Papers for Friday, Jun 24 2022

We study the diffuse background free-free emission induced in dark matter halos. Since dark matter halos host ionized thermal plasma, they are an important source of the cosmological free-free emission. We evaluate the global background intensity and anisotropy of this free-free emission. We show that the dominant contribution comes from dark matter halos with a mass close to the Jeans mass, $M_{\mathrm{halo}}\sim 10^{10} M_\odot$, around the redshift $z \sim 1$. Therefore, the intensity of the free-free emission is sensitive to the small-scale curvature perturbations that form such small-mass dark matter halos. Considering the blue-tilted curvature perturbations, we find that the free-free emission signal is modified by $\sim 25 \%$ even in the parameter set of the spectral index and the running, which is consistent with the recent Planck result. However, our obtained intensity of the global and anisotropic free-free emission is smaller than the ten percent level of the observed free-free emission, which is dominated by the Galactic origin. Therefore, the measurement of the cosmological free-free signals has the potential to provide more stringent constraints on the abundance of small-mass dark matter halos and the curvature perturbations including the spectral index and the running, while carefully removing the Galactic free-free emission is required through the multifrequency radio observation or the cross-correlation study with the galaxy surveys or 21-cm intensity map.

Exoplanet atmospheres are inherently three-dimensional systems in which thermal/chemical variation and winds can strongly influence spectra. Recently, the ultra-hot Jupiter WASP-76 b has shown evidence for condensation and asymmetric Fe absorption with time. However, it is currently unclear whether these asymmetries are driven by chemical or thermal differences between the two limbs, as precise constraints on variation in these have remained elusive due to the challenges of modelling these dynamics in a Bayesian framework. To address this we develop a new model, HyDRA-2D, capable of simultaneously retrieving morning and evening terminators with day-night winds. We explore variations in Fe, temperature profile, winds and opacity deck with limb and orbital phase using VLT/ESPRESSO observations of WASP-76 b. We find Fe is more prominent on the evening for the last quarter of the transit, with $\log(X_\mathrm{Fe}) = {-4.03}^{+0.28}_{-0.31}$, but the morning shows a lower abundance with a wider uncertainty, $\log(X_\mathrm{Fe}) = {-4.59}^{+0.85}_{-1.0}$, driven by degeneracy with the opacity deck and the stronger evening signal. We constrain 0.1 mbar temperatures ranging from $2950^{+111}_{-156}$ K to $2615^{+266}_{-275}$ K, with a trend of higher temperatures for the more irradiated atmospheric regions. We also constrain a day-night wind speed of $9.8^{+1.2}_{-1.1}$ km/s for the last quarter, higher than $5.9^{+1.5}_{-1.1}$ km/s for the first, in line with general circulation models. We find our new spatially- and phase-resolved treatment is statistically favoured by 4.9$\sigma$ over traditional 1D-retrievals, and thus demonstrate the power of such modelling for robust constraints with current and future facilities.

Ultra-light dark matter (ULDM) refers to a class of theories, including ultra-light axions, in which particles with mass $m_{\psi} < 10^{-20}\, \rm{eV}$ comprise a significant fraction of the dark matter. A galactic scale de Broglie wavelength distinguishes these theories from cold dark matter (CDM), suppressing the overall abundance of structure on sub-galactic scales, and producing wave-like interference phenomena in the density profiles of halos. With the aim of constraining the particle mass, we analyze the flux ratios in a sample of eleven quadruple-image strong gravitational lenses. We account for the suppression of the halo mass function and concentration-mass relation predicted by ULDM theories, and the wave-like fluctuations in the host halo density profile, calibrating the model for the wave interference against numerical simulations of galactic-scale halos. We show that the granular structure of halo density profiles, in particular, the amplitude of the fluctuations, significantly impacts image flux ratios, and therefore inferences on the particle mass derived from these data. We infer relative likelihoods of CDM to ULDM of 8:1, 7:1, 6:1, and 4:1 for particle masses $\log_{10}(m_\psi/\rm{eV})\in[-22.5,-22.25], [-22.25,-22.0],[-22.0,-21.75], [-21.75,-21.5]$, respectively. Repeating the analysis and omitting fluctuations associated with the wave interference effects, we obtain relative likelihoods of CDM to ULDM with a particle mass in the same ranges of 98:1, 48:1, 26:1 and 18:1, highlighting the significant perturbation to image flux ratios associated with the fluctuations. Nevertheless, our results disfavor the lightest particle masses with $m_{\psi} < 10^{-21.5}\,\rm{eV}$, adding to mounting pressure on ultra-light axions as a viable dark matter candidate.

Since its launch in 2008, the Fermi Large Area Telescope (LAT) allowed us to peek into the extremely energetic side of the Universe with unprecedented sensitivity and resolution. The tools available for analyzing Fermi-LAT data are the Fermitools and Fermipy, both of which can be scripted in Python and run via command lines in a terminal or in web-based interactive computing platforms. In this work, we are providing the community with easyFermi, an open-source user-friendly graphical interface for performing basic to intermediate analyses of Fermi-LAT data in the framework of Fermipy. With easyFermi, the user can quickly measure the $\gamma$-ray flux and photon index, build spectral energy distributions, light curves, test statistic maps, test for extended emission and even relocalize the coordinates of $\gamma$-ray sources. The tutorials for easyFermi are available on YouTube and GitHub, allowing the user to learn how to use Fermi-LAT data in about 10 min.

The effect of stellar multiplicity on the formation and evolution of planetary systems is complex. At a demographic level, campaigns with both high-resolution imaging and radial velocity observations indicate that planet formation is strongly disrupted by close binaries, while being relatively unaffected by wide companions. However, the magnitude and distance-limited nature of those tools mean that large ranges of mass ratios and separations remain largely unexplored. The Early Data Release 3 (EDR3) from the Gaia Mission includes radial velocity measurements of over 6.5 million targets, which we employ to explore the effect of binary companions within a statistical framework called paired. These companions present as a source of excess radial velocity noise in the Gaia catalog, when compared to the typical noise for stars of similar spectral type and magnitude. Within this framework, we examine the evidence for stellar multiplicity among the stars surveyed by NASA's Kepler and TESS missions. We use radial velocity errors published in Gaia EDR3 to estimate the probability of an unresolved stellar companion for a large subset of the Kepler and TESS Input Catalog stars, where possible benchmarking our inferred radial velocity semi-amplitudes against the those from ground-based radial velocity surveys. We determine that we are typically sensitive out to several AU and mass ratios $>0.1$, dependent upon the stellar magnitude. We aim for paired to be a useful community tool for the exploration of the effects of binarity on planets at a population level, and for efficient identification of false-positive transit candidates.

The Wess Zumino Dark Radiation (WZDR) model first proposed in arXiv:2111.00014 shows great promise as a well-motivated simple explanation of the Hubble tension between local and CMB-based measurements. In this work we investigate the assumptions made in the original proposal and confront the model with additional independent data sets. We show that the original assumptions can have an impact on the overall results but are usually well motivated. We further demonstrate that the preference for negative $\Omega_k$ remains at a similar level as for the $\Lambda$CDM model, while the $A_L$ tension is slightly reduced. Furthermore, the tension between Planck data for $\ell < 800$ and $\ell \geq 800$ is significantly reduced for the WZDR model. The independent data sets show slightly more permissive bounds on the Hubble parameter, allowing the tension to be further reduced to $2.1 \sigma$ (CMB-independent) or $1.9\sigma$ (ACT+WMAP). However, no combination shows a large preference for the presence of WZDR. We also investigate whether additional dark radiation -- dark matter interactions can help in easing the $S_8$ tension as well. We find that the CMB data are too restrictive on this additional component as to allow a significant decrease in the clustering.

ASASSN-14ko is a nuclear transient at the center of the AGN ESO 253-G003 that undergoes periodic flares. Optical flares were first observed in 2014 by the All-Sky Automated Survey for Supernovae (ASAS-SN) and their peak times are well-modeled with a period of $115.2^{+1.3}_{-1.2}$ days and period derivative of $-0.0026 \pm 0.0006$. Here we present ASAS-SN, Chandra, HST/STIS, NICER, Swift, and TESS data for the flares that occurred in December 2020, April 2021, July 2021, and November 2021. The HST/STIS UV spectra evolve from blue shifted broad absorption features to red shifted broad emission features over $\sim$10 days. The Swift UV/optical light curves peaked as predicted by the timing model, but the peak UV luminosities varied between flares and the UV flux in July 2021 was roughly half the brightness of all other peaks. The X-ray luminosities consistently decreased and the spectra became harder during the UV/optical rise but apparently without changes in absorption. Finally, two high-cadence TESS light curves from December 2020 and November 2018 showed that the slopes during the rising and declining phases changed over time, which indicates some stochasticity in the flare's driving mechanism. ASASSN-14ko remains observationally consistent with a repeating partial tidal disruption event, but, these rich multi-wavelength data are in need of a detailed theoretical model.

