Papers for Wednesday, Jul 20 2022

Elias 2-27 is a young star that hosts an extended, bright and inclined disk of dust and gas. The inclination and extreme flaring of the disk make Elias 2-27 an ideal target to study the vertical distribution of molecules, particularly CN. We directly trace the emission of CN in Elias 2-27 and compare it to previously published CO isotopologue data. CN $N = 3-2$ emission is analyzed in two different transitions $J = 7/2 - 5/2$ and $J = 5/2 - 3/2$, for which we detect two hyperfine group transitions. The vertical location of CN emission is traced directly from the channel maps, following geometrical methods that have been previously used to analyze the CO emission of Elias 2-27. Analytical models are used to parametrize the vertical profile of each molecule and study the extent of each tracer, additionally we compute radial profiles of column density and optical depth. We show that the vertical location of CN and CO isotopologues in Elias 2-27 is layered and consistent with predictions from thermochemical models. A north/south asymmetry in the radial extent of CN is detected and we find that the CN emission is mostly optically thin and constrained vertically to a thin slab at $z/r \sim$0.5. A column density of 10$^{14}$\,cm$^{-2}$ is measured in the inner disk which for the north side decreases to 10$^{12}$\,cm$^{-2}$ and for the south side to 10$^{13}$\,cm$^{-2}$ in the outer regions. In Elias 2-27, CN traces a vertically elevated region above the midplane, very similar to that traced by $^{12}$CO. The inferred CN properties are consistent with thermo-chemical disk models, in which CN formation is initiated by the reaction of N with UV-pumped H$_2$. The observed north/south asymmetry may be caused by either ongoing infall or by a warped inner disk. This study highlights the importance of tracing the vertical location of various molecules to constrain the disk physical conditions.

The recently published Gaia DR3 catalog of 181 327 spectroscopic binaries (SB) includes the Keplerian elements of each orbit, but not the measured radial velocities (RVs) and their epochs themselves. Instead, the catalog lists a few parameters that characterize the robustness of each solution. In this work, we use two external sources to validate the orbits - 17 563 LAMOST DR6 and 6 018 GALAH DR3 stars with measured RVs that have Gaia-SB orbits. We compare the expected RVs, based on the Gaia orbits, with the LAMOST and GALAH measurements. Finding some orbits that are not consistent with these measurements, we constructed a function that estimates the probability of each of the Gaia orbits to be correct, using the published robust parameters. On this basis, we devise a clean but still very large Gaia SB1 sample of 91 740 orbits. The sample differs from the parent sample by the absence of - physically unlikely and hence presumably spurious - short-period binaries with high eccentricity. The clean SB1 sample offers the prospect of thorough statistical studies of the binary population, after careful modeling of the remaining selection effects. As a first step, we point to two possible emerging features - a circularized main-sequence sub-sample, and a paucity of short-period low-mass primary binaries

We present a comparison between the average atomic gas mass, $\langle M_{Atom}\rangle$ (including HI and He), the average molecular gas mass, $\langle M_{Mol}\rangle$, and the average stellar mass, $\langle M_*\rangle$, of a sample of star-forming galaxies at $z\approx0.75-1.45$, to probe the baryonic composition of galaxies in and during the epoch of peak star-formation activity in the universe. The $\langle M_{Atom}\rangle$ values of star-forming galaxies in two stellar-mass matched samples at $z=0.74-1.25$ and $z=1.25-1.45$, were derived by stacking their HI 21cm signals in the GMRT-CAT$z1$ survey. We find that the baryonic composition of star-forming galaxies at $z\gtrsim 1$ is dramatically different from that at $z\approx0$. For star-forming galaxies with $\langle M_*\rangle\approx10^{10} M_\odot$, the contribution of stars to the total baryonic mass, $M_{Baryon}$, is $\approx61\%$ at $z\approx0$, but only $\approx16\%$ at $z\approx1.3$, while molecular gas constitutes $\approx6\%$ of the baryonic mass at $z\approx0$, and $\approx14\%$ at $z\approx1.3$. Remarkably, we find that atomic gas makes up $\approx70\%$ of $M_{Baryon}$ in star-forming galaxies at $z\approx1.3$. We find that the ratio $\langle M_{Atom}\rangle/\langle M_*\rangle$ is higher both at $z\approx1.0$ and at $z\approx1.3$ than in the local Universe, with $\langle M_{Atom}\rangle/\langle M_*\rangle\approx1.0$ at $z\approx1.0$, and $\approx3.3$ at $z\approx1.3$, compared to its value of $\approx0.4$ today. Further, we find that the ratio $\langle M_{Atom}\rangle/\langle M_{Mol}\rangle$ in star-forming galaxies with $\langle M_*\rangle \approx10^{10} M_\odot$ is $\approx2.3$ at $z\approx1.0$ and $\approx5.0$ at $z\approx1.3$. Overall, we find that atomic gas is the dominant component of the baryonic mass of star-forming galaxies at $z\approx1.3$, during the epoch of peak star-formation activity in the universe.

We reassess the historical $L_{X}/L_{Bol}$ relation for early-type stars from a comparison between T-ReX, the Chandra ACIS X-ray survey of the Tarantula Nebula in the LMC, and contemporary spectroscopic analysis of massive stars obtained primarily from VLT/FLAMES, VLT/MUSE and HST/STIS surveys. For 107 sources in common (some host to multiple stars), the majority of which are bolometrically luminous (40% exceed $10^6 L_{\odot}$), we find an average $\log L_{X} /L_{Bol} = -6.90 \pm 0.65$. Excluding extreme systems Mk 34 (WN5h+WN5h), R140a (WC4+WN6+) and VFTS 399 (O9 IIIn+?), plus four WR sources with anomalously hard X-ray components (R130, R134, R135, Mk 53) and 10 multiple sources within the spatially crowded core of R136a, $\log L_{X}/L_{Bol} = -7.00 \pm 0.49$, in good agreement with Galactic OB stars. No difference is found between single and binary systems, nor between O, Of/WN and WR stars, although there does appear to be a trend towards harder X-ray emission from O dwarfs, through O (super)giants, Of/WN stars and WR stars. The majority of known OB stars in the Tarantula are not detected in the T-ReX point source catalogue, so we have derived upper limits for all undetected OB stars for which log $L_{Bol}/L_{\odot} \geq 5.0$. A survival analysis using detected and upper-limit log $L_{X}/L_{Bol}$ values indicates no significant difference between luminous O stars in the LMC and the Carina Nebula. This analysis suggests that metallicity does not strongly influence $L_{X}/L_{Bol}$. Plasma temperatures for single, luminous O stars in the Tarantula ($\overline{kT_{m}}=1.0$ keV) are higher than counterparts in Carina ($\overline{kT_{m}}=0.5$ keV).

The large number of gravitational wave (GW) detections have revealed the properties of the merging black hole binary population, but their formation is still heavily debated. Understanding the imprint of stellar physics on the observable GW population will shed light on how we can use the gravitational wave data, along with other observations, to constrain the poorly understood evolution of massive binaries. We perform a parameter study for the classical isolated binary formation channel in order to better understand how sensitive the properties of the coalescing binary black hole population are on uncertainties related of stable mass transfer phase and stellar winds. We use the population synthesis code SeBa to simulate the evolution of massive binaries on a large range of metallicities. We vary five assumptions: 1 and 2) the mass transfer efficiency and the angular momentum loss during the first mass transfer phase, 3) the mass transfer stability criteria for giant donors with radiative envelopes, 4) the effective temperature at which an evolved star develops a deep convective envelope, and 5) the stellar winds. Our varied parameters have a complex, interrelated effects on the population properties of GW sources. Most notably, the impact of the mass transfer stability criteria parameter depends on the assumed mass transfer efficiency. The uncertainties in the assumed angular momentum loss have significant effects on the relative rates of the two dominant channels. Because of the numerous uncertainties and lack of reliable models direct inference of massive binary physics from gravitational data is not recommended.

We measure the enclosed Milky Way mass profile to Galactocentric distances of $\sim70$ and $\sim50$ kpc using the smooth, diffuse stellar halo samples of Bird et al. The samples are LAMOST and SDSS/SEGUE K giants (KG) and SDSS/SEGUE blue horizontal branch (BHB) stars with accurate metallicities. The 3D kinematics are available through LAMOST and SDSS/SEGUE distances and radial velocities and {\it Gaia} DR2 proper motions. Two methods are used to estimate the enclosed mass: 3D spherical Jeans equation and Evans et al. tracer mass estimator (TME). We remove substructure via the Xue et al. method based on integrals of motion. We evaluate the uncertainties on our estimates due to random sampling noise, systematic distance errors, the adopted density profile, and non-virialization and non-spherical effects of the halo. The tracer density profile remains a limiting systematic in our mass estimates, although within these limits we find reasonable agreement across the different samples and the methods applied. Out to $\sim70$ and $\sim50$ kpc, the Jeans method yields total enclosed masses of $4.3\pm0.95$ (random) $\pm0.6$ (systematic) $\times10^{11}$ M$_\odot$ and $4.1\pm1.2$ (random) $\pm0.6$ (systematic) $\times10^{11}$ M$_\odot$ for the KG and BHB stars, respectively. For the KG and BHB samples we find a dark matter virial mass of $M_{200}=0.55^{+0.15}_{-0.11}$ (random) $\pm0.083$ (systematic) $\times10^{12}$ M$_\odot$ and $M_{200}=1.00^{+0.67}_{-0.33}$ (random) $\pm0.15$ (systematic) $\times10^{12}$ M$_\odot$, respectively.

