Papers for Friday, Apr 22 2022

In this paper, the X-ray Earth occultation (XEO) of the Crab Nebula is investigated by using the Hard X-ray Modulation Telescope (Insight-HXMT). The pointing observation data on the 30th September, 2018 recorded by the Low Energy X-ray telescope (LE) of Insight-HXMT are selected and analyzed. The extinction lightcurves and spectra during the X-ray Earth occultation process are extracted. A forward model for the XEO lightcurve is established and the theoretical observational signal for lightcurve is predicted. The atmospheric density model is built with a scale factor to the commonly used MSIS density profile within a certain altitude range. A Bayesian data analysis method is developed for the XEO lightcurve modeling and the atmospheric density retrieval. The posterior probability distribution of the model parameters is derived through the Markov Chain Monte Carlo (MCMC) algorithm with the NRLMSISE-00 model and the NRLMSIS 2.0 model as basis functions and the best-fit density profiles are retrieved respectively. It is found that in the altitude range of 105--200 km, the retrieved density profile is 88.8% of the density of NRLMSISE-00 and 109.7% of the density of NRLMSIS 2.0 by fitting the lightcurve in the energy range of 1.0--2.5 keV based on XEOS method. In the altitude range of 95--125 km, the retrieved density profile is 81.0% of the density of NRLMSISE-00 and 92.3% of the density of NRLMSIS 2.0 by fitting the lightcurve in the energy range of 2.5--6.0 keV based on XEOS method. In the altitude range of 85--110 km, the retrieved density profile is 87.7% of the density of NRLMSISE-00 and 101.4% of the density of NRLMSIS 2.0 by fitting the lightcurve in the energy range of 6.0--10.0 keV based on XEOS method. This study demonstrates that the XEOS from the X-ray astronomical satellite Insight-HXMT can provide an approach for the study of the upper atmosphere.

We present a far-ultraviolet (FUV) study of the globular cluster M30 (NGC 7099). The images were obtained using the Advanced Camera for Surveys (ACS/SBC, F150LP, FUV) and the Wide Field Planetary Camera 2 (WFPC2, F300W, UV) on board the Hubble Space Telescope (HST). We compare the catalogue of FUV objects to ten known X-ray sources and find six confident matches of two cataclysmic variables (CVs), one RS CVn, one red giant with strong FUV emission and two sources only detected in the FUV. We also searched for variable sources in our dataset and found a total of seven blue stragglers (BSs), four horizontal branch (HB) stars, five red giant branch stars, 28 main sequence stars and four gap objects that demonstrated variability. One BS star is a known W-UMa contact binary, one of the gap objects is a known CV identified in this work to be a dwarf nova, and the three other gap sources are weak variables. The periods and positions of two of the variable HB stars match them to two previously known RR Lyrae variables of types RRab and RRc.

The origins of type Ia supernovae (SNe Ia) are still debated. Some of the leading scenarios involve a double detonation in double white dwarf (WD) systems. In these scenarios, helium shell detonation occurs on top of a carbon-oxygen (CO) WD, which then drives the detonation of the CO-core, producing a SN Ia. Extensive studies have been done on the possibility of a double helium detonation, following a dynamical helium mass-transfer phase onto a CO-WD. However, 3D self-consistent modeling of the double-WD system, the mass transfer, and the helium shell detonation have been little studied. Here we use 3D hydrodynamical simulations to explore this case in which a helium detonation occurs near the point of Roche lobe overflow of the donor WD and may lead to an SN Ia through the dynamically driven double-degenerate double-detonation (D6) mechanism. We find that the helium layer of the accreting primary WD does undergo a detonation, while the underlying carbon-oxygen core does not, leading to an extremely rapid and faint nova-like transient instead of a luminous SN Ia event. This failed core detonation suggests that D6 SNe Ia may be restricted to the most massive carbon-oxygen primary WDs. We highlight the nucleosynthesis of the long-lived radioisotope $^{44}$Ti during explosive helium burning, which may serve as a hallmark both of successful as well as failed D6 events which subsequently detonate as classical double-degenerate mergers.

The existence of mutually correlated thin and rotating planes of satellite galaxies around both the Milky Way (MW) and Andromeda (M31) calls for an explanation. Previous work in Milgromian dynamics (MOND) indicated that a past MW-M31 encounter might have led to the formation of these satellite planes. We perform the first-ever hydrodynamical MOND simulation of the Local Group using Phantom of RAMSES. We show that an MW-M31 encounter at $z \approx 1$, with a perigalactic distance of about 80 kpc, can yield two disc galaxies at $z=0$ oriented similarly to the observed galactic discs and separated similarly to the observed M31 distance. Importantly, the tidal debris are distributed in phase space similarly to the observed MW and M31 satellite planes, with the correct preferred orbital pole for both. The MW-M31 orbital geometry is consistent with the presently observed M31 proper motion despite this not being considered as a constraint when exploring the parameter space. The mass of the tidal debris around the MW and M31 at $z=0$ compare well with the mass observed in their satellite systems. The remnant discs of the two galaxies have realistic radial scale lengths and velocity dispersions, and the simulation naturally produces a much hotter stellar disc in M31 than in the MW. However, reconciling this scenario with the ages of stellar populations in satellite galaxies would require that a higher fraction of stars previously formed in the outskirts of the progenitors ended up within the tidal debris, or that the MW-M31 interaction occurred at $z>1$.

The James Webb Space Telescope (JWST) will open a new window of the most distant universe and unveil the early growth of supermassive black holes (BHs) in the first galaxies. In preparation for deep JWST imaging surveys, it is crucial to understand the color selection of high-redshift accreting seed BHs. We model the spectral energy distribution of super-Eddington accreting BHs with millions of solar masses in metal-poor galaxies at $z\gtrsim 8$, applying post-process line transfer calculations to radiation hydrodynamical simulation results. Ten kilosecond exposures with the NIRCam and MIRI broad-band filters are sufficient to detect the radiation flux from the seed BHs with bolometric luminosities of $L_{\rm bol}\simeq 10^{45}~{\rm erg~s}^{-1}$. While the continuum colors are similar to those of typical low-$z$ quasars, strong H$\alpha$ line emission with a rest-frame equivalent width ${\rm EW}_{\rm rest}\simeq 1300~\r{A}$ is so prominent that the line flux affects the broad-band colors significantly. The unique colors, for instance F356W$-$F560W $\gtrsim 1$ at $7<z<8$ and F444W$-$F770W $\gtrsim 1$ at $9<z<12$, provide robust criteria for photometric selection of the rapidly growing seed BHs. Moreover, NIRSpec observations of low-ionization emission lines can test whether the BH is fed via a dense accretion disk at super-Eddington rates.

The discovery and characterization of Earth-sized planets that are in, or near, a tidally-locked state are of crucial importance to understanding terrestrial planet evolution, and for which Venus is a clear analog. Exoplanetary science lies at the threshold of characterizing hundreds of terrestrial planetary atmospheres, thereby providing a statistical sample far greater than the limited inventory of terrestrial planetary atmospheres within the Solar System. However, the model-based approach for characterizing exoplanet atmospheres relies on Solar System data, resulting in our limited inventory being both foundational and critical atmospheric laboratories. Present terrestrial exoplanet demographics are heavily biased toward short-period planets, many of which are expected to be tidally locked, and also potentially runaway greenhouse candidates, similar to Venus. Here we describe the rise in the terrestrial exoplanet population and the study of tidal locking on climate simulations. These exoplanet studies are placed within the context of Venus, a local example of an Earth-sized, asynchronous rotator that is near the tidal locking limit. We describe the recent lessons learned regarding the dynamics of the Venusian atmosphere and how those lessons pertain to the evolution of our sibling planet. We discuss the implications of these lessons for exoplanet atmospheres, and outline the need for a full characterization of the Venusian climate in order to achieve a full and robust interpretation of terrestrial planetary atmospheres.

While emission-selected galaxy surveys are biased towards the most luminous part of the galaxy population, absorption selection is a potentially unbiased galaxy selection technique with respect to luminosity. However, the physical properties of absorption-selected galaxies are not well characterised. Here we study the excitation conditions in the interstellar medium (ISM) in damped Ly$\alpha$ (DLA) absorption-selected galaxies. We present a study of the CO spectral line energy distribution (SLED) in four high-metallicity absorption-selected galaxies with previously reported CO detections at intermediate ($z \sim 0.7$) and high ($z \sim 2$) redshifts. We find further evidence for a wide variety of ISM conditions in these galaxies. Two out of the four galaxies show CO SLEDs consistent with that of the Milky Way inner disk. Interestingly, one of these galaxies is at $z \sim 2$ and has a CO SLED below that of main-sequence galaxies at similar redshifts. The other two galaxies at $z>2$ show more excited ISM conditions, with one of them showing thermal excitation of the mid-$J$ (J$=3, 4$) levels, similar to that seen in two massive main-sequence galaxies at these redshifts. Overall, we find that absorption selection traces a diverse population of galaxies.

