Papers for Monday, Jul 19 2021

In the spirit of Trimble's ``Astrophysics in XXXX'' series, I very briefly and subjectively review developments in SETI in 2020. My primary focus is 74 papers and books published or made public in 2020, which I sort into six broad categories: results from actual searches, new search methods and instrumentation, target and frequency seleciton, the development of technosignatures, theory of ETIs, and social aspects of SETI.

Magnetically-driven hotspot variations (which are tied to atmospheric wind variations) in hot Jupiters are studied using non-linear numerical simulations of a shallow-water magnetohydrodynamic (SWMHD) system and a linear analysis of equatorial SWMHD waves. In hydrodynamic models, mid-to-high latitude geostrophic circulations are known to cause a net west-to-east equatorial thermal energy transfer, which drives hotspot offsets eastward. We find that a strong toroidal magnetic field can obstruct these energy transporting circulations. This results in winds aligning with the magnetic field and generates westward Lorentz force accelerations in hotspot regions, ultimately causing westward hotspot offsets. In the subsequent linear analysis we find that this reversal mechanism has an equatorial wave analogy in terms of the planetary scale equatorial magneto-Rossby waves. We compare our findings to three-dimensional MHD simulations, both quantitively and qualitatively, identifying the link between the mechanics of magnetically-driven hotspot and wind reversals. We use the developed theory to identify physically-motivated reversal criteria, which can be used to place constraints on the magnetic fields of ultra-hot Jupiters with observed westward hotspots.

We present new two-fluid models of accretion disks in active galactic nuclei (AGN) that aim to address the long-standing problem of Toomre instability in AGN outskirts. In the spirit of earlier work by Sirko & Goodman 2003, and others, we argue that Toomre instability is eventually self-regulated via feedback produced by fragmentation and its aftermath. Unlike past semi-analytic models, which (i) adopt local prescriptions to connect star formation rates to heat feedback, and (ii) assume that AGN disks self-regulate to a star-forming steady state (with Toomre parameter Q=1), we find that feedback processes are both temporally and spatially non-local. The accumulation of many stellar-mass black holes (BHs) embedded in AGN gas eventually displaces radiation, winds and supernovae from massive stars as the dominant feedback source. The delay inherent in BH formation as well as their subsequent migration causes local heating rates to have little correlation with local star formation rates. The non-locality of feedback heating, in combination with the need for heat to efficiently mix throughout the gas, gives rise to steady-state AGN solutions that can have Q>>1 and no ongoing star formation. We explore the implications of our two-fluid disk models for the evolution of compact object populations embedded in AGN disks, and find self-consistent steady state solutions in much of the parameter space of AGN mass and accretion rate. These solutions harbor large populations of embedded compact objects which may grow in mass by factors of a few over the AGN lifetime, including into the lower and upper mass gaps. These feedback-dominated AGN disks differ significantly in structure from commonly used 1D disk models, which has broad implications for gravitational wave source formation inside AGN.

The community may be on the verge of detecting low-frequency gravitational waves from massive black hole binaries (MBHBs), but no examples of binary active galactic nuclei (AGN) have been confirmed. Because MBHBs are intrinsically rare, the most promising detection methods utilize photometric data from all-sky surveys. Recently D'Orazio & Di Stefano 2018 (arXiv:1707.02335) suggested gravitational self-lensing as a method of detecting AGN in close separation binaries. In this study we calculate the detectability of lensing signatures in realistic populations of simulated MBHBs. Within our model assumptions, we find that VRO's LSST should be able to detect 10s to 100s of self-lensing binaries, with the rate uncertainty depending primarily on the orientation of AGN disks relative to their binary orbits. Roughly a quarter of lensing detectable systems should also show detectable Doppler boosting signatures. If AGN disks tend to be aligned with the orbit, lensing signatures are very nearly achromatic, while in misaligned configurations the bluer optical bands are lensed more than redder ones. Whether substantial obscuring material (e.g.~a dusty torus) will be present in close binaries remains uncertain, but our estimates suggest that a substantial fraction of systems would still be observable in this case.

The MagAO-X instrument is a new extreme adaptive optics system for high-contrast imaging at visible and near-infrared wavelengths on the Magellan Clay Telescope. A central component of this system is a 2040-actuator microelectromechanical deformable mirror (DM) from Boston Micromachines Corp. that operates at 3.63 kHz for high-order wavefront control (the tweeter). Two additional DMs from ALPAO perform the low-order (the woofer) and non-common-path science-arm wavefront correction (the NCPC DM). Prior to integration with the instrument, we characterized these devices using a Zygo Verifire Interferometer to measure each DM surface. We present the results of the characterization effort here, demonstrating the ability to drive tweeter to a flat of 6.9 nm root mean square (RMS) surface (and 0.56 nm RMS surface within its control bandwidth), the woofer to 2.2 nm RMS surface, and the NCPC DM to 2.1 nm RMS surface over the MagAO-X beam footprint on each device. Using focus-diversity phase retrieval on the MagAO-X science cameras to estimate the internal instrument wavefront error (WFE), we further show that the integrated DMs correct the instrument WFE to 18.7 nm RMS, which, combined with a 11.7% pupil amplitude RMS, produces a Strehl ratio of 0.94 at H$\alpha$.

The Yakutsk Extensive Air Shower Array has been continuously operating for more than 50 years (since 1970) and up until recently it has been one of world's largest ground-based instruments aimed at studying the properties of cosmic rays in the ultra-high energy domain. In this report we discuss results recently obtained at the array - on cosmic rays energy spectrum, mass composition and directional anisotropy - and how they fit into the world data. Special attention is paid to the measurements of muonic component of extensive air showers. Theoretical results of particle acceleration at shocks are also briefly reviewed. Future scientific and engineering plans on the array modernization are discussed.

Recent ground and space-based observations show that stars with multiple planets are common in the galaxy. Most of these observational methods are biased toward detecting large planets near to their host stars. Because of these observational biases, these systems can hide small, close-in planets or far-orbiting (big or small) companions. These planets can still exert dynamical influence on known planets and have such influence exerted upon them in turn. In certain configurations, this influence can destabilize the system; in others, the star's gravitational influence can instead further stabilize the system. For example, in systems with planets close to the host star, effects arising from general relativity can help to stabilize the configuration. We derive criteria for hidden planets orbiting both beyond and within known planets that quantify how strongly general relativistic effects can stabilize systems that would otherwise be unstable. As a proof-of-concept, we investigate the several planets around the star Kepler 56, show that the outermost planet will not disrupt the system, and show that an Earth-radius planet could be stable within this system if it orbits below $0.08$ au. Furthermore, we provide specific predictions to known observed systems by constraining the parameter space of possible hidden planets.

Survey telescopes such as the Vera C. Rubin Observatory will increase the number of observed supernovae (SNe) by an order of magnitude, discovering millions of events; however, it is impossible to spectroscopically confirm the class for all the SNe discovered. Thus, photometric classification is crucial but its accuracy depends on the not-yet-finalized observing strategy of Rubin Observatory's Legacy Survey of Space and Time (LSST). We quantitatively analyze the impact of the LSST observing strategy on SNe classification using the simulated multi-band light curves from the Photometric LSST Astronomical Time-Series Classification Challenge (PLAsTiCC). First, we augment the simulated training set to be representative of the photometric redshift distribution per supernovae class, the cadence of observations, and the flux uncertainty distribution of the test set. Then we build a classifier using the photometric transient classification library snmachine, based on wavelet features obtained from Gaussian process fits, yielding similar performance to the winning PLAsTiCC entry. We study the classification performance for SNe with different properties within a single simulated observing strategy. We find that season length is an important factor, with light curves of 150 days yielding the highest classification performance. Cadence is also crucial for SNe classification; events with median inter-night gap of <3.5 days yield higher performance. Interestingly, we find that large gaps (>10 days) in light curve observations does not impact classification performance as long as sufficient observations are available on either side, due to the effectiveness of the Gaussian process interpolation. This analysis is the first exploration of the impact of observing strategy on photometric supernova classification with LSST.

For over 60 years, the scientific community has studied actively growing central super-massive black holes (active galactic nuclei -- AGN) but fundamental questions on their genesis remain unanswered. Numerical simulations and theoretical arguments show that black hole growth occurs during short-lived periods ($\sim$ 10$^{7}$ -10$^{8}$ yr) of powerful accretion. Major mergers are commonly invoked as the most likely dissipative process to trigger the rapid fueling of AGN. If the AGN-merger paradigm is true, we expect galaxy mergers to coincide with black hole accretion during a heavily obscured AGN phase (N$_H$ $ > 10^{23}$ cm$^{-2}$). Starting from one of the largest samples of obscured AGN at 0.5 $<$ $z$ $<$ 3.1, we select 40 non-starbursting lower-luminosity obscured AGN. We then construct a one-to-one matched redshift- and near-IR magnitude-matched non-starbursting inactive galaxy control sample. Combining deep color \textit{Hubble Space Telescope} imaging and a novel method of human classification, we test the merger-AGN paradigm prediction that heavily obscured AGN are strongly associated with galaxies undergoing a major merger. On the total sample of 80 galaxies, we estimate each individual classifier's accuracy at identifying merging galaxies/post-merging systems and isolated galaxies. We calculate the probability of each galaxy being in either a major merger or isolated system, given the accuracy of the human classifiers and the individual classifications of each galaxy. We do not find statistically significant evidence that obscured AGN at cosmic noon are predominately found in systems with evidence of significant merging/post-merging features.

Atmospheric escape from close-in exoplanets is thought to be crucial in shaping observed planetary populations. Recently, significant progress has been made in observing this process in action through excess absorption in transit spectra and narrowband light curves. We present a 3D hydrodynamic simulation and radiative transfer post-processing method for modeling the interacting flows of escaping planetary atmosphere and stellar winds. We focus on synthetic transmission spectra of the helium 1083 nm line, and discuss a planetary outflow of fixed mass-loss rate that interacts with stellar winds of varying order of magnitude. The morphology of these outflows in differing stellar wind environments changes dramatically, from torii that completely encircle the star when the ram pressure of the stellar wind is low, to cometary tails of planetary outflow when the stellar wind ram pressure is high. Our results demonstrate that this interaction leaves important traces on line kinematics and spectral phase curves in the helium 1083 nm triplet. In particular, the confinement of outflows through wind--wind collisions leads to absorption that extends in phase and time well beyond the optical transit. We further demonstrate that these differences are reflected in light curves of He 1083 nm equivalent width as a function of transit phase. Our results suggest that combining high-resolution spectroscopy with narrowband photometry offers a path to observationally probe how stellar wind environments shape exoplanetary atmosphere escape.

