Papers for Monday, Sep 23 2024

It was recently claimed (arXiv:2409.09081v1 [astro-ph.HE]) that accretion of ordinary matter on black holes of mass $(6\times 10^{14}-4\times10^{19})\,$g would be inhibited by quantum mechanical effects, namely the de Broglie wavelength of the electron being larger than the Schwarzschild radius. However the conclusion is based on considering accretion of a single atom over the age of the Universe. There is no suppression of the accretion rate per atom on such black holes.

Evaluating the Kirchhoff-Fresnel diffraction integral is essential in studying wave effects in astrophysical lensing, but is often intractable because of the highly oscillatory integrated. A recent breakthrough was made by exploiting the Picard-Lefschetz theory: the integral can be performed along the `Lefschetz thimbles' in the complex domain where the integrand is not oscillatory but rapidly converging. The application of this method, however, has been limited by both the unfamiliar concepts involved and the low numerical efficiency of the method used to find the Lefschetz thimbles. In this paper, we give simple examples of the Lefschetz thimbles and define the `flow lines' that facilitate the understanding of the concepts. Based on this, we propose new ways to obtain the Lefschetz thimbles with high numerical efficiency, which provide an effective tool for studying wave effects in astrophysical lensing.

Conventional narrowband photoelectric photometry of Comet Hale-Bopp (1995 O1) was obtained on 99 nights from mid-1995 to early-2000, yielding gas and dust production rates over an unprecedented range of time and distance. The appearance of Hale-Bopp presented a prime opportunity for active comet studies and its inherent brightness and orbital geometry allowed the characterization of its long-term activity. Throughout the apparition Hale-Bopp released, by far, more gas and dust than any other comet ever measured. As a very high dust-to-gas ratio object, dust production was successfully measured throughout the apparition, with dust consistently slightly red in color. All five gas species including OH and NH were detected just inside of 5 AU inbound, while C2 and C3 were detected to just past 5 AU outbound and CN was followed until nearly 7.7 AU. Heliocentric distance dependencies ranged between -1.2 to -2.7 in log-log space, with the extremes magnified by the large extrapolations in Haser model parameters at large distances. Hale-Bopp's enormous size and associated extremely high outgassing resulted in a much larger collisional zone, which in turn yielded outflow velocities more than 2x higher than ever previously measured at comparable distances. Even so, volatile composition remained within the "typical" classification, consistent with most Oort Cloud comets, and water production follows the expected curve based on a standard water vaporization model. However, seasonal effects provided evidence for inhomogeneities among the major source regions on the surface of the nucleus. Preliminary modeling of the nucleus and coma successfully matches this seasonal behavior.

The way in which the large-scale cosmic environment affects galactic properties is not yet understood. Dark matter halos, which embed galaxies, initially evolve following linear theory. Their subsequent evolution is driven by non-linear structure formation in the halo region and in its outer environment. In this work, we present the first study where we explicitly control the linear part of the evolution of the halo, thus revealing the role of non-linear effects on halo formation. We focus specifically on the effect of proximity to a large cosmological filament. We employ the splicing method to keep fixed the initial density, velocity, and potential fields where a halo will form while changing its outer environment, from an isolated state to one where the halo is near a large filament. In the regime of Milky Way-mass halos, we find that mass and virial radius of such halos are not affected by even drastic changes of environment, whereas halo spin and shape orientation with respect to a massive filament is largely impacted, with fluctuations of up to 80 % around the mean value. Our results suggest that halo orientation and shape cannot be predicted accurately from a local analysis in the initial conditions alone. This has direct consequences on the modeling of intrinsic alignment for cosmic shear surveys, like Euclid. Our results highlight that non-linear couplings to the large-scale environment may have an amplitude comparable to linear effects, and should thus be treated explicitly in analytical models of dark matter halo formation.

Massive black-hole binaries will be the loudest sources detectable by LISA. These systems are predicted to form during the hierarchical assembly of cosmic structures and coalesce by interacting with the surrounding environment. The hardening phase of their orbit is driven by either stars or gas and encodes distinctive features into the binary black holes that can potentially be reconstructed with gravitational-wave observations. We present a Bayesian framework to assess the likelihood of massive mergers being hardened by either gaseous or stellar interactions. We use state-of-the-art astrophysical models tracking the cosmological evolution of massive black-hole binaries and construct a large number of simulated catalogs of sources detectable by LISA. From these, we select a representative catalog and run both parameter estimation assuming a realistic LISA response as well model comparison capturing selection effects. Our results suggest that, at least within the context of the adopted models, future LISA observations can confidently constrain whether stars or gas are responsible for the binary hardening. We stress that accurate astrophysical modeling of the black-hole spins and the inclusion of subdominant emission modes in the adopted signal might be crucial to avoid systematic biases.

It is now well known that certain massive galaxies undergo enormous enhancements in their SFR when they undergo major mergers(100x). To analyse the SF enhancement and AGN fraction evolution during the merger process, we use a more timeline-like merger sequence. Also, to determine the relation between the SF enhancement in mergers and the morphology of the galaxies involved. Taking advantage of the Mstr and SFR of 600 nearby isolated mergers from our previous study, we calculate the distance of our galaxies from the SF MS, which we refer to as SFmode. We analyse how the SFmode varies during the merger process, for morphology and Mstr. We also analyse the AGN content of our mergers, using multiple diagnostics based on emission line ratios and WISE colours. We observe that, overall, merging galaxies show a SFmode that is governed by their morphology. Spirals typically show high SFmode values while highly-disturbed galaxies are generally even more enhanced (0.8dex and 1dex above the MS, resp). On the contrary, elliptical and lenticular galaxies show the lowest SF modes, as expected. However, even they show SF enhancement compared to their unperturbed counterparts (their median SFmode is within the 1-sigma scatter of the MS, and this can occur even before the galaxies have coalesced). We see a trend for SFmode to gradually increase with increasing merger stage. We do not find a clear dependency of the observed AGN fraction on merger stage for the majority of our classification methods. We find mergers can significantly enhance SF in galaxies of all morphologies. For early-type galaxies, this could suggest that some gas was present prior to the merger which may be triggered to form stars by the tidal interaction. As the SF enhancement continues throughout the merger process, this suggests that the enhancement may be a long-lived event, contrary to the short starbursts seen in some models.

We resolve the multiple images of the binary-lens microlensing event ASASSN-22av using the GRAVITY instrument of the Very Large Telescope Interferometer (VLTI). The light curves show weak binary perturbations, complicating the analysis, but the joint modeling with the VLTI data breaks several degeneracies, arriving at a strongly favored solution. Thanks to precise measurements of angular Einstein radius \theta_E = 0.726 +/- 0.002 mas and microlens parallax, we determine that the lens system consists of two M dwarfs with masses of M_1 = 0.261 +/- 0.009 M_sun and M_2 = 0.252 +/- 0.017 M_sun, a projected separation of r_\perp = 7.42 +/- 0.33 AU and a distance of D_L = 2.31 +/- 0.09 kpc. The successful VLTI observations of ASASSN-22av open up a new path for studying intermediate-separation (i.e., a few AUs) stellar-mass binaries, including those containing dark compact objects such as neutron stars and stellar-mass black holes.

The 21-cm background is a promising probe of early star formation and black hole activity. While a slew of experiments on the ground seek to detect the 21-cm monopole and spatial fluctuations on large $\sim 10$ arcminute scales, little work has been done on the prospects for detecting the 21-cm dipole signal or its utility as a probe of early galaxies. Though an intrinsically weak signal relative to the monopole, its direction is known well from the cosmic microwave background and wide-field surveys, plus as a relative measurement the dipole could help relax instrumental requirements. In order to understand the constraining power of the dipole, in this work we perform parameter inference on mock datasets that include the dipole, monopole, or both signals. We find that while the monopole does provide the best constraints for a given integration time, constraints from a dipole measurement are competitive, and can in principle constrain the cosmic star formation rate density and efficiency of X-ray photon production in early $z \sim 15$ galaxies to better than a factor of $\sim 2$. This result holds for most of the available prior volume, which is set by constraints on galaxy luminosity functions, the reionization history, and upper limits from 21-cm power spectrum experiments. We also find that predictions for the monopole from a dipole measurement are robust to different choices of signal model. As a result, the 21-cm dipole signal is a valuable target for future observations and offers a robust cross-check on monopole measurements.