Recent observations of protoplanetary disks (PPDs) in the sub-mm have revealed the ubiquity of annular substructures, indicative of pebble-sized dust particles trapped in turbulent ring-like gas pressure bumps. This major paradigm shift also challenges the leading theory of planetesimal formation from such pebbles by the streaming instability, which operates in a pressure gradient and can be suppressed by turbulence. Here we conduct three-dimensional local shearing-box, non-ideal magnetohydrodynamic (MHD) simulations of dust trapping in enforced gas pressure bumps including dust backreaction. Under the moderate level of turbulence generated by the magnetorotational instability (MRI) with ambipolar diffusion that is suitable for outer disk conditions, we achieve quasi-steady states of dust trapping balanced by turbulent diffusion. We find strong dust clumping in all simulations near the gas pressure maxima, reaching a maximum density well above the threshold of triggering gravitational collapse to form planetesimals. A strong pressure bump concentrates dust particles towards bump center. With a weak pressure bump, dust can also concentrate in secondary filaments off the bump center due to dust backreaction, but strong clumping still occurs mainly in the primary ring around the bump center. Our results reveal dust-trapping rings as robust locations for planetesimal formation in outer PPDs, while they may possess diverse observational properties.

EIFIS (Extreme Integral FIeld Spectrograph) is a modular integral field spectrograph, based on image slicers, and makes use of new, large format detectors. The concept is thought to cover the largest possible field of view while producing spectroscopy over the complete optical range (3 000 - 10 000 \r{A}) at a medium resolving power of about 2400. In the optimal concept, each module covers a field of view of 38" x 38" with 0.3" spaxels, which is fed into a double spectrograph with common collimator optics. The blue arm covers the spectral range between 3000 and 5600 \r{A} and the red arm between 5400 and 10100 \r{A}, allowing for an overlap range. The spectra are imaged onto 9.2k x 9.2k detectors using a double pseudoslit. The proposed design for the 10.4m Gran Telescopio Canarias uses a total of 6 such modules to cover a total of 2.43 square arcminutes. Here we will present the conceptual design of the instrument and a feasibility study of the optical and mechanical design of the spectrographs. We discuss the limitations and alternative designs and its potential to produce leading edge science in the era of extremely large telescopes and the James Webb Space Telescope.

The spectroscopic characterization of terrestrial exoplanets will be made possible for the first time with JWST. One challenge to characterizing such planets is that it is not known a priori whether they possess optically thick atmospheres or even any atmospheres altogether. But this challenge also presents an opportunity - the potential to detect the surface of an extrasolar world. This study explores the feasibility of characterizing the atmosphere and surface of a terrestrial exoplanet with JWST, taking LHS 3844b as a test case because it is the highest signal-to-noise rocky thermal emission target among planets that are cool enough to have non-molten surfaces. We model the planetary emission, including the spectral signal of both atmosphere and surface, and we explore all scenarios that are consistent with the existing Spitzer 4.5 $\mu$m measurement of LHS 3844b from Kreidberg et al. (2019). In summary, we find a range of plausible surfaces and atmospheres that are within 3 $\sigma$ of the observation - less reflective metal-rich, iron oxidized and basaltic compositions are allowed, and atmospheres are restricted to a maximum thickness of 1 bar, if near-infrared absorbers at $\gtrsim$ 100 ppm are included. We further make predictions on the observability of surfaces and atmospheres, perform a Bayesian retrieval analysis on simulated JWST data and find that a small number, ~3, of eclipse observations should suffice to differentiate between surface and atmospheric features. However, the surface signal may make it harder to place precise constraints on the abundance of atmospheric species and may even falsely induce a weak H$_2$O detection.

Although not predicted by standard stellar evolution, it is known that the surface abundance of light elements changes during the red giant branch (RGB) as a result of extra-mixing. This is associated usually with thermohaline mixing acting after the RGB bump. Peculiar lithium-enriched RGB stars might also be related to either enhanced extra-mixing or pollution from external sources. We measure the lithium (Li) abundance and carbon isotopic ratio C12/C13 in a sample of 166 field red giants with -0.3<[Fe/H]<0.2, targeted by the EXPRESS radial velocity program to analyze the effects of extra-mixing. The Li abundance pattern is complicated to interpret, but the comparison between RGB and core-He burning giants shows the effects of extra-mixing consistent with thermohaline. The most Li-enriched giant in the sample was classified as a RGB star close to the luminosity function bump with low C12/C13. Given that the C12/C13 should not be affected by external mechanisms, contamination by an external source, such as a planet, does not seem to be the source of the high Li. The C12C13 presents new clues to describe the extra-mixing. There is a decreasing correlation between mass and C12/C13 in the RGB and an increasing correlation in the horizontal branch, which, once again, is consistent with thermohaline mixing. Our data also shows a correlation between C12/C13 and [Fe/H]. There is no evident impact of binarity either on Li or C12/C13. Our sample shows behavior that is consistent with additional mixing acting after the RGB bump. Li, which is heavily affected by rotational mixing and other processes, does not show a clear trend. Instead, the C12/C13 could be the best tool to study mixing in red giants. Additional measurements of C12/C13 in field stars would greatly improve our ability to compare with models and understand the mixing mechanisms.

We identify targets in the Kepler field that may be characterized by transit timing variations (TTVs) and are detectable by the Transiting Exoplanet Survey Satellite (TESS). Despite the reduced signal-to-noise ratio of TESS transits compared to Kepler, we recover 48 transits from 13 systems in Sectors 14, 15, 26, 40 and 41. We find strong evidence of a nontransiting perturber orbiting Kepler-396 (KOI-2672) and explore two possible cases of a third planet in that system that could explain the measured transit times. We update the ephemerides and mass constraints where possible at KOI-70 (Kepler-20), KOI-82 (Kepler-102), KOI-94 (Kepler-89), KOI-137 (Kepler-18), KOI-244 (Kepler-25), KOI-245 (Kepler-37), KOI-282 (Kepler-130), KOI-377 (Kepler-9), KOI-620 (Kepler-51), KOI-806 (Kepler-30), KOI-1353 (Kepler-289) and KOI-1783 (Kepler-1662).

We present the detailed analysis of 11 local luminous infrared galaxies (LIRGs) from ultraviolet through far-infrared to radio ($\sim$70 MHz to $\sim$15 GHz) bands. We derive the astrophysical properties through spectral energy distribution (SED) modeling using the Code Investigating GALaxy Emission (CIGALE) and UltraNest codes. The radio SEDs include our new observations at 325 and 610 MHz from the GMRT and the measurements from public archives. Our main results are (1) radio SEDs show turnovers and bends, (2) the synchrotron spectral index of the fitted radio spectra ranges between $-$0.5 and $-$1.7, and (3) the infrared luminosity, dust mass, dust temperature, stellar mass, star-formation rates (SFRs) and AGN fraction obtained from CIGALE falls in the range exhibited by galaxies of the same class. The ratio of 60$\mu$m infrared and 1.4 GHz radio luminosity, the 1.4 GHz thermal fraction, and emission measure range between 2.1 and 2.9, 0.1% and 10%, 0.02 and 269.5$\times$10$^{6}$ cm$^{-6}$ pc, respectively. We conclude that the turnovers seen in the radio SEDs are due to free-free absorption; this is supported by the low AGN fraction derived from the CIGALE analysis. The decomposed 1.4 GHz thermal and nonthermal radio luminosities allowed us to compute the star formation rate (SFR) using scaling relations. A positive correlation is observed between the SFR$_{IR}$ obtained 10 Myr ago (compared to 100 Myr ago) and 1.4 GHz radio (total and nonthermal) because similar synchrotron lifetimes are expected for typical magnetic field strengths observed in these galaxies ($\approx$50$\mu$G).

The abundance distribution in the ejecta of the peculiar slowly declining Type Ia supernova (SN\,Ia) SN\,1999aa is obtained by modelling a time series of optical spectra. Similar to SN\,1991T, SN\,1999aa was characterised by early-time spectra dominated by \FeIII\ features and a weak \SiII\,6355\,\AA\ line, but it exhibited a high-velocity \CaII\,H\&K line and morphed into a spectroscopically normal SN\,Ia earlier. Three explosion models are investigated, yielding comparable fits. The innermost layers are dominated by $\sim 0.3$\,\Msun\ of neutron-rich stable Fe-group elements, mostly stable iron. Above that central region lies a \Nifs-dominated shell, extending to $v \approx 11,000$ -- $12,000$\,\kms, with mass $\sim 0.65$\,\Msun. These inner layers are therefore similar to those of normal SNe\,Ia. However, the outer layers exhibit composition peculiarities similar to those of SN\,1991T: the intermediate-mass elements shell is very thin, containing only $\sim 0.2$\,\Msun, and is sharply separated from an outer oxygen-dominated shell, which includes $\sim 0.22$\,\Msun. These results imply that burning suddenly stopped in SN\,1999aa. This is a feature SN\,1999aa shares with SN\,1991T, and explain the peculiarities of both SNe, which are quite similar in nature apart from the different luminosities. The spectroscopic path from normal to SN\,1991T-like SNe\,Ia cannot be explained solely by a temperature sequence. It also involves composition layering differences, suggesting variations in the progenitor density structure or in the explosion parameters.

The Simons Observatory (SO) is a ground-based cosmic microwave background survey experiment that consists of three 0.5 m small-aperture telescopes and one 6 m large-aperture telescope, sited at an elevation of 5200 m in the Atacama Desert in Chile. SO will study the polarization and temperature anisotropies of the Cosmic Microwave Background (CMB). The observatory will require well-understood telescope pointing and scanning. Good antenna control will allow us to execute the scan strategy devised to optimize sensitivity to our scientific goals, calibrate the system with celestial targets, and make maps. To achieve this, we integrate the data acquisition and control of the telescopes' Antenna Control Units (ACUs) within the software framework of the SO Observatory Control System (OCS). We present here the current status of the software integration for the ACUs, as well as measurements of the Small Aperture Telescope platforms' responsiveness to software commanding in the factory, plans for in situ measurements, and prospects for implementation on the Large Aperture Telescope.

