Papers for Tuesday, Jan 02 2024

We show evidence of particle acceleration at GEV energies associated directly with protons from the prompt emission of a long-duration M6-class solar flare on July 17, 2023, rather than from protons acceleration by shocks from its associated Coronal Mass Ejection (CME), which erupted with a speed of 1342 km/s. Solar Energetic Particles (SEP) accelerated by the blast have reached Earth, up to an almost S3 (strong) category of a radiation storm on the NOAA scale. Also, we show a temporal correlation between the fast rising of GOES-16 proton and muon excess at ground level in the count rate of the New-Tupi muon detector at the central SAA region. A Monte Carlo spectral analysis based on muon excess at New-Tupi is consistent with the acceleration of electrons and protons (ions) up to relativistic energies (GeV energy range) in the impulsive phase of the flare. In addition, we present another two marginal particle excesses (with low confidence) at ground-level detectors in correlation with the solar flare prompt emission.

In this work, we compare the SMBH and host galaxy properties of X-ray obscured and unobscured AGN. For that purpose, we use $\sim 35 000$ X-ray detected AGN in the 4XMM-DR11 catalogue for which there are available measurements for their X-ray spectral parameters, from the XMM2Athena Horizon 2020 European project. We calculate the host galaxy properties via SED fitting analysis. Our final sample consists of 1 443 AGN. In the first part of our analysis, we use different N$_H$ thresholds (10$^{23}$ cm$^{-2}$ or 10$^{22}$ cm$^{-2}$), taking also into account the uncertainties associated with the N$_H$ measurements, to classify these sources into obscured and unobscured. We find that obscured AGN tend to live in more massive systems that have lower SFR compared to their unobscured counterparts. However, only the difference in stellar mass, M$_*$, appears statistically significant ($>2\sigma$). The results do not depend on the N$_H$ threshold used to classify AGN. The differences in M$_*$ and SFR are not statistically significant for luminous AGN ($\rm log (L_{X,2-10 KeV}/erg s^{-1})> 44$). Our findings also show that unobscured AGN have, on average, higher specific black hole accretion rates compared to their obscured counterparts. In the second part of our analysis, we cross-match the 1 443 X-ray AGN with the SDSS DR16 quasar catalogue to obtain information on the SMBH properties of our sources. This results in 271 type 1 AGN, at $\rm z<1.9$. Our findings show that type 1 AGN with increased N$_H$ ($>10^{22}$ cm$^{-2}$) tend to have higher M$_{BH}$ compared to AGN with lower N$_H$ values, at similar M$_*$. The M$_{BH}$/M$_*$ ratio remains consistent for N$_H$ values below 10$^{22}$ cm$^{-2}$, but it exhibits signs of an increase at higher N$_H$ values. Finally, we detect a correlation between $\Gamma$ and Eddington ratio, but only for type 1 sources with N$_H<10^{22}$ cm$^{-2}$.

Low-mass giants with large amounts of lithium (Li) have challenged stellar evolution for decades. One of the possibilities usually discussed to explain them involves the interaction with a close binary companion. This predicts that when compared against their non-enriched counterparts, Li-rich giants should preferentially be found as part of binary systems. In order to test this scenario, we assemble a sample of 1418 giants with radial velocities (RVs) from RAVE, GALAH, and Gaia, as well as stellar parameters and Li abundances from GALAH. Evolutionary states can be determined for 1030 of these giants. We develop a method that quantifies the degree of RV variability, which we use as a proxy for close binary companions. The method is tested and calibrated against samples of known RV standard stars and known spectroscopic binaries. We also compare the results of our RV variability analysis with binarity indicators from Gaia. We find that the accuracy of the classification is controlled by the precision of the RVs, which for the set of RVs available for the giants is 80-85%. Consistent with seismic studies, the resulting sample of giants contains a fraction of Li-rich objects in the red clump (RC) that is twice as large as that for first-ascent giants (RGB). Among RC giants, the fractions of Li-rich objects with high RV variability and with no RV variability are the same as those for Li-normal objects, which argues against a binary interaction scenario for the genesis of the bulk of Li-rich giants at that evolutionary stage. On the other hand, Li-rich giants in the RGB appear to have a small but detectable preference for higher RV variability, and thus possibly a larger close binary fraction, than the Li-normal giants at that stage. Additional measurements of the RVs of these giants at higher RV precision would greatly help confirm and more robustly quantify these results.

Observatories need to measure and evaluate the scientific output and overall impact of their facilities. An observatory bibliography consists of the papers published using that observatory's data, typically gathered by searching the major journals for relevant keywords. Recently, the volume of literature and methods by which the publications pool is evaluated has increased. Efficient and standardized procedures are necessary to assign meaningful metadata; enable user-friendly retrieval; and provide the opportunity to derive reports, statistics, and visualizations to impart a deeper understanding of the research output. In 2021, a group of observatory bibliographers from around the world convened online to continue the discussions presented in Lagerstrom (2015). We worked to extract general guidelines from our experiences, techniques, and lessons learnt. The paper explores the development, application, and current status of telescope bibliographies and future trends. This paper briefly describes the methodologies employed in constructing databases, along with the various bibliometric techniques used to analyze and interpret them. We explain reasons for non-standardization and why it is essential for each observatory to identify metadata and metrics that are meaningful for them; caution the (over-)use of comparisons among facilities that are, ultimately, not comparable through bibliometrics; and highlight the benefits of telescope bibliographies, both for researchers within the astronomical community and for stakeholders beyond the specific observatories. There is tremendous diversity in the ways bibliographers track publications and maintain databases, due to parameters such as resources, type of observatory, historical practices, and reporting requirements to funders and outside agencies. However, there are also common sets of Best Practices.