Stars and planets form in regions of enhanced stellar density, subjecting protoplanetary discs to gravitational perturbations from neighbouring stars. Observations in the Taurus star-forming have uncovered evidence of at least three recent, star-disc encounters that have truncated discs (HV/DO Tau, RW Aurigae, UX Tau), raising questions about the frequency of such events. We aim to assess the probability of observing truncating star-disc encounters in Taurus. We generate a physically motivated dynamical model including binaries and spatial-kinematic substructure to follow the historical dynamical evolution and stellar encounters in the Taurus star forming region. We track the star-disc encounters and outer disc radius evolution over the lifetime of Taurus. A quarter of discs are truncated below 30 au by dynamical encounters, but this truncation mostly occurs in binaries over the course of a few orbital periods, on a time-scale $\lesssim 0.1$ Myr. Nonetheless, some truncating encounters still occur up to the present age of Taurus. Strongly truncating encounters (ejecting $\gtrsim 10$ percent of the disc mass) occur at a rate $\sim 10$ Myr$^{-1}$, sufficient to explain the encounter between HV and DO Tau $\sim 0.1$ Myr ago. If encounters that eject only $\sim 1$ percent of the disc mass are responsible for RW Aurigae and UX Tau, then they are also expected with encounter rate $\Gamma_\mathrm{enc} \sim 100{-}200$ Myr$^{-1}$. However, the observed sample of recent encounters is probably incomplete, since these examples occurred in systems that are not consistent with random drawing from the mass function. One more observed example would statistically imply additional physics, such as replenishment of the outer disc material.

We present the updated constraints on cosmological parameters in a 12 parameter cosmology extended with dynamical dark energy parameters ($w_0$, $w_a$), sum of neutrino masses ($\sum m_{\nu}$), effective number of neutrinos ($N_{\rm eff}$), scaling of the lensing amplitude ($A_{\rm lens}$), and running of the scalar spectral index ($\alpha_s$). For 'CMB' data, we use the latest Planck PR4 (2020) HiLLiPoP and LoLLiPoP likelihoods, Planck PR4+ACT DR6 lensing, and Planck 2018 lowl-$l$ TT likelihoods. Also, we use the latest DESI DR1 BAO likelihoods and SNeIa likelihoods from the Pantheon+ and DESY5 samples. We find: i) Contrary to the findings of DESI collaboration, we find that the CMB+BAO+Pantheon+ leads to the inclusion of cosmological constant within $2\sigma$, while CMB+BAO+DESY5 excludes the same at more than 2$\sigma$. Thus, the dynamical nature of dark energy cannot yet be considered a robust cosmological signature. As pointed out in earlier literature, the DESY5 SNe sample might have systematics which are driving the exclusion of cosmological constant. ii) We find that for certain data combinations lead to a 1$\sigma$+ detection of $\sum m_{\nu}$, and we get a posterior peak in all dataset combinations, which is an encouraging trend towards future detection. We also provide a robust bound of $\sum m_{\nu} \lesssim 0.3$ eV (95%). Given the current uncertainty in determining the correct underlying cosmological model, we prescribe this bound for the cosmology and particle physics community. iii) With CMB+BAO+SNe, we find that $A_{\rm lens}=1$ is included at 2$\sigma$ but not at $1\sigma$. This indicates that with Planck PR4 likelihoods, there is currently no lensing anomaly in a dynamical dark energy cosmology. iv) We find that even in this largely extended cosmology, the Hubble tension persists at the level of 3.2-3.9$\sigma$. (truncated)

We present recent laboratory results demonstrating high-contrast coronagraphy for the future space-based large IR/Optical/Ultraviolet telescope recommended by the Decadal Survey. The High-contrast Imager for Complex Aperture Telescopes (HiCAT) testbed aims to implement a system-level hardware demonstration for segmented aperture coronagraphs with wavefront control. The telescope hardware simulator employs a segmented deformable mirror with 37 hexagonal segments that can be controlled in piston, tip, and tilt. In addition, two continuous deformable mirrors are used for high-order wavefront sensing and control. The low-order sensing subsystem includes a dedicated tip-tilt stage, a coronagraphic target acquisition camera, and a Zernike wavefront sensor that is used to measure and correct low-order aberration drifts. We explore the performance of a segmented aperture coronagraph both in static operations (limited by natural drifts and instabilities) and in dynamic operations (in the presence of artificial wavefront drifts added to the deformable mirrors), and discuss the estimation and control strategies used to reach and maintain the dark-zone contrast using our low-order wavefront sensing and control. We summarize experimental results that quantify the performance of the testbed in terms of contrast, inner/outer working angle and bandpass, and analyze limiting factors.

In direct imaging at high contrast, the bright glare produced by the host star makes the detection and the characterization of sub-stellar companions particularly challenging. In spite of the use of an extreme adaptive optics system combined with a coronagraphic mask to strongly attenuate the starlight contamination, dedicated post-processing methods combining several images recorded with the pupil tracking mode of the telescope are needed to reach the required contrast. In that context, we recently proposed to combine the statistics-based model of PACO with a deep learning approach in a three-step algorithm. First, the data are centered and whitened locally using the PACO framework to improve the stationarity and the contrast in a preprocessing step. Second, a convolutional neural network (CNN) is trained in a supervised fashion to detect the signature of synthetic sources in the preprocessed science data. Finally, the trained network is applied to the preprocessed observations and delivers a detection map. A second network is trained to infer locally the photometry of detected sources. Both deep models are trained from scratch with a custom data augmentation strategy allowing to generate a large training set from a single spatio-temporo-spectral dataset. This strategy can be applied to process jointly the images of observations conducted with angular, and eventually spectral, differential imaging (A(S)DI). In this proceeding, we present in a unified framework the key ingredients of the deep PACO algorithm both for ADI and ASDI. We apply our method on several datasets from the the IRDIS imager of the VLT/SPHERE instrument. Our method reaches, in average, a better trade-off between precision and recall than the comparative algorithms.

PLATO will begin observing stars in its Southern Field (LOPS2) after its launch in late 2026. By this time, TESS will have observed the stars in LOPS2 for at least four years. We find that by 2025, on average each star in the PLATO field will have been monitored for 330 days by TESS, with a subset of stars in the TESS continuous viewing zone having over 1000 days of monitoring. There are currently 96 known transiting exoplanets in the LOPS2 field, with 33 of these residing in multiplanet systems. The LOPS2 field also contains around 500 TESS planet candidate systems, over 1000 bright (V<13) eclipsing binary systems, 6 transiting brown dwarf systems, and 2 bright white dwarfs (G<13). We calculate TESS and PLATO sensitivities to detecting transits for the bright FGK stars that make up the PLATO LOPS2 P1 sample. We find that TESS should have discovered almost all transiting giant planets out to approximately 30 d within the LOPS2 field, and out to approximately 100 d for the regions of the LOPS2 field within the TESS CVZ ($\sim$20 per cent of the LOPS2 field). However, we find that for smaller radius planets in the range 1$-$4 R$_\oplus$ PLATO will have significantly better sensitivity, and these are likely to make up the bulk of new PLATO discoveries.

A multitude of JWST studies reveal a surprising over-abundance of over-massive accreting super-massive blackholes (SMBHs) -- leading to a deepening tension between theory and observation in the first billion years of cosmic time. Across X-ray to infrared wavelengths, models built off of pre-JWST predictions fail to easily reproduce observed AGN signatures (or lack thereof), driving uncertainty around the true nature of these sources. Using a sample of JWST AGN identified via their broadened Halpha emission and covered by the deepest X-ray surveys, we find neither any measurable X-ray emission nor any detection of high-ionization emission lines frequently associated with accreting SMBHs. We propose that these sources are accreting at or beyond the Eddington limit, which reduces the need for efficient production of heavy SMBH seeds at cosmic dawn. Using a theoretical model of super-Eddington accretion, we can produce the observed relative dearth of both X-ray and ultraviolet emission, as well as the high Balmer decrements, without the need for significant dust attenuation. This work indicates that super-Eddington accretion is easily achieved through-out the early Universe, and further study is required to determine what environments are required to trigger this mode of black hole growth.

The discovery of over 5700 exoplanets has led to a boom in the field of exoplanet demographics over the past decade. Led by swaths of exoplanet discoveries from NASA's Kepler space mission, astronomers have been conducting statistical studies of the exoplanet population in search of trends in various planetary and host stellar parameters. These investigations are informing our understanding of how planets form and evolve, thus putting our solar system into a galactic context. In this chapter, we review many of the major features uncovered in the distributions of physical and orbital parameters of known exoplanets including the Radius Valley, the Neptunian Desert, the Peas in a Pod pattern, dynamical properties that point toward likely formation/migration mechanisms, as well as trends with host stellar parameters such as the time-evolution of exoplanetary systems and the search for planets within the Habitable Zone. The overarching theme is that exoplanetary systems exhibit an incredible diversity of planet properties and system architectures that do not exist within our own solar system. A promising future awaits the field of exoplanet demographics with increasingly deep investigations planned following the launch of numerous dedicated space telescopes over the coming years and decades.