We perform a general test of the $\Lambda{\rm CDM}$ and $w {\rm CDM}$ cosmological models by comparing constraints on the geometry of the expansion history to those on the growth of structure. Specifically, we split the total matter energy density, $\Omega_M$, and (for $w {\rm CDM}$) dark energy equation of state, $w$, into two parameters each: one that captures the geometry, and another that captures the growth. We constrain our split models using current cosmological data, including type Ia supernovae, baryon acoustic oscillations, redshift space distortions, gravitational lensing, and cosmic microwave background (CMB) anisotropies. We focus on two tasks: (i) constraining deviations from the standard model, captured by the parameters $\Delta\Omega_M \equiv \Omega_M^{\rm grow}-\Omega_M^{\rm geom}$ and $\Delta w \equiv w^{\rm grow}-w^{\rm geom}$, and (ii) investigating whether the $S_8$ tension between the CMB and weak lensing can be translated into a tension between geometry and growth, i.e. $\Delta\Omega_M \neq 0$, $\Delta w \neq 0$. In both the split $\Lambda{\rm CDM}$ and $w {\rm CDM}$ cases, our results from combining all data are consistent with $\Delta\Omega_M = 0$ and $\Delta w = 0$. If we omit BAO/RSD data and constrain the split $w {\rm CDM}$\ cosmology, we find the data prefers $\Delta w<0$ at $3.6\sigma$ significance and $\Delta\Omega_M>0$ at $4.2\sigma$ evidence. We also find that for both CMB and weak lensing, $\Delta\Omega_M$ and $S_8$ are correlated, with CMB showing a slightly stronger correlation. The general broadening of the contours in our extended model does alleviate the $S_8$ tension, but the allowed nonzero values of $\Delta\Omega_M$ do not encompass the $S_8$ values that would point toward a mismatch between geometry and growth as the origin of the tension.

Recently, cosmic rays (CRs) have emerged as a leading candidate for driving galactic winds. Small-scale processes can dramatically affect global wind properties. We run two-moment simulations of CR streaming to study how sound waves are driven unstable by phase-shifted CR forces and CR heating. We verify linear theory growth rates. As the sound waves grow non-linear, they steepen into a quasi-periodic series of propagating shocks; the density jumps at shocks create CR bottlenecks. The depth of a propagating bottleneck depends on both the density jump and its velocity; {\Delta}P_c is smaller for rapidly moving bottlenecks. A series of bottlenecks creates a CR staircase structure, which can be understood from a convex hull construction. The system reaches a steady state between growth of new perturbations, and stair mergers. CRs are decoupled at plateaus, but exert intense forces and heating at stair jumps. The absence of CR heating at plateaus leads to cooling, strong gas pressure gradients and further shocks. If bottlenecks are stationary, they can drastically modify global flows; if their propagation times are comparable to dynamical times, their effects on global momentum and energy transfer are modest. The CR acoustic instability is likely relevant in thermal interfaces between cold and hot gas, as well as galactic winds. Similar to increased opacity in radiative flows, the build-up of CR pressure due to bottlenecks can significantly increase mass outflow rates, by up to an order of magnitude. It seeds unusual forms of thermal instability, and the shocks could have distinct observational signatures.

Symbiotic stars are long-period interacting binaries where the compact objects, most commonly a white dwarf, is embedded in the dense stellar wind of an evolved companion star. UV and soft X-ray emission of the accretion disk and nuclear burning white dwarf plays a major role in shaping the ionisation balance of the surrounding wind material and giving rise to the rich line emission. In this paper, we employ 2D photoionisation calculations based on Cloudy code to study the ionisation state of the circumbinary material in symbiotic systems and to predict their emission line spectra. Our simulations are parameterized via the orbital parameters of the binary and the wind mass-loss rate of the donor star, while the mass accretion rate, temperature and luminosity of the WD are computed self-consistently. We explore the parameter space of symbiotic binaries and compute luminosities of various astrophysicaly important emission lines. The line ratios are compared to the traditional diagnostic diagrams used to distinguish symbiotic binaries from other types of sources and it is shown how the binary system parameters shape these diagrams. In the significant part of the parameter space the wind material is nearly fully ionized, except for the "shadow" behind the donor star, thus the WD emission is typically freely escaping the system

Observations by LIGO--Virgo of binary black hole mergers suggest a possible anti-correlation between black hole mass ratio ($q=m_{2}/m_{1}$) and the effective inspiral spin parameter $\chi_{\rm eff}$, the mass-weighted spin projection onto the binary orbital angular momentum (Callister et al. 2021). We show that such an anti-correlation can naturally occur for binary black holes assembled in active galactic nuclei (AGN) due to spherical and planar symmetry-breaking effects. We describe a phenomenological model in which: 1) heavier black holes live in the AGN disk and tend to spin up into alignment with the disk; 2) lighter black holes with random spin orientations live in the nuclear spheroid; 3) the AGN disk is dense enough to rapidly capture a fraction of the spheroid component. but small in radial extent to limit the number of bulk disk mergers; 4) migration within the disk is non-uniform, likely disrupted by feedback from migrators or disk turbulence; 5) dynamical encounters in the disk are common and preferentially disrupt binaries that are retrograde around their center of mass, particularly at stalling orbits, or traps. This model may explain trends in LIGO--Virgo data while offering falsifiable predictions. Comparisons of predictions in ($q,\chi_{\rm eff}$) parameter space for the different channels may allow us to distinguish their fractional contributions to the observed merger rates.

We use a geometric method to derive (two-dimensional) separation functions amongst pairs of objects within populations of specified position function $\mathrm{d} N/\mathrm{d} \vec{R}$. We present analytic solutions for separation functions corresponding to a uniform surface density within a circular field, a Plummer sphere (viewed in projection), and the mixture thereof -- including contributions from binary objects within both sub-populations. These results enable inferences about binary object populations via direct modeling of object position and pair separation data, without resorting to standard estimators of the two-point correlation function. Analyzing mock data sets designed to mimic known dwarf spheroidal galaxies, we demonstrate the ability to recover input properties including the number of wide binary star systems and, in cases where the number of resolved binary pairs is assumed to be $\gtrsim$ a few hundred, characteristic features (e.g., steepening and/or truncation) of their separation function. Combined with forthcoming observational capabilities, this methodology opens a window onto the formation and/or survival of wide binary populations in dwarf galaxies, and offers a novel probe of dark matter substructure on the smallest galactic scales.

Scattered light noise affects the sensitivity of gravitational waves detectors. The characterization of such noise is needed to mitigate it. The time-varying filter empirical mode decomposition algorithm is suitable for identifying signals with time-dependent frequency such as scattered light noise (or scattering). We present a fully automated pipeline based on the pytvfemd library, a python implementation of the tvf-EMD algorithm, to identify objects inducing scattering in the gravitational-wave channel with their motion. The pipeline application to LIGO Livingston O3 data shows that most scattering noise is due to the penultimate mass at the end of the X-arm of the detector (EXPUM) and with a motion in the micro-seismic frequency range.

Context: The pre-main sequence evolution is often simplified by choosing classical initial models. These have large initial radii and sufficient uniform contraction to make them fully convective. Contrary to that, real stars are born as small protostellar seeds in collapsing molecular clouds and obtain their final mass by means of accretion. Aims: We aim to constrain the input physics of accretion on protostellar seeds with observed spectroscopic parameters and stellar pulsations of young stellar objects and pre-main sequence stars. Methods: We conducted a literature search for spectroscopic samples of young stellar objects and pre-main sequence stars including all previously known pulsators. The sample size of pulsating pre-main sequence stars is increased by analysing TESS observations and presenting discoveries in CoRoT data. We employ MESA and GYRE to calculate evolutionary tracks of accreting protostellar seeds in a constant accretion scenario, the subsequent pre-main sequence evolution, and their pulsation properties. The results are then compared with observations to constrain the input physics. Results: We discuss 16 formerly unknown pulsating pre-main sequence stars and candidates that are either of SPB, $\delta$ Scuti,$\gamma$ Doradus or $\delta$ Scuti - $\gamma$ Doradus hybrid type. We find that evolutionary tracks with a mass accretion rate of $5\times10^{-6} M_\odot/{\rm yr}$ and fraction of injected accretion energy of $\beta=0.1$ provide the best results in enveloping the spectroscopic parameters of pre-main sequence stars in a constant accretion scenario. The calculated instability regions constrain the atmospheric boundary conditions to Eddington Gray atmospheres; we discuss the future potential for additional constraints by instability regions that are dependent on radial order. We present a possible candidate for pulsations in M-type young stellar objects.

Non-gravitationally induced condensations are observed in many astrophysical environments. Such structures are formed due to energy loss by optically thin radiative emission. Instead of solving the full radiative transfer equations, precomputed cooling curves are typically used in numerical simulations. In the literature, there exists a wide variety of cooling curves and they are quite often used as unquestionable ingredients. We determine the effect of the optically thin cooling curves on the formation and evolution of condensations. We perform a case study using thermal instability as a mechanism to form in-situ condensations. We compare 2D numerical simulations with different cooling curves using interacting slow magnetohydrodynamic (MHD) waves as trigger for the thermal instability. Furthermore, we discuss a bootstrap measure to investigate the far nonlinear regime of the thermal instability. In the appendix, we include the details of all cooling curves implemented in MPI-AMRVAC and briefly discuss a hydrodynamic variant of the slow MHD waves setup for thermal instability. For all tested cooling curves, condensations are formed. However, the growth rates of the thermal instability are different. Also, the morphology of the formed condensation widely varies. We find fragmentation that is influenced by the low-temperature treatment of the cooling curves. Condensations formed using cooling curves that vanish for temperatures lower than 20 000 K seem to be more stable against dynamical instabilities. The nonlinear regime and fragmentation in the hydrodynamic case differ greatly from the MHD case. We advocate the use of modern cooling curves, based on accurate computations and up-to-date atomic parameters and solar abundances. Our bootstrap procedure can be used in future multi-dimensional simulations, to study fine-structure dynamics in solar prominences.