Modeling of strong gravitational lenses is a necessity for further applications in astrophysics and cosmology. Especially with the large number of detections in current and upcoming surveys such as the Rubin Legacy Survey of Space and Time (LSST), it is timely to investigate in automated and fast analysis techniques beyond the traditional and time consuming Markov chain Monte Carlo sampling methods. Building upon our convolutional neural network (CNN) presented in Schuldt et al. (2021b), we present here another CNN, specifically a residual neural network (ResNet), that predicts the five mass parameters of a Singular Isothermal Ellipsoid (SIE) profile (lens center $x$ and $y$, ellipticity $e_x$ and $e_y$, Einstein radius $\theta_E$) and the external shear ($\gamma_{ext,1}$, $\gamma_{ext,2}$) from ground-based imaging data. In contrast to our CNN, this ResNet further predicts a 1$\sigma$ uncertainty for each parameter. To train our network, we use our improved pipeline from Schuldt et al. (2021b) to simulate lens images using real images of galaxies from the Hyper Suprime-Cam Survey (HSC) and from the Hubble Ultra Deep Field as lens galaxies and background sources, respectively. We find overall very good recoveries for the SIE parameters, while differences remain in predicting the external shear. From our tests, most likely the low image resolution is the limiting factor for predicting the external shear. Given the run time of milli-seconds per system, our network is perfectly suited to predict the next appearing image and time delays of lensed transients in time. Therefore, we also present the performance of the network on these quantities in comparison to our simulations. Our ResNet is able to predict the SIE and shear parameter values in fractions of a second on a single CPU such that we are able to process efficiently the huge amount of expected galaxy-scale lenses in the near future.

Spectroscopic data are necessary to break degeneracies in asteroseismic modelling of the interior structure in high- and intermediate-mass stars. We derive precise photospheric stellar parameters for a sample of 166 B-type stars with TESS light curves, suitable for detailed asteroseismic studies, through a homogeneous spectroscopic analysis. The variability types of these stars are classified based on all currently available TESS sectors. We obtained high-resolution spectra for all 166 targets with the FEROS spectrograph in the context of a large program. The Least-Squares Deconvolution method is employed to investigate spectral line profile variability and to detect binary systems. We identify 26 spectroscopic double-lined binaries; the remainder of the sample are 42 supergiants in the LMC galaxy and 98 Galactic stars. The spectra of the Galactic stars are analysed with the zeta-Payne, a machine learning-based spectrum analysis algorithm. We determine the five main surface parameters with average formal precisions of 70 K (Teff), 0.03 dex (logg), 0.07 dex ([M/H]), 8 km/s (vsini), and 0.7 km/s (vmicro). The average internal uncertainties we find for FEROS spectra with our spectrum analysis method are 430 K (Teff), 0.12 dex (logg), 0.13 dex ([M/H]), 12 km/s (vsini), and 2 km/s (vmicro). We find spectroscopic evidence that eight of the 98 Galactic targets are fast rotating g-mode pulsators occurring in between the slowly pulsating B (SPB) stars and delta Scuti instability strips. The g-mode frequencies of these pulsators are shifted to relatively high frequency values due to their rotation. Their apparently too low Teff relative to the SPB instability region can in most cases be explained by the gravity darkening effect. We also discover 13 new HgMn stars of which only one is found in a spectroscopic binary, resulting in a biased and therefore unreliable low binary rate of only 8%.

Astrophysical observations of neutron stars have been widely used to infer the properties of the nuclear matter equation of state. Beside being a source of information on average properties of dense matter, however, the data provided by electromagnetic and gravitational wave (GW) facilities are reaching the accuracy needed to constrain, for the first time, nuclear dynamics in dense matter. In this work we assess the sensitivity of current and future neutron star observations to directly infer the strength of repulsive three-nucleon forces, which are key to determine the stiffness of the equation of state. Using a Bayesian approach we focus on the constraints that can be derived on three-body interactions from binary neutron star mergers observed by second and third-generation of gravitational wave interferometers. We consider both single and multiple observations. For current detectors at design sensitivity the analysis suggests that only low mass systems, with large signal-to-noise ratios (SNR), allow to reliably constrain the three-body forces. However, our results show that a single observation with a third-generation interferometer, such as the Einstein Telescope or Cosmic Explorer, will constrain the strength of the repulsive three-body potential with exquisite accuracy, turning third-generation GW detectors into new laboratories to study the nucleon dynamics.

Silicon Pore Optics (SPO) uses commercially available monocrystalline double-sided super-polished silicon wafers as a basis to produce mirrors that form lightweight high-resolution X-ray optics. The technology has been invented by cosine Measurement Systems and the European Space Agency (ESA) and developed together with scientific and industrial partners to mass production levels. It leverages techniques and processes developed over decades by the semiconductor industry to handle, process, and clean silicon wafers and plates. SPO is an enabling technology for large space-borne X-ray telescopes such as Athena and ARCUS, operating in the 0.2 to 12 keV band, with angular resolution aiming for 5 arc seconds. SPO has also shown to be a versatile technology that can be further developed for gamma-ray optics, medical applications and for material research.

We introduce the TangoSIDM project, a suite of cosmological simulations of structure formation in a $\Lambda$-Self-Interacting Dark Matter (SIDM) universe. TangoSIDM explores the impact of large dark matter (DM) scattering cross sections over dwarf galaxy scales. Motivated by DM interactions that follow a Yukawa potential, the cross section per unit mass, $\sigma/m_{\chi}$, assumes a velocity dependent form that avoids violations of current constraints on large scales. We demonstrate that our implementation accurately models not only core formation in haloes, but also gravothermal core collapse. For central haloes in cosmological volumes, frequent DM particle collisions isotropise the particles orbit, making them largely spherical. We show that the velocity-dependent $\sigma/m_{\chi}$ models produce a large diversity in the circular velocities of satellites haloes, with the spread in velocities increasing as the cross sections reach 20, 60 and 100 cm$^2$/g in $10^9~\rm{M}_{\odot}$ haloes. The large variation in the haloes internal structure is driven by DM particles interactions, causing in some haloes the formation of extended cores, whereas in others gravothermal core collapse. We conclude that the SIDM models from the Tango project offer a promising explanation for the diversity in the density and velocity profiles of observed dwarf galaxies.

The 1.33 mm survey of protoplanetary discs in the Taurus molecular cloud found annular gaps and rings to be common in extended sources (>~55 au), when their 1D visibility distributions were fit parametrically. We first demonstrate the advantages and limitations of nonparametric visibility fits for data at the survey's 0.12" resolution. Then we use the nonparametric model in Frankenstein ('frank') to identify new substructure in three compact and seven extended sources. Among the new features we identify three trends: a higher occurrence rate of substructure in the survey's compact discs than previously seen, underresolved (potentially azimuthally asymmetric) substructure in the innermost disc of extended sources, and a 'shoulder' on the trailing edge of a ring in discs with strong depletion at small radii. Noting the shoulder morphology is present in multiple discs observed at higher resolution, we postulate it is tracing a common physical mechanism. We further demonstrate how a super-resolution frank brightness profile is useful in motivating an accurate parametric model, using the highly structured source DL Tau in which frank finds two new rings. Finally we show that sparse (u, v) plane sampling may be masking the presence of substructure in several additional compact survey sources.

High-resolution cosmological N-body simulations are excellent tools for modelling the formation and clustering of dark matter haloes. These simulations suggest complex physical theories of halo formation governed by a set of effective physical parameters. Our goal is to extract these parameters and their uncertainties in a Bayesian context. We make a step towards automatising this process by directly comparing dark matter density projection maps extracted from cosmological simulations, with density projections generated from an analytical halo model. The model is based on a toy implementation of two body correlation functions. To accomplish this we use marginal neural ratio estimation, an algorithm for simulation-based inference that allows marginal posteriors to be estimated by approximating marginal likelihood-to-evidence ratios with a neural network. In this case, we train a neural network with mock images to identify the correct values of the physical parameters that produced a given image. Using the trained neural network on cosmological N-body simulation images we are able to reconstruct the halo mass function, to generate mock images similar to the N-body simulation images and to identify the lowest mass of the haloes of those images, provided that they have the same clustering with our training data. Our results indicate that this is a promising approach in the path towards developing cosmological simulations assisted by neural networks.

The accuracy in determining the spatial-kinematical parameters of open clusters makes them ideal tracers of the Galactic structure. Young open clusters (YOCs) are the main representative of the clustered star formation mode, which identifies how most of the stars in the Galaxy form. We apply the Kriging technique to a sample of Gaia YOCs within a 3.5 kpc radius around the Sun and log(age) $\leq$ 7.5, age in years, to obtain the $Z(X,Y)$ and $V_Z(X,Y)$ maps. The previous work by Alfaro et al. (1991) showed that Kriging can provide reliable results even with small data samples ($N \sim 100$). We approach the 3D spatial and vertical velocity field structure of the Galactic disk defined by YOCs and analyze the hierarchy of the stellar cluster formation, which shows a rich hierarchical structure, displaying complexes embedded within each other. We discuss the fundamental characteristics of the methodology used to perform the mapping and point out the main results obtained in phenomenological terms. Both the 3D spatial distribution and the vertical velocity field reveal a complex disk structure with a high degree of substructures. Their analysis provides clues about the main physical mechanisms that shape the phase space of the clustered star formation in this Galactic area. Warp, corrugations, and high local deviations in $Z$ and $V_Z$, appear intimately connected in a single but intricate scenario.

Understanding the radii of massive stars throughout their evolution is important to answering numerous questions about stellar physics, from binary interactions on the main sequence to the pre-supernova radii. One important factor determining a star's radius is the fraction of its mass in elements heavier than Helium (metallicity, $Z$). However, the metallicity enters stellar evolution through several distinct microphysical processes, and which dominates can change throughout stellar evolution and with the overall magnitude of $Z$. We perform a series of numerical experiments with 15M$_{\odot}$ MESA models computed doubling separately the metallicity entering the radiative opacity, the equation of state, and the nuclear reaction network to isolate the impact of each on stellar radii. We explore separately models centered around two metallicity values: one near solar $Z=0.02$ and another sub-solar $Z\sim10^{-3}$, and consider several key epochs from the end of the main sequence to core carbon depletion. We find that the metallicity entering the opacity dominates at most epochs for the solar metallicity models, contributing to on average $\sim$60 - 90% of the total change in stellar radius. Nuclear reactions have a larger impact ($\sim$50 - 70%) during most epochs in the subsolar $Z$ models. The methodology introduced here can be employed more generally to propagate known microphysics errors into uncertainties on macrophysical observables including stellar radii.