Archean atmospheric evolution is the transition from an abiological atmosphere, to an atmosphere for which the composition and therefore climate is highly altered by life. We review the key processes and transitions in this evolution.

The radiance of nighttime artificial lights measured by the VIIRS-DNB instrument on board the satellite Suomi-NPP increases at an average rate ~2.2 %/yr worldwide, whereas the artificial radiance of the night sky deduced from the Globe at Night (GAN) unaided-eye observations of the number of visible stars is reported to increase at an average rate ~9.6 %/yr. The difference between these two estimates is remarkable. This raises the question of whether the diverging temporal evolution of these indicators could be due to changes in the spectral composition of outdoor artificial light, consequence of the current process of replacement of lighting technologies. This paper presents a model for evaluating the temporal rate of change of different light pollution indicators and applies it to the VIIRS-DNB vs GAN issue, based on available data. The results show that the reported difference could be explained by spectral changes alone, if the visual observations are made under scotopic adaptation in some specific transition conditions. In case of photopic adapted observers, however, reconciling these two measurement sets requires the existence of additional light sources that affect the Globe at Night observations but do not show up in the VIIRS-DNB data. The lumen emissions of these specific sources should increase at a rate 6 %/yr worlwide, adding to the estimated 3 %/yr of the remaining lights deduced from the VIIRS-DNB measurements corrected for spectral shift.

Real-time control (RTC) is pivotal for any Adaptive Optics (AO) system, including high-contrast imaging of exoplanets and circumstellar environments. It is the brain of the AO system, and what wavefront sensing and control (WFS\&C) techniques need to work with to achieve unprecedented image quality and contrast, ultimately advancing our understanding of exoplanetary systems in the context of high contrast imaging (HCI). Developing WFS\&C algorithms first happens in simulation or a lab before deployment on-sky. The transition to on-sky testing is often challenging due to the different RTCs used. Sharing common RTC standards across labs and telescope instruments would considerably simplify this process. A data architecture based on the interprocess communication method known as shared memory is ideally suited for this purpose. The CACAO package, an example of RTC based on shared memory, was initially developed for the Subaru-SCExAO instrument and now deployed on several benches and instruments. This proceeding discusses the challenges, requirements, implementation strategies, and performance evaluations associated with integrating a shared memory-based RTC. The Santa Cruz Extreme AO Laboratory (SEAL) bench is a platform for WFS\&C development for large ground-based segmented telescopes. Currently, SEAL offers the user a non-real-time version of CACAO, a shared-memory based RTC package initially developed for the Subaru-SCExAO instrument, and now deployed on several benches and instruments. We show here the example of the SEAL RTC upgrade as a precursor to both RTC upgrade at the 3-m Shane telescopes at Lick Observatory (Shane-AO) and a future development platform for the Keck II AO. This paper is aimed at specialists in AO, astronomers, and WFS\&C scientists seeking a deeper introduction to the world of RTCs.

We present the Pilot Survey Phase 2 data release for the Wide-field ASKAP L-band Legacy All-sky Blind surveY (WALLABY), carried-out using the Australian SKA Pathfinder (ASKAP). We present 1760 HI detections (with a default spatial resolution of 30") from three pilot fields including the NGC 5044 and NGC 4808 groups as well as the Vela field, covering a total of ~180 deg$^2$ of the sky and spanning a redshift up to $z \simeq 0.09$. This release also includes kinematic models for over 126 spatially resolved galaxies. The observed median rms noise in the image cubes is 1.7 mJy per 30" beam and 18.5 kHz channel. This corresponds to a 5$\sigma$ HI column density sensitivity of $\sim 9.1\times10^{19}(1 + z)^4$ cm$^{-2}$ per 30" beam and $\sim 20$ km/s channel, and a 5$\sigma$ HI mass sensitivity of $\sim 5.5\times10^8 (D/100$ Mpc)$^{2}$ M$_{\odot}$ for point sources. Furthermore, we also present for the first time 12" high-resolution images ("cut-outs") and catalogues for a sub-sample of 80 sources from the Pilot Survey Phase 2 fields. While we are able to recover sources with lower signal-to-noise ratio compared to sources in the Public Data Release 1, we do note that some data quality issues still persist, notably, flux discrepancies that are linked to the impact of side lobes associated with the dirty beams due to inadequate deconvolution. However, in spite of these limitations, the WALLABY Pilot Survey Phase 2 has already produced roughly a third of the number of HIPASS sources, making this the largest spatially resolved HI sample from a single survey to date.

We introduce a method for removing CMB and anomalous microwave emission (AME, or spinning dust) intensity signals at high to intermediate Galactic latitudes in temperature sky maps at frequencies roughly between 5 and 40 GHz. The method relies on the assumption of a spatially uniform combined dust (AME and thermal) rms spectral energy distribution for these regions, but is otherwise model independent. A difference map is produced from input maps at two different frequencies in thermodynamic temperature: the two frequencies are chosen such that the rms AME signal in the lower frequency (~5 - 40 GHz) map is equivalent to the thermal dust emission rms in the higher frequency (~95 - 230 GHz) map. Given the high spatial correlation between AME and thermal dust, the resulting difference map is dominated by synchrotron and free-free foreground components, and can thus provide useful insight into the morphology and possible spectral variations of these components at high latitudes. We show examples of these difference maps obtained with currently available WMAP and Planck data and demonstrate the efficacy of CMB and dust mitigation using this method. We also use these maps, in conjunction with Haslam 408 MHz and WHAM H-alpha observations, to form an estimate of the diffuse synchrotron spectral index in temperature on degree scales. The hybrid analysis approach we describe is advantageous in situations where frequency coverage is insufficient to break spectral degeneracies between AME and synchrotron.

We identify delta Scuti pulsators amongst members of the recently-discovered Cep--Her Complex using light curves from the Transiting Exoplanet Survey Satellite (TESS). We use Gaia colours and magnitudes to isolate a subsample of provisional Cep--Her members that are located in a narrow band on the colour--magnitude diagram compatible with the zero-age main sequence. The $\delta$ Sct pulsator fraction amongst these stars peaks at 100% and we describe a trend of higher pulsator fractions for younger stellar associations. We use four methods to measure the frequency of maximum amplitude or power, $\nu_{\rm max}$, to minimise methodological bias and we demonstrate their sound performance. The $\nu_{\rm max}$ measurements display a correlation with effective temperature, but with scatter that is too large for the relation to be useful. We find two ridges in the $\nu_{\rm max}$--$T_{\rm eff}$ diagram, one of which appears to be the result of rapid rotation causing stars to pulsate in low-order modes. We measure the $\nu_{\rm max}$ values of $\delta$ Sct stars in four other clusters or associations of similar age (Trumpler 10, the Pleiades, NGC 2516, and Praesepe) and find similar behaviour with $T_{\rm eff}$. Using échelle diagrams we measure the asteroseismic large spacing, $\Delta\nu$, for 70 stars, and find a correlation between $\Delta\nu$, rotation, and luminosity that allows rapid rotators seen at low inclinations to be distinguished from slow rotators. We find that rapid rotators are more likely than slow rotators to pulsate, but they do so with less regular pulsation patterns. We also investigate the reliability of Gaia's vbroad measurement for A-type stars, finding that it is mostly accurate but underestimates $v\sin i$ for slow rotators ($v\sin i < 50$ km.s$^{-1}$) by 10--15%.

