available from https://github.com/davidharvey1986/pyRRG.

Compact Symmetric Objects (CSOs) are thought to represent the first step in the evolutionary path of radio galaxies. In this work, we investigate the X-ray emission of two CSOs confirmed to emit at GeV energies: PKS 1718-649 and TXS 1146+596. Unveiling the origin of their observed high-energy emission is crucial to establishing the physical parameters of the radio source and understanding how CSOs interact with the surrounding medium. We combined archival and new NuSTAR observations of PKS 1718-649 and TXS 1146+596 to have a broadband X-ray coverage. For both sources, we model the broadband spectral energy distribution, from radio band up to $\gamma$-rays, to derive their physical parameters. We also discuss the role of the ambient medium in confining the source expansion, which we investigate using X-ray obscuration. For the first time, we report on X-ray detections of PKS 1718-649 and 1146+596 with NuSTAR at energies higher than 10 keV. Combining Chandra and NuSTAR observations of TXS 1146+596, we reveal the presence of a multi-temperature thermal component dominating the soft X-ray spectrum, and we interpret this finding as indicative of an AGN feedback process in action in this source. In addition, we show that two emitting electrons populations are necessary to reproduce the observed broadband spectral energy distribution of TXS 1146+596: in our models, the X-ray emission could be produced either by synchrotron radiation or by a weak X-ray corona or an ADAF-type emission. Interestingly, an additional X-ray component, i.e. a weak corona, is also required for PKS 1718-649. Moreover, we argue that heavily obscured, and possibly frustrated, sources tend to show different radio sizes with respect to unobscured, free to expand, ones.

In this work we aim to determine the atmospheric survivability of the TRAPPIST-1 planets by modelling the response of the upper atmosphere to incoming stellar high-energy radiation. Through this case study, we also aim to learn more about rocky planet atmospheres in the habitable zone around low-mass M dwarfs. We simulated the upper atmospheres using the Kompot code, a self-consistent thermo-chemical code. Specifically, we studied the atmospheric mass loss due to Jeans escape induced by stellar high-energy radiation. This was achieved through a grid of models that account for the differences in planetary properties, irradiances, and atmospheric properties, allowing the exploration of the different factors influencing atmospheric loss. The present-day irradiance of the TRAPPIST-1 planets would lead to the loss of an Earth's atmosphere within just some 100 Myr. Taking into account the much more active early stages of a low-mass M dwarf, the planets undergo a period of even more extreme mass loss, regardless of planetary mass or atmospheric composition. This indicates that it is unlikely that any significant atmosphere could survive for any extended amount of time around any of the TRAPPIST-1 planets. The assumptions used here allow us to generalise the results, and we conclude that the results tentatively indicate that this conclusion applies to all Earth-like planets in the habitable zones of low-mass M dwarfs.

Sun-like stars are thought to accrete most of their final mass during the protostellar phase, during which the stellar embryo is surrounded by an infalling dense envelope. We present an analysis of 26 $K$-band spectra of Class 0 protostars, which are the youngest protostars. 18 of these are new observations made with the Keck MOSFIRE instrument. HI Br$\gamma$ , several H$_2$, and CO $\Delta\,v\;=\;2$ features are detected and analyzed. We detect Br$\gamma$ emission in 62%, CO overtone emission in 50%, and H$_2$ emission in 90% of sources. The HI and CO emission is associated with accretion while the H$_2$ lines are consistent with shock excitation indicating jets/outflows. Six objects exhibit photospheric absorption features, with almost no outflow activity, and no detection of the accretion-related Br$\gamma$ emission line. Comparing these results with archival sample of Class I $K$-band spectra, we find that the CO and Br$\gamma$ emission lines are systematically more luminous in Class 0s, suggesting the accretion is on average more vigorous in the Class 0 phase. Typically associated with the heated inner accretion disk, the much higher detection rate of CO overtone emission in Class 0s indicate also that episodes of high accretion activity are more frequent in Class 0 systems. The kinematics of the Class 0 CO overtone emission suggest either an accretion-heated inner disk, or material directly infalling onto the central region. This could point toward an accretion mechanism of different nature in Class 0 systems than the typical picture of magnetospheric accretion.

For more than 25 years, the Instituto Argentino de Radioastronom\'ia has been directing efforts from basic research and radio astronomy development to technology transfer projects around Argentina's National Space Plan and to Small and Medium Enterprises. With the surge of COVID-19, our organization's transformation accelerated, bringing new opportunities and challenges which can be applied to impact health, education, processes and businesses. In this article, we explore our efforts to bridge the gap between basic science and the needs of our society.

We present mock JWST observations for more than 215,000 different galaxies from the Astrid simulation with $3 \leq z \leq 6$. The mock observations are made using the BPASS stellar SED model, and a simple dust model. They are then viewed through NIRCam filters, convolved with a PSF, have noise added, and are drizzled together to emulate the Cosmic Evolution Early Release Science (CEERS) survey. We analyse this dataset by computing a number of morphological measures and find our catalog to have comparable statistics to similar mock catalogs, and the first release of CEERS data. We find that most of the Sersic indices of galaxies in our redshift range are lower than observed, with most having n less than one. Additionally, we observe the sizes of galaxies of all masses to increase from redshift z=6 to redshift z=3 consistent with other results. The number of galaxies in our catalog allows us to examine how relationships like the mass-size relation evolve with redshift, and compare the accuracy of a variety of traditional galaxy classification techniques (Sersic fit, Asymmetry-Concentration, and Gini-$M_{20}$) within our redshift range. We find the mass-size relation to be nearly flat at redshift z=6, and consistently increases as redshift decreases, and find the galaxy classification methods have minimal correlation with each other in our redshift range. We also investigate the impact that different stages of our imaging pipeline have on these morphological measures to determine how robust mock catalogs are to different choices at each step. Finally, we test the addition of incorporating light from AGNs into our pipeline and find that while the population of galaxies that have significant AGN luminosity is low, those galaxies do tend to have higher Sersic indices once the AGN luminosity is added, rectifying some of the systematic bias towards lower Sersic indices present in our dataset.

As the brightest galaxy cluster in the X-ray sky, Perseus is an excellent target for studying the Intracluster Medium (ICM), but until recently, its active galactic nucleus (AGN) made studies of the diffuse emission near its center nearly impossible to accomplish with NuSTAR due to the extended wings of NuSTAR's PSF. The development of a new open source software package -- nucrossarf -- now allows the contribution from point and diffuse sources to be modeled so that scattered light from the AGN can be accounted for. Using this technique, we present an analysis of diffuse hard X-ray (3-25keV) emission from the ICM using three archival NuSTAR observations of the Perseus cluster. We find a ~10% excess of emission beyond 20keV not describable by purely thermal models. By performing similar analyses of AGN in archival observations, we have characterized the systematic uncertainty of the modeled AGN contribution to be 3.4%. However, in order to explain the excess, the total scattered AGN emission would have to be 39% stronger than we have measured. We test physical explanations for the excess, such as diffuse inverse Compton emission potentially originating from the radio mini-halo, but we determine that none of the models are compelling. An upper limit on inverse Compton flux ($\leq1.5\times10^{-11}$erg s$^{-1}$cm$^{-2}$) and a corresponding lower limit on global magnetic field strength ($\geq 0.35~\mu G$) is derived. We discuss the potential origin and implications of the excess and present our characterization of the nucrossarf systematic uncertainty, which should be useful for future work.

Tens of thousands of galaxy-galaxy strong lensing systems are expected to be discovered by the end of the decade. These will form a vast new dataset that can be used to probe subgalactic dark matter structures through its gravitational effects, which will in turn allow us to study the nature of dark matter at small length scales. This work shows how we can leverage machine learning to search through the data and identify which systems are most likely to contain dark matter substructure and thus can be studied in greater depth. We use a UNet, an image segmentation architecture, on a simulated strongly-lensed dataset with realistic sources (COSMOS galaxies), lenses (power-law elliptical profiles with multipoles and external shear), and noise. Our machine learning algorithm is able to quickly detect most substructure at high image resolution and subhalo concentration. At a false positive rate of $10\%$, we are able to identify systems with substructure at a true positive rate of $71\%$ for a subhalo mass range of $10^{9}\text{-}10^{9.5}\,M_\odot$. While recent detections are consistent with higher concentrations, we find that our algorithm fails at detecting subhalos with lower concentrations (expected from $\Lambda$CDM simulations).

The inclination angle of substructures in active galaxies gives insights into physical components from scales of the vicinity of the central black hole to the entire host galaxy. We use the self-consistent reflection spectral model \textsc{RELXILL} to measure the inclination of the inner region of accretion disks with broadband ($0.3-78\,\rm keV$) X-ray observations, systematically studying the reliability of this methodology. To test the capability of the model to return statistically consistent results, we analyze multi-epoch, joint XMM-Newton and NuSTAR data of the narrow-line Seyfert~1 galaxy I\,Zwicky\,1 and the broad-line radio galaxy 3C\,382, which exhibit different degrees of spectral complexity and reflection features. As expected, we find that adding more data for analysis narrows the confidence interval and that multi-epoch, joint observations return optimal measurements; however, even single-epoch data can be well-fitted if the reflection component is sufficiently dominant. Mock spectra are used to test the capability of \textsc{RELXILL} to recover input parameters from typical single-epoch, joint observations. We find that inclination is well-recovered at 90\% confidence, with improved constraints at higher reflection fraction and higher inclination. Higher iron abundance and corona temperature tighten the constraints as well, but the effect is not as significant as a higher reflection fraction. The spin, however, have little effect in reflection-based inclination measurements. We conclude that broadband reflection spectroscopy can reliably measure inner accretion disk inclination.

A novel, data-driven model of deflagration-to-detonationtransition (DDT) is constructed for application to explosions of thermonuclear supernovae (SN Ia). The DDT mechanism has been suggested as the necessary physics process to obtain qualitative agreement between SN Ia observations and computational explosion models. This work builds upon a series of studies of turbulent combustion that develops during the final stages of the SN explosion. These studies suggest that DDT can occur in the turbulerized flame of the white dwarf via the Zel'dovich reactivity gradient mechanism when hotspots are formed. We construct a large database of direct numerical simulations that explore the parameter space of the Zel'dovich initiated detonation. We use this database to construct a neural network classifier for hotspots. The classifier is integrated into our supernova simulation code, FLASH/Proteus, and is used as the basis for a subgrid-scale model for DDT. The classifier is evaluated both in the training environment and in reactive turbulence simulations to verify its accuracy in realistic conditions.

Type Ia supernova (SN Ia) as a standard candle is an ideal tool to measure cosmic distance and expansion history of the Universe. Here we investigate the SN Ia photometric measurement in the China Space Station Telescope Ultra Deep Field (CSST-UDF) survey, and study the constraint power on the cosmological parameters, such as the equation of state of dark energy. The CSST-UDF survey is expected to cover a 9 deg$^2$ sky area in two years with 60 exposures. The magnitude limit can reach $i\simeq26$ AB mag for 5$\sigma$ point source detection. We generate light curve mock data for SNe Ia and different types of core-collapse supernovae (CCSNe), based on the relevant SN SED templates, natural generation rates, luminosity functions, CSST instrumental design and survey strategy. After selecting high-quality data and fitting the light curves, we derive the light curve parameters and identify CCSNe as contamination, resulting in $\sim2200$ SNe with a $\sim7\%$ CCSN contamination rate. We adopt a calibration method similar to Chauvenet's criterion, and apply it to the distance modulus data to further reduce the contamination. We find that this method is effective and can suppress the contamination fraction to $\sim3.5\%$ with 2012 SNe Ia and 73 CCSNe. About 16\% of SNe Ia are at $z>1$ in the final CSST-UDF SN sample. By checking the cosmological constraints, the result derived from this calibrated SN sample is in good agreement with that using the pure SN Ia sample. The constraint accuracies on $\Omega_{\rm M}$, $\Omega_{\Lambda}$ and $w$ are about $10\%\sim20\%$, which is about two times better than the current SN surveys, and it could be further improved by a factor of $\sim$1.4 if including the baryon acoustic oscillation (BAO) data from the CSST spectroscopic survey. This indicates that CSST can provide accurate measurements for the cosmic expansion history and the nature of dark energy.

We explore the chemodynamical properties of the Galaxy in the azimuthal velocity $V_\phi$ and metallicity [Fe/H] space using red giant stars from Gaia Data Release 3. The row-normalized $V_\phi$-[Fe/H] maps form a coherent sequence from the bulge to the outer disk, clearly revealing the thin/thick disk and the Splash. The metal-rich stars display bar-like kinematics while the metal-poor stars show dispersion-dominated kinematics. The intermediate-metallicity population ($-1<$[Fe/H]$<-0.4$) can be separated into two populations, one that is bar-like, i.e. dynamically cold ($\sigma_{V_R}\sim80$ $\rm km\ s^{-1}$) and fast rotating ($V_\phi\gtrsim100$ $\rm km\ s^{-1}$), and the Splash, which is dynamically hot ($\sigma_{V_R}\sim110$ $\rm km\ s^{-1}$) and slow rotating ($V_\phi\lesssim100$ $\rm km\ s^{-1}$). We compare the observations in the bulge region with an Auriga simulation where the last major merger event concluded $\sim10$ Gyr ago: only stars born around the time of the merger reveal a Splash-like feature in the $V_\phi$-[Fe/H] space, suggesting that the Splash is likely merger-induced, predominantly made-up of heated disk stars and the starburst associated with the last major merger. Since the Splash formed from the proto-disk, its lower metallicity limit coincides with that of the thick disk. The bar formed later from the dynamically hot disk with [Fe/H] $>-1$ dex, with the Splash not participating in the bar formation and growth. Moreover, with a set of isolated evolving $N$-body disk simulations, we confirm that a non-rotating classical bulge can be spun up by the bar and develop cylindrical rotation, consistent with the observation for the metal-poor stars.

The eruption of solar filaments, also known as prominences appearing off-limb, is a common phenomenon in the solar atmosphere. It ejects massive plasma and high-energy particles into interplanetary space, disturbing the solar-terrestrial environment. It is vital to obtain the three-dimensional velocity fields of erupting filaments for space-weather predictions. We derive the three-dimensional kinematics of an off-limb prominence and an on-disk filament, respectively, using the full-disk spectral and imaging data detected by the Chinese H$\alpha$ Solar Explorer (CHASE). It is found that both the prominence and the filament experience a fast semicircle-shaped expansion at first. The prominence keeps propagating outward with an increasing velocity until escaping successfully, whereas the south leg of the prominence finally moves back to the Sun in a swirling manner. For the filament, the internal plasma falls back to the Sun associated with an anticlockwise rotation in the late ejection, matching the failed eruption without a coronal mass ejection. During the eruptions, both the prominence and the filament show material splitting along the line-of-sight direction, revealed by the bimodal H$\alpha$ spectral profiles. For the prominence, the splitting begins at the top and gradually spreads to almost the whole prominence with a fast blue-shift component and a slow red-shift component. The material splitting in the filament is more fragmental. As shown by the present results, the CHASE full-disk spectroscopic observations make it possible to systematically study the three-dimensional kinematics of solar filament eruptions.

