Papers for Monday, Jan 01 2024

The tidal deformability and the radius of neutron stars are observables, which have been used to constrain the neutron star equation of state and explore the composition in neutron stars. We investigated the radius and tidal deformability of dark matter admixed neutron stars (DANSs) by utilizing the two-fluid TOV equations. Assuming that the dark matter modeled as ideal fermi gas or self-interacting bosons, for a series of DANSs at a fixed mass, it is shown that there exists the DANSs with smaller normal matter radii but larger tidal deformabilities. This negative correlation does not exist in the normal neutron stars.In other words, if the observation finds that the neutron stars with a fixed mass exists such a situation, that is, having a smaller observed radius but a larger tidal deformability, it will indicate the existence of dark matter in neutron stars.In addition, the relevant neutron star observations can also be used to constrain the dark matter parameters.

The Astrophysics Source Code Library (ASCL) is a free online registry for source codes of interest to astronomers, astrophysicists, and planetary scientists. It lists, and in some cases houses, software that has been used in research appearing in or submitted to peer-reviewed publications. As of December 2023, it has over 3300 software entries and is indexed by NASA's Astrophysics Data System (ADS) and Clarivate's Web of Science. In 2020, NASA created the Exoplanet Modeling and Analysis Center (EMAC). Housed at the Goddard Space Flight Center, EMAC serves, in part, as a catalog and repository for exoplanet research resources. EMAC has 240 entries (as of December 2023), 78% of which are for downloadable software. This oral presentation covered the collaborative work the ASCL, EMAC, and ADS are doing to increase the discoverability and citability of EMAC's software entries and to strengthen the ASCL's ability to serve the planetary science community. It also introduced two new projects, Virtual Astronomy Software Talks (VAST) and Exoplanet Virtual Astronomy Software Talks (exoVAST), that provide additional opportunities for discoverability of EMAC software resources.

Galactic centers are very dense and dynamically active environments, often harboring a nuclear star cluster and supermassive black hole at their cores. Binaries in these environments are subject to strong tidal fields that can efficiently torque its orbit, exciting near unity eccentricities that ultimately lead to their merger. In turn, the frequent close interactions due to passing stars impulsively perturb the orbit of the binary, generally softening their orbit until their evaporation, thus potentially hindering the role of the tidal fields to drive these mergers. In this work, we study the evolution of compact object binaries in the galactic center and their merger rates, focusing for the first time on the combined effect of the cluster's tidal field and flyby interactions. We find a significant synergy between both evolution processes, where merger rates increase by a factor of ~10-30 compared with models in which only flybys or tidal fields are taken into account. This synergy is mainly a consequence of the persistent tides-driven eccentricity excitation that is enhanced by the gradual diffusion of z-component of the angular momentum driven by flybys. The merger efficiency peaks when the diffusion rate is ~10-100 times slower than the torquing due to the tidal field. Added to this synergy, we also find that the gradual softening of the binary can lift the relativistic quenching of initially tight binaries, otherwise unable to reach extreme eccentricities, and thus expanding the available phase-space for mergers. Cumulatively, we conclude that despite the gradual softening of binaries due to stellar flybys, these greatly enhance their merger rates in the centers of galaxies by promoting the eccentricity excitation driven by the tidal fields.

We probe the small-scale absorption line variability using absorption depth based analysis of a sample of 64 ultra-fast outflow (UFO) C IV broad absorption line (BAL) quasars monitored using the Southern African Large Telescope. We confirm the strong monotonic increase in the strength of variability with increasing outflow velocity. We identify regions inside the BAL trough for each source where the normalized flux difference between two epochs is $>$0.1 for a velocity width $\ge$500 kms$^{-1}$ (called ``variable regions"). We find the total number of variable regions increases with the time interval probed and the number of BALs showing variable regions almost doubles from short ($<$2 yrs) to long ($>$2 yrs) time scales. We study the distributions of variable region properties such as its velocity width, depth, and location. These regions typically occupy a few-tenths of the entire width of the BAL. Their widths are found to increase with increasing time scales having typical widths of ~2000 kms$^{-1}$ for dt $>$ 2 yr. However, their absolute velocity with respect to z$_{em}$ and their relative position within the BAL profile remain random irrespective of the time scale probed. The equivalent width variations of the BALs are strongly dependent on the size and depth of the variable regions but are little dependent on their total number. Finally, we find that ~17% of the UFO BALs show uncorrelated variability within the BAL trough.