Near-Earth Asteroids (NEAs) with small perihelion distances reach sub-solar temperatures of > 1000 K. They are hypothesized to undergo "super-catastrophic" disruption, potentially caused by near-Sun processes such as thermal cracking, spin-up, meteoroid impacts, and subsurface volatile release; all of which are likely to cause surface alteration, which may change the spectral slope of the surface. We attempted to observe 35 of the 53 known near-Sun asteroids with q < 0.15 au from January 2017 to March 2020 to search for trends related to near-Sun processes. We report the optical colors and spectral slopes of 22 objects that we successfully observed and the measured rotation periods for three objects. We find the distribution of colors to be overall bluer than the color distribution of NEAs, though there is large overlap. We attribute large scatter to unknown dynamical histories and compositions for individual objects, as well as competing surface altering processes. We also investigated potential correlations between colors and other properties (e.g., perihelion distance, Tisserand parameter, rotation period), and searched for evidence of activity. Finally, we have compiled all known physical and dynamical properties of these objects, including probabilistic source regions and dwell times with q < 0.15 au.

During the last few decades, the most widely favored models for coronal heating have involved the in situ dissipation of energy, with footpoint shuffling giving rise to multiple current sheets (the "nanoflare" model) or to Alfv{\'e}n waves that leak into the corona and undergo dissipative interactions (the wave heating scenario). As has been recognized earlier, observations suggest instead that the energy deposition is concentrated at very low heights, with the coronal loops being filled with hot, dense material from below, which accounts for their overdensities and flat temperature profiles. While an obvious mechanism for footpoint heating would be reconnection with small-scale fields, this possibility seems to have been widely ignored because magnetograms show almost no minority-polarity flux inside active region (AR) plages. Here, we present further examples to support our earlier conclusions (1) that magnetograms greatly underrepresent the amount of minority-polarity flux inside plages and "unipolar" network, and (2) that small loops are a major constituent of \ion{Fe}{9} 17.1 nm moss. On the assumption that the emergence or churning rate of small-scale flux is the same inside plages as in mixed-polarity regions of the quiet Sun, we estimate the energy flux density associated with reconnection with the plage fields to be on the order of 10$^7$ erg cm$^{-2}$ s$^{-1}$, sufficient to heat the AR corona.

A correlation between the intrinsic energy and the burst duration of non-repeating fast radio bursts (FRBs) has been reported. If it exists, the correlation can be used to estimate intrinsic energy from the duration, and thus can provide us with a new distance measure for cosmology. However, the correlation suffered from small number statistics (68 FRBs) and was not free from contamination by latent repeating populations, which might not have such a correlation. How to separate/exclude the repeating bursts from the mixture of all different types of FRBs is essential to see this property. Using a much larger sample from the new FRB catalogue (containing 536 FRBs) recently released by the CHIME/FRB project, combined with a new classification method developed based on unsupervised machine learning, we carried out further scrutiny of the relation. We found that there is a weak correlation between the intrinsic energy and duration for non-repeating FRBs at z < 0.3 with Kendall's tau correlation coefficient of 0.239 and significance of 0.001 (statistically significant), whose slope looks similar to that of gamma-ray bursts. This correlation becomes weaker and insignificant at higher redshifts (z > 0.3), possibly due to the lack of the faint FRBs at high-z and/or the redshift evolution of the correlation. The scattering time in the CHIME/FRB catalogue shows an intriguing trend: it varies along the line obtained from linear fit on the energy versus duration plane between these two parameters. A possible cosmological application of the relation must wait for faint FRBs at high-z.

Galactic massive lenses with large Einstein Radius should cause a measurable astrometric microlensing effect, i.e. the light centroid shift due to motion of two images. Such shift in the position of a background star due to microlensing was not included in the $Gaia$ astrometric model, therefore significant deviation should cause $Gaia$ astrometric parameters to be determined incorrectly. Here we studied one of the photometric microlensing events reported in the $Gaia$ DR3, GaiaDR3-ULENS-001, for which $Gaia$ poor goodness of fit and erroneous parallax could indicate presence of the astrometric microlensing signal. Based on the photometric microlensing model, we simulated $Gaia$ astrometric time-series with astrometric microlensing effect added. We found that including microlensing with the angular Einstein Radius of $\theta_{\rm E}$ from 2.23-2.81 mas reproduces well the astrometric quantities reported by $Gaia$. We estimate the mass of the lens to within 0.57-1.23 $M_\odot$ and its distance within 0.60-1.04 kpc, proposing the lens could be a nearby isolated white dwarf.

Numerical simulations of dwarf galaxies have so far failed to reproduce the observed metallicity-luminosity relation, down to the ultra-faint dwarfs (UFDs). We address this issue exploring how the first generations of metal-free stars (Pop III) could help increase the mean metallicity of those faint galaxies. We run zoom-in chemo-dynamical simulations of nineteen halos extracted from a cosmological box and follow down to redshift 0. Models are validated not only on the basis of galaxy global properties, but also the stellar abundance ratios. We identify the necessary conditions for the formation of first stars in mini-halos and derive constraints on the metal ejection schemes. The impact of Pop III stars on the final metallicity of UFDs is evaluated by considering different IMFs, the influence of pair-instability supernovae (PISNe) and their energetic feedback, as well as the metallicity threshold marks the transition from first stars to the formation of low-mass long-lived stars. The inclusion of Pop III stars does increase the global metallicity of UFDs, though insufficient to resolve the tension with observations. PISNe with progenitor masses above 140Msun do allow to further increase the metal content of UFDs. However, as PISNe are rare and sometimes absent in the faintest UFDs, they have a limited impact on the global faint end of the metallicity-luminosity relation. Despite a limited number of spectroscopically confirmed members in UFDs, that makes the metallicity distribution of some UFDs uncertain, our analysis reveals this is the metal-rich tail that is missing in the models. The remaining challenges are thus both observational and numerical: i) to extend high resolution spectroscopy data samples and confirm the mean metallicity of the faintest UFDs, ii) to explain the presence of chemically enriched stars in galaxies with very short star formation histories.

Meteor showers and their outbursts are the dominant source of meteoroid impact risk to spacecraft on short time scales. Meteor shower prediction models depend on historical observations to produce accurate forecasts. However, the current lack of quality and persistent world-wide monitoring at optical meteoroid sizes has left some recent major outbursts poorly observed. A novel method of computing meteor shower flux is developed and applied to Global Meteor Network data. The method is verified against previously published observations of the Perseids and the Geminids. The complete mathematical and algorithmic details of computing meteor shower fluxes from video observations are described. As an example application of our approach, the flux measurements of the 2021 Perseid outburst, the 2020-2022 Quadrantids, and 2020-2021 Geminids are presented. The flux of the 2021 Perseids reached similar levels to the 1991-1994 and 2016 outbursts (ZHR $\sim$ 280). The flux of the Quadrantids shows high year-to-year variability in the core of the stream while the longer lasting background activity is less variable, consistent with an age difference between the two components. The Geminids show a double peak in flux near the time of peak.

The habitability of exoplanets can be strongly influenced by the presence of an exomoon, and in some cases the exomoon itself could be a possible place for life to develop. For moons outside of the habitable zone, significant tidal heating may raise their surface temperature enough to be considered habitable. Tidal heating of a moon depends on numerous factors such as eccentricity, semimajor axis, size of parent planet, and presence of additional moons. In this work, we explore the degree of tidal heating possible for multi-moon systems in resonance using a combination of semi-analytic and numerical models. This demonstrates that even for a moon with zero initial eccentricity, when it moves into resonance with an outer moon, it can generate significant eccentricity and associated tidal heating. Depending on the mass ratio of the two moons, this resonance can either be short-lived ($\leq200$ Myr) or continue to be driven by the tidal migration of the moons. This tidal heating can also assist in making the exomoons easier to discover, and we explore two scenarios: secondary eclipses and outgassing of volcanic species. We then consider hypothetical moons orbiting known planetary systems to identify which will be beast suited for finding exomoons with these methods. We conclude with a discussion of current and future instrumentation and missions to better understand how practical it will be to make exomoon discoveries in these ways.

Compact planetary systems with more than two planets can undergo orbital crossings from planet-planet perturbations. The time which the system remains stable without orbital crossings has an exponential dependence on the initial orbital separations in units of mutual Hill radii. However when a multiplanet system has period ratios near mean-motion resonances, its stability time differs from the time determined by planet separation. This difference can be up to an order of magnitude when systems are set up with chains of equal period ratios. We use numerical simulations to describe the stability time relationship in systems with equal separations but non-equal masses which breaks the chains of equal period ratios. We find a deviation of 30 per cent in the masses of the planets creates a large enough deviation in the period ratios where the average stability time of a given spacing can be predicted by the stability time relationship. However, the distribution of stability time at a given spacing is much wider than in equal-mass systems. We find the stability time distribution is heteroscedastic with spacing -- the deviation in stability time for a given spacing increases with said spacing.

Laser guide star (LGS) wave-front sensing (LGSWFS) is a key element of tomographic adaptive optics system. However, when considering Extremely Large Telescope (ELT) scales, the LGS spot elongation becomes so large that it challenges the standard recipes to design LGSWFS. For classical Shack-Hartmann wave-front sensor (SHWFS), which is the current baseline for all ELT LGS-assisted instruments, a trade-off between the pupil spatial sampling [number of sub-apertures (SAs)], the SA field-of-view (FoV) and the pixel sampling within each SA is required. For ELT scales, this trade-off is also driven by strong technical constraints, especially concerning the available detectors and in particular their number of pixels. For SHWFS, a larger field of view per SA allows mitigating the LGS spot truncation, which represents a severe loss of performance due to measurement biases. For a given number of available detectors pixels, the SA FoV is competing with the proper sampling of the LGS spots, and/or the total number of SAs. We proposed a sensitivity analysis, and we explore how these parameters impacts the final performance. In particular, we introduce the concept of super resolution, which allows one to reduce the pupil sampling per WFS and opens an opportunity to propose potential LGSWFS designs providing the best performance for ELT scales.