It was recently discovered that the time correlations of repeating fast radio bursts (FRBs) are similar to the properties of earthquake aftershocks. Motivated by the association between FRBs and magnetars, here we report two-point correlation function analyses in the time-energy space for the 563 periodic radio pulses detected by FAST and the 579 X-ray short bursts detected by NICER from the magnetar SGR 1935+2154, which is known to have generated FRBs. Although radio pulses are concentrated near the fixed phase of the rotational cycle, we find that when multiple pulses occur within a single cycle, their correlation properties (aftershock production probability, aftershock rate decaying in power of time, and more) are similar to those of extragalactic FRBs and earthquakes. A possible interpretation is that the radio pulses are produced by rupture of the neutron star crust, and the first pulse within one cycle is triggered by external force or torque periodically exerted on the crust. The source of the periodic external force may be the interaction of the magnetosphere with the material ejected in an outburst. For X-ray bursts, we found no significant correlation signal. The similarity in the aftershock nature between the periodic radio pulsation and FRBs is surprising, given that the two are energetically very different, and therefore the energy sources would be different. This suggests that the essence of FRB-like phenomena is starquakes, regardless of the energy source, and it is important to search for FRB-like bursts from neutron stars with various properties or environments.

We present a long-term X-ray study of a nearby Active Galactic Nucleus Mrk 6, utilizing observations from XMM-Newton, Suzaku, Swift and NuSTAR observatories, spanning 22 years from 2001 to 2022. From timing analysis, we estimated variance, normalized variance, and fractional rms amplitude in different energy bands.The temporal study shows fractional rms amplitude ($F_{\rm var}$) below $10\%$ for the shorter timescale $(\sim60 ~\rm ks)$ and above $20\%$ for the longer timescale ($\sim \rm weeks$ ). A complex correlation is observed between the soft $(0.5-3.0$ keV) and hard $(3.0-10.0$ keV) X-ray bands of different epochs of observations. This result prompts a detailed investigation through spectral analysis, employing various phenomenological and physical models on the X-ray spectra. Our analysis reveals a heterogeneous structure of the obscuring material surrounding Mrk 6. A partially ionized absorber exhibits a rapid change in location and extends up to the narrow line regions or torus. In contrast, another component, located far from the central engine, remained relatively stable. During the observation period, the source luminosity in the 3.0--10.0 keV range varies between $(3-15) \times10^{42}$ erg $\rm sec^{-1}$.

Magnetars, whose magnetic fields are strongest in the neutron stars, show diverse bursting activities. The shape of the magnetar deviates from an exactly pure spherical shape because of its strong magnetic field, and it can be a triaxial body. We study the free precession of the triaxial magnetar focusing on the unstable situation, in which the main rotation axis turns upside-down. This flip is the so-called Dzhanibekov effect. We find that during the flip, the Euler force can suddenly disturb the force balance on the magnetar surface, which may result in a crack at the surface. We suggest that the crack can trigger bursting activities of the magnetar, such as X-ray short bursts and flares with sufficiently large baryon fractions. In the burst with a large baryon fraction, right- or left-handed circularly polarized photons are selectively scattered, depending on the magnetic field direction. The association between the flip and the X-ray bursts will be confirmed by the observations of X-ray circular polarization. We also discuss the association of fast radio bursts, ultrahigh-energy cosmic rays, and gravitational waves.

A stellar-mass black hole (BH) or a millisecond magnetar is believed to be born as the central engine of Gamma-ray bursts (GRBs). The presence of plateaus in the X-ray extended emission or afterglow of GRBs is widely accepted as an indicator of magnetar central engine, particularly those with a sharp decay (faster than $t^{-3}$), so-called internal plateau. However, an alternative model, by taking the evolution of the magnetic flux at the BH horizon into account, suggests that an internal plateau can also arise from a Blandford-Znajek (BZ) mechanism powered jet (hereafter referred to as the BZ jet). In this study, we propose that a precessional BZ jet would manifest a Quasi-Periodic Oscillation (QPO) signature on the internal plateau and the subsequent sharp decay. Such lightcurves cannot be readily explained by the activity of a short-lived, supermassive magnetar, thus favoring a Kerr BH as the central engine. The X-ray afterglow of GRB 050904, comprising nine flares, is characterized by a QPO-modulated plateau and sharp decay, which can be well reproduced by a precessional BZ jet model. Therefore, one potential clue for distinguishing between these two engines lies in whether QPO signature throughout the entire plateau and the subsequent sharp decay, as the magnetar scenario suggests a collapse at the end of the plateau.

Population III (pop III) stars were born in halos characterised by a pristine gas composition. In such a halo, once the gas density reaches n$_{\mathrm{H}} \sim$ 1 cm$^{-3}$, molecular cooling leads to the collapse of the gas and the birth of pop III stars. Halo properties, such as the chemical abundances, mass, and angular momentum can affect the collapse of the gas, thereby leading to the pop III initial mass function (IMF) of star formation. We want to study the properties of primordial halos and how halos that host early star formation differ from other types of halos. The aim of this study is to obtain a representative population of halos at a given redshift hosting a cold and massive gas cloud that enables the birth of the first stars. We investigated the growth of primordial halos in a $\Lambda$CDM Universe in a large cosmological simulation. We used the hydrodynamic code RAMSES and the chemical solver KROME to study halo formation with non-equilibrium thermochemistry. We then identified structures in the dark and baryonic matter fields, thereby linking the presence or absence of dense gas clouds to the mass and the physical properties of the hosting halos. In our simulations, the mass threshold for a halo for hosting a cold dense gas cloud is $\simeq 7 \times 10^5 M_{\odot}$ and the threshold in the H$_2$ mass fraction is found to be $\simeq 2 \times 10^{-4}$. This is in agreement with previous works. We find that the halo history and accretion rate play a minor role. Here, we present halos with higher HD abundances, which are shown to be colder, as the temperature in the range between $10^2 - 10^4 \, \mathrm{cm^{-3}}$ depends on the HD abundance to a large extent. The higher fraction of HD is linked to the higher spin parameter that is seen for the dense gas.

Understanding the magnetic fields of the Sun is essential for unraveling the underlying mechanisms driving solar activity. Integrating topological data analysis techniques into these investigations can provide valuable insights into the intricate structures of magnetic fields, enhancing our comprehension of solar activity and its implications. In this study, we explore what persistent homology can offer in the analysis of solar magnetograms, with the objective of introducing a novel tool that will serve as the foundation for further studies of magnetic structures at the solar surface. By combining various filtration methods of the persistent homology analysis, we conduct an analysis of solar magnetograms that captures the broad magnetic scene, involving a mixture of positive and negative polarities. This analysis is applied to observations of both quiet Sun and active regions, taken with Hinode/SOT and SDO/HMI, respectively. Our primary focus is on analyzing the properties of the spatial structures and features of the magnetic fields identified through these techniques. The results show that persistent diagrams can encode the spatial structural complexity of the magnetic flux of active regions by identifying the isolated, connected, and interacting features. They facilitate the classification of active regions based on their morphology and the detection and quantification of interacting structures of opposing polarities, such as $\delta$-spots. The small-scale events in the quiet Sun, such as magnetic flux cancellation and emergence, are also revealed in persistent diagrams and can be studied by observing the evolution of the plots and tracking the relevant features.

Polar vortices are common in the atmospheres of rapidly rotating planets [1-4]. On Earth and Mars they are tied to the surface and their existence follows the seasonal insolation cycle [1-3]. Venus is a slowly rotating planet but it is also known to have vortices at both poles at the edge of a superrotating atmosphere [5-8]. However, their nature and long-term properties have not been constrained so far impeding precise modeling. Here we report cloud motions at two altitude levels (about 42 km and 63 km above the surface) using infrared images from the VIRTIS instrument onboard Venus Express that show that the south polar vortex is a permanent but erratic and unpredictable feature. We find that the centers of rotation of the vortex at these levels rarely coincide and both wander erratically around the pole with speeds of up to 16 m s-1. The cloud morphology and vorticity patches are uncorrelated and change continuously developing transient areas of small vertical motions. Venus south polar vortex is a continuously evolving structure immersed in a baroclinic environment laying at altitude levels that have variable vertical and meridional wind shears, extending at least 20 km in height through a quasi-convective turbulent region.

The Hunting Outbursting Young Stars (HOYS) project performs long-term, optical, multi-filter, high cadence monitoring of 25 nearby young clusters and star forming regions. Utilising Gaia DR3 data we have identified about 17000 potential young stellar members in 45 coherent astrometric groups in these fields. Twenty one of them are clear young groups or clusters of stars within one kiloparsec and they contain 9143 Gaia selected potential members. The cluster distances, proper motions and membership numbers are determined. We analyse long term (about 7yr) V, R, and I-band light curves from HOYS for 1687 of the potential cluster members. One quarter of the stars are variable in all three optical filters, and two thirds of these have light curves that are symmetric around the mean. Light curves affected by obscuration from circumstellar materials are more common than those affected by accretion bursts, by a factor of 2-4. The variability fraction in the clusters ranges from 10 to almost 100 percent, and correlates positively with the fraction of stars with detectable inner disks, indicating that a lot of variability is driven by the disk. About one in six variables shows detectable periodicity, mostly caused by magnetic spots. Two thirds of the periodic variables with disk excess emission are slow rotators, and amongst the stars without disk excess two thirds are fast rotators - in agreement with rotation being slowed down by the presence of a disk.

Extreme emission line galaxies (EELGs) exhibit large equivalent widths (EW) in their rest-optical emission lines ([OIII]$\lambda5007$ or H$\alpha$ rest-frame EW$ > 750\r{A}$) which can be tied to a recent upturn in star formation rate, due to the sensitivity of the nebular line emission and the rest-optical continuum to young ($<10$Myr) and evolved stellar populations, respectively. By studying a sample of 85 star forming galaxies (SFGs), spanning the redshift and magnitude interval $3 <z<9.5$ and $-16>$ M$_{UV}>-21$, in the JWST Advanced Deep Extragalactic Survey (JADES) with NIRSpec/prism spectroscopy, we determine that SFGs initiate an EELG phase when entering a significant burst of star formation, with the highest EWs observed in EELGs with the youngest mass-weighted ages ($<5$ Myr old) and the highest burst intensity (those with the highest proportion of their total stellar mass formed in the last 10 Myr). We spectroscopically confirm that a greater proportion of SFGs are in an EELG phase at high redshift in our UV-selected sample ($61\pm4\%$ in our $z>5.7$ high-redshift bin, compared to $23^{+4}_{-1}\%$ in our lowest-redshift bin $3<z<4.1$) due to the combined evolution of metallicity, ionisation parameter and star formation histories (SFH) with redshift. We report that the EELGs within our sample exhibit a higher average ionisation efficiency ($\log_{10}(\xi_{ion}^{HII}/$erg$^{-1}$Hz)$=25.5\pm0.2$) than the non-EELGs. High-redshift EELGs therefore comprise a population of efficient ionising photon producers. Additionally, we report that $53\%$ (9/17) of EELGs at $z>5.7$ have observed Lyman-$\alpha$ emission, potentially lying within large ionised regions. The high detection rate of Lyman-$\alpha$ emitters in our EELG selection suggests that the physical conditions associated with entering an EELG phase also promote the escape of Lyman-$\alpha$ photons.

Pulsations of rapidly oscillating Ap stars and their interaction with the stellar magnetic field have not been studied in the near-IR region despite the benefits these observations offer compared to visual wavelengths. The main advantage of the near-IR is the quadratic dependence of the Zeeman effect on the wavelength, as opposed to the linear dependence of the Doppler effect. To test pulsation diagnostics of roAp stars in the near-IR, we aim to investigate the pulsation behaviour of one of the brightest magnetic roAp stars, $\gamma$Equ, which possesses a strong surface magnetic field of the order of several kilogauss and exhibits magnetically split spectral lines in its spectra. Two magnetically split spectral lines belonging to different elements, the triplet Fe I at 1563.63nm and the pseudo-doublet Ce III at 1629.2nm, were recorded with CRIRES+ over about one hour in the H band with the aim of understanding the character of the line profile variability and the pulsation behaviour of the magnetic field modulus. The profile shapes of both studied magnetically split spectral lines vary in a rather complex manner probably due to a significant decrease in the strength of the longitudinal field component and an increase in the strength of the transverse field components over the last decade. A mean magnetic field modulus of 3.9kG was determined for the Fe I, whereas for the Ce III we observe only about 2.9kG. For comparison, a mean field modulus of 3.4kG was determined using the Zeeman doublet Fe II at 6249.25 in optical PEPSI spectra recorded just about two weeks before the CRIRES+ observations. Different effects that may lead to the differences in the field modulus values are discussed. Our measurements of the mean magnetic field modulus using the line profiles recorded in different pulsational phase bins suggest a field modulus variability of 32G for the Fe I and 102G for the Ce III.

Imaging Atmospheric Cherenkov Telescopes (IACTs) of gamma ray observatory TAIGA detect the Extesnive Air Showers (EASs) originating from the cosmic or gamma rays interactions with the atmosphere. Thereby, telescopes obtain images of the EASs. The ability to segregate gamma rays images from the hadronic cosmic ray background is one of the main features of this type of detectors. However, in actual IACT observations simultaneous observation of the background and the source of gamma ray is needed. This observation mode (called wobbling) modifies images of events, which affects the quality of selection by neural networks. Thus, in this work, the results of the application of neural networks (NN) for image classification task on Monte Carlo (MC) images of TAIGA-IACTs are presented. The wobbling mode is considered together with the image adaptation for adequate analysis by NNs. Simultaneously, we explore several neural network structures that classify events both directly from images or through Hillas parameters extracted from images. In addition, by employing NNs, MC simulation data are used to evaluate the quality of the segregation of rare gamma events with the account of all necessary image modifications.

In this study, we explored the impact of isolated and group environments on stellar mass, star formation rate (SFR), and specific star formation rate (SSFR, i.e., the rate of star formation per unit stellar mass) using the galaxy dataset from the Sloan Digital Sky Survey Data Release 12 (SDSS DR12) for $z\lesssim0.2$. To mitigate the Malmquist bias, we partitioned the entire dataset into fifteen subsamples with a redshift bin size of $\Delta z = 0.01$ and examined the environmental dependencies of these properties within each redshift bin. A strong correlation between environment, stellar mass, SFR, and SSFR was observed across nearly all redshift bins. In the lower redshift bins $(z<0.1)$, the proportion of galaxies within the isolated environment exceeded that within the group environment. On the other hand, in the higher redshift bins $(z\geq 0.12)$, the isolated environment's galaxy fraction is found to be lower than that of the group environment. For the intermediate redshift bins $(0.1 \leq z < 0.12)$, an approximately equal proportion of galaxies is observed in both isolated and group environments.