We obtained polarimetric differential imaging of a gas-rich debris disk around HD 141569A with SPHERE in the H-band to compare the scattering properties of the innermost ring at 44 au with former observations in total intensity with the same instrument. In polarimetric imaging, we observed that the intensity of the ring peaks in the south-east, mostly in the forward direction, whereas in total intensity imaging, the ring is detected only at the south. This noticeable characteristic suggests a non-uniform dust density in the ring. We implemented a density function varying azimuthally along the ring and generated synthetic images both in polarimetry and in total intensity, which are then compared to the actual data. We find that the dust density peaks in the south-west at an azimuthal angle of $220^{\circ} \sim 238^{\circ}$ with a rather broad width of $61^{\circ} \sim 127^{\circ}$. Although there are still uncertainties that remain in the determination of the anisotropic scattering factor, the implementation of an azimuthal density variation to fit the data proved to be robust. Upon elaborating on the origin of this dust density distribution, we conclude that it could be the result of a massive collision when we account for the effect of the high gas mass that is present in the system on the dynamics of grains. Using the outcome of this modelization, we further measured the polarized scattering phase function for the observed scattering angle between 33$^{\circ}$ and 147$^{\circ}$ as well as the spectral reflectance of the southern part of the ring between 0.98 $\mu$m and 2.1 $\mu$m. We tentatively derived the grain properties by comparing these quantities with MCFOST models and assuming Mie scattering. Our preliminary interpretation indicates a mixture of porous sub-micron sized astro-silicate and carbonaceous grains.

There exists a number of astronomical spectral phenomena that have remained unidentified after decades of extensive observations. The diffuse interstellar bands, the 220 nm feature, unidentified infrared emission bands, extended red emissions, and 21 and 30 $\mu$m emission features are seen in a wide variety of astrophysical environments. The strengths of these features suggest that they originate from chemical compounds made of common elements, possibly organic in nature. The quest to understand how such organic materials are synthesized and distributed across the Galaxy represents a major challenge to our understanding of the chemical content of the Universe.

AM CVn systems are ultra-compact, helium-rich, accreting binaries with degenerate or semi-degenerate donors. We report the discovery of five new eclipsing AM CVn systems with orbital periods of 61.5, 55.5, 53.3, 37.4, and 35.4 minutes. These systems were discovered by searching for deep eclipses in the Zwicky Transient Facility (ZTF) lightcurves of white dwarfs selected using Gaia parallaxes. We obtained phase-resolved spectroscopy to confirm that all systems are AM CVn binaries, and we obtained high-speed photometry to confirm the eclipse and characterize the systems. The spectra of two long-period systems (61.5 and 53.3 minutes) show many emission and absorption lines, indicating the presence of N, O, Na, Mg, Si, and Ca, and also the K and Zn, elements which have never been detected in AM CVn systems before. By modelling the high-speed photometry, we measured the mass and radius of the donor star, potentially constraining the evolutionary channel that formed these AM CVn systems. We determined that the average mass of the accreting white dwarf is $\approx0.8$$\mathrm{M_{\odot}}$, and that the white dwarfs in long-period systems are hotter than predicted by recently updated theoretical models. The donors have a high entropy and are a factor of $\approx$ 2 more massive compared to zero-entropy donors at the same orbital period. The large donor radius is most consistent with He-star progenitors, although the observed spectral features seem to contradict this. The discovery of 5 new eclipsing AM~CVn systems is consistent with the known observed AM CVn space density and estimated ZTF recovery efficiency. Based on this estimate, we expect to find another 1--4 eclipsing AM CVn systems as ZTF continues to obtain data. This will further increase our understanding of the population, but will require high precision data to better characterize these 5 systems and any new discoveries.

The recent compilation of quasar (QSO) X-ray and UV flux measurements include QSOs that appear to not be standardizable via the X-ray luminosity and UV luminosity ($L_X-L_{UV}$) relation and so should not be used to constrain cosmological model parameters. Here we show that the largest of seven sub-samples in this compilation, the SDSS-4XMM QSOs that contribute about 2/3 of the total QSOs, have $L_X-L_{UV}$ relations that depend on the cosmological model assumed and also on redshift, and is the main cause of the similar problem discovered earlier for the full QSO compilation. The second and third biggest sub-samples, the SDSS-Chandra and XXL QSOs that together contribute about 30% of the total QSOs, appear standardizable, but provide only weak constraints on cosmological parameters that are not inconsistent with the standard spatially-flat $\Lambda$CDM model or with constraints from better-established cosmological probes.

High quality, repeatable point-spread functions are important for science cases like direct exoplanet imaging, high-precision astrometry, and high-resolution spectroscopy of exoplanets. For such demanding applications, the initial on-sky point-spread function delivered by the adaptive optics system can require further optimization to correct unsensed static aberrations and calibration biases. We investigated using the Fast and Furious focal-plane wavefront sensing algorithm as a potential solution. This algorithm uses a simple model of the optical system and focal plane information to measure and correct the point-spread function phase, without using defocused images, meaning it can run concurrently with science. On-sky testing demonstrated significantly improved PSF quality in only a few iterations, with both narrow and broadband filters. These results suggest this algorithm is a useful path forward for creating and maintaining high-quality, repeatable on-sky adaptive optics point-spread functions.

Constraining the frequency of energy deposition in magnetically-closed active region cores requires sophisticated hydrodynamic simulations of the coronal plasma and detailed forward modeling of the optically-thin line-of-sight integrated emission. However, understanding which set of model inputs best matches a set of observations is complicated by the need for any proposed heating model to simultaneously satisfy multiple observable constraints. In this paper, we train a random forest classification model on a set of forward-modeled observable quantities, namely the emission measure slope, the peak temperature of the emission measure distribution, and the time lag and maximum cross-correlation between multiple pairs of AIA channels. We then use our trained model to classify the heating frequency in every pixel of active region NOAA 1158 using the observed emission measure slopes, peak temperatures, time lags, and maximum cross-correlations and are able to map the heating frequency across the entire active region. We find that high-frequency heating dominates in the inner core of the active region while intermediate frequency dominates closer to the periphery of the active region. Additionally, we assess the importance of each observed quantity in our trained classification model and find that the emission measure slope is the dominant feature in deciding with which heating frequency a given pixel is most consistent. The technique presented here offers a very promising and widely applicable method for assessing observations in terms of detailed forward models given an arbitrary number of observable constraints.

We study the process of the Primordial Black Holes (PBHs) production in the novel framework, namely $\alpha$-attractor Galileon inflation (G-inflation) model. In our framework, we take the Galileon function as $G(\phi)=G_{I}(\phi)\left(1+G_{II}(\phi)\right)$, where the part $G_{I}(\phi)$ is motivated from the $\alpha$-attractor inflationary scenario in its original non-canonical frame, and it ensures for the model to be consistent with the Planck 2018 observations at the CMB scales. The part $G_{II}(\phi)$ is invoked to enhance the curvature perturbations at some smaller scales which in turn gives rise to PBHs formation. By fine-tuning of the model parameters, we find three parameter sets which successfully produce a sufficiently large peak in the curvature power spectrum. We show that these parameter sets produce PBHs with masses ${\cal O}(10)M_\odot$, ${\cal O}(10^{-5})M_\odot$, and ${\cal O}(10^{-12})M_\odot$ which can explain the LIGO events, the ultrashort-timescale microlensing events in OGLE data, and around $0.98\%$ of the current Dark Matter (DM) content of the universe, respectively. Additionally, we study the secondary Gravitational Waves (GWs) in our setup and show that our model anticipates the peak of their present fractional energy density as $\Omega_{GW0} \sim 10^{-8}$ for all the three parameter sets, but at different frequencies. These predictions can be located well inside the sensitivity region of some GWs detectors, and therefore the compatibility of our model can be assessed in light of the future data. We further estimate the tilts of the included GWs spectrum in the different ranges of frequency, and confirm that spectrum follows the power-law relation $\Omega_{GW0}\sim f^{n}$ in those frequency bands.

We measure the velocity dispersions of clusters of galaxies selected by the redMaPPer algorithm in the first three years of data from the Dark Energy Survey (DES), allowing us to probe cluster selection and richness estimation, $\lambda$, in light of cluster dynamics. Our sample consists of 126 clusters with sufficient spectroscopy for individual velocity dispersion estimates. We examine the correlations between cluster velocity dispersion, richness, X-ray temperature and luminosity as well as central galaxy velocity offsets. The velocity dispersion-richness relation exhibits a bimodal distribution. The majority of clusters follow scaling relations between velocity dispersion, richness, and X-ray properties similar to those found for previous samples; however, there is a significant population of clusters with velocity dispersions which are high for their richness. These clusters account for roughly 20\% of the $\lambda < 70$ systems in our sample, but more than half of $\lambda < 70$ clusters at $z>0.5$. A couple of these systems are hot and X-ray bright as expected for massive clusters with richnesses that appear to have been underestimated, but most appear to have high velocity dispersions for their X-ray properties likely due to line-of-sight structure. These results suggest that projection effects contribute significantly to redMaPPer selection, particularly at higher redshifts and lower richnesses. The redMaPPer determined richnesses for the velocity dispersion outliers are consistent with their X-ray properties, but several are X-ray undetected and deeper data is needed to understand their nature.