The centre of the Milky Way hosts a supermassive black hole of 4 million solar masses called Sagittarius A*. This object has been observed for more than 20 years in the near infrared. This has confirmed some effects of General Relativity. In addition, recurrent observations have made it possible to detect flares, i.e. a much larger flux than the average, with a variability of the order of 30 minutes to 1 hour. In 2018, GRAVITY, using the 4 large telescopes of the VLTI/ESO, observed an orbital motion of the source of these flares. This thesis focuses on the modelling of these flares, using models of varying complexity, including one based on the phenomenon of magnetic reconnection. The latter corresponds to an abrupt change in the magnetic configuration around the black hole, releasing a large amount of energy. We are also looking at the problem of polarisation in General Relativity.

In this paper, we elaborate on correctly predicting \'Echelle spectrograms by employing the fully three-dimensional representation of Snell's law to model the effects of prisms as cross-dispersers in \'Echelle spectrographs. We find that it is not sufficient to simply apply the frequently used trigonometric prism dispersion equation to describe recorded spectra. This vector equation approach is not limited to a single dispersive element when modeling multi-prism cross-disperser configurations. Our results help to understand the main levers in an \'Echelle spectrograph as well as contribute to auto-calibration algorithms for minimizing calibration efforts in daily operation.

We present an X-ray and UV investigation of five X-ray flares detected on two active systems, CC Eri and AB Dor, using the AstroSat observatory. The peak X-ray luminosities of the flares in the 0.3$-$7.0 keV band are found to be within 10$^{31-33}$ erg s$^{-1}$. Preliminary spectral analysis indicates the presence of three and four-temperature corona for CC Eri and AB Dor, respectively, where the highest temperature is found to vary with flare. The flare temperatures peaked at 51$-$59 MK for CC Eri and 29$-$44 MK for AB Dor. The peak emission measures of the flaring loops are estimated to be $\sim$10$^{54}$ for CC Eri and $\sim$10$^{55}$ cm$^{-3}$ for AB Dor. Global metallic abundances were also found to increase during flares.

Utilizing observations from the New Vacuum Solar Telescope (NVST), Solar Dynamics Observatory (SDO), and Solar Terrestrial Relations Observatory-Ahead (STEREO-A), we investigate the event from two distinct observational perspectives: on the solar disk using NVST and SDO, and on the solar limb using STEREO-A. We employ both a non-linear force-free field model and a potential field model to reconstruct the coronal magnetic field, aiming to understand its magnetic properties. Two precursor jet-like activities were observed before the eruption, displaying an untwisted rotation. The second activity released an estimated twist of over two turns. During these two jet-like activities, Y-shaped brightenings, newly emerging magnetic flux accompanied by magnetic cancellation, and the formation of newly moving fibrils were identified. Combining these observational features, it can be inferred that these two precursor jet-like activities released the magnetic field constraining the filament and were triggered by newly emerging magnetic flux. Before the filament eruption, it was observed that some moving flows had been ejected from the site as the onset of two jet-like activities, indicating the same physical process as two jet-like activities. Extrapolations revealed that the filament laid under the height of the decay index of 1.0 and had strong magnetic field (540 Gauss) and a high twisted number (2.4 turns) before the eruption. An apparent rotational motion was observed during the filament eruption. We deduce that the solar filament, exhibiting an inverted U-shape, is a significantly twisted flux rope. The eruption of the filament was initiated by the release of constraining magnetic fields through continuous magnetic reconnection. This reconnection process was triggered by the emergence of newly magnetic flux.

The FIR distribution at high Galactic latitudes, observed with Planck, is filamentary with coherent structures in polarization. These structures are also closely related to HI filaments with coherent velocity structures. There is a long-standing debate about the physical nature of these structures. They are considered either as velocity caustics, fluctuations engraved by the turbulent velocity field or as cold three-dimensional density structures in the interstellar medium (ISM). We discuss different approaches to data analysis and interpretation in order to work out the differences. We considered mathematical preliminaries for the derivation of caustics that characterize filamentary structures in the ISM. Using the Hessian operator, we traced individual FIR filamentary structures in HI from channel maps as observed and alternatively from data that are provided by the velocity decomposition algorithm (VDA). VDA is claimed to separate velocity caustics from density effects. Based on the strict mathematical definition, the so-called velocity caustics are not actually caustics. These VDA data products may contain caustics in the same way as the original HI observations. Caustics derived by a Hessian analysis of both databases are nearly identical with a correlation coefficient of 98%. However, the VDA algorithm leads to a 30% increase in the alignment uncertainties when fitting FIR/HI orientation angles. We used HI absorption data to constrain the physical nature of FIR/HI filaments and determine spin temperatures and volume densities of FIR/HI filaments. HI filaments exist as CNM structures; outside the filaments no CNM absorption is detectable. The CNM in the diffuse ISM is exclusively located in filaments with FIR counterparts. These filaments at high Galactic latitudes exist as cold density structures; velocity crowding effects are negligible.

Neutron star contains a large number of nucleons and muons, if coupled with hidden ultralight particles, the orbit motion can produce sizable energy flux in addition to the binary's gravitational quadrupole radiation. Here, we explore a scenario in which the scalar boson sourced by the binary is also coupled to the lowest dimensional photon operator, through which indirect electromagnetic radiation is generated beyond the scalar's mass threshold. Using the observational data of two pulsar binaries, we place stringent constraints on the strength of such couplings.