We investigate the prospect of reconstructing the ``cosmic distance ladder'' of the Universe using a novel deep learning framework called LADDER - Learning Algorithm for Deep Distance Estimation and Reconstruction. LADDER is trained on the apparent magnitude data from the Pantheon Type Ia supernovae compilation, incorporating the full covariance information among data points, to produce predictions along with corresponding errors. After employing several validation tests with a number of deep learning models, we pick LADDER as the best performing one. We then demonstrate applications of our method in the cosmological context, that include serving as a model-independent tool for consistency checks for other datasets like baryon acoustic oscillations, calibration of high-redshift datasets such as gamma ray bursts, use as a model-independent mock catalog generator for future probes, etc. Our analysis advocates for interesting yet cautious consideration of machine learning applications in these contexts.

Intermediate mass black holes (IMBHs, $\sim 10^2-10^5M_{\odot}$) are often dubbed as the missing link between stellar mass ($\lesssim 10^2M_{\odot}$) and super-massive ($\gtrsim 10^{5-6} M_{\odot}$) black holes. Observational signatures of these can result from tidal disruption of white dwarfs (WDs), which would otherwise be captured as a whole by super-massive black holes. Recent observations indicate that IMBHs might be rapidly spinning, while it is also known that isolated white dwarfs might have large spins, with spin periods of the order of minutes. Here, we aim to understand the effects of ``coupling'' between black hole and stellar spin, focussing on the tidal disruption of spinning WDs in the background of spinning IMBHs. Using smoothed particle hydrodynamics, we perform a suite of numerical simulations of partial tidal disruptions, where spinning WDs are in eccentric orbits about spinning IMBHs. We take a hybrid approach, where we integrate the Kerr geodesic equations while being in a regime where we can treat the internal stellar fluid dynamics in the Newtonian limit. We find substantial effects of the ``coupling'' between the black hole spin and the spin of the white dwarf, although the pericenter distance of the white dwarf is taken to be large enough so that the Newtonian limit of its fluid dynamics is a robust approximation. In particular, the core mass, the bound tail mass, and the mass difference between the two tidal tails strongly depend on such ``coupled'' spin effects. However, the late time fallback rate of the debris behaves similar to the non-spinning cases. We also compute gravitational wave amplitudes and find that while the black hole spin influences the same, there is no evidence of influence of stellar spin on such amplitudes in our regime of interest.

Venus Express provided a long-term monitoring of Venus atmosphere. Several works focused on the dynamics of the upper cloud visible on the day-side in ultraviolet images sensitive to the 65-70 km altitude and in the lower cloud level (50 km height) observable in the night-side of the planet in 1.74 microns. Here we use VIRTIS-M spectral images to study the upper cloud layer in ultraviolet (360-400 nm), visible (570-680 nm) and near infrared (900-955 nm) extending in time previous analysis of VIRTIS-M data. UV images show relatively well contrasted cloud features at the cloud top. Cloud features in the visible and near infrared images lie a few kilometers below the upper cloud top, have low contrast and are distinct to the features observed in the uv. Wind measurements were obtained over a six-year period using a semi-automatic cloud correlation algorithm. Results for the upper cloud confirm analysis based on images obtained by the Venus Monitoring Camera (Khatuntsev et al. 2013). At the cloud top the mean zonal and meridional winds vary with local time accelerating towards the local afternoon. The upper branch of the Hadley cell reaches maximum velocities at 45deg latitude and local times of 14-16h. The mean zonal winds in the uv cloud accelerated in the course of the 2006-2012 period 15 ms-1. The near infrared and visible images show a more constant circulation without time variability or longitudinal variations. The meridional circulation is absent in near infrared and visible images indicating thatthe Hadley-cell circulation in Venus atmosphere is shallow or the returning branch of the meridional circulation extends to levels below levels sensed in near infrared images. At the clod tops observed in UV images there are signatures of a long-term acceleration of the zonal winds when comparing winds from 2006-2008 to 2009-2012 with a mean acceleration of 17 ms-1 between both time periods

Solar oscillations can be modeled by Galbrun's equation which describes Lagrangian wave displacement in a self-gravitating stratified medium. For spherically symmetric backgrounds, we construct an algorithm to compute efficiently and accurately the coefficients of the Green's tensor of the time-harmonic equation in vector spherical harmonic basis. With only two resolutions, our algorithm provides values of the kernels for all heights of source and receiver, and prescribes analytically the singularities of the kernels. We also derive absorbing boundary conditions (ABC) to model wave propagation in the atmosphere above the cut-off frequency. The construction of ABC, which contains varying gravity terms, is rendered difficult by the complex behavior of the solar potential in low atmosphere and for frequencies below the Lamb frequency. We carry out extensive numerical investigations to compare and evaluate the efficiency of the ABCs in capturing outgoing solutions. Finally, as an application towards helioseismology, we compute synthetic solar power spectra that contain pressure modes as well as internal-gravity (g-) and surface-gravity (f-) ridges which are missing in simpler approximations of the wave equation. For purpose of validation, the location of the ridges in the synthetic power spectra are compared with observed solar modes.

We have analyzed the total intensity, spectral index, linear polarization, and RM distributions at pc scale for the quasar 1604+159. The source was observed in 2002 and 2020 with the VLBA. Combining the MOJAVE results, we studied the evolution of the magnetic field. We detected a core-jet structure. The jet extends to a distance of ~25 mas. The jet shape varies slightly with time. We divided the source structure into the central region and the jet region. In the jet region, we find the polarized emission varies with time. The flatter spectral index values and EVPA direction indicate the possible existence of shocks, contributing to the variation. In the central region, the derived core shift index k_r values indicate that the core in 2002 is close to the equipartition case while deviating from it in 2020. The measured magnetic field strength in 2020 is two orders of magnitude lower than that in 2002. We detected transverse RM gradients, evidence of a helical magnetic field, in the core. At 15 GHz, in the place close to the jet base, the polarization direction changes significantly with time from perpendicular to parallel to the jet direction. The evolution of RM and magnetic field structure are potential reasons for the observed polarization change. The core |RM| in 2020 increases with frequency following a power law with index a = 2.7, suggesting a fast electron density fall-off in the medium with distance from the jet base.

Previous studies of the protoplanetary disk HD 163296 revealed that the morphology of its sub-au infrared emission encompasses the terminal sublimation front of dust grains, referred to as the inner rim, but also extends into the (supposedly) dust-free region within it. Here, we present a set of radiative hydrostatic simulations of the inner rim in order to assess how much the rim alone can contribute to the observed interferometric visibilities $V$, half-light radii $R_{\mathrm{hl}}$, and fractional disk fluxes $\mathcal{F}$ in the wavelength range $1.5$--$13\,\mu\mathrm{m}$. In our set of models, we regulate the cooling efficiency of the disk via the boundary condition for radiation diffusion and we also modify the shape of the sublimation front. We find that when the cooling efficiency is reduced, the infrared photosphere at the rim becomes hotter, leading to an increase of $R_{\mathrm{hl}}$ sufficient to match the observations. However, the near-infrared disk flux is typically too low ($\mathcal{F}\simeq0.25$ at $1.5\,\mu\mathrm{m}$), resulting in H-band visibility curves located above the observed data. We show that the match to the H-band observations up to moderate baselines can be improved when a wall-shaped rather than curved sublimation front is considered. Nevertheless, our model visibilities always exhibit a bounce at long baselines, which is not observed, confirming the need for additional emission interior to the rim. In summary, our study illustrates how the temperature structure and geometry of the inner rim needs to change in order to boost the rim's infrared emission.

We investigate the fate of a collapsing stellar core, which is the final state of evolution of a massive, rotating star of a Wolf-Rayet type. Such stars explode as type I b/c supernovae, which have been observed in association with long gamma ray bursts (GRBs). The core of the star is potentially forming a black hole, which is embedded in a dense, rotating, and possibly highly magnetized envelope. We study the process of collapse using General Relativistic MHD simulations, and we account for the growth of the black hole mass and its spin, as well as related evolution of the spacetime metric. We find that some particular configurations of the initial black hole spin, the content of angular momentum in the stellar core, and the magnetic field configuration and its strength, are favored for producing a bright electromagnetic transient (i.e., a gamma ray burst). On the other hand, most of the typical configurations studied in our models do not lead to a transient electromagnetic explosion and will end up in a direct collapse, accompanied by some residual variability induced by changing accretion rate. We also study the role of self-gravity in the stellar core and quantify the relative strength of the interfacial instabilities, such as Self-Gravity Interfacial (SGI) instability and Rayleigh-Taylor (RT), which may account for the production of an inhomogeneous structure, including spikes and bubbles, through the inner radii of the collapsing core (inside $\sim 200~r_{g}$). %Furthermore, we investigate the axisymmetric modes of gravitational instability based on the generalized Toomre parameter. We find that in self-gravitating collapsars the RT modes cannot grow efficiently. We also conclude that transonic shocks are formed in the collapsing envelope, but they are weaker in magnetized stars.

Star formation is essential in galaxy evolution and the cycling of matter. The support of interstellar clouds against gravitational collapse by magnetic (B-) fields has been proposed to explain the low observed star formation efficiency in galaxies and the Milky Way. Despite the Planck satellite providing a 5-15' all-sky map of the B-field geometry in the diffuse interstellar medium, higher spatial resolution observations are required to understand the transition from diffuse gas to gravitationally unstable filaments. NGC 2024, the Flame Nebula, in the nearby Orion B molecular cloud, contains a young, expanding HII region and a dense filament that harbors embedded protostellar objects. Therefore, NGC 2024 is an excellent opportunity to study the role of B-fields in the formation, evolution, and collapse of filaments, as well as the dynamics and effects of young HII regions on the surrounding molecular gas. We combine new 154 and 216 micron dust polarization measurements carried out using the HAWC+ instrument aboard SOFIA with molecular line observations of 12CN(1-0) and HCO+(1-0) from the IRAM 30-meter telescope to determine the B-field geometry and to estimate the plane of the sky magnetic field strength across the NGC 2024. The HAWC+ observations show an ordered B-field geometry in NGC 2024 that follows the morphology of the expanding HII region and the direction of the main filament. The derived plane of the sky B-field strength is moderate, ranging from 30 to 80 micro G. The strongest B-field is found at the northern-west edge of the HII region, characterized by the highest gas densities and molecular line widths. In contrast, the weakest field is found toward the filament in NGC 2024. The B-field has a non-negligible influence on the gas stability at the edges of the expanding HII shell (gas impacted by the stellar feedback) and the filament (site of the current star formation).

W43-main is a massive molecular complex located at the interaction of the Scutum arm and the Galactic bar undergoing starburst activities. We aim to investigate the gas dynamics, in particular, the prevailing shock signatures from the cloud to clump scale and assess the impact of shocks on the formation of dense gas and early-stage cores. We have carried out NOEMA and IRAM-30m observations at 3 mm with an angular resolution of $\sim$0.1 pc towards five massive clumps in W43 main. We use CH$_{3}$CCH and H$_{2}$CS lines to trace the extended gas temperature and CH$_{3}$OH lines to probe the volume density of the dense gas ($\gtrsim$10$^{5}$ cm$^{-3}$). The emission of SiO (2-1) is extensive across the region ($\sim$4 pc) and is mostly contained within a low-velocity regime, hinting at a large-scale origin of the shocks. The position-velocity maps of multiple tracers show systematic spatio-kinematic offsets supporting the cloud-cloud collision/merging scenario. We identify an additional extended velocity component in CCH emission, which coincides with one of the velocity components of the larger scale $^{13}$CO (2-1) emission, likely representing an outer, less dense gas layer in the cloud merging process. We find that the V-shaped, asymmetric SiO wings are tightly correlated with localised gas density enhancements, which is direct evidence of dense gas formation and accumulation in shocks. We resolve two categories of NH$_{2}$D cores: ones exhibiting only subsonic to transonic velocity dispersion, and the others with an additional supersonic velocity dispersion. The centroid velocities of the latter cores are correlated with the shock front seen by SiO. The kinematics of the $\sim$0.1 pc NH$_{2}$D cores are heavily imprinted by shock activities, and may represent a population of early-stage cores forming around the shock interface.

We propose an extended formalism for the spectral broadening function (BF) based on the multiplication rule of block matrices. The formalism, which we named the binary broadening function (BBF), can produce decomposed BFs for individual components of a binary star system by using two spectral templates. The decomposed BFs can be used to derive precise rotational profiles and radial velocities for individual components. We test the BBF on simulated spectra and actual observational spectra to show that the method is feasible on spectroscopic binaries, even when the spectral lines of two stellar components are heavily blended. To demonstrate the capability of the method, we conduct a simulation of `sketching' (imaging) a transiting circumbinary exoplanet using the BBF. We also discuss issues of implementation such as the variation of BBF with biased templates, the pros and cons of BBF, and cases when the method is not applicable.

We analyzed spectral cubes of Callisto's leading and trailing hemispheres, collected with the NIRSpec Integrated Field Unit (G395H) on the James Webb Space Telescope. These spatially resolved data show strong 4.25-micron absorption bands resulting from solid-state 12CO2, with the strongest spectral features at low latitudes near the center of its trailing hemisphere, consistent with radiolytic production spurred by magnetospheric plasma interacting with native H2O mixed with carbonaceous compounds. We detected CO2 rovibrational emission lines between 4.2 and 4.3 microns over both hemispheres, confirming the global presence of CO2 gas in Callisto's tenuous atmosphere. These results represent the first detection of CO2 gas over Callisto's trailing side. The distribution of CO2 gas is offset from the subsolar region on either hemisphere, suggesting that sputtering, radiolysis, and geologic processes help sustain Callisto's atmosphere. We detected a 4.38-micron absorption band that likely results from solid-state 13CO2. A prominent 4.57-micron absorption band that might result from CN-bearing organics is present and significantly stronger on Callisto's leading hemisphere, unlike 12CO2, suggesting these two spectral features are spatially anti-associated. The distribution of the 4.57-micron band is more consistent with a native origin and/or accumulation of dust from Jupiter's irregular satellites. Other, more subtle absorption features could result from CH-bearing organics, CO, carbonyl sulfide (OCS), and Na-bearing minerals. These results highlight the need for preparatory laboratory work and improved surface-atmosphere interaction models to better understand carbon chemistry on the icy Galilean moons before the arrival of NASA's Europa Clipper and ESA's JUICE spacecraft.