I further test the theory that the Cosmic Background Radiation (CBR) is not photonic in composition. Tipler (2005) has previously argued that the consistency of the Standard Model (SM) with the Second Law of Thermodynamics requires the early universe CBR to be composed entirely of an SU(2) gauge field (pseudo-photons) instead of photons. One of the consequences of this assumption is that the Ultra High Energy Cosmic Rays (UHECRs) would be able to propagate a factor of ten further than allowed in standard theory as a pseudo-photonic CBR would be unable to couple with right-handed fermions. I test if this novel theory solves the problem of UHECR origin by finding suitable candidates up to a redshift z = 0.1 within three degrees of the arrival direction. Utilizing the Fly's Eye Northern Hemisphere UHECR data, I identified candidates with 80% success for the Northern Sky UHECR (98.7% if certain celestial objects which are likely to be Active Galactic Nuclei are absolutely identified as such). This is parsimonious with the CBR theory, which has other important implications for the Standard Model, early universe cosmology, and the origin of matter and anti-matter. This extends the work of Tipler and Piasecki (2018), where they used UHECR data from the Southern Hemisphere to get a 86% successful source identification rate. I predict that the remaining UHECR not paired with a potential source will have sources identified upon closer telescopic investigations of these regions. Other recent experiments further suggest a pseudo-photonic composition of the CBR. The problem of UHECR origin may be solved.

We analyse optical datacubes of the inner kiloparsec of 30 local ($z\le0.02$) active galactic nuclei (AGN) hosts that our research group, AGNIFS, has collected over the past decade via observations with the integral field units of the Gemini Multi-Object Spectrographs. Spatial resolutions range between $50~{\rm pc}$ and $300~{\rm pc}$ and spectral coverage is from $4800~\mathring{A}$ or $5600~\mathring{A}$ to $7000~\mathring{A}$, at velocity resolutions of $\approx 50~{\rm km~s^{-1}}$. We derive maps of the gas excitation and kinematics, determine the AGN ionisation axis -- which has random orientation relative to the galaxy, and the kinematic major axes of the emitting gas. We find that rotation dominates the gas kinematics in most cases, but is disturbed by the presence of inflows and outflows. Outflows have been found in 21 nuclei, usually along the ionisation axis. The gas velocity dispersion is traced by $W_{80}$ (velocity width encompassing 80 per cent of the line flux), adopted as a tracer of outflows. In 7 sources $W_{80}$ is enhanced perpendicularly to the ionisation axis, indicating lateral expansion of the outflow. We have estimated mass-outflow rates $\dot{M}$ and powers $\dot{E}$, finding median values of $\log\,[\dot{M}/({\rm\,M_\odot\,yr^{-1}})]=-2.1_{-1.0}^{+1.6}$ and $\log\,[\dot{E}/({\rm\,erg\,s^{-1}})]=38.5_{-0.9}^{+1.8}$, respectively. Both quantities show a mild correlation with the AGN luminosity ($L_{\rm AGN}$). $\dot{E}$ is of the order of 0.01 $L_{\rm AGN}$ for 4 sources, but much lower for the majority (9) of the sources, with a median value of $\log\,[\dot{E}/L_{\rm AGN}]=-5.34_{-0.9}^{+3.2}$ indicating that typical outflows in the local Universe are unlikely to significantly impact their host galaxy evolution.

Based on the accurate color excess $E_{\rm G_{BP},G_{RP}}$ of more than 4 million stars and $E_{\rm NUV,G_{BP}}$ of more than 1 million stars from \citet{2021ApJS..254...38S}, the distance and the extinction of the molecular clouds in the MBM catalog at $|b|>20^{\circ}$ are studied in combination with the distance measurement of \emph{Gaia}/EDR3. The distance as well as the color excess is determined for 66 molecular clouds. The color excess ratio $E_{\rm G_{BP},G_{RP}}/E_{\rm NUV,G_{BP}}$ is derived for 39 of them, which is obviously larger and implies more small particles at smaller extinction. In addition, the scale height of the dust disk is found to be about 100 pc and becomes large at the anticenter direction due to the disk flaring.

The discovery of a large number of terrestrial exoplanets in the habitable zones of their stars, many of which are qualitatively different from Earth, has led to a growing need for fast and flexible 3D climate models, which could model such planets and explore multiple possible climate states and surface conditions. We respond to that need by creating ExoPlaSim, a modified version of the Planet Simulator (PlaSim) that is designed to be applicable to synchronously rotating terrestrial planets, planets orbiting stars with non-solar spectra, and planets with non-Earth-like surface pressures. In this paper we describe our modifications, present validation tests of ExoPlaSim's performance against other GCMs, and demonstrate its utility by performing two simple experiments involving hundreds of models. We find that ExoPlaSim agrees qualitatively with more-sophisticated GCMs such as ExoCAM, LMDG, and ROCKE-3D, falling within the ensemble distribution on multiple measures. The model is fast enough that it enables large parameter surveys with hundreds to thousands of models, potentially enabling the efficient use of a 3D climate model in retrievals of future exoplanet observations. We describe our efforts to make ExoPlaSim accessible to non-modellers, including observers, non-computational theorists, students, and educators through a new Python API and streamlined installation through pip, along with online documentation.

The Fourier transform spectrometer (FTS) is a core instrument for solar observation with high spectral resolution, especially in the infrared. The Infrared System for the Accurate Measurement of Solar Magnetic Field (AIMS), working at 10-13 $\mu m$, will use a FTS to observe the solar spectrum. The Bruker IFS-125HR, which meets the spectral resolution requirement of AIMS but just equips with a point source detector, is employed to carry out preliminary experiment for AIMS. A sun-light feeding experimental system is further developed. Several experiments are taken with them during 2018 and 2019 to observe the solar spectrum in the visible and near infrared wavelength, respectively. We also proposed an inversion method to retrieve the solar spectrum from the observed interferogram and compared it with the standard solar spectrum atlas. Although there is a wavelength limitation due to the present sun-light feeding system, the results in the wavelength band from 0.45-1.0 $\mu m$ and 1.0-2.2 $\mu m$ show a good consistence with the solar spectrum atlas, indicating the validity of our observing configuration, the data analysis method and the potential to work in longer wavelength. The work provided valuable experience for the AIMS not only for the operation of a FTS but also for the development of its scientific data processing software.

Turbulence in the intracluster medium (ICM) is driven by active galactic nuclei (AGNs) jets, by mergers, and in the wakes of infalling galaxies. It not only governs gas motion but also plays a key role in the ICM thermodynamics. Turbulence can help seed thermal instability by generating density fluctuations, and mix the hot and cold phases together to produce intermediate temperature gas ($10^4$--$10^7$~$\mathrm{K}$) with short cooling times. We conduct high resolution ($384^3$--$768^3$ resolution elements) idealised simulations of the multiphase ICM and study the effects of turbulence strength, characterised by $f_{\mathrm{turb}}$ ($0.001$--$1.0$), the ratio of turbulent forcing power to the net radiative cooling rate. We analyse density and temperature distribution, amplitude and nature of gas perturbations, and probability of transitions across the temperature phases. We also study the effects of mass and volume-weighted thermal heating and weak ICM magnetic fields. For low $f_{\mathrm{turb}}$, the gas is distribution is bimodal between the hot and cold phases. The mixing between different phases becomes more efficient with increasing $f_{\mathrm{turb}}$, producing larger amounts of the intermediate temperature gas. Strong turbulence ($f_{\mathrm{turb}}\geq0.5$) generates larger density fluctuations and faster cooling, The rms logarithmic pressure fluctuation scaling with Mach number $\sigma_{\ln{\bar{P}}}^2\approx\ln(1+b^2\gamma^2\mathcal{M}^4)$ is unaffected by thermal instability and is the same as in hydro turbulence. In contrast, the density fluctuations characterised by $\sigma_s^2$ are much larger, especially for $\mathcal{M}\lesssim0.5$. In magnetohydrodynamic runs, magnetic fields provide significant pressure support in the cold phase but do not have any strong effects on the diffuse gas distribution, and nature and amplitude of fluctuations.

The Sun's axisymmetric flows, differential rotation and meridional flow, govern the dynamics of the solar magnetic cycle and variety of methods are used to measure these flows, each with its own strengths and weaknesses. Flow measurements based on cross-correlating images of the surface magnetic field have been made since the 1970s which require advanced numerical techniques that are capable of detecting movements of less than the pixel size in images of the Sun. We have identified several systematic errors in addition to the center-to-limb effect that influence previous measurements of these flows and propose numerical techniques that can minimize these errors by utilizing measurements of displacements at several time-lags. Our analysis of line-of-sight magnetograms from the {\em Michelson Doppler Imager} (MDI) on the ESA/NASA {\em Solar and Heliospheric Observatory} (SOHO) and {\em Helioseismic and Magnetic Imager} (HMI) on the NASA {\em Solar Dynamics Observatory} (SDO) shows long-term variations in the meridional flow and differential rotation over two sunspot cycles from 1996 to 2020. These improved measurements can serve as vital inputs for solar dynamo and surface flux transport simulations.

We construct a new catalog of extragalactic X-ray binaries (XRBs) by matching the latest Chandra source catalog with local galaxy catalogs. Our XRB catalog contains 4430 XRBs hosted by 237 galaxies within ~130 Mpc. As XRBs dominate the X-ray activity in galaxies, the catalog enables us to study the correlations between the total X-ray luminosity of a galaxy $L_{X,\rm tot}$, star formation rate $\dot{\rho}_\star$, and stellar mass $M_\star$. As previously reported, $L_{X,\rm tot}$ is correlated with $\dot{\rho}_\star$ and $M_\star$. In particular, we find that there is a fundamental plane in those three parameters as $\log L_{X,\rm tot}={38.80^{+0.09}_{-0.12}}+\log(\dot{\rho}_\star + \alpha M_\star)$, where $\alpha = {(3.36\pm1.40)\times10^{-11}}\ {\rm yr^{-1}}$. In order to investigate this relation, we construct a phenomenological binary population synthesis model. We find that the high mass XRB and low mass XRB fraction in formed compact object binary systems is ~9% and ~0.04%, respectively. Utilizing the latest XMM-Newton, and Swift X-ray source catalog data sets, additional XRB candidates are also found resulting in 5757 XRBs hosted by 311 galaxies.