Atmosphere-skimming air showers are initiated by cosmic rays with incoming directions that allow the cascade to develop entirely within the atmosphere, without reaching the ground. Radio pulses induced by this type of showers have already been observed in balloon-borne experiments such as ANITA, but a detailed characterisation of their properties is lacking. The extreme range of densities in which these cascades can develop gives rise to a wide range of shower profiles, with radio emission characteristics that can differ significantly from those of regular downward-going showers. In this work, we have used the ZHAireS-RASPASS program to characterise the expected radio emission from atmosphere-skimming air showers and its properties. We have studied the interplay between the magnetic field and atmospheric density profile in the expected radio signal, focusing on its detection aboard balloon-borne experiments. The almost horizontal geometry of the events gives rise to a significant \textit{refractive} asymmetry in the spatial distribution of the electric field, due to the propagation of the radio signals across a gradient of index of refraction. In addition, a unique \textit{coherence} asymmetry appears in the intensity of the signals, as a consequence of the cumulative effect of the Earth's magnetic field over the very long distances that these particle cascades traverse. The implications of the peculiar characteristics of the emission are discussed regarding their impact both on the interpretation of collected data and in the exposure of balloon-borne experiments

Over 700 bright millisecond-duration radio transients, known as Fast Radio Bursts (FRBs), have been identified to date. Nevertheless, the origin of FRBs remains unknown. The two repeating FRBs (FRB 20121102A and FRB 20190520B) have been verified to be associated with persistent radio sources (PRSs), making them the best candidates to study the nature of FRBs. Monitoring the variability in PRSs is essential for understanding their physical nature. We conducted 22 observations of the PRSs linked to FRB 20121102A and FRB 20190520B using the Karl G. Jansky Very Large Array (VLA), to study their variability. We have observed significant flux variability for the PRSs of FRB 20121102A and FRB 20190520B, with a confidence level exceeding 99.99%, based on the observations covering the longest timescale recorded to date. The observed variability of the two PRSs exhibits no significant difference in amplitude across both short and long timescales. We found that the radio-derived star formation rates of the two FRB hosts are significantly higher than those measured by the optical $H_{\alpha}$ emissions, indicating that their host galaxies are highly obscured or most radio emissions are not from star formation processes. The observed timescale of PRS flux evolution constrained the magnetic field of FRB 20121102A with $B_\parallel\gtrsim1~{\rm mG}$ and FRB 20190520B with $B_\parallel\gtrsim0.1~{\rm mG}$.

James Webb Space Telescope opens a new window to directly probe luminous quasars powered by billion solar mass black holes in the epoch of reionization and their co-evolution with massive galaxies with unprecedented details. In this paper, we report the first results from the deep NIRSpec integral field spectroscopy study of a quasar at $z = 7.5$. We obtain a bolometric luminosity of $\sim$$1.8\times10^{47}$ erg s$^{-1}$ and a black hole mass of $\sim$0.7--2.5$\times10^{9}$ M$_{\odot}$ based on H$\beta$ emission line from the quasar spectrum. We discover $\sim$2 kpc scale, highly blueshifted ($\sim$$-$870 km/s) and broad ($\sim$1400 km/s) [O III] line emission after the quasar PSF has been subtracted. Such line emission most likely originates from a fast, quasar-driven outflow, the earliest one on galactic-scale known so far. The dynamical properties of this outflow fall within the typical ranges of quasar-driven outflows at lower redshift, and the outflow may be fast enough to reach the circumgalactic medium. Combining both the extended and nuclear outflow together, the mass outflow rate, $\sim$300 M$_{\odot}$yr, is $\sim$60%--380% of the star formation rate of the quasar host galaxy, suggesting that the outflow may expel a significant amount of gas from the inner region of the galaxy. The kinetic energy outflow rate, $\sim$3.6$\times10^{44}$ erg s$^{-1}$, is $\sim$0.2% of the quasar bolometric luminosity, which is comparable to the minimum value required for negative feedback based on simulation predictions. The dynamical timescale of the extended outflow is $\sim$1.7 Myr, consistent with the typical quasar lifetime in this era.

We present high-spatial-resolution (0.7 to 1.0 arcsec) submillimeter observations of continuum and molecular lines of CH3OCHO, CH3OCH3, and H2CCO toward 11 high-mass star-forming regions using the Atacama Large Millimetre/submillimetre Array (ALMA). A total of 19 separate cores from 9 high-mass star-forming regions are found to be line-rich, including high-, intermediate-, and low-mass line-rich cores. The three molecules are detected in these line-rich cores. We map the emission of CH3OCHO, CH3OCH3, and H2CCO in 9 high-mass star-forming regions. The spatial distribution of the three molecules is very similar and concentrated in the areas of intense continuum emission. We also calculate the rotation temperatures, column densities, and abundances of CH3OCHO, CH3OCH3, and H2CCO under the local thermodynamic equilibrium (LTE) assumption. The abundances relative to H2 and CH3OH, and line widths of the three molecules are significantly correlated. The abundances relative to H2, temperatures and line widths of the three molecules tend to be higher in cores with higher mass and outflows detected. The possible chemical links of the three molecules are discussed.

GRAMS (Gamma-Ray and AntiMatter Survey) is a next-generation balloon/satellite experiment utilizing a LArTPC (Liquid Argon Time Projection Chamber), to simultaneously target astrophysical observations of cosmic MeV gamma-rays and conduct an indirect dark matter search using antimatter. While LArTPCs are widely used in particle physics experiments, they have never been operated at balloon altitudes. An engineering balloon flight with a small-scale LArTPC (eGRAMS) was conducted on July 27th, 2023, to establish a system for safely operating a LArTPC at balloon altitudes and to obtain cosmic-ray data from the LArTPC. The flight was launched from the Japan Aerospace Exploration Agency's (JAXA) Taiki Aerospace Research Field in Hokkaido, Japan. The total flight duration was 3 hours and 12 minutes, including a level flight of 44 minutes at a maximum altitude of 28.9~km. The flight system was landed on the sea and successfully recovered. The LArTPC was successfully operated throughout the flight, and about 0.5 million events of the cosmic-ray data including muons, protons, and Compton scattering gamma-ray candidates, were collected. This pioneering flight demonstrates the feasibility of operating a LArTPC in high-altitude environments, paving the way for future GRAMS missions and advancing our capabilities in MeV gamma-ray astronomy and dark matter research.

Sulfur-bearing molecules are commonly detected in dense cores within star-forming regions, but the total sulfur budget is significantly low, when compared to the interstellar medium (ISM) value. The properties of sulfur-bearing molecules are not well understood due to the absence of large sample studies with uniform observational configurations. To deepen our understanding of this subject, we conducted a study using ALMA 870 \micron~observations of 11 massive protoclusters. By checking the spectra of 248 dense cores in 11 massive protoclusters, a total of 10 sulfur-bearing species (CS, SO, \htcs, NS, \sot, \ttso, \tfsot, \ttsot, \seoo, \octfs) were identified. The parameters including systemic velocities, line widths, gas temperatures, column densities, and abundances were derived. Our results indicate that SO appears to be more easily detected in a wider range of physical environments than \htcs, despite these two species show similarities in gas distributions and abundances. \tfsot~and \htcs~are good tracers of the temperature of sulfur-bearing species, in which \htcs~traces the outer warm envelope and \tfsot~is associated with high-temperature central-regions. High-mass star-forming feedback (outflow and other non-thermal motions) significantly elevates the sulfur-bearing molecular abundances and detection rates specifically for \sot~and SO. A positive correlation between the \sot~abundance increasing factor ($F$) and temperatures suggests that \sot~could serve as a sulfur reservoir on the grain mantles of dense cores and then can be desorbed from dust to gas phase as the temperature rises. This work shows the importance of a large and unbiased survey to understand the sulfur depletion in dense cores.

Most massive galaxies host a supermassive black hole at their centre. Matter accretion creates an active galactic nucleus (AGN), forming a relativistic particle wind. The wind heats and pushes the interstellar medium, producing galactic-wide outflows. Fast outflows remove the gas from galaxies and quench star formation, and while slower ($v<500$ km s$^{-1}$) outflows are ubiquitous, their effect is less clear but can be both positive and negative. We wish to understand the conditions required for positive feedback. We investigated the effect that slow and warm-hot outflows have on the dense gas clouds in the host galaxy. We aim to constrain the region of outflow and cloud parameter space, if any, where the passage of the outflow enhances star formation. We used numerical simulations of virtual `wind tunnels' to investigate the interaction of isolated turbulent spherical clouds ($10^{3;4;5}$ M$_{\odot}$) with slow outflows ($10$ km s$^{-1} - 400$ km s$^{-1}$) spanning a wide range of temperatures ($10^{4;5;6}$ K). We find that warm outflows compress the clouds and enhance gas fragmentation at velocities ${\leq}200$ km s$^{-1}$, while hot ($T_{\rm out} = 10^6$ K) outflows increase fragmentation rates even at moderate velocities of $400$ km s$^{-1}$. Cloud acceleration, on the other hand, is typically inefficient, with dense gas only attaining velocities of ${<}0.1 v_{\rm out}$. We suggest three primary scenarios where positive feedback on star formation is viable: stationary cloud compression by slow outflows in low-powered AGN, sporadic enhancement in shear flow layers formed by luminous AGN, and self-compression in fragmenting AGN-driven outflows. Our results are consistent with current observational constraints and with previous works investigating triggered star formation in these disparate domains.