Since the discovery of synchrotron X-ray emission from the shell of the supernova remnant (SNR) SN 1006, multiple observations from Chandra and XMM-Newton have shown that many young SNRs produce synchrotron emission in X-rays. Among those, a few peculiar SNRs have their X-ray emission largely dominated by synchrotron radiation, showing no or only faint traces of thermal emission. In this paper, we report our mapping of the thermal emission in three emblematic synchrotron-dominated SNRs: G330.2+1.0, 3C58, and RX J1713.7-3946. We used a blind source separation method able to retrieve faint components from X-ray data in the form of Chandra and XMM-Newton observations. The thermal candidates disentangled by the algorithm were then used to select regions of extraction. We then analyzed the extracted spectra to assess their physical nature. We conclude that the components retrieved by the algorithm indeed represent the spatial distribution of the thermal emission in G330.2+1.0 and 3C58, and a likely thermal candidate in RX J1713.7-3946. Our findings confirm and expand on past studies.

Fast radio bursts (FRBs) are short-duration radio pulses of cosmological origin. Among the most common sources predicted to explain this phenomenon are bright pulses from a class of extremely highly magnetized neutron stars known as magnetars. Motivated by the discovery of an FRB-like pulse from the Galactic magnetar SGR 1935+2154, we searched for similar events in Messier 82 (M82). With a star formation rate 40 times that of the Milky Way, one might expect that the implied rate of events similar to that seen from SGR 1935+2154 from M82 should be 40 times higher than that of the Milky Way. We observed M82 at 1.4 GHz with the 20-m telescope at the Green Bank Observatory for 34.8 days. While we found many candidate events, none had a signal-to-noise ratio greater than 8. We also show that there are insufficient numbers of repeating low-significance events at similar dispersion measures to constitute a statistically significant detection. From these results, we place an upper bound for the rate of radio pulses from M82 to be 30 per year above a fluence limit of 8.5 Jy ms. While this is less than 9 times the rate of radio bursts from magnetars in the Milky Way inferred from the previous radio detections of SGR 1935+2154, it is possible that propagation effects from interstellar scattering are currently limiting our ability to detect sources in M82. Further searches of M82 and other nearby galaxies are encouraged to probe this putative FRB population.

The Simeis~147 nebula (S147), particularly well known for a spectacular net of ${\rm H}_\alpha$-emitting filaments, is often considered one of the largest and oldest known supernova remnants in the Milky Way. Here, and in a companion paper, we present studies of X-ray emission from the S147 nebula using the data of SRG/eROSITA All-Sky Survey observations. In this paper, we argue that many inferred properties of the X-ray emitting gas are broadly consistent with a scenario of the supernova explosion in a low-density cavity, e.g. a wind-blown-bubble. This scenario assumes that a $\sim 20\,{\rm M_\odot}$ progenitor star has had small velocity with respect to the ambient ISM, so it stayed close to the center of a dense shell created during its Main Sequence evolution till the moment of the core-collapse explosion. The ejecta first propagate through the low-density cavity until they collide with the dense shell, and only then the reverse shock goes deeper into the ejecta and powers the observed X-ray emission of the nebula. The part of the remnant inside the dense shell remains non-radiative till now and, plausibly, in a state with $T_e<T_i$ and Non-Equilibrium Ionization (NEI). On the contrary, the forward shock becomes radiative immediately after entering the dense shell, and, being subject to instabilities, creates a characteristic "foamy" appearance of the nebula in ${\rm H}_\alpha$ and radio emission.

We investigate production of non-thermal dark matter particle and heavy sterile neutrino from inflaton during the reheating era which is preceded by a slow-roll inflationary epoch with a quartic potential and non-minimal coupling ($\xi$) between the inflaton and the gravity. We compare our analysis between metric and Palatini formalism. For the latter with $\xi=0.5$ and number of $e$-folds $\sim 60$, $r$ can be as small as $\sim {\cal O}\left(10^{-3}\right)$ which may be validated at $1-\sigma$ CL of prospective future reaches of upcoming CMB observation such as CMB-S4~etc. We identify that permissible range of Yukawa coupling $y_\chi$ between inflaton and fermionic DM $\chi$, to be ${\cal O}\left(10^{-3.5}\right)\gtrsim y_\chi \gtrsim {\cal O}\left(10^{-20}\right)$ for metric formalism and ${\cal O}\left(10^{-4}\right)\gtrsim y_\chi \gtrsim {\cal O}\left(10^{-11}\right)$ for Palatini formalism which is consistent with current PLANCK data and also be within the reach of future CMB experiments. For the scenario of leptogenesis via the decay of sterile neutrino produced from inflaton decay, we also investigate the parameter space of heavy neutrino mass $m_{N_1}$ and Yukawa coupling $y_{N_1}$ of sterile neutrino with inflaton, which are consistent with current CMB data and successful generation of the observed baryon asymmetry of the universe via leptogenesis. In contrast to metric formalism, in the case of Palatini formalism for successful leptogenesis to occur we find that $y_{N_1}$ has a very narrow allowable range and is severely constrained from the consistency with CMB predictions.

Planetary systems with close-in giant planets can experience magnetic star-planet interactions that modify the activity levels of their host stars. The induced activity is known to strongly depend on the magnetic moment of the interacting planet. Therefore, such planet-induced activity should be more readily observable in systems with planets in eccentric orbits, since those planets are expected to rotate faster than in circular orbits. However, no evidence of magnetic interactions has been reported in eccentric systems to date. We intend to unveil a possible planet-induced activity in the bright ($V$ = 8.05 $\pm$ 0.03 mag) and slightly evolved star HD 118203, which hosts an eccentric ($e$ = 0.32 $\pm$ 0.02) and close-in ($a$ = 0.0864 $\pm$ 0.0006 au) Jupiter-sized planet. We characterized the system by modelling 56 ELODIE radial velocities and four sectors of TESS photometry. We searched for planet-induced and rotation-related activity signals within the TESS, ELODIE, and ASAS-SN public data. We studied the possible origins of the variability found, analysed its persistence and evolution, and searched for links with the eccentric orbital motion of HD 118203 b. We found evidence of an activity signal within the TESS data that matches the orbital period of HD 118203 b, which suggests the existence of magnetic star-planet interactions. We did not find, however, any additional signal that could be interpreted as the rotation of the star, so we cannot discard stellar rotation as the source of the signal found. Nevertheless, the evolved nature of the star and the orbital eccentricity make the synchronous stellar rotation very unlikely. HD 118203 represents the best evidence that magnetic star-planet interactions can be found in eccentric systems, and it opens the door to future dedicated searches that will allow us to better understand the interplay between close-in planets and their hosts.

We present the results of the first X-ray all-sky survey (eRASS1) performed by the eROSITA instrument onboard the Spectrum-Roentgen-Gamma (SRG) mission on X-ray emitting red giants and supergiants. Focussing on stars positioned at high galactic latitudes above 20 deg, we construct a complete sample of such objects using the Gaia DR3 catalog and identify a sample 96 stars appearing as bona fide entries in the eRASS1 source catalog. Restricting again the sample to objects nearer than 1300~pc and eliminating all catalog entries which are due to optical contamination, we end up with a sample of 16 genuine red giant/supergiant X-ray sources, which represent -- with the exception of one source (CL~Hyi) -- new X-ray detections. We furthermore present a low SNR X-ray spectrum of the nearby low activity giant Arcturus obtained from a pointed observation with the XMM-Newton satellite and give a detailed account of our data analysis. We show that Arcturus-like X-ray emission cannot be the explanation for the X-ray emissions observed by eROSITA and provide a discussion of the possible nature of the detected X-ray sources.

The eROSITA telescope array aboard the Spektrum Roentgen Gamma (SRG) satellite began surveying the sky in December 2019, with the aim of producing all-sky X-ray source lists and sky maps of an unprecedented depth. Here we present catalogues of both point-like and extended sources using the data acquired in the first six months of survey operations (eRASS1; completed June 2020) over the half sky whose proprietary data rights lie with the German eROSITA Consortium. We describe the observation process, the data analysis pipelines, and the characteristics of the X-ray sources. With nearly 930000 entries detected in the most sensitive 0.2-2.3 keV energy range, the eRASS1 main catalogue presented here increases the number of known X-ray sources in the published literature by more than 60%, and provides a comprehensive inventory of all classes of X-ray celestial objects, covering a wide range of physical processes. A smaller catalogue of 5466 sources detected in the less sensitive but harder 2.3-5 keV band is the result of the first true imaging survey of the entire sky above 2 keV. We show that the number counts of X-ray sources in eRASS1 are consistent with those derived over narrower fields by past X-ray surveys of a similar depth, and we explore the number counts variation as a function of the location in the sky. Adopting a uniform all-sky flux limit (at 50% completeness) of F_{0.5-2 keV} > 5 \times 10^{-14}$ erg\,s$^{-1}$\,cm$^{-2}$, we estimate that the eROSITA all-sky survey resolves into individual sources about 20% of the cosmic X-ray background in the 1-2 keV range. The catalogues presented here form part of the first data release (DR1) of the SRG/eROSITA all-sky survey. Beyond the X-ray catalogues, DR1 contains all detected and calibrated event files, source products (light curves and spectra), and all-sky maps. Illustrative examples of these are provided.

X-ray quasi-periodic eruptions (QPEs) are a novel addition to the group of extragalactic transients. In this work, we report the discovery of two further galaxies showing QPEs, eRO-QPE3 and eRO-QPE4, with the eROSITA X-ray telescope on board the Spectrum Roentgen Gamma observatory. Among the properties in common with those of known QPEs are: the thermal-like spectral shape in eruption (up to $kT\sim110-120$ eV) and quiescence ($kT\sim50-90$ eV) and its evolution during the eruptions (with a harder rise than decay); the lack of strong canonical signatures of active nuclei (from current optical, UV, infrared and radio data); and the low-mass nature of the host galaxies ($\log M_*\approx 9-10$) and their massive central black holes ($\log M_{\rm BH}\approx 5-7$). These discoveries also bring several new insights into the QPE population: i) eRO-QPE3 shows eruptions on top of a decaying quiescence flux, providing further evidence for a connection between QPEs and a preceding tidal disruption event; ii) eRO-QPE3 exhibits the longest recurrence times and faintest peak luminosity of QPEs, compared to the known QPE population, excluding a correlation between the two; iii) we find evidence, for the first time, of a transient component that is harder, albeit much fainter, than the thermal QPE spectrum in eRO-QPE4; and iv) eRO-QPE4 displays the appearance (or significant brightening) of the quiescence disk component after the detection of QPEs, supporting its short-lived nature against a preexisting active galactic nucleus. Overall, the newly discovered properties (e.g., recent origin and/or transient nature of the quiescent accretion disk; lack of correlation between eruption recurrence timescales and luminosity) are qualitatively consistent with recent models that identify QPEs as extreme mass-ratio inspirals.

We investigate the impact of AGN feedback, on the entropy and characteristic temperature measurements of galaxy groups detected in the SRG/eROSITA's first All-Sky Survey (eRASS1) to shed light on the characteristics of the feedback mechanisms. We analyze deeper eROSITA observations of 1178 galaxy groups detected in eRASS1. We divide the sample into 271 subsamples and extract average thermodynamic properties, including electron density, temperature, and entropy at three characteristic radii along with the integrated temperature by jointly analyzing X-ray images and spectra following a Bayesian approach. We present the tightest constraints on the impact of AGN feedback through our average entropy and characteristic temperature measurements of the largest group sample used in X-ray studies, incorporating major systematics in our analysis. We find that entropy shows an increasing trend with temperature in the form of a power-law-like relation at the higher intra-group medium temperatures, while for the low mass groups, a slight flattening is observed on the average entropy. Overall, the observed entropy measurements agree well with the earlier measurements in the literature. The comparisons with the state-of-the-art cosmological hydrodynamic simulations (MillenniumTNG, Magneticum, OWL simulations) after the applications of the selection function calibrated for our galaxy groups reveal that observed entropy profiles in the cores are below the predictions of simulations. At the mid-region, the entropy measurements agree well with the Magneticum simulations, whereas the predictions of MillenniumTNG and OWL simulations fall below observations. At the outskirts, the overall agreement between the observations and simulations improves, with Magneticum simulations reproducing the observations the best. Our measurements will pave the way for more realistic AGN feedback implementations in simulations.

Major mergers between galaxies are predicted to fuel their central supermassive black holes (SMBHs), particularly after coalescence. However, determining the prevalence of active galactic nuclei (AGNs) in mergers remains a challenge, because AGN diagnostics are sensitive to details of the central structure (e.g., nuclear gas clouds, geometry and orientation of a dusty torus) that are partly decoupled from SMBH accretion. X-rays, expected to be ubiquitous among accreting systems, are detectable through non-Compton-thick screens of obscuring material, and thus offer the potential for a more complete assessment of AGNs in mergers. But, extant statistical X-ray studies of AGNs in mergers have been limited by either sparse, heterogeneous, or shallow on-sky coverage. We use new X-ray observations from the first SRG/eROSITA all-sky data release to characterize the incidence, luminosity, and observability of AGNs in mergers. Combining machine learning and visual classification, we identify 923 post-mergers in Dark Energy Camera Legacy Survey (DECaLS) imaging and select 4,565 interacting galaxy pairs (with separations <120 kpc and mass ratios within 1:10) from the Sloan Digital Sky Survey. We find that galaxies with X-ray AGNs are 2.0+/-0.24 times as likely to be identified as post-mergers compared to non-AGN controls, and that post-mergers are 1.8+/-0.1 times as likely to host an X-ray AGN as non-interacting controls. A multi-wavelength census of X-ray, optical, and mid-IR-selected AGNs suggests a picture wherein the underlying AGN fraction increases during pair-phase interactions, that galaxy pairs within ~20 kpc become heavily obscured, and that the obscuration often clears post-coalescence.

Aims: During its all-sky survey phase, the eROSITA X-ray telescope onboard SRG scans through the ecliptic poles every 4 hours. This extensive data set of long-duration, frequent, and consistent observations of thousands of X-ray sources is ideal for a detailed long-term X-ray variability analysis. However, individual observations are short, are separated by long but consistent gaps, and have varying exposure times. Therefore, the identification of variable sources, and the characterisation and quantification of their variability requires a unique methodology. We aim to develop and evaluate such methods for eROSITA observations, focusing on sources close to the survey poles. Methods: We simulate eROSITA-like light curves to evaluate and quantify the effect of survey mode observations on the measured periodogram and normalised excess variance. We introduce a new method for estimating the normalised intrinsic variance of a source based on the Bayesian excess variance (bexvar) method. Results: We determine thresholds for identifying likely variable sources while minimising the false-positive rate, as a function of the number of bins, and the average count rate in the light curve. The bexvar normalised intrinsic variance estimate is significantly more accurate than the normalised excess variance method in the Poisson regime. At high count rates, the two methods are comparable. We quantify the scatter in the intrinsic variance of a stationary pink noise process, and investigate how to reduce it. Finally, we determine a description of the excess noise in a periodogram caused by varying exposure times throughout a light curve. Although most of these methods were developed specifically for analysing variable AGN in the eROSITA all-sky survey, they can also be used for the variability analysis of other datasets from other telescopes, with slight modifications.