Massive protostars attain high luminosities as they are actively accreting and the radiation pressure exerted on the gas in the star's atmosphere may launch isotropic high-velocity ($v_{\rm w} \gtrsim 10^3$ km/s) winds. These winds will collide with the surrounding gas producing shock-heated ($T\sim 10^7$ K) tenuous gas that adiabatically expands and pushes on the dense gas that may otherwise be accreted. We present a series of 3D radiation-magnetohydrodynamic simulations of the collapse of massive prestellar cores and include radiative feedback from the direct stellar and dust-reprocessed radiation fields, collimated outflows, and, for the first time, isotropic stellar winds to model how these processes affect the formation of massive (proto)stars. We find that winds are initially launched when the massive protostar is still accreting and the wind properties evolve as the star contracts to the main sequence. Wind feedback drives asymmetric adiabatic wind bubbles that have a bipolar morphology because the dense circumstellar material pinches the expansion of the hot shock-heated gas, which preferentially expands along low-density channels. We term this the "wind tunnel effect." For unmagnetized cores, we find that wind feedback eventually quenches accretion onto massive stars. For magnetized cores, we find that wind feedback is less efficient at halting the accretion flow initially because magnetic tension delays the growth of the wind-driven bubbles. Once winds become strong enough, wind feedback launches adiabatic wind bubbles that eventually reduce accretion. Additionally, we discuss the implications of observing adiabatic wind bubbles with Chandra while the massive protostars are still highly embedded.

It is well established that magnetars are neutron stars with extreme magnetic fields and young ages, but the evolutionary pathways to their creation are still uncertain. Since most massive stars are in binaries, if magnetars are a frequent result of core-collapse supernovae, some fraction are expected to have a bound companion at the time of observation. In this paper, we utilise literature constraints, including deep Hubble Space Telescope imaging, to search for bound stellar companions to magnetars. The magnitude and colour measurements are interpreted in the context of binary population synthesis predictions. We find two candidates for stellar companions associated with CXOU J171405.7-381031 and SGR 0755-2933, based on their J-H colours and H-band absolute magnitudes. Overall, the proportion of the Galactic magnetar population with a plausibly stellar near-infrared counterpart candidate, based on their magnitudes and colours, is between 5 and 10 per cent. This is consistent with a population synthesis prediction of 5 per cent, for the fraction of core-collapse neutron stars arising from primaries which remain bound to their companion after the supernova. These results are therefore consistent with magnetars being drawn in an unbiased way from the natal core-collapse neutron star population, but some contribution from alternative progenitor channels cannot be ruled out.

(ABRIDGED) We use the 17th data release of the second phase of the Apache Point Observatory Galactic Evolution Experiment (APOGEE-2) to provide a homogenous census of N-rich red giant stars across the Milky Way (MW). We report a total of 149 newly identified N-rich field giants toward the bulge, metal-poor disk, and halo of our Galaxy. They exhibit significant enrichment in their nitrogen abundance ratios ([N/Fe] $\gtrsim+0.5$), along with simultaneous depletions in their [C/Fe] abundance ratios ([C/Fe] $< +0.15$), and they cover a wide range of metallicities ($-1.8 < $ [Fe/H] $ <-0.7$). The final sample of candidate N-rich red giant stars with globular-cluster-like (GC-like) abundance patterns from the APOGEE survey includes a grand total of $\sim$ 412 unique objects. These strongly N-enhanced stars are speculated to have been stripped from GCs based on their chemical similarities with these systems. Even though we have not found any strong evidence for binary companions or signatures of pulsating variability yet, we cannot rule out the possibility that some of these objects were members of binary systems in the past and/or are currently part of a variable system. In particular, the fact that we identify such stars among the field stars in our Galaxy provides strong evidence that the nucleosynthetic process(es) producing the anomalous [N/Fe] abundance ratios occurs over a wide range of metallicities. This may provide evidence either for or against the uniqueness of the progenitor stars to GCs and/or the existence of chemical anomalies associated with likely tidally shredded clusters in massive dwarf galaxies such as "Kraken/Koala," \textit{Gaia}-Enceladus-Sausage, among others, before or during their accretion by the MW. A dynamical analysis reveals that the newly identified N-rich stars exhibit a wide range of dynamical characteristics throughout the MW, ...

We present detailed elemental abundances and radial velocities of stars in the metal-poor globular cluster (GC) NGC 2298, based on near-infrared high-resolution ($R\sim$ 22,500) spectra of twelve members obtained during the second phase of the Apache Point Observatory Galactic Evolution Experiment (APOGEE-2) at Las Campanas Observatory as part of the seventeenth Data Release (DR 17) of the Sloan Digital Sky Survey IV (SDSS-IV). We employ the Brussels Automatic Code for Characterizing High accuracy Spectra (\texttt{BACCHUS}) software to investigate abundances for a variety of species including $\alpha$-elements (Mg, Si, and Ca), the odd-Z element Al, and iron-peak elements (Fe and Ni) located in the innermost regions of NGC 2298. We find a mean and median metallicity [Fe/H] $ = -1.76$ and $-1.75$, respectively, with a star-to-star spread of 0.14 dex, compatible with the internal measurement errors. Thus, we find no evidence for an intrinsic Fe abundance spread in NGC 2298. The typical $\alpha-$element enrichment in NGC 2298 is overabundant relative to the Sun, and follows the trend of other metal-poor GCs. We confirm the existence of an Al-enhanced population in this cluster, which is clearly anti-correlated with Mg, indicating the prevalence of the multiple-population phenomenon in NGC 2298.

Photoevaporative winds are a promising mechanism for dispersing protoplanetary discs, but so far theoretical models have been unable to agree on the relative roles that the X-ray, Extreme Ultraviolet or Far Ultraviolet play in driving the winds. This has been attributed to a variety of methodological differences between studies, including their approach to radiative transfer and thermal balance, the choice of irradiating spectrum employed, and the processes available to cool the gas. We use the \textsc{mocassin} radiative transfer code to simulate wind heating for a variety of spectra on a static density grid taken from simulations of an EUV-driven wind. We explore the impact of choosing a single representative X-ray frequency on their ability to drive a wind by measuring the maximum heated column as a function of photon energy. We demonstrate that for reasonable luminosities and spectra, the most effective energies are at a few $100~\mathrm{eV}$, firmly in the softer regions of the X-ray spectrum, while X-rays with energies $\sim1000~\mathrm{eV}$ interact too weakly with disc gas to provide sufficient heating to drive a wind. We develop a simple model to explain these findings. We argue that further increases in the cooling above our models - for example due to molecular rovibrational lines - may further restrict the heating to the softer energies but are unlikely to prevent X-ray heated winds from launching entirely; increasing the X-ray luminosity has the opposite effect. The various results of photoevaporative wind models should therefore be understood in terms of the choice of irradiating spectrum.

Samples of young type Ia supernovae have shown `early excess' emission in a few cases. Similar excesses are predicted by some explosion and progenitor scenarios and hence can provide important clues regarding the origin of thermonuclear supernovae. They are however, only predicted to last up to the first few days following explosion. It is therefore unclear whether such scenarios are intrinsically rare or if the relatively small sample size simply reflects the difficulty in obtaining sufficiently early detections. To that end, we perform toy simulations covering a range of survey depths and cadences, and investigate the efficiency with which young type Ia supernovae are recovered. As input for our simulations, we use models that broadly cover the range of predicted luminosities. Based on our simulations, we find that in a typical three day cadence survey, only $\sim$10% of type Ia supernovae would be detected early enough to rule out the presence of an excess. A two day cadence however, should see this increase to $\sim$15%. We find comparable results from more detailed simulations of the Zwicky Transient Facility surveys. Using the recovery efficiencies from these detailed simulations, we investigate the number of young type Ia supernovae expected to be discovered assuming some fraction of the population come from scenarios producing an excess at early times. Comparing the results of our simulations to observations, we find the intrinsic fraction of type Ia supernovae with early flux excesses is $\sim28^{+13}_{-11}%$%.

Type IIn supernovae (SNe\,IIn) are an uncommon and highly heterogeneous class of SN where the SN ejecta interact with pre-existing circumstellar media (CSM). Previous studies have found a mass ladder in terms of the association of the SN location with H$\alpha$ emission and the progenitor masses of SN classes. In this paper, we present the largest environmental study of SNe\,IIn. We analyse the H$\alpha$ environments of 77 type IIn supernovae using continuum subtracted H$\alpha$ images. We use the pixel statistics technique, normalised cumulative ranking (NCR), to associate SN pixels with H$\alpha$ emission. We find that our 77 SNe\,IIn do not follow the H$\alpha$ emission. This is not consistent with the proposed progenitors of SNe\,IIn, luminous blue variables (LBVs) as LBVs are high mass stars that undergo dramatic episodic mass loss. However, a subset of the NCR values follow the H$\alpha$ emission, suggesting a population of high mass progenitors. This suggests there may be multiple progenitor paths with $\sim$60\% having non-zero NCR values with a distribution consistent with high mass progenitors such as LBVs and $\sim$40\% of these SNe not being associated with H$\alpha$ emission. We discuss the possible progenitor routes of SNe\,IIn, especially for the zero NCR value population. We also investigate the radial distribution of the SNe in their hosts in terms of H$\alpha$ and $r'$-band flux.