Energetic particles emitted by active stars are likely to propagate in astrospheric magnetized plasma turbulent and disrupted by the prior passage of energetic Coronal Mass Ejections (CMEs). We carried out test-particle simulations of $\sim$ GeV protons produced at a variety of distances from the M1Ve star AU~Microscopii by coronal flares or travelling shocks. Particles are propagated within the large-scale quiescent three-dimensional magnetic field and stellar wind reconstructed from measured magnetograms, and { within the same stellar environment following passage of a $10^{36}$~erg kinetic energy CME}. In both cases, magnetic fluctuations with an isotropic power spectrum are overlayed onto the large scale stellar magnetic field and particle propagation out to the two innnermost confirmed planets is examined. In the quiescent case, the magnetic field concentrates the particles onto two regions near the ecliptic plane. After the passage of the CME, the closed field lines remain inflated and the re-shuffled magnetic field remains highly compressed, shrinking the scattering mean free path of the particles. In the direction of propagation of the CME-lobes the subsequent EP flux is suppressed. Even for a CME front propagating out of the ecliptic plane, the EP flux along the planetary orbits highly fluctuates and peaks at $\sim 2 -3$ orders of magnitude higher than the average solar value at Earth, both in the quiescent and the post-CME cases.

Near-Earth asteroid (3200) Phaethon is an active asteroid with a dust tail repeatedly observed over the past decade for 3 days during each perihelion passage down to a heliocentric distance of 0.14 au. The mechanism causing the activity is still debated, and the suggested mechanisms lack clear supporting evidence. Phaethon has been identified as the likely parent body of the annual Geminid meteor shower, making it one of the few active asteroids associated with a meteoroid stream. Its low albedo and B-type reflectance spectrum indicates that Phaethon's composition is similar to carbonaceous chondrite meteorites, but a connection to a specific meteorite group is ambiguous due to the lack of diagnostic absorption features. In this study, we analyze the mid-infrared emissivity spectrum of Phaethon and find that it is closely associated with the Yamato-group (CY) of carbonaceous chondrites. The CY chondrites represent primitive carbonaceous material that experienced early aqueous alteration and subsequent late-stage thermal metamorphism. Minerals in these meteorites, some of which we identify in Phaethon's spectrum, show evidence of thermal decomposition; notably, the dehydroxylation and transformation of phyllosilicates into poorly crystalline olivine. Additionally, sulfides and carbonates in CYs are known release S2and CO2 gas upon heating to ~700oC. We show that Phaethon's surface temperature during its observed window of activity is consistent with the thermal decomposition temperatures of several components in CY meteorites. All of these lines of evidence are strong indicators that gas release from thermal decomposition reactions is responsible for Phaethon's activity. The results of this study have implications for the formation of the Geminid meteoroid stream, the origins of thermally-altered primitive meteorites, and the destruction of low-perihelion asteroids.

Since the late '50s, when the first artificial satellite was launched, the number of resident space objects (RSOs) has steadily increased. It is estimated that around 1 Million objects larger than 1 cm are currently orbiting the Earth, with only 30,000, larger than 10 cm, presently being tracked. To avert a chain reaction of collisions, termed Kessler Syndrome, it is indispensable to accurately track and predict space debris and satellites' orbit alike. Current physics-based methods have errors in the order of kilometres for 7 days predictions, which is insufficient when considering space debris that have mostly less than 1 meter. Typically, this failure is due to uncertainty around the state of the space object at the beginning of the trajectory, forecasting errors in environmental conditions such as atmospheric drag, as well as specific unknown characteristics such as mass or geometry of the RSO. Leveraging data-driven techniques, namely machine learning, the orbit prediction accuracy can be enhanced: by deriving unmeasured objects' characteristics, improving non-conservative forces' effects, and by the superior abstraction capacity that Deep Learning models have of modelling highly complex non-linear systems. In this survey, we provide an overview of the current work being done in this field.

It has been recently shown that the astrophysics of reionization can be extracted from the Ly$\alpha$ forest power spectrum by marginalizing the memory of reionization over cosmological information. This impact of cosmic reionization on the Ly$\alpha$ forest power spectrum can survive cosmological time scales because cosmic reionization, which is inhomogeneous, and subsequent shocks from denser regions can heat the gas in low-density regions to $\sim 3\times10^4$ K and compress it to mean-density. Current approach of marginalization over the memory of reionization, however, is not only model-dependent, based on the assumption of a specific reionization model, but also computationally expensive. Here we propose a simple analytical template for the impact of cosmic reionization, thereby treating it as a broadband systematic to be marginalized over for Bayesian inference of cosmological information from the Ly$\alpha$ forest in a model-independent manner. This template performs remarkably well with an error of $\leq 6 \%$ at large scales $k \approx 0.19$ Mpc$^{-1}$ where the effect of the memory of reionization is important, and reproduces the broadband effect of the memory of reionization in the Ly$\alpha$ forest correlation function, as well as the expected bias of cosmological parameters due to this systematic. The template can successfully recover the morphology of forecast errors in cosmological parameter space as expected when assuming a specific reionization model for marginalization purposes, with a slight overestimation of tens of per cent for the forecast errors on the cosmological parameters. We further propose a similar template for this systematic on the Ly$\alpha$ forest 1D power spectrum.

The chemical composition of the inner region of protoplanetary disks can trace the composition of planetary building material. The exact elemental composition of the inner disk has not yet been measured and tensions between models and observations still exist. Recent advancements have shown UV-shielding to be able to increase emission of organics. Here, we expand on these models and investigate how UV-shielding may impact chemical composition in the inner 5 au. In this work, we use the model from arxiv:2204.07108 and expand it with a larger chemical network. We focus on the chemical abundances in the upper disk atmosphere where the effects of water UV-shielding are most prominent and molecular lines originate. We find rich carbon and nitrogen chemistry with enhanced abundances of C2H2, CH4, HCN, CH3CN, and NH3 by > 3 orders of magnitude. This is caused by the self-shielding of H2O, which locks oxygen in water. This subsequently results in a suppression of oxygen-containing species like CO and CO2. The increase in C2H2 seen in the model with the inclusion of water UV-shielding allows us to explain the observed C2H2 abundance without resorting to elevated C/O ratios as water UV-shielding induced an effectively oxygen-poor environment in oxygen-rich gas. Thus, water UV-shielding is important for reproducing the observed abundances of hydrocarbons and nitriles. From our model result, species like CH4, NH3, and NO are expected to be observable with the James Webb Space Telescope (JWST).

Active star forming regions are excellent laboratories for studying the origins and evolution of young stellar object (YSO) clustering. The W40 - Serpens South region is such a region, and we compile a super near-and-mid-infrared catalog of point sources in it, based on deep NIR observations of CFHT in combination with 2MASS, UKIDSS, and Spitzer catalogs. From this catalog, we identify 832 YSOs, and classify 15, 135, 647, and 35 of them to be the deeply embedded sources, Class I, Class II YSOs, and transition disk sources, respectively. In general, these YSOs are well correlated with the filamentary structures of molecular clouds, especially the deeply embedded sources and the Class I YSOs. The W40 central region is dominated by Class II YSOs, but in the Serpens South region, a half of the YSOs are Class I. We further generate a minimum spanning tree (MST) for all the YSOs. Around the W40 cluster, there are eight prominent MST branches that may trace vestigial molecular gas filaments that once fed gas to the central natal gas clump. Of the eight, only two now include detectable filamentary gas in Herschel data and corresponding Class I YSOs, while the other six are exclusively populated with Class II. Four MST branches overlap with the Serpens South main filament, and where they intersect, molecular gas "hubs" and more Class I YSOs are found. Our results imply a mixture of YSO distributions composed of both primordial and somewhat evolved YSOs in this star forming region.

Young stellar clusters are believed to inherit the spatial distribution like hierarchical structures of their natal molecular cloud during their formation. However, the change of the structures between the cloud and the young clusters is not well constrained observationally. We select the W40 - Serpens South region (~ 7 $\times$ 9 pc$^{2}$) of the Aquila Rift as a testbed and investigate hierarchical properties of spatial distribution of young stellar objects (YSOs) in this region. We develop a minimum spanning tree (MST)-based method to group stars into several levels by successively cutting down edges longer than an algorithmically determined critical value. A total of 832 YSOs are divided into 5 levels with 23 groups. For describing the hierarchical properties in a controlled way, we construct a set of synthetic source distributions at various fractal dimensions, and apply the same method to explore their group characters. By comparing the $Q$ parameter and the surface density profiles of the observed and the synthetic data, we find that the YSO observation matches spatial patterns from multi-fractal dimensions. In the periphery region where the molecular clouds are more diffuse, the YSO structure is close to a fractal dimension of 2.0, while in the core regions the fractal dimensions are close to 1.6 and 1.4 for the W40 and the Serpens South regions, respectively. Therefore, the YSOs may inherit the fractal pattern of the dense part of the molecular clouds, but such pattern dissipates slowly in several Myr.

We explore the capability of deep learning to classify cosmic structures. In cosmological simulations, cosmic volumes are segmented into voids, sheets, filaments and knots, according to the distribution and kinematics of dark matter (DM), and galaxies are also classified according to the segmentation. However, observational studies cannot adopt this classification method using DM. In this study, we demonstrate that deep learning can bridge the gap between simulations and observations. Our models are based on three-dimensional convolutional neural networks and trained with data of the distribution of galaxies in a simulation to deduce the structure classes from the galaxies rather than DM. Our model can predict the class labels as accurate as a previous study using DM distribution for the training and prediction. This means that galaxy distribution can be a substitution for DM for the cosmic-structure classification, and our models using galaxies can be directly applied to wide-field survey observations. When observational restrictions are ignored, our model can classify simulated galaxies into the four classes with an accuracy (macro-averaged $F_{\rm 1}$-score) of 64 per cent. If restrictions such as limiting magnitude are considered, our model can classify SDSS galaxies at $\sim100~{\rm Mpc}$ with an accuracy of 60 per cent. In the binary classification distinguishing void galaxies from the others, our model can achieve an accuracy of 88 per cent.

We have re-investigated Cosmology involving interaction between Dark matter and Dark Energy in the light of a new parametrization. The new parametrization is based on the hypothesis that when Dark matter and Dark Energy will interact, Dark matter will dilute in a different manner than standard non-interacting scenario. We re-built the Cosmological equations with this new parametrization. Observational constraints on the traditional Cosmological parameters and new parameters has also been obtained by using supernova data from Pantheon and Hubble data. The parameter values obtained are $H_0$ = 69.023 $\pm$ 0.722, $M$ = -19.385 $\pm$ 0.019, $I$ = 2.901 $\pm$ 0.092 and $\Omega_{dm0}(1 - \frac{3}{I})\frac{1}{\kappa}$ = 0.254 $\pm$ 0.023 where $H_0$, $M$, $\Omega_{dm0}$ and $\kappa$ are Hubble constant, absolute magnitude of type 1a supernova, present day dark matter density and coupling parameter between dark matter and dark energy respectively while $I$ is a new parameter, dubbed dilution parameter which we introduced in the model representing the modified dilution of dark matter in the interacting scenario. The physical features of the model in regard to evolution of the Universe, deceleration parameter, age of Universe, particle physics implications of interacting scenario has also been explored in depth and conclusions has been drawn.