Atacama Large Millimeter/Submillimeter Array (ALMA) has revolutionized the field of dust polarization in protoplanetary disks across multiple wavelengths. Previous observations and empirical modeling suggested multiple mechanisms of dust polarization toward HL Tau, including grain alignment and dust scattering. However, a detailed modeling of dust polarization based on grain alignment physics is not yet available. Here, using our updated POLARIS code, we perform numerical modeling of dust polarization arising from both grain alignment by Magnetically Enhanced Radiative Torque (MRAT) mechanism and self-scattering to reproduce the HL Tau polarization observed at three wavelengths 0.87, 1.3, and 3.1$\,$mm. Our modeling results show that the observed multi-wavelength polarization could be reproduced only when large grains contain embedded iron inclusions and those with slow internal relaxation must have wrong internal alignment (i.e., the grain's major axis parallel to its angular momentum). The abundance of iron embedded inside grains in the form of clusters is constrained to be $\gtrsim 16$%, and the number of iron atoms per cluster is $N_{\rm cl} \sim 2\times10^3$. Maximum grain sizes probed at wavelengths $\lambda$ = 0.87, 1.3, and 3.1$\,$mm are constrained at $\sim$ 60, 90, and 130$\,\mu$m, respectively. Assuming a dust differential settling effect with grain sizes from the constraint gives the value of maximum grain size at the disk mid-plane to be millimeter-scaled.

Comets would have amorphous ice rather than crystalline one at the epoch of their accretion. Cometary ice contains some impurities that govern the latent heat of ice crystallization, $L_{\rm cry}$. However, it is still controversial whether the crystallization process is exothermic or endothermic. In this study, we perform one-dimensional simulations of the thermal evolution of km-sized comets and investigate the effect of the latent heat. We find that the depth where amorphous ice can survive significantly depends on the latent heat of ice crystallization. Assuming the cometary radius of 2 km, the depth of the amorphous ice mantle is approximately 100 m when the latent heat is positive (i.e., the exothermic case with $L_{\rm cry} = + 9 \times 10^{4}$ J/kg). In contrast, when we consider the impure ice representing the endothermic case with $L_{\rm cry} = - 9 \times 10^{4}$ J/kg, the depth of the amorphous ice mantle could exceed 1 km. Although our numerical results indicate that these depths depend on the size and the accretion age of comets, the depth in a comet with the negative latent heat is a few to several times larger than the positive case for a given comet size. This work suggests that the spatial distribution of the ice crystallinity in a comet nucleus depends on the latent heat, which can be different from the previous estimates assuming pure water ice.

A conducting cylinder with a central source of electrons, in a uniform magnetic field along its axis, and radial temperature gradient, is considered at the stationary state. Interaction of heat flux, magnetic field and charge distribution is discussed. Four different models are considered, regarding of the electronic supply and possibility of electrons to leave the cylinder.

Direct imaging of Earth-like exoplanets is one of the most prominent scientific drivers of the next generation of ground-based telescopes. Typically, Earth-like exoplanets are located at small angular separations from their host stars, making their detection difficult. Consequently, the adaptive optics (AO) system's control algorithm must be carefully designed to distinguish the exoplanet from the residual light produced by the host star. A new promising avenue of research to improve AO control builds on data-driven control methods such as Reinforcement Learning (RL). RL is an active branch of the machine learning research field, where control of a system is learned through interaction with the environment. Thus, RL can be seen as an automated approach to AO control, where its usage is entirely a turnkey operation. In particular, model-based reinforcement learning (MBRL) has been shown to cope with both temporal and misregistration errors. Similarly, it has been demonstrated to adapt to non-linear wavefront sensing while being efficient in training and execution. In this work, we implement and adapt an RL method called Policy Optimization for AO (PO4AO) to the GHOST test bench at ESO headquarters, where we demonstrate a strong performance of the method in a laboratory environment. Our implementation allows the training to be performed parallel to inference, which is crucial for on-sky operation. In particular, we study the predictive and self-calibrating aspects of the method. The new implementation on GHOST running PyTorch introduces only around 700 microseconds in addition to hardware, pipeline, and Python interface latency. We open-source well-documented code for the implementation and specify the requirements for the RTC pipeline. We also discuss the important hyperparameters of the method, the source of the latency, and the possible paths for a lower latency implementation.

The intrinsic alignment (IA) of galaxies acts as a systematic effect in weak lensing measurements and tends to introduce biases. It mimics the gravitational lensing signal which makes it difficult to distinguish it from the true gravitational weak lensing effect. Hence, it is critical to account for the noise for correctly interpreting the results. This study aims at a quantitative analysis of IA using the Tidal Alignment and Tidal Torquing (TATT) model. We also investigate how the signals for shear and galaxy-galaxy lensing behave upon changing the parameters of the TATT model. The data for this study was prepared with a computational pipeline based on the Cocoa model to explore the parameter space of the intrinsic shape signal. Through this work, we identify that linear terms of the intrinsic shape signal are dominant in the case of GGL while the higher-order terms dictate the shear signal.

Synthetic data sets are used in cosmology to test analysis procedures, to verify that systematic errors are well understood and to demonstrate that measurements are unbiased. In this work we describe the methods used to generate synthetic datasets of Lyman-$\alpha$ quasar spectra aimed for studies with the Dark Energy Spectroscopic Instrument (DESI). In particular, we focus on demonstrating that our simulations reproduces important features of real samples, making them suitable to test the analysis methods to be used in DESI and to place limits on systematic effects on measurements of Baryon Acoustic Oscillations (BAO). We present a set of mocks that reproduce the statistical properties of the DESI early data set with good agreement. Additionally, we use full survey synthetic data to forecast the BAO scale constraining power with DESI.