Aims: During the Spectrum Roentgen Gamma (SRG)/ eROSITA all-sky surveys, X-ray sources close to the South Ecliptic Pole (SEP) are observed almost every 4 hours. We aim to identify the sources exhibiting the most significant long-term X-ray variability within 3 degrees of the SEP in the first three surveys, and investigate their properties. Methods: We determined the variability significance of all sources observed by eROSITA within 3 degrees of the SEP by using thresholds on the Bayesian excess variance (SCATT_LO) and the maximum amplitude deviation (AMPL_SIG). Sources exhibiting a variability significance above $3\sigma$ were subdivided into likely Galactic and extragalactic sources, by using spectral and photometric information of their optical counterparts. We quantified the X-ray normalised excess variances of all variable sources, and also calculated the periodograms of the brightest ones. Results: Out of more than $10^4$ X-ray sources detected by eROSITA within 3 degrees of the SEP, we identified 453 that exhibit significant X-ray variability. SCATT_LO is significantly more sensitive to detecting variable sources in this field, but AMPL_SIG helps provide a more complete variability sample. Of those variable sources, 168 were classified as likely extragalactic, and 235 as likely Galactic. The periodograms of most bright and variable extragalactic sources are approximately described by an aliased power law ($P\propto\nu^{-\alpha}$) with an index of $\alpha\approx 1$. We identified a potential tidal disruption event, and long-term transient sources. The stellar X-ray variability was predominantly caused by bright X-ray flares from coronally active stars.

The extended ROentgen Survey with an Imaging Telescope Array (eROSITA) on board the Spectrum-Roentgen-Gamma (SRG) mission with its first All-Sky Survey (eRASS1) has offered an unprecedented, comprehensive view of the variable X-ray sky. With enhanced sensitivity, broader energy coverage, and improved resolution compared to prior surveys, the eRASS1 Data Release 1 (DR1) catalogue underwent a variability analysis, focusing on a substantial subset of 128,669 sources. We performed multiple variability tests, utilizing conventional normalized excess variance, maximum amplitude variability, and Bayesian excess variance methods. Among the 128,669 DR1 sources, our research identified 557 objects exhibiting variability through NEV and AMPLMAX tests. After applying suitable thresholds, 108 sources demonstrated significant variability via NEV, while 73 did so through AMPLMAX. The utilization of the bexvar method extended our detection capabilities to lower count rates, unveiling a total of 1307 sources manifesting variability. Furthermore, our comparative analysis spanning 2.5 years encompassed observations from consecutive eROSITA surveys, eRASS2, eRASS3, eRASS4, and eRASS5. Notably, the Gamma-ray burst afterglow GRB 200120A, which was the most variable DR1 source, was as expected absent in subsequent eROSITA survey scans. Observations of the Low-Mass X-ray Binary GX 339-4 across various eROSITA survey scans unveiled substantial variability. These outbursts involve the movement of the inner radius of the accretion disk, fluctuating inward and outward. Combining eROSITA and MAXI data reveals that the most effective tracer for monitoring the onset of the outbursts is the softest eROSITA band. Magnetically active stars are commonly found among the more variable X-ray sources. We analyzed the AGN sample to identify variability patterns and instances of efficiency limit violations.

The new Spectrum Roentgen Gamma (SRG)/eROSITA X-ray telescope has a superior response to extended soft X-rays in terms of effective area, energy resolution, and field-of-view (FoV). This makes SRG/eROSITA ideal for studying low X-ray surface brightness emission of cosmic filaments. We search for extended X-ray emission between the two nearby galaxy clusters Abell 3667 and Abell 3651 that are separated by a projected transverse distance of ${\sim} 13\,\mathrm{Mpc}$, using data from the SRG/eROSITA All-Sky Survey. Detailed X-ray image analysis of the region between the two galaxy clusters and redshift analysis of sources between them is performed. We carried out thorough surface brightness analysis between the clusters and in their outskirts studying enhanced emission in different directions. The analysis is complemented with an X-ray pointed observation from XMM-Newton, infrared 2MASS data and redshift information from NED. We discover an emission filament beyond the known radio relic in the northwest of A3667 and even beyond three times its virial radius, smoothly connecting to A3651. The X-ray emission in the direction of the filament shows a $30\pm3\,\%$ enhancement with a significance of $11\,\sigma$. The 2MASS map and redshift analysis show an alignment of sources along the filament and make a projection effect unlikely. Taking the redshift progression of sources within the filament into account, its three-dimensional length is estimated to be in the range of $25\,\mathrm{Mpc} - 32\,\mathrm{Mpc}$. Surface brightness analysis in combination with assumptions for ranges of plausible temperatures and metallicities leads to estimates of total flux, gas mass and central baryon overdensity of $F_\mathrm{X}= (7.1^{+2.1}_{-1.0})\times 10^{-12}\,\mathrm{erg s^{-1} cm^{-2}}$, $M_\mathrm{g}=(2.8^{+5.4}_{-1.0})\times 10^{14}\,\mathrm{M_\odot}$ and $\delta_0=220^{+390}_{-65}$, respectively.

The first eROSITA all-sky survey (eRASS1) performed on board the Spectrum-Roentgen-Gamma mission (SRG) provides more than 900,000 X-ray sources in the 0.2 - 2.3 keV band located in the western hemisphere. We present identifications of the eRASS1 sources obtained using our HamStar method, which was designed for the identification of coronal X-ray sources. HamStar is a Bayesian framework that estimates coronal probabilities for each eRASS1 source based on a cross-match with optical counterparts from Gaia DR3. It considers geometric properties, such as angular separation and positional uncertainty, as well the additional properties of fractional X-ray flux, color, and distance. We identify 138,800 coronal eRASS1 sources and estimate a completeness and reliability of about 91.5% for this sample, which we confirmed with Chandra detections. This is the largest available sample of coronal X-ray emitters and we find nearly five times as many coronal sources as in the ROSAT all-sky survey. The coronal eRASS1 sources are made up of all spectral types and the onset of convection and the saturation limit are clearly visible. As opposed to previous samples, rare source types are also well populated. About 10% of the coronal eRASS1 sources have a correlated secondary counterpart, which is a wide binary companion or belongs to the same stellar cluster. We also identify 6700 known unresolved binaries, and an excess of fast binary periods below 10 d. Furthermore, the binary sequence is clearly visible in a color-magnitude diagram. When combining the coronal eRASS1 sources with rotation modulations from Gaia DR3, we find 3700 X-ray sources with known rotation periods, which is the largest sample of this kind. We fitted the rotation-activity relation and convection turnover times for our flux-limited sample. We do not detect the low-amplitude fast rotators discovered in the Gaia DR3 sample in X-rays.

Most baryonic matter resides in the intergalactic medium (IGM), a diffuse gas primarily composed of ionized hydrogen and helium, filling the space between galaxies. Observations of such an environment are crucial to better understanding the physical processes involved in such an environment. We present an analysis of the IGM absorption using blazar spectra from the first eROSITA all-sky survey (eRASS1) performed onboard of the Spectrum-Roentgen-Gamma mission (SRG) and {\it XMM-Newton} X-ray observations. First, we fitted the continuum spectra using a log-parabolic spectrum model and fixed the Galactic absorption. Then, we included a collisional ionization equilibrium model, namely {\tt IONeq}, to account for the IGM absorption. The column density $N({\rm H})$ and metallicity ($Z$) were set as free parameters. At the same time, the redshift of the absorber was fixed to half the blazar redshift as an approximation of the full line-of-sight absorber. We measured IGM-$N({\rm H})$ for 147 sources for SRG and 10 sources for {\it XMM-Newton}. We found a clear trend between IGM-$N({\rm H})$ and the blazar redshifts which scales as $(1+z)^{1.63\pm 0.12}$. The mean hydrogen density at $z=0$ is $n_{0}=(2.75\pm 0.63)\times 10^{-7}$ cm$^{-3}$. The mean temperature over the redshift range is $\log(T/K)=5.6\pm 0.6$ while the mean metallicity is $Z=0.16\pm 0.09$. We found no acceptable fit using a power-law model for either temperatures or metallicities as a function of the redshift. These results indicate that the IGM contributes substantially to the total absorption seen in the blazar spectra.

We present a detailed study of the hydrogen density distribution in the local interstellar medium (ISM) using the X-ray absorption technique. Hydrogen column densities were precisely measured by fitting X-ray spectra from coronal sources observed during the initial {\it eROSITA} all-sky survey (eRASS1). Accurate distance measurements were obtained through cross-matching Galactic sources with the {\it Gaia} third data release (DR3). Despite the absence of a discernible correlation between column densities and distances or Galactic longitude, a robust correlation with Galactic latitude was identified. This suggests a decrease in ISM material density along the vertical direction away from the Galactic plane. To further investigate, we employed multiple density laws to fit the measured column densities, revealing constraints on height scale values ($8 < h_{z} < 30$~pc). Unfortunately, radial scales and central density remain unconstrained due to the scarcity of sources near the Galactic center. Subsequently, a 3D density map of the ISM was computed using a Gaussian processing approach, inferring hydrogen density distribution from hydrogen column densities. The results unveiled the presence of multiple beams and clouds of various sizes, indicative of small-scale structures. Large density regions were identified at approximately 100~pc, consistent with findings in dust reddening studies, potentially associated with the Galactic Perseus arm. Moreover, high-density regions were pinpointed in proximity to the Orion star-forming region and the Chamaeleon molecular complex, enriching our understanding of the intricate structure of the local interstellar medium.

Although flux variability is one of the defining properties of accretion flows onto supermassive black holes, its dependence on physical parameters such as the mass of the compact object and the Eddington ratio remain under discussion. In this paper we address this issue using the structure function statistic to measure the variability at X-ray wavelengths of a sample of optically selected QSOs with available black hole masses and Eddington ratios. We present a new Bayesian methodology for estimating the structure function tailored to the Poisson nature of the X-ray data. This is applied to 15,548 SDSS DRQ16 QSOs with repeat observations in the XMM-Newton archive and/or the SRG/eROSITA All Sky Survey. The X-ray structure function monotonically increases to time intervals of about 10-15 years, suggesting a preference for scenarios in which instabilities of the accretion disk contribute to the X-ray variability on long timescales. Additionally, there is evidence that the amplitude of the stochastic X-ray flux variations rises with decreasing black hole mass and Eddington ratio. This finding imposes stringent constraints on empirical models of Active Galactic Nuclei variability derived from local samples, emphasizing the significance of high-redshift population studies for comprehending the stochastic flux variations in active black holes.

We present an extensive radio monitoring campaign of the nuclear transient eRASSt J234403-352640 with the Australia Telescope Compact Array, one of the most X-ray luminous TDE candidates discovered by the SRG/eROSITA all-sky survey. The observations reveal a radio flare lasting more than 1000 d, coincident with the X-ray, UV, optical, and infra-red flare of this transient event. Through modelling of the 10 epochs of radio spectral observations obtained, we find that the radio emission is well-described by an expanding synchrotron emitting region, consisting of a single ejection of material launched coincident with the optical flare. We conclude that the radio flare properties of eRASSt J234403-352640 are consistent with the population of radio-emitting outflows launched by non-relativistic tidal disruption events, and that the flare is likely due to an outflow launched by a tidal disruption event (but could also be a due to a new AGN accretion event) in a previously turned-off AGN.

We study variability through simultaneous optical and X-ray observations for the first time in a statistical sample of 256 M dwarfs. Such observations are required to constrain the flare frequency and energetics and to understand the physics of flares. Using light curves from extended ROentgen Survey with an Imaging Telescope Array (eROSITA) on board the Russian Spektrum-Roentgen-Gamma mission (SRG) and the Transiting Exoplanet Survey Satellite (TESS), we identify 256 M dwarfs with simultaneous detections. The 25 brightest or most variable in X-rays are selected. Stellar parameters are obtained from Gaia and 2MASS, while X-ray fluxes are derived from eROSITA count rates. Proximity (<100 pc), fast rotation (P_rot < 9 d), and high flare frequency characterize our sample. Optical and X-ray duty cycles correlate positively, with faster rotators exhibiting more variability. Stars with frequent X-ray flares often coincide with optical flares. Analyzing individual X-ray flares is hindered by eROSITA's low cadence, mitigated by leveraging TESS optical flares and solar flare knowledge. An exponential fit to 21 X-ray light curves post-optical flares reveals a correlation between X-ray and optical flare energies. Despite uncertainties due to poor eROSITA sampling, our study underscores the significance of simultaneous all-sky surveys in diverse wavelengths for unprecedented insights into stellar variability.

Massive black holes (MBHs) are typically hosted in the centres of massive galaxies but they appear to become rarer in lower mass galaxies, where nuclear star clusters (NSCs) frequently appear instead. The transition region, where both an MBH and NSC can co-exist, has been poorly studied to date and only a few dozen galaxies are known to host them. One avenue for detecting new galaxies with both an MBH and NSC is to look for accretion signatures of MBHs. Here, we use new SRG/eROSITA all-sky survey eRASS:4 data to search for X-ray signatures of accreting MBHs in NSCs, while also investigating their combined occupation fraction. We find significant detections for 18 galaxies (~8.3%), including one ultra-luminous X-ray source; however, only three galaxies (NGC2903, 4212, and 4639) have X-ray luminosities that are higher than the expected value from X-ray binaries, indicative of the presence of an MBH. In addition, the X-ray luminosity of six galaxies (NGC2903, 3384, 4321, 4365, 4639, and 4701) differs from previous studies and could indicate the presence of a variable active galactic nucleus. The combined occupation fraction of accreting MBHs and NSCs becomes non-zero for galaxy masses above ~10^7.5 M_sun and this result is slightly elevated as compared to the literature data. Our data extend, for the first time, towards the dwarf elliptical galaxy regime and identify promising MBH candidates for higher resolution follow-up observations. At most galaxy masses (and with the exception of three cases), the X-ray constraints are consistent with the expected emission from binary systems or an Eddington fraction of at most 0.01%, assuming a black holes mass of 10^6.5 M_sun. This work confirms the known complexities in similar-type of studies, while providing the appealing alternative of using X-ray survey data of in-depth observations of individual targets with higher resolution instruments.