The observed near-Earth asteroid population contains very few objects with small perihelion distances, say, q<=0.2 au. NEAs that currently have orbits with larger q might be hiding a past evolution during which they have approached closer to the Sun. We present a probabilistic assessment of the minimum q that an asteroid has reached during its orbital history. At the same time, we offer an estimate of the dwell time, that is, the time q has been in a specific range. We have re-analyzed orbital integrations of test asteroids from the moment they enter the near-Earth region until they either collide with a major body or are thrown out from the inner Solar System. We considered a total disruption of asteroids at certain q as a function of absolute magnitude (H). We calculated the probability that an asteroid with given orbital elements and H has reached a q smaller than a given threshold value and its respective dwell time in that range. We have constructed a look-up table that can be used to study the past orbital and thermal evolution of asteroids as well as meteorite falls and their possible parent bodies. An application to 25 meteorite falls shows that carbonaceous chondrites typically have short dwell times at small q, whereas for ordinary chondrites it ranges from 10,000 to 500,000 years. A dearth of meteorite falls with long dwell times and small minimum q supports a super-catastrophic disruption of asteroids at small q.

We conducted an X-ray analysis of one of the two Planck-detected triplet-cluster systems, PLCK G334.8-38.0, with a $\sim100$~ks deep XMM-Newton data. We find that the system has a redshift of $z=0.37\pm{0.01}$ but the precision of the X-ray spectroscopy for two members is too low to rule out a projected triplet system, demanding optical spectroscopy for further investigation. In projection, the system looks almost like an equilateral triangle with an edge length of $\sim2.0\,\mathrm{Mpc}$, but masses are very unevenly distributed ($M_{500} \sim [2.5,0.7,0.3] \times 10^{14}\,\mathrm{M_{\odot}}$ from bright to faint). The brightest member appears to be a relaxed cool-core cluster and is more than twice as massive as both other members combined. The second brightest member appears to be a disturbed non-cool-core cluster and the third member was too faint to make any classification. None of the clusters have an overlapping $R_{500}$ region and no signs of cluster interaction were found; however, the XMM-Newton data alone are probably not sensitive enough to detect such signs, and a joint analysis of X-ray and the thermal Sunyaev-Zeldovich effect (tSZ) is needed for further investigation, which may also reveal the presence of the warm-hot intergalactic medium (WHIM) within the system. The comparison with the other Planck-detected triplet-cluster-system (PLCK G214.6+36.9) shows that they have rather different configurations, suggesting rather different merger scenarios, under the assumption that they are both not simply projected triplet systems.

The Solar X-ray Spectrometer (XSM) payload onboard Chandrayaan-2 provides disk-integrated solar spectra in the 1-15 keV energy range with an energy resolution of 180 eV (at 5.9 keV) and a cadence of 1~second. During the period from September 2019 to May 2020, covering the minimum of Solar Cycle 24, it observed nine B-class flares ranging from B1.3 to B4.5. Using time-resolved spectroscopic analysis during these flares, we examined the evolution of temperature, emission measure, and absolute elemental abundances of four elements -- Mg, Al, Si, and S. These are the first measurements of absolute abundances during such small flares and this study offers a unique insight into the evolution of absolute abundances as the flares evolve. Our results demonstrate that the abundances of these four elements decrease towards their photospheric values during the peak phase of the flares. During the decay phase, the abundances are observed to quickly return to their pre-flare coronal values. The depletion of elemental abundances during the flares is consistent with the standard flare model, suggesting the injection of fresh material into coronal loops as a result of chromospheric evaporation. To explain the quick recovery of the so-called coronal "First Ionization Potential (FIP) bias" we propose two scenarios based on the Ponderomotive force model.

We have carried out a systematic search for galaxy-scale strong lenses in multiband imaging from the Hyper Suprime-Cam (HSC) survey. Our automated pipeline, based on realistic strong-lens simulations, deep neural network classification, and visual inspection, is aimed at efficiently selecting systems with wide image separations (Einstein radii ~1.0-3.0"), intermediate redshift lenses (z ~ 0.4-0.7), and bright arcs for galaxy evolution and cosmology. We classified gri images of all 62.5 million galaxies in HSC Wide with i-band Kron radius >0.8" to avoid strict pre-selections and to prepare for the upcoming era of deep, wide-scale imaging surveys with Euclid and Rubin Observatory. We obtained 206 newly-discovered candidates classified as definite or probable lenses with either spatially-resolved multiple images or extended, distorted arcs. In addition, we found 88 high-quality candidates that were assigned lower confidence in previous HSC searches, and we recovered 173 known systems in the literature. These results demonstrate that, aided by limited human input, deep learning pipelines with false positive rates as low as ~0.01% are not only very powerful in identifying the rare strong lenses from large catalogs, but also largely extending the samples found by traditional algorithms. We provide a ranked list of candidates for future spectroscopic confirmation.

Context. Spiral arms in protoplanetary disks could be shown to be the manifestation of density waves launched by protoplanets and propagating in the gaseous component of the disk. At least two point sources have been identified in the L band in the MWC 758 system as planetary mass object candidates. Aims. We used VLT/SPHERE to search for counterparts of these candidates in the H and K bands, and to characterize the morphology of the spiral arms . Methods. The data were processed with now-standard techniques in high-contrast imaging to determine the limits of detection, and to compare them to the luminosity derived from L band observations. Results. In considering the evolutionary, atmospheric, and opacity models we were not able to confirm the two former detections of point sources performed in the L band. In addition, the analysis of the spiral arms from a dynamical point of view does not support the hypothesis that these candidates comprise the origin of the spirals. Conclusions. Deeper observations and longer timescales will be required to identify the actual source of the spiral arms in MWC 758.

We use the stellar evolution code MESA to study the negative jet feedback mechanism in common envelope jets supernovae (CEJSNe) where a neutron star (NS) launches jets in the envelope of a red supergiant (RSG), and find that the feedback reduces the mass accretion rate to be about 0.05-0.2 times the mass accretion rate without the operation of jets. We mimic the effect of the jets on the RSG envelope by depositing the energy that the jets carry into the envelope zones outside the NS orbit. The energy deposition inflates the envelope, therefore reducing the density in the NS vicinity, which in turn reduces the mass accretion rate in a negative feedback cycle. For the canonical ratio of jets' power to actual accretion power of 0.1, and for results from numerical simulations that show the actual mass accretion rate to be a fraction of 0.1-0.5 of the Bondi-Hoyle-Lyttleton mass accretion rate, we find that the negative jet feedback coefficient (the further reduction in the accretion rate) is about 0.05-0.2, for a NS spiraling-in in the RSG envelope.

An X-ray Interferometer (XRI) has recently been proposed as a theme for ESA's Voyage 2050 planning cycle, with the eventual goal to observe the X-ray sky with an unprecedented angular resolution better than 1 micro arcsec (5 prad) [1]. A scientifically very interesting mission is possible on the basis of a single spacecraft [2], owing to the compact 'telephoto' design proposed earlier by Willingale [3]. Between the practical demonstration of X-ray interferometry at 1 keV by Cash et al. [4] with a 1 mm baseline and 0.1 arcsec effective resolution to a mission flying an interferometer with a baseline of one or more meters, an effective collecting area of square meters and micro arcsec resolution lie many milestones. The first important steps to scale up from a laboratory experiment to a viable mission concept will have to be taken on a scalable and flexible testbed set-up. Such a testbed cannot singularly focus on the optical aspects, but should simultaneously address the thermal and mechanical stability of the interferometer. A particular challenge is the coherent X-ray source, which should provide a wavefront at the entrance of the interferometer that is transversely coherent over a distance at least equal to the baseline, and bright enough. In this paper, we will explore the build-up of a testbed in several stages, with increasing requirements on optical quality and associated thermo-mechanical control and source sophistication, with the intent to guide the technological development of X-ray interferometry from the lab to space in a sequence of achievable milestones.

The first luminous objects forming in the universe produce radiation backgrounds in the FUV and X-ray bands that affect the formation of Population III stars. Using a grid of cosmological hydrodynamics zoom-in simulations, we explore the impact of the Lyman-Warner (LW) and X-ray radiation backgrounds on the critical dark matter halo mass for Population III star formation and the total mass in stars per halo. We find that the LW radiation background lowers the H$_2$ fraction and delays the formation of the Population III stars. On the other hand, X-ray irradiation anticipates the redshift of collapse and reduces the critical halo mass, unless the X-ray background is too strong and gas heating shuts down gas collapse into the halos and prevents star formation. Therefore, an X-ray background can increase the number of dark matter halos forming Population III stars by about a factor of ten, but the total mass in stars forming in each halo is reduced. This is because X-ray radiation increases the molecular fraction and lowers the minimum temperature of the collapsing gas (or equivalently the mass of the quasi-hydrostatic core) and therefore slows down the accretion of the gas onto the central protostar.

We present a new deep learning method, dubbed FibrilNet, for tracing chromospheric fibrils in Halpha images of solar observations. Our method consists of a data pre-processing component that prepares training data from a threshold-based tool, a deep learning model implemented as a Bayesian convolutional neural network for probabilistic image segmentation with uncertainty quantification to predict fibrils, and a post-processing component containing a fibril-fitting algorithm to determine fibril orientations. The FibrilNet tool is applied to high-resolution Halpha images from an active region (AR 12665) collected by the 1.6 m Goode Solar Telescope (GST) equipped with high-order adaptive optics at the Big Bear Solar Observatory (BBSO). We quantitatively assess the FibrilNet tool, comparing its image segmentation algorithm and fibril-fitting algorithm with those employed by the threshold-based tool. Our experimental results and major findings are summarized as follows. First, the image segmentation results (i.e., detected fibrils) of the two tools are quite similar, demonstrating the good learning capability of FibrilNet. Second, FibrilNet finds more accurate and smoother fibril orientation angles than the threshold-based tool. Third, FibrilNet is faster than the threshold-based tool and the uncertainty maps produced by FibrilNet not only provide a quantitative way to measure the confidence on each detected fibril, but also help identify fibril structures that are not detected by the threshold-based tool but are inferred through machine learning. Finally, we apply FibrilNet to full-disk Halpha images from other solar observatories and additional high-resolution Halpha images collected by BBSO/GST, demonstrating the tool's usability in diverse datasets.