Revealing the large-scale structure from the 21cm intensity mapping surveys is only possible after the foreground cleaning. However, most current cleaning techniques relying on the smoothness of the foreground spectrum lead to a severe side effect of removing the large-scale structure signal along the line of sight. On the other hand, the clustering fossil, a coherent variation of the small-scale clustering over large scales, allows us to recover the long-wavelength density modes from the off-diagonal correlation between short-wavelength modes. In this paper, we study the requirements for an unbiased and optimal clustering-fossil estimator and show that (A) the estimator is unbiased only when using an accurate bispectrum model for the long-short-short mode coupling and (B) including the connected four-point correlation functions is essential for characterizing the noise power spectrum of the estimated long mode. The clustering fossil estimator based upon the leading-order bispectrum yields an unbiased estimation of the long-wavelength ($k\lesssim 0.01~[h/{\rm Mpc}]$) modes with the cross-correlation coefficient of $0.7$ at redshifts $z=0$ to $3$.

The Balloon Experiment for Galactic INfrared Science (BEGINS) is a concept for a sub-orbital observatory that will operate from $\lambda$ = 25-250 $\mu$m to characterize dust in the vicinity of high-mass stars. The mission's sensitivity requirements will be met by utilizing arrays of 1,840 lens-coupled, lumped-element kinetic inductance detectors (KIDs) operating at 300 mK. Each KID will consist of a titanium nitride (TiN) parallel strip absorbing inductive section and parallel plate capacitor (PPC) deposited on a silicon (Si) substrate. The PPC geometry allows for reduction of the pixel spacing. At the BEGINS focal plane the detectors require optical NEPs from $2\times10^{-16}$ W/$\sqrt{\textrm{Hz}}$ to $6\times10^{-17}$ W/$\sqrt{\textrm{Hz}}$ from 25-250 $\mu$m for optical loads ranging from 4 pW to 10 pW. We present the design, optical performance and quasiparticle lifetime measurements of a prototype BEGINS KID array at 25 $\mu$m when coupled to Fresnel zone plate lenses. For our optical set up and the absorption efficiency of the KIDs, the electrical NEP requirement at 25 $\mu$m is $7.6\times10^{-17}$ W/$\sqrt{\textrm{Hz}}$ for an absorbed optical power of 0.36 pW. We find that over an average of five resonators the the detectors are photon noise limited down to about 200 fW, with a limiting NEP of about $7.4\times10^{-17}$ W/$\sqrt{\textrm{Hz}}$.

We select a sample of 1,437 active galactic nuclei (AGN) from the catalog of the Sloan Digital Sky Survey (SDSS) galaxy properties from the Portsmouth group by detection of the high-ionization [Ne V] 3426 \r{A} emission line. We compare the fluxes of [Ne III] 3869 \r{A}, [O III] 5007 \r{A}, [O II] 3726, 3728 \r{A}, and [O I] 6300 \r{A} to that of [Ne V]. All four lines show a strong linear correlation with [Ne V], although lines from ions with lower ionization potentials have a lower correlation coefficient. We investigate the use of two forbidden-line ratio (FLR) diagnostic diagrams that do not rely on H$\alpha$ in order to classify high redshift galaxies. These use the [Ne III]/[O II] line ratio plotted against [O III]/[O I] and [O III]/[O II] respectively. We use photo-ionization modeling to characterize the behavior of the narrow-line region in AGN and star-forming regions and test the validity of our diagnostic diagrams. We also use a luminosity cutoff of log L[OIII] [erg/s] = 42, which lowers the contamination of the AGN region by star-forming galaxies down to 10% but does not remove Green Pea and Purple Grape galaxies from the AGN region. We also investigate the OHNO diagram which uses [Ne III]/[O II] plotted against [O III]/H$\beta$. Using our new diagnostic diagrams, we are able to reliably classify AGN up to a redshift of z $\leq$ 1.06, and add more than 822 new AGN to the [Ne V]-selected AGN sample.

