Papers for Wednesday, May 22 2024

The probability that two satellites overlap in space at a specified instant of time is called their instantaneous collision probability. Assuming Gaussian uncertainties and spherical satellites, this probability is the integral of a Gaussian distribution over a sphere. This paper shows how to compute the probability using an established numerical procedure called characteristic function inversion. The collision probability in the short-term encounter scenario is also evaluated with this approach, where the instant at which the probability is computed is the time of closest approach between the objects. Python and R code is provided to evaluate the probability in practice. Overall, the approach has been established for over fifty years, is implemented in existing software, does not rely on analytical approximations, and can be used to evaluate two and three dimensional collision probabilities.

We show that stars in the inner parsec of the Milky Way can be significantly affected by dark matter annihilation, producing population-level effects that are visible in a Hertzsprung-Russell (HR) diagram. We establish the dark HR diagram, where stars lie on a new stable $\textit{dark main sequence}$ with similar luminosities, but lower temperatures, than the standard main sequence. The dark matter density in these stars continuously replenishes, granting these stars immortality and solving multiple stellar anomalies. Upcoming telescopes could detect the dark main sequence, offering a new dark matter discovery avenue.

Crustal quakes of highly magnetized neutron stars can disrupt their magnetospheres, triggering energetic phenomena like X-ray and fast radio bursts (FRBs). Understanding plasma wave dynamics in these extreme environments is vital for predicting energy transport across scales to the radiation length. This study models relativistic plasma wave interaction in magnetar magnetospheres with force-free electrodynamics simulations. For propagation along curved magnetic field lines, we observe the continuous conversion of Alfvén waves (AWs) to fast magnetosonic (FMS) waves. The conversion efficiency can be up to three times higher when counter-propagating AWs interact in the equatorial region. Alfvén waves generate FMS waves of twice their frequency during their first crossing of the magnetosphere. After the initial transient burst of FMS waves, AWs convert to FMS waves periodically, generating variations on timescales of the magnetospheric AW crossing time. This decaying FMS wave tail carries a significant portion (half) of the total energy emitted. Plastic damping of `bouncing' AWs by the magnetar crust has minimal impact on the FMS efficiency. We discuss the implications of the identified wave phenomena for magnetar observations. Outgoing FMS waves can develop electric zones, potential sources of coherent radiation. Long wavelength FMS waves could generate FRBs through reconnection beyond the light cylinder.

Recent observations have positioned the endpoint of the Epoch of Reionisation (EoR) at redshift $z \sim 5.3$. However, observations of the Lyman-$\alpha$ forest have not yet been able to discern whether reionisation occurred slowly and late, with substantial neutral hydrogen persisting at redshift $\sim 6$, or rapidly and earlier, with the apparent late end driven by the fluctuating UV background. Gunn-Peterson (GP) absorption troughs are solid indicators that reionisation is not complete until $z=5.3$, but whether they contain significantly neutral gas has not yet been proven. We aim to answer this question by directly measuring, for the first time, the neutral hydrogen fraction ($x_\mathrm{HI}$) at the end of the EoR ($5 \lesssim z \lesssim 6$) in high-redshift quasars spectra. For high neutral fractions $x_\mathrm{HI}\gtrsim0.1$, GP troughs exhibit damping wing (DW) absorption extending over $1000$ km s$^{-1}$ beyond the troughs. While conclusively detected in Lyman-$\alpha$ emission lines of quasars at $z\geq7$, DWs are challenging to observe in the general Lyman-$\alpha$ forest due to absorption complexities and small-scale stochastic transmission features. We report the first successful identification of the stochastic DW signal adjacent to GP troughs at redshifts $z=5.6$ through careful stacking of the dark gaps in Lyman-$\alpha$ forest. We use the signal to present a measurement of the corresponding global $x_\mathrm{HI}=0.19\pm0.07$ $(_{-0.16}^{+0.11})$ at $1\sigma$ $(2\sigma)$ at $z=5.6$ and a limit $x_\mathrm{HI}<0.44$ at $z=5.9$. The detection of this signal demonstrates the existence of substantially neutral islands near the conclusion of the EoR, unequivocally signaling a late-and-slow reionization scenario.

Recent quasar absorption line observations suggest that reionization may end as late as $z \approx 5.3$. As a means to search for large neutral hydrogen islands at $z<6$, we revisit long dark gaps in the Ly$\beta$ forest in VLT/X-Shooter and Keck/ESI quasar spectra. We stack the Ly$\alpha$ forest corresponding to the edges of these Ly$\beta$ dark gaps and identify a damping wing-like extended absorption profile. The average redshift of the stacked forest is $z=5.8$. By comparing these observations with reionization simulations, we infer that such a damping wing-like feature can be naturally explained if these gaps are at least partially created by neutral islands. Conversely, simulated dark gaps lacking neutral hydrogen struggle to replicate the observed damping wing features. Furthermore, this damping wing-like profile implies that the volume-averaged neutral hydrogen fraction must be $\langle x_{\rm HI} \rangle \geq 6.1 \pm 3.9\%$ at $z = 5.8$. Our results offer robust evidence that reionization extends below $z=6$.

Ground-based observations of `Barbarian' L-type asteroids at 1 to 2.5-$\mu$m indicate that their near-infrared spectra are dominated by the mineral spinel, which has been attributed to a high abundance of calcium-aluminum inclusions (CAIs) -- the first solids to condense out of the protoplanetary disk during the formation of the Solar System. However, the spectral properties of these asteroids from 2.5 to 5-$\mu$m, a wavelength region that covers signatures of hydrated minerals, water, and organics, have not yet been explored. Here, we present 2 to 5-$\mu$m reflectance spectra of five spinel-rich asteroids obtained with the NIRSpec instrument on the James Webb Space Telescope. All five targets exhibit a $\sim$ 2.85-$\mu$m absorption feature with a band depth of 3-6$\%$ that appears correlated in strength with that of the 2-$\mu$m spinel absorption feature. The shape and position of the 2.85-$\mu$m feature are not a good match to the 2.7-$\mu$m feature commonly seen in carbonaceous CM meteorites or C-type asteroids. The closest spectral matches are to the Moon and Vesta, suggesting commonalities in aqueous alteration across silicate bodies, infall of hydrated material, and/or space weathering by solar wind H implantation. Lab spectra of CO/CV chondrites, CAIs, as well as the minerals cronstedtite and spinel, also show a similar feature, providing clues into the origin of the 2.85-$\mu$m feature.

Recent results from baryon acoustic oscillation measurements by the Dark Energy Spectroscopic Instrument (DESI) have found preliminary evidence that dark energy (DE) evolves with time, as parameterized by a $w_0 w_a$ equation of state. In this study, we point out that the DESI-preferred $w_0w_a$ models are recovered when a $w_0w_a$ model is fit to DE produced by baryon conversion in cosmologically coupled black holes (BHs). This recovery does not require any \emph{ad hoc} parameter adjustments; it solely depends on the independently measured cosmic star formation rate density. We discuss our result in the context of the missing baryon problem and the anomalously low sum of neutrino masses preferred by DESI. The global evolution of DE is an orthogonal probe of cosmological coupling, complementing constraints on BH mass growth from elliptical galaxies, stellar binaries, globular clusters, the LIGO-Virgo-KAGRA merging population, and X-ray binaries. A DE density that correlates with star formation is a natural outcome of cosmological coupling in BH populations.

From deep imaging data obtained with the Large Binocular Telescope as part of the Smallest Scale of Hierarchy Survey (SSH), we have discovered low-surface brightness tidal features around NGC 5238 and UGC 8760, two nearby and relatively isolated dwarf galaxies with stellar masses of approximately $10^8 M_\odot$ and $2\times10^7 M_\odot$, respectively. In this study, we present detailed hydrodynamical $N$-body simulations that explain the observed faint substructures as the outcome of interactions between the dwarf galaxies and smaller satellite systems. We show that the asymmetric stellar distribution of NGC 5238 and the low-luminosity substructures observed to the northeast of UGC 8760 can be well attributed to recent interactions with smaller galaxies, each with a stellar mass roughly a few $10^5 M_\odot$, 50 times less massive than their respective hosts. In the simulations, these satellites have stellar and dark-matter masses consistent with the ones predicted by $\Lambda$CDM cosmology and share properties similar to those of local dwarf galaxies with similar stellar masses. The satellite-to-main galaxy mass ratio is approximately 1:10 in both cases. This satellite population aligns closely with predictions from cosmological simulations in terms of the number and mass relative to the host galaxy mass.

Two main mechanisms have classically been proposed for the formation of runaway stars. The binary supernova scenario (BSS) suggests that a massive star in a binary explodes as a supernova, ejecting its companion. The dynamical ejection scenario suggests that a star is ejected through a strong dynamical encounter between multiple stars. We propose a third mechanism for the formation of runaway stars: the sub-cluster ejection scenario (SCES), where an infalling sub-cluster of stars is ejected out of the cluster by a slingshot interaction with the contracting gravitational potential of the assembling cluster. We demonstrate the SCES in a star-by-star simulation of a young massive cluster forming from a $10^6\rm~M_\odot$ gas cloud using the Torch framework. This star cluster forms hierarchically through a sequence of sub-cluster mergers, determined by the initial turbulent, spherical initial conditions of the gas. We find that these mergers drive the formation of runaway stars in our model. Late-forming sub-clusters fall into the central potential, where they are ejected on a slingshot trajectory, forming groups of runaway stars that are distributed highly anisotropically. Runaways formed by the same SCES share similar ages, velocities, and ejection directions. Surveying observations, we identify several SCES candidate groups with anisotropic ejection directions. The SCES is capable of producing runaway binaries: two wide dynamical binaries in infalling sub-clusters were tightened through ejection. This allows for another velocity kick via subsequent BSS, which is a promising avenue for producing hypervelocity stars unbound to the Galaxy. The SCES occurs when sub-cluster formation is resolved. We expect non-spherical initial gas distributions to increase runaway star numbers. The observation of groups of runaway stars formed via SCES thus reveals the assembly history of their natal clusters.