From a sample of 109 candidate Ultra-Strong Mg II (USMgII; having rest equivalent width of Mg II absorption, $W_{2796}>3.0$ Angstrom) systems at z=0.4-0.6, we confirm 27 and identify host galaxies of 20 systems based on associated nebular line emission from our SALT observations or from SDSS fiber spectra. The measured impact parameter, [O II] luminosity, star formation rate, B-band luminosity and stellar mass are in the ranges $7.3\le D[kpc]\le79$, $0.2\le L_{[O II]}[ 10^{41}~erg s^{-1}]$ $\le 4.5$, $2.59\le SFR[M_\odot yr^{-1} ]\le 33.51$, $0.15L_B^*\le L_B\le1.63L_B^*$ and $10.21\le log[M_*/M_\odot]\le11.62$ respectively. The impact parameters found are larger than that predicted by the $W_{2796}$ vs D relationship of the general population of Mg II absorbers. At a given D, USMgII host galaxies are more luminous and massive compared to typical Mg II absorbers. However, the measured SFRs are slightly lower than that of main-sequence galaxies with the same M$_\star$ at $z\sim0.5$. We report a correlation between $L_{[O II]}$ and W$_{2796}$ for the full population of Mg II absorbers, driven mainly by the host galaxies of weak Mg II absorbers that tend to have low $L_{[O II]}$ and large impact parameters. We find at least $\sim$33% of the USMgII host galaxies (with a limiting magnitude of $m_r<23.6$) are isolated and the large $W_{2796}$ in these cases may originate from gas flows (infall/outflow) in single halos of massive but not starburst galaxies. We also find galaxy interactions could be responsible for large velocity widths in at least $\sim$17% cases.

We present a novel application of the extended Fast Action Minimization method (eFAM) aimed at assessing the role of the environment in shaping galaxy evolution. We validate our approach by testing eFAM predictions against the Magneticum hydrodynamical simulation. We consider the z~0 snapshot of the simulation as our observed catalogue and use the reconstructed trajectories of galaxies to model the evolution of cosmic structures. At the statistical level, the fraction of volume (VFF) occupied by voids, sheets, filaments, and clusters in the reconstructed catalogues agrees within $1\sigma$ with the VFF estimated from the high-redshift snapshots of the simulation. The local accuracy of eFAM structures is evaluated by computing their purity with respect to the simulated catalogues, P, at the cells of a regular grid. Up to z=1.2, clusters have 0.58<P<0.93, filaments vary in 0.90<P<0.99, sheets show 0.78<P<0.92, and voids are best identified with 0.90<P<0.92. As redshift increases, comparing reconstructed tracers and simulated galaxies becomes more difficult due to their different biases and number densities and the purity decreases to P~0.6. We retrieve the environmental history of individual galaxies by tracing their trajectories through the cosmic web and relate their observed gas fraction, $f_\mathrm{gas}$, with the time spent within different structures. For galaxies in clusters and filaments, eFAM reproduces the variation of $f_\mathrm{gas}$ as a function of the redshift of accretion/infall as traced by the simulations with a 1.5 $\sigma$ statistical agreement (which decreases to 2.5 $\sigma$ statistical agreement for low-mass galaxies in filaments). These results support the application of eFAM to observational data to study the environmental dependence of observed galaxy properties, offering a complementary approach to that based on light-cone observations.

We study the low redshift Lyman-$\alpha$ Forest in the Illustris and IllustrisTNG (TNG) cosmological simulations to demonstrate their utility in constraining aspects of sub-grid models of feedback from active galactic nuclei (AGN). The two simulations share an identical Ultraviolet Background prescription and similar cosmological parameters, but TNG features an entirely reworked AGN feedback model. Therefore a comparison of these simulations is useful to assess the effects of an altered AGN sub-grid model on the low redshift Lyman-$\alpha$ Forest. We find significant differences in the IGM temperature-density relation between the two simulations due to changes in the gas heating rate due to AGN. We investigate Lyman-$\alpha$ Forest observables such as the column density distribution function, flux PDF, and Doppler width ($b$-parameter) distribution. Due to the AGN radio mode model, the original Illustris simulations have a factor of 2-3 fewer absorbers than TNG at column densities $N_{\rm HI}< 10^{15.5}$ cm$^{-2}$. We show that TNG is in much better agreement with the observed $z=0.1$ flux power spectrum than Illustris. The differences in the amplitude and shape of the flux PDF and power spectrum between Illustris and TNG cannot be attributed to simple changes in the photoheating rate. We also compare the simulated Forest statistics to UV data from the Cosmic Origins Spectrograph (COS) and find that neither simulation can reproduce the slope of the absorber distribution. Both Illustris and TNG also produce significantly smaller $b$-parameter distributions than observed in the COS data, possibly due to unresolved or missing sources of turbulence.

A broad class of dark energy models can be written in the form of k-essence, whose Lagrangian density is a two-variable function of a scalar field $\phi$ and its kinetic energy $X\equiv \frac{1}{2}\partial^\mu\phi \partial_\mu\phi$. In the thawing scenario, the scalar field becomes dynamic only when the Hubble friction drops below its mass scale in the late universe. Thawing k-essence dark energy models can be randomly sampled by generating the Taylor expansion coefficients of its Lagrangian density from random matrices \cite{thaws}. Ref. \cite{thaws} points out that the non-uniform distribution of effective equation of state parameters $(w_0, w_a)$ of thawing k-essence model can be used to improve the statistics of model selection. The present work studies the statistics of thawing k-essence in a more general framework that is Parameterized by the Age of the universe (PAge) \cite{PAge}. For fixed matter fraction $\Omega_m$, the random thawing k-essence models cluster in a narrow band in the PAge parameter space, providing a strong theoretical prior. We simulate cosmic shear power spectrum data for the Chinese Space Station Telescope optical survey, and compare the fisher forecast with and without the theoretical prior of thawing k-essence. For an optimal tomography binning scheme, the theoretical prior improves the figure of merit in PAge space by a factor of $3.3$.

Comet 156P/Russell-LINEAR is a short period Jupiter family comet with an orbital period of 6.44 years. The results from spectroscopic, photometric, polarimetric observations and dust modelling studies are presented here. From the spectroscopic study, strong emissions from $CN (\Delta \nu = 0)$, $C_3 (\lambda 4050$ \AA), $C_2 (\Delta \nu = +1)$ and $C_2 (\Delta \nu = 0)$ can be observed during both the epochs of our observations. The Q($C_2$)/Q(CN) ratio classifies the comet as a typical comet. The imaging data reveals the presence of jets. The dust emission from the comet is observed to have a non-steady state outflow due to the presence of these strong jets which subside in later epochs, resulting in a steady state outflow. Polarimetric study at two different phase angles reveals the degree of polarization to be comparable to Jupiter family comets at similar phase angles. Localized variations in polarization values are observed in the coma. The dust modelling studies suggest the presence of high amount of silicate/low absorbing material and indicate the coma to be dominated by higher amount of large size grains with low porosity having power law size distribution index = 2.4. The observed activity and dust properties points to a similarity to another Jupiter family comet, 67P/Churyumov-Gerasimenko.

The winds observed around asymptotic giant branch (AGB) stars are generally attributed to radiation pressure on dust, which is formed in the extended dynamical atmospheres of these pulsating, strongly convective stars. Current radiation-hydrodynamical models can explain many of the observed features, and they are on the brink of delivering a predictive theory of mass loss. This review summarizes recent results and ongoing work on winds of AGB stars, discussing critical ingredients of the driving mechanism, and first results of global 3D RHD star-and-wind-in-a-box simulations. With such models it becomes possible to follow the flow of matter, in full 3D geometry, all the way from the turbulent, pulsating interior of an AGB star, through its atmosphere and dust formation zone into the region where the wind is accelerated by radiation pressure on dust. Advanced instruments, which can resolve the stellar atmospheres, where the winds originate, provide essential data for testing the models.

The prompt emission of Gamma Ray Bursts (GRBs) is still an outstanding question in the study of these cataclysmic events. Part of what makes GRBs difficult to study is how unique each event seems to be. However, aggregating many GRB observations and analyzing the population allows us to obtain a better understanding of the emission mechanism that produces the observed prompt emission. In this review, we outline some of the most prevalent correlations that have emerged from GRB prompt emission observations and how these correlations are interpreted in relation to GRB physical properties and prompt emission models.

The mean plane-of-sky magnetic field strength is traditionally obtained from the combination of polarization and spectroscopic data using the Davis-Chandrasekhar-Fermi (DCF) technique. However, we identify the major problem of the DCF to be its disregard of the anisotropic character of MHD turbulence. On the basis of the modern MHD turbulence theory we introduce a new way of obtaining magnetic field strength from observations. Unlike the DCF, the new technique uses not the dispersion of the polarization angle and line of sight velocities, but increments of these quantities given by the structure functions. To address the variety of the astrophysical conditions for which our technique can be applied, we consider the turbulence in both media with magnetic pressure larger than the gas pressure corresponding e.g. to molecular and the gas pressure larger than the magnetic pressure corresponding to the warm neutral medium. We provide general expressions for arbitrary admixture of Alfv\'en, slow and fast modes in these media and consider in detail the particular cases relevant to diffuse media and molecular clouds. We successfully test our results using synthetic observations obtained from MHD turbulence simulations. We demonstrate that our Differential Measure Approach (DMA), unlike the DCF, can be used to measure the distribution of magnetic field strengths, can provide magnetic field measurements with limited data and is much more stable in the presence of large scale variations induces of non-turbulent nature. In parallel, our study uncover the deficiencies of the earlier DCF research.