Detecting the 21-cm hyperfine transition from neutral hydrogen in the intergalactic medium is our best probe for understanding the astrophysical processes driving the Epoch of Reionisation (EoR). The primary means for a detection of this 21-cm signal is through a statistical measurement of the spatial fluctuations using the 21-cm power spectrum (PS). However, the 21-cm signal is non-Gaussian meaning the PS, which only measures the Gaussian fluctuations, is sub-optimal for characterising all of the available information. The upcoming Square Kilometre Array (SKA) will perform a deep, 1000 hr observation over 100 deg$.^{2}$ specifically designed to recover direct images of the 21-cm signal. In this work, we use the Wavelet Scattering Transform (WST) to extract the non-Gaussian information directly from these two-dimensional images of the 21-cm signal. The key advantage of the WST is its stability with respect to statistical noise for measuring non-Gaussian information, unlike the bispectrum whose statistical noise diverges. We introduce a novel method to isolate this non-Gaussian information from mock 21-cm images and demonstrate its detection at 150 (177)~MHz ($z\sim8.5$ and $\sim7$) for a fiducial model with signal-to-noise of $\sim$5~(8) assuming perfect foreground removal and $\sim2$~(3) assuming foreground wedge avoidance.

NGC~5548 is an X-ray bright Seyfert 1 active galaxy. It exhibits a variety of spectroscopic features in the soft X-ray band, including in particular the absorption by the AGN outflows of a broad range of ionization states, with column densities up to 1E27 /m^2, and having speeds up to several thousand kilometers per second. The known emission features are in broad agreement with photoionized X-ray narrow and broad emission line models. We report on an X-ray spectroscopic study using 1.1 Ms XMM-Newton and 0.9 Ms Chandra grating observations of NGC 5548 spanning two decades. The aim is to search and characterize any potential spectroscopic features in addition to the known primary spectral components that are already modeled in high precision. We detect a weak unidentified excess emission feature at 18.4 Angstrom (18.1 Angstrom in the restframe). The feature is seen at >5 sigma statistical significance taking into account the look elsewhere effect. No known instrumental issues, atomic transitions, and astrophysical effects can explain this excess. The observed intensity of the possible feature seems to anti-correlate in time with the hardness ratio of the source. However, the variability might not be intrinsic, it might be caused by the time-variable obscuration by the outflows. An intriguing possibility is the line emission from charge exchange between a partially ionized outflow and a neutral layer in the same outflow, or in the close environment. Other possibilities, such as emission from a highly-ionized component with high outflowing speed, cannot be fully ruled out.

The radiations from the first luminous sources drive the fluctuations in the 21-cm signal at Cosmic Dawn (CD) via two dominant astrophysical processes i.e. the Ly$\alpha$ coupling and X-ray heating, making this signal highly non-Gaussian. The impact of these processes on the 21-cm signal and its non-Gaussianity vary depending on the properties of these first sources of light. In this work, we consider different CD scenarios by varying two major source parameters i.e. the minimum halo mass $M_{\rm h,\, min}$ and X-ray photon production efficiency $f_{\rm X}$ in a 1D radiative transfer code GRIZZLY. We study the impact of variation in these source parameters on the large scale ($k_1 = 0.16 {\, \rm Mpc}^{-1}$) 21-cm bispectrum for all possible unique triangles in the Fourier domain. Our detailed and comparative analysis of the power spectrum and bispectrum shows that the shape, sign and magnitude of the bispectrum combinedly provide the best measure of the signal fluctuations and its non-Gaussianity compared to the power spectrum. We also conclude that it is important to study the sequence of sign changes along with the variations in the shape and magnitude of the bispectrum throughout the CD history to arrive at a robust conclusion about the dominant IGM processes at different cosmic times. We further observe that among all the possible unique $k$-triangles, the large-scale non-Gaussianity in signal is best probed by the small $k$-triangles in the squeezed limit and by triangles of similar shapes. This opens up the possibility of constraining the source parameters during the CD using the 21-cm bispectrum.

Time-series photometry in I and J band of 57 inner Galactic late-type stars, highly-probable red supergiant (RSG) stars, is here presented. 38% of the sample presents significant photometric variations. The variations in I and J band appear to be correlated, with DeltaI = DeltaJ x 2.2, DeltaI variations ranging from 0.04-1.08 mag, DeltaJ variations from 0.03-0.52 mag. New short periods (< 1000 d) could be estimated for 8 stars and range from 167-433 d. This work confirms that the sample is not contaminated by large-amplitude Asymptotic Giant Branch (AGB) stars. Furthermore, despite the large errors in distance, the period-luminosity diagram suggests that the sample is populating the same sequence as the known Galactic RSGs.

The study of pulsating stars in eclipsing binaries holds the promise of combining two different ways of measuring the physical properties of a star to obtain improved constraints on stellar theory. Gravity (g) mode pulsations such as those found in $\gamma$ Doradus stars can be used to probe rotational profiles, mixing and magnetic fields. Until recently few $\gamma$ Doradus stars in eclipsing binaries were known. We have discovered g-mode pulsations in four detached eclipsing binary systems from light curves obtained by the Transiting Exoplanet Survey Satellite (TESS) and present an analysis of their eclipses and pulsational characteristics. We find unresolved g-mode pulsations at frequencies 1--1.5 d$^{-1}$ in CM Lac, and measure the masses and radii of the component stars from the TESS data and published radial velocities. MZ Lac shows a much richer frequency spectrum, including pressure modes and tidally-excited g-modes. RX Dra is in the northern continuous viewing zone of TESS so has a light curve covering a full year, but shows relatively few pulsation frequencies. For V2077 Cyg we formally measure four pulsation frequencies, but the available data are inadequate to properly resolve the g-mode pulsations. V2077 Cyg also shows total eclipses, with which we obtain the first measurement of the surface gravity of the faint secondary star. All four systems are bright and good candidates for detailed study. Further TESS observations are scheduled for all four systems, with much improved temporal baselines in the cases of RX Dra and V2077 Cyg.

We investigate the observational excess of the EDGES experiment on the global 21-cm brightness temperature ($-500^{+200}_{-500} mK$ at redshift $14<z<20$) in the context of viscous dark energy (VDE) models. The bulk viscosity of dark energy perturbs the Hubble evolution of the Universe which could cool baryons faster, and hence, alter the 21-cm brightness temperature. An additional amount of entropy is also produced as an outcome of the viscous flow. We study the contribution of Hawking radiation from primordial black holes and baryon-dark matter scattering in the backdrop of VDE models towards modification of the 21-cm temperature. We obtain bounds on the VDE model parameters in order to account for the EDGES result due to the interplay of the above effects. Moreover, our analysis yields modified constraints on the dark matter mass and scattering cross-section compared to the case of the $\Lambda$CDM model.

The measurement of the isotopic composition of cosmic rays (CRs) provides essential insights the understanding of the origin and propagation of these particles, namely the CR source spectra, the propagation processes and the galactic halo size. The Alpha Magnetic Spectrometer (AMS-02), a CR detector operating aboard the International Space Station since May 2011, has the capability of performing these measurements due to its precise determination of the velocity provided by its Time of Flight (TOF) and Ring Imaging Cherenkov (RICH) detector. The correct interpretation of the data requires the measurements to be deconvoluted from the instrumental effects. The unique design of AMS-02, with more than one subdetector being used to measure the same flux, requires a novel approach to unfold the measured fluxes. In this work, we describe an iterative-Bayesian unfolding method applied in the context of isotopic flux measurements in AMS-02. The accuracy of the method is assessed using a simulated flux based on previous measurements and a full detector response function. We introduce a non-parametric regularization method for the detector response functions, as well as a single, smooth prior flux covering the full range of measurements from both detectors, TOF and RICH. In addition, the estimation of the errors and a discussion about the performance of the method are also shown, demonstrating that the method is fast and reliable, allowing for the recovery of the true fluxes in the full energy range.

The microscopic quantum nature of elementary particles, chirality, leads to macroscopic phenomena like the chiral anomaly, chiral magnetic effect, and chiral plasma instability. We review recent progress of the studies of these chiral effects in high-energy astrophysics, such as pulsar kicks, magnetars, and core-collapse supernovae, and early Universe cosmology, such as the primordial magnetic field, baryogenesis, and chiral gravitational waves. We also provide a pedagogical introduction to the chiral effects and low-energy effective theories to describe them in and out of equilibrium -- the chiral (magneto)hydrodynamics, chiral kinetic theory, and chiral radiation transport theory for neutrinos.

The origin of the Fermi bubbles, which constitute two gamma-rays emitting lobes above and below the Galactic plane, remains unclear. The possibility that the Fermi bubble gamma-rays emission originates from hadronic cosmic-rays advected by a subsonic Galactic outflow is explored. Such a solution is called a Galactic breeze. This model is motivated by UV absorption line observations of cold clouds expanding from the Galactic center to high latitudes. For this purpose the hydrodynamical code PLUTO has been used in combination with a cosmic ray transport code. A model of the Galactic gravitational potential has been determined through constraints derived from the Gaia second data release. It is found that a Galactic breeze can be collimated by the surrounding gas and is indeed able to reproduce the observed Fermi-LAT energy flux at high Galactic latitudes. Following these results a prediction concerning the gamma-rays emission for 1-3~TeV photons is made for future comparison with CTA/SWGO measurements.