It has been more than 30 years since the enigmatic 21 {\mu}m emission feature was first discovered in protoplanetary nebulae (PPNs). Although dozens of different dust carrier candidates have been proposed, there is as yet no widely accepted one. We present the results of molecular observations toward 21{\mu}m objects using the 10m Submillimeter Telescope of Arizona Radio Observatory at the 1.3 mm band and the 13.7 m telescope of Purple Mountain Observatory at the 3mm band, aiming to investigate whether the gas-phase environments of these unusual sources have some peculiarities compared to normal PPNs. We detect 31 emission lines belonging to seven different molecular species, most of which are the first detection in 21 {\mu}m PPNs. The observations provide clues on the identification of the 21 {\mu}m feature. We report a correlation study between the fractional abundance of gas-phase molecules and the strengths of the 21 {\mu}m emission. Our study shows that given the small sample size, the 21 {\mu}m feature has weak or no correlations with the gas-phase molecules. Future radio observations of high spatial and spectral resolution toward a large sample are desirable to elucidate the 21 {\mu}m emission phenomena.

We conducted 4-night multiwavelength observations of an active M-dwarf star EV Lac on 2022 October 24$-$27 with simultaneous coverage of soft X-rays (NICER; 0.2$-$12 $\mathrm{keV}$, Swift XRT; 0.2$-$10 $\mathrm{keV}$), near-ultraviolet (Swift UVOT/UVW2; 1600$-$3500 \r{A}), optical photometry (TESS; 6000$-$10000 \r{A}), and optical spectroscopy (Nayuta/MALLS; 6350$-$6800 \r{A}). During the campaign, we detected a flare starting at 12:28 UTC on October 25 with its white-light bolometric energy of $3.4 \times 10^{32}$ erg. At about 1 hour after this flare peak, our $\mathrm{H\alpha}$ spectrum showed a blue-shifted excess component at its corresponding velocity of $\sim 100 \: \mathrm{km \: s^{-1}}$. This may indicate that the prominence erupted with a 1-hour delay of the flare peak. Furthermore, the simultaneous 20-second cadence near-ultraviolet and white-light curves show gradual and rapid brightening behaviors during the rising phase at this flare. The ratio of flux in NUV to white light at the gradual brightening was $\sim 0.49$, which may suggest that the temperature of the blackbody is low ($< 9000 \: \mathrm{K}$) or the maximum energy flux of a nonthermal electron beam is less than $5\times10^{11} \: \mathrm{erg \: cm^{-2} \: s^{-1}}$. Our simultaneous observations of NUV and white-light flare raise the issue of a simple estimation of UV flux from optical continuum data by using a blackbody model.

Some theoretical models for the early universe predict a spike-type enhancement in the primordial power spectrum on a small scale, which would result in forming early-formed dark matter halos (EFHs). In this work, we study the CMB lensing effect, considering the existence of EFHs, and investigate the potential to probe the EFHs and the primordial perturbations on scales smaller than $1\mathrm{Mpc}$. We numerically calculate the angular power spectrum of the lensing potential and the lensed CMB anisotropy of temperature, E-mode, and B-mode polarization, including the nonlinear effects of EFHs. We find the possibility that the lensed CMB temperature anisotropy is significantly enhanced on small scales, $\ell>1000$, and could be tested by component decomposition of observed signals through multi-frequency observations. Through the calculation with different models of the spiky-type power spectrum, we demonstrate that the accurate measurements of the CMB lensing effect would provide insight into the abundance of EFHs within the limited mass range around $10^{12}M_\odot$ and the primordial power spectrum on the limited scales around $k\sim 1\mathrm{Mpc}^{-1}$. In particular, we find that the existence of such EFHs can amplify the lensed anisotropy of CMB B-mode polarization even on large scales, $\ell <100$, as the overall enhancement by $\sim 10 \%$ level compared to the standard structure formation model without EFHs. Therefore, future CMB measurements such as the LiteBIRD satellite can probe the existence of the EFHs and the spike-type primordial power spectrum through the precise measurement of the large-scale CMB B-mode polarization.

We considered two sequences of spiral galaxies with different shapes of the radial gas-phase oxygen abundance distributions from the galaxies in the MaNGA survey: (1) Galaxies in which the gradient is well approximated by a single linear relation across the whole disc, that is, galaxies with an S (slope) gradients, (2) galaxies in which the metallicity in the inner region of the disc is at a nearly constant level and the gradient is negative at larger radii, that is, galaxies with level-slope (LS) gradients. We also selected galaxies with a nearly uniform oxygen abundance across the whole galaxy, that is, galaxies with level (L) gradients that can be the final evolutionary stage of the two galaxy sequences described above. The radial nitrogen abundance distributions in galaxies with LS oxygen abundance distributions also show breaks at radii smaller than the O/H distribution breaks. The observed behaviour of the oxygen and nitrogen abundances with radius in these galaxies can be explained by the time delay between the nitrogen and oxygen enrichment together with the variation in the star formation history along the radius. These galaxies clearly show the effect of the inside-out disc evolution model. We find that the shape of the radial abundance distribution in a galaxy is not related to its macroscopic characteristics (rotation velocity, stellar mass, isophotal radius, and star formation rate). The correlations between the gradient slopes and macroscopic characteristics of galaxies are weak in the sense that the scatter of the points in each diagram is large. We also examined the properties of the Milky Way in the context of the considered galaxy samples.