SGR J1935+2154 was discovered in 2016 and is currently one of the most burst-active Soft Gamma-ray Repeaters (SGR), having emitted several X-ray bursts in recent years. In one of our previous articles, we investigated the contribution to high-energy and very high-energy gamma-ray emission (VHE, $E > 100$ GeV) due to cosmic-ray acceleration of SNR G57.2+0.8 hosting SGR J1935+2154 using the GALPROP propagation code. However, follow-up observations of SGR 1935+2154 were made for 2 hours on April 28, 2020, using the High Energy Stereoscopic System (H.E.S.S.). The observations coincide with X-ray bursts detected by INTEGRAL and Fermi/Gamma-ray Burst Monitor (GBM). These are the first high-energy gamma-ray observations of an SGR in a flaring state, and upper limits on sustained and transient emission have been derived. Now that new H.E.S.S. observations have been made, it is interesting to update our model with respect to these new upper limits. We extend our previous results to a more general situation using the new version of GALPROP. We obtain a hadronic model that confirms the results discussed by H.E.S.S.. This leads to an optimistic prospect that cosmic ray gamma rays from SGR J1935+2154 can contribute to the overall gamma energy density distribution and in particular to the diffusion gamma rays from the Galactic center.

We present the discovery of 34 comoving systems containing an ultra-cool dwarf found by means of the NOIRLab Source Catalog (NSC) DR2. NSC's angular resolution of $\sim$1" allows for the detection of small separation binaries with significant proper motions. We used the catalog's accurate proper motion measurements to identify the companions by cross-matching a previously compiled list of brown dwarf candidates with NSC DR2. The comoving pairs consist of either a very low-mass star and an ultra-cool companion, or a white dwarf and an ultra-cool companion. The estimated spectral types of the primaries are in the K and M dwarf regimes, those of the secondaries in the M, L and T dwarf regimes. We calculated angular separations between $\sim$2 and $\sim$56", parallactic distances between $\sim$43 and $\sim$261 pc and projected physical separations between $\sim$169 and $\sim$8487 AU. The lowest measured total proper motion is 97 mas yr$^{-1}$, the highest 314 mas yr$^{-1}$. Tangential velocities range from $\sim$23 to $\sim$187 km s$^{-1}$. We also determined comoving probabilities, estimated mass ratios and calculated binding energies for each system. We found no indication of possible binarity for any component of the 34 systems in the published literature. The discovered systems can contribute to the further study of the formation and evolution of low-mass systems as well as to the characterization of cool substellar objects.

We use time-resolved spectra from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) to examine the distribution of radial velocity (RV) variations in 249 stars identified as members of the Sagittarius (Sgr) dwarf spheroidal (dSph) galaxy by Hayes et al (2020). We select Milky Way (MW) stars that have stellar parameters ($log(g)$, $T_{eff}$, and $[Fe/H]$) similar to those of the Sagittarius members by means of a k-d tree of dimension 3. We find that the shape of the distribution of RV shifts in Sgr dSph stars is similar to that measured in their MW analogs, but the total fraction of RV variable stars in the Sgr dSph is larger by a factor of $\sim 2$. After ruling out other explanations for this difference, we conclude that the fraction of close binaries in the Sgr dSph is intrinsically higher than in the MW. We discuss the implications of this result for the physical processes leading to the formation of close binaries in dwarf spheroidal and spiral galaxies.

The classical Cepheid eta Aql was not included in past Leavitt Law work (Benedict et al. 2007) because of a presumed complicating orbit due to a known B9.8V companion. To determine the orbit of eta Aql B, we analyze a significant number of radial velocity measures (RV) from eight sources. With these we establish the RV variation due to Cepheid pulsation, using a twelve Fourier coefficient model, while solving for velocity offsets required to bring the RV data sets into coincidence. RV residuals provide no evidence of orbital motion, suggesting either nearly face-on orientation or very long period. Reanalysis of Hubble Space Telescope Fine Guidance Sensor astrometry now includes reference star parallax and proper motion priors from Gaia EDR3. As modeling confirmation, we reanalyze zeta Gem in parallel, deriving zeta Gem parallax and proper motion values consistent with Gaia EDR3, and consistent with the Benedict 2007 Leavitt Law. In an effort to further characterize eta Aql B, we hypothesize that eta Aql residuals larger than those of the associated reference stars or a parallax inconsistent with EDR3 and the Benedict 2007 Leavitt Law indicate unmodeled orbital motion. Using the astrometric noise or parallax mismatch with EDR3 we estimate possible periods and mass for eta Aql B. Ascribing photocenter motion to the photometric variation of the Cepheid, eta Aql A, yields a plausible separation, consistent with a long period, explaining the lack of RV variation. None of these approaches yields an unassailable characterization of the eta Aql A-B system

X-Calibur is a balloon-borne telescope that measures the polarization of high-energy X-rays in the 15--50keV energy range. The instrument makes use of the fact that X-rays scatter preferentially perpendicular to the polarization direction. A beryllium scattering element surrounded by pixellated CZT detectors is located at the focal point of the InFOC{\mu}S hard X-ray mirror. The instrument was launched for a long-duration balloon (LDB) flight from McMurdo (Antarctica) on December 29, 2018, and obtained the first constraints of the hard X-ray polarization of an accretion-powered pulsar. Here, we describe the characterization and calibration of the instrument on the ground and its performance during the flight, as well as simulations of particle backgrounds and a comparison to measured rates. The pointing system and polarimeter achieved the excellent projected performance. The energy detection threshold for the anticoincidence system was found to be higher than expected and it exhibited unanticipated dead time. Both issues will be remedied for future flights. Overall, the mission performance was nominal, and results will inform the design of the follow-up mission XL-Calibur, which is scheduled to be launched in summer 2022.

A Kerr black hole (BH) surrounded by a neutrino-dominated accretion flow (NDAF) is one of plausible candidates of the central engine in gamma-ray bursts. The accretion material might inherit and restructure strong magnetic fields from the compact object mergers or massive collapsars. The magnetic coupling (MC) process between a rapid rotating BH and an accretion disc is one of possible magnetic configurations that transfers the energy and angular momentum from the BH to the disc. In this paper, we investigate one-dimensional global solutions of NDAFs with MC (MCNDAFs), taking into account general relativistic effects, detailed neutrino physics, different MC geometries, and reasonable nucleosynthesis processes. Six cases with different accretion rates and power-law indices of magnetic fields are presented and compared with NDAFs without MC. Our results indict that the MC process can prominently impact the structure, thermal properties, and microphysics of MCNDAFs, increase luminosities of neutrinos and their annihilations, result in the changing of radial distributions of nucleons, and push the region of heavy nuclei synthesis to a larger radius than counterparts in NDAFs.

In this letter we report observations of magnetic switchback (SB) features near 1 au using data from the \emph{Wind} spacecraft. These features appear to be strikingly similar to the ones observed by the Parker Solar Probe mission (PSP) closer to the Sun: namely, one-sided spikes (or enhancements) in the solar-wind bulk speed $V$ that correlate/anti-correlate with the spikes seen in the radial-field component $B_R$. In the solar-wind streams that we analyzed, these specific SB features near 1 au are associated with large-amplitude Alfv\'enic oscillations that propagate outward from the sun along a local background (prevalent) magnetic field $\bf{B}_0$ that is nearly radial. We also show that, when $\bf{B}_0$ is nearly perpendicular to the radial direction, the large amplitude Alfv\'enic oscillations display variations in $V$ that are two-sided (i.e., $V$ alternately increases and decreases depending on the vector $\Delta\bf{B}=\bf{B} - \bf{B}_0$). As a consequence, SBs may not appear always as one-sided spikes in $V$, especially at larger heliocentric distances where the local background field statistically departs from the radial direction. We suggest that SBs can be well described by large-amplitude Alfv\'enic fluctuations if the field rotation is computed with respect to a well-determined local background field that, in some cases, may deviate from the large-scale Parker field.

With the upcoming Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST), it is expected that only $\sim 0.1\%$ of all transients will be classified spectroscopically. To conduct studies of rare transients, such as Type I superluminous supernovae (SLSNe), we must instead rely on photometric classification. In this vein, here we carry out a pilot study of SLSNe from the Pan-STARRS1 Medium-Deep Survey (PS1-MDS) classified photometrically with our SuperRAENN and Superphot algorithms. We first construct a sub-sample of the photometric sample using a list of simple selection metrics designed to minimize contamination and ensure sufficient data quality for modeling. We then fit the multi-band light curves with a magnetar spin-down model using the Modular Open-Source Fitter for Transients (MOSFiT). Comparing the magnetar engine and ejecta parameter distributions of the photometric sample to those of the PS1-MDS spectroscopic sample and a larger literature spectroscopic sample, we find that these samples are overall consistent, but that the photometric sample extends to slower spins and lower ejecta masses, which correspond to lower luminosity events, as expected for photometric selection. While our PS1-MDS photometric sample is still smaller than the overall SLSN spectroscopic sample, our methodology paves the way to an orders-of-magnitude increase in the SLSN sample in the LSST era through photometric selection and study.