Fast radio burst (FRB) is a type of extragalactic radio signal characterized by millisecond duration, extremely high brightness temperature, and large dispersion measure. It remains a mystery in the universe. Advancements in instrumentation have led to the discovery of 816 FRB sources and 7622 bursts from 67 repeating FRBs now. This field is undergoing rapid development, rapidly advancing our understanding of the physics of FRBs as new observational data accumulates. The accumulation of data has also promoted our exploration of our universe. In this review, we summarize the statistical analysis and cosmological applications using large samples of FRBs, including the energy functions, the waiting time distributions of repeating FRBs, the probe of "missing baryons" and circumgalactic medium in the universe, measurements of cosmological parameters, exploration of the epoch of reionization history, and study of the gravitational lensing of FRBs.

Sulfur-bearing species play critical roles in atmospheric physical-chemical processes, atmosphere-surface interactions, and the geological evolution of Venus. This chapter provides a comprehensive overview of (1) Instrumental data on the abundance and speciation of sulfur in atmospheric and crustal materials, (2) the behavior of sulfur-bearing species in the mesosphere, clouds, and lower atmosphere, (3) chemical and mineralogical aspects of atmosphere-surface interactions, (4) the fate of sulfur during the formation, differentiation, and geological evolution of Venus, including volcanic degassing, gas-solid reactions at the surface, a putative aqueous period, and subsequent evolution. The chapter also outlines outstanding questions and discusses further exploration of Venus in the context of sulfur-relevant investigations.

Optical spectra of the Very Late Thermal Pulse (VLTP) object V4334 Sgr have shown a rapidly changing spectrum resulting from shocks in the outflow, which created a new bipolar nebula inside the old nebula. We see C II and C III emission lines emerging typical of a [WC 11-10]-type star. The strong increase of [O III] and [S III] emission lines indicate the possible onset of photoionisation in the new ejecta.

We live in an exoplanet revolution, with more than 5,000 exoplanets detected to date. Our ability to characterise individual exoplanets is constantly improving, with exquisite mass and radius measurements for an ever-growing sample of planets, complimented by atmospheric characterisation of lower and lower mass planets. This chapter outlines a complimentary set of observations that uniquely provide bulk elemental compositions for exoplanetary material. Absorption features from metals, including Mg, Fe, Si, O, Ca, Al, Ni and Ti in the white dwarf photosphere characterise the composition of accreted planetary material. These observations highlight the diversity in composition across exoplanetary systems including volatile content and probe key geological processes including the formation of iron cores. Thanks to the many white dwarfs identified by the space satellite {\it Gaia}, a revolution in the spectroscopic characterisation of white dwarfs is underway.

Most existing star-galaxy classifiers depend on the reduced information from catalogs, necessitating careful data processing and feature extraction. In this study, we employ a supervised machine learning method (GoogLeNet) to automatically classify stars and galaxies in the COSMOS field. Unlike traditional machine learning methods, we introduce several preprocessing techniques, including noise reduction and the unwrapping of denoised images in polar coordinates, applied to our carefully selected samples of stars and galaxies. By dividing the selected samples into training and validation sets in an 8:2 ratio, we evaluate the performance of the GoogLeNet model in distinguishing between stars and galaxies. The results indicate that the GoogLeNet model is highly effective, achieving accuracies of 99.6% and 99.9% for stars and galaxies, respectively. Furthermore, by comparing the results with and without preprocessing, we find that preprocessing can significantly improve classification accuracy (by approximately 2.0% to 6.0%) when the images are rotated. In preparation for the future launch of the China Space Station Telescope (CSST), we also evaluate the performance of the GoogLeNet model on the CSST simulation data. These results demonstrate a high level of accuracy (approximately 99.8%), indicating that this model can be effectively utilized for future observations with the CSST.

Coronal heating refers to the physical processes that shape and structure the corona of the Sun and are responsible for its multi-million Kelvin temperatures. These processes are revealed in a number of different observational manifestations and have been studied on theoretical grounds in great detail over the last eight decades. The aim of this Chapter is to give an account of some of those manifestations and to discuss relevant physics that we believe is responsible for them. Coronal heating is closely connected to other magnetohydrodynamic (MHD) processes occurring in the solar plasma and described in this book such as waves, shocks, instabilities, and magnetic reconnection.

Cen X-3 is a compact, high-mass X-ray binary (HMXRB), likely powered by Roche lobe overflow. We present a phase-resolved X-ray spectral and timing analysis of a target of opportunity \textit{Chandra} observation made during a low-flux to high-flux transition. The high-resolution spectra allow us to delve into the events that occurred during this episode. The spectrum is described by a single black body absorbed by a local column density of the order of $10^{23-24}$ cm$^{-2}$, which is one to two orders of magnitude higher than found for previous analyses of data taken at similar orbital phases. Such a large column produces a Compton shoulder in the Fe K$\alpha$ line. The transition appears to be caused by the onset of efficient cooling, which cools the plasma by 10 million degrees in just 10 ks, allowing matter to enter the magnetosphere. This happens after a major disturbance, probably the arrival of a train of wind clumps with individual masses in the range $10^{19-20}$ g. This train moves ballistically in an eccentric orbit around the NS, producing a distinctive Doppler modulation in the \ion{Fe}{xxv} line.

We investigate the radial dependence of the scaling relations of dust attenuation in nearby galaxies using integral field spectroscopy (IFS) data from MaNGA. We identify ionized gas regions of kpc sizes from MaNGA galaxies, and for each region we estimate both the stellar attenuation $E(B-V)_{\rm star}$ and gas attenuation $E(B-V)_{\rm gas}$. We then quantify the correlations of 15 regional/global properties with $E(B-V)_{\rm gas}$ and $E(B-V)_{\rm star}$, using both the feature importance obtained with the Random Forest regression technique and the Spearman correlation coefficients. The importance of stellar mass, metallicity and nebular velocity dispersion found previously from SDSS-based studies can be reproduced if our analysis is limited to the central region of galaxies. The scaling relations of both $E(B-V)_{\rm gas}$ and $E(B-V)_{\rm star}$ are found to strongly vary as one goes from the galactic center to outer regions, and from H$\alpha$-bright regions to H$\alpha$-faint regions. For $E(B-V)_{\rm gas}$, [NII]/[SII] is top ranked with a much higher correlation coefficient than any other property at $0<R\lesssim R_e$, while [OIII]/[OII] outperforms [NII]/[SII] as the leading property in the outermost region. For $E(B-V)_{\rm star}$, stellar age shows the strongest correlation with no/weak dependence on radial distance, although $\rm \Sigma_{H\alpha}$ and sSFR present similarly strong correlations with $E(B-V)_{\rm star}$ in the galactic center. We find H$\alpha$-bright regions to generally show stronger correlations with $E(B-V)_{\rm gas}$, while H$\alpha$-faint regions are more strongly correlated with $E(B-V)_{\rm star}$, although depending on individual properties and radial distance. The implications of our results on studies of high-$z$ galaxies are discussed.

Jupiter's icy moon Ganymede has a tenuous exosphere produced by sputtering and possibly sublimation of water ice. To date, only atomic hydrogen and oxygen have been directly detected in this exosphere. Here, we present observations of Ganymede's CO$_2$ exosphere obtained with the James Webb Space Telescope. CO$_2$ gas is observed over different terrain types, mainly over those exposed to intense Jovian plasma irradiation, as well as over some bright or dark terrains. Despite warm surface temperatures, the CO$_2$ abundance over equatorial subsolar regions is low. CO$_2$ vapor has the highest abundance over the north polar cap of the leading hemisphere, reaching a surface pressure of 1 pbar. From modeling we show that the local enhancement observed near 12 h local time in this region can be explained by the presence of cold traps enabling CO$_2$ adsorption. However, whether the release mechanism in this high-latitude region is sputtering or sublimation remains unclear. The north polar cap of the leading hemisphere also has unique surface-ice properties, probably linked to the presence of the large atmospheric CO2 excess over this region. These CO2 molecules might have been initially released in the atmosphere after the radiolysis of CO$_2$ precursors, or from the sputtering of CO$_2$ embedded in the H$_2$O ice bedrock. Dark terrains (regiones), more widespread on the north versus south polar regions, possibly harbor CO$_2$ precursors. CO$_2$ molecules would then be redistributed via cold trapping on ice-rich terrains of the polar cap and be diurnally released and redeposited on these terrains. Ganymede's CO$_2$ exosphere highlights the complexity of surface-atmosphere interactions on Jupiter's icy Galilean moons.