Understanding the physical properties of stars, and putting these properties into the context of stellar evolution, is a core challenge in astronomical research. A key visualization in studying stellar evolution is the Hertzsprung-Russell diagram (HRD), organizing data about stellar luminosity and colour into a form that is informative about stellar structure and evolution. However, connecting the HRD with other sources of information, including stellar time series, is an outstanding challenge. Here we present a new method to turn stellar time series into sound. This method encodes physically meaningful features such that auditory comparisons between sonifications of different stars preserve astrophysical differences between them. We present an interactive multimedia version of the HRD that combines both visual and auditory components and that allows exploration of different types of stars both on and off the main sequence through both visual and auditory media.

The recent parameterisation by the GSP-spec module of Gaia/RVS spectra has produced an homogeneous catalogue of about 174,000 AGB stars. Among the 13 chemical elements presented in this catalogue, the abundance of 2 of them (Ce and Nd) have been estimated in most of these AGBs. These 2 species formed by slow n-captures in the interior of low- and intermediate-mass stars, belong to the family of 2nd-peak s-process elements. We defined a working sample of 19,544 AGB stars with high-quality Ce and/or Nd abundances, selected by applying a specific combination of the GSP-spec quality flags. We compared these abundances with the yield production predicted by AGB stars evolutionary models. We found a good correlation between the Ce and Nd abundances, confirming the high quality of the derived abundances and that these species indeed belong to the same s-process family. We also found higher Ce and Nd abundances for more evolved AGB stars of similar metallicity, illustrating the successive mixing episodes enriching the AGB star surface. We then compared the observed Ce and Nd abundances with the FRUITY and Monash AGB yields and found that the higher Ce and Nd abundances cannot be explained by AGB stars of masses higher than 5Msun. In contrast, the yields predicted by both models for AGB stars with an initial mass between ~1.5 and ~2.5Mssun and metallicities between ~-0.5 and ~0.0dex are fully compatible with the observed GSP-spec abundances. This work based on the largest catalogue of high-quality second-peak s-element abundances in O-rich AGB stars allows evolutionary models to be constrained and confirms the fundamental role played by low- and intermediate-mass stars in the enrichment of the Universe in these chemical species.

Recently, the pulsar timing array (PTA) collaborations, including CPTA, EPTA, NANOGrav, and PPTA, announced that they detected a stochastic gravitational wave background spectrum in the nHz band. This may be relevant to the cosmological phase transition suggested by some models. Magnetic monopoles and primordial black holes (PBHs), two unsolved mysteries in the universe, may also have their production related to the cosmological phase transition. Inspired by that, we revisit the model proposed by Stojkovic and Freese, which involves PBHs accretion to solve the cosmological magnetic monopole problem. We further develop it by considering the increase in the mass of the PBHs during accretion and taking the effect of Hawking radiation into account. With these new considerations, we find that solutions to the problem still exist within a certain parameter space. In {addition}, we also generalize the analysis to PBHs with {an} extended distribution in mass. This may be a more interesting scenario because PBHs that have accreted magnetic monopoles might produce observable electromagnetic signals if they are massive enough to survive in the late universe.

The Photometric objects Around Cosmic webs (PAC) approach developed in Xu et al. (2022b) has the advantage of making full use of spectroscopic and deeper photometric surveys. With the merits of PAC, the excess surface density $\bar{n}_2w_{{\rm{p}}}$ of neighboring galaxies can be measured down to stellar mass $10^{10.80}\,M_{\odot}$ around quasars at redshift $0.8<z_{\rm{s}}<1.0$, with the data from the Sloan Digital Sky Survey IV (SDSS-IV) extended Baryon Oscillation Spectroscopic Survey (eBOSS) and the Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys. We find that $\bar{n}_2w_{{\rm{p}}}$ generally increases quite steeply with the decrease of the separation. Using subhalo abundance matching method, we can accurately model the $\bar{n}_2w_{{\rm{p}}}$ both on small and large scales. We show that the steep increase of the $\bar{n}_2w_{{\rm{p}}}$ towards the quasars requires that a large fraction $f_{\mathrm{sate}}=0.29_{-0.06}^{+0.05}$ of quasars should be satellites in massive halos, and find that this fraction measurement is insensitive to the assumptions of our modeling. This high satellite fraction indicates that the subhalos have nearly the same probability to host quasars as the halos for the same (infall) halo mass, and the large scale environment has negligible effect on the quasar activity. We show that even with this high satellite fraction, each massive halo on average does not host more than one satellite quasar due to the sparsity of quasars.

The chemical compositions of stars encode the history of the universe and are thus fundamental for advancing our knowledge of astrophysics and cosmology. However, measurements of elemental abundances ratios, and our interpretations of them, strongly depend on the physical assumptions that dictate the generation of synthetic stellar spectra. Three-dimensional radiation-hydrodynamic (3D RHD) ``box-in-a-star'' simulations of stellar atmospheres offer a more realistic representation of surface convection occurring in late-type stars compared to traditional one-dimensional (1D) hydrostatic models. As evident from a multitude of observational tests, the coupling of 3D RHD models with line-formation in non-local thermodynamic equilibrium (non-LTE) today provides a solid foundation for abundance analysis for many elements. This review describes the ongoing and transformational work to advance the state-of-the-art and replace 1D LTE spectrum synthesis with its 3D non-LTE counterpart. In summary: 1) 3D and non-LTE effects are intricately coupled and consistent modelling thereof is necessary for high-precision abundances, which is currently feasible for individual elements in large surveys. Mean 3D (<3D>) models are not adequate as substitutes. 2) The solar abundance debate is presently dominated by choices and systematic uncertainties that are not specific to 3D non-LTE modelling. 3) 3D non-LTE abundance corrections have a profound impact on our understanding of FGK-type stars, exoplanets, and the nucleosynthetic origins of the elements.