The Gemini-Monoceros X-ray enhancement is a rich field for studying diffuse X-ray emission and supernova remnants (SNRs). With the launch of eROSITA onboard the SRG platform in 2019, we are now able to fully study these sources. Many of the SNRs in the vicinity are suspected to be very old remnants, which are severely understudied in X-rays due to numerous observational challenges. In addition, identification of new faint large SNRs might help to solve the long-standing discrepancy of observed and expected number of Galactic SNRs. We performed a detailed X-ray spectral analysis of the entire diffuse structure and a detailed background analysis of the vicinity. We also made use of multi-wavelength data to better understand the morphology and to constrain the distances to the different sources. We estimated the plasma properties of the sources and calculated a grid of model SNRs to determine the individual SNR properties. Most of the diffuse plasma of the Monogem Ring SNR is well described by a single non-equilibrium ionization (NEI) component with an average temperature of $kT = 0.14\pm 0.03$ keV. We obtain an age of $\approx 1.2\cdot 10^5$ yr - consistent with PSR B0656+14 - for the Monogem Ring. In the south-east, we found evidence for a hotter second plasma component and a possible new SNR candidate at $\approx 300$ pc, with the new candidate having an age of $\approx 50,000$ yr. We were also able to improve on previous studies on the more distant Monoceros Loop and PKS 0646+06 SNRs. We obtained significantly higher temperatures than previous studies, and for PKS 0646+06 a much lower estimated age of the SNR. We also found a new SNR candidate G190.4+12.5 which most likely is located at $D > 1.5 $ kpc, expanding into a low density medium at a high distance from the Galactic plane, with an estimated age of $40,000-60,000$ yr.

The X-ray source eRASSU J131716.9-402647 was recently identified from observations with Spectrum Roentgen Gamma (SRG)/eROSITA as a promising X-ray dim isolated neutron star (XDINS) candidate on the premise of a soft energy distribution, absence of catalogued counterparts, and a high X-ray-to-optical flux ratio. Here, we report the results of a multi-wavelength observational campaign with XMM-Newton, NICER and the FORS2 instrument at the ESO-VLT. We found in both the XMM-Newton and NICER data that the X-ray emission is strongly pulsed at a period of $12.757$ s (pulsed fraction $p_\mathrm{f} = (29.1 \pm 2.6)$% in the 0.2-2 keV band). The pulse profile is double-humped, and the pulsed fraction increases with energy. The XMM-Newton and NICER epochs allow us to derive a 3$\sigma$ upper limit of $\dot{P}\leq 8\times 10^{-11}$ s s$^{-1}$ on the spin-down rate of the neutron star. The source spectrum is well described by a purely thermal continuum, either a blackbody with $kT\sim95$ eV or a magnetised neutron star atmosphere model with $kT \sim 35$ eV. Similarly to other thermally emitting isolated neutron stars, we found in either case strong deviations from the continuum, a broad absorption feature at energy $\sim260$ eV and a narrow one around $590$ eV. The FORS2 instrument at ESO-VLT has not detected the optical counterpart ($m_\mathrm{R}>27.5$ mag, $5\sigma$ detection limit), implying an X-ray-to-optical flux ratio of $10^4$ at least. The properties of eRASSU J131716.9-402647 strongly resemble those of a highly magnetised isolated neutron star and favour an XDINS or high-B pulsar nature.

A dozen of patches of polarized radio emission spanning tens of degrees in the form of coherent and stationary loops are observed at radio frequencies across the sky. Their origin is usually associated to nearby shocks, possibly arising from close supernovae explosions. The origin of the radio Loop XII remains so far unknown. We report an anti-correlation of the radio polarized emission of loop XII with a large patch of soft X-ray emission found with SRG/eROSITA in excess of the background surface brightness, in the same region. The soft X-ray seemingly coherent patch in excess of the background emission, which we dub as the Goat Horn complex, extends over a remarkable area of $\sim 1000$ deg$^2$ and includes an arc-shaped enhancement potentially tracing a cold front. An anti-correlation of the X-ray intensity with the temperature of the plasma responsible for the X-ray emission is also observed. The X-ray bright arc seems to anticipate the radio loop XII by some degrees on the sky. This behavior can be recast in terms of a correlation between X-ray surface brightness and radio depolarization. We explore and discuss different possible scenarios for the source of the diffuse emission in the Goat Horn complex: a large supernova remnant; an outflow from active star formation regions in nearby Galactic spiral arms; a hot atmosphere around the Large Magellanic Cloud. In order to probe these scenarios further, a more detailed characterization on the velocity of the hot gas is required.

We aim at advancing our understanding of magnetic activity and the underlying dynamo mechanism at the end of the main-sequence. To this end, we collected simultaneous X-ray and radio observations for a sample of M7-L0 dwarfs using XMM-Newton jointly with the JVLA and the ATCA. We also included data from the all-sky surveys of eROSITA on board the Russian Spektrum-Roentgen-Gamma mission (SRG) and rotation periods from TESS together with an archival compilation of X-ray and radio data for UCDs from the literature. We limit the sample to objects with rotation period <1d, focusing on the study of a transition in magnetic behavior suggested by a drastic change in the radio detection rate at vsini \approx 38 km/s. We compiled the most up-to-date radio/X-ray luminosity relation for 26 UCDs with rotation periods lower than 1d, finding that rapid rotators lie the furthest away from the G\"udel-Benz relation previously studied for earlier-type stars. Radio bursts are mainly experienced by very fast UCDs, while X-ray flares are seen along the whole range of rotation. We examined the L_{\rm x}/L_{\rm bol} vs P_{\rm rot} relation, finding no evident relation between the X-ray emission and rotation, reinforcing previous speculations on a bimodal dynamo across late-type dwarfs. One radio-detected object has a rotation period consistent with the range of auroral bursting sources; while it displays moderately circularly polarized emission. A radio flare from this object is interpreted as gyrosynchrotron emission, and it displays X-ray and optical flares. We also found a slowly rotating apparent auroral emitter, that is also one of the X-ray brightest radio-detected UCDs. We speculate that this UCD is experiencing a transition of its magnetic behavior since it produces signatures expected from higher mass M dwarfs along with emerging evidence of auroral emission.

Context. During four all-sky surveys (eRASS1--4), eROSITA, the soft X-ray instrument aboard Spektrum-Roentgen-Gamma (SRG) detected a new supersoft X-ray source, eRASSU J060839.5-704014, in the direction of the Large Magellanic Cloud (LMC). Methods. We arranged follow-up observations in the X-ray and optical wavelengths and further searched in archival observations to reveal the nature of the object. Results. We discover pulsations at ~374 s with a pulse profile consistent with 100% modulation. We identify two other periodicities in the eROSITA data, which we establish as aliases due to the sampling of the eROSITA light curve. We identify a multi-wavelength counterpart to the X-ray source in UVW1 and g, r, i, and z images obtained by the optical/UV monitor on XMM-Newton and the Dark Energy Camera at the Cerro Tololo Inter-American Observatory. The timing and spectral characteristics of the source are consistent with a double degenerate ultra-compact binary system in the foreground of the LMC. eRASSU J060839.5-704014 belongs to a rare class of AM CVns, which are important to study in the context of progenitors of SN Ia and for persistent gravitational wave detection. Conclusions. We identify eRASSU J060839.5-704014 as a new double degenerate ultra-compact binary located in the foreground of the LMC.

Detecting a supernova remnant (SNR) along the Galactic plane can be quite challenging. Any new detection reduces the discrepancy between the expected and known number of remnants. In this paper, we present results from a large selection of radio and X-ray data that cover the position of G321.3-3.9. We identified G321.3-3.9 as a new SNR using data collected by several radio surveys spanning a frequency range from 200 MHz to 2300 MHz. Stacked eROSITA data from four consecutive all-sky surveys (eRASS:4) provide spectro-imaging information in the energy band 0.2-8.0 keV. G321.3-3.9 has an elliptical shape with major and minor axes of about 1.7 deg x 1.1 deg. From CHIPASS and S-PASS data, we calculate a spectral index -0.8 +- 0.4, consistent with synchrotron emission from an expanding shell in the Sedov Taylor phase. The eROSITA data show an X-ray diffuse structure filling almost the entire radio shell. Depending on the tested spectral model, a plasma temperature between 0.2 keV (VAPEC) and 0.7 keV (NEI) can be fit. The X-ray spectral analysis allowed us to estimate the column absorption towards G321.3-3.9, which suggests a remnant distance of about 1 kpc by comparison with optical extinction maps.

The latest source catalog of the Fermi-LAT telescope contains more than 7000 $\gamma$-ray sources at GeV energies, with the two dominant source classes thought to be blazars and rotation-powered pulsars. Our target is the identification of possible (young and recycled) pulsar candidates in the sample of 2600 unassociated $\gamma$-ray sources, via their characteristic X-ray and $\gamma$-ray emission. To achieve this, we cross-match the Fermi-LAT catalog with the catalog of X-ray sources in the western Galactic hemisphere from the first four all-sky surveys of SRG/eROSITA. We complement this by identifying X-ray counterparts of known pulsars detected at $\gamma$-ray and radio energies in the eROSITA data. We use a Bayesian cross-matching scheme to construct a probabilistic catalog of possible pulsar-type X-ray counterparts to Fermi-LAT sources. Our method combines the overlap of X-ray and $\gamma$-ray source positions with a probabilistic classification (into pulsar and blazar candidates) of each source based on its $\gamma$-ray properties and a prediction on the X-ray flux of pulsar- or blazar-type counterparts. We provide a catalog of our prior $\gamma$-ray-based classifications of all 2600 unassociated sources in the Fermi-LAT catalog, with around equal numbers of pulsar and blazar candidates. Our final list of candidate X-ray pulsar counterparts, cleaned for spurious detections and sources with obvious non-pulsar counterparts, contains around 900 X-ray sources. We predict between 30 and 40 new pulsars among our top 200 candidates, with around equal expected numbers of young and recycled pulsars. This candidate list may serve as input to future follow-up campaigns, looking directly for pulsations or for the orbital modulation of possible binary companions. We furthermore detect the X-ray counterparts of 15 known rotation-powered pulsars, which were not seen in X-rays before.

As the closest galaxy cluster, the Virgo Cluster is an exemplary environment for the study of large-scale filamentary structure and physical effects that are present in cluster outskirts but absent from the more easily studied inner regions. Here, we present an exploration of the SRG/eROSITA data from five all-sky surveys. eROSITA allows us to resolve the entire Virgo cluster and its outskirts on scales between 1 kpc and 3 Mpc, covering a total area on the sky of about 25 by 25 degrees. We utilize image manipulation techniques and surface brightness profiles to search for extended emission, surface brightness edges, and features in the outskirts. We employ a method of comparing mean and median profiles to measure gas clumping beyond the virial radius. Surface brightness analysis of the cluster and individual sectors of the cluster reveal the full extent of previously identified cold fronts to the north and south. The emissivity bias due to gas clumping, which we quantify over three orders of magnitude in radial range, is found to be mild, consistent with previous findings. We find an estimated virial gas mass of $M_{\mathrm{gas},r<r_{200}} = (1.98 \pm 0.70) \times 10^{13}$ M$_\odot$. Through imaging analysis we detect the presence of extended emission spanning 320 kpc to the southwest of M49. The extension has a significance of 3.15sigma and is coincident with radio emission detected with LOFAR, which could be evidence of an accretion shock or turbulent re-acceleration as the background W' cloud or M49 group falls into the cluster and interacts with the ICM.

Galaxy cluster gas temperatures ($T$) play a crucial role in many cosmological and astrophysical studies. However, it has been shown that $T$ measurements can vary between different X-ray telescopes. These $T$ biases can propagate to several cluster applications for which $T$ can be used. Thus, it is important to accurately cross-calibrate X-ray instruments to account for systematic biases. In this work, we present the cross-calibration between SRG/eROSITA and Chandra/ACIS, and between SRG/eROSITA and XMM-Newton/EPIC, using for the first time a large sample of galaxy cluster $T$. To do so, we use the first eROSITA All-Sky Survey data and a large X-ray flux-limited cluster catalog. We measure X-ray $T$ for 186 independent cluster regions with both SRG/eROSITA and Chandra/ACIS in a self-consistent way, for three energy bands; 0.7-7 keV (full), 0.5-4 keV (soft), and 1.5-7 keV (hard). We do the same with SRG/eROSITA and XMM-Newton/EPIC for 71 different cluster regions and all three bands. We find that SRG/eROSITA measures systematically lower $T$ than the other two instruments. For the full band, SRG/eROSITA returns 20$\%$ and 14$\%$ lower $T$ than Chandra/ACIS and XMM-Newton/EPIC respectively, when the two latter instruments measure $k_{\text{B}}T\approx 3$ keV each. The discrepancy increases to 38\% and 32\% when Chandra/ACIS and XMM-Newton/EPIC measure $k_{\text{B}}T\approx 10$ keV respectively. For low-$T$ galaxy groups, the discrepancy becomes milder. The soft band shows a marginally lower discrepancy than the full band. In the hard band, the cross-calibration of SRG/eROSITA and the other instruments show stronger differences. We could not identify any possible systematic biases that significantly alleviated the tension. Finally, we provide conversion factors between SRG/eROSITA, Chandra/ACIS, and XMM-Newton/EPIC $T$ which will be beneficial for future cluster studies.

Context. Cataclysmic variables with degenerate donors which have evolved past the period minimum, also known as period-bouncers, are predicted to make up a great portion of the cataclysmic variable population, between 40 and 70 percent. However, either due to shortcomings in the models or due to the intrinsic faintness of these strongly evolved systems, only a few have been confidently identified so far. Aims. We have compiled a multi-wavelength catalog of period-bouncers and cataclysmic variables around the period minimum from the literature in order to provide an in-depth characterization of the elusive subclass of period-bounce CVs that will help in the identification of new candidates. Methods. In this study we combine published or archival multi-wavelength data with new X-ray observations from the all-sky surveys carried out with the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) onboard the Spektrum-Roentgen-Gamma spacecraft (SRG). Our catalog comprises 192 cataclysmic variables around the period minimum that were chosen as likely period bounce candidates based on reported short orbital periods and low donor mass. This sample helped us establish specific selection parameters that have been used to compile a scorecard which rates a systems likelihood of being a period-bouncer. Results. Our scorecard correctly assigns high scores to the already confirmed period-bouncers in our literature catalog and it identifies 80 additional strong period-bounce candidates present in the literature that have not been classified as such. We established two selection cuts based on the X-ray-to-optical flux ratio and the typical X-ray luminosity observed from the 8 already confirmed period-bouncers with eROSITA data. These X-ray selection cuts led to the categorization of 5 systems as new period-bouncers, increasing their population number to 22 systems.