A search for pulse signals was carried out in a new sky area included in the monitoring program for the search for pulsars and transients. Processing of several months data recorded in six frequency channels with a total bandwidth of 2.5 MHz showed that, on average, 4 pulses per hour are observed in each of the 24 connected stationary beams. Of these pulses, 18.3% are similar to those of pulsars. They are visible in one or two neighboring beams and have a pronounced dispersion shift, that is, they are recorded first at a high and then at a low frequency, which indicates the possible passage of the signal through the interstellar medium. Almost 68% of such detected pulses belong to six known pulsars with dispersion measures from 9 to 141 $pc/cm^3$, and almost all of the remaining pulses are either noise of an unknown nature or artifacts of the proposed pulse separation technique. An additional study of the selected array of 3650 obvious pulsar pulses revealed 13 pulses belonging to four rotating radio transients (RRATs). Their dispersion measures are in the range of 17-51 $pc/cm^3$. A search for regular (periodic) RRAT emission was carried out using power spectra summed over 121 days. Periodic radiation was not detected, but for two RRATs, upper estimates of the periods were obtained from measurements of the time intervals between pulses. The upper estimates of the integrated flux density of the detected RRATs are in the range 2-4 mJy at the frequency 111 MHz.

Massive O and early B stars are important markers of recent star formation and exert a significant influence on their environments during their short lives via photoionization and winds and when they explode as supernovae. In the Milky Way they can be detected at great distances but often lie behind large dust columns, making detection at short wavelengths difficult. In this study the use of the less extinguished far-red spectrum (8400 -- 8800 \AA ) for radial velocity measurement is examined. Results are reported for a sample of 164 confirmed OB stars within a 2-degree field positioned on the Carina Arm. Most stars are at distances between 3 and 6 kpc, and Westerlund 2 is at the field edge. The measured radial velocities have errors concentrated in the 3--10 km s$^{-1}$ range, with a systematic uncertainty of 2--3 km s$^{-1}$. These are combined with Gaia-mission astrometry to allow full space motions to be constructed. Up to 22 stars are likely to be runaways although 8 of them are as likely to be interloping (so far undetected) binaries. The mean azimuthal motion of the sample fits in with recent measurements of Galactic disk rotation. In the Galactocentric radial direction the mean motion indicates modest infall at a speed of $\sim$ 10 km s$^{-1}$. This experiment shows that weak Paschen lines in the far-red can yield credible radial velocity determination, offering the prospect of exploring OB-star kinematics over much more of the Galactic disk than has hitherto been possible.

We have carried out a search for flares from the analysis of light curves for 12 active G, K, and M dwarfs. As sources of data we used ground-based observations in 2000-2020 from the photometric databases ASAS, SuperWASP, KWS. Events of low-amplitude brightening (Delta V < 0.25 mag), which possibly could be flares, were revealed for 11 stars. A large number of such increases in brightness were found on K dwarfs. Events of increasing in V-magnitudes to 0.5 mag or more were detected on light curves of one G star, BE Cet, and two M dwarfs. For three flares we could follow their development with time. We have estimated the duration of these flares; they lasted more than an hour, but less than 3 hours. In most cases we could not determine a lifetime of the suggested flares, but we believe that most of the probable flares on the investigated cool dwarfs are short-lived, on the order of several minutes.

The extended ROentgen Survey with an Imaging Telescope Array (eROSITA) onboard the Spectrum-Roentgen-Gamma (SRG) observatory is revolutionizing X-ray astronomy. It provides large samples of active galactic nuclei (AGN) and clusters of galaxies, with the potential of studying X-ray sources and measuring cosmological parameters using X-ray-selected samples with higher precision than ever before. We aim to study the detection, and the selection of AGN and clusters in the first eROSITA all-sky survey (eRASS1), and to characterize the properties of the source catalog. We produced a half-sky eRASS1 simulation, by combining models that truthfully represent the clusters and AGN. In total, we simulated 1 116 758 clusters and 225 583 320 AGN. We ran the standard eROSITA detection algorithm. We matched the input and source catalogs with a photon-based algorithm. We perfectly recovered the bright sources. We detected half of the AGN brighter than 2e-14 erg/s/cm2 as point sources and half of the clusters brighter than 3e-13 erg/s/cm2 as extended in the 0.5-2.0 keV band. We quantified the detection performance in terms of completeness, false detection rate, and contamination. We studied the source catalog according to multiple cuts of detection and extension likelihood. We find that the detection of clusters is mainly driven by flux and exposure. It depends on secondary effects, such as the size of the clusters and their dynamical state. The cool core bias mostly affects faint clusters classified as point sources, while its impact on the extent-selected sample is small. The measured X-ray luminosity of the detected clusters is compatible with the simulated values. We discuss how to best build samples of galaxy clusters for cosmological purposes, accounting for the nonuniform depth of eROSITA. This simulation provides a digital twin of the real eRASS1.

We report recent ESPaDOnS and HARPSpol spectropolarimetric observations from our ongoing magnetic survey of the brightest twenty-five classical Cepheids. Stokes $V$ magnetic signatures are detected in eight of fifteen targets observed to date. The Stokes $V$ profiles show a diversity of morphologies with weak associated longitudinal field measurements of order 1 G. Many of the Stokes $V$ profiles are difficult to interpret in the context of the normal Zeeman effect. They consist of approximately unipolar single or double lobe(s) of positive or negative circular polarization. We hypothesize that these unusual signatures are due to the Zeeman effect modified by atmospheric velocity or magnetic field gradients. In contrast, the Stokes $V$ profiles of Polaris and MY Pup appear qualitatively similar to the complex magnetic signatures of non-pulsating cool supergiants, possibly due to the low pulsation amplitudes of these two stars.

The Earth's revolution is modified by changes in inclination of its rotation axis. Despite the fact that the gravity field is central, the Earth's trajectory is not closed and the equinoxes drift. Milankovic (1920) argued that the shortest precession period of solstices is 20,7kyr: the Summer solstice in one hemisphere takes place alternately every 11kyr at perihelion and at aphelion. We have submitted the time series for the Earth's pole of rotation, global mean surface temperature and ephemeris to iterative Singular Spectrum Analysis. iSSA extracts from each a trend, a 1yr and a 60yr component. Both the apparent drift of solstices of Earth around the Sun and the global mean temperature exhibit a strong 60yr oscillation. The "fixed dates" of solstices actually drift. Comparing the time evolution of the Winter and Summer solstices positions of the rotation pole and the first iSSA component (trend) of the temperature allows one to recognize some common features. A basic equation from Milankovic links the derivative of heat received at a given location on Earth to solar insolation, known functions of the location coordinates, solar declination and hour angle, with an inverse square dependence on the Sun-Earth distance. We have translated the drift of solstices as a function of distance to the Sun into the geometrical insolation theory of Milankovic. Shifting the inverse square of the 60yr iSSA drift of solstices by 15 years with respect to the first derivative of the 60yr iSSA trend of temperature, that is exactly a quadrature in time, puts the two curves in quasi-exact superimposition. The probability of a chance coincidence appears very low. Correlation does not imply causality when there is no accompanying model. Here Milankovic's equation can be considered as a model that is widely accepted. This paper identifies a case of agreement between observations and a mathematical formulation.

Over the past decades, global geodynamical models have been used to investigate the thermal evolution of terrestrial planets. With the increase of computational power and improvement of numerical techniques, these models have become more complex, and simulations are now able to use a high resolution 3D spherical shell geometry and to account for strongly varying viscosity, as appropriate for mantle materials. In this study we review global 3D geodynamic models that have been used to study the thermal evolution and interior dynamics of Mars. We discuss how these models can be combined with local and global observations to constrain the planet's thermal history. In particular, we use the recent InSight estimates of the crustal thickness, upper mantle structure, and core size to show how these constraints can be combined with 3D geodynamic models to improve our understanding of the interior dynamics, present-day thermal state and temperature variations in the interior of Mars.

Around one third of the point-like sources in the Fermi-LAT catalogs remain as unidentified sources (unIDs) today. Indeed, these unIDs lack a clear, univocal association with a known astrophysical source. If dark matter (DM) is composed of weakly interacting massive particles (WIMPs), there is the exciting possibility that some of these unIDs may actually be DM sources, emitting gamma rays from WIMPs annihilation. We propose a new approach to solve the standard, Machine Learning (ML) binary classification problem of disentangling prospective DM sources (simulated data) from astrophysical sources (observed data) among the unIDs of the 4FGL Fermi-LAT catalogue. Concretely, we artificially build two systematic features for the DM data which are originally inherent to observed data: the detection significance and the uncertainty on the spectral curvature. We do it by sampling from the observed population of unIDs, assuming that the DM distributions would, if any, follow the latter. We consider different ML models: Logistic Regression, Neural Network (NN), Naive Bayes and Gaussian Process, out of which the best, in terms of classification accuracy, is the NN, achieving around 93% performance. Applying the NN to the unIDs sample, we find that the degeneracy between some astrophysical and DM sources can be partially solved within this methodology. Nonetheless, we conclude that there are no DM source candidates among the pool of 4FGL Fermi-LAT unIDs.

Cosmological parameters encoding our current understanding of the expansion history of the Universe can be constrained by the accurate estimation of time delays arising in gravitationally lensed systems. We propose TD-CARMA, a Bayesian method to estimate cosmological time delays by modelling the observed and irregularly sampled light curves as realizations of a Continuous Auto-Regressive Moving Average (CARMA) process. Our model accounts for heteroskedastic measurement errors and microlensing, an additional source of independent extrinsic long-term variability in the source brightness. The CARMA formulation admits a linear state-space representation, that allows for efficient and scalable likelihood computation using the Kalman Filter. We obtain a sample from the joint posterior distribution of the model parameters using a nested sampling approach. This allows for "painless" Bayesian Computation, dealing with the expected multi-modality of the posterior distribution in a straightforward manner and not requiring the specification of starting values or an initial guess for the time delay, unlike existing methods. In addition, the proposed sampling procedure automatically evaluates the Bayesian evidence, allowing us to perform principled Bayesian model selection. TD-CARMA is parsimonious, and typically includes no more than a dozen unknown parameters. We apply TD-CARMA to three doubly lensed quasars HS 2209+1914, SDSS J1001+5027 and SDSS J1206+4332, estimating their time delays as $-21.96 \pm 1.448$ (6.6$\%$ precision), $120.93 \pm 1.015$ (0.8$\%$), and $111.51 \pm 1.452$ (1.3$\%$), respectively. A python package, TD-CARMA, is publicly available to implement the proposed method.