We implement a test of MOND and Verlinde's Emergent Gravity using the galaxy cluster SMACS J0723-7327, which has been recently imaged using the eROSITA X-ray telescope as well as with JWST. We test MOND using two independent methods. The first method involves comparing the dynamical MOND mass and baryonic mass, while the second method entails a comparison of the MOND-estimated temperature with the observed temperature. We then compare the unseen mass predicted by Emergent Gravity with the estimated dark matter mass. We find that MOND is able to explain the mass discrepancy at large radii but not in the central regions. The observed temperature profile is also in slight disagreement with that in the MOND paradigm. Likewise the Emergent Gravity Theory shows a marginal discrepancy in accurately accounting for the dynamical mass in the inner regions. Our results are qualitatively consistent with the earlier tests on other clusters.

For decades, the spectral variations of Beta Pictoris have been modelled as the result of the evaporation of exocomets close to the star, termed falling evaporating bodies (FEBs). Resonant perturbations by a giant planet have been proposed to explain the dynamical origin of these stargrazers. The disk is now known to harbour two giant planets, Beta Pic b and c, orbiting the star at 9.9 au and 2.7 au. While the former almost matches the planet formerly suspected, the discovery of the latter complicates the picture. We first question the stability of the two-planet system. Then we investigate the dynamics of a disk of planetesimals orbiting the star with both planets to check the validity of the FEB generation mechanism. Symplectic N-body simulations are used to determine which regions of the planetesimal disk are dynamically stable. Then we focus on regions where disk particles are able to reach high eccentricities thanks to resonant mechanisms. The first result is that the system is dynamically stable. Both planets may temporarily fall in 7:1 mean motion resonance (MMR). Then, simulations reveal that the whole region extending between ~1.5 au and ~25 au is unstable to planetary perturbations. However, a disk below 1.5 au survives, which appears to constitute an active source of FEBs via high-order MMRs with Beta Pic c. Beta Pic b acts as a distant perturber that helps sustain the whole process. These simulations rule out the preceding FEB generation mechanism model, which placed their origin at around 4-5 au. Conversely, FEBs are likely to originate from a region much further in and related to MMRs with Beta Pic c. That mechanism also appears to last longer, as new planetesimals are able to continuously enter the MMRs and evolve towards the FEB state. Subsequently, the physical nature of the FEBs may differ from that previously thought, and presumably may not be icy.

We have analyzed Chandra and Suzaku observations of the globular cluster Terzan 6, made when the recurrent transient GRS 1747-312 was in quiescence. Our analysis reveals the presence of a second eclipsing, bursting neutron-star low-mass X-ray binary in the central regions of the cluster, in addition to GRS 1747-312. The new source, which we name Terzan 6 X2, is located very close to GRS 1747-312 (~0.7 arcsec away) in the 2021 Chandra images. The detection of a 5.14 ks-long eclipse in the light curve of X2 at a time not predicted by the ephemeris of GRS 1747-312 confirms that it is an unrelated source. Using the Suzaku light curve from 2009, which in addition to a type-I X-ray burst also showed an eclipse-like feature, we constrain the orbital period to be longer than 16.27 h. The 0.5-10 keV luminosities of X2 vary in the range of ~0.24-5.9x10^34 erg/s on time scales of months to years. We have identified a plausible optical counterpart of X2 in HST F606W and F814W images. This star varied by 2.7 mag in V_606 between epochs separated by years. In the cluster color-magnitude diagram, the variable counterpart lies in the blue-straggler region when it was optically bright, about 1.1-1.7 mag above the main-sequence turn-off. From the orbital period-density relation of Roche-lobe filling stars we find the mass-donor radius to be >0.8 Rsun.

X-ray binaries are known to launch powerful accretion disk winds that can have significant impact on the binary systems and their surroundings. To quantify the impact and determine the launching mechanisms of these outflows, we need to measure the wind plasma number density, an important ingredient in the theoretical disk wind models. While X-ray spectroscopy is a crucial tool to understanding the wind properties, such as their velocity and ionization, in nearly all cases, we lack the signal-to-noise to constrain the plasma number density, weakening the constraints on outflow location and mass outflow rate. We present a new approach to determine this number density in the X-ray binary Hercules X-1 by measuring the speed of the wind ionization response to time-variable illuminating continuum. Hercules X-1 is powered by a highly magnetized neutron star, pulsating with a period of 1.24 s. We show that the wind number density in Hercules X-1 is sufficiently high to respond to these pulsations by modeling the ionization response with the time-dependent photoionization model TPHO. We then perform a pulse-resolved analysis of the best-quality XMM-Newton observation of Hercules X-1 and directly detect the wind response, confirming that the wind density is at least $10^{12}$ cm$^{-3}$. Finally, we simulate XRISM observations of Hercules X-1 and show that they will allow us to accurately measure the number density at different locations within the outflow. With XRISM we will rule out $\sim3$ orders of magnitude in density parameter space, constraining the wind mass outflow rate, energetics, and its launching mechanism.

With the onset of the era of gravitational-wave (GW) astronomy, the search for continuous gravitational waves (CGWs), which remain undetected to date, has intensified in more ways than one. Rapidly rotating neutron stars with non-axisymmetrical deformations are the main targets for CGW searches. The extent of this quadrupolar deformation is measured by the maximum ellipticity that can be sustained by the crust of a neutron star and it places an upper limit on the CGW amplitudes emitted by such systems. In this paper, following previous works on this subject, we calculate the maximum ellipticity of a neutron star generated by the Lorentz force exerted on it by the internal magnetic fields. We show that the ellipticity of stars deformed by such a Lorentz force is of the same order of magnitude as previous theoretical and astrophysical constraints. We also consider if this ellipticity can be further enhanced by crustal surface currents. We discover that this is indeed true; surface currents at crustal boundaries are instrumental towards enhancing the ellipticity of magnetized neutron stars.