Disc fragmentation plays an important role in determining the number of primordial stars (Pop III stars), their masses, and hence the initial mass function. In this second paper of a series, we explore the effect of uniform FUV H$_2$-photodissociating and X-ray radiation backgrounds on the formation of Pop~III stars using a grid of high-resolution zoom-in simulations. We find that, in an X-ray background, protostellar discs have lower surface density and higher Toomre $Q$ parameter, so they are more stable. For this reason, X-ray irradiated discs undergo fewer fragmentations and typically produce either binary systems or low-multiplicity systems. In contrast, the cases with weak or no X-ray irradiation produce systems with a typical multiplicity of $6 \pm 3$. In addition, the most massive protostar in each system is smaller by roughly a factor of two when the disc is irradiated by X-rays, due to lower accretion rate. With these two effects combined, the initial mass function of fragments becomes more top-heavy in a strong X-ray background and is well described by a power-law with slope $1.53$ and high-mass cutoff of $61$ M$_\odot$. Without X-rays, we find a slope $0.49$ and cutoff mass of $229$ M$_\odot$. Finally, protostars migrate outward after their formation due to the accretion of high-angular momentum gas from outside and the migration is more frequent and significant in absence of X-ray irradiation.

The Centaur (10199) Chariklo has the first rings system discovered around a small object. It was first observed using stellar occultation in 2013. Stellar occultations allow the determination of sizes and shapes with kilometre accuracy and obtain characteristics of the occulting object and its vicinity. Using stellar occultations observed between 2017 and 2020, we aim at constraining Chariklo's and its rings physical parameters. We also determine the rings' structure, and obtain precise astrometrical positions of Chariklo. We predicted and organised several observational campaigns of stellar occultations by Chariklo. Occultation light curves were measured from the data sets, from which ingress and egress times, and rings' width and opacity were obtained. These measurements, combined with results from previous works, allow us to obtain significant constraints on Chariklo's shape and rings' structure. We characterise Chariklo's ring system (C1R and C2R), and obtain radii and pole orientations that are consistent with, but more accurate than, results from previous occultations. We confirmed the detection of W-shaped structures within C1R and an evident variation of radial width. The observed width ranges between 4.8 and 9.1 km with a mean value of 6.5 km. One dual observation (visible and red) does not reveal any differences in the C1R opacity profiles, indicating ring particle's size larger than a few microns. The C1R ring eccentricity is found to be smaller than 0.022 (3-sigma), and its width variations may indicate an eccentricity higher than 0.005. We fit a tri-axial shape to Chariklo's detections over eleven occultations and determine that Chariklo is consistent with an ellipsoid with semi-axes of 143.8, 135.2 and 99.1 km. Ultimately, we provided seven astrometric positions at a milliarcseconds accuracy level, based on Gaia EDR3, and use it to improve Chariklo's ephemeris.

This work presents a new physically-motivated supervised machine learning method, Hydro-BAM, to reproduce the three-dimensional Lyman-$\alpha$ forest field in real and in redshift space learning from a reference hydrodynamic simulation, thereby saving about 7 orders of magnitude in computing time. We show that our method is accurate up to $k\sim1\,h\,\rm{Mpc}^{-1}$ in the one- (PDF), two- (power-spectra) and three-point (bi-spectra) statistics of the reconstructed fields. When compared to the reference simulation including redshift space distortions, our method achieves deviations of $\lesssim2\%$ up to $k=0.6\,h\,\rm{Mpc}^{-1}$ in the monopole, $\lesssim5\%$ up to $k=0.9\,h\,\rm{Mpc}^{-1}$ in the quadrupole. The bi-spectrum is well reproduced for triangle configurations with sides up to $k=0.8\,h\,\rm{Mpc}^{-1}$. In contrast, the commonly-adopted Fluctuating Gunn-Peterson approximation shows significant deviations already neglecting peculiar motions at configurations with sides of $k=0.2-0.4\,h\,\rm{Mpc}^{-1}$ in the bi-spectrum, being also significantly less accurate in the power-spectrum (within 5$\%$ up to $k=0.7\,h\,\rm{Mpc}^{-1}$). We conclude that an accurate analysis of the Lyman-$\alpha$ forest requires considering the complex baryonic thermodynamical large-scale structure relations. Our hierarchical domain specific machine learning method can efficiently exploit this and is ready to generate accurate Lyman-$\alpha$ forest mock catalogues covering large volumes required by surveys such as DESI and WEAVE.

In the search for life in the cosmos, transiting exoplanets are currently our best targets. In the search for life in the cosmos, transiting exoplanets are currently our best targets. With thousands already detected, our search is entering a new era of discovery with upcoming large telescopes that will look for signs of life in the atmospheres of transiting worlds. However, the universe is dynamic, and which stars in the solar neighborhood have a vantage point to see Earth as a transiting planet and can identify its vibrant biosphere since early human civilizations are unknown. Here we show that 1,715 stars within 326 light-years are in the right position to have spotted life on a transiting Earth since early human civilization, with an additional 319 stars entering this special vantage point in the next 5,000 years. Among the stars are 7 known exoplanet hosts that hold the vantage point to see Earth transit, including Ross-128, which saw Earth transit in the past, Teegarden's Star, and Trappist-1, which will start to see Earth transit in 29 and 1,642 years, respectively. We found that human-made radio waves have swept over 75 of the closest stars on our list already.

Axions are among the best motivated dark matter candidates. Their production in the early Universe by the vacuum misalignment mechanism gives rise to isocurvature perturbations, which are constrained by cosmic microwave background measurements. In this paper, we compute the axion isocurvature power spectrum using spectral expansion in the stochastic Starobinsky-Yokoyama formalism, which captures non-linear effects in the axion dynamics. In contrast to most of the existing literature, we focus on high inflationary Hubble rates of order $10^{13}~{\rm GeV}$, and demonstrate that there is a significant window in which axions can account for all or part of the dark matter abundance without violating the isocurvature bounds or tensor mode bounds. Crucially, we find that the isocurvature spectrum is dominated by non-perturbative contributions in a large part of this window. Therefore the commonly used linear approximation is not reliable in this region, making the stochastic approach essential.

By means of 3D hydrodynamic simulations, we study how Type Ia supernovae (SNe) explosions affect the star formation history and the chemical properties of second generation (SG) stars in globular clusters (GC). SG stars are assumed to form once first generation asymptotic giant branch (AGB) stars start releasing their ejecta; during this phase, external gas is accreted by the system and SNe Ia begin exploding, carving hot and tenuous bubbles. Given the large uncertainty on SNe Ia explosion times, we test two different values for the 'delay time'. We run two different models for the external gas density: in the low-density scenario with short delay time, the explosions start at the beginning of the SG star formation, halting it in its earliest phases. The external gas hardly penetrates the system, therefore most SG stars present extreme helium abundances (Y > 0.33). The low-density model with delayed SN explosions has a more extended SG star formation epoch and includes SG stars with modest helium enrichment. On the contrary, the high-density model is weakly affected by SN explosions, with a final SG mass similar to the one obtained without SNe Ia. Most of the stars form from a mix of AGB ejecta and pristine gas and have a modest helium enrichment. We show that gas from SNe Ia may produce an iron spread of $\sim 0.14$ dex, consistent with the spread found in about 20% of Galactic GCs, suggesting that SNe Ia might have played a key role in the formation of this sub-sample of GCs.

We extend our previous study (Li et al. 2021) on neutron stars with a quark core to predict the moment of inertia of pulsar A in the double pulsar binary J0737-3039, assuming there is a phase transition in the pulsar inner core from the soft QMF or the stiff DD2 hadronic equation of state (EOS) to a high-density phase of quark matter modelled by the generic "constant-sound-speed" (CSS) parameterization. We perform a Bayesian analysis of the moment of inertia by incorporating observational data for the tidal deformability of the GW170817 and GW190425 binary neutron star mergers, as detected by LIGO/Virgo, and the mass and radius of PSR J0030+0451 and MSP J0740+6620, as detected by the Neutron Star Interior Composition Explorer. We find that the most probable values of the moment of inertia of PSR J0737-3039 A are $1.27_{-0.14}^{+0.18}\times10^{45}\,{\rm g\,cm^2}$ for QMF+CSS and similarly $1.29_{-0.15}^{+0.26}\times10^{45}\,{\rm g\,cm^2}$ for DD2+CSS at $90\%$ credible interval. We also demonstrate how a moment of inertia measurement would improve our knowledge of the EOS and the mass-radius relation for hybrid stars and discuss whether a quark deconfinement phase transition is supported by the available data and forthcoming data that could be consistent with this hypothesis.

The eccentricity of binary black hole mergers is predicted to be an indicator of the history of their formation. In particular, eccentricity is a strong signature of dynamical formation rather than formation by stellar evolution in isolated stellar systems. It has been shown that searches for eccentric signals with quasi-circular templates can lead to loss of SNR, and some signals could be missed by such a pipeline. We investigate the efficacy of the existing quasi-circular parameter estimation pipelines to determine the source parameters of such eccentric systems. We create a set of simulated signals with eccentricity up to 0.3 and find that as the eccentricity increases, the recovered mass parameters are consistent with those of a binary with up to a $\approx 10\%$ higher chirp mass and mass ratio closer to unity. We also employ a full inspiral-merger-ringdown waveform model to perform parameter estimation on two gravitational wave events, GW151226 and GW170608, to investigate this bias on real data. We find that the correlation between the masses and eccentricity persists in real data, but that there is also a correlation between the measured eccentricity and effective spin. In particular, using a non-spinning prior results in a spurious eccentricity measurement for GW151226. Performing parameter estimation with an aligned spin, eccentric model, we constrain the eccentricities of GW151226 and GW170608 to be $<0.15$ and $<0.12$ respectively.