While there is now a consensus that X-ray binaries (XRBs) are the dominant X-ray sources in the early Universe and play a significant role during the epoch of heating of the intergalactic medium (IGM), recent studies report contradicting results regarding their contribution in the nebular emission of local Universe galaxies. Ultraluminous X-ray sources (ULXs), which dominate the X-ray budget of normal galaxies, may be important interstellar-medium (ISM) ionizing sources. However, their output in the extreme UV (EUV) and soft--X-ray part of the spectrum remains observationally unconstrained. In this paper, we predict the ionizing and heating power from ULX populations under the geometrical beaming scenario, and three models describing the emission from super-critical accretion disks. We find that our theoretical spectra for ULX populations cannot (can) explain the HeII (NeV) emission observed in some galaxies, with their contribution being less (more) important than the underlying stellar population. Stochastic fluctuations in the number of ULXs may allow for equal contributions in the HeII emission, in a fraction of galaxies. We provide average spectra of ULX populations as an input to local, and early-Universe studies. We find that the soft--X-ray emission arising from super-critical accretion is significant for the heating of the IGM, and consistent with recent constraints from the 21-cm cosmic signal. Based on the dependence on the adopted compact-object (CO) mass and accretion model, we encourage efforts in modeling ULX spectra via simulations, and their combination with detailed binary population synthesis models.

Massive stars are among the main cosmic engines driving the evolution of star-forming galaxies. Their powerful ionising radiation and stellar winds inject a large amount of energy in the interstellar medium. Furthermore, mass-loss ($\dot{M}$) through radiatively driven winds plays a key role in the evolution of massive stars. Even so, the wind mass-loss prescriptions used in stellar evolution models, population synthesis, and stellar feedback models often disagree with mass-loss rates empirically measured from the UV spectra of low metallicity massive stars. The most massive young star cluster in the low metallicity Small Magellanic Cloud galaxy is NGC346. This cluster contains more than half of all O stars discovered in this galaxy so far. A similar age, metallicity ($Z$), and extinction, the O stars in the NGC346 cluster are uniquely suited for a comparative study of stellar winds in O stars of different subtypes. We aim to use a sample of O stars within NGC346 to study stellar winds at low metallicity. We mapped the central 1" of NGC346 with the long-slit UV observations performed by the Space Telescope Imaging Spectrograph (STIS) on board of the {\em Hubble Space Telescope} and complemented these new datasets with archival observations. Multi-epoch observations allowed for the detection of wind variability. The UV dataset was supplemented by optical spectroscopy and photometry. The resulting spectra were analysed using a non-local thermal equilibrium model atmosphere code (PoWR) to determine wind parameters and ionising fluxes. The effective mapping technique allowed us to obtain a mosaic of almost the full extent of the cluster and resolve stars in its core. Among hundreds of extracted stellar spectra, 21 belong to O stars. Nine of them are classified as O stars for the first time. We analyse, in detail, the UV spectra of 19 O stars... (continued)

We report on the first observation of a radio-quiet Active Galactic Nucleus (AGN) using polarized X-rays: the Seyfert 1.9 galaxy MCG-05-23-16. This source was pointed with the Imaging X-ray Polarimetry Explorer (IXPE) starting on May 14, 2022 for a net observing time of 486 ks, simultaneously with XMM-Newton (58 ks) and NuSTAR (83 ks). A polarization degree smaller than $\Pi<4.7\%$ (at the 99% c.l.) is derived in the 2-8 keV energy range, where emission is dominated by the primary component ascribed to the hot corona. The broad-band spectrum, inferred from a simultaneous fit to the IXPE, NuSTAR, and XMM-Newton data, is well reproduced by a power law with photon index $\Gamma=1.85\pm0.01$ and a high-energy cutoff $E_{\rm C}=120\pm15$ keV. A comparison with Monte Carlo simulations shows that a lamp-post and a conical geometry of the corona are consistent with the observed upper limit, a slab geometry is allowed only if the inclination angle of the system is less than 50$^{\circ}$.

We present measurements of the rest-frame ultraviolet luminosity function (UV LF) at redshifts $z=3$, $z=4$ and $z=5$, using 96894, 38655 and 7571 sources respectively to map the transition between AGN and galaxy-dominated ultraviolet emission shortly after the epoch of reionization. Sources are selected using a comprehensive photometric redshift approach, using $10$\ds\, of deep extragalactic legacy fields covered by both HSC and VISTA. The use of template fitting spanning a wavelength range of $0.3\text{--}2.4\mu m$ achieves $80\text{--}90$ per cent completeness, much higher than classical colour-colour cut methodology. The measured LF encompasses $-26<M_{\rm UV}<-19.25(-20.5)$ at $z=3(5)$. This is further extended to $-28.5<M_{\rm UV}<-16$ using complementary results from other studies, allowing for the simultaneous fitting of the combined AGN and galaxy LF. We find that there are fewer UV luminous galaxies ($M_{\rm UV}<-22$) at $z\sim3$ than $z\sim4$, indicative of an onset of widespread quenching alongside dust obscuration, and that the evolution of the AGN LF is much more rapid than the galaxy LF, with their number density rising by around 2 orders of magnitude from $3<z<6$. We also find that it remains difficult to determine if a double power law (DPL) functional form is preferred over the Schechter function to describe the galaxy UV LF with photometric data alone. Estimating the Hydrogen ionizing photon budget from our UV LFs, we find that AGN can contribute to, but cannot solely maintain, the reionization of the Universe at $z=3-5$. However, the rapidly evolving AGN LF strongly disfavours a significant contribution within the EoR.

Habitability of exoplanet's deepest oceans could be limited by the presence of high-pressure ices at their base. New work demonstrates that efficient chemical transport within deep planetary ice mantles is possible through significant salt incorporation within the high-pressure ice.

We report the detection of fulvenallene ($c$-C$_5$H$_4$CCH$_2$) in the direction of TMC-1 with the QUIJOTE line survey. Thirty rotational transitions with $K_a$=0,1,2,3 and $J$=9-15 were detected. The best rotational temperature fitting of the data is 9\,K and a derived column density is (2.7$\pm$0.3)$\times$10$^{12}$ cm$^{-2}$, which is only a factor of 4.4 below that of its potential precursor cyclopentadiene ($c$-C$_5$H$_6$), and 1.4--1.9 times higher than that of the ethynyl derivatives of cyclopentadiene. We searched for fulvene ($c$-C$_5$H$_4$CH$_2$), a CH$_2$ derivative of cyclopentadiene, for which we derive a 3$\sigma$ upper limit to its column density of (3.5$\pm$0.5)$\times$10$^{12}$ cm$^{-2}$. Upper limits were also obtained for toluene (C$_6$H$_5$CH$_3$) and styrene (C$_6$H$_5$C$_2$H$_3$), the methyl and vinyl derivatives of benzene. Fulvenallene and ethynyl cyclopentadiene are likely formed in the reaction between cyclopentadiene ($c$-C$_5$H$_6$) and the ehtynyl radical (CCH). However, the bottom-up gas-phase synthesis of cycles in TMC-1 underestimates the abundance of cyclopentadiene by two orders of magnitude, which strengthens the need to study all possible chemical pathways to cyclisation in cold dark cloud environments, such as TMC-1. However, the inclusion of the reaction between C$_3$H$_3^+$ and C$_2$H$_4$ produces a good agreement between model and observed abundances.

The CRESST experiment observes an unexplained excess of events at low energies. In the current CRESST-III data-taking campaign we are operating detector modules with different designs to narrow down the possible explanations. In this work, we show first observations of the ongoing measurement, focusing on the comparison of time, energy and temperature dependence of the excess in several detectors. These exclude dark matter, radioactive backgrounds and intrinsic sources related to the crystal bulk as a major contribution.

We calculate ab initio the gravitational potential energy per unit area for a gravitationally coupled multi-component galactic disk of stars and gas, which is given as the integration over vertical density distribution, vertical gravitational force, and vertical distance. This is based on the method proposed by Camm for a single-component disk, which we extend here for a multi-component disk by deriving the expression of the energy explicitly at any galactocentric radius R. For a self-consistent distribution, the density and force are obtained by jointly solving the equation of vertical hydrostatic equilibrium and the Poisson equation. Substituting the numerical values for the density distribution and force obtained for the coupled system, in the derived expression of the energy, we find that the energy of each component remains unchanged compared to the energy for the corresponding single-component case. We explain this surprising result by simplifying the above expression for the energy of a component analytically, which turns out to be equal to the surface density times the squared vertical velocity dispersion of the component. However, the energy required to raise a unit test mass to a certain height z from the mid-plane is higher in the coupled case. The system is therefore more tightly bound closer to the mid-plane, and hence it is harder to disturb it due to an external tidal encounter.

Interstellar dust grain growth in dense clouds and protoplanetary disks, even moderate, affects the observed interstellar ice profiles as soon as a significant fraction of dust grains is in the size range close to the wave vector at the considered wavelength. The continuum baseline correction made prior to analysing ice profiles influences the subsequent analysis and hence the estimated ice composition, typically obtained by band fitting using thin film ice mixture spectra. We model the effect of grain growth on ice mantle spectroscopic profiles, focusing on CO2 to see how it can affect interstellar ice mantle spectral analysis and interpretation. Using the Discrete Dipole Approximation for Scattering and Absorption of Light, the mass absorption coefficients of distributions of grains composed of ellipsoidal silicate cores with water and carbon dioxide ice mantles are calculated. A few other ice mantle compositions are also calculated. We explore the size distribution evolution from dense clouds to simulate the first steps of grain growth up to three microns in size. The results are injected into RADMC-3D full scattering radiative transfer models of spherical clouds and protoplanetary disk templates to retrieve observable spectral energy distributions. We focus on calculated profile of the CO2 antisymmetric stretching mode ice band profile at 4.27 microns, a meaningful indicator of grain growth. The observed profiles toward dense cores with the Infrared space observatory and Akari satellites already showed profiles possibly indicative of moderate grain growth.The observation of protoplanetary disks at high inclination with the JWST should present distorted profiles that will put constraints on the extent of dust growth. The more evolved the dust size distribution, the more the extraction of the ice mantle composition will require both understanding and taking into account grain growth.