We investigate the metal species associated with the Ly$\alpha$ forest in the eBOSS quasar spectra. Metal absorption lines are revealed in the stacked spectra from cross-correlating the selected Ly$\alpha$ absorbers in the forest and the flux fluctuation field. Up to 13 metal species are identified associated with relatively strong Ly$\alpha$ absorbers (those with flux fluctuation $-1.0<\delta_{\rm Ly\alpha}<-0.6$ and with neutral hydrogen column density of ~ $10^{15-16}$ $\rm cm^{-2}$) over absorber redshift range of $2<z_{\rm abs}<4$. The column densities of these species decrease toward higher redshift and for weaker Ly$\alpha$ absorbers. From modelling the column densities of various species, we find that the column density pattern suggests contributions from multiple gas components both in the circumgalactic medium (CGM) and in the intergalactic medium (IGM). While the low-ionization species (e.g., C II, Si II, and Mg II) can be explained by high-density, cool gas ($T \sim 10^4$ K) from the CGM, the high-ionization species may reside in low-density or high-temperature gas in the IGM. The measurements provide inputs to model metal contamination in the Ly$\alpha$ forest baryon acoustic oscillations measurement. Comparison with metal absorptions in high-resolution quasar spectra and with hydrodynamic galaxy formation simulations can further elucidate the physical conditions of these Ly$\alpha$ absorbers.

We measure the spatially resolved recent star formation history (SFH) of M33 using optical images taken with the Hubble Space Telescope as part of the Panchromatic Hubble Andromeda Treasury: Triangulum Extended Region (PHATTER) survey. The area covered by the observations used in this analysis covers a de-projected area of $\sim$38 kpc$^{2}$ and extends to $\sim$3.5 and $\sim$2 kpc from the center of M33 along the major and semi-major axes, respectively. We divide the PHATTER optical survey into 2005 regions that measure 24 arcsec, $\sim$100 pc, on a side and fit color magnitude diagrams for each region individually to measure the spatially resolved SFH of M33 within the PHATTER footprint. There are significant fluctuations in the SFH on small spatial scales and also galaxy-wide scales that we measure back to about 630 Myr ago. We observe a more flocculent spiral structure in stellar populations younger than about 80 Myr, while the structure of the older stellar populations is dominated by two spiral arms. We also observe a bar in the center of M33, which dominates at ages older than about 80 Myr. Finally, we find that the mean star formation rate (SFR) over the last 100 Myr within the PHATTER footprint is 0.32$\pm$0.02 M$_{\odot}$ yr$^{-1}$. We measure a current SFR (over the last 10 Myr) of 0.20$\pm$0.03 M$_{\odot}$ yr$^{-1}$. This SFR is slightly higher than previous measurements from broadband estimates, when scaled to account for the fraction of the D25 area covered by the PHATTER survey footprint.

We complete the analysis of all 2018 sub-prime-field microlensing planets identified by the KMTNet AnomalyFinder. Among the 9 previously unpublished events with clear planetary solutions, 6 are clearly planetary (KMT-2018-BLG-0030, KMT-2018-BLG-0087, KMT-2018-BLG-0247, OGLE-2018-BLG-0298, KMT-2018-BLG-2602, and OGLE-2018-BLG-1119), while the remaining 3 are ambiguous in nature. In addition, there are 8 previously published sub-prime field planets that were selected by the AnomalyFinder algorithm. Together with a companion paper (Gould et al. 2022) on 2018 prime-field planets, this work lays the basis for the first statistical analysis of the planet mass-ratio function based on planets identified in KMTNet data. As expected (Zhu et al. 2014), half (17/33) of the 2018 planets likely to enter the mass-ratio analysis have non-caustic-crossing anomalies. However, only 1 of the 5 non-caustic anomalies with planet-host mass ratio $q<10^{-3}$ was discovered by eye (compared to 7 of the 12 with $q>10^{-3}$), showing the importance of the semi-automated AnomalyFinder search.

The currently available, detailed properties (e.g., isotopic ratios) of solar system planets may provide guides for constructing better approaches of exoplanet characterization. With this motivation, we explore how the measured values of the deuterium-to-hydrogen (D/H) ratio of Uranus and Neptune can constrain their formation mechanisms. Under the assumption of in-situ formation, we investigate three solid accretion modes; a dominant accretion mode switches from pebble accretion to drag-enhanced three-body accretion and to canonical planetesimal accretion, as the solid radius increases. We consider a wide radius range of solids that are accreted onto (proto)Neptune-mass planets and compute the resulting accretion rates as a function of both the solid size and the solid surface density. We find that for small-sized solids, the rate becomes high enough to halt concurrent gas accretion, if all the solids have the same size. For large-sized solids, the solid surface density needs to be enhanced to accrete enough amounts of solids within the gas disk lifetime. We apply these accretion modes to the formation of Uranus and Neptune and show that if the minimum-mass solar nebula model is adopted, solids with radius of $\sim 1$ m to $\sim 10$ km should have contributed mainly to their deuterium enrichment; a tighter constraint can be derived if the full solid size distribution is determined. This work therefore demonstrates that the D/H ratio can be used as a tracer of solid accretion onto Neptune-mass planets. Similar efforts can be made for other atomic elements that serve as metallicity indicators.

Measurements from galaxies spanning a broad range of morphology reveal a linear scaling of enclosed dark to luminous mass that is not anticipated by standard galaxy formation cosmology. The linear scaling is found to extend from the inner galactic region to the outermost data point. Uncertainties in the linear relation are narrow, with rms = 0.31 and {\sigma} = 0.31. It is unclear what would produce this linearity of enclosed dark to luminous mass. Baryonic processes are challenged to account for the linear scaling, and no dark matter candidate possesses a property that would result in a linear relation. The linear scaling may indicate new dark matter candidates, or an astrophysical process beyond the standard galaxy formation theory.

Long-duration GRB 211211A that lacks a supernova emission even down to very stringent limits at such a low redshift $z=0.076$ and associate with kilonova emission, suggest that its physical origin is from binary compact stars merger. By re-analyzing its data observed with the GBM on board Fermi mission, we find that both time-integrated and time-resolved spectra can be fitted well by using Band plus blackbody (Band+BB) model in the prompt emission. The bulk Lorentz factors ($\Gamma_{\rm ph}$) of the outflow can be inferred by invoking the observed thermal emission at photosphere radius within a pure fireball model, and find out that the temporal evolution of $\Gamma_{\rm ph}$ seems to be tracking with the light curve. The derived values of $\Gamma_{\rm ph}$ are also consistent with the $\Gamma_{\rm ph}$ - $L_{\gamma, iso}$/$E_{\gamma, iso}$ correlations that had been found in other bursts. Moreover, we also calculate the magnetization factor $\sigma_{0}$ in the central engine and $\sigma_{\rm ph}$ at the photosphere radius within the framework of hybrid jet model, and find that the values of both $1+\sigma_{\rm 0}$ and $1+\sigma_{\rm ph}$ are larger than 1 for different time slices. It suggests that at least the Poynting-flux component is indeed existent in the outflow. If this is the case, one possible physical interpretation of thermal and non-thermal emissions in GRB 211211A is from the contributions of both $\nu\bar{\nu}$ annihilation and the Blandford-Znajek mechanisms in the relativistic jet when a stellar mass black hole reside in the central engine.

Flat $\Lambda$CDM cosmology is specified by two constant fitting parameters in the late Universe, the Hubble constant $H_0$ and matter density (today) $\Omega_m$. Through fitting $(H_0, \Omega_m)$ to mock $\Lambda$CDM simulations in redshift bins, we confirm that $A := H_0^2 (1-\Omega_{m})$ and $B:= H_0^2 \Omega_m$ distributions spread and contract, respectively, with increasing bin redshift. Noting that $A = H_0^2 - B$, the spread in $A$ and contraction in $B$ corresponds to a spread in $H_0$, and consequently in $\Omega_m$. Restricted to non-negative energy densities, $A, B\geq 0$, the spread in $A$ yields a `pile up' around $A=0$ or $\Omega_m = 1$. At even higher redshifts, further spreading flattens $A$ and causes pile up near $\Omega_m = 0$. Thus, in generic higher redshift bins the Planck value $\Omega_m \sim 0.3$ appears with low probability. We explore if observational Hubble data, Type Ia supernovae and standardisable quasars substantiate the features. We confirm that observed data exhibit an increasing $\Omega_m$ (decreasing $H_0$) trend with increasing bin redshift and that such behaviour can arise randomly within the flat $\Lambda$CDM model with probability $p = 0.0021$ ($3.1 \, \sigma)$.

As the demand of astronomical observation rising, the telescope systems are becoming more and more complex. Thus, the observatory control software needs to be more intelligent, they have to control each instrument inside the observatory, finish the observation tasks autonomously, and report the information to users if needed. We developed a distributed autonomous observatory control framework named Remote Autonomous Control System 2nd, RACS2 to meet these requirements. The RACS2 framework uses decentralized distributed architecture, instrument control software and system service such as observation control service are implemented as different components. The communication between components is implemented based on a high-performance serialization library and a light-weighted messaging library.The interfaces towards python and Experimental Physics and Industrial Control System (EPICS) are implemented, so the RACS2 framework can communicate with EPICS based device control software and python-based software. Several system components including log, executor, scheduler and other modules are developed to help observation. Observation tasks can be programmed with python language, and the plans are scheduled by the scheduler component to achieve autonomous observation.A set of web service is implemented based on the FastAPI framework, with which user can control and manage the framework remotely.Based on the RACS2 framework, we have implemented the DATs telescope's observation system and the space object observation system.We performed remote autonomous observation and received many data with these systems.