We present new VLT/MUSE observations of the Hubble Frontier Field (HFF) galaxy cluster MACS J1149.5+2223, lensing the well-known supernova "Refsdal" into multiple images, which enabled the first cosmological applications with a strongly lensed supernova. Thanks to these data, targeting a northern region of the cluster and thus complementing our previous MUSE program on the cluster core, we release a new catalog containing 162 secure spectroscopic redshifts. We confirm 22 cluster members, which were previously only photometrically selected, and detect ten additional ones, resulting in a total of 308 secure members, of which 63% are spectroscopically confirmed. We further identify 17 new spectroscopic multiple images belonging to 6 different background sources. By exploiting MUSE data, in combination with the deep HFF images, we develop an improved total mass model of MACS J1149.5+2223. This model includes 308 total mass components for the member galaxies and requires four additional mass profiles, one of which is associated with a cluster galaxy overdensity identified in the North, representing the DM mass distribution on larger scales. The values of the resulting 34 free parameters are optimized based on the observed positions of 106 multiple images from 34 different families, that cover the redshift range between 1.240 and 5.983. Our final model has a multiple image position rms value of 0.39", which is well in agreement with that of other cluster lens models. With this refined mass model, we pave the way towards even better strong-lensing analyses that will exploit the deep and high resolution observations with HST and JWST on a pixel level in the region of the supernova Refsdal host. This will increase the number of observables by around two orders of magnitudes, thus offering us the opportunity of carrying out more precise and accurate cosmographic measurements.

The Astro2020 Decadal Survey recognizes time-domain astronomy as a key science area over the next decade and beyond. With over 30 years of HST data and the potential for 20 years of JWST operations, these flagship observatories offer an unparalleled prospect for a half-century of space-based observations in the time domain. To take best advantage of this opportunity, STScI charged a working group to solicit community input and formulate strategies to maximize the science return in time-domain astronomy from these two platforms. Here, the HST/JWST Long-Term Monitoring Working Group reports on the input we received and presents our recommendations to enhance the scientific return for time-domain astronomy from HST and JWST. We suggest changes in policies to enable and prioritize long-term science programs of high scientific value. As charged, we also develop recommendations based on community input for a JWST Director's Discretionary Time program to observe high-redshift transients.

A large number of candidate binary stars with apparent acceleration on the sky has emerged from analysis of astrometric data collected by the Hipparcos, Tycho-2, and Gaia space missions. Although the apparent acceleration can serve as a relatively reliable indicator of binarity, it provides scarce information about the orbital and physical parameters of the components. With an emphasis on the search for stellar-mass black holes and neutron stars hidden in binary systems, we start a broader effort to characterize the most promising candidates using follow-up ground-based observations. Accurate quantification of orbital and physical parameters of systems with dim or invisible companions requires combination of Hipparcos, Gaia, and precision spectroscopic measurements. In this paper, we review the necessary steps in this implementation and describe the improved Hipparcos-Gaia sample of long-term astrometric accelerations which includes correction of sky-correlated systematic errors using the vector spherical decomposition method. As an example, we study one Hipparcos star with a large acceleration, HIP 44842, where the companion is revealed to be a normal main sequence star.

Astronomical time series often have non-uniform sampling in time, or irregular cadences, with long gaps separating clusters of observations. Some of these data sets are also explicitly non-Gaussian with respect to the expected model fit, or the simple mean. The standard Lomb-Scargle periodogram is based on the least squares solution for a set of test periods and, therefore, is easily corrupted by a subset of statistical outliers or an intrinsically non-Gaussian population. It can produce completely misleading results for heavy-tailed distribution of residuals. We propose a robust 1-norm periodogram technique, which is based on the principles of robust statistical estimation. This technique can be implemented in weighted or unweighted options. The method is described in detail and compared with the classical least squares periodogram on a set of astrometric VLBI measurements of the ICRF quasar IERS B0642+449. It is uniformly applied to a collection of 259 ICRF3 quasars each with more than 200 epoch VLBI measurements, resulting in a list of 49 objects with quasi-periodic position changes above the $3\sigma$ level, which warrant further investigation.

The study of binary stars in the Galactic halo provides crucial insights into the dynamical history and formation processes of the Milky Way. In this work, we aim to investigate the binary fraction in a sample of accreted and in-situ halo stars, focusing on short-period binaries. Utilising data from Gaia DR3, we analysed the radial velocity (RV) uncertainty $\sigma_{\mathrm{RV}}$ distribution of a sample of main-sequence stars. We used a novel Bayesian framework to model the dependence in $\sigma_{\mathrm{RV}}$ of single and binary systems allowing us to estimate binary fractions $F$ in a sample of bright ($G_{\mathrm{RVS}}$ < 12) Gaia sources. We selected the samples of in-situ and accreted halo stars based on estimating the 6D phase space information and affiliating the stars to the different samples on an action-angle vs energy ($L_{\mathrm{z}}-E$) diagram. Our results indicate a higher, though not significant, binary fraction in accreted stars compared to the in-situ halo sample. We further explore binary fractions using cuts in $E$ and $L_z$ and find a higher binary fraction in both high-energy and prograde orbits that might be explained by differences in metallicity. By cross-matching our Gaia sample with APOGEE DR17 catalogue, we confirm the results of previous studies on higher binary fractions in metal-poor stars and find the fractions of accreted and in-situ halo stars consistent with this trend. Our finding provides new insights into binary stars' formation processes and dynamical evolution in the primordial Milky Way Galaxy and its accreted dwarf Galaxies.

While most galaxies live in group environments where they undergo an accelerated evolution, the characteristics of their circumgalactic medium (CGM) remain uncertain. We present an analysis of the CGM of two galaxy groups in different stages of interaction: (G1) a close pair of galaxies ($z=0.043$) separated by 87 kpc that do not show signs of interactions and (G2) four merging galaxies ($z=0.098$) separated by 10 kpc. We present spatially-resolved Keck/KCWI galaxy observations and HST/COS quasar spectra (G1 at 48 kpc and G2 at 100 kpc away) to quantify both the resolved galaxy and CGM properties in these two different group environments. G1 contains two typical star-forming galaxies with no evidence of strong outflows. G2 contains two star-forming, one post-starburst and one quiescent galaxy. Both groups have a range of CGM detected metal lines (HI, CII, SiII, SiIII, NV and OVI). Despite G2 being twice as far from the quasar, G2 has $\log (N(HI)/{\rm cm}^{-2})=17.33$, compared to $\log (N(HI)/{\rm cm}^{-2})=16.43$ for G1. We find that the CGM of the merging galaxies (G2) is more kinematically complex, is in a higher ionisation state, spans a wider range of metallicities and column densities, has smaller cloud sizes, and is inconsistent with the simple superposition model that seems to match well with G1. We conclude that the complexity of the CGM in merging galaxies surpasses that of not strongly interacting galaxies, suggesting that mergers play a significant role in shaping the intricate structure of the CGM.

Blue Compact Galaxies (BCGs), also known as \HII\ galaxies, are dwarf, star-forming objects with relatively simple dynamics, which allows for the investigation of star formation mechanisms in a cleaner manner compared to late-type objects. In this study, we have examined various characteristics of the interstellar medium, in connection with the kinematics and dynamics of ionized gas, in Tol 1004-296 and Tol 0957-278. These two objects were observed using the SOAR Integral Field Spectrometer (SIFS) attached to the Southern Observatory for Astrophysical Research (SOAR). Both galaxies were observed with two gratings: one with medium resolution for monochromatic and abundance maps, and another with high resolution for kinematics and profile analysis. Additionally, we conducted an analysis on the velocity and velocity dispersion maps using intensity-velocity dispersion (I - $\sigma$) and velocity-velocity dispersion (Vr - $\sigma$) diagrams. Neither object exhibits a rotation pattern, and only Tol 1004-296 shows a velocity gradient between the two principal knots. However, the study reveals the significant role played by velocity dispersion in the star formation process. Specifically, we identified a relationship between monochromatic intensity, metallicity, and velocity dispersion, where high emission corresponds to low metallicity and low velocity dispersion. Tol 1004-296, in particular, exhibits a distinctive linear high velocity dispersion pattern between the two main knots, suggesting that both star formation sites are pushing the gas in opposite directions.

Stellar spin down is a critical yet poorly understood component of stellar evolution. In particular, results from the Kepler Mission imply that mature age, solar-type stars have inefficient magnetic braking, resulting in a stalled spin down rate. However, a large number of precise asteroseismic ages are needed for mature ($\geq$ 3Gyr) stars in order to probe the regime where traditional and stalled spin-down models differ. In this paper, we present a new asteroseismic benchmark star for gyrochronology discovered using reprocessed Kepler short cadence data. KIC 11029516 (Papayu) is a bright ($K_{p}$ = 9.6 mag) solar-type star with well-measured rotation period (21.1$\pm$0.8 days) from spot modulation using 4 years of Kepler long cadence data. We combine asteroseismology and spectroscopy to obtain $T_{eff}=5888\pm100$ K, $\rm{[Fe/H]} = 0.30 \pm 0.06\,$ dex, $M = 1.24 \pm 0.05 M_{\odot}$, $R = 1.34 \pm 0.02 R_{\odot}$ and age of 4.0 $\pm$ 0.4 Gyr, making Papayu one of the most similar stars to the Sun in terms of temperature and radius with an asteroseismic age and a rotation period measured from spot modulation. We find that Papayu sits at the transition of where traditional and weakened spin-down models diverge. A comparison with stars of similar zero-age main-sequence temperatures supports previous findings that weakened spin-down models are required to explain the ages and rotation periods of old solar-type stars.