The number of known variable stars has increased by several magnitudes over the last decade, and automated classification routines are becoming increasingly important to cope with this development. Here we show that the "upside-down CBH variables", which were proposed as a potentially new class of variable stars by Heinze et al. (2018) in the ATLAS First Catalogue of Variable Stars, are, at least to a high percentage, made up of alpha2 Canum Venaticorum (ACV) variables - that is, photometrically variable magnetic chemically peculiar (CP2/He-peculiar) stars - with distinct double-wave light curves. Using suitable selection criteria, we identified 264 candidate ACV variables in the ATLAS variable star catalogue. 62 of these objects were spectroscopically confirmed with spectra from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (all new discoveries except for nine stars) and classified on the MK system. The other 202 stars are here presented as ACV star candidates that require spectroscopic confirmation. The vast majority of our sample of stars are main-sequence objects. Derived masses range from 1.4M(Sun) to 5M(Sun), with half our sample stars being situated in the range from 2 M(Sun) to 2.4 M(Sun), in good agreement with the spectral classifications. Most stars belong to the thin or thick disk; four objects, however, classify as members of the halo population. With a peak magnitude distribution at around 14th magnitude, the here presented stars are situated at the faint end of the known Galactic mCP star population. Our study highlights the need to consider rare variability classes, like ACV variables, in automated classification routines.

Much progress has been made recently in the acceleration of $\sim10^{4}$ K clouds to explain absorption-line measurements of the circumgalactic medium and the atomic phase of galactic winds. However, the origin of the molecular phase in galactic winds has received relatively little theoretical attention. Studies of the survival of atomic clouds suggest efficient radiative cooling may enable the survival of expelled material from galactic disks. Alternatively, atomic and molecular gas may form within the outflow, if dust survives the acceleration process. We explore the survival of molecular, dusty clouds in a hot wind with three-dimensional hydrodynamic simulations in which we include radiative cooling and model dust as tracer particles. We find that molecular gas can be destroyed, survive, or transformed entirely to $\sim 10^4$ K gas. We establish analytic criteria distinguishing these three outcomes which compare characteristic cooling times to the `cloud crushing' time of the system. In contrast to typically studied atomic $\sim10^{4}$ K clouds, molecular clouds are entrained faster than the drag time as a result of efficient mixing. Moreover, we find that while dust can in principle survive embedded in the accelerated clouds, the survival fraction depends critically on the time dust spends in the hot phase and on the effective threshold temperature for destruction. We discuss our results in the context of polluting the circumgalactic medium with dust and metals, as well as understanding observations suggesting rapid acceleration of molecular galactic winds and ram pressure stripped tails of jellyfish galaxies.

The NASA Double Asteroid Redirection Test (DART) mission is a planetary defense-driven test of a kinetic impactor on Dimorphos, the satellite of the binary asteroid 65803 Didymos. DART will intercept Dimorphos at a relative speed of ${\sim}6.5 \text{ km s}^{-1}$, perturbing Dimorphos's orbital velocity and changing the binary orbital period. We present three independent methods (one analytic and two numerical) to investigate the post-impact attitude stability of Dimorphos as a function of its axial ratios, $a/b$ and $b/c$ ($a \ge b \ge c$), and the momentum transfer efficiency $\beta$. The first method uses a novel analytic approach in which we assume a circular orbit and a point-mass primary that identifies four fundamental frequencies of motion corresponding to the secondary's mean motion, libration, precession, and nutation frequencies. At resonance locations among these four frequencies, we find that attitude instabilities are possible. Using two independent numerical codes, we recover many of the resonances predicted by the analytic model and indeed show attitude instability. With one code, we use fast Lyapunov indicators to show that the secondary's attitude can evolve chaotically near the resonance locations. Then, using a high-fidelity numerical model, we find that Dimorphos enters a chaotic tumbling state near the resonance locations and is especially prone to unstable rotation about its long axis, which can be confirmed by ESA's Hera mission arriving at Didymos in late 2026. We also show that a fully coupled treatment of the spin and orbital evolution of both bodies is crucial to accurately model the long-term evolution of the secondary's spin state and libration amplitude. Finally, we discuss the implications of a post-impact tumbling or rolling state, including the possibility of terminating BYORP evolution if Dimorphos is no longer in synchronous rotation.

This study is the first of a series of papers that provide a technique to analyse the mixed-modes frequency spectra and characterise the structure of stars on the subgiant and red-giant branches. We define seismic indicators, relevant of the stellar structure and study their evolution on a grid of models. The proposed method, EGGMiMoSA, relies on the asymptotic description of mixed modes, defines initial guesses for the parameters, and uses a Levenberg-Marquardt technique to adjust the mixed-modes pattern efficiently. We follow the evolution of the mixed-modes parameters along a grid of models from the subgiant phase to the RGB bump and extend past works. We show the impact of the mass and composition on their evolution. The evolution of the period spacing $\Delta\pi_1$, pressure offset $\epsilon_p$, gravity offset $\epsilon_g$, and coupling factor $q$ as a function of $\Delta\nu$ is little affected by the chemical composition and it follows two different regimes depending on the evolutionary stage. On the subgiant branch, the models display a moderate core-envelope density contrast. The evolution of $\Delta \pi_1$, $\epsilon_p$, $\epsilon_g$, and $q$ thus significantly changes with the mass. Also, we demonstrate that, at fixed Z/X and with proper measurements of $\Delta\pi_1$ and $\Delta\nu$, we may unambiguously constrain the mass, radius and age of a subgiant star. Conversely, on the red-giant branch, the core-envelope density contrast becomes very large. Consequently, the evolution of $\epsilon_p$, $\epsilon_g$ and $q$ as a function of $\Delta\nu$ becomes independent of the mass. This is also true for $\Delta \pi_1$ in stars with masses $\lesssim 1.8M_\odot$ because of core electron degeneracy. This degeneracy is lifted for higher masses, again allowing for a precise measurement of the age. Overall, our computations qualitatively agree with past observed and theoretical studies.

The Cosmology Large Angular Scale Surveyor (CLASS) observes the polarized cosmic microwave background (CMB) over the angular scales of 1$^\circ \lesssim \theta \leq$ 90$^\circ$ with the aim of characterizing primordial gravitational waves and cosmic reionization. We report on the on-sky performance of the CLASS Q-band (40 GHz), W-band (90 GHz), and dichroic G-band (150/220 GHz) receivers that have been operational at the CLASS site in the Atacama desert since June 2016, May 2018, and September 2019, respectively. We show that the noise-equivalent power measured by the detectors matches the expected noise model based on on-sky optical loading and lab-measured detector parameters. Using Moon, Venus, and Jupiter observations, we obtain power-to-antenna-temperature calibrations and optical efficiencies for the telescopes. From the CMB survey data, we compute instantaneous array noise-equivalent-temperature sensitivities of 22, 19, 24, and 56 $\mathrm{\mu K}_\mathrm{cmb}\sqrt{\mathrm{s}}$ for the 40, 90, 150, and 220 GHz frequency bands, respectively. These noise temperatures refer to white noise amplitudes, which contribute to sky maps at all angular scales. Future papers will assess additional noise sources impacting larger angular scales.

We present Period-Luminosity Relations (PLRs) for 55 Cepheids in M31 with periods ranging from 4 to 78 days observed with the Hubble Space Telescope (HST) using the same three-band photometric system recently used to calibrate their luminosities. Images were taken with the Wide Field Camera 3 in two optical filters (F555W and F814W) and one near-infrared filter (F160W) using the Drift And SHift (DASH) mode of operation to significantly reduce overheads and observe widely-separated Cepheids in a single orbit. We include additional F160W epochs for each Cepheid from the Panchromatic Hubble Andromeda Treasury (PHAT) and use light curves from the Panoramic Survey Telescope and Rapid Response System of the Andromeda galaxy (PAndromeda) project to determine mean magnitudes. Combined with a 1.28$\%$ absolute calibration of Cepheid PLRs in the Large Magellanic Cloud from Riess_2019 in the same three filters, we find a distance modulus to M31 of $\mu_0$ = 24.407 $\pm$ 0.032, corresponding to 761 $\pm$ 11 kpc and 1.49$\%$ uncertainty including all error sources, the most precise determination of its distance to date. We compare our results to past measurements using Cepheids and the Tip of the Red Giant Branch (TRGB). This study also provides the groundwork for turning M31 into a precision anchor galaxy in the cosmic distance ladder to measure the Hubble constant together with efforts to measure a fully geometric distance to M31.

Developing analysis pipelines based on statistics beyond two-point functions is critical for extracting a maximal amount of cosmological information from current and upcoming weak lensing surveys. In this paper, we study the impact of the intrinsic alignment of galaxies (IA) on three promising probes measured from aperture mass maps -- the lensing peaks, minima and full PDF, in comparison and in combination with the shear two-point correlation functions ($\gamma$-2PCFs). Our two-dimensional IA infusion method converts the light-cone-projected mass sheets into projected tidal tensors, which are then linearly coupled to an intrinsic ellipticity component with a strength controlled by the coupling parameter $A_{\rm IA}$. We validate our method with the $\gamma$-2PCFs statistics, recovering well the analytical calculations from the linear alignment model of \citet{BridleKing} in a full tomographic setting, and for different $A_{\rm IA}$ values. We next use our method to infuse at the galaxy catalogue level a non-linear IA model that includes the density-weighting term introduced in \citet{Blazek2015}, and compute the impact on the three aperture mass map statistics. We find that large \snr peaks are maximally affected, with deviations reaching 30\% (10\%) for a {\it Euclid}-like (KiDS-like) survey. Modelling the signal in a $w$CDM cosmology universe with $N$-body simulations, we forecast the cosmological bias caused by unmodelled IA for 100 deg$^2$ of {\it Euclid}-like data, finding very large offsets in $w_0$ (5-10$\sigma_{\rm stat}$), $\Omega_{\rm m}$ (4-6$\sigma_{\rm stat}$), and $S_8 \equiv \sigma_8\sqrt{\Omega_{\rm m}/0.3}$ ($\sim$3$\sigma_{\rm stat}$). The method presented in this paper offers a compelling avenue to account for IA in beyond-two-point weak lensing statistics, with a flexibility comparable to that of current $\gamma$-2PCFs IA analytical models.