Coronal mass ejections (CMEs) are the most geoeffective space weather phenomena, being associated with large geomagnetic storms, having the potential to cause disturbances to telecommunication, satellite network disruptions, power grid damages and failures. Thus, considering these storms' potential effects on human activities, accurate forecasts of the geoeffectiveness of CMEs are paramount. This work focuses on experimenting with different machine learning methods trained on white-light coronagraph datasets of close to sun CMEs, to estimate whether such a newly erupting ejection has the potential to induce geomagnetic activity. We developed binary classification models using logistic regression, K-Nearest Neighbors, Support Vector Machines, feed forward artificial neural networks, as well as ensemble models. At this time, we limited our forecast to exclusively use solar onset parameters, to ensure extended warning times. We discuss the main challenges of this task, namely the extreme imbalance between the number of geoeffective and ineffective events in our dataset, along with their numerous similarities and the limited number of available variables. We show that even in such conditions, adequate hit rates can be achieved with these models.

Determining black hole masses and accretion rates with better accuracy and precision is crucial for understanding quasars as a population. These are fundamental physical properties that underpin models of active galactic nuclei. A primary technique to measure the black hole mass employs the reverberation mapping of low-redshift quasars, which is then extended via the radius-luminosity relationship for the broad-line region to estimate masses based on single-epoch spectra. An updated radius-luminosity relationship incorporates the flux ratio of optical Fe ii to H$\beta$ ($\equiv \mathcal{R}_{\rm Fe}$) to correct for a bias in which more highly accreting systems have smaller line-emitting regions than previously realized. In this current work, we demonstrate and quantify the effect of using this Fe-corrected radius-luminosity relationship on mass estimation by employing archival data sets possessing rest-frame optical spectra over a wide range of redshifts. We find that failure to use a Fe-corrected radius predictor results in overestimated single-epoch black hole masses for the most highly accreting quasars. Their accretion rate measures ($L_{\rm Bol}/ L_{\rm Edd}$ and $\dot{\mathscr{M}}$), are similarly underestimated. The strongest Fe-emitting quasars belong to two classes: high-z quasars with rest-frame optical spectra, which given their extremely high luminosities, require high accretion rates, and their low-z analogs, which given their low black holes masses, must have high accretion rates to meet survey flux limits. These classes have mass corrections downward of about a factor of two, on average. These results strengthen the association of the dominant Eigenvector 1 parameter $\mathcal{R}_{\rm Fe}$ with the accretion process.

The Fermi Large Area Telescope (Fermi-LAT) Collaboration reported the Second Gamma-ray Burst Catalog (2FLGC), which comprises a subset of 29 bursts with photon energies above 10 GeV. Although the standard synchrotron forward-shock model has successfully explained the Gamma-ray burst (GRB) afterglow observations, energetic photons higher than 10 GeV from these transient events can hardly be described in this scenario. We present the closure relations (CRs) of synchrotron self-Compton (SSC) afterglow model in the adiabatic and radiative scenario and when the central engine injects continuous energy into the blastwave to study the evolution of the spectral and temporal indexes of those bursts reported in 2FLGC. We consider the SSC afterglow model evolving in stellar-wind and interstellar medium, and the CRs as a function of the radiative parameter, the energy injection index, and the electron spectral index for $1<p<2$ and $ 2\leq p$. We select all GRBs that have been modeled with both a simple or a broken power law in the 2FLGC. We found that the CRs of the SSC model can satisfy a significant fraction of burst that cannot be interpreted in the synchrotron scenario, even though those that require an intermediate density profile (e.g., GRB 130427A) or an atypical fraction of total energy given to amplify the magnetic field ($\varepsilon_B$). The value of this parameter in the SSC model ranges ($\varepsilon_B\approx 10^{-5} - 10^{-4}$) when the cooling spectral break corresponds to the Fermi-LAT band for typical values of GRB afterglow. The analysis shows that ISM is preferred for the scenario without energy injection and the stellar wind medium for an energy injection scenario.

We conduct a systematic search for quasars with periodic variations from the archival photometric data of the Zwicky Transient Facility (ZTF) by cross matching with the quasar catalogues of the Sloan Digital Sky Survey and V\'eron-Cetty & V\'eron. We first select out primitive periodic candidates using the methods of the generalized Lomb-Scargle periodogram and auto-correlation function, and then estimate the false-alarm probability of the periodicity and calculate the Bayesian information criterion to compare between periodic and purely stochastic models. As such, we finally identify a sample of 127 candidates with the most significant periodic variations out of 143,700 quasars. This is the largest periodic quasar sample so far, thus providing a useful guiding sample for studying origins of quasar periodicity considering the moderate sampling rate and high-quality photometry of the ZTF data. We summarize the basic properties of the sample and briefly discuss the implications.

The advent of space-based photometry missions in the early 21st century enabled the application to asteroseismic data of advanced inference techniques until then restricted to the field of helioseismology. The high quality of the observations, the discovery of mixed modes in evolved solar-like oscillators and the need for an improvement in the determination of stellar fundamental parameters such as mass, radius and age led to the development of sophisticated modelling tools, amongst which seismic inversions play a key role. In this review, we will discuss the existing inversion techniques for the internal structure of distant stars adapted from helio- to asteroseismology. We will present results obtained for various Kepler targets, their coupling to other existing modelling techniques as well as the limitations of seismic analyses and the perspectives for future developments of these approaches in the context of the current TESS and the future PLATO mission, as well as the exploitation of the mixed modes observed in post-main sequence solar-like oscillators, for which variational formulations might not provide sufficient accuracy.

The outer Galaxy beyond the Outer Arm represents a promising opportunity to study star formation in an environment vastly different from the solar neighborhood. In our previous study, we identified 788 candidate star-forming regions in the outer Galaxy (at galactocentric radii $R_{\rm G}$ $\ge$ 13.5 kpc) based on Wide-field Infrared Survey Explorer (WISE) mid-infrared (MIR) all-sky survey. In this paper, we investigate the statistical properties of the candidates and their parental molecular clouds derived from the Five College Radio Astronomy Observatory (FCRAO) CO survey. We show that the molecular clouds with candidates have a shallower slope of cloud mass function, a larger fraction of clouds bound by self-gravity, and a larger density than the molecular clouds without candidates. To investigate the star formation efficiency (SFE) at different $R_{\rm G}$, we used two parameters: 1) the fraction of molecular clouds with candidates and 2) the monochromatic MIR luminosities of candidates per parental molecular cloud mass. We did not find any clear correlation between SFE parameters and $R_{\rm G}$ at $R_{\rm G}$ of 13.5 kpc to 20.0 kpc, suggesting that the SFE is independent of environmental parameters such as metallicity and gas surface density, which vary considerably with $R_{\rm G}$. Previous studies reported that the SFE per year (SFE/yr) derived from the star-formation rate surface density per total gas surface density, HI plus H$_2$, decreases with increased $R_{\rm G}$. Our results might suggest that the decreasing trend is due to a decrease in HI gas conversion to H$_2$ gas.

Since the '80s the \textit{Einstein} observatory has shown the Young Stellar Objects (YSOs), emit X-rays with luminosities, in the 0.3--8 keV bandpass, up to $\rm 10^3$--$\rm 10^4$ times than the Sun and that the X-ray emission is highly variable. ROSAT has confirmed the pervasiveness of X-ray emission from YSOs and ASCA has provided evidence that the emission of Class I YSOs is largely originating from optical thin-plasma at temperature of 1-50 $\times 10^6$ K. These intrinsic, unexpected, properties and the transformational capabilities of the \textit{Chandra} and \textit{XMM-Newton} observatories has made X-rays a powerful tool to trace the star formation process up to distance of a few kpc around the Sun. Starting from the early evidences of the '80s and the intriguing questions they raised, I will summarize the results obtained and how they have influenced our current understanding of physical processes at work and I will discuss some of the still open issues and some of the likely avenues that next generation X-ray observatory will open.

The Parker Solar Probe mission provides a unique opportunity to characterize several features of the solar wind at different heliocentric distances. Recent findings have shown the existence of a different scale-invariant nature when moving away from the Sun. Here we provide, for the first time, how to reconcile these observational results on the nature of the radial evolution of the magnetic and velocity field fluctuations across the inertial range with two scenarios drawn from the magnetohydrodynamic theory. In details, we evidence (i) a magnetically-dominated scenario up to 0.4 AU and (ii) a fluid-like at larger distances. The observed breakdown is the result of the radial evolution of magnetic field fluctuations and plasma thermal expansion affecting the distribution of between magnetic and kinetic fluctuations. The two scenarios can be reconciled with those of Iroshnikov-Kraichnan and Kolmogorov pictures of turbulence in terms of an evolving nature of the coupling between fields. Our findings have important implications for turbulence studies and modeling approaches.