Prompt emission of GRB 230812B stands out as one of the most luminous events observed by both the Fermi-GBM and LAT. Prompt emission spectral analysis (both time-integrated and resolved) of this burst supports an additional thermal component together with a non-thermal, indicating the hybrid jet composition. The spectral parameters alpha, Ep, and kT of the best-fit Band+Blackbody model show a tacking behaviour with the intensity. Further, the low energy afterglow emission is consistent with the synchrotron emission from the external forward shock in the ISM medium. LAT detected very high energy emission (VHE) deviating from the synchrotron mechanism, possibly originating from the Lorentz boosting of prompt emission photons by accelerated electrons in the external shock via Inverse Compton (IC) or Synchrotron Self Compton (SSC) emission mechanisms. The comparison of the prompt and afterglow emission properties of this burst revealed that, unlike the bright prompt emission, the afterglow of GRB 230812B is fainter than the other SN-detected bright bursts (GRB 130427A and GRB 171010A) at a similar redshift.

We investigate the null test of cosmic accelerated expansion by using the Baryon Acoustic Oscillation (BAO) measurements released by the Dark Energy Spectroscopic Instrument, and we find that the latest BAO data alone can provide strong model-independent evidence for the existence of accelerated expansion in the Universe. Using Gaussian Process reconstruction, we derive the deceleration parameter $q(z)$ from the BAO data, revealing that accelerated expansion persisted until $z \lesssim 0.833$. By further incorporating data from Cosmic Chronometers and 6 expansion rate measured by type Ia supernovae, we find that accelerated expansion continued until $z \lesssim 0.417$.

Weak gravitational lensing (WL) surveys provide insight into the matter distribution over an extensive range of scales. Current WL results are in mild tension with cosmic microwave background measurements from the early Universe. Reconstructing the matter power spectrum from their measurements instead of condensing the information into a single cosmological parameter may help locate the origin of these differences. To investigate the cosmic shear measurements of Stage-III WL surveys, we compare their tomographic data by assuming a simple parametric model for the matter power spectrum. The model allows the comparison of surveys with different characteristics and, in an agnostic approach, gives insight into the shape of the matter power spectrum preferred by the data without assuming a cosmological model. For the matter power spectrum, we assume a double power law model in scale factor and wavenumber. The best-fit amplitude and exponents are inferred in an MCMC analysis. We identify the scales to which the data is most sensitive. We test the sensitivity to different assumptions of the intrinsic alignment strength. We find that Stage-III surveys' constraining power on the power spectrum shape and evolution is still limited. Most information can be summarised as an overall amplitude at a pivot point in wave number and scale factor, while constraints on the power law indices are considerably weaker. Nevertheless, all surveys prefer a weaker rate of growth from $z=$ 0.5 to 0.1 than predicted. The assumed intrinsic alignment strength is found to have no significant impact on the measured parameters and goodness of fit. Direct estimates of the matter power spectrum from Stage-III weak lensing surveys can, in principle, be used to locate the physical origin of the $S_8$ tension. We present a simple methodology for the first steps in this direction but find that current constraints are still weak.

Based on TESS observations of a $\delta$ Scuti variable WASP-33 obtained in 2019 and 2022, we thoroughly investigate the power spectrum of this target photometric flux and construct a statistically exhaustive model for its variability. This model contains $30$ robustly justified harmonics detected in the both TESS sectors simultaneously, $13$ less robust harmonics detected in a single TESS sector, a red noise and a quasiperiodic noise terms. This allowed us to greatly improve the accuracy of the exoplanet WASP-33 b transit timings, reducing the TTV residuals r.m.s. drastically, by a factor of $3.5$, from $63$ s to $18$ s. Finally, our analysis does not confirm existence of a detectable orbital phase variation claimed by von Essen et al. (2020) based on WASP-33 TESS photometry of 2019.

The discovery of phosphine in Venus' atmosphere provides lessons for the search for life. The detection has survived all challenges and has acquired independent support from archival data from PVP. The presence of phosphine in Venus' oxidising environment is perplexing, and comprehensive studies rule out all known abiotic sources. More data is needed to understand the origin of phosphine, leading to JCMT-Venus, a long term atmospheric monitoring programme. This can find how phosphine varies in relation to other species providing clues to its origin. We present the latest JCMT-Venus results. The discovery and subsequent papers were explicit that they did not constitute evidence for life, only of phosphine. Media and public reaction to the discovery and its implications provide lessons for future life searches, as does the reaction of the scientific community. How this was handled by the team, media, and general public will be reviewed.

Recent observations by the James Webb Space Telescope (JWST) have revealed a previously hidden population of extremely bright and compact objects between redshifts of $z \sim 4$ and $z \sim 10$. Given their extreme red colouring in the observed frame these galaxies have been dubbed Little Red Dots (LRDs). The aim of this project was to identify LRDs using photometric data from previously uninvestigated JWST datasets and to estimate their AGN fractions by fitting the spectral energy distribution of each galaxy against well calibrated templates using CIGALE. We identified a list of potential LRDs using a single colour cut of F444W-F277W $>$1.5 mag and by applying a morphological analysis. We used EAZY to estimate the (photometric) redshift and CIGALE to estimate the AGN fraction of each LRD. Overall, we identified 14 LRDs, applying accurate SED fits to 11 of them. We found that 7 of them had a high AGN fraction (with the AGN component generating more than 50\% of the observed flux), a further two LRDs had AGN contribution in excess of approximately 40\%. In total nine LRDs (our of 14) are likely to have a supermassive black hole in their centre. Interestingly, the three LRDs which could not be well fit by CIGALE displayed extremely high photometric redshifts ($z_{phot} \gtrsim 11$) and require further analysis (and may also host a supermassive black hole in their centre).

Previous as well as recent observations by ISO, Spitzer, AKARI, SOFIA, JWST etc. have revealed various characteristics of mid-infrared emission bands between 3-20 micron. Subsequently, several forms of organics including Polycylic Aromatic Hydrocarbons (PAHs)/PAHs-like molecules are proposed as carriers for these bands. Deuterated PAH (PAD) is one such substituted PAH, which is proposed as a potential candidate carrier for weak emission bands at 4.4 and 4.65 micron, detected towards few astronomical targets and are characteristics of aromatic and aliphatic C-D stretching modes in a PAD molecule, respectively. However, the 4.4 micron band is not widely detected. In order to validate PADs as carriers for mid-infrared emission bands, an additional alternative way is crucial. If PAHs are deuterated or deuteronated, they should also possess an inherent signature from the C-D out of plane (C-Doop) vibrations, which are at the longer wavelength side. In this report, features due to C-Doop modes belonging to PAHs with single to multiple deuteration in the same ring are reported by performing quantum-chemical calculations. We found that some of the C-Doop vibrations appear at 14-19 micron range, which does not overlap with the region attributed to C-Hoop modes. Also, the strength of C-Doop modes is not proportional to D/H in PAHs. In addition, new C-Hoop modes also appear due to the creation of new C-H bonds upon deuteration of duet, trio, and quartet C-H sites. We discuss the efficiency and usefulness of these bands to constrain the form of PAHs emitting mid-infrared emission bands.

We present our analysis of MAXI J1813-095 during its hard state ``stalled'' outburst in 2018. This self-consistent analysis has been carried out using \NICER, \Swift, \Chandra, and {\NuSTAR} throughout seven observations of MAXI J1813-095. We find a relativistic iron line at $\sim$6.5 keV from the inner region of the accretion disk. Our results are consistent with a slightly truncated disk or non-truncated disk for an inner radius of $\sim$2$R_\mathrm{g}$ and minimum spin of $>$0.7 with a best value of $\sim0.9$, assuming $R_\mathrm{in}$ reaches the innermost stable circular orbit at $\it{L_\mathrm{x}}$ $\sim$ 1\% $\it{L_\mathrm{Edd}}$. We analyzed MAXI J1813-095 over its outburst employing a spectral model which self-consistently couples the seed disk photons to the Comptonization and reflection components, also inclusive of reflection Comptonization. The unique aspect of this work is a reflection fraction of order unity, which is significantly higher than previous studies of this source, and is a consequence of applying the self-consistent disk-Comptonization-reflection spectral model. Other key parameters such as inclination and inner radius are found to be consistent with other works. works.