Visual photometry, the estimation of stellar brightness by eye, continues to provide valuable data even in this highly-instrumented era. However, the eye-brain system functions differently from electronic sensors and its products can be expected to have different characteristics. Here I characterize some aspects of the visual data set by examining ten well-observed variable stars from the AAVSO database. The standard deviation around a best-fit curve ranges from 0.14 to 0.34 magnitude, smaller than most previous estimates. The difference in scatter between stars is significant, but does not correlate with such things as range or quickness of variation, or even with color. Naked-eye variables, which would be expected to be more difficult to observe accurately, in fact show the smallest scatter. The difference between observers (bias) is less important than each observer's internal precision. A given observer's precision is not set but varies from star to star for unknown reasons. I note some results relevant to other citizen science projects.

Stellar evolution theory predicts the existence of He-core remnants of the primary components of intermediate-mass close binaries that lost most of their H/He envelopes due to the mass exchange. They are expected to be observed as (1-7) solar mass hot He-rich stars located in the HRD between sdO/B and WR-stars. Several thousands of such stars are expected to exist in the Galaxy, but none of them have been identified so far. We aim to provide comprehensive predictions of the numbers and fundamental properties of He-stars and their companions in the Galaxy. This is a necessary first step to guide observations, to enable a comparison between evolutionary models and observed populations, and to determine the feedback of He-stars in the Galaxy. We expanded the previously considered space of parameters describing progenitors of He-stars and applied a population synthesis based on a grid of models computed by the code MESA. The estimated number of Galactic binaries hosting (1-7) solar mass He-stars is about 20000; it declines to about 3000 for mass exceeding two solar ones. The decisive factor that defines the number of He-stars is runaway mass loss after Roche lobe overflow by primary components, resulting in formation of common envelopes and merger of components. He-stars are much less numerous than expected, since a fraction of close binaries with primary masses below (5-7) solar ones produce subdwarfs with masses below solar. Overwhelming majority of He-stars reside in binaries with an early-type companions and can be identified neither by the UV excess nor by emission features. The large periods of a significant fraction of binaries hosting stripped stars (exceeding several hundred days) also hamper their discovery. (Abridged).

We have used data from the Outer Galaxy High-Resolution Survey (OGHReS) to refine the velocities, distances, and physical properties of a large sample of 3584 clumps detected in far infrared/submillimetre emission in the HiGAL survey located in the $\ell = 250^\circ-280^\circ$ region of the Galactic plane. Using $^{12}$CO and $^{13}$CO spectra, we have determined reliable velocities to 3412 clumps (95% of the sample). In comparison to the velocities from the HiGAL catalogue, we find good agreement for 80% of the sample (within 5 km/s). Using the higher resolution and sensitivity of OGHReS has allowed us to correct the velocity for 632 clumps and provide velocities for 687 clumps for which no velocity had been previously allocated. The velocities are used with a rotation curve to refine the distances to the clumps and to calculate the clumps' properties using a distance-dependent gas-to-dust ratio. We have determined reliable physical parameters for 3200 outer Galaxy dense clumps (~90% of the HiGAL sources in the region). We find a trend of decreasing luminosity-to-mass ratio with increasing Galactocentric distance, suggesting the star formation efficiency is lower in the outer Galaxy or that it is resulting in more lower mass stars than in the inner Galaxy. We also find a similar surface density for protostellar clumps located in the inner and outer Galaxy, revealing that the surface density requirements for star formation are the same across the Galactic disc.

The nearly continuous stream of miniature comets dominated by the Kreutz sungrazers has been an unexpected bonanza for cometary science initiated by the launch of the Solar and Heliospheric Observatory (SOHO) in 1995. Over the nearly 30 years since the time, no serious attempt has been made to formulate a self-consistent model for the formation and evolution of this stream of Kreutz comets -- the goal of the present two-part investigation. Part I describes historical highlights of the research that has been relevant to the problem of SOHO sungrazers (including the major contributions by Hubbard, Kreutz, and Marsden) and furnishes preliminaries of diagnostic value that are intended to facilitate, and provide critical information for, the work in Part II. Formerly noted issues, such as the high frequency of close pairs in the SOHO database, are proposed to be products of a broader process of swarming, seen in both the nodal longitude and time. I present examples of tight swarms revealed by high arrival rates of the SOHO Kreutz sungrazers, primarily from Population I.

The proposed Laser Interferometer Space Antenna (LISA) mission is tasked with the detection and characterization of gravitational waves from various sources in the universe. This endeavor is challenged by transient displacement and acceleration noise artifacts, commonly called glitches. Uncalibrated glitches impact the interferometric measurements and decrease the signal quality of LISA's time-delay interferometry (TDI) data used for astrophysical data analysis. The paper introduces a novel calibration pipeline that employs a neural network ensemble to detect, characterize, and mitigate transient glitches of diverse morphologies. A convolutional neural network is designed for anomaly detection, accurately identifying and temporally pinpointing anomalies within the TDI time series. Then, a hybrid neural network is developed to differentiate between gravitational wave bursts and glitches, while a long short-term memory (LSTM) network architecture is deployed for glitch estimation. The LSTM network acts as a TDI inverter by processing noisy TDI data to obtain the underlying glitch dynamics. Finally, the inferred noise transient is subtracted from the interferometric measurements, enhancing data integrity and reducing biases in the parameter estimation of astronomical targets. We propose a low-latency solution featuring generalized LSTM networks primed for rapid response data processing and alert service in high-demand scenarios like predicting binary black hole mergers. The research highlights the critical role of machine learning in advancing methodologies for data calibration and astrophysical analysis in LISA.