Multi-wavelength polarimetry and radio observations of Swift J1727.8-1613 at the beginning of its recent 2023 outburst suggested the presence of a bright compact jet aligned in the north-south direction, which could not be confirmed without high angular resolution images. Using the Very Long Baseline Array and the Long Baseline Array, we imaged Swift J1727.8-1613, during the hard/hard-intermediate state, revealing a bright core and a large, two-sided, asymmetrical, resolved jet. The jet extends in the north-south direction, at a position angle of $-0.60\pm0.07°$ East of North. At 8.4 GHz, the entire resolved jet structure is $\sim110 (d/2.7\,\text{kpc})/\sin i$ AU long, with the southern approaching jet extending $\sim80 (d/2.7\,\text{kpc})/\sin i$ AU from the core, where $d$ is the distance to the source and $i$ is the inclination of the jet axis to the line of sight. These images reveal the most resolved continuous X-ray binary jet, and possibly the most physically extended continuous X-ray binary jet ever observed. Based on the brightness ratio of the approaching and receding jets, we put a lower limit on the intrinsic jet speed of $\beta\geq0.27$ and an upper limit on the jet inclination of $i\leq74°$. In our first observation we also detected a rapidly fading discrete jet knot $66.89\pm0.04$ mas south of the core, with a proper motion of $0.66\pm0.05$ mas hour$^{-1}$, which we interpret as the result of a downstream internal shock or a jet-ISM interaction, as opposed to a transient relativistic jet launched at the beginning of the outburst.

We describe the evolution of low mass planets in a dispersing protoplanetary disk around a Solar mass star. The disk model is based on the results of Yu, Hansen & Hasegawa (2023), which describes a region of the inner disk where the direction of the migration torque is outwards due to the diffusion of the stellar magnetic field into the disk and the resultant gradual increase in surface density outwards. We demonstrate that the magnetospheric rebound phase in such a disk leads to diverging orbits for double and triple planet systems, and the disruption of a high fraction of the initial resonant chains. We present simulations of three planet systems with masses based on the observed triple planet systems observed by the Kepler satellite within the context of this model. The final distribution of nearest neighbour period ratios provides an excellent fit to the observations, provided that the initial resonant configurations are compact. The occurrence rate of planets as a function of orbital period also provides a good match to the observations, for final orbital periods P<20 days. These results suggest that the period and period ratio distributions of low mass planets are primarily set in place during the disk dispersal epoch, and may not require significant dynamical evolution thereafter.

We describe the space observatory architecture and mission design of the SALTUS mission, a NASA Astrophysics Probe Explorer concept. SALTUS will address key far-infrared science using a 14-m diameter <45 K primary reflector (M1) and will provide unprecedented levels of spectral sensitivity for planet, solar system, and galactic evolution studies, and cosmic origins. Drawing from Northrop Grumman's extensive NASA mission heritage, the observatory flight system is based on the LEOStar-3 spacecraft platform to carry the SALTUS Payload. The Payload is comprised of the inflation control system (ICS), Sunshield Module (SM), Cold Corrector Module (CCM), Warm Instrument Electronics Module, and Primary Reflector Module (PRM). The 14-m M1 is an off-axis inflatable membrane radiatively cooled by a two-layer sunshield (~1,000 m2 per layer). The CCM corrects for residual aberration from M1 and delivers a focused beam to two instruments - High Resolution Receiver (HiRX) and SAFARI-Lite. The CCM and PRM reside atop a truss-based composite deck which also provides a platform for the attitude control system. The 5-year mission lifetime is driven by a two-consumable architecture: the propellant system and the ICS. The Core Interface Module (CIM), a multi-faceted composite truss structure, provides a load path with high stiffness, mechanical attachment, and thermal separation between the Payload and spacecraft. The SM attaches outside the CIM with its aft end integrating directly to the bus. The spacecraft maintains an attitude off M1's boresight with respect to the Sun line to facilitate the <45 K thermal environment. SALTUS will reside in a Sun-Earth halo L2 orbit with a maximum Earth slant range of 1.8 million km thereby reducing orbit transfer delta-v. The instantaneous field of regard provides two continuous 20-deg viewing zones around the ecliptic poles resulting in full sky coverage in six months.

During the first half of the fourth observing run (O4a) of the International Gravitational Wave Network (IGWN), the Zwicky Transient Facility (ZTF) conducted a systematic search for kilonova (KN) counterparts to binary neutron star (BNS) and neutron star-black hole (NSBH) merger candidates. Here, we present a comprehensive study of the five high-significance (FAR < 1 per year) BNS and NSBH candidates in O4a. Our follow-up campaigns relied on both target-of-opportunity observations (ToO) and re-weighting of the nominal survey schedule to maximize coverage. We describe the toolkit we have been developing, Fritz, an instance of SkyPortal, instrumental in coordinating and managing our telescope scheduling, candidate vetting, and follow-up observations through a user-friendly interface. ZTF covered a total of 2841 deg$^2$ within the skymaps of the high-significance GW events, reaching a median depth of g~20.2 mag. We circulated 15 candidates, but found no viable KN counterpart to any of the GW events. Based on the ZTF non-detections of the high-significance events in O4a, we used a Bayesian approach, nimbus, to quantify the posterior probability of KN model parameters that are consistent with our non-detections. Our analysis favors KNe with initial absolute magnitude fainter than -16 mag. The joint posterior probability of a GW170817-like KN associated with all our O4a follow-ups was 64%. Additionally, we use a survey simulation software, simsurvey, to determine that our combined filtered efficiency to detect a GW170817-like KN is 36%, when considering the 5 confirmed astrophysical events in O3 (1 BNS and 4 NSBH), along with our O4a follow-ups. Following Kasliwal et al. (2020), we derived joint constraints on the underlying KN luminosity function based on our O3 and O4a follow-ups, determining that no more than 76% of KNe fading at 1 mag/day can peak at a magnitude brighter than -17.5 mag.

Planetary systems in mean motion resonances hold a special place among the planetary population. They allow us to study planet formation in great detail as dissipative processes are thought to have played an important role in their existence. Additionally, planetary masses in bright resonant systems may be independently measured both by radial velocities (RVs) and transit timing variations (TTVs). In principle, they also allow us to quickly determine the inclination of all planets in the system, as for the system to be stable, they are likely all in coplanar orbits. To describe the full dynamical state of the system, we also need the stellar obliquity that provides the orbital alignment of a planet with respect to the spin of their host star and can be measured thanks to the Rossiter-McLaughlin effect. It was recently discovered that HD 110067 harbours a system of six sub-Neptunes in resonant chain orbits. We here analyze an ESPRESSO high-resolution spectroscopic time series of HD 110067 during the transit of planet c. We find the orbit of HD 110067 c to be well aligned with sky projected obliquity $\lambda =6^{+24}_{-26}$ deg. This result is indicative that the current architecture of the system has been reached through convergent migration without any major disruptive events. Finally, we report transit-timing variation in this system as we find a significant offset of 19 $\pm$ 4 minutes in the center of the transit compared to the published ephemeris.

H$\alpha$ emission is a clear indicator of circumstellar activity in Be stars, historically employed to assess the classical Be star (CBe) population in young open clusters (YOCs). The YOC NGC330 in the Small Magellanic Cloud exhibits a large known fraction of {CBe} stars and was selected for a pilot study to establish a comprehensive methodology for identifying H$\alpha$ emitters in the Magellanic Clouds, encompassing the entire B-type spectral range. Using the SOAR Adaptative Module Imager (SAMI), we investigated the stellar population of NGC330 using multi-band BVRI+H$\alpha$ imaging. We identified H$\alpha$ emitters within the entire V-band range covered by SAMI/SOAR observations ($V\lesssim22$), comprising the complete B-type stellar population and offering a unique opportunity to explore the Be phenomenon across all spectral sub-classes. The stellar radial distribution shows a clear bimodal pattern between the most massive (B5 or earlier) and the lower-mass main-sequence objects (later than B6) within the cluster. The former is concentrated towards the cluster center (showing a dispersion of $\sigma=4.26\pm0.20$ pc), whereas the latter extends across larger radii ($\sigma=10.83\pm0.65$ pc), indicating mass stratification within NGC330. The total fraction of emitters is $4.4\pm0.5\%$, notably smaller than previous estimates from flux- or seeing-limited observations. However, a higher fraction of H$\alpha$ emitters is observed among higher-mass stars ($32.8\pm3.4\%$) than within lower-mass ($4.4\pm0.9\%$). Consequently, the putative CBe population exhibits distinct dynamical characteristics compared to the bulk of the stellar population in NGC330. These findings highlight the significance of the current observations in providing a complete picture of the CBe population in NGC330.

Magnetic reconnection is a fundamental process for releasing magnetic energy in space physics and astrophysics. At present, the usual way to investigate the reconnection process is through analytical studies or first-principles numerical simulations. This paper is the first to understand the turbulent magnetic reconnection process by exploring the nature of magnetic turbulence. From the perspective of radio synchrotron polarization statistics, we study how to recover the properties of the turbulent magnetic field by considering the line of sight along different directions of the reconnection layer. We find that polarization intensity statistics can reveal the spectral properties of reconnection turbulence. This work opens up a new way of understanding turbulent magnetic reconnection.