The magnetic fields in galaxy clusters and probably also in the interstellar medium are believed to be generated by a small-scale dynamo. Theoretically, during its kinematic stage, it is characterized by a Kazantsev spectrum, which peaks at the resistive scale. It is only slightly shallower than the Saffman spectrum that is expected for random and causally connected magnetic fields. Causally disconnected fields have the even steeper Batchelor spectrum. Here we show that all three spectra are present in the small-scale dynamo. During the kinematic stage, the Batchelor spectrum occurs on scales larger than the energy-carrying scale of the turbulence, and the Kazantsev spectrum on smaller scales within the inertial range of the turbulence -- even for a magnetic Prandtl number of unity. In the saturated state, the dynamo develops a Saffman spectrum on large scales. At large magnetic Prandtl numbers, elongated structures are seen in the parity-even E polarization, but not in the parity-odd B polarization. We also observe a significant excess in the E polarization over the B polarization at subresistive scales, and a deficiency at larger scales. This finding is at odds with the observed excess in the Galactic microwave foreground emission. The E and B polarizations become Gaussian in the saturated state, but may be highly non-Gaussian and skewed in the kinematic regime of the dynamo.

Precise fundamental atmospheric stellar parameters and abundance determination of individual elements in stars are important for all stellar population studies. Non-Local Thermodynamic Equilibrium (Non-LTE; hereafter NLTE) models are often important for such high precision, however, can be computationally complex and expensive, which renders the models less utilized in spectroscopic analyses. To alleviate the computational burden of such models, we developed a robust 1D, LTE and NLTE fundamental atmospheric stellar parameter derivation tool, $\texttt{LOTUS}$, to determine the effective temperature $T_{\mathrm{eff}}$, surface gravity $\log g$, metallicity $\mbox{[Fe/H]}$ and microturbulent velocity $v_{\mathrm{mic}}$ for FGK type stars, from equivalent width (EW) measurements of Fe I and Fe II lines. We utilize a generalized curve of growth method to take into account the EW dependencies of each Fe I and Fe II line on the corresponding atmospheric stellar parameters. A global differential evolution optimization algorithm is then used to derive the optimized fundamental parameters. Additionally, $\texttt{LOTUS}$ can determine precise uncertainties for each stellar parameter using a Markov Chain Monte Carlo (MCMC) algorithm. We test and apply $\texttt{LOTUS}$ on a sample of benchmark stars, as well as stars with available asteroseismic surface gravities from the K2 survey, and metal-poor stars from $R$-process Alliance (RPA) survey. We find very good agreement between our NLTE-derived parameters in $\texttt{LOTUS}$ to non-spectroscopic values within $T_{\mathrm{eff}}=\pm 30$ K and $\log g=\pm 0.20$ dex for benchmark stars. We provide open access of our code, as well as of the interpolated pre-computed NLTE EW grids available on Github, and documentation with working examples on Readthedocs.

We present a new strong lensing (SL) model of the Hubble Frontier Fields galaxy cluster Abell 2744, at z=0.3072, by exploiting archival Hubble Space Telescope (HST) multi-band imaging and Multi Unit Spectroscopic Explorer (MUSE) follow-up spectroscopy. The lens model considers 90 spectroscopically confirmed multiple images (from 30 background sources), which represents the largest secure sample for this cluster field prior to the recently acquired James Webb Space Telescope observations. The inclusion of the sub-structures within several extended sources as model constraints allows us to accurately characterize the inner total mass distribution of the cluster and the position of the cluster critical lines. We include the lensing contribution of 225 cluster members, 202 of which are spectroscopically confirmed. We also measure the internal velocity dispersion of 85 cluster galaxies to independently estimate the role of the subhalo mass component in the lens model. We investigate the effect of the cluster environment on the total mass reconstruction of the cluster core with two different mass parameterizations. We consider the mass contribution from three external clumps, either based on previous weak-lensing studies, or extended HST imaging of luminous members around the cluster core. In the latter case, the observed positions of the multiple images are better reproduced, with a remarkable accuracy of 0.37", a factor of $\sim2$ smaller than previous lens models. We develop and make publicly available a Strong Lensing Online Tool (SLOT) to exploit the predictive power and the full statistical information of this and future models, through a simple graphical interface. We plan to apply our high-precision SL model to the first analysis of the GLASS-JWST-ERS program, specifically to measure the intrinsic physical properties of high-$z$ galaxies from robust magnification maps.

The interstellar medium contains dust and gas, in which at high densities and cold conditions molecules can proliferate. Interstellar Complex Organic Molecules (iCOMs) are C-bearing species that contain at least six atoms. As they are detected in young stellar objects, iCOMs are expected to inhabit the early stages of the star formation evolution. In this study, we try to determine which iCOMs are present in the outflow component of massive protostars. To do this, we analyzed the morphological extension of blue- and red-shifted iCOMs emission in a sample of eleven massive protostars employing mapping observations at one mm within a ~1 GHz bandwidth for both IRAM-30m and APEX telescopes. We modeled the iCOMs emission of the central pointing spectra of our objects using the XCLASS LTE radiative transfer code. We detected the presence of several iCOMs such as: CH3OH, 13CH3OH, CH3OCHO, C2H5C15N, and c-C3H2)CH2. In G034.41+0.24, G327.29-0.58, G328.81+0.63, G333.13-0.43, G340.97-1.02, G351.45+0.66 and G351.77-0.54, the iCOMs lines show a faint broad line profile. Due to the offset peak positions of the blue- and red-shifted emission, covering from ~0.1 to 0.5 pc, these wings are possibly related to movements external to the compact core, such as large-scale low-velocity outflows. We have also established a correlation between the parent iCOM molecule CH3OH and the shock tracer SiO, reinforcing the hypothesis that shock environments provide the conditions to boost the formation of iCOMs via gas-phase reactions.

We present early results regarding the morphological and structural properties of galaxies seen with the James Webb Space Telescope at $z > 3$ in the Early Release Observations of SMACS 0723, a galaxy cluster at $z=0.39$. We investigate, for the first time, the optical morphologies of a significant number of $z > 3$ galaxies with accurate photometric redshifts in this field to determine the form of galaxy structure in the relatively early universe. We use visual morphologies and \textsc{Morfometryka} measures to perform quantitative morphology measurements, both parametric with light profile fitting (S\'ersic indices) and non-parametric (CAS values). Using these, we measure the relative fraction of disk, spheroidal, and peculiar galaxies at $3 < z < 8$. We discover the surprising result that at $z > 1.5$ disk galaxies dominate the overall fraction of morphologies, with a factor of $\sim 10$ relative higher number of disk galaxies than seen by the Hubble Space Telescope at these redshifts. Our visual morphological estimates of galaxies align closely with their locations in CAS parameter space and their S\'ersic indices.

The first few hundred Myrs at $z>10$ mark the last major uncharted epoch in the history of the Universe, where only a single galaxy (GNz11 at $z\approx11$) is currently spectroscopically confirmed. Here we present a search for luminous $z>10$ galaxies with $JWST$/NIRCam photometry spanning $\approx1-5\mu$m and covering 49 arcmin$^{2}$ from the public $JWST$ Early Release Science programs (CEERS and GLASS). Our most secure candidates are two $M_{\rm{UV}}\approx-21$ systems: GLASS-z13 and GLASS-z11. These galaxies display abrupt $\gtrsim2.5$ mag breaks in their spectral energy distributions, consistent with complete absorption of flux bluewards of Lyman-$\alpha$ that is redshifted to $z\approx13$ and $z\approx11$. Lower redshift interlopers such as dusty quiescent galaxies with strong Balmer breaks would be comfortably detected at $>5\sigma$ in multiple bands where instead we find no flux. From SED modeling we infer that these galaxies have already built up $\sim 10^9$ solar masses in stars over the $\lesssim300-400$ Myrs after the Big Bang. The brightness of these sources enable morphological constraints. Tantalizingly, GLASS-z11 shows a clearly extended exponential light profile, potentially consistent with a disk galaxy of $r_{\rm{50}}\approx0.7$ kpc. These sources, if confirmed, join GNz11 in defying number density forecasts for luminous galaxies based on Schechter UV luminosity functions, which require a survey area $>10\times$ larger than we have studied here to find such luminous sources at such high redshifts. They extend evidence from lower redshifts for little or no evolution in the bright end of the UV luminosity function into the cosmic dawn epoch, with implications for just how early these galaxies began forming. This, in turn, suggests that future deep $JWST$ observations may identify relatively bright galaxies to much earlier epochs than might have been anticipated.

We present the results of a first search for galaxy candidates at z$\sim$9--15 on deep seven-bands NIRCam imaging acquired as part of the GLASS-JWST Early Release Science Program on a flanking field of the Frontier Fields cluster A2744. Candidates are selected via two different renditions of the Lyman-break technique, isolating objects at z$\sim$9-11, and z$\sim$9-15, respectively, supplemented by photometric redshifts obtained with two independent codes. We find six color-selected candidates at z$>$9, plus one additional candidate with photometric redshift z$_{phot}\geq$9. In particular, we identify two bright candidates at $m_{F150W}\simeq 26$ that are unambiguously placed at $z\simeq 10.6$ and $z\simeq 12.3$, respectively. The total number of galaxies discovered at $z>9$ is in line with the predictions of a non-evolving LF. The two bright ones at $z>10$ are unexpected given the survey volume, although cosmic variance and small number statistics limits general conclusions. This first search demonstrates the unique power of JWST to discover galaxies at the high redshift frontier. The candidates are ideal targets for spectroscopic follow-up in cycle$-2$.