Over the past couple of decades, researchers have predicted more than a dozen super-Chandrasekhar white dwarfs from the detections of over-luminous type Ia supernovae. It turns out that magnetic fields and rotation can explain such massive white dwarfs. If these rotating magnetized white dwarfs follow specific conditions, they can efficiently emit continuous gravitational waves and various futuristic detectors, viz. LISA, BBO, DECIGO, and ALIA can detect such gravitational waves with a significant signal-to-noise ratio. Moreover, we discuss various timescales over which these white dwarfs can emit dipole and quadrupole radiations and show that in the future, the gravitational wave detectors can directly detect the super-Chandrasekhar white dwarfs depending on the magnetic field geometry and its strength.

The spectrum of oscillating compact objects can be considerably altered in alternative theories of gravity. In particular, it may be enriched by modes with no counterpart in general relativity, tied to the dynamics of additional degrees of freedom generically present in these theories. Detection of these modes, e.g. in the gravitational-wave signal from a binary compact object coalescence, could provide a powerful tool to probe the underlying theory of gravity. To access the potential of such a detection, it is crucial to understand the linear and nonlinear spectral features of dynamically formed, oscillating compact objects in alternative theories of gravity. As a step towards that goal, in this work we present a suite of 1+1 numerical relativity simulations of neutron stars in scalar-tensor theories, we carefully analyze the spectrum of stellar pulsations, and we compare results with expectations from linear perturbation theory. This allows us to build intuition for the (3+1) case of binary neutron star mergers. Additionally, the models investigated in this work are representatives of two broad classes, in which the scalar field couples either strongly or weakly with the fluid. The distinct phenomenology of the nonlinear dynamics that we identify for each class of models, may find counterparts also in other alternative theories of gravity.

The axion is a well-motivated candidate for the inflaton, as the radiative corrections that spoil many single-field models are avoided by virtue of its shift symmetry. However, axions generically couple to gauge sectors. As the axion slow-rolls during inflation, this coupling can cause the production of a non-diluting thermal bath, a situation known as "warm inflation." This thermal bath can dramatically alter inflationary dynamics and observable predictions. In this paper, we demonstrate that a thermal bath can form for a wide variety of initial conditions, including starting from zero initial temperature in the universe. Furthermore, we find that axion inflation becomes warm over a large range of couplings, and explicitly map the parameter space for two axion inflation potentials. We show that in large regions of parameter space, axion inflation models once assumed to be safely "cold" are in fact warm, and must be reevaluated in this context.

Sterile neutrinos ($\nu_s$) that mix with active neutrinos ($\nu_a$) are interesting dark matter candidates with a rich cosmological and astrophysical phenomenology. In their simplest incarnation, their production is severely constrained by a combination of structure formation observations and X-ray searches. We show that if active neutrinos couple to an oscillating condensate of a very light $L_{\mu}-L_{\tau}$ gauge field, resonant $\nu_a$-$\nu_s$ oscillations can occur in the early universe, consistent with $\nu_s$ constituting all of the dark matter, while respecting X-ray constraints on $\nu_s\to\nu_a\gamma$ decays. Interesting deviations from standard solar and atmospheric neutrino oscillations can persist to the present.

The axion solution to the strong CP problem is delicately sensitive to Peccei-Quinn breaking contributions that are misaligned with respect to QCD instantons. Heavy QCD axion models are appealing because they avoid this so-called "quality problem". We show that generic realizations of this framework can be probed by the LIGO-Virgo-KAGRA interferometers, through the stochastic gravitational wave (GW) signal sourced by the long-lived axionic string-domain wall network, and by upcoming measurements of the neutron Electric Dipole Moment. Additionally, we provide predictions for searches at future GW observatories, which will further explore the parameter space of heavy QCD axion models.

We present here the model dependent and independent sensitivity studies for NaI detectors designed to test the DAMA result, and compare the predicted limits from SABRE with the present performance of both ANAIS and COSINE. We find that the strongest discovery and exclusion limits are set by a detector with the lowest background (assuming equal run times), and also note that our method correctly computes the present exclusion limits previously published by ANAIS and COSINE. In particular, with a target mass of 50 kg and background rate of 0.36 cpd/kg/keV (after veto), SABRE will be able to exclude the DAMA signal with 3$\sigma$ confidence or `discover' it with 5$\sigma$ confidence within 2 years. This strongly motivates the quest for ever lower backgrounds in NaI detectors.

In the present work, we study slow-roll inflation in scalar-tensor gravity theories in the presence of both the non-minimal coupling between the scalar field and curvature, and the Galileon self-interaction of the scalar field. Furthermore, we give predictions for the duration of reheating as well as for the reheating temperature after inflation. After working out the expressions for the power spectra of scalar and tensor perturbations in the case of a general non-minimal coupling function that depends solely on the scalar field and a general scalar potential, we focus on the special cases of the power-law coupling function and chaotic quadratic inflation. Thus, under the slow-roll approximation we confront the predictions of the model with the current PLANCK constraints on the spectral index $n_s$ and the tensor-to-scalar ratio $r$ using the $n_{s}-r$ plane. We found that the combination of the non-minimal coupling and Galileon self-interaction effects allows us to obtain better results for $r$ than in the case in which each effect is considered separately. Particularly, we obtained that the predictions of the model are in agreement with the current observational bounds on $n_{s}$ and $r$ within the $95 \%$ C.L region and also slightly inside the $68 \%$ C.L region. Also, we investigate the oscillatory regime after the end of inflation by solving the full background equations, and then we determine the upper bound for the Galileon and non-minimal coupling parameters under the condition that the scalar field oscillates coherently during reheating. Finally, after approximating reheating by a constant equation of state, we derive the relations between the reheating duration, the temperature at the end of reheating, its equation of state, and the number of $e$-folds of inflation and then we relate all them with the inflationary observables.

Searches for neutrinoless double beta decay generally require ultimate low backgrounds. Surface $\alpha$ decays on the crystals themselves or nearby materials can deposit a continuum of energies that can be as high as the $Q$-value of the decay and may cover in the region of interest (ROI). The AMoRE-Pilot experiment is an initial phase of the AMoRE search for neutrinoless double beta decay of $^{100}$Mo, with the purpose of investigating the level and sources of backgrounds. To understand those background events, we have studied backgrounds from radioactive contaminations internal to and on the surface of the crystals or nearby materials with Geant4-based Monte Carlo simulations. In this paper, we report the measured $\alpha$ energy spectra fitted with the simulated $\alpha$ energy spectra for the six crystal detectors, where sources of background contributions can be identified at high energy by $\alpha$ peaks for both surface and internal contaminations. We determine the low-energy contributions from internal and surface $\alpha$ contaminations by extrapolating from the $\alpha$ background fitting model.

Loop Quantum Cosmology (LQC) is a theory which renders the Big Bang initial singularity into a quantum bounce, by means of short range repulsive quantum effects at the Planck scale. In this work, we are interested in reproducing the effective Friedmann equation of LQC, by considering a generic $f(R,P,Q)$ theory of gravity, where $R=g^{\mu\nu}R_{\mu\nu}$ is the Ricci scalar, $P=R_{\mu\nu}R^{\mu\nu}$, and $Q=R_{\alpha\beta\mu\nu}R^{\alpha\beta\mu\nu}$ is the Kretschmann scalar. An order reduction technique allows us to work in $f(R,P,Q)$ theories which are perturbatively close to General Relativity, and to deduce a modified Friedmann equation in the reduced theory. Requiring that the modified Friedmann equation mimics the effective Friedmann equation of LQC, we are able to derive several functional forms of $f(R,P,Q)$. We discuss the necessary conditions to obtain viable bouncing cosmologies for the proposed effective actions of $f(R,P,Q)$ theory of gravity.

We study the weak mixing of photons and relativistic axion-like particles (axions) in plasmas with background magnetic fields, ${\bf B}$. We show that, to leading order in the axion-photon coupling, the conversion probability, $P_{\gamma \to a}$, is given by the one-dimensional power spectrum of the magnetic field components perpendicular to the particle trajectory. Equivalently, we express $P_{\gamma \to a}$ as the Fourier transform of the magnetic field autocorrelation function, and establish a dictionary between properties of the real-space magnetic field and the energy-dependent conversion probability. For axions more massive than the plasma frequency, ($m_a>\omega_{\rm pl}$), we use this formalism to analytically solve the problem of perturbative axion-photon mixing in a general magnetic field. In the general case where $m_a/\omega_{\rm pl}$ varies arbitrarily along the trajectory, we show that a naive application of the standard formalism for resonant conversion can give highly inaccurate results, and that a careful calculation generically gives non-resonant contributions at least as large as the resonant contribution. Furthermore, we demonstrate how techniques based on the Fast Fourier Transform provide a new, highly efficient numerical method for calculating axion-photon mixing. We briefly discuss magnetic field modelling in galaxy clusters in the light of our results and argue, in particular, that a recently proposed regular model used for studying axion-photon mixing (specifically applied to the Perseus cluster) is inconsistent with observations. Our formalism suggest new methods to search for imprints of axions, and will be important for spectrographs with percent level sensitivity, which includes existing X-ray observations by Chandra as well as the upcoming Athena mission.

Rates of conversions of molecular internal energy to and from kinetic energy by means of molecular collision allows to compute collisional line shapes and transport properties of gases. Knowledge of ro-vibrational quenching rates is necessary to connect spectral observations to physical properties of warm astrophysical gasses, including exo-atmospheres. For a system of paramount importance in this context, the vibrational bending mode quenching of H2O by H2, we show here that exchange of vibrational to rotational and kinetic energy remains a quantum process, despite the large numbers of quantum levels involved and the large vibrational energy transfer. The excitation of the quantized rotor of the projectile is by far the most effective ro-vibrational quenching path of water. To do so, we use a fully quantum first principle computation, potential and dynamics, converging it at all stages, in a full coupled channel formalisms. We present here rates for the quenching of the first bendingmode of ortho-H2O by ortho H2, up to 500K, in a fully converged coupled channels formalism.