Relativistic magnetic reconnection studies have focused on symmetric configurations so far, where the upstream plasma has identical properties on each side of the layer. The boundary layer between a relativistic jet and an accretion flow forming around a supermassive black hole may present an asymmetric configuration in terms of plasma composition, bulk velocity, temperature and magnetization. In this work, we aim to conduct the first study of relativistic magnetic reconnection where the upstream plasma is composed of electron-positron pairs on one side, and electrons and ions on the other. We also investigate the role of a relativistic symmetric shear flow applied along the reconnecting field lines. We simulate magnetic reconnection using two-dimensional particle-in-cell simulations. The initial setup is adapted from a classic Harris layer without guide field, modified to accommodate plasma-composition and shear asymmetries in the upstream medium. For a composition-asymmetric setup, we find that the reconnection dynamics is driven by the electron-ion side, which is the plasma with the lowest magnetization. The energy partition favors accelerating ions at the expense of electrons even more than in a corresponding symmetric setup. With respect to shear, a super-Alfvénic upstream decreases the laboratory-frame reconnection rate, but, unlike in non-relativistic studies, does not shut off reconnection completely. The asymmetries examined in this work diminish the overall efficiency of electron acceleration relative to corresponding symmetric configurations. In the context of a black hole jet-disk boundary, asymmetric reconnection alone is probably not efficient at accelerating electrons to very high energies, but it might facilitate plasma mixing and particle injection for other acceleration channels at the interface.

The curvature perturbation in a model of constant-roll (CR) inflation is interpreted in view of the logarithmic duality discovered in Ref. [1] according to the $\delta N$ formalism. We confirm that the critical value $\beta:=\ddot{\varphi}/(H\dot{\varphi})=-3/2$ determining whether the CR condition is stable or not is understood as the point at which the dual solutions, i.e., the attractor and non-attractor solutions of the field equation, are interchanged. For the attractor-solution domination, the curvature perturbation in the CR model is given by a simple logarithmic mapping of a Gaussian random field, which can realise both the exponential tail (i.e., the single exponential decay) and the Gumbel-distribution-like tail (i.e., the double exponential decay) of the probability density function, depending on the value of $\beta$. Such a tail behaviour is important for, e.g., the estimation of the primordial black hole abundance.

Ultra hot Jupiters (gas giants, Teq>2000 K) are intriguing exoplanets due to their extreme atmospheres. Their torrid daysides can be characterised using ground-based high-resolution emission spectroscopy. We search for signatures of neutral and singly ionised iron (Fe I and Fe II) in the dayside of the ultra hot Jupiter WASP-76 b, as these species were detected via transmission spectroscopy in this exoplanet. Furthermore, we aim to confirm the existence of a thermal inversion layer, which has been reported in previous studies, and attempt to constrain its properties. We observed WASP-76 b on four epochs with ESPRESSO at the VLT, at orbital phases shortly before and after the secondary transit, when the dayside is in view. We present the first analysis of high-resolution optical emission spectra for this exoplanet. We compare the data to synthetic templates from petitRADTRANS, using cross-correlation function techniques. We detect a blueshifted (-4.7+-0.3 km/s) Fe I emission signature on the dayside of WASP-76 b at 6.0-sigma. The signal is detected independently both before and after the eclipse, and blueshifted in both cases. The presence of iron emission features confirms the existence of a thermal inversion layer. Fe II was not detected, possibly because this species is located in the upper layers of the atmosphere, which are more optically thin. Thus the Fe II signature on the dayside of WASP-76 b is too weak to be detected with emission spectroscopy. We propose that the blueshifted Fe I signature is created by material rising from the hot spot to the upper layers of the atmosphere, and discuss possible scenarios related to the position of the hotspot. This work unveils some of the dynamic processes ongoing on the dayside of WASP-76 b through the analysis of the Fe I signature from its atmosphere, and complements previous knowledge obtained from transmission studies.

Non-radiative shocks accelerate particles and heat astrophysical plasmas. While supernova remnants are the most well-studied example, neutron star (NS) bow shocks are also non-radiative and Balmer-dominated. NS bow shocks are likely ubiquitous in the interstellar medium due to their large speeds imparted at birth, and they are thought to be a discrete source population contributing to the Galactic cosmic ray spectrum. To date, nine NS bow shocks have been directly observed in H$\alpha$ images. Most of these shocks have been characterized using narrowband H$\alpha$ imaging and slit spectroscopy, which do not resolve the multi-component velocity structure of the shocks and their spatial geometry. Here we present integral field spectroscopy of three NS bow shocks: J0742$-$2822, J1741$-$2054, and J2225$+$6535 (the Guitar Nebula). We measure the shock properties simultaneously in four dimensions: the 2D projected shock morphology, the radial velocity structure, and the H$\alpha$ flux. The broad-to-narrow line ratio ($I_{\rm b}/I_{\rm n}$) is inferred from radial velocity profiles, and for J1741$-$2054 the narrow line is detected in multiple regions of the shock. The inferred line ratios and widths suggest that NS bow shocks represent a low shock velocity regime in which electron-ion temperature equilibration is low, contrary to the trend seen in supernova remnants. While the low velocity regime is poorly captured by state-of-the-art simulations, these results may imply electron injection efficiency is lower for bow shocks than their counterparts in supernova remnants.

High-cadence surveys of the sky are revealing that a large fraction of red-supergiant (RSG) stars, which are progenitors of Type II-Plateau (II-P) supernovae (SNe), explode within circumstellar material (CSM). Such SNe II-P/CSM exhibit considerable diversity, with interaction signatures lasting from hours to days, potentially merging with the Type IIn subclass for which longer-duration interaction typically occurs. To tackle this growing sample of transients and to understand the pre-SN mass loss histories of RSGs, we train on the highest quality, spectropolarimetric observations of a young Type IIn SN taken to date: Those of SN1998S at ~5d after explosion. We design an approach based on a combination of radiation hydrodynamics with HERACLES and polarized radiative transfer with CMFGEN and LONG_POL. The adopted asymmetries are based on a latitudinal, depth- and time-independent, scaling of the density of 1D models of SNe II-P/CSM (e.g., model r1w6b with a `wind' mass-loss rate of 0.01Msun/yr used for SN2023ixf). For a pole-to-equator density ratio of five, we find that the polarization reaches, and then remains for days, at a maximum value of 1.0, 1.4, and 1.8% as the CSM extent is changed from 6, to 8 and 10x10^14cm. The polarization is independent of wavelength away from funnel-shaped depolarizations within emission lines. Our models implicate a significant depolarization at line cores, which we use to constrain the interstellar polarization of SN1998S. Our 2D, prolate ejecta models with moderate asymmetry match well the spectropolarimetric observations of SN1998S at 5d, supporting a polarization level of about ~2%. This study provides a framework for interpreting future spectropolarimetric observations of SNe II-P/CSM and SNe IIn and fostering a better understanding of the origin of their pre-SN mass loss.

We simulate mergers between star clusters embedded within their natal giant molecular cloud. We extract initial conditions from cloud-scale simulations of cluster formation and introduce different prescriptions for primordial binaries. We find that simulations that do not include primordial binaries result in a larger fraction of unbound stars than simulations which include a prescription for binaries based on observations. We also find a preferred direction of motion for stars that become unbound during the merger. Sub-cluster mergers within realistic gas environments promote binary disruption while mergers between idealized, gas-rich spherical clusters do not produce the same disruption. Binary systems with smaller semi-major axes are disrupted in simulations of sub-cluster mergers within their natal environment compared to simulations that do not include the realistic gas environment. We conclude that binary disruption and the production of an anisotropic distribution of unbound stars are the natural consequences of sub-cluster mergers during star cluster assembly.

We present the Near-Ultraviolet eXplorer (NUX), which will consist out of 4 small (36 cm diameter) ground-based telescopes that are optimized for the shortest wavelengths that are detectable from Earth (i.e., the near-UV [NUV] wavelength range of 300-350 nm). Each telescope will have a field-of-view of ~17 square degrees sampled at ~2.6"/pixel, and will reach a NUV magnitude (AB) of 20 in 2.5 minutes exposures (in dark time). The goal of NUX is to improve our understanding of the physical processes that power fast (days) to very fast (hours) hot transients, such as shock-breakout and shock-cooling emission of supernovae and the electromagnetic counterparts of gravitational wave events. Each telescope will be an off-the-shelf 14" Celestron RASA telescope, retrofitted with NUV optics. We have already demonstrated that the normal Schmidt corrector of this telescope can be replaced by a custom made one consisting of NUV transparent glass. Currently, a prototype NUX telescope is being fully assembled to demonstrate the technical and scientific feasibility of the NUX concept. Site tests will be held (in 2025/2026) at La Silla, Chile, to determine the NUV characteristics of the atmosphere at this site.