One of the brightest objects in the universe, supernovae (SNe) are powerful explosions marking the end of a star's lifetime. Supernova (SN) type is defined by spectroscopic emission lines, but obtaining spectroscopy is often logistically unfeasible. Thus, the ability to identify SNe by type using time-series image data alone is crucial, especially in light of the increasing breadth and depth of upcoming telescopes. We present a convolutional neural network method for fast supernova time-series classification, with observed brightness data smoothed in both the wavelength and time directions with Gaussian process regression. We apply this method to full duration and truncated SN time-series, to simulate retrospective as well as real-time classification performance. Retrospective classification is used to differentiate cosmologically useful Type Ia SNe from other SN types, and this method achieves >99% accuracy on this task. We are also able to differentiate between 6 SN types with 60% accuracy given only two nights of data and 98% accuracy retrospectively.

Ultraluminous X-ray sources (ULXs) are a class of accreting compact objects with X-ray luminosities above 10$^{39}$ erg s$^{-1}$. The average number of ULXs per galaxy is still not well constrained, especially given the uncertainty on the fraction of ULX transients. Here, we report the identification of a new transient ULX in the galaxy NGC 55 (which we label as ULX-2), thanks to recent XMM-Newton and the Neil Gehrels Swift Observatory observations. This object was previously classified as a transient X-ray source with a luminosity around a few 10$^{38}$ erg s$^{-1}$ in a 2010 XMM-Newton observation. Thanks to new and deeper observations ($\sim$ 130 ks each), we show that the source reaches a luminosity peak $>1.6 \times 10^{39}$ erg s$^{-1}$. The X-ray spectrum of ULX-2 is much softer than in previous observations and fits in the class of soft ULXs. It can be well described using a model with two thermal components, as often found in ULXs. The time scales of the X-ray variability are of the order of a month and are likely driven by small changes in the accretion rate or due to super-orbital modulations, attributed to precession of the accretion disc, which is similar to other ULXs.

The equation for canonical gravity produced by Wheeler and deWitt in the late 1960s still presents difficulties both in terms of its mathematical solution and physical interpretation. One of these issues is, notoriously, the absence of an explicit time. In this short note, we suggest one simple and straightforward way to avoid this. We go back to the classical equation that inspired Wheeler and deWitt, namely the Hamilton-Jacobi-Einstein equation, and make explicit before quantization the presence of a known, classically meaningful notion of time, by a allowing Hamilton's principal function to be explicitely dependent on this time locally. This choice results in a Wheeler-deWitt equation with time. A working solution for the de Sitter minisuperspace is shown.

Over the last couple of decades, there are direct and indirect evidences for massive compact objects than their conventional counterparts. A couple of such examples are super-Chandrasekhar white dwarfs and massive neutron stars. The observations of more than a dozen peculiar over-luminous type Ia supernovae predict their origins from super-Chandrasekhar white dwarf progenitors. On the other hand, recent gravitational wave detection and some pulsar observations argue for massive neutron stars, lying in the famous mass-gap between lowest astrophysical black hole and conventional highest neutron star masses. We show that the idea of a squashed fuzzy sphere, which brings in noncommutative geometry, can self-consistently explain either of the massive objects as if they are actually fuzzy or squashed fuzzy spheres. Noncommutative geometry is a branch of quantum gravity. If the above proposal is correct, it will provide observational evidences for noncommutativity.

It is shown that a component of the dynamical affine connection, which is independent of the metric, can drive inflation in agreement with observations. This provides a geometrical origin for the inflaton. It is also found that the decays of this field, which has spin 0 and odd parity, into Higgs bosons can reheat the universe up to a sufficiently high temperature.

We present a rotating regular black hole whose inner horizon has zero surface gravity for any value of the spin parameter, and is therefore stable against mass inflation. Our metric is built by combining two successful strategies for regularizing singularities, i.e. by replacing the mass parameter with a function of $r$ and by introducing a conformal factor. The mass function controls the properties of the inner horizon, whose displacement away from the Kerr geometry's inner horizon is quantified in terms of a parameter $e$; while the conformal factor regularizes the singularity in a way that is parametrized by the dimensionful quantity $b$. The resulting line element not only avoids the stability issues that are common to regular black hole models endowed with inner horizons, but is also free of problematic properties of the Kerr geometry, such as the existence of closed timelike curves. While the proposed metric has all the phenomenological relevant features of singular rotating black holes -- such as ergospheres, light ring and innermost stable circular orbit -- showing a remarkable similarity to a Kerr black hole in its exterior, it allows nonetheless sizable deviations, especially for large values of the spin parameter $a$. In this sense, the proposed rotating ``inner-degenarate'' regular black hole solution is not only amenable to further theoretical investigations but most of all can represent a viable geometry to contrast to the Kerr one in future phenomenological tests.

We revisit the Kodama state by quantizing the theory of General Relativity (GR) with dynamical Chern-Simons (dCS) gravity. We find a new exact solution to the Wheeler-DeWitt equation where the Pontryagin term induces a modification in the Kodama state from quantizing GR alone. The dCS modification directly encodes the variation of the cosmological constant $\Lambda$.

Use of curvilinear coordinates is sometimes indicated by the inherent geometry of a fluid dynamics problem, but this introduces fictitious forces into the momentum equations that spoil strict conservative form. If one is willing to work in three dimensions, these fictitious forces can be eliminated by solving for rectangular (Cartesian) momentum components on a curvilinear mesh. A thoroughly geometric approach to fluid dynamics on spacetime demonstrates this transparently, while also giving insight into a greater unity of the relativistic and nonrelativistic cases than is usually appreciated.

Scorpius X-1 (Sco X-1) has long been considered one of the most promising targets for detecting continuous gravitational waves with ground-based detectors. Observational searches for Sco X-1 have achieved substantial sensitivity improvements in recent years, to the point of starting to rule out emission at the torque-balance limit in the low-frequency range \sim 40--180 Hz. In order to further enhance the detection probability, however, there is still much ground to cover for the full range of plausible signal frequencies \sim 20--1500 Hz, as well as a wider range of uncertainties in binary orbital parameters. Motivated by this challenge, we have developed BinaryWeave, a new search pipeline for continuous waves from a neutron star in a known binary system such as Sco X-1. This pipeline employs a semi-coherent StackSlide F-statistic using efficient lattice-based metric template banks, which can cover wide ranges in frequency and unknown orbital parameters. We present a detailed timing model and extensive injection-and-recovery simulations that illustrate that the pipeline can achieve high detection sensitivities over a significant portion of the parameter space when assuming sufficiently large (but realistic) computing budgets. Our studies further underline the need for stricter constraints on the Sco X-1 orbital parameters from electromagnetic observations, in order to be able to push sensitivity below the torque-balance limit over the entire range of possible source parameters.

This paper presents a highly robust third-order accurate finite volume weighted essentially non-oscillatory (WENO) method for special relativistic hydrodynamics on unstructured triangular meshes. We rigorously prove that the proposed method is physical-constraint-preserving (PCP), namely, always preserves the positivity of the pressure and the rest-mass density as well as the subluminal constraint on the fluid velocity. The method is built on a highly efficient compact WENO reconstruction on unstructured meshes, a simple PCP limiter, the provably PCP property of the Harten--Lax--van Leer flux, and third-order strong-stability-preserving time discretization. Due to the relativistic effects, the primitive variables (namely, the rest-mass density, velocity, and pressure) are highly nonlinear implicit functions in terms of the conservative variables, making the design and analysis of our method nontrivial. To address the difficulties arising from the strong nonlinearity, we adopt a novel quasilinear technique for the theoretical proof of the PCP property. Three provable convergence-guaranteed iterative algorithms are also introduced for the robust recovery of primitive quantities from admissible conservative variables. We also propose a slight modification to an existing WENO reconstruction to ensure the scaling invariance of the nonlinear weights and thus to accommodate the homogeneity of the evolution operator, leading to the advantages of the modified WENO reconstruction in resolving multi-scale wave structures. Extensive numerical examples are presented to demonstrate the robustness, expected accuracy, and high resolution of the proposed method.

This paper designs and analyzes positivity-preserving well-balanced (WB) central discontinuous Galerkin (CDG) schemes for the Euler equations with gravity. A distinctive feature of these schemes is that they not only are WB for a general known stationary hydrostatic solution, but also can preserve the positivity of the fluid density and pressure. The standard CDG method does not possess this feature, while directly applying some existing WB techniques to the CDG framework may not accommodate the positivity and keep other important properties at the same time. In order to obtain the WB and positivity-preserving properties simultaneously while also maintaining the conservativeness and stability of the schemes, a novel spatial discretization is devised in the CDG framework based on suitable modifications to the numerical dissipation term and the source term approximation. The modifications are based on a crucial projection operator for the stationary hydrostatic solution, which is proposed for the first time in this work. This novel projection has the same order of accuracy as the standard $L^2$-projection, can be explicitly calculated, and is easy to implement without solving any optimization problems. More importantly, it ensures that the projected stationary solution has the same cell averages on both the primal and dual meshes, which is a key to achieve the desired properties of our schemes. Based on some convex decomposition techniques, rigorous positivity-preserving analyses for the resulting WB CDG schemes are carried out. Several one- and two-dimensional numerical examples are performed to illustrate the desired properties of these schemes, including the high-order accuracy, the WB property, the robustness for simulations involving the low pressure or density, high resolution for the discontinuous solutions and the small perturbations around the equilibrium state.

We use Swampland principles to theoretically disfavor regions of the parameter space of dark matter and other darkly charged particles that may exist. The Festina Lente bound, the analogue of the Weak-Gravity conjecture in de Sitter, places constraints on the mass and charge of dark particles, which here we show cover regions in parameter space that are currently allowed by observations. As a consequence, a broad set of new ultra-light particles are in the Swampland, independently of their cosmic abundance, showing the complementarity of Quantum Gravity limits with laboratory and astrophysical studies. In parallel, a Swampland bound on the UV cutoff associated to the axion giving a St\"{u}ckelberg photon its longitudinal mode translates to a new constraint on the kinetic mixings and masses of dark photons. This covers part of the parameter space targeted by upcoming dark-photon direct-detection experiments. Moreover, it puts astrophysically interesting models in the Swampland, including freeze-in dark matter through an ultra-light dark photon, as well as radio models invoked to explain the 21-cm EDGES anomaly.