Since the discovery of the first hot Jupiter orbiting a solar-type star, 51 Peg, in 1995, more than 4000 exoplanets have been identified using various observational techniques. The formation process of these sub-Earths remains elusive, and acquiring additional samples is essential for investigating this unique population. In our study, we employ a novel GPU Phase Folding algorithm combined with a Convolutional Neural Network, termed the GPFC method, on Kepler photometry data. This method enhances the transit search speed significantly over the traditional Box-fitting Least Squares method, allowing a complete search of the known KOI photometry data within hours using a commercial GPU card. To date, we have identified five promising sub-Earth short-period candidates: K00446.c, K01821.b, K01522.c, K03404.b, and K04978.b. A closer analysis reveals the following characteristics: K00446.c orbits a K dwarf on a 0.645091-day period. With a radius of $0.461R_\oplus$, it ranks as the second smallest USP discovered to date. K01821.b is a sub-Earth with a radius of $0.648R_\oplus$, orbiting a G dwarf over a 0.91978-day period. It is the second smallest USP among all confirmed USPs orbiting G dwarfs in the NASA Archive. K01522.c has a radius of $0.704 R_\oplus$ and completes an orbit around a Sun-like G dwarf in 0.64672 days; K03404.b, with a radius of $0.738 R_\oplus$, orbits a G dwarf on a 0.68074-day period; and K04978.b, with its planetary radius of $0.912 R_\oplus$, orbits a G dwarf, completing an orbit every 0.94197 days. Three of our finds, K01821.b, K01522.c and K03404.b, rank as the smallest planets among all confirmed USPs orbiting G dwarfs in the Kepler dataset. The discovery of these small exoplanets underscores the promising capability of the GPFC method for searching for small, new transiting exoplanets in photometry data from Kepler, TESS, and future space transit missions.

Aims. We aim to study the structure and kinematics of the two filaments inside the subsonic core Barnard 5 in Perseus using high-resolution ($\approx$ 2400 au) NH3 data and a multi-component fit analysis. Methods. We used observations of NH3 (1,1) and (2,2) inversion transitions using the Very Large Array (VLA) and the Green Bank Telescope (GBT). We smoothed the data to a beam of 8'' to reliably fit multiple velocity components towards the two filamentary structures identified in B5. Results. Along with the core and cloud components, which dominate the flux in the line of sight, we detected two components towards the two filaments showing signs of infall. We also detected two additional components that can possibly trace new material falling into the subsonic core of B5. Conclusions. Following comparison with previous simulations of filament formation scenarios in planar geometry, we conclude that either the formation of the B5 filaments is likely to be rather cylindrically symmetrical or the filaments are magnetically supported. We also estimate infall rates of $1.6\times10^{-4}\,M_\odot\,yr^{-1}$ and $1.8\times10^{-4}\,M_\odot\,yr^{-1}$ (upper limits) for the material being accreted onto the two filaments. At these rates, the filament masses can change significantly during the core lifetime. We also estimate an upper limit of $3.5\times10^{-5}\,M_\odot\,yr^{-1}$ for the rate of possible infall onto the core itself. Accretion of new material onto cores indicates the need for a significant update to current core evolution models, where cores are assumed to evolve in isolation.

Tidal disruption event (TDE) iPTF16fnl shows a relatively low optical flare with observationally very weak X-ray emission and the spectroscopic property that the helium emission line from the source dominates over the hydrogen emission line at early times. We explore these observed signatures by calculating spectral emission lines with the publicly available code, CLOUDY. We estimate five physical parameters by fitting the observed optical UV spectra on multiple days to a theoretical model of a steady-state, slim disk with a spherical outflow. The resultant key parameters among them are black hole mass $M_{\bullet} = (6.73 \pm 0.44) \times 10^5 M_{\odot}$, stellar mass $M_{\star} = (2.59 \pm 0.17) M_{\odot}$, and wind velocity $v_{\rm w} = 7447.43 \pm 183.9~{\rm km~s^{-1}}$. The disk-wind model also estimates the radiative efficiency to be $0.01\lesssim\eta\lesssim0.02$ over the observational time, resulting in the disk being radiatively inefficient, and the disk X-ray luminosity is consistent with the observed low luminosity. In our CLOUDY model, the filling factor of the wind is also estimated to be 0.8, suggesting that the wind is moderately clumpy. We reveal that the helium-to-hydrogen number density ratio of the wind lies between 0.1 and 0.15, which is nearly the same as the solar case, suggesting the tidally disrupted star is originally a main sequence star. Because the optical depth of the helium line is lower than the hydrogen line by two orders of magnitude, the helium line is significantly optically thinner than the hydrogen line. Consequently, our results indicate that the helium line luminosity dominates the hydrogen line luminosity due to the optical depth effect despite a small helium-to-hydrogen number density ratio value.