We perform the first magnetic field strength survey of Class I and Flat Spectrum (FS) sources using $K$-band observations with iSHELL. We obtained new observations of 42 Class I and FS sources and additionally included 10 sources from the archive. We detect photospheric lines in 44 of the sources, in addition to Br$\gamma$, H$_2$, and CO emission in several objects. We model the photospheric absorption lines of 32 Class I and FS sources and measure their magnetic field strengths, $K$-band temperatures, gravities, projected rotational velocities, and infrared veiling values. We put the physical properties of Class I and FS sources in context by comparing them to the values derived for a sample of Class II sources. We find that a) the average magnetic field strength of Class I and FS sources $\langle B \rangle=2.0\pm0.15$ kG is consistent with the average magnetic field strength of Class II sources $\langle B \rangle=1.8\pm0.15$ kG, and b) the average gravity of Class I and FS objects $\log{g}=3.43\pm0.07$ is lower than the average gravity of Class II sources $\log{g}=3.75\pm0.04$, although there is significant overlap between both gravity distributions. Furthermore, using stellar evolutionary models, we deduce that Class I and FS sources have a median age of $\sim$0.6 Myr, and are, as a group, younger than the Class II stars with a median age of $\sim$3 Myr. Our results confirm that Class I and FS sources host strong magnetic fields on their photospheres. Thus, it is likely that these sources accrete disk material through a magnetosphere similar to the more evolved T Tauri stars.

With great advance of ground-based extensive air shower array, such as LHAASO and HAWC, many very high energy (VHE) gamma-ray sources have been discovered and are been monitored regardless of the day and the night. Hence, the Sun and Moon would have some compact on the observation of gamma-ray sources, which have not been taken into account in previous analysis. In this paper, the influence of the Sun and Moon on the observation of very high energy gamma-ray sources when they are near the line of sight of the Sun or Moon is estimated. The tracks of all the known VHE sources are scanned and several VHE sources are found to be very close to the line of sight of the Sun or Moon during some period. The absorption of very high energy gamma-ray by sunlight is estimated with detailed method and some usefully conclusions are achieved. The main influence is the block of the Sun and Moon on gamma-ray and their shadow on the cosmic ray background. The influence is investigated considering the detector angular resolution and some strategy on data analysis are proposed to avoid the underestimation of the gamma-ray emission.

The sound horizon is a key theoretical prediction of the cosmological model that depends on the speed of sound and the rate of expansion in the early universe, before matter and radiation decoupled. The standard ruler for low redshift calibration of baryon acoustic oscillations (BAOs) is a direct measurement that would exist even if the standard cosmological model and the standard assumptions of early physics did not. We propose a new model-independent method to calibrate sound horizon $r^h_s$ (relative standard ruler) by using the latest observations of SNe Ia and transversal BAO measurements. The final result reports $r_s^{h}=107.10^{+1.36}_{-1.32}$ $Mpc/h$ in the framework of the Pantheon dataset. This result changes to $r_s^{h}=105.63^{+1.33}_{-1.31}$ $Mpc/h$ when uses Pantheon+ dataset. Note that even without an estimate of dimensionless Hubble constant $h$, the combination of BAO and SNe Ia datasets already constrain the low-redshift standard ruler scale $r_s^{h}$ at the $\sim1.26\%$ level. More importantly, it is interesting to find that most of the $r_s^{h}$ obtained at high redshifts have a larger value (9 out of 15 results are larger than the result obtained by combining all BAOs). This finding may give us a better understanding of the discordance between the data sets or Hubble tension or reveal new physics beyond the standard model.

We present a sample of 22 massive galaxies with stellar masses $>10^{10} M_{\odot}$ at $3<z<4$ with deep H and K-band high resolution spectra (R=3500-3000) from Keck/MOSFIRE and VLT/KMOS near-infrared spectrographs. We find a large fraction have strong [OIII]5007 and H$\beta$ emission lines with large line widths ($\sigma$ 100 -- 450 km/s). We measure the sizes of our galaxies from Hubble Space Telescope images and consider the potential kinematic scaling relations of our sample; and rule out an explanation for these broad lines in terms of galaxy-wide kinematics. Based on consideration of the [OIII]5007 $/$ H$\beta$ flux ratios, their location in the Mass--Excitation diagram, and the derived bolometric luminosities, we conclude that Active Galactic Nuclei (AGN) and their Narrow Line Regions most likely give rise to this emission. At redshifts $3<z<4$, we find significantly high AGN fractions in massive galaxies, ranging from 60--70\% for the mass range $10<\log(M_{\star}/M_{\odot})<11$, with a lower limit 30\% for all galaxies within that redshift range when we apply our most stringent AGN criteria. We also find a considerably lower AGN fraction in massive quiescent galaxies, ranging from 20-30\%. These fractions of AGN point to the period between $3<z<4$ being a time of heightened activity for the development of supermassive black holes in the massive end of the galaxy population and provide evidence for their role in the emergence of the first massive quenched galaxies at this epoch.

We present photometric and spectroscopic observations and analysis of the type IIb supernova (SN) SN 2019tua, which exhibits multiple bumps in its declining light curves between 40 and 65 days after discovery. SN 2019tua shows a time to peak of about 25 days similar to other type IIb SNe. Our observations indicate a decrease in its brightness of about 1 magnitude in the 60 days after the peak. At about days 50, and 60, its multiband light curves exhibit bumpy behavior. The complex luminosity evolution of SN 2019tua could not be well modeled with a single currently popular energy source model, e.g., radioactive decay of $^{56}$Ni, magnetar, interaction between the ejecta and a circumstellar shell. Even though the magnetar model has a smaller \( \chi^2 / \text{dof} \) value, the complex changes in SN 2019tua's brightness suggest that more than one physical process might be involved. We propose a hybrid CSM interaction plus $^{56}$Ni model to explain the bolometric light curve (LC) of SN 2019tua. The fitting results show that the ejecta mass $M_{\rm ej} \approx 2.4~M_\odot$, the total CSM mass $M_{\rm CSM} \approx 1.0~M_\odot$, and the $^{56}$Ni mass $M_{\rm Ni} \approx 0.4~M_\odot$. The total kinetic energy of the ejecta is $E_k\approx 0.5 \times 10^{51}\rm~erg$. Pre-existing multiple shells suggest that the progenitor of SN 2019tua experienced mass ejections within approximately $\sim6 - 44$ years prior to the explosion.

In this paper, we describe the wide-field spectroscopic survey telescope (WST) project. WST is a 12-metre wide-field spectroscopic survey telescope with simultaneous operation of a large field-of-view (3 sq. degree), high-multiplex (20,000) multi-object spectrograph (MOS), with both a low and high-resolution modes, and a giant 3x3 arcmin2 integral field spectrograph (IFS). In scientific capability, these specifications place WST far ahead of existing and planned facilities. In only 5 years of operation, the MOS would target 250 million galaxies and 25 million stars at low spectral resolution, plus 2 million stars at high resolution. Without need for pre-imaged targets, the IFS would deliver 4 billion spectra offering many serendipitous discoveries. Given the current investment in deep imaging surveys and noting the diagnostic power of spectroscopy, WST will fill a crucial gap in astronomical capability and work in synergy with future ground and space-based facilities. We show how it can address outstanding scientific questions in the areas of cosmology; galaxy assembly, evolution, and enrichment, including our own Milky Way; the origin of stars and planets; and time domain and multi-messenger astrophysics. WST's uniquely rich dataset may yield unforeseen discoveries in many of these areas. The telescope and instruments are designed as an integrated system and will mostly use existing technology, with the aim to minimise the carbon footprint and environmental impact. We will propose WST as the next European Southern Observatory (ESO) project after completion of the 39-metre ELT.

This study presented the first light curve analysis of the OP Boo and V0511 Cam binary stars, which was conducted in the frame of the Binary Systems of South and North (BSN) Project. Photometric ground-based observations were conducted with standard filters at two observatories in the Czech Republic. We computed a new ephemeris for each of the systems using our extracted times of minima, TESS data, and additional literature. Linear fits for O-C diagrams of both systems were considered using the Markov Chain Monte Carlo (MCMC) method. The light curves were analyzed using the Wilson-Devinney (WD) binary code combined with the Monte Carlo (MC) simulation. The light curve solutions of both target systems required a cold starspot. The absolute parameters of the systems were calculated by using a P-M parameter relationship. The positions of the systems were also depicted on the Hertzsprung-Russell (HR), P-L, logMtot-logJ0, and T-M diagrams. The second component in both systems is determined to be a more massive and hotter star. Therefore, it can be concluded that both systems are W-type contact binary systems.

In-situ measurements of the solar wind, a turbulent and anisotropic plasma flow originating at the Sun, are mostly carried out by single spacecraft, resulting in one-dimensional time series. The conversion of these measurements to the spatial frame of the plasma is a great challenge, but required for direct comparison of the measurements with MHD turbulence theories. Here we present a toolkit, based on the synthetic modeling of solar wind fluctuations as two-dimensional noise maps with adjustable spectral and power anisotropy, that can help with the temporal-spatial conversion of real data. Specifically, by following the spacecraft trajectory through a noise map (relative velocity and angle relative to some mean magnetic field) with properties tuned to mimic those of the solar wind, the likelihood that the temporal data fluctuations represent parallel or perpendicular fluctuations in the plasma frame can be quantified by correlating structure functions of the noise map. Synthetic temporal data can also be generated, which can provide a testing ground for analysis applied to the solar wind data. We demonstrate this tool by investigating Parker Solar Probe's E7 trajectory and data, and showcase several possible ways in which it can be used. We find that whether temporal variations in the spacecraft frame come from parallel or perpendicular variations in the plasma frame strongly depends on the spectral and power anisotropy of the measured wind. Data analysis assisted by such underlying synthetic models as presented here could open up new ways to interpret measurements in the future, specifically in the more reliable determination of plasma frame quantities from temporal measurements.