In 2018, we reported our discovery of a dozen quiescent X-ray binaries in the central parsec (pc) of the Galaxy (Hailey et al. 2018). In a recent follow-up paper (Mori et al. 2021), we published an extended analysis of these sources and other X-ray binaries (XRBs) in the central pc and beyond, showing that most if not all of the 12 non-thermal sources are likely black hole low-mass X-ray binary (BH-LMXB) candidates. In response, Maccarone et al. 2022 (TM22 hereafter) argued, primarily on the claim that neutron star low-mass X-ray binaries (NS-LMXBs) often do not have short outburst recurrence times (<~ 10 yr), that they cannot be excluded as a designation for the 12 quiescent X-ray binary sources. TM22 cites three main factors in their study: (1) X-ray outburst data of NS transients detected by RXTE and MAXI, (2) the Galactic population of NS-LMXBs, and (3) (persistently) quiescent NS-LMXBs in globular clusters. We address these arguments of TM22 and correct their misunderstandings of our work and the literature, even though most of these points have already been thoroughly addressed by Mori et al. 2021. We also correct TM22's assertion that our arguments are based solely on NS transients' recurrence times.

In high-contrast imaging optical systems for direct observation of planets outside our solar system, adaptive optics with an accuracy of lambda/10,000 root mean square is required to reduce the speckle noise down to 1e-10 level in addition to the nulling coronagraph which eliminate the diffracted light. We developed the speckle area nulling (SAN) method as a new dark-hole control algorithm which is capable of controlling speckle electric field in a wide area quickly, in spite of an extension of speckle nulling, and is robust not relying upon an optical model. We conducted a validation experiment for the SAN method with a monochromatic light and succeeded in reducing the intensity of areal speckles by 4.4e-2.

Investigating the heliospheric evolution and consequences of Coronal mass ejections (CMEs) is critical to understanding the solar-terrestrial relationship. For the first time, Heliospheric Imagers (HIs) onboard STEREO, providing multiple views of CMEs in the heliosphere, observed the vast and crucial observational gap between the Sun and the Earth. Using J-maps constructed from coronagraphs (CORs) and HIs observations, we continuously tracked different density enhanced features of CMEs. We implemented several reconstruction methods to estimate the three-dimensional (3D) kinematics of CMEs during their evolution from the Sun to Earth. Our study provides evidence that the 3D speeds of CMEs near the Sun are not reasonably sufficient for understanding the propagation and accurate forecasting of the arrival time at the Earth of a majority of CMEs. This finding can be due to many factors that significantly change the CME kinematics beyond the COR field of view, such as the interaction/collision of two or more CMEs or the interaction of CMEs with the ambient solar wind medium. We attempted to understand the evolution and consequences of the interacting/colliding CMEs in the heliosphere using STEREO/HI, WIND, and ACE observations. The study found a significant change in the dynamics of the CMEs after their collision and interaction. The in situ observations show the signatures of CME-CME interaction as heating and compression, formation of magnetic holes (MHs), and interaction region (IR). We also noticed that long-lasting IR, formed at the rear edge of preceding CME, is responsible for large geomagnetic perturbations. Our study highlights the significance of using HIs observations in studying heliospheric evolution of CMEs, CME-CME collision, identifying and associating the three-part structure of CMEs in their remote and in situ observations, and hence for improved space weather forecasting.

We discuss non-linear excitation and amplitude saturation of $g$-modes, $r$-modes and overstable convective (OsC) modes in early type main sequence stars, taking account of the effects of three-mode couplings on amplitude evolutions. OsC modes are rotationally stabilized convective modes in the convective core and they resonantly excite low frequency $g$-modes to obtain large amplitudes in the envelope when the rotation rate of the core is larger than critical rates. We use, for a network of three-mode couplings, amplitude equations governing the time evolution of the mode amplitudes where each of three-mode couplings is assumed to occur between two stable modes and one unstable mode. Assuming that the unstable modes in the couplings are OsC modes in the core and the stable modes are $g$- and $r$-modes in the envelope, we integrate the amplitude equations to see how the $g$- and $r$-modes are non-linearly excited by the OsC modes and whether or not the amplitude evolutions tend toward a state of finite amplitudes. We find that the non-linear three-mode couplings do excite low frequency $g$- and $r$-modes but they are not necessarily effective to achieve amplitude saturation since the three-mode couplings between the OsC modes with large growth rates and $g$- and $r$-modes with small damping rates tend to destabilize amplitude evolutions.

We have analyzed Atacama Large Millimeter/submillimeter Array Band 6 data of the hyper-compact H$_{\rm {II}}$ region G24.78+0.08 A1 (G24 HC H$_{\rm {II}}$) and report the detection of vibrationally-excited lines of HC$_{3}$N ($v_{7}=2$, $J=24-23$). The spatial distribution and kinematics of a vibrationally-excited line of HC$_{3}$N ($v_{7}=2$, $J=24-23$, $l=2e$) are found to be similar to the CH$_{3}$CN vibrationally-excited line ($v_{8}=1$), which indicates that the HC$_{3}$N emission is tracing the disk around the G24 HC H$_{\rm {II}}$ region previously identified by the CH$_{3}$CN lines. We derive the $^{13}$CH$_{3}$CN/HC$^{13}$CCN abundance ratios around G24 and compare them to the CH$_{3}$CN/HC$_{3}$N abundance ratios in disks around Herbig Ae and T Tauri stars. The $^{13}$CH$_{3}$CN/HC$^{13}$CCN ratios around G24 ($\sim 3.0-3.5$) are higher than the CH$_{3}$CN/HC$_{3}$N ratios in the other disks ($\sim 0.03-0.11$) by more than one order of magnitude. The higher CH$_{3}$CN/HC$_{3}$N ratios around G24 suggest that the thermal desorption of CH$_{3}$CN in the hot dense gas and efficient destruction of HC$_{3}$N in the region irradiated by the strong UV radiation are occurring. Our results indicate that the vibrationally-excited HC$_{3}$N lines can be used as a disk tracer of massive protostars at the HC H$_{\rm {II}}$ region stage, and the combination of these nitrile species will provide information of not only chemistry but also physical conditions of the disk structures.

Previously, we modelled the X-ray spectra of the narrow-line Seyfert 1 galaxy IRAS 13224$-$3809 using a disc reflection model with a fixed electron density of $10^{15}$ cm$^{-3}$. An additional blackbody component was required to fit the soft X-ray excess below 2 keV. In this work, we analyse simultaneously five flux-resolved XMM-Newton spectra of this source comprising data collected over 2 Ms. A disc reflection model with an electron density of $n_{\rm e}\approx10^{20}$ cm$^{-3}$ and an iron abundance of $Z_{\rm Fe}=3.2\pm0.5Z_{\odot}$ is used to fit the broad-band spectra of this source. No additional component is required to fit the soft excess. Our best-fit model provides consistent measurements of black hole spin and disc inclination angle as in previous models where a low disc density was assumed. In the end, we calculate the average illumination distance between the corona and the reflection region in the disc of IRAS 13224$-$3809 based on best-fit density and ionisation parameters, which changes from 0.43$\sqrt{f_{\rm AD}/f_{\rm INF}}$ $r_{\rm g}$ in the lowest flux state to 1.71$\sqrt{f_{\rm AD}/f_{\rm INF}}$ $r_{\rm g}$ in the highest flux state assuming a black hole mass of $2\times10^{6}M_{\odot}$. $f_{\rm AD}/f_{\rm INF}$ is the ratio between the flux of the coronal emission that reaches the accretion disc and infinity. This ratio depends on the geometry of the coronal region in IRAS 13224$-$3809. So we only discuss its value based on the simple `lamp-post' model, although detailed modelling of the disc emissivity profile of IRAS 13224$-$3809 is required in future to reveal the exact geometry of the corona.

The detection of a branched alkyl molecule in the high-mass star forming protocluster Sgr B2(N) permitted by the advent of ALMA revealed a new dimension of interstellar chemistry. Astrochemical simulations subsequently predicted that beyond a certain degree of molecular complexity, branched molecules could even dominate over their straight-chain isomers. More generally, we aim at probing further the presence in the ISM of complex organic molecules with the capacity to exhibit both a normal and iso form, via the attachment of a functional group to either a primary or secondary carbon atom. We used the imaging spectral line survey survey ReMoCA performed with ALMA and the results of a recent spectroscopic study of propanol to search for the iso and normal isomers of this molecule in the hot molecular core Sgr B2(N2). We expanded the network of the astrochemical model MAGICKAL to explore the formation routes of propanol. We report the first interstellar detection of iso-propanol toward a position of Sgr B2(N2) that shows narrow linewidths. We also report the first secure detection of normal-propanol in a hot core. i-Propanol is found to be nearly as abundant as n-propanol, with an abundance ratio of 0.6 similar to the ratio of 0.4 that we obtained previously for i- and n-propyl cyanide in Sgr B2(N2). The results are in good agreement with the outcomes of our astrochemical models, which indicate that OH-radical addition to propylene in dust-grain ice mantles, driven by water photodissociation, can produce appropriate quantities of n- and i-propanol. The n-to-i ratio in Sgr B2(N2) may be a direct inheritance of the branching ratio of this reaction process. The detection of n- and i-propanol and their ratio indicate that the modest preference toward the normal form of propyl cyanide determined previously may be a more general feature among similarly sized interstellar molecules. [abridged]