Dark matter constitutes $26\%$ of the total energy in our universe, but its nature remains elusive. Among the assortment of viable dark matter candidates, particles and fields with masses lighter than $40 \mathrm{eV}$, called ultralight dark matter, stand out as particularly promising thanks to their feasible production mechanisms, consistency with current observations, and diverse and testable predictions. In light of ongoing and forthcoming experimental and observational efforts, it is important to advance the understanding of ultralight dark matter from theoretical and phenomenological perspectives: How does it interact with itself, ordinary matter, and gravity? What are some promising ways to detect it? In this thesis, we aim to explore the dynamics and interaction of ultralight dark matter and other astrophysically accessible hypothetical fields in a relatively model-independent way. Without making specific assumptions about their ultraviolet physics, we first demonstrate a systematic approach for constructing a classical effective field theory for both scalar and vector dark fields and discuss conditions for its validity. Then, we explore the interaction of ultralight dark fields, both gravitational and otherwise, within various contexts such as nontopological solitons, neutron stars, and gravitational waves.

We generalize Integration-By-Parts (IBP) and differential equations methods to de Sitter amplitudes related to inflation. While massive amplitudes in de Sitter spacetime are usually regarded as highly intricate, we find they have remarkably hidden concise structures from the perspective of IBP. We find the irrelevance of IBP relations to propagator-types. This also leads to the factorization of the IBP relations of each vertex integral family corresponding to $\mathrm{d} \tau_i$ integration. Furthermore, with a smart construction of master integrals, the universal formulas for iterative reduction and $\mathrm{d} \log$-form differential equations of arbitrary vertex integral family are presented and proved. These formulas dominate all tree-level de Sitter amplitude and play a kernel role at the loop-level as well.

The intrinsic resolution is the primary limitation on the total energy resolution of LaBr3(Ce) crystal. This intrinsic resolution arises from two effects: fluctuations occurring in the process of energy transfer to luminescent centers within the LaBr3(Ce) crystal and the LaBr3(Ce) crystal's non-proportional luminescence. Presently, experimental measurements regarding the intrinsic resolution of LaBr3(Ce) crystal are scarce, and the underlying physical mechanisms remain incompletely understood. In this paper, we aim to elucidate the concept of intrinsic resolution. We investigated the entire physical process of luminescence following energy deposition in the LaBr3(Ce) crystal, quantifying the various components in the total energy resolution. We conducted a series of experimental measurements and Geant4 simulations, determining the intrinsic resolution of LaBr3(Ce) crystal to 100 keV electrons as 2.12%. The non-proportionality contributes significantly at 1.43%, while fluctuations in the energy transfer process accounted for 0.27%. It is evident that non-proportionality in light output constitutes the primary source of intrinsic resolution. Horizontal and vertical unevenness in light collection contributed 0.25% and 0.07%, respectively. Statistical fluctuations showed the largest impact on the total energy resolution, at 2.86%. The contribution from fluctuations in single-photoelectron events was 0.77%. Furthermore, we reconstructed the photon response using Geant4, and the consistency between the simulated relative light yield and the experimentally measured one confirmed the reliability of the LaBr3(Ce) detector mass model employed in the simulation.

Thermal leptogenesis is a mechanism that explains the observed asymmetry between matter and antimatter in the early universe. In this study, we review the impact of nonextensive Tsallis statistical mechanics on the early universe and study its effect on thermal leptogenesis. The study has found that the use of nonextensive statistical mechanics can affect the production of baryon asymmetry in thermal leptogenesis by modifying the equilibrium abundance of particles, decay, and washout parameters. Also, we show that nonextensive statistical mechanics potentially reduce the required right-handed neutrino mass scale.

We provide a comprehensive analysis of the acceleration of magnetic monopoles in intergalactic magnetic fields. We demonstrate that monopoles with intermediate to low masses can be accelerated to relativistic velocities. This can significantly affect direct and indirect searches for magnetic monopoles. As an example, we show that the Parker bound is relaxed in the presence of intergalactic fields. We also find that a cosmic population of monopoles can produce significant backreaction on the intergalactic fields.

We discuss the gravitational wave (GW) spectra predicted from the electroweak scalegenesis of the Higgs portal type with a large number of dark chiral flavors, which many flavor QCD would underlie and give the dynamical explanation of the negative Higgs portal coupling required to trigger the electroweak symmetry breaking. We employ the linear-sigma model as the low-energy description of dark many flavor QCD and show that the model undergoes ultra-supercooling due to the produced strong first-order thermal phase transition along the (approximately realized) flat direction based on the Gildener-Weinberg mechanism. Passing through evaluation of the bubble nucleation/percolation, we address the reheating and relaxation processes, which are generically non-thermal and nonadiabatic. Parametrizing the reheating epoch in terms of the efolding number, we propose proper formulae for the redshift effects on the GW frequencies and signal spectra. It then turns out that the ultra-supercooling predicted from the Higgs-portal scalegenesis generically yields none of GW signals with the frequencies as low as nano Hz, instead, prefers to give the higher frequency signals, which still keeps the future prospected detection sensitivity, like at LISA, BBO, and DECIGO, etc. We also find that with large flavors in the dark sector, the GW signals are made further smaller and the peak frequencies higher. Characteristic phenomenological consequences related to the multiple chiral scalars include the prediction of dark pions with the mass much less than TeV scale, which is also briefly addressed.