Evolutionary models suggest that the initial growth phases of active galactic nuclei (AGN) are dust-enshrouded, and characterized by jet/wind outflows that should gradually clear the interstellar medium (ISM) in the host by heating and/or expelling the surrounding gas. eFEDSJ091157.4+014327 (z~0.6) was selected from X-ray samples for its characteristics that are similar to sources with outflows which include red, obscured (2.7x10$^{22}$ cm$^{-2}$ ) and X-ray luminous (6.5x10$^{44}$ erg s$^{-1}$). We aim to explore the environment around the red quasar and characterise kinematics within the system. We use spatially resolved spectroscopic data from Multi Unit Spectroscopic Explorer (MUSE) with an average seeing of 0.6" to construct flux, velocity and velocity dispersions maps. We found that the quasar is embedded in an interacting and merging system with three other galaxies ~ 50 kpc from its nucleus. Spatially resolved kinematics reveal that the quasar has extended ionised outflows of up to 9.4 kpc with positive and negative velocities up to 1000 km s$^{-1}$ and -1200 km s$^{-1}$, respectively. The velocity dispersion (W$_{80}$) ranges from 600-1800 km s$^{-1}$. We associate the presence of turbulent and high-velocity components with the outflow. The total mass outflow rate is estimated to be 9.6 M$_{\odot}$ yr$^{-1}$ and kinetic power of 1.9x10$^{42}$ erg s$^{-1}$. Considering different recipes of velocity and AGN bolometric luminosities, the kinetic coupling efficiencies range from 0.01%-0.2% and the momentum boosts from 0.04-0.5. The kinetic coupling efficiency values are low which indicates that the outflow is not very significant from the energetic point of view but is slightly consistent with theoretical predictions of radiation-pressure-driven outflows. The mass loading factor of 4.8 is an indication that these outflows are more likely AGN-driven than star formation-driven.

During its calibration and performance verification phase, the eROSITA instrument aboard the SRG satellite performed a uniform wide--area X-ray survey of approximately 140 deg$^{2}$ in a region of the sky known as the eROSITA Final Equatorial Depth Survey (eFEDS). The primary aim of eFEDS is to demonstrate the scientific performance to be expected at the end of the 8-pass eROSITA all sky survey. This will provide the first focussed image of the whole sky in the hard X-ray ($>2$~keV) bandpass. The expected source population in this energy range is thus of great interest, particularly for AGN studies. We use the 2.3--5 keV selection presented by Brunner et al. (2022) to construct a sample of 246 point-like hard X-ray sources for further study and characterization. These are classified as either extragalactic ($\sim 90$~\%) or Galactic ($\sim 10$~\%), with the former consisting overwhelmingly of AGN and the latter active stars. We concentrate our further analysis on the extragalactic/AGN sample, describing their X-ray and multiwavelength properties and comparing them to the eFEDS main AGN sample selected in the softer 0.2-2.3 keV band. The eROSITA hard band selects a subsample of sources that is a factor $>10$ brighter than the eFEDS main sample. The AGN within the hard population reach up to $z=3.2$ but on the whole are relatively nearby, with median $z$=0.34 compared to $z$=0.94 for the main sample. The hard survey probes typical luminosities in the range $\log L_{\rm X} = 43-46$. X-ray spectral analysis shows significant intrinsic absorption (with $\log N_{\rm H}>21$) in $\sim 20$~\% of the sources, with a hard X-ray power law continuum with mean $<\Gamma>=1.83\pm0.04$, typical of AGN, but slightly harder than the soft-selected eROSITA sample. (abridged)

Context: Environmental soft protons have affected the performance of the X-ray detectors on board Chandra and XMM-Newton, and they pose a threat for future high energy astrophysics missions with larger aperture, such as ATHENA. Aims: We aim at estimating soft proton fluxes at the ATHENA detectors independently of any modelisation of the external fluxes in the space environment.We analysed the background data measured by eROSITA on board SRG, and with the help of simulations we defined a range of values for the potential count-rate of quiet-time soft protons focused through the mirror shells. We used it to derive an estimate of soft proton fluxes at the ATHENA detectors, assuming ATHENA in the same L2-orbit as SRG. Results: The scaling, based on the computed proton transmission yields of the optics and optical/thermal filters of eROSITA and ATHENA, indicates that the soft proton induced WFI and X-IFU backgrounds could be expected close to the requirement. Conclusions: No soft proton fluxes detrimental to the observations have been suffered by eROSITA during its all-sky survey in orbit around L2. Regardless of where ATHENA will be placed (L1 or L2), our analysis suggests that increasing somewhat the thickness of the WFI optical blocking filter, e.g. by 30%, would help to reduce the soft proton flux onto the detector, in case the planned magnetic diverters perform worse than expected due to soft proton neutralisation at the mirror level.

The planet GJ 367 b is a recently discovered high-density sub-Earth orbiting an M dwarf star. Its composition was modelled to be predominantly iron with a potential remainder of a hydrogen-helium envelope. Here we report an X-ray detection of this planet's host star for the first time, using data from the spectro-imaging X-ray telescope eROSITA onboard the Spectrum-Roentgen-Gamma (SRG) mission. We characterise the magnetic activity of the host star from the X-ray data and estimate the present-day mass-loss rate of the potential atmosphere of the planet driven by the high-energy irradiation. We find that despite the very low activity level of the host star the potential mass loss rate is so high that any atmospheric remainders would evaporate in about 15 million years. Since the activity level of the host star indicates that the system is several Gigayears old, it is very unlikely that the planet currently still hosts any atmosphere.

The high-energy environment of the host stars could be deleterious for their planets. It is crucial to ascertain this contextual information to fully characterize the atmospheres of terrestrial exoplanets. We aim to fully characterize a unique triple system, LTT 1445, with three known rocky exoplanets around LTT 1445A. The X-ray irradiation and flaring of this system are studied through a new 50 ks Chandra observation, which is divided into 10 ks, 10 ks, and 30 ks segments conducted two days apart, and two months apart, respectively. This is complemented by an archival Chandra observation approximately one year earlier and repeated observations with eROSITA (extended ROentgen Survey with an Imaging Telescope Array), the soft X-ray instrument on the Spectrum-Roentgen-Gamma (SRG) mission, enabling the investigation of X-ray flux behavior across multiple time scales. The flux data acquired from these observations serve as a basis for estimating the photo-evaporation mass loss of the individual exoplanets with their host stars. To gain deeper insights into the environmental context influenced by XUV flux and to better understand the anticipated atmospheric conditions of the planets orbiting the A component, we integrate the use of the planet modeling package, VPLanet. Our findings indicate that LTT 1445C is the primary contributor to X-ray emissions, with additional input from LTT 1445B. Moreover, our study confirms that LTT1445A, recognized as a slowly-rotating star, exhibits no significant flare activity in the observed dataset. The observed results also suggest that the X-ray emissions from the LTT 1445BC components do not pose a greater threat to the planets orbiting LTT 1445A than the emissions from A itself. According to simulation results, LTT 1445Ad might have the capacity to retain its water surface.

Aims. Compact white-dwarf binaries are selected from spectra obtained in the early SDSS-V plate program. A dedicated set of SDSS plate observations were carried out in the eFEDS field, providing spectroscopic classifications for a significant fraction of the optically bright end (r < 22.5) of the X-ray sample. The identification and subclassification rests on visual inspections of the SDSS spectra, spectral variability, color-magnitude and color-color diagrams involving optical and X-ray fluxes, optical variability and literature work. Results. Upon visual inspection of SDSS spectra and various auxiliary data products we have identified 26 accreting compact white-dwarf binaries (aCWDBs) in eFEDS, of which 24 are proven X-ray emitters. Among those 26 objects are 12 dwarf novae, three WZ Sge-like disk-accreting non-magnetic CVs with low accretion rates, five likely non-magnetic high accretion rate novalike CVs, two magnetic CVs of the polar subcategory, and three double degenerates (AM CVn objects). Period bouncing candidates and magnetic systems are rarer than expected in this sample, but it is too small for a thorough statistical analysis. Fourteen of the systems are new discoveries, of which five are fainter than the Gaia magnitude limit. Thirteen aCWDBs have measured or estimated orbital periods, of which five were presented here. Through a Zeeman analysis we revise the magnetic field estimate of the polar system J0926+0105, which is likely a low-field polar at B = 16 MG. We quantify the success of X-ray versus optical/UV selection of compact white-dwarf binaries which will be relevant for the full SDSS-V survey. We also identify six white-dwarf main-sequence (WDMS) systems, among them one confirmed pre-CV at an orbital period of 17.6 hours and another pre-CV candidate.

The soft X-ray instrument eROSITA on board the Spectrum-Roentgen-Gamma (SRG) observatory has successfully completed four of the eight planned all-sky surveys, detecting almost one million X-ray sources during the first survey (eRASS1). The catalog of this survey will be released as part of the first eROSITA data release (DR1). Based on X-ray aperture photometry, we provide flux upper limits for eRASS1 in several energy bands. We cover galactic longitudes between $180^{\circ}\lesssim l \lesssim 360^{\circ}$ (eROSITA-DE). These data are crucial for studying the X-ray properties of variable and transient objects, as well as non-detected sources in the eROSITA all-sky survey data. We performed aperture photometry on every pixel of the SRG/eROSITA standard pipeline data products for all available sky tiles in the single detection band ($0.2 - 2.3$ keV). Simultaneously, we performed the same analysis in the three-band detection at soft ($0.2-0.6$ keV), medium ($0.6-2.3$ keV), and hard ($2.3-5.0$ keV) energy bands. Based on the combination of products for the individual bands, we are also able to provide aperture photometry products and flux upper limits for the $0.2 - 5.0$ keV energy band. The upper limits were calculated based on a Bayesian approach that utilizes detected counts and background within the circular aperture. The final data products consist of tables with the aperture photometry products (detected counts, background counts, and exposure time), a close-neighbor flag, and the upper flux limit based on an absorbed power-law spectral model ($\Gamma=2.0, \; N_{\rm H}=3\times10^{20}$ cm$^{-2}$). The upper limits are calculated using the one-sided $3\sigma$ confidence interval (CL) of a normal distribution, representing CL = 99.87\%. The aperture photometry products allow for an easy computation of upper limits at any other confidence interval and spectral model. ...

The eROSITA instrument aboard the Spectrum Roentgen Gamma (SRG) satellite has performed its first all-sky survey between December 2019 and June 2020. This paper presents the resulting hard X-ray (2.3-5 keV) sample, the first created from an all-sky imaging survey in the 2-8 keV band, for sources within western galactic sky. The 5466 hard X-ray selected sources detected with eROSITA are presented and discussed. The Bayesian statistics-based code NWAY is used to identify the counterparts for the X-ray sources. These sources are classified based on their multiwavelength properties, and the literature is searched to identify spectroscopic redshifts, which further inform the source classification. A total of 2547 sources are found to have good-quality counterparts, and 111 of these are detected only in the hard band. Comparing with other hard X-ray selected surveys, the eROSITA hard sample covers a larger redshift range and probes dimmer sources, providing a complementary and expanded sample as compared to Swift-BAT. Examining the column density distribution of missed and detected eROSITA sources present in the follow-up catalog of Swift BAT 70 month sources, it is demonstrated that eROSITA can detect obscured sources with column densities $>10^{24}$ cm$^{-2}$, but that the completeness drops rapidly after $10^{23}$ cm$^{-2}$. A sample of hard-only sources, many of which are likely to be heavily obscured AGN, is also presented and discussed. X-ray spectral fitting reveals that these sources have extremely faint soft X-ray emission and their optical images suggest that they are found in more edge-on galaxies with lower b/a. The resulting X-ray catalog is demonstrated to be a powerful tool for understanding AGN, in particular heavily obscured AGN found in the hard-only sample.

The study of the entire population of SNRs in a galaxy helps us to understand the underlying stellar populations, the environments, in which the SNRs are evolving, and the stellar feedback on the ISM. The all-sky survey carried out by the extended Roentgen Survey with an Imaging Telescope Array (eROSITA) on board Spektrum-Roentgen-Gamma (Spektr-RG, SRG) has provided us with spatially and spectrally resolved X-ray data of the entire Large Magellanic Cloud (LMC) and its immediate surroundings in the soft X-ray band down to 0.2 keV. We performed a multiwavelength analysis of previously known SNR candidates and newly detected SNRs and SNR candidates. We applied the Gaussian gradient magnitude (GGM) filter to the eROSITA images of the LMC to highlight the edges of the shocked gas in order to find new SNRs. We compared the X-ray images with those of their optical and radio counterparts to investigate the true nature of the extended emission. We used the Magellanic Cloud Emission Line Survey (MCELS) for the optical data. For the radio comparison, we used data from the Australian Square Kilometre Array Pathfinder (ASKAP) survey of the LMC. Using the VISTA survey of the Magellanic Clouds (VMC) we have investigated the possible progenitors of the new SNRs and SNR candidates in our sample. We present the most updated catalogue of SNRs in the LMC. The eROSITA data have allowed us to confirm two of the previous SNR candidates and discover 16 new extended sources. We confirm 3 of them as new SNRs, while we propose the remaining 13 as new X-ray SNR candidates. We also present the first analysis of the follow-up XMM-Newton observation of MCSNR J0456-6533 discovered with eROSITA. Among the new candidates, we propose J0614-7251 (4eRASSU J061438.1-725112) as the first X-ray SNR candidate in the outskirts of the LMC.

We apply a stacking technique to gain enough statistics to detect the hot CGM around galaxies. We use the X-ray data from the first four SRG/eROSITA all-sky surveys (eRASS:4). We discuss how the satellite galaxies could bias the stacking and carefully build the central galaxy samples based on the SDSS spectroscopic survey and halo-based group finder algorithm and isolated galaxy sample from the ninth data release of the DESI Legacy survey (LS DR9, photometric). We mask the detected X-ray point sources and carefully model the X-ray emission from the unresolved active galactic nuclei (AGN) and X-ray binaries (XRB) to obtain the X-ray emission from the hot CGM. The X-ray surface brightness profiles are measured for $\log(M_*)>10.0$ or $\log(M_{\rm 200m})>11.5$ central galaxies, and $\log(M_*)>9.5$ isolated galaxies. We detect the X-ray emission around MW-mass ($\log(M_*)=10.5-11.0$) and more massive central galaxies extending up to the virial radius ($R_{\rm vir}$). The signal-to-noise ratio of the extended emission around the MW-mass galaxy is about $8.1\sigma$ within $R_{\rm vir}$. We use the $\beta$ model to describe the X-ray surface brightness profiles of the hot CGM. We obtain a central surface brightness of $S_{\rm X,0}\approx 3.1\times10^{35}\rm erg/s/kpc^2$ and $\beta \approx0.42$ for MW-mass galaxy. We estimate the baryon budget of the hot CGM and obtain a value lower than the $\Lambda CDM$ cosmology predicted. Our results set a firm footing for the presence of a hot CGM around MW-mass and more massive central galaxies. These measurements constitute a new benchmark for galaxy evolution models and possible implementations of feedback processes therein.