Impacts may have had a significant effect on the atmospheric chemistry of the early Earth. Reduced phases in the impactor (e.g., metallic iron) can reduce the planet's H$_2$O inventory to produce massive atmospheres rich in H$_2$. Whilst previous studies have focused on the interactions between the impactor and atmosphere in such scenarios, we investigate two further effects, 1) the distribution of the impactor's iron inventory during impact between the target interior, target atmosphere, and escaping the target, and 2) interactions between the post-impact atmosphere and the impact-generated melt phase. We find that these two effects can potentially counterbalance each other, with the melt-atmosphere interactions acting to restore reducing power to the atmosphere that was initially accreted by the melt phase. For a $\sim10^{22}\,\mathrm{kg}$ impactor, when the iron accreted by the melt phase is fully available to reduce this melt, we find an equilibrium atmosphere with H$_2$ column density $\sim10^4\,\mathrm{moles\,cm^{-2}}$ ($p\mathrm{H2}\sim120\,\mathrm{bars}\mathrm{,}~X_\mathrm{H2}\sim0.77$), consistent with previous estimates. However, when the iron is not available to reduce the melt (e.g., sinking out in large diameter blobs), we find significantly less H$_2$ ($7\times10^2-5\times10^3\,\mathrm{moles\,cm^{-2}}$, $p\mathrm{H2}\lesssim60\,\mathrm{bars}\mathrm{,}~X_\mathrm{H2}\lesssim0.41$). These lower H$_2$ abundances are sufficiently high that species important to prebiotic chemistry can form (e.g., NH3, HCN), but sufficiently low that the greenhouse heating effects associated with highly reducing atmospheres, which are problematic to such chemistry, are suppressed. The manner in which iron is accreted by the impact-generated melt phase is critical in determining the reducing power of the atmosphere and re-solidified melt pool in the aftermath of impact.

We present a novel approach for the detection of events in systems of ordinary differential equations. The new method combines the unique features of Taylor integrators with state-of-the-art polynomial root finding techniques to yield a novel algorithm ensuring strong event detection guarantees at a modest computational overhead. Detailed tests and benchmarks focused on problems in astrodynamics and celestial mechanics (such as collisional N-body systems, spacecraft dynamics around irregular bodies accounting for eclipses, computation of Poincare' sections, etc.) show how our approach is superior in both performance and detection accuracy to strategies commonly employed in modern numerical integration works. The new algorithm is available in our open source Taylor integration package heyoka.

In accelerating and supersonic media, the interaction of photons with spectral lines can be of ultimate importance. However, fully accounting for such line forces currently can only be done by specialised codes in 1-D steady-state flows. More general cases and higher dimensions require alternative approaches. We presented a comprehensive and fast method for computing the radiation line-force using tables of spectral line-strength distribution parameters, which can be applied in arbitrary (multi-D, time-dependent) simulations, including those accounting for the line-deshadowing instability, to compute the appropriate opacities. We assumed local thermodynamic equilibrium to compute a flux-weighted line opacity from $>4$ million spectral lines. We derived the spectral line strength and tabulated the corresponding line-distribution parameters for a range of input densities $\rho\in[10^{-20},10^{-10}]gcm^{-3}$ and temperatures $T\in[10^4,10^{4.7}]K$. We found that the variation of the line distribution parameters plays an essential role in setting the wind dynamics in our models. In our benchmark study, we also found a good overall agreement between the O-star mass-loss rates of our models and those derived from steady-state studies using more detailed radiative transfer. Our models reinforce that self-consistent variation of the line-distribution parameters is important for the dynamics of line-driven flows. Within a well-calibrated O-star regime, our results support the proposed methodology. In practice, utilising the provided tables, yielded a factor $>100$ speed-up in computational time compared to specialised 1-D model-atmosphere codes of line-driven winds, which constitutes an important step towards efficient multi-D simulations. We conclude that our method and tables are ready to be exploited in various radiation-hydrodynamic simulations where the line force is important.

The $\gamma$-ray astronomy in time domain has been by now progressed further as the variabilities of Active Galactic Nuclei (AGNs) on different timescales have been reported a lot. We study the $\gamma$-ray variabilities of 23 jetted AGNs through applying a stochastic process method to the ~12.7 yr long-term light curve (LC) obtained by Fermi-Large Area Telescope (Fermi-LAT). In this method, the stochastically driven damped simple harmonic oscillator (SHO) and the damped random walk (DRW) models are used to model the long-term LCs. Our results show that the long-term variabilities of 23 AGNs can be characterized well by both SHO and DRW models. However, the SHO model is restricted in the over-damped mode and the parameters are poorly constrained. The SHO power spectral densities (PSDs) are same as the typical DRW PSD. In the plot of the rest-frame timescale that corresponds to the broken frequency in the PSD versus black hole mass, the intrinsic $\gamma$-ray characteristic timescales of 23 AGNs occupy almost the same space with the optical variability timescales obtained from the accretion disk emission. This suggests a connection between the jet and the accretion disk. Same as the optical variability of AGN accretion disk, the $\gamma$-ray timescale is also consistent with the thermal timescale caused by the thermal instability in the standard accretion disk of AGN.

Differential imaging is a postprocessing method to obtain high contrast, often used for exoplanet searches. The coherent differential imaging on speckle area nulling (CDI-SAN) method was developed to detect a faint exoplanet lying beneath residual speckles of a host star. It utilizes image acquisitions faster than the stellar speckle variation synchronized with five shapes of a deformable mirror repeatedly. By using the only the integrated values of each of the five images and square differences for a long interval of observations, the light of the exoplanet could be separated from the stellar light. The achievable contrast would reach to almost the photon-noise limit of the residual speckle intensities under appropriate conditions. The CDI-SAN can be applied to both ground-based and space telescopes.

Over the past few years, $\sim$30 extragalactic fast X-ray transients (FXRTs) have been discovered, mainly in Chandra and XMM-Newton data. Their nature remains unclear, with proposed origins including a double neutron star merger, a tidal disruption event involving an intermediate-mass black hole and a white dwarf, or a supernova shock breakout. A decisive differentiation between these three promising mechanisms for their origin requires an understanding of the FXRT energetics, environments, and/or host properties. We present optical observations obtained with the Very Large Telescope for the FXRTs XRT 000519 and XRT 110103 and Gran Telescopio Canarias observations for XRT 000519 designed to search for host galaxies of these FXRTs. In the $g_s$, $r_s$ and $R$-band images, we detect an extended source on the North-West side of the $\sim$ $1^{\prime\prime}$ (68% confidence) error circle of the X-ray position of XRT 000519 with a Kron magnitude of $g_s=$26.29$\pm$0.09 (AB magnitude). We discuss the XRT 000519 association with the probable host candidate for various possible distances, and we conclude that if XRT 000519 is associated with the host candidate a supernova shock breakout scenario is likely excluded. No host galaxy is found near XRT 110103 down to a limiting magnitude of $R>25.8$.

The shell bound by the Karman line at a height of 80 to 100km above the Earth's surface, and Geosynchronous Orbit, at 36,000km, is defined as the orbital space surrounding the Earth. It is within this region, and especially in Low Earth Orbit (LEO), where environmental issues are becoming urgent because of the rapid growth of the anthropogenic space object population, including satellite "mega-constellations". In this Perspective, we summarise the case that the orbital space around the Earth should be considered an additional ecosystem, and so subject to the same care and concerns and the same broad regulations as, for example, the oceans and the atmosphere. We rely on the orbital space environment by looking through it as well as by working within it. Hence, we should consider damage to professional astronomy, public stargazing and the cultural importance of the sky, as well as the sustainability of commercial, civic and military activity in space. Damage to the orbital space environment has problematic features in common with other types of environmental issue. First, the observed and predicted damage is incremental and complex, with many contributors. Second, whether or not space is formally and legally seen as a global commons, the growing commercial exploitation of what may appear a "free" resource is in fact externalising the true costs.

In spectra of the Active Galactic Nuclei (AGNs), the [N II] 6548, 6583 A lines are commonly fitted using the fixed intensity ratio of these two lines (R[N II]=I$_{6583}$/I$_{6548}$). However, the used values for fixed intensity ratio are slightly different through literature. There are several theoretical calculations of the transition probabilities which can be used for the line ratio estimation, but there are no experimental measurements of this ratio, since the [N II] lines are extremely weak in laboratory plasma. Therefore, the intensity ratio of [N II] lines can be measured only in the spectra of astrophysical objects. However, precise and systematic measurements have not be done so far, because of difficulties in measurement of the [N II] ratio in various spectra (overlapping with H$\alpha$, weak intensity of [N II], influence of the continuum noise and outflow contribution, etc.). Here we present the measurements of the flux ratio of the [N II]$\lambda\lambda$ 6548, 6583 A emission lines for a sample of 250 Type 2 AGNs spectra taken form Sloan Digital Sky Survey (SDSS) data base. The spectra are chosen to have high signal-to-noise ratio and to [N II] and H$\alpha$ lines do not overlap. The obtained mean flux ratio from measurements is 3.049 $\pm$ 0.021. Our result is in agreement with theoretical result obtained by taking into account the relativistic corrections to the magnetic dipole operator.