The metallicity distribution function (MDF) of the Galactic bulge features a multi-peak shape, with a metal-poor peak at [Fe/H]=-0.3 dex and a metal-rich peak at [Fe/H]=+0.3 dex. This bimodality is also seen in [alpha/Fe] versus [Fe/H] ratios, indicating different stellar populations in the bulge. We aim to replicate the observed MDF by proposing a scenario where the metal-poor bulge stars formed in situ during an intense star formation burst, while the metal-rich stars formed during a second burst and/or were accreted from the inner Galactic disk due to a growing bar. We used a chemical evolution model that tracks various chemical species with detailed nucleosynthesis, focusing on Fe production from both Type Ia supernovae and massive stars, including rotating massive stars with varying velocities. Our model also accounts for gas infall, outflow, and the effect of stellar migration. Results are compared to 13,000 stars from the SDSS/APOGEE survey within 3.5 kpc of the Galactic center. Our model successfully reproduces the double-peak shape of the bulge MDF and the alpha-element abundance trends relative to Fe by assuming (i) a multi-burst star formation history with a 250 Myr quenching of the first burst and (ii) stellar migration from the inner disk due to a growing bar. We estimate that about 40% of the bulge-bar's stellar mass originates from the inner disk. Nucleosynthesis models that assume either no rotation for massive stars or a rotational velocity distribution favoring slow rotation at high metallicities best match the observed MDF and [alpha/Fe] and [Ce/Fe] versus [Fe/H] abundance patterns.

V892 Tau is a young binary star surrounded by a circumbinary disc which show hints of interaction with the low-mass nearby star V892 Tau NE. The goal of this paper is to constrain the orbit of V892 Tau NE and to determine the resulting circumbinary disc dynamics. We present new ALMA observations of the V892 Tau circumbinary disc at a twice higher angular and spectral resolution. We model the data with V892 Tau as a triple system and perform a grid of hydrodynamical simulations testing several orbits of the companion. The simulation outputs are then post-processed to build synthetic maps that we compare to the observations. The 12CO emission of the disc shows clear non-Keplerian features such as spiral arms. When comparing the data with our synthetic observations, we interpret these features as ongoing interactions with the companion. Our simulations indicate that an eccentricity of 0.5 of the companion is needed to reproduce the observed disc extent and that a mutual inclination of approximately 60° with the inner binary reproduces the measured disc tilt. In order to explain most of the features of the circumbinary disc, we propose that V892 Tau NE follows a misaligned eccentric orbit, with an eccentricity between 0.2 and 0.5 and a mutual inclination between 30° and 60°. Such a misaligned companion suggests the disc is oscillating and precessing with time, stabilising in an intermediate plane with a non-zero mutual inclination with the inner binary. Given that orbital configuration, we show that the stability of future planets is compromised in the second half of the disc once the gas has dissipated.

We report high-frequency pulsations in WR135 from short cadence optical photometric and spectroscopic time series surveys. The harmonics up to $6^{th}$ order are detected from the integrated photometric flux variation while the comparatively weaker $8^{th}$ harmonic is detected from the varying strengths of the least blended emission lines. We investigate the atmospheric stratification of the stellar winds of WR135 using a radiative transfer modeling code, CMFGEN, and find the physical conditions that can support the propagation of such pulsations. From our study, we find that the sub-sonic layers of the atmosphere are close to the Eddington limit and are launched by the Fe-opacity. While the outer optically thin super-sonic winds ($\tau_{ross}$=0.1-0.01) are driven by the He II and C IV opacities. The stratified winds above the sonic point undergo velocity perturbation that can lead to clumps. We find that the optically thin supersonic winds ($\tau_{ross}$=0.1-0.01) contain dense smaller clumps (f=0.2-0.3) that oscillate under the higher-order harmonics of the pulsation. These clumps grow larger (f=0.1), dominate the outer stellar winds ($\tau_{ross}$=0.01-0.001), and oscillate under the lower-order harmonics.

Partially ionised plasmas (PIP) constitute an essential ingredient of our plasma universe. Historically, the physical effects associated with partial ionisation were considered in astrophysical topics such as the interstellar medium, molecular clouds, accretion disks and, later on, in solar physics. PIP can be found in layers of the Sun's atmosphere as well as in solar structures embedded within it. As a consequence, the dynamical behaviour of these layers and structures is influenced by the different physical effects introduced by partial ionisation. Here, rather than considering an exhaustive discussion of partially ionised effects in the different layers and structures of the solar atmosphere, we focus on solar prominences. The reason is that they represent a paradigmatic case of a partially ionised solar plasma, confined and insulated by the magnetic field, constituting an ideal environment to study the effects induced by partial ionisation. We present the current knowledge about the effects of partial ionisation in the global stability, mass cycle and dynamics of solar prominences. We revise the identified observational signatures of partial ionisation in prominences. We conclude with prospects for PIP research in prominences, proposing the path for advancing in the prominence modelling and theory and using new and upcoming instrumentation.

Cosmic very small dust grains (VSGs) contain 100 to 10,000 atoms, making it a mesoscopic system with specific thermal and optical characteristics due to the finite number of atoms within each grain. This paper focuses on graphite VSGs which contain free electrons. The energy level statistics devised by Kubo (1962, J.Phys.Soc.Jpn., 17, 975-986) were used for the first time to understand the thermal properties of free electrons in graphite VSGs. We showed that the shape irregularity of the grains allows graphite VSGs to absorb or emit photons at sub-millimeter wavelengths or longer; otherwise, the frequency is limited to above a few THz. Additionally, we considered the decrease in Debye temperature due to the surface effect. VSGs have an extremely small volume, resulting in limited thermal energy storage, especially at low temperatures. Since a VSG is able to emit a photon with energy smaller than its internal energy, this determines the maximum frequency of the emitted photon. We developed a Monte-Carlo simulation code to track the thermal history of a dust grain, considering the stochastic heating from the absorption of ambient photons and radiative cooling. This approach was applied to the interstellar environment to compute the spectral energy distributions from the interstellar graphite dust grains. The results showed that graphite VSGs emit not only the mid-infrared excess emission, but also a surplus emission from sub-millimeter to millimeter wavelengths.

Recent James Webb Space Telescope (JWST) data analyses have shown that massive red galaxies existed at redshifts $z>6$, a discovery that is difficult to understand in the context of standard cosmology ($\Lambda $CDM). Here we analyze these observations more deeply by fitting a stellar population model to the optical and near-infrared photometric data. These fits include a main stellar population in addition to a residual younger population and with the same extinction for both (a lower extinction for the younger population is unphysical). Extra stellar populations or the inclusion of an AGN component do not significantly improve the fits. These galaxies are being viewed at very high redshifts, with an average $\langle z\rangle \approx 8.2$, when the $\Lambda$CDM Universe was only $\approx 600$ Myr old. This result conflicts with the inferred ages of these galaxies, however, which were on average between 0.9 and 2.4 Gyr old within 95% CL. Given the sequence of star formation and galaxy assembly in the standard model, these galaxies should instead be even younger than 290 Myr on average, for which our analysis assigns a probability of only $<3\times 10^{-4}$ ($\gtrsim 3.6\sigma $ tension). This outcome may indicate the need to consider non-standard cosmologies. Nevertheless, our conclusions result from several approximations in stellar astrophysics and extinction, so they should be taken with a grain of salt. Further research is necessary to corroborate the possible existence of galaxies older than the $\Lambda $CDM universe at their observed redshifts.

It has been consensus that star-disk systems accrete most of their mass and angular momentum during the collapse of a prestellar core, such that the rotational direction of a system is equivalent to the net rotation of the core. Recent results, however, indicate that stars experience post-collapse or late infall, during which the star and its disk is refreshed with material from the protostellar environment through accretion streamers. Apart from adding mass to the star-disk system, infall potentially supplies a substantial amount of angular momentum as the infalling material is initially not bound to the collapsing prestellar core. We investigate the orientation of infall on star-disk systems by analyzing the properties of accreting tracer particles in 3D magnetohydrodynamical simulations of a molecular cloud that is (4 pc)$^3$ in volume. In contrast to the traditional picture, where the rotational axis is inherited from the collapse of a coherent pre-stellar core, the orientation of star-disk systems can change substantially during the accretion process. In agreement with previous results that show larger contributions of late infall for increasing stellar masses, infall is more likely to lead to a prolonged change in orientation for stars of higher final mass. On average, brown dwarfs and very low mass stars are more likely to form and accrete all of their mass as part of a multiple system, while stars with final masses above a few 0.1 M$_{\odot}$ are more likely to accrete part of their mass as single stars. Finally, we find an overall trend: the post-collapse accretion phase is more anisotropic than the early collapse phase. This result is consistent with a scenario, where mass accretion from infall occurs via infalling streamers along a preferred direction, while the initial collapse is less anisotropic albeit the fact that material is funneled through accretion channels.

Context. As a new growing field, exocartography aims to map the surface features of exoplanets that are beyond the resolution of traditional observing techniques. While photometric approaches have been discussed extensively, polarimetry has received less attention despite its promising prospects. Aims. We demonstrate that the limb polarization of an exoplanetary atmosphere offers valuable insights into its cloud cover distribution. Specifically, we determine an upper limit for the polarimetric precision, which is required to extract information about the latitudinal cloud cover of temperate Jovian planets for scenarios of observations with and without host stars. Methods. To compute the scattered stellar radiation of an exoplanetary atmosphere and to study the polarization at various planetary phase angles, we used the three-dimensional Monte Carlo radiative transfer code POLARIS. Results. When the planetary signal can be measured separately from the stellar radiation, information about the latitudinal cloud cover for polar cap models is accessible at polarimetric sensitivities of $0.1$ %. In contrast, a precision of about $10^{-3}$ ppm is required when the stellar flux is included to gain this information.