Understanding how the hot circum-galactic medium (CGM) properties relate to the galaxy's properties can constrain galaxy evolution models. We aim to measure the scaling relations between the X-ray luminosity of the hot CGM and the fundamental properties of a galaxy, i.e., its stellar mass and halo mass. We calculate the X-ray luminosity of the hot CGM based on the surface brightness profiles of central galaxy samples measured in Zhang et al. (2024a, submitted) from Spectrum Roentgen Gamma (SRG)/eROSITA all-sky survey data. We relate the X-ray luminosity to the galaxies' stellar and halo mass. We compare the observed relations to the TNG, EAGLE, and SIMBA simulations. The hot CGM X-ray luminosity correlates with the galaxy's stellar mass ($M_*$). It increases from $2.1 \pm 1.3\times10^{39} \rm erg/s$ to $2.0 \pm 0.1\times10^{41} \rm erg/s$, when $\log(M_*)$ increases from 10.0 to 11.5. A double power law describes the correlation, with a break at $\log(M_*)=11.28\pm 0.03$ and a power-law index or $1.9\pm 0.2$ ($4.2\pm0.1$) below (above) the break. The hot CGM X-ray luminosity as a function of halo mass is measured within $\log(M_{\rm 500c})=11.3-13.7$, extending our knowledge of the scaling relation by more than two orders of magnitude. $L_{\rm X,CGM}$ increases with $M_{\rm 500c}$ from $2.7 \pm 0.9\times10^{39}\ \rm erg/s$ at $\log(M_{\rm 500c})=11.3$ to $9.2 \pm 0.4\times10^{41}\ \rm erg/s$ at $\log(M_{\rm 500c})=13.7$. The relation follows a power law of $\log(L_{\rm X,CGM})= (1.35\pm 0.04)\times \log(M_{\rm 500c})+(23.8\pm0.5)$. We find a general agreement between simulations and observation. We explore, at the low mass end, the average scaling relations between the CGM X-ray luminosity and the galaxy's stellar mass or halo mass, which constitutes a new benchmark for galaxy evolution models and feedback processes.

[abridged] Hot plasma plays a crucial role in regulating the baryon cycle within the Milky Way, flowing from the energetic sources in the Galactic center and disc, to the corona and the halo Taking advantage of the Spectrum Roentgen Gamma (SRG)/eROSITA first all-sky survey, in this work we aim to provide a panoramic view of the hot circumgalactic medium (CGM) of the Milky Way. The energy resolution of eROSITA enables us to map, for the first time, the sky within the narrow energy bands characteristic of soft X-ray emission lines. We present the eROSITA eRASS1 half sky maps in narrow energy bands corresponding to the most prominent soft X-ray lines: O VII and O VIII, which allow us to constrain the distribution of the hot plasma within and surrounding the Milky Way. We removed the expected contribution associated with the cosmic X-ray background, the time-variable solar wind charge exchange, the local hot bubble and foreground absorption. We use the line ratio of the oxygen lines as a proxy to constrain the temperature of the warm-hot CGM and we define a pseudo-temperature $\mathcal{T}$ map. The map highlights how different regions are dominated by different thermal components. Towards the outer halo, the temperature distribution of the CGM is consistent with being constant ($\Delta \mathcal{T} / \langle \mathcal{T}\rangle) \leq 4\%$) on angular scales of 2-20 deg, while significant variations $\sim 12\%$ are observed on many tens of degrees scales, when comparing the northern and southern hemisphere. The pseudo-temperature map shows significant variations across the borders of the eROSITA bubbles, therefore suggesting temperature variations, possibly linked to shocks, between the interior of the Galactic outflow and the unperturbed CGM. In particular, a "shell" of colder material appears to be present close to the edge of the eROSITA bubbles.

A thorough inspection of known Galactic Supernova Remnants (SNRs) along the Galactic plane with SRG/eROSITA yielded the detection of the X-ray counterpart of the SNR G279.0+01.1. The SNR is located just 1.5 deg above the Galactic plane. Its X-ray emission emerges as an incomplete, partial shell of $\sim$3 deg angular extension. It is strongly correlated to the fragmented shell-type morphology of its radio continuum emission. The X-ray spatial morphology of the SNR seems to be linked to the presence of dust clouds in the surroundings. The majority of its X-ray emission is soft (exhibiting strong O, Ne and Mg lines), and occurs in a narrow range of energies between 0.3 and 1.5 keV. Above 2.0 keV the remnant remains undetected. The remnant's X-ray spectrum is of purely thermal nature. Constraining the X-ray absorption column to values which are consistent with optical extinction data from the remnant's location favours non-equilibrium over equilibrium models. A non-equilibrium two-temperature plasma model of $\mathrm{kT}\sim0.3$~keV and $\mathrm{kT}\sim0.6$~keV, and an absorption column density of $\mathrm{N_{H}}\sim0.3~\mathrm{cm^{-2}}$ describes the spectrum of the entire remnant well. Significant temperature variations across the remnant have been detected. Employing 14.5 years of Fermi-LAT data, we carried out a comprehensive study of the extended GeV source 4FGL J1000.0-5312e. By refining and properly modeling the GeV excess originating from the location of the remnant, we conclude that the emission is likely related to the remnant itself rather than being co-located by chance. We also discuss implications of the new X-ray data to the estimates of the distance and age of the remnant.

Simeis 147 (S147, G180.0-01.7, ``Spaghetti nebula'') is a supernova remnant (SNR) extensively studied across the entire electromagnetic spectrum, from radio to GeV $\gamma$-rays, except in X-rays. In this study, we report the first detection of significant X-ray emission from the entire SNR. Here, and in a companion paper, we present studies of X-ray emission from the S147 nebula using the data of the extended ROentgen Survey Imaging Telescope Array (eROSITA) onboard the Russian-German Spektrum Roentgen Gamma (SRG). The object is located at the Galactic anti-center, and its 3 deg size classifies it among the largest SNRs ever detected in X-rays. Overall, the X-ray emission morphology as observed with eROSITA is fully confined within the boundaries of both radio synchrotron and H$\alpha$ emission, except for the Western edge of the remnant where radio and H$\alpha$ emission appears to extend further to the West compared to X-rays. The X-ray emission is predominantly soft with a strong detection between 0.5-1.0 keV, leaving S147 undetected above 2.3 keV. The X-ray emission is purely thermal, exhibiting strong O, Ne, and Mg lines, whereas it lacks heavier-Z elements. A model of non-equilibrium collisional plasma, with a gas temperature of $kT=0.22^{-0.03}_{+0.02}$~keV, and an absorption column density of $N_\mathrm{{H}}=0.30_{-0.03}^{+0.04}\cdot10^{22}~\mathrm{cm^{-2}}$ ($\tau=4.27^{+1.87}_{-0.99}~\mathrm{\cdot10^{10}s~ cm^{-3}}$), is preferred over a collisional plasma model in equilibrium with $kT=0.11\pm0.01$~keV and with $N_\mathrm{{H}}=0.51\pm0.02\cdot10^{22}~\mathrm{cm^{-2}}$. By employing $\sim$14.5 years of Fermi-LAT data, our study confirms the association of the remnant with a spatially coincident diffuse GeV excess, namely 4FGL J0540.3+2756e or FGES J0537.6+2751. Age and distance estimates of the remnant are also reported based on the eROSITA data.

We construct models of two exotic objects: (i) a wormhole whose throat is hidden by a stellar object like a neutron star; and (ii) a wormhole inside a black hole. We work within Einstein's gravity coupled to two scalar fields with a specific choice of the scalar field Lagrangian. In general, the model contains ghosts, but they are eliminated using the constraints given by the Lagrange multiplier fields. The constraints are a generalization of the mimetic constraint, where non-dynamical dark matter effectively appears. As a result, in our model, instead of the non-dynamical dark matter, non-dynamical exotic matter like a phantom effectively arises. For the mixed wormhole-plus-star system, we find the corresponding mass-radius relations and show that it is possible to get characteristics comparable to those of ordinary neutron stars. For the wormhole inside the black hole, we find an extremal limit where the radius of the throat coincides with the radius of the event horizon and demonstrate that the Hawking temperature vanishes in this limit.

In the framework of the extended Einstein-aether-axion theory we study the model of a two-level aetheric control over the evolution of a spatially isotropic homogeneous Universe filled with axionic dark matter. Two guiding functions are introduced, which depend on the expansion scalar of the aether flow, equal to the tripled Hubble function. The guiding function of the first type enters the aetheric effective metric, which modifies the kinetic term of the axionic system; the guiding function of the second type predetermines the structure of the potential of the axion field. We obtained new exact solutions of the total set of master equations of the model (with and without cosmological constant), and studied in detail four analytically solvable submodels, for which both guiding functions are reconstructed and illustrations of their behavior are presented.

I argue that research in physics operates under an implicit community philosophy, and I offer a definition I think physicists would accept, by and large. I compare this definition to what philosophers, sociologists, and historians of science, with physicists, say we are doing.

Many well motivated dark matter (DM) particle candidates can decay into detectable X-ray photons. We analyze eROSITA Final Equatorial Depth Survey (eFEDS) from eROSITA early data release to search for unexplained X-ray lines that could indicate DM signal. Having discovered no extra line, we set limits on DM decay rate in mass range between 1.8-18 keV, and constrain the parameter space of two DM particles: sterile neutrino and axion-like particles. Finally we also study the projected sensitivity of eROSITA full sky search, showing that eROSITA all-sky survey is expected to set the most stringent limits in the soft X-ray band.

We investigate inflationary particle production associated with a spectator ultralight scalar field, which has been recently proposed as a plausible dark matter candidate. In this framework, we select the Starobinsky potential to drive the inflationary epoch, also discussing the case of a nonminimally coupled inflaton field fueled by a quartic symmetry-breaking potential. We focus on particle production arising from spacetime perturbations, which are induced by inflaton fluctuations during the quasi-de Sitter stage of inflation. In particular, we construct the first order Lagrangian describing interaction between inhomogeneities and the spectator field, quantifying superhorizon particle production during slow-roll. We then compare this mechanism with gravitational particle production associated with an instantaneous transition from inflation to the radiation dominated era. We show that the amount of particles obtained from perturbations is typically non-negligible and it is significantly enhanced on super-Hubble scales by the nonadiabatic inflationary expansion. Possible implications for primordial entanglement generation are also debated.

The recently reported signal of common red noise between pulsars by several pulsar timing array collaborations has been thought as evidence of the stochastic gravitational wave background (SGWB) due to the Helling-Downs correlation. In this study, we will search for the non-linearities of SGWB through its effect on the overlap reduction function in NANOGrav 15-year data set. In particular, we focus on a folded non-Gaussian component to SGWB whose amplitude is quantified with a single parameter $\alpha$ in the unpolarized case. The results reveal that such a non-Gaussianity of SGWB is favored, and $\alpha=0$ (the Gaussian SGWB) is excluded at about $3\sigma$ level.

We have conducted a study on the thermal properties of the recently developed nuclear energy density functional known as BCPM. This functional is founded on microscopic calculations that incorporate the realistic Argonne $v_{18}$ potential along with Urbana-type three-body forces. BCPM has demonstrated success in describing finite nuclei and cold neutron stars. However, investigating the properties of hot $\beta$-stable matter under both neutrino-free and neutrino-trapped scenarios is vital for astrophysical applications. In this study, we investigate the BCPM equation of state for $\beta$-stable, neutrino-free matter at finite temperatures, taking into consideration the hot inner crust and applying the frozen correlation approximation. Such an equation of state holds significant importance for hot compact objects, such as the final result of a binary neutron star merger event. Our exploration has unveiled the presence of cluster regions, persisting up to a temperature of approximately $7.2$ MeV, denoted as the limiting temperature. Beyond this limiting temperature, clusters are not anticipated to manifest. At temperatures below the limiting threshold, clusters within the inner crust are encompassed by uniform matter with varying densities, facilitating the distinction between the higher and lower transition density branches. Furthermore, we have computed mass-radius relationship, while assuming an isothermal profile for neutron star matter at diverse temperature values. Our findings indicate that the results of the hot inner crust substantially influences the mass-radius relationship, resulting in the formation of larger, more inflated neutron stars. A thorough analysis of the hot inner crust is therefore essential for the study of proto-neutron stars.

We present a new method and implementation to obtain Bayesian posteriors on the amplitude parameters $\{h_0, \cos \iota, \psi, \phi_0\}$ of continuous-gravitational waves emitted by known pulsars. This approach leverages the well-established $\mathcal{F}$-statistic framework and software. We further explore the benefits of employing a likelihood function that is analytically marginalized over $\phi_0$, which avoids signal degeneracy problems in the $\psi$-$\phi_0$ subspace. The method is tested on simulated signals, hardware injections in Advanced-LIGO detector data, and by performing percentile-percentile (PP) self-consistency tests of the posteriors via Monte-Carlo simulations. We apply our methodology to PSR J1526-2744, a recently discovered millisecond pulsar. We find no evidence for a signal and obtain a Bayesian upper limit $h_0^{95\%}$ on the gravitational-wave amplitude of approximately $7 \times 10^{-27}$, consistent with a previous frequentist upper limit.

Why does the Sun have a radius around 696000~km? We will see in this article that dimensional arguments can be used to understand the size of the Sun and of a few other things along the way. These arguments are not new and can be found scattered in textbooks. They are presented here in a succinct way in order to better confront the kinematic and mechanical viewpoints on size. We derive and compare a number of expressions for the size of the Sun and relate large and small scales. We hope that such presentation will be useful to students, instructors and researchers alike.

Cold dark matter axions produced in the post-inflationary Peccei-Quinn symmetry breaking scenario serve as clear targets for their experimental detection, since it is in principle possible to give a sharp prediction for their mass once we understand precisely how they are produced from the decay of global cosmic strings in the early Universe. In this paper, we perform a dedicated analysis of the spectrum of axions radiated from strings based on large scale numerical simulations of the cosmological evolution of the Peccei-Quinn field on a static lattice. Making full use of the massively parallel code and computing resources, we executed the simulations with up to $11264^3$ lattice sites, which allows us to improve our understanding of the dependence on the parameter controlling the string tension and thus give a more accurate extrapolation of the numerical results. We found that there are several systematic effects that have been overlooked in previous works, such as the dependence on the initial conditions, contaminations due to oscillations in the spectrum, and discretisation effects, some of which could explain the discrepancy in the literature. We confirmed the trend that the spectral index of the axion emission spectrum increases with the string tension, but did not find a clear evidence of whether it continues to increase or saturates to a constant at larger values of the string tension due to the severe discretisation effects. Taking this uncertainty into account and performing the extrapolation with a simple power law assumption on the spectrum, we find that the dark matter mass is predicted in the range of $m_a \approx 95$-$450\,\mu\mathrm{eV}$.