An important future goal in exoplanetology is to detect and characterize potentially habitable planets. Using nulling interferometry, LIFE will allow us to constrain the radius and effective temperature of (terrestrial) exoplanets, as well as provide unique information about their atmospheric structure and composition. We explore the potential of LIFE in characterizing emission spectra of Earth at various stages of its evolution. We perform Bayesian retrievals on simulated spectra of 8 different scenarios, which correspond to cloud-free and cloudy spectra of four different epochs of the evolution of the Earth. Assuming a distance of 10 pc and a Sun-like host star, we simulate observations obtained with LIFE using its simulator LIFEsim, considering all major astrophysical noise sources. With the nominal spectral resolution (R=50) and signal-to-noise ratio (assumed to be S/N=10 at 11.2 $\mu$m), we can identify the main spectral features of all the analyzed scenarios (most notably CO$_2$, H$_2$O, O$_3$, CH$_4$). This allows us to distinguish between inhabited and lifeless scenarios. Results suggest that particularly O$_3$ and CH$_4$ yield an improved abundance estimate by doubling the S/N from 10 to 20. We conclude that the baseline requirements for R and S/N are sufficient for LIFE to detect O$_3$ and CH$_4$ in the atmosphere of an Earth-like planet with an abundance of O$_2$ of around 2% in volume mixing ratio. This information is relevant in terms of the LIFE mission planning. We also conclude that cloud-free retrievals of cloudy planets can be used to characterize the atmospheric composition of terrestrial habitable planets, but not the thermal structure of the atmosphere. From the inter-model comparison performed, we deduce that differences in the opacity tables (caused by e.g. a different line wing treatment) may be an important source of systematic errors.

Non-ideal magnetohydrodynamic effects that rule the coupling of the magnetic field to the circumstellar gas during the low-mass star formation process depend heavily on the local physical conditions, such as the ionization fraction of the gas. The purpose of this work is to observationally characterize the level of ionization of the circumstellar gas at small envelope radii and investigate its relation to the efficiency of the coupling between the star-forming gas and the magnetic field in the Class 0 protostar B335. We have obtained molecular line emission maps of B335 with ALMA, which we use to measure the deuteration fraction of the gas, its ionization fraction, and the cosmic-ray ionization rate, at envelope radii $\lesssim$1000 au. We find large fractions of ionized gas, $\chi_{e} \simeq 1-8 \times 10^{-6}$. Our observations also reveal an enhanced ionization that increases at small envelope radii, reaching values up to $\zeta_{CR} \simeq 10^{-14}$~s$^{-1}$ at a few hundred au from the central protostellar object. We show that this extreme ionization rate can be attributed to the presence of cosmic rays accelerated close to the protostar. We report the first resolved map of the cosmic-ray ionization rate at scales $\lesssim 1000$~au in a solar-type Class 0 protostar, finding remarkably high values. Our observations suggest that local acceleration of cosmic rays, and not the penetration of interstellar Galactic cosmic rays, may be responsible for the gas ionization in the inner envelope, potentially down to disk forming scales. If confirmed, our findings imply that protostellar disk properties may also be determined by local processes setting the coupling between the gas and the magnetic field, and not only by the amount of angular momentum available at large envelope scales and the magnetic field strength in protostellar cores.

Some of the accreting black holes exhibit much stronger variability patterns than the usual stochastic variations. Radiation pressure instability is one of the proposed mechanisms which could account for this effect. We aim to model luminosity changes for objects with black hole mass of 10, 10$^5$, and 10$^7$ solar masses, using the time-dependent evolution of an accretion disk unstable due to the dominant radiation pressure. We use a 1-dimensional, vertically integrated time-dependent numerical scheme which models simultaneous evolution of the disk and corona, coupled by the vertical mass exchange. We also discuss the possibility of presence of an inner optically thin flow, namely the Advection-Dominated Accretion Flow (ADAF). We found that the outburst character strongly depends on the magnetic field and the outer radius of the disk if this radius is smaller (due to TDE phenomenon) than the size of the instability zone in a stationary disk with infinite radius. For microquasars, the dependence on the magnetic field is monotonic, and the period decreases with the field strength. For larger black hole masses, the dependence is non-monotonic, and initial rise of the period is later replaced with the relatively rapid decrease as the magnetic field continues to rise. Still stronger magnetic field stabilizes the disk. Our computations confirm that the radiation pressure instability model can account for heartbeat states in microquasars. Rapid variability detected in IMBH in the form of Quasi-Periodic Ejection can be consistent with the model but only if combined with TDE phenomenon. Yearly repeating variability in Changing Look AGN also requires, in our model, small outer radius either due to the recent TDE or due to the presence of the gap in the disk related to the presence of a secondary black hole.

The configuration of the interplanetary magnetic field and features of the related ambient solar wind in the ecliptic and meridional plane are different. Therefore, one can expect that the orientation of the flux-rope axis of a coronal mass ejection (CME) influences the propagation of the CME itself. However, the determination of the CME orientation, especially from image data, remains a challenging task to perform. This study aims to provide a reference to different CME orientation determination methods in the near-Sun environment. Also, it aims to investigate the non-radial flow in the sheath region of the interplanetary CME (ICME) in order to provide the first proxy to relate the ICME orientation with its propagation. We investigated 22 isolated CME-ICME events in the period 2008-2015. We determined the CME orientation in the near-Sun environment using the following: 1) a 3D reconstruction of the CME with the graduated cylindrical shell (GCS) model applied to coronagraphic images provided by the STEREO and SOHO missions and; 2) an ellipse fitting applied to single spacecraft data from SOHO/LASCO C2 and C3 coronagraphs. In the near-Earth environment, we obtained the orientation of the corresponding ICME using in situ plasma and field data and also investigated the non-radial flow (NRF) in its sheath region. The ability of GCS and ellipse fitting to determine the CME orientation is found to be limited to reliably distinguish only between the high or low inclination of the events. Most of the CME-ICME pairs under investigation were found to be characterized by a low inclination. For the majority of CME-ICME pairs, we obtain consistent estimations of the tilt from remote and in situ data. The observed NRFs in the sheath region show a greater y direction to z direction flow ratio for high-inclination events, indicating that the CME orientation could have an impact on the CME propagation.

Precision-era optical cluster cosmology calls for a precise definition of the red sequence (RS), consistent across redshift. To this end, we present the Red Dragon algorithm: an error-corrected multivariate Gaussian mixture model (GMM). Simultaneous use of multiple colors and smooth evolution of GMM parameters result in a continuous RS and blue cloud (BC) characterization across redshift, avoiding the discontinuities of red fraction inherent in swapping RS selection colors. Based on a mid-redshift spectroscopic sample of SDSS galaxies, a RS defined by Red Dragon selects quenched galaxies (low specific star formation rate) with a balanced accuracy of over 90%. This approach to galaxy population assignment gives more natural separations between RS and BC galaxies than hard cuts in color--magnitude or color--color spaces. The Red Dragon algorithm is publicly available at bitbucket.org/wkblack/red-dragon-gamma.

Ultra-hot Jupiters (UHJs) are expected to possess temperature inversion layers in their dayside atmospheres. Recent thermal emission observations have discovered several atomic and molecular species along with temperature inversions in UHJs. We observed the thermal emission spectra of two UHJs (WASP-33b and WASP-189b) with the GIANO-B high-resolution near-infrared spectrograph. Using the cross-correlation technique, we detected carbon monoxide (CO) in the dayside atmospheres of both planets. The detected CO lines are in emission, which agrees with previous discoveries of iron emission lines and temperature inversions in the two planets. This is the first detection of CO lines in emission with high-resolution spectroscopy. Further retrieval work combining the CO lines with other spectral features will enable a comprehensive understanding of the atmospheric properties such as temperature structures and C/O ratios. The detected CO and iron emission lines of WASP-189b have redshifted radial velocities of several km/s, which likely originate from a dayside to nightside wind in its atmosphere. Such a redshifted velocity has not been detected for the emission lines of WASP-33b, suggesting that the atmospheric circulation patterns of the two UHJs may be different.

We report the results of new XMM-Newton observations of the middle-aged ($\sim$10$^5$ yr) radio pulsar PSR J1740+1000 carried out in 2017-2018. These long pointings ($\sim$530 ks) show that the non-thermal emission, well described by a power-law spectrum with photon index $\Gamma=1.80\pm0.17$, is pulsed with a $\sim$30% pulsed fraction above 2 keV. The thermal emission can be well fit with the sum of two blackbodies of temperatures $kT_1=70\pm4$ eV, $kT_2=137\pm7$ eV, $R_1=5.4_{-0.9}^{+1.3}$ km and $R_2=0.70_{-0.13}^{+0.15}$ km (for a distance of 1.2 kpc). We found no evidence for absorption lines as those observed in the shorter XMM-Newton observations ($\sim$67 ks) of this pulsar carried out in 2006. The X-ray thermal and non-thermal components peak in anti-phase and none of them is seen to coincide in phase with the radio pulse. This, coupled with the small difference in the emission radii of the two thermal components, disfavors an interpretation in which the dipolar polar cap is heated by magnetospheric backward-accelerated particles. Comparison with the other thermally-emitting isolated neutron stars with spectra well described by the sum of two components shows that the ratios $T_2$/$T_1$ and $R_2$/$R_1$ are similar for objects of different classes. The observed values cannot be reproduced with simple temperature distributions, such as those caused by a dipolar field, indicating the presence of more complicated thermal maps.