We report on the high-resolution spectroscopic observations of two planetary transits of the hot Jupiter KELT-7b ($M_{\rm p}$ $=$ 1.28 $\pm$ 0.17 M$_{\rm Jup}$, $T_{\rm eq}$ $=$ 2028 K) observed with the High Optical Resolution Spectrograph (HORuS) mounted on the 10.4-m Gran Telescopio Canarias (GTC). A new set of stellar parameters are obtained for the rapidly rotating parent star from the analysis of the spectra. Using the newly derived stellar mass and radius, and the planetary transit data of the Transiting Exoplanet Survey Satellite (TESS) together with the HORuS velocities and the photometric and spectroscopic data available in the literature, we update and improve the ephemeris of KELT-7b. Our results indicate that KELT-7 has an angle $\lambda$ = $-$10.55 $\pm$ 0.27 deg between the sky projections of the star's spin axis and the planet's orbital axis. By combining this angle and our newly derived stellar rotation period of 1.38 $\pm$ 0.05 d, we obtained a 3D obliquity $\psi$ = 12.4 $\pm$ 11.7 deg (or 167.6 deg), thus reinforcing that KELT-7 is a well-aligned planetary system. We search for the presence of H$\alpha$, Li I, Na I, Mg I, and Ca II features in the transmission spectrum of KELT-7b but we are only able to determine upper limits of 0.08-1.4 % on their presence after accounting for the contribution of the stellar variability to the extracted planetary spectrum. We also discuss the impact of stellar variability in the planetary data. Our results reinforce the importance of monitoring the parent star when performing high-resolution transmission spectroscopy of the planetary atmosphere in the presence of stellar activity.

We describe the on-line algorithms developed to probe Lumped Element Kinetic Inductance Detectors (LEKID) in this paper. LEKIDs are millimeter wavelength detectors for astronomy. LEKID arrays are currently operated in different instruments as: NIKA2 at the IRAM telescope in Spain, KISS at the Teide Observatory telescope in Tenerife, and CONCERTO at the APEX 12-meter telescope in Chile. LEKIDs are superconducting microwave resonators able to detect the incoming light at millimeter wavelengths and they are well adapted for frequency multiplexing (currently up to 360 pixels on a single microwave guide). Nevertheless, their use for astronomical observations requires specific readout and acquisition systems both to deal with the instrumental and multiplexing complexity, and to adapt to the observational requirements (e.g. fast sampling rate, background variations, on-line calibration, photometric accuracy, etc). This paper presents the different steps of treatment from identifying the resonance frequency of each LEKID to the continuous automatic control of drifting LEKID resonance frequencies induced by background variations.

Asteroid binaries found amongst the Near-Earth objects are believed to have formed from rotational fission. In this paper, we aim to study the dynamical evolution of asteroid systems the moment after fission. The initial condition is modelled as a contact binary, similar to that of Boldrin et al. (2016). Both bodies are modelled as ellipsoids, and the secondary is given an initial rotation angle about its body-fixed $y$-axis. Moreover, we consider six different cases, three where the density of the secondary varies, and three where we vary its shape. The simulations consider 45 different initial tilt angles of the secondary, each with 37 different mass ratios. We start the dynamical simulations at the moment the contact binary reaches a spin fission limit, and our model ensures that the closest distance between the surfaces of the two bodies is always kept at 1 cm. The forces, torques and gravitational potential between the two bodies are modelled using a newly developed surface integration scheme, giving exact results for two ellipsoids. We find that more than 80% of the simulations end with the two bodies impacting, and collisions between the bodies are more common when the density of the secondary is lower, or when it becomes more elongated. When comparing with data on asteroid pairs from Pravec et al. (2019) we find that variations in density and shape of the secondary can account for some of the spread seen in the rotation period for observed pairs. Furthermore, the secondary may also reach a spin limit for surface disruption, creating a ternary/multiple system. We find that secondary fission typically occurs within the first five hours after the contact binary separates, and is more common when the secondary is less dense or more elongated.

Planets open deep gaps in protoplanetary discs when their mass exceeds a gap opening mass, $M_{\rm gap}$. We use one- and two-dimensional simulations to study planet gap opening in discs with angular momentum transport powered by MHD disc winds. We parameterise the efficiency of the MHD disc wind angular momentum transport through a dimensionless parameter $\alpha_{\rm dw}$, which is an analogue to the turbulent viscosity $\alpha_{\rm v}$. We find that magnetised winds are much less efficient in counteracting planet tidal torques than turbulence is. For discs with astrophysically realistic values of $\alpha_{\rm dw}$, $M_{\rm gap}$ is always determined by the residual disc turbulence, and is a factor of a few to ten smaller than usually obtained for viscous discs. We introduce a gap opening criterion applicable for any values of $\alpha_{\rm v}$ and $\alpha_{\rm dw}$ that may be useful for planet formation population synthesis. We show that in discs powered by magnetised winds, growing planets detach from the disc at planet masses below $\sim 0.1M_{\rm Jup}$ inside 10 AU. This promotes formation of super-Earth planets rather than gas giants in this region, in particular precluding formation of hot jupiters in situ. On larger scales, ALMA gap opening planet candidates may be less massive than currently believed. Future high-resolution observations with instruments such as the extended ALMA, ngVLA, and SKA are likely to show abundant narrow annular features at $R < 10$ AU due to ubiquitous super-Earth planets.

We studied light curves of GJ 1243, YZ CMi, and V374 Peg, observed by TESS for the presence of stellar spots and stellar flares. One of the main goals was to model light curves of spotted stars to estimate the number of spots along with their parameters using our original BASSMAN software. The modeled light curves were subtracted from the observations to increase efficiency of flare detection. Flares were detected automatically with our new dedicated software WARPFINDER. We estimated the presence of two spots on GJ 1243 with mean temperature about 2800$\,$K and spottedness varying between $3\%-4\%$ of the stellar surface and two spots on V374 Peg with a mean temperature of about 3000$\,$K and spottedness about 6$\%$ of the stellar surface. On YZ CMi we found two different models for two light curves separated in time by one and a half year. One of them is three-spot model with mean temperature of about 3000$\,$K and spottedness of star about 9$\%$ of the stellar surface. The second is a four-spot model with mean temperature about 2800$\,$K and spottedness about 7$\%$ of the stellar surface. We tested whether the flares are distributed homogeneously in phase and if there is any correlation between the presence of spots and the distribution of flares. For YZ CMi one spot is in anticorrelation with the distribution of the flares and for GJ 1243 shows non-homogeneous distribution of flares.

Water (H2O) ice is ubiquitous component of the universe, having been detected in a variety of interstellar and Solar System environments where radiation plays an important role in its physico-chemical transformations. Although the radiation chemistry of H2O astrophysical ice analogues has been well studied, direct and systematic comparisons of different solid phases are scarce and are typically limited to just two phases. In this article, we describe the results of an in-depth study of the 2 keV electron irradiation of amorphous solid water (ASW), restrained amorphous ice (RAI) and the cubic (Ic) and hexagonal (Ih) crystalline phases at 20 K so as to further uncover any potential dependence of the radiation physics and chemistry on the solid phase of the ice. Mid-infrared spectroscopic analysis of the four investigated H2O ice phases revealed that electron irradiation of the RAI, Ic, and Ih phases resulted in their amorphization (with the latter undergoing the process more slowly) while ASW underwent compaction. The abundance of hydrogen peroxide (H2O2) produced as a result of the irradiation was also found to vary between phases, with yields being highest in irradiated ASW. This observation is the cumulative result of several factors including the increased porosity and quantity of lattice defects in ASW, as well as its less extensive hydrogen-bonding network. Our results have astrophysical implications, particularly with regards to H2O-rich icy interstellar and Solar System bodies exposed to both radiation fields and temperature gradients.

We report results for a complete sample of ten luminous radio-quiet quasars with large C IV equivalent widths (EW > 150 A). For 8/10 we performed Chandra snapshot observations. We find that, in addition to the enhanced C IV line EW, their He II and Mg II lines are enhanced, but the C III] line is not. Their X-ray emission is substantially stronger than expected from their ultraviolet luminosity. Additionally, these large C IV EW quasars show small C IV blueshifts and possibly low Eddington ratios, suggesting they are "extreme low Eigenvector 1 (EV1)" quasars. The mean excess He II EW is well-matched by Radiation Pressure Compression (RPC) photoionization models, with the harder aox ionizing spectrum. However, these results do not reproduce well the enhancement pattern of the C IV, Mg II, and C III] EWs, or the observed high C IV/Mg II ratio. RPC calculations indicate that the C IV/Mg II line ratio is an effective metallicity indicator, and models with sub-Solar metallicity gas and a hard ionizing continuum reproduce well the enhancement pattern of all four ultraviolet lines. We find that the C IV/Mg II line ratio in quasars is generally correlated with the excess X-ray emission. Extremely high EV1 quasars are characterized by high metallicity and suppressed X-ray emission. The underlying mechanism relating gas metallicity and X-ray emission is not clear, but may be related to radiation-pressure driven disk winds, which are enhanced at high metallicity, and consequent mass loading reducing coronal X-ray emission.

The gamma-ray binary 1FGL J1018.6-5856 consists of an O6V((f)) type star and an unknown compact object, and shows orbitally modulated emission from radio to very high energy gamma rays. The X-ray light curve shows a maximum around the same phase as the GeV emission, but also a secondary maximum between phases $\phi=0.2 - 0.6$. A clear solution to the binary system is important for understanding the emission mechanisms occurring within the system. In order to improve on the existing binary solution, we undertook radial velocity measurements of the optical companion using the Southern African Large Telescope, as well as analysed publicly available X-ray and GeV gamma-ray data. A search for periodicity in Fermi-LAT data found an orbital period of $P=16.5507\pm0.0004$ d. The best fit solution to the radial velocities, held at this new period, finds the system to be more eccentric than previous observations, $e=0.531 \pm 0.033$ with a longitude of periastron of $151.2 \pm 5.1^\circ$, and a larger mass function $f = 0.00432\pm 0.00077$ M$_\odot$. We propose that the peaks in the X-ray and gamma-ray light curves around phase 0 are due to the observation of the confined shock formed between the pulsar and stellar wind pointing towards the observer. The secondary increase or strong rapid variations of the X-ray flux at phases 0.25-0.75 is due to the interaction of multiple randomly oriented stellar wind clumps/pulsar wind interactions around apastron.