Obtaining tight constraints on primordial non-Gaussianity (PNG) is a key step in discriminating between different models for cosmic inflation. The constraining power from large-scale structure (LSS) measurements is expected to overtake that from cosmic microwave background (CMB) anisotropies with the next generation of galaxy surveys including the Dark Energy Spectroscopic Instrument (DESI) and Euclid. We consider whether Density-Split Clustering (DSC) can help improve PNG constraints from these surveys for local, equilateral and orthogonal types. DSC separates a surveyed volume into regions based on local density and measures the clustering statistics within each environment. Using the Quijote simulations and the Fisher information formalism, we compare PNG constraints from the standard halo power spectrum, DSC power spectra and joint halo/DSC power spectra. We find that the joint halo/DSC power spectra outperform the halo power spectrum by factors of $\sim$ 1.4, 8.8, and 3.6 for local, equilateral and orthogonal PNG, respectively. This is driven by the higher-order information that DSC captures on small scales. We find that applying DSC to a halo field does not allow sample variance cancellation on large scales by providing multiple tracers of the same volume with different local PNG responses. Additionally, we introduce a Fourier space analysis for DSC and study the impact of several modifications to the pipeline, such as varying the smoothing radius and the number of density environments and replacing random query positions with lattice points.

The Small Magellanic Cloud (SMC) is an irregular dwarf galaxy that has recently undergone an interaction with the Large Magellanic Cloud. The young massive stars in the SMC formed in the disturbed low-metallicity environment are important targets in astrophysics. We present a catalog of $\sim$ 76,800 far ultraviolet (FUV) sources towards the SMC detected using the Ultra Violet Imaging Telescope (UVIT) onboard AstroSat. We created an FUV catalog with $\sim$ 62900 probable SMC members which predominantly comprise main-sequence, giant, and subgiant stars. We selected 4 young populations (Young 1, Young 2, Young 3, and Blue Loop (BL) stars) identified from the Gaia optical color-magnitude diagram to study the morphology and kinematics of the young SMC using this catalog. We detect a clumpy morphology with a broken bar, a shell-like structure, and the inner SMC Wing for the 4 stellar populations. The eastern region and the northeastern regions are mainly populated by Young 1, 2, and 3. The central region predominantly has the Young 2 and 3 populations, whereas the SW has BL stars, Young 2 and 3. The 2-D kinematic study using proper motion (PM) reveals that Young 2 and 3 populations show two kinematically distinct sub-populations with low and high PM dispersion, whereas the Young 1 and BL stars show two kinematically distinct populations with low dispersion. Our analysis points to a kinematic disturbance along the RA direction for stars younger than $\sim$ 150 Myr located in the eastern region, with no significant disturbance along the Declination.

We analyze data from the IRAS, WISE, and Planck satellites, revealing an unresolved dust condensation at the center of the Fourcade-Figueroa galaxy (ESO270-G017), which may correspond to a forming nucleus. We model the condensation's continuum spectrum in the spectral range from 3 to 1300 microns using the DUSTY code. The best-fit model, based on the Chi-square test, indicates that the condensation is a shell with an outer temperature of T_out ~ 12 K and an inner boundary temperature of T_i ~ 500 K. The shell's outer radius is r_o = 86.2 pc, and the inner cavity radius is r_i = 0.082 pc. The condensation produces an extinction A_V = 50 mag and its luminosity is L_c = 1.08E34 W, which would correspond to a burst of massive star formation approximately similar to the central 5 pc of R136 in the LMC and NGC3603, the ionizing cluster of a giant Carina arm HII region. The comparison with Normal, Luminous, and Ultra-Luminous Infrared Galaxies leads us to consider this obscured nucleus as the nearest and weakest object of this category.

Theoretical studies of giant planet formation suggest that substantial quantities of metals - elements heavier than hydrogen and helium - can be delivered by solid accretion during the envelope-assembly phase. This metal enhancement process is believed to diminish as a function of planet mass, leading to predictions for a mass-metallicity relationship. This picture is supported by the abundance of CH$_4$ in solar system giant planets, which is unaffected by condensation, unlike H$_2$O. However, all of the solar system giants exhibit some evidence for stratification of metals outside of their cores. In this context, two fundamental questions are whether metallicity of giant planets inferred from observations of the outer envelope layers represents their bulk metallicities, and if not, how are metals distributed within these planets. Comparing the mass-metallicity relationship inferred for solar system giants with various tracers of exoplanet metallicity has yielded a range of results. There is evidence of a solar-system-like mass-metallicity trend using bulk density estimates of exoplanets. However, transit-spectroscopy-based tracers of exoplanet metallicity, which probe only the outer layers of the envelope, are less clear about a mass-metallicity trend and radial composition gradients. The large number of known exoplanets enables statistical characterization. We develop a formalism for comparing both the metallicity inferred for the outer envelope and the metallicity inferred using the bulk density and show this combination may offer insights into metal stratification within planetary envelopes. Thus, future exoplanet observations with JWST and Ariel will be able to shed light on the conditions governing radial composition gradients in exoplanets and, perhaps, provide information about the factors controlling stratification and convection in our solar system gas giants.

Based on the recently solidified notion that the jittering jets explosion mechanism (JJEM) is the primary explosion mechanism of core-collapse supernovae (CCSNe), I estimate some typical properties of the jittering jets. From the imprints of jittering jets in the outskirts of some CCSN remnants, I estimate the half-opening angles of jittering jets that shape CCSN remnants to be ~1-10 degrees. I also estimate that intermittent accretion disks around the newly born neutron star (NS) can launch jets after they live for only several times their orbital period around the NS. To operate, the JJEM requires the intermittent accretion disks that launch the jets to amplify the magnetic fields in a dynamo and the magnetic fields to reconnect to release their energy rapidly. I estimate the width of magnetic field reconnection zones to be ~0.005r~0.1km near the surface of the NS. This width requires a numerical resolution several times smaller than the resolution of present CCSN simulations. I argue, therefore, that existing simulations of the CCSN explosion mechanism are still far from correctly simulating CCSN explosions.

Gas-phase abundance ratios between \ce{C2H4O2} isomers methyl formate (MF), glycolaldehyde (GA), and acetic acid (AA) are typically on the order of 100:10:1 in star-forming regions. However, an unexplained divergence from this neat relationship was recently observed towards a collection of sources in the massive protocluster NGC 6334I; some sources exhibited extreme MF:GA ratios, producing a bimodal behavior between different sources, while the MF:AA ratio remained stable. Here, we use a three-phase gas-grain hot-core chemical model to study the effects of a large parameter space on the simulated \ce{C2H4O2} abundances. A combination of high gas densities and long timescales during ice-mantle desorption ($\sim$125--160~K) appears to be the physical cause of the high MF:GA ratios. The main chemical mechanism for GA destruction occurring under these conditions is the rapid adsorption and reaction of atomic H with GA on the ice surfaces before it has time to desorb. The different binding energies of MF and GA on water ice are crucial to the selectivity of the surface destruction mechanism; individual MF molecules rapidly escape the surface when exposed by water loss, while GA lingers and is destroyed by H. Moderately elevated cosmic-ray ionization rates can increase absolute levels of COM production in the ices and increase the MF:GA ratio, but extreme values are destructive for gas-phase COMs. We speculate that the high densities required for extreme MF:GA ratios could be evidence of COM emission dominated by COMs desorbing within a circumstellar disk.

When interpreting spectropolarimetric observations of the solar atmosphere, wavelength variations of the emergent intensity and polarization translate into information on the depth stratification of physical parameters. We aim to quantify how the information content contained in a representative set of polarized spectra depends on the spectral resolution and spectral sampling. We use a state-of-the-art numerical simulation of a sunspot to synthesize polarized spectra of magnetically sensitive neutral iron lines. We then apply various degrees of spectral degradation to the synthetic spectra and analyze the impact on its dimensionality using PCA and wavelet decomposition. Finally, we apply the SIR code to the degraded synthetic data, to assess the effect of spectral resolution on the inferred parameters. We find that regions with strong magnetic fields where convection is suppressed produce less complex Stokes profiles. On the other hand, regions with strong gradients give rise to more complex Stokes profiles that are more affected by spectral degradation. The degradation also makes the inversion problem more ill-defined, so inversion models with a larger number of free parameters overfit and give wrong estimates. The impact of spectral degradation depends on multiple factors, including spectral resolution, noise level, line spread function (LSF) shape, complexity of the solar atmosphere, and the degrees of freedom in our inversion methods. Having a finely sampled spectrum may be more beneficial than achieving a higher signal-to-noise ratio per wavelength bin. Considering the inclusion of different spectral lines that can counter these effects, and calibrating the effective degrees of freedom in modeling strategies, are also important considerations. These strategies are crucial for the accurate interpretation and have the potential to offer more cost-effective solutions.