The exploration of outflows in protobinary systems presents a challenging yet crucial endeavour, offering valuable insights into the dynamic interplay between protostars and their evolution. In this study, we examine the morphology and dynamics of jets and outflows within the IRAS\,4A protobinary system. This analysis is based on ALMA observations of SiO(5--4), H$_2$CO(3$_{0,3}$--2$_{0,3}$), and HDCO(4$_{1,4}$--3$_{1,3}$) with a spatial resolution of $\sim$150\,au. Leveraging an astrochemical approach involving the use of diverse tracers beyond traditional ones has enabled the identification of novel features and a comprehensive understanding of the broader outflow dynamics. Our analysis reveals the presence of two jets in the redshifted emission, emanating from IRAS\,4A1 and IRAS\,4A2, respectively. Furthermore, we identify four distinct outflows in the region for the first time, with each protostar, 4A1 and 4A2, contributing to two of them. We characterise the morphology and orientation of each outflow, challenging previous suggestions of bends in their trajectories. The outflow cavities of IRAS\,4A1 exhibit extensions of 10$''$ and 13$''$ with position angles (PA) of 0$^{\circ}$ and -12$^{\circ}$, respectively, while those of IRAS\,4A2 are more extended, spanning 18$''$ and 25$''$ with PAs of 29$^{\circ}$ and 26$^{\circ}$. We propose that the misalignment of the cavities is due to a jet precession in each protostar, a notion supported by the observation that the more extended cavities of the same source exhibit lower velocities, indicating they may stem from older ejection events.

The architectures of extrasolar planetary systems often deviate considerably from the ``standard" model for planet formation, which is largely based on our own Solar System. In particular, gas giants on close orbits are not predicted by planet formation theory and so some process(es) are thought to move the planets closer to their host stars. Recent research has suggested that Hot Jupiter host stars display a different phase space compared to stars that do not host Hot Jupiters. This has been attributed to these stars forming in star-forming regions of high stellar density, where dynamical interactions with passing stars have perturbed the planets. We test this hypothesis by quantifying the phase space of planet-hosting stars in dynamical N-body simulations of star-forming regions. We find that stars that retain their planets have a higher phase space than non-hosts, regardless of their initial physical density. This is because an imprint of the kinematic substructure from the regions birth is retained, as these stars have experienced fewer and less disruptive encounters than stars whose planets have been liberated and become free-floating. However, host stars whose planets remain bound but have had their orbits significantly altered by dynamical encounters are also primarily found in high phase space regimes. We therefore corroborate other research in this area which has suggested the high phase space of Hot Jupiter host stars is not caused by dynamical encounters or stellar clustering, but rather reflects an age bias in that these stars are (kinematically) younger than other exoplanet host stars.

Studying the sun's outer atmosphere is challenging due to its complex magnetic fields impacting solar activities. Magnetohydrodynamics (MHD) simulations help model these interactions but are extremely time-consuming (usually on a scale of days). Our research applies the Fourier Neural Operator (FNO) to accelerate the coronal magnetic field modeling, specifically, the Bifrost MHD model. We apply Tensorized FNO (TFNO) to generate solutions from partial differential equations (PDEs) over a 3D domain efficiently. TFNO's performance is compared with other deep learning methods, highlighting its accuracy and scalability. Physics analysis confirms that TFNO is reliable and capable of accelerating MHD simulations with high precision. This advancement improves efficiency in data handling, enhances predictive capabilities, and provides a better understanding of magnetic topologies.

The A-type metallic-line (Am) stars are typically considered to be non-magnetic or possessing very weak sub-G magnetic fields. This view has been repeatedly challenged in the literature, most commonly for the bright hot Am star o Peg. Several studies claimed to detect 1-2 kG field of unknown topology in this object, possibly indicating a new process of magnetic field generation in intermediate-mass stars. In this study, we revisit the evidence of a strong magnetic field in o Peg using new high-resolution spectropolarimetric observations and advanced spectral fitting techniques. The mean magnetic field strength in o Peg is estimated from the high-precision CRIRES+ measurement of near-infrared sulphur lines. This observation is modelled with a polarised radiative transfer code, including treatment of the departures from local thermodynamic equilibrium. In addition, the least-squares deconvolution multi-line technique is employed to derive longitudinal field measurements from archival optical spectropolarimetric observations of this star. Our analysis of the near-infrared S I lines reveals no evidence of Zeeman broadening, ruling out magnetic field with a strength exceeding 260 G. This null result is compatible with the relative intensification of Fe II lines in the optical spectrum taking into account blending and uncertain atomic parameters of the relevant diagnostic transitions. Longitudinal field measurements at three different nights also yield null results with a precision of 2 G. This study refutes the claims of kG-strength dipolar or tangled magnetic field in o Peg. This star is effectively non-magnetic, with the surface magnetic field characteristics no different from those of other Am stars.

The Small Magellanic Cloud (SMC) shows a large variation in ultraviolet (UV) dust extinction curves, ranging from Milky Way-like (MW) to significantly steeper curves with no detectable 2175 A bump. This result is based on a sample of only nine sightlines. From HST/STIS and IUE spectra of OB stars, we have measured UV extinction curves along 32 SMC sightlines where eight of these curves were published previously. We find 16 sightlines with steep extinction with no detectable 2175 A bump, four sightlines with MW-like extinction with a detectable 2175 A bump, two sightlines with fairly flat UV extinction and weak/absent 2175 A bumps, and 10 sightlines with unreliable curves due to low SMC dust columns. Our expanded sample shows that the sightlines with and without the 2175 A bump are located throughout the SMC and not limited to specific regions. The average extinction curve of the 16 bumpless sightlines is very similar to the previous average based on four sightlines. We find no correlation between dust column and the strength of the 2175 A bump. We test the hypothesis that the 2175 A bump is due to the same dust grains that are responsible for the mid-infrared carbonaceous (PAH) emission features and find they are correlated, confirming recent work in the MW. Overall, the slope of the UV extinction increases as the amplitudes of the 2175 A bump and far-UV curvature decrease. Finally, the UV slope is correlated with $N(HI)/A(V)$ and the 2175 A bump and nonlinear far-UV rise amplitudes are anti-correlated with $N(HI)/A(V)$.

We present one high-resolution and a time series of 561 low-resolution follow-up spectroscopic observations of SZ Lyn. It is a high-amplitude Delta Scuti-type pulsating star in a binary system. The photometric observations reveal the existence of radial and non-radial oscillation modes in SZ Lyn. In spectroscopy, the variation of equivalent width of the line profiles reflects the temperature variations. The equivalent widths of the Balmer lines, H-alpha, H-hbeta, and H-gamma were measured over the pulsation cycle of SZ Lyn using time sequence spectra. Hence, the temperature profile of SZ Lyn was derived using the curve of growth analysis. Furthermore, the stellar parameters were determined through the best fit analysis of observed and synthetic high-resolution spectral lines. The best fit determines a model of Teff=6750 K, log(g)=3.5 dex, and vrot=10 km/s for solar abundance.

The SALTUS Probe mission will provide a powerful far-infrared (far-IR) pointed space observatory to explore our cosmic origins and the possibility of life elsewhere. The observatory employs an innovative deployable 14-m aperture, with a sunshield that will radiatively cool the off-axis primary to <45K. This cooled primary reflector works in tandem with cryogenic coherent and incoherent instruments that span the 34 to 660 micron far-IR range at both high and moderate spectral resolutions.

The SRG/eROSITA All-Sky Survey (eRASS) allows for the creation of a complete sample of X-ray dim isolated neutron stars (XDINSs), which will significantly facilitate the study of their population properties, evolution, and connection to other families of isolated neutron stars (INSs). In this work, we conduct a systematic search for XDINSs on the western Galactic hemisphere and discuss the resulting candidate sample. Consistently with the properties of the known XDINSs, we selected all eRASS sources possessing a soft X-ray spectral distribution and that are unlikely to be associated with optical or infrared sources. Our selection criteria allowed us to recover all known XDINSs and previously proposed candidates. In addition, we put forward 33 new candidate members for dedicated follow-up identification campaigns. We found the resulting candidate sample to be about 30-50% complete, mainly due to source confusion and the stringent cross-matching criteria adopted. The candidates of the sample presented here can be divided into two groups: 13 soft and 20 somewhat hard X-ray emitters. Interestingly, the thermal nature, spatial distribution, lack of known counterparts, and absence of significant flux variability of the candidates in the first group agree well with the properties of other confirmed thermally emitting INSs. For the candidates in the second group, the current observational data do not allow one to discern between rotation-powered or recycled pulsars, cataclysmic variables, or quiescent neutron stars in binary systems or even to rule out an extragalactic nature. On the basis of population synthesis and the estimated source completeness of the search, we expect that between one and three new XDINSs are among the already singled-out list of XDINS candidates - a long-sought increase in the proposed number of members of this elusive class of X-ray emitters.

Nearby associations of stars which are coeval are important benchmark laboratories because they provide robust measurements of stellar ages. The study of such coeval groups makes it possible to better understand star formation by studying the initial mass function, the binary fraction or the circumstellar disks of stars, to determine how the initially dense populations of young stars gradually disperse to form the field population, and to shed light on how the properties of stars, exoplanets and substellar objects evolve with distinct snapshots along their lifetime. The advent of large-scale missions such as Gaia is reshaping our understanding or stellar kinematics in the Solar neighborhood and beyond, and offers the opportunity to detect a large number of loose, coeval stellar associations for the first time, which evaded prior detection because of their low density or the faintness of their members. In parallel, advances in detection and characterization of exoplanets and substellar objects are starting to unveil the detailed properties of extrasolar atmospheres, as well as population-level distributions in fundamental exoplanet properties such as radii, masses, and orbital parameters. Accurate ages are still sparsely available to interpret the evolution of both exoplanets and substellar objects, and both fields are now ripe for detailed age investigations because we are starting to uncover ever-closer low-density associations that previously escaped detection, as well as exoplanets and ever lower-mass members of more distant open clusters and star-forming regions. In this paper, we review some recent advances in the identification and characterization of nearby associations, the methods by which stellar ages are measured, and some of the direct applications of the study of young associations such as the emergent field of isolated planetary-mass objects.