Changes in the flux and spectrum of Eta Carinae since 1900 have been attributed to the evolution of the central binary by some. Others suggest evolution in the occulting ejecta. The brightness jump in the 1940s, which coincided with the appearance of narrow forbidden emission lines, may have been caused by the clearing and ionization of intervening circumstellar ejecta. The brightening changed at a slower pace up through forty years later. Here we continue earlier studies focused on the long-term showing that the forbidden line emission increased in the early 1990s with no noticeable increase in the brightness of the Homunculus. We interpret that the increase in narrow line emission is due to decreased extinction in the LOS from the central binary to the Weigelt clumps. In 2000, the central stellar core increased in brightness at a faster rate without associated changes in the Homunculus. By 2018, hundreds of narrow-line absorptions from singly-ionized metals in our LOS from Eta Carinae disappeared, thought to be caused by increased ionization of metals. These three events (1990, 2000, and 2018) are explained by the dissipation of circumstellar material within the Homunculus close to the binary. Combining these changes with the steadiness of the Homunculus and the primary winds over the past four decades indicates that circumstellar ejecta in our direction have been cleared.

To investigate whether disk-mediated accretion is the primary mechanism in high-mass star formation, we have established a survey of a large sample of massive dense cores within a giant molecular cloud. We used high angular resolution ($\sim 1.8''$) observations with SMA to study the dust emission and molecular line emission of about 50 massive dense cores in Cygnus-X. At a typical distance of 1.4 kpc for Cygnus-X, these massive dense cores are resolved into $\sim 2000$ au condensations. We combined the CO outflow emission and gas kinematics traced by several high-density tracers to search for disk candidates. We extracted hundreds of dust condensations from the SMA 1.3 mm dust continuum emission. The CO data show bipolar or unipolar outflow signatures toward 49 dust condensations. Among them, only 27 sources are detected in dense gas tracers, which reveals the gas kinematics, and nine sources show evidence of rotating envelopes, suggesting the existence of embedded accretion disks. The position-velocity diagrams along the velocity gradient of all rotating condensations suggest that four condensations are possible to host Keplerian-like disks. A detailed investigation of the 27 sources detected in dense gas tracers suggests that the nine disk candidates are at earlier evolutionary stages compared to the remaining 18 sources. Non-detection of rotating disks in our sample may be due to several factors, including an unknown inclination angle of the rotation axis and an early evolutionary stage of the central source, and the latter could be important, considering that young and powerful outflows could confuse the observational evidence for rotation. The detection rate of disk candidates in our sample is 1/3, which confirms that disk accretion is a viable mechanism for high-mass star formation, although it may not be the only one.

The observations of gravitational waves (GWs) have revealed the existence of black holes (BHs) above $30M_\odot$. A variety of scenarios have been proposed as their origin. Among the scenarios, we consider the population III (Pop~III) star scenario. In this scenario, binary black holes (BBHs) containing such massive BHs are naturally produced. We consider Pop~I/II field binaries, Pop~III field binaries and the binaries dynamically formed in globular clusters. We employ a hierarchical Bayesian analysis method and constrain the branching fraction of each formation channel in our universe by using the LIGO-Virgo-KAGRA gravitational wave transient catalog (GWTC-3) events. We find that the Pop~I/II field binary channel dominates the entire merging BBHs. We obtain the branching fraction of the Pop~III BBH channel of $0.11^{+0.08}_{-0.06}$, which gives the consistent local merger rate density with the model of Pop~III BBH scenario we adopt. We confirm that BHs arising from the Pop~III channel contribute to massive BBHs in GWTC-3. We also evaluate the branching fraction of each formation channel in the observed BBHs in the GWTC-3 and find the near-equal contributions from the three channels.