A reliable determination of the basic physical properties and variability patterns of hot emission-line stars is important for understanding the Be phenomenon and ultimately, the evolutionary stage of Be stars. This study is devoted to one of the most remarkable Be stars, V1294 Aql = HD 184279. We collected and analysed spectroscopic and photometric observations covering a time interval of about 25000 d (68 yr). We present evidence that the object is a single-line 192.9 d spectroscopic binary and estimate that the secondary probably is a hot compact object with a mass of about 1.1-1.2 solar masses. We found and documented very complicated orbital and long-term spectral, light, and colour variations, which must arise from a combination of several distinct variability patterns. Attempts at modelling them are planned for a follow-up study. We place the time behaviour of V1294 Aql into context with variations known for some other systematically studied Be stars and discuss the current ideas about the nature of the Be phenomenon.

There are many difficulties associated with forecasting high-energy solar particle events at Earth. One issue is understanding why some large solar eruptive events trigger ground level enhancement (GLE) events and others do not. In this work we perform 3D test particle simulations of a set of historic GLEs to understand more about what causes these powerful events. Particular focus is given to studying how the heliospheric current sheet (HCS) affects high-energy proton transport through the heliosphere following an event. Analysis of $\geq$M7.0 flares between 1976$-$2020 shows that active regions located closer to the HCS ($<$10$^{\circ}$) are more likely to be associated with a GLE event. We found that modelled GLE events where the source region was close to the HCS also led to increased heliospheric transport in longitude and higher count rates (when the Earth was located in the drift direction). In a model that does not include perpendicular diffusion associated with turbulence, the HCS is the dominant mechanism affecting heliospheric particle transport for GLE 42 and 69, and varying other parameters (e.g. a narrow, 10$^{\circ}$, or wider, 60$^{\circ}$, injection width) causes little change. Overall in our model, the HCS is relevant in 71$\%$ of our analysed GLEs and including it more accurately reproduces observed intensities near Earth. Our simulations enable us to produce model profiles at Earth that can be compared to existing observations by the GOES satellites and neutron monitors, as well as for use in developing future forecasting models.

Indirect observations of the cosmic-ray electron (CRE) distribution via synchrotron emission is crucial for deepening the understanding of the CRE transport in the interstellar medium, and in investigating the role of galactic outflows. In this paper, we quantify the contribution of diffusion and advection dominated transport of cosmic-ray electrons in the galaxy M51 considering relevant energy loss processes. We use recent measurement from M51 that allow for the derivation of the diffusion coefficient, the star formation rate, and the magnetic field strength. With this input, we solve the 3D transport equation numerically including the spatial dependence as provided by the measurements, using the open-source transport framework CRPropa (v3.1). We include three-dimensional transport (diffusion and advection), and the relevant loss processes. We find that the data can be described well with the parameters from recent measurements. For the best fit, it is required that the wind velocity, following from the observed star formation rate, must be decreased by a factor of 5. We find that a model in which the inner galaxy is dominated by advective escape and the outer galaxy by diffusive one fits the data well. Three-dimensional modeling of cosmic-ray transport in the face-on galaxy M51 allows for conclusions about the strength of the outflow of such galaxies by quantifying the need for a wind in the description of the cosmic-ray signatures. This opens up the possibility of investigating galactic winds in face-on galaxies in general.

X-ray polarimetry-timing is the characterization of rapid variability in the X-ray polarization degree and angle. As for the case of spectral-timing, it provides causal information valuable for reconstructing indirect maps of the vicinity of compact objects. To call X-ray polarimetry-timing a young field is somewhat of an understatement, given that the first X-ray mission truly capable of enabling polarimetry-timing analyses has only just launched at the time of writing. Now is therefore an exciting time for the field, in which we have theoretical predictions and are eagerly awaiting data. This Chapter discusses the theoretical expectations and also describes the data analysis techniques that can be used.

We probed the surface environment of large ($>$80 km in diameter) T-type asteroids, a taxonomic type relatively ill-constrained as an independent group, and discussed their place of origin. We performed spectroscopic observations of two T-type asteroids, (96) Aegle and (570) Kythera, over 2.8--4.0 $\mu$m using the Subaru telescope. With other T-types' spectra available in the literature and survey datasets, we strove to find commonalities and global trends in this group. We also utilised the asteroids' polarimetric data and meteorite spectra to constrain their surface texture and composition. Our targets exhibit red $L$-band continuum slopes similar to (1) Ceres and 67P/Churyumov-Gerasimenko, and have an OH-absorption feature with band centres $<$2.8 $\mu$m. (96) Aegle hints at a shallow N--H band near 3.1 $\mu$m and C--H band of organic materials over 3.4--3.6 $\mu$m, whereas no diagnostic bands of water ice and other volatiles exceeding the noise of the data were seen for both asteroids. The large T-type asteroids but (596) Scheila display similar spectral shapes to our targets. $\sim$50 \% of large T-types contain an absorption band near 0.6--0.65 $\mu$m likely associated with hydrated minerals. For T-type asteroids (except Jupiter Trojans) of all sizes, we found a weak correlation: the smaller the diameter and the closer the Sun, the redder the visible slope. The 2.9-$\mu$m band depths of large T-types suggest that they might have experienced aqueous alteration comparable to Ch-types but more intense than most of the main-belt asteroids. The polarimetric phase curve of the T-types is well described by a particular surface structure and their 0.5--4.0 $\mu$m reflectance spectra appear most similar to CI chondrites with grain sizes of $\sim$25--35 $\mu$m. Taken as a whole, we propose that large T-type asteroids might be dislodged roughly around 10 au in the early solar system.

Emission from the photosphere in gamma-ray burst (GRB) jets can be substantially affected by subphotospheric energy dissipation, which is typically caused by radiation-mediated shocks (RMSs). We study the observational characteristics of such emission, in particular the spectral signatures. Invoking an internal collision framework to estimate relevant shock initial conditions, we use an RMS model to generate synthetic photospheric spectra. The spectra are then fitted with a standard cutoff power-law (CPL) function to compare with corresponding GRB catalogues. We find mean values and standard deviations for the low-energy index and the peak energy as $\langle\alpha_{\rm cpl}\rangle = -0.76\pm 0.227$ and $\langle\log(E_{\rm peak}/{\rm keV})\rangle = 2.42\pm 0.408$, respectively. The range of $\alpha_{\rm cpl}$ values obtained cover a substantial fraction of the catalogued values, $\langle\alpha_{\rm cpl}^{\rm cat}\rangle = -0.80 \pm 0.311$. This requires that the free fireball acceleration starts at $r_0 \sim 10^{10}~$cm, which is in agreement with hydrodynamical simulations. The CPL function generally provides a good fit, even though the synthetic spectra typically exhibit an additional break at lower energies. We also identify a non-negligible parameter region for what we call ``optically shallow shocks'': shocks that do not accumulate enough scatterings to reach a steady-state spectrum before decoupling. These occur for optical depths $\tau \lesssim 55 \, u_u^{-2}$, where $u_u = \gamma_u\beta_u\sim 2$ is the dimensionless specific momentum of the upstream as measured in the shock rest frame. We conclude that photospheric emission, which has passed through an RMS, is spectrally consistent with the dominant fraction of observed bursts.

Active Galactic Nuclei are powered by accretion of matter onto a supermassive black hole (SMBH) of mass Mbh ~ 10^{5}-10^{9} Msun. The accretion process is indeed the most efficient mechanism for energy release we currently know of, with up to ~30-40% of the gravitational rest mass energy that can be converted into radiation. The vast majority of this energy is released at high energy (UV-X-rays) within the central $100$ gravitational radii from the central SMBH. This energy release occurs through a variety of emission and absorption mechanisms, spanning the entire electromagnetic spectrum. The UV emission being commonly explained by the presence of an optically thick accretion flow, while the X-rays generally require a hotter, optically thinner, plasma, the so-called X-ray corona. If outflows are present, they can also extract a significant part of the gravitational power. With an origin in the deep potential well of the SMBH, the study of the high-energy emission of AGN give a direct insight into the physical properties of the accretion, ejection and radiative mechanisms occurring in the SMBH close environment. While not exhaustive, we discuss in this chapter our present understanding of these mechanisms, the limitations we are currently facing and the expected advances in the future.

Extended gamma-ray emission, interpreted as halos formed by the inverse-Compton scattering of ambient photons by electron-positron pairs, is observed toward a number of middle-aged pulsars. The physical origin and actual commonness of the phenomenon in the Galaxy remain unclear. The conditions of pair confinement seem extreme compared to what can be achieved in recent theoretical models. We searched for scenarios minimizing as much as possible the extent and magnitude of diffusion suppression in the halos in J0633+1746 and B0656+14, and explored the implications on the local positron flux if they are applied to all nearby middle-aged pulsars. We used a phenomenological static two-zone diffusion framework and compared its predictions with Fermi-LAT and HAWC observations of the two halos, and with the local positron flux measured with AMS-02. While strong diffusion suppression by 2-3 orders of magnitude at ~100TeV is required by the data, it is possible to find solutions with diffusion suppression extents as small as 30pc for both objects. If all nearby middle-aged pulsars develop such halos, their combined positron flux including the contribution from Geminga would saturate the >100GeV AMS-02 measurement for injection efficiencies that are much smaller than those inferred for the canonical halos in J0633+1746 and B0656+14, and more generally with the values typical of younger pulsar wind nebulae. Conversely, if positrons from other nearby pulsars are released in the interstellar medium without any confinement around the source, their total positron flux fits into the observed spectrum for the same injection efficiencies of a few tens of percent for all pulsars, from kyr-old objects powering pulsar wind nebulae to 100kyr-old objects like J0633+1746 and B0656+14. It seems a simpler scenario to assume that most middle-aged pulsars do not develop halos (abridged).