We present an alternative model of unusual type-IIP SN 2018gj. Despite the short plateau and early gamma-rays escape seeming to favor low-mass ejecta, our hydrodynamic model requires a large ejected mass (about 23 Msun). The high ejecta velocity, we find from hydrogen lines in early spectra, is among crucial constraints on the hydrodynamic model. We recover the wind density that rules out a notable contribution of the circumstellar interaction to the bolometric luminosity. The early radioactive gamma-rays escape is found to be due to the high velocity of Ni-56, whereas the asymmetry of the H-alpha emission is attributed to the asymmetry of the Ni-56 ejecta. The available sample of type-IIP supernovae studied hydrodynamically in a uniform way indicates that the asymmetry of the Ni-56 ejecta is probably their intrinsic property. Hydrogen lines in the early spectra of SN 2018gi and SN 2020jfo are found to imply a clumpy structure of the outer ejecta. With two already known similar cases of SN 2008in and SN 2012A we speculate that the clumpiness of the outer ejecta is inherent to type-IIP supernovae related to the red supergiant explosion.

Broad H$\alpha$ and H$\beta$ emission lines (FWHM > 1,000 km s$^{-1}$) are incredibly efficient tracers of the high-velocity clouds encircling Active Galactic Nuclei (AGN). As a result, we search for these broad line AGN in the Sloan Digital Sky Survey's Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) catalog. We identify 301 broad-line H$\alpha$ galaxies and 801 broad-line H$\beta$ galaxies in the catalog. In total, we detect 1,042 unique broad-line galaxies with luminosities between 10$^{37}$ - 10$^{43}$ erg s$^{-1}$ and inferred supermassive black hole masses between 10$^{5}$ - 10$^{10}$ $M_{\odot}$; 60 feature both broad H$\alpha$ and broad H$\beta$ emission. We also determine that the broad line region radius ranges between 0.01 - 46 light days, with a median radius of 0.1 light days (0.02 pc) for our broad H$\beta$ sample. In addition, we find that both samples feature a higher fraction of galaxy mergers (44% for the broad H$\alpha$ sample and 43% for the broad H$\beta$ sample), compared to the full MaNGA galaxy sample (26%), which suggests that merger-driven fueling is strongly active in our sample.

We show that it is possible to observe the Hawking radiation emitted by small black holes assumed to form in catastrophic astrophysical events such as black hole mergers. Gamma ray bursts in the TeV range are unique footprints of these asteroid-mass black hole morsels ejected during the merger. The time delay of the gamma ray bursts from the gravitational wave event is correlated to the mass distribution of the morsels. The integrated mass of the morsels allowed by the unaccounted merger mass leads to a Hawking induced radiation in photons that is above the sensitivity of atmospheric Cherenkov telescopes such as HESS, LHAASO and HAWC.

The analyses of the next generation cosmological surveys demand an accurate, efficient, and differentiable method for simulating the universe and its observables across cosmological volumes. We present Hamiltonian ray tracing (HRT) -- the first post-Born (accounting for lens-lens coupling and without relying on the Born approximation), three-dimensional (without assuming the thin-lens approximation), and on-the-fly (applicable to any structure formation simulations) ray tracing algorithm based on the Hamiltonian formalism. HRT performs symplectic integration of the photon geodesics in a weak gravitational field, and can integrate tightly with any gravity solver, enabling co-evolution of matter particles and light rays with minimal additional computations. We implement HRT in the particle-mesh library \texttt{pmwd}, leveraging hardware accelerators such as GPUs and automatic differentiation capabilities based on \texttt{JAX}. When tested on a point-mass lens, HRT achieves sub-percent accuracy in deflection angles above the resolution limit across both weak and moderately strong lensing regimes. We also test HRT in cosmological simulations on the convergence maps and their power spectra.

Recent $\gamma$-ray and neutrino observations seem to favor the consideration of non-uniform diffusion of cosmic rays (CRs) throughout the Galaxy. In this study, we investigate the consequences of spatially-dependent inhomogeneous propagation of CRs on the fluxes of secondary CRs and antiprotons detected at Earth. A comparison is made among different scenarios in search of potential features that may guide us toward favoring one over another in the near future. We also examine both the influence of inhomogeneous propagation in the production of secondary CRs from interactions with the gas, and the effects of this scenario on the local fluxes of antiprotons and light antinuclei produced as final products of dark matter annihilation. Our results indicate that the consideration of an inhomogeneous diffusion model could improve the compatibility of the predicted local antiproton flux with that of B, Be and Li, assuming only secondary origin of these particles. In addition, our model predicts a slightly harder local antiproton spectrum, making it more compatible with the high energy measurements of AMS-02. Finally, no significant changes are expected in the predicted local flux of antiprotons and antinuclei produced from dark matter among the different considered propagation scenarios.

We present observations of the $z\sim5.7$ Lyman-break galaxy HZ10 with the JWST/NIRSpec IFU in high and low spectral resolution (G395H, $R\sim2700$ and PRISM, $R\sim100$, respectively), as part of the GA-NIFS program. By spatially resolving the source, we find evidence for three spatially and spectrally distinct regions of line emission along with one region of strong continuum emission, all within a projected distance of $<10$kpc. The R2700 data features strong detections in H$\beta$, [OIII]$\lambda\lambda4959{,}5007$, [NII]$\lambda\lambda6548{,}6584$, H$\alpha$, and [SII]$\lambda\lambda6716{,}6731$. The R100 data additionally contains a strong detection of the Ly$\alpha$ break, rest-UV continuum, and [OII]$\lambda\lambda3726{,}3729$. None of the detected lines present strong evidence for AGN excitation from line diagnostic diagrams, and no high-ionisation lines are detected. Using the detected lines, we constrain the electron density $\left( \rm \log_{10}\left( n_e / cm^{-3}\right)\sim2.5-3.3\right)$ and metallicity ($\sim0.5-0.7$ solar) in each component. Spaxel-by-spaxel fits of each cube reveal a strong east-west velocity gradient and significant line asymmetries (indicating tidal features or outflows). The western component features a very red UV slope ($\beta_{UV}\sim-1$) and significant H$\alpha$ emission, suggesting an evolved population and active star formation. From a comparison to high resolution [CII]$158\mu$m imaging obtained with the Atacama Large Millimetre/submillimetre Array (ALMA), we find that the continuum emitter is associated with a gas-poor stellar population. Altogether, these data suggest that HZ10 represents an ongoing merger, with a complex distribution of stars, gas, and dust $<1$Gyr after the Big Bang.

We advocate for a new paradigm of cosmological likelihood-based inference, leveraging recent developments in machine learning and its underlying technology, to accelerate Bayesian inference in high-dimensional settings. Specifically, we combine (i) emulation, where a machine learning model is trained to mimic cosmological observables, e.g. CosmoPower-JAX; (ii) differentiable and probabilistic programming, e.g. JAX and NumPyro, respectively; (iii) scalable Markov chain Monte Carlo (MCMC) sampling techniques that exploit gradients, e.g. Hamiltonian Monte Carlo; and (iv) decoupled and scalable Bayesian model selection techniques that compute the Bayesian evidence purely from posterior samples, e.g. the learned harmonic mean implemented in harmonic. This paradigm allows us to carry out a complete Bayesian analysis, including both parameter estimation and model selection, in a fraction of the time of traditional approaches. First, we demonstrate the application of this paradigm on a simulated cosmic shear analysis for a Stage IV survey in 37- and 39-dimensional parameter spaces, comparing $\Lambda$CDM and a dynamical dark energy model ($w_0w_a$CDM). We recover posterior contours and evidence estimates that are in excellent agreement with those computed by the traditional nested sampling approach while reducing the computational cost from 8 months on 48 CPU cores to 2 days on 12 GPUs. Second, we consider a joint analysis between three simulated next-generation surveys, each performing a 3x2pt analysis, resulting in 157- and 159-dimensional parameter spaces. Standard nested sampling techniques are simply not feasible in this high-dimensional setting, requiring a projected 12 years of compute time on 48 CPU cores; on the other hand, the proposed approach only requires 8 days of compute time on 24 GPUs. All packages used in our analyses are publicly available.

Efficient algorithms are being developed to search for strong gravitational lens systems owing to increasing large imaging surveys. Neural networks have been successfully used to discover galaxy-scale lens systems in imaging surveys such as the Kilo Degree Survey, Hyper-Suprime Cam (HSC) Survey and Dark Energy Survey over the last few years. Thus, it has become imperative to understand how some of these networks compare, their strengths and the role of the training datasets as most of the networks make use of supervised learning algorithms. In this work, we present the first-of-its-kind systematic comparison and benchmarking of networks from four teams that have analysed the HSC Survey data. Each team has designed their training samples and developed neural networks independently but coordinated apriori in reserving specific datasets strictly for test purposes. The test sample consists of mock lenses, real (candidate) lenses and real non-lenses gathered from various sources to benchmark and characterise the performance of each of the network. While each team's network performed much better on their own constructed test samples compared to those from others, all networks performed comparable on the test sample with real (candidate) lenses and non-lenses. We also investigate the impact of swapping the training samples amongst the teams while retaining the same network architecture. We find that this resulted in improved performance for some networks. These results have direct implications on measures to be taken for lens searches with upcoming imaging surveys such as the Rubin-Legacy Survey of Space and Time, Roman and Euclid.

Ultra-relativistic jets are believed to play important role in producing prompt emission and afterglow of Gamma-Ray Burst (GRB), but the nature of the jet is poorly known owing to the lacking of decisive features observed in the prompt emission. A series of bright, narrow and temporally evolving MeV emission line detected in the brightest-of-all-time GRB 221009A provide a chance to probe GRB jet physics. The evolution of the central energy of the line with power-law index $-1$ is naturally explained by high-latitude curvature effect. Under the assumption that the line emission is generated in the prompt emission by $e^\pm$ pair production, cooling and annihilation in the jet, we can strictly constrain jet physics with observed line emission properties. We find the radius of the emission region is $r\sim10^{16}$cm. The narrow line width of $10\%$ implies that pairs cool fast down to non-relativistic state within a time of tenth of the dynamical time. This requires a magnetic-field energy density much larger than the prompt gamma-ray energy density in the jet, implying a magnetic field dominated jet. The temporal behavior of line flux suggests some angle dependence of line emission. We also discuss the difficulties of other scenarios to interpret the observed emission line.