The energy released from dark matter annihilation leads to additional ionization and heating of the intergalactic gas and thereby impact the hydrogen 21-cm signal during the cosmic dawn. The dark matter annihilation rate scales as density-squared and it becomes inhomogeneously boosted along with structure formation. This paper examines the inhomogeneity in DM annihilation rate induced by the growth of DM halo structures, and we show that this effect can significantly enhance the spatial fluctuations in gas temperature, gas ionization fraction and consequently the 21-cm brightness temperature. Compared to previous homogeneous calculations, inhomogeneous dark matter annihilation can enhance the 21-cm power spectrum by orders of magnitude across the scales of $k \in [0.05, 3]\ {\rm{Mpc^{-1}}}$. For a DM annihilation rate of $\left<\sigma v\right>/m_\chi \sim 10^{-27} {\rm cm^3 s^{-1} GeV^{-1}}$, the corresponding signatures in the 21-cm power spectrum signal can be detected by upcoming radio observatories such as the SKA.

We argue that the lensing power spectrum of astrometric shift (lensing shift power spectrum) is a powerful tool of the clustering property of dark matter on subgalactic scales. First we give the formalism to probe the nature of dark matter by using the lensing shift power spectrum. Then, leveraging recent measurements of the lensing shift power spectrum on an angular scale of approximately $1~$arcsec towards the gravitationally lensed quasar MG$\,$J0414+0534 at the redshift of $z_S=2.639$, we place constraints on the mass of warm dark matter (WDM) particles $m_{\rm WDM}$ and their fraction in a mixed dark matter (MDM) model $r_{\rm WDM}$, in which WDM and cold dark matter coexist. Although the constraint derived from the above single lensing system is not as strong as the existing constraints, as we show in this paper, the lensing shift power spectrum has a great potential to obtain much tighter constraints on WDM and MDM models through future observations, highlighting the importance of well-controlled systematic error considerations for achieving enhanced precision.

Near-equilibrium bottom-up crystallization of fully-ionized neutron star crusts or white dwarf cores is considered. We argue that this process is similar to liquid-phase epitaxial (i.e. preserving order of previous layers) crystal growth or crystal pulling from melt in Earth laboratories whereby lateral positions of newly crystallizing ions are anchored by already solidified layers. Their vertical positions are set by charge neutrality. Consequently, interplane spacing of a growing crystal either gradually increases, tracing $n_\mathrm{e}$ decrease, as the crystallization front moves away from the stellar center, or decreases, tracing decrease of $\langle Z \rangle$, when the crystallization front crosses a boundary between layers of different compositions. This results in a formation of stretched Coulomb crystals, in contrast to the standard assumption of cubic crystal formation, which is based on energetics arguments but does not take into account growth kinetics. Overstretched crystals break, which limits the vertical sizes of growing crystallites. We study breaking shear strain and effective shear modulus of stretched matter and discuss possibility of macrocrystallite formation. The latter has interesting astrophysical implications, for instance, appearance of weak crustal layers, whose strength may increase by a few orders of magnitude upon breaking and refreezing at a late-time event. We also analyze interaction of adjacent Coulomb crystals, having different ion compositions, and estimate the strength of such interfaces.

RW Aurigae is a young stellar system containing a classical T Tauri star as the primary component. It shows deep, irregular dimmings, first detected in 2010. At the University Observatory Jena, we carried out optical follow-up observations. We performed multiband (BVRI) photometry of the system with the Cassegrain-Teleskop-Kamera II and the Schmidt-Teleskop-Kamera between September 2016 and April 2019, as well as spectroscopy, using the Fibre Linked \'ECHelle Astronomical Spectrograph between September 2016 and April 2018. We present the apparent photometry of RW Aur, which is consistent with and complementary to photometric data from the American Association of Variable Star Observers. The V-band magnitude of RW Aur changed by up to three magnitudes during the timespan of our monitoring campaign. For the observing epochs 2016/2017 and 2017/2018 we report a decreasing brightness, while in the epoch 2018/2019 the system remained in a relatively constant bright state. In the color-magnitude diagram, we see that RW Aur lies close to a track for grey extinction. The spectra show a decreasing equivalent width of the H$\alpha$ emission line for decreasing brightness, whereas the equivalent width of the [OI] line increases, indicating an increased outflow activity during the obscuration. Both gives further evidence for the favored theory that the obscurations are caused by a hot dusty wind emerging from the inner disk.