We report results from our ongoing project MOMO (Multiwavelength Observations and Modelling of OJ 287). In this latest publication of a sequence, we combine our Swift UVOT--XRT and Effelsberg radio data (2.6-44 GHz) between 2019 and 2022.04 with public SMA data and gamma-ray data from the Fermi satellite. The observational epoch covers OJ 287 in a high state of activity from radio to X-rays. The epoch also covers two major events predicted by the binary supermassive black hole (SMBH) model of OJ 287. Spectral and timing analyses clearly establish: a new UV-optical minimum state in 2021 December at an epoch where the secondary SMBH is predicted to cross the disk surrounding the primary SMBH; an overall low level of gamma-ray activity in comparison to pre-2017 epochs; the presence of a remarkable, long-lasting UV--optical flare event of intermediate amplitude in 2020--2021; a high level of activity in the radio band with multiple flares; and particularly a bright, ongoing radio flare peaking in 2021 November that may be associated with a gamma-ray flare, the strongest in 6 years. Several explanations for the UV--optical minimum state are explored, including the possibility that a secondary SMBH launches a temporary jet, but the observations are best explained by variability associated with the main jet.

We report the discovery of a multi-planetary system transiting the M0 V dwarf HD 260655 (GJ 239, TOI-4599). The system consists of at least two transiting planets, namely HD 260655 b, with a period of 2.77 d, a radius of R$_b$ = 1.240$\pm$0.023 R$_\oplus$, a mass of M$_b$ = 2.14$\pm$0.34 M$_\oplus$, and a bulk density of $\rho_b$ = 6.2$\pm$1.0 g cm$^{-3}$, and HD 260655 c, with a period of 5.71 d, a radius of R$_c$ = 1.533$^{+0.051}_{-0.046}$ R$_\oplus$, a mass of M$_c$ = 3.09$\pm$0.48 M$_\oplus$, and a bulk density of $\rho_c$ = 4.7$^{+0.9}_{-0.8}$ g cm$^{-3}$. The planets were detected in transit by the TESS mission and confirmed independently with archival and new precise radial velocities obtained with the HIRES and CARMENES instruments since 1998 and 2016, respectively. At a distance of 10 pc, HD 260655 becomes the fourth closest known multi-transiting planet system after HD 219134, LTT 1445 A, and AU Mic. Due to the apparent brightness of the host star (J = 6.7 mag), both planets are among the most suitable rocky worlds known today for atmospheric studies with the JWST, both in transmission and emission.

Due to their strong resonances with their host planet, Trojan asteroids can remain in stable orbits for billions of years. As a result, they are powerful probes for constraining the dynamical and chemical history of the solar system. Although we have detected thousands of Jupiter Trojans and dozens of Neptune Trojans, there are currently no known long-term stable Earth Trojans. Dynamical simulations show that the parameter space for stable Earth Trojans in substantial, so their apparent absence poses a mystery. This work uses a large ensemble of N-body simulations to explore how the Trojan population dynamically responds if Earth suffers large collisions, such as those thought to have occurred to form the Moon and/or to have given Earth its Late Veneer. We show that such collisions can be highly disruptive to the primordial Trojan population, and could have eliminated it altogether. More specifically, if Earth acquired the final 1\% of its mass through ${\cal O}(10)$ collisions, then only $\sim1\%$ of the previously bound Trojan population would remain.

In the standard cosmological model the dark energy (DE) and nonrelativistic (NR) matter densities are determined to be comparable at the present time, in spite of their greatly different evolution histories. This `cosmic coincidence' enigma could be explained as a non-anthropic observational selection effect: We show that in a suitably chosen frame the Universe is at its most probable epoch when the Hubble radius attains a maximum, at the epoch when the energy densities of DE and NR matter are comparable.

We investigate McVittie and generalized McVittie solutions for Horndeski gravity with a spatially homogeneous gravitational scalar field, which is stealth at small scales near the central object but, at large scales, sources the FLRW universe in which the central inhomogeneity is embedded. Unlike previous studies, we include matter and obtain generalized McVittie solutions in the extended cuscuton model. The possible configurations are classified according to the time-dependence of the gravitational coupling, the radial energy flow, the accretion rate onto the central object, and the Hubble rate.

Testing the variation of fundamental constants of Nature can provide valuable insights into new physics scenarios. While many constraints have been derived for Standard Model coupling constants and masses, the $\bar{\theta}$ parameter of QCD has often been ignored in these studies. This letter discusses potentially promising paths to investigate the time dependence of the $\bar{\theta}$ parameter. While laboratory searches for CP-violating signals of $\bar{\theta}$ yield the most robust bounds on today's value of $\bar{\theta}$, we show that CP-conserving effects provide constraints on the variation of $\bar{\theta}$ over cosmological time scales. We find no significant evidence for a variation of $\bar{\theta}$ except for a mild hint around $z\sim 4$ which would imply an "iron-deficient" Universe at high redshifts. Finally, we also sketch an axion model which results in a varying $\bar{\theta}$ and could lead to excess diffuse gamma ray background, from decays of axions produced in high redshift supernova explosions.

Time-series data has an increasingly growing usage in Industrial Internet of Things (IIoT) and large-scale scientific experiments. Managing time-series data needs a storage engine that can keep up with their constantly growing volumes while providing an acceptable query latency. While traditional ACID databases favor consistency over performance, many time-series databases with novel storage engines have been developed to provide better ingestion performance and lower query latency. To understand how the unique design of a time-series database affects its performance, we design SciTS, a highly extensible and parameterizable benchmark for time-series data. The benchmark studies the data ingestion capabilities of time-series databases especially as they grow larger in size. It also studies the latencies of 5 practical queries from the scientific experiments use case. We use SciTS to evaluate the performance of 4 databases of 4 distinct storage engines: ClickHouse, InfluxDB, TimescaleDB, and PostgreSQL.

Thermoelastic loss is one of the main energy dissipation mechanisms in resonant systems. A careful analysis of the thermoelastic loss is critical to design low-noise resonators for high-precision applications, such as gravitational-wave detectors. This paper presents an analytical solution to the thermoelastic loss in multimaterial coated finite substrates with realistic assumptions on the model structure and the elastic fields. The mechanism responsible for thermoelastic loss is taken as a function of material properties, operating temperature and frequency, and other design parameters. We calculate the thermoelastic loss for specific applications over a wide range of frequencies (1 Hz to 10 GHz) and temperatures (1 K to 300 K), and for a variety of substrate and coating materials. The result is relevant for gravitational-wave detectors and for experiments sensitive to mechanical dissipation.

We proposed in this paper a new method, which we named the W4 method, to solve nonlinear equation systems. It may be regarded as an extension of the Newton-Raphson~(NR) method to be used when the method fails. Indeed our method can be applied not only to ordinary problems with non-singular Jacobian matrices but also to problems with singular Jacobians, which essentially all previous methods that employ the inversion of the Jacobian matrix have failed to solve. In this article, we demonstrate that (i) our new scheme can define a non-singular iteration map even for those problems by utilizing the singular value decomposition, (ii) a series of vectors in the new iteration map converges to the right solution under a certain condition, (iii) the standard two-dimensional problems in the literature that no single method proposed so far has been able to solve completely are all solved by our new method.

We present a new formulation to construct numerically equilibrium configurations of rotating stars in general relativity. Having in mind the application to their quasi static evolutions, we adopt a Lagrangian formulation of our own devising, in which we solve force balance equations to seek for the positions of fluid elements assigned to the grid points, instead of the ordinary Eulerian formulation. Unlike previous works in the literature, we do not employ the first integral of the Euler equation, which is not obtained by an analytic integration in general. We assign a mass, specific angular momentum and entropy to each fluid element in contrast to the previous methods, in which the spatial distribution of the angular velocity or angular momentum is specified. Those distributions are determined after the positions of all fluid elements (or grid points) are derived in our formulation. We solve the large system of algebraic nonlinear equations that are obtained by discretizing the time-independent Euler and Einstein equations in the finite-elements method by using our new multi-dimensional root-finding scheme, named the W4 method. To demonstrate the capability of our new formulation, we construct some rotational configurations both barotropic and baroclinic. We also solve three evolutionary sequences that mimic the cooling, mass-loss, and mass-accretion as simple toy models.

Primordial gravitational waves (PGW) produced during inflation span a large range of frequencies, carrying information on the dynamics of the primordial universe. During an early scalar-tensor dominated epoch, the amplitude of the PGW spectrum can be enhanced over a wide range of frequencies. To study this phenomenon, we focus on a class of scalar-tensor theories, well motivated by high energy theories of dark energy and dark matter, where the scalar is conformally and disformally coupled to matter during the early cosmological evolution. For a conformally dominated epoch, the PGW spectrum has a flat step-like shape. More interestingly, a disformally dominated epoch is characterised by a peaked spectrum with a broken power-law profile, with slopes depending on the scalar-tensor theory considered. We introduce a graphical tool, called broken power-law sensitivity curve, as a convenient visual indicator for understanding whether a given broken power-law profile can be detected by GW experiments. We then analyse the GW spectra for a variety of representative conformal and disformal models, discussing their detectability prospects with the Einstein Telescope (ET), Laser Interferometer Space Antenna (LISA), DECi-hertz Interferometer Gravitational wave Observatory (DECIGO), and Big Bang Observer (BBO).