The definition of thermodynamic entropy is dependent on one's assignment of physical microstates to observed macrostates. As a result, low entropy in the distant past could be equivalently explained by selection of a particular observer. In this paper, I make the case that because we observe a low-entropy past everywhere even as we look further and further away, anthropic selection over observers does not explain the non-equilibrium state of the observed cosmos. Under a uniform prior over possible world states, the probability of a non-equilibrium past, given our local observations, decreases to zero as the size of the world tends toward infinity. This claim is not dependent on choice of observer, unless the amount of information used to encode the observer's coarse-graining perception function scales linearly with the size of the world. As a result, for anthropic selection to choose a world like the one we live in, the initial state of a universe with size $N$ must be low-information, having Kolmogorov complexity that does not scale with $N$.

Repulsive short-range interactions can induce p-wave attraction between fermions in dense matter and lead to Cooper pairing at the Fermi surface. We investigate this phenomenon, well-known as the Kohn-Luttinger effect in condensed matter physics, in dense matter with strong short-range repulsive interactions. We find that repulsive interactions required to stabilize massive neutron stars can induce p-wave pairing in neutron and quark matter. When massive vector bosons mediate the interaction between fermions, the induced interaction favors Cooper pairing in the 3P2 channel. For the typical strength of the interaction favored by massive neutron stars, the associated pairing gaps in neutrons can be in the range of 10 keV to 10 MeV. Strong and attractive spin-orbit and tensor forces between neutrons can result in repulsive induced interactions that greatly suppress the 3P2 pairing gap in neutron matter. In quark matter, the induced interaction is too small to result in pairing gaps of phenomenological relevance.

We show that a rotating axion field that makes a transition from a matter-like equation of state to a kination-like equation of state around the epoch of recombination can significantly ameliorate the Hubble tension, i.e., the discrepancy between the determinations of the present-day expansion rate $H_0$ from observations of the cosmic microwave background on one hand and Type Ia supernovae on the other. We consider a specific, UV-complete model of such a rotating axion and find that it can relax the Hubble tension without exacerbating tensions in determinations of other cosmological parameters, in particular the amplitude of matter fluctuations $S_8$. We subsequently demonstrate how this rotating axion model can also generate the baryon asymmetry of our universe, by introducing a coupling of the axion field to right-handed neutrinos. This baryogenesis model predicts heavy neutral leptons that are most naturally within reach of future lepton colliders, but in finely-tuned regions of parameter space may also be accessible at the high-luminosity LHC and the beam dump experiment SHiP.

We show that dark matter with certain minimal properties can convert the majority of baryons in galaxies to black holes over hundred trillion year timescales. We argue that this has implications for cosmologies which propose that new universes are created in black hole interiors. We focus on the paradigm of cosmological natural selection, which connects black hole production to a universe's likelihood for existing. Further, we propose that the universe's timescale for entropy production could be dynamically linked to black hole production in a naturally selected universe. Our universe would fit this scenario for models of particle dark matter that convert helium white dwarfs to black holes in around a hundred trillion years, where the dominant source of entropy in our universe are the helium white dwarfs' stellar progenitors, which cease forming and burning also in around a hundred trillion years. Much of this dark matter could be discovered at ongoing experiments.

After black holes collide, the remnant settles to a stationary state by emitting gravitational waves. Once non-linearities subside, these ringdown waves are dominated by exponentially-damped sinusoids, or quasinormal modes. We develop a general method using perturbative spectral expansions to calculate the quasinormal-mode frequencies and damping times in a wide class of modified gravity theories for black holes with any subextremal spin. We apply this method to scalar-Gauss-Bonnet gravity to show its accuracy, thus enabling robust ringdown tests with gravitational wave data.

Dark photon dark matter emerges as a compelling candidate for ultralight bosonic dark matter, detectable through resonant conversion into photons within a plasma environment. This study employs in-situ measurements from the Parker Solar Probe (PSP), the first spacecraft to venture into the solar corona, to probe for DPDM signatures. The PSP in-situ measurements go beyond the traditional radio window, spanning frequencies between about 10 kHz and 20 MHz, a challenging range inaccessible to Earth-based radio astronomy. Additionally, the proximity of PSP to the resonant conversion location enhances the signal flux, providing a distinct advantage over ground-based observations. As a result, the PSP data establishes the most stringent constraints on the kinetic mixing parameter $\epsilon$ for DPDM frequencies between 70 kHz and 20 MHz, with values of $\epsilon \lesssim 10^{-14}-10^{-13}$. Investigating the data from STEREO satellites resulted in weaker constraints compared to those obtained from PSP. By utilizing state-of-the-art solar observations from space, we have surpassed the cosmic microwave background limits established in the early universe.

Stationary, asymptotically flat, black hole solutions of the vacuum field equations of General Relativity belong to the Kerr family. But how does one approach this state, dynamically? Linearized fluctuations decay at late times, at fixed spatial position, as a Price power law for generic initial conditions. However, little attention was paid to forced and nonlinear spacetimes, where matter and nonlinearities play a role. We uncover a new, source-driven tail governing waves generated by pointlike matter and nonlinearities, which can dominate over Price's decay.

In order to investigate the potential observational signals of different regularization ambiguities in loop quantum cosmological models, we systematically compute and compare the primordial scalar power spectra and the resulting angular power spectra in the standard loop quantum cosmology (LQC) and its Thiemann regularized versions -- modified LQC-I/II (mLQC-I/II), using both the dressed metric and the hybrid approaches. All three loop quantum cosmological models yield a non-singular bounce with a post-bounce physics that converges rapidly in a few Planck seconds. Using Starobinsky potential and the initial conditions for the background dynamics chosen to yield the same inflationary e-foldings, which are fixed to be $65$ in all three LQC models, we require that all three models result in the same scale-invariant regime for the primordial power spectrum with a relative difference of less than one percent. This permits us to explore the differences resulting from the deep Planck regime in the angular power spectrum. For the adiabatic states, our results demonstrate that the angular power spectrum predicted by the hybrid approach has a smaller deviation from the angular power spectrum predicted by the standard $\Lambda$CDM cosmological model at large angles in comparison with the dressed metric approach for all three models. The angular power spectrum predicted by mLQC-I in both the hybrid and the dressed metric approaches shows the smallest deviation from the one predicted by the standard $\Lambda$CDM cosmological model at large angular scales, except for the case of fourth order adiabatic initial states in the hybrid approach. On the contrary, mLQC-II results in the largest deviations for the amplitude of the angular power spectrum at large angles and is most disfavored.

A novel method for finding the eigenvalues of a Sturm-Liouville problem is developed. Following the minimalist approach the problem is transformed to a single first-order differential equation with appropriate boundary conditions. Although the resulting equation is nonlinear, its form allows to find the general solution by adding a second part to a particular solution. This splitting of the general solution in two parts involves the Schwarzian derivative, hence the name of the approach. The eigenvalues that correspond to acceptable solutions asymptotically can be found by requiring the second part to correct the diverging behavior of the particular solution. The method can be applied to many different areas of physics, such as the Schrödinger equation in quantum mechanics and stability problems in fluid dynamics. Examples are presented.

The origin of the ultra high energy cosmic rays via annihilation of heavy stable, fermions "f", of the cosmological dark matter (DM) is studied. The particles in question are supposed to be created by the scalaron decays in $R^2$ modified gravity. Novel part of our approach is the assumption that the mass of these carriers of DM is slightly below than a half of the scalaron mass. In such a case the phase space volume becomes tiny. It leads to sufficiently low probability of "f" production, so their average cosmological energy density could be equal to the observed energy density of dark matter. Several regions of the universe, where the annihilation could take place, are studied. They include the whole universe under assumption of homogeneous energy density, the high density DM clump in the galactic centre, the cloud of DM in the Galaxy with realistic density distribution, and high density clusters of DM in the Galaxy. Possible resonance annihilation of $f \bar f$ into energetic light particle is considered. We have shown that the proposed scenario can successfully explain the origin of the ultrahigh energy flux of cosmic rays where the canonical astrophysical mechanisms are not operative.

Motivated by the old idea of using the moon as a resonant gravitational-wave (GW) detector, as well as the recent updates in modeling the lunar response to GWs, } we re-evaluate the feasibility of using a network of lunar seismometers to constrain the stochastic GW background (SGWB). In particular, using the updated model of the lunar response, we derive the pattern functions for the two polarizations of GW. With these pattern functions, we further calculate the overlap reduction functions for a network of lunar seismometers, where we have relaxed the conventional assumption that lunar seismometers are perfectly leveled to measure only the vertical acceleration. We apply our calculation to two future lunar projects, namely, Chang'e and the Lunar Gravitational-Wave Antenna (LGWA). We find that the two projects could constrain the SGWB to a level of $\Omega_{\text{GW}}^{\text{Chang'e}} < 79$ and $\Omega_{\text{GW}}^{\text{LGWA}} < 6.7 \times 10^{-11}$, respectively. These results are better than the constraints placed previously on the SGWB in the mid-frequency band (around $10^{-3}- 10~\text{Hz}$) by various types of experiments.

Calculations are performed for electron collision with the methylene molecular ion CH$_2^+$ in its bent equilibrium geometry, with the goal to obtain cross sections for electron impact excitation and dissociation. The polyatomic version of the UK molecular R-matrix codes was used to perform an initial configuration-interaction calculation on the doublet and quartet states of the CH$_2^+$ ion. Subsequently, scattering calculations are performed to obtain electron impact electronic excitation and dissociation cross sections and, additionally, the bound states of the CH$_2$ molecule and Feshbach resonances in the $e$-CH$_2^+$ system.