We present analysis of the starspot properties and chromospheric activity on HD 134319 using high precision photometry by TESS in sectors 14-16 (T1), 21-23 (T2) %in sectors 14-16 and 21-23 and high-resolution spectroscopy by OHP/ELODIE and Keck/HIRES during years 1995-2013. We applied a two-spot model with GLS determined period $P=4.436391\pm0.00137$ day to model chunks sliding over TESS light curve, and measured relative equivalent widths of Ca II H and K, H$\beta$ and H$\alpha$ emissions by subtracting overall spectrum from individual spectrum. It was found that a two-spot configuration, i.e. a primary, slowly evolving and long-lasting spot (P) plus a secondary and rapidly evolving spot S, was capable of explaining the data, although the actual starspot distribution is unable to derived from collected data. Despite the spot radius-latitude degeneracy revealed in the best-fit solutions, a sudden alternation between P and S radii followed by gradual decrease of S in T1 and the decrease of both P and S from T1 to T2 were significant, corresponding to the evolution of magnetic activity. Besides, S revealed rotation and oscillatory longitude migration synchronized to P in T1, but held much larger migration than P in T2. This might indicate the evolution of internal magnetic configuration. Chromospheric activity indicators were found to tightly correlated with each other and revealed rotational modulation as well as a long-term decrease of emissions, implying the existence and evolution of magnetic acitivity on HD 134319.

We consider quintessence models within 4D effective descriptions of gravity coupled to two scalar fields. These theories are known to give rise to viable models of late-time cosmic acceleration without any need for flat potentials, and so they are potentially in agreement with the dS Swampland conjecture. In this paper we investigate the possibility of consistently embedding such constructions in string theory. We identify situations where the quintessence fields are either closed string universal moduli or non-universal moduli such as blow-up modes. We generically show that no trajectories compatible with today's cosmological parameters exist, if one starts from matter-dominated initial conditions. It is worth remarking that universal trajectories compatible with observations do appear, provided that the starting point at early times is a phase of kinetic domination. However, justifying this choice of initial conditions on solid grounds is far from easy. We conclude by studying Q-ball formation in this class of models and discuss constraints coming from Q-ball safety in all cases analyzed here.

We discuss cosmology based on the cuscuton gravity theory to resolve the anomaly of the observational $^4$He abundance reported by the EMPRESS collaboration. We find that the gravitational constant $G_{\rm cos}$ in Friedmann equation should be smaller than the Newton's constant ${G_{\rm N}}$ such that ${\Delta G_{\rm N}}/{G_{\rm N}} \equiv (G_{\rm cos}-G_{\rm N})/{G_{\rm N}} = -0.086_{-0.028}^{+0.026} \quad(68 \% \text { C.L. })$ in terms of big-bang nucleosynthesis, which excludes ${\Delta G_{\rm N}}=0$ at more than 95~$\% \text { C.L. }$ To fit the data, we obtain a negative mass squared of a non-dynamical scalar field with the Planck-mass scale as $\sim - {\cal O}(1) {M_{\rm PL}^2} ({\mu}/{0.5 M_{\rm PL}})^{4}$ with the cuscuton mass parameter $\mu$. This fact could suggest the need for modified gravity theories such as the cuscuton gravity theory with a quadratic potential, which can be regarded as the low-energy Ho\v{r}ava-Lifshitz gravity, and might give a hint of quantum gravity.

We explore the suggestion that the neutron lifetime puzzle might be resolved by neutrons decaying into dark matter through the process, n \rightarrow \chi\chi\chi, with \chi having a mass one third of that of the neutron. In particular, we examine the consequences of such a decay mode for the properties of neutron stars. Unlike an earlier suggested decay mode, in order to satisfy the constraints on neutron star mass and tidal deformability, there is no need for a strong repulsive force between the dark matter particles. This study suggests the possibility of having hot dark matter at the core of the neutron star and examines the possible signal of neutrons decaying in this way inside the neutron star right after its birth.

Entropy production is a necessary ingredient for addressing the over-population of thermal relics. It is widely employed in particle physics models for explaining the origin of dark matter. A long-lived particle that decays to the known particles, while dominating the universe, plays the role of the dilutor. We point out the impact of its partial decay to dark matter on the primordial matter power spectrum. For the first time, we derive a stringent limit on the branching ratio of the dilutor to dark matter from large scale structure observation using the SDSS data. This offers a novel tool for testing models with a dark matter dilution mechanism. We apply it to the left-right symmetric model and show that it firmly excludes a large portion of parameter space for right-handed neutrino warm dark matter.

We explore a mechanism for producing the baryon asymmetry and dark matter in models with multiple hidden sectors that are Standard Model-like but with varying Higgs mass parameters. If the field responsible for reheating the Standard Model and the exotic sectors carries an asymmetry, that asymmetry can be converted into a baryon asymmetry using the standard sphaleron process. A hidden sector with positive Higgs mass squared can accommodate dark matter with its baryon asymmetry, and the larger abundance of dark matter relative to baryons is explained by the fact that the dark sphaleron is active all the way down the hidden sector QCD scale. This scenario predicts that dark matter is clustered in large dark nuclei and that $\Delta N_{\rm eff} \gtrsim 0.05$, which may be observable in the next generation Cosmic Microwave Background (CMB) experiment CMB-S4.

We employ an unregulated computation the graviton self-energy from gravitons on de Sitter background to infer the renormalized result. This is used to quantum-correct the linearized Einstein equation. We solve this equation for the potentials which represent the gravitational response to static, point mass. We find large spatial and temporal logarithmic corrections to the Newtonian potential and to the gravitational shift. Although suppressed by a minuscule loop-counting parameter, these corrections cause perturbation theory to break down at large distances and late times. Another interesting fact is that gravitons induce up to three large logarithms whereas a loop of massless, minimally coupled scalars produces only a single large logarithm. This is in line with corrections to the graviton mode function: a loop of gravitons induces two large logarithms whereas a scalar loop gives none.

We investigate the second-order effective energy-momentum tensor (2EMT) constructed by the quadratic terms of the linear scalar cosmological perturbations while the universe is dominated by a scalar field. We show that 2EMT is gauge dependent. We then study 2EMT in three (longitudinal, spatially flat, and comoving) gauge conditions in the slow-roll stage of inflation. We find that 2EMT exhibits an effective fluid of w=-1/3 on super-horizon scales in all of those gauge conditions.

We propose a Standard Model extension, coined VISH$\nu$ (Variant-axIon Seesaw Higgs $\nu$-trino), that is a variation of its predecessor, the $\nu$DFSZ model. In accounting for the origin of neutrino masses, dark matter and the baryon asymmetry of the universe, VISH$\nu$ inherits the explanatory power of $\nu$DFSZ while, of course, resolving the strong $CP$ problem. In both models, the electroweak scale is naturally protected in the presence of a high seesaw scale that is identified with the Peccei-Quinn (PQ) spontaneous symmetry breaking scale. Importantly, VISH$\nu$ extends the cosmological reach of $\nu$DFSZ to include a viable period of inflation and, through a variant flavour coupling structure, evades a cosmological domain wall problem. The focus of this paper is thus on the inflationary dynamics of VISH$\nu$ and their naturalness in the sense of radiative stability. In particular, we find that non-minimal gravitational couplings of the VISH$\nu$ scalar fields naturally give rise to a selection of viable inflatons. An axion mass window [$40\mu\text{eV}, \sim 2\text{meV}$], which is accessible to forthcoming searches, results for the case that PQ symmetry is restored during the (p)reheating phase.

We present the results from the analysis of galaxy rotation curves with Verlinde's emergent gravity. We use the data in the SPARC (Spitzer Photometry and Accurate Rotation Curves) database, which contains a sample of 175 nearby disk galaxies with 3.6 $\mu$m surface photometry and rotation curves. We compute the gravitational acceleration at different galactocentric radii expected from the baryon distribution of the galaxies with the emergent gravity, and compare it with the observed gravitational acceleration derived from galactic rotation curves. The predicted and observed accelerations agree well with a mean offset $\mu{\rm [log(g_{obs})-log(g_{Ver})]}=-0.060\pm0.004$ and a scatter $\sigma{\rm [log(g_{obs})-log(g_{Ver})]}=0.137\pm0.004$ by assuming a de Sitter universe. These offset and scatter become smaller when we assume a more realistic universe, quasi de Sitter universe, as $\mu=-0.027\pm0.003$ and $\sigma=0.129\pm0.003$. Our results suggest that Verlinde's emergent gravity could be a good solution to the missing mass problem without introducing dark matter.

We consider a pseudoscalar axion-like field coupled to a Chern-Simons gravitational anomaly term. The axion field backreacts on a rotating Kerr black hole background, resulting in modifications in the spacetime. In an attempt to determine potentially observable signatures, we study the angular momentum of the system of the modified Kerr-like black hole and the axionic matter outside the horizon of the black hole. As the strength of the coupling of the axion field to the Chern-Simons term is increasing, the requirement that the total angular momentum of the system remain constant forces the black hole angular momentum to decrease. There exists a critical value of this coupling beyond which the black hole starts to rotate in the opposite direction, with an increasing magnitude of its angular momentum. We interpret this effect as a consequence of the exchange of energy between the axionic matter and the gravitational anomaly, which is sourced by the rotating black hole.