We forecast the sensitivity of ongoing and future galaxy cluster abundance measurements to detect deviations from the cold dark matter (CDM) paradigm. Concretely, we consider a class of dark sector models that feature an interaction between dark matter and a dark radiation species (IDM-DR). This setup can be naturally realized by a non-Abelian gauge symmetry and has the potential to explain $S_8$ tensions arising within $\Lambda$CDM. We create mock catalogs of the ongoing SPT-3G as well as the future CMB-S4 surveys of galaxy clusters selected via the thermal Sunyaev-Zeldovich effect (tSZE). Both datasets are complemented with cluster mass calibration from next-generation weak gravitational lensing data (ngWL) like those expected from the Euclid mission and the Vera C. Rubin Observatory. We consider an IDM-DR scenario with parameters chosen to be in agreement with Planck 2018 data and that also leads to a low value of $S_8$ as indicated by some local structure formation analyses. Accounting for systematic and stochastic uncertainties in the mass determination and the cluster tSZE selection, we find that both SPT-3G$\times$ngWL and CMB-S4$\times$ngWL cluster data will be able to discriminate this IDM-DR model from $\Lambda$CDM, and thus test whether dark matter - dark radiation interactions are responsible for lowering $S_8$. Assuming IDM-DR, we forecast that the temperature of the dark radiation can be determined to about 40% (10%) with SPT-3G$\times$ngWL (CMB-S4$\times$ngWL), considering 68% credibility, while $S_8$ can be recovered with percent-level accuracy. Furthermore, we show that IDM-DR can be discriminated from massive neutrinos, and that cluster counts will be able to constrain the dark radiation temperature to be below $\sim 10%$ (at 95% credibility) of the cosmic microwave background temperature if the true cosmological model is $\Lambda$CDM.

We apply the inverse Gertsenshtein effect, i.e., the graviton-photon conversion in the presence of a magnetic field, to constrain high-frequency gravitational waves (HFGWs). Using existing astrophysical measurements, we compute upper limits on the GW energy densities $\Omega_{\rm GW}$ at 16 different frequency bands. Given the observed magnetisation of galaxy clusters with field strength $B\sim\mu{\rm G}$ correlated on $\mathcal{O}(10)\,{\rm kpc}$ scales, we estimate HFGW constraints in the $\mathcal{O}(10^2)\,{\rm GHz}$ regime to be $\Omega_{\rm GW}\lesssim10^{16}$ with the temperature measurements of the Atacama Cosmology Telescope (ACT). Similarly, we conservatively obtain $\Omega_{\rm GW}\lesssim10^{13} (10^{11})$ in the $\mathcal{O}(10^2)\,{\rm MHz}$ ($\mathcal{O}(10)\,{\rm GHz}$) regime by assuming uniform magnetic field with strength $B\sim0.1\,{\rm nG}$ and saturating the excess signal over the Cosmic Microwave Background (CMB) reported by radio telescopes such as the Experiment to Detect the Global EoR Signature (EDGES), LOw Frequency ARray (LOFAR), and Murchison Widefield Array (MWA), and the balloon-borne second generation Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE2) with graviton-induced photons. Although none of these existing constraints fall below the critical value of $\Omega_{\rm GW} = 1$ or reaches the Big Bang Nucleosynthesis (BBN) bound of $\Omega_{\rm GW}\simeq1.2\times10^{-6}$, the upcoming Square Kilometer Array (SKA) can improve the sensitivities by roughly 10 orders of magnitude and potentially become realistic probes of HFGWs. We also explore several next-generation CMB surveys, including Primordial Inflation Explorer (PIXIE), Polarized Radiation Interferometer for Spectral disTortions and INflation Exploration (PRISTINE) and Voyage 2050, that could potentially provide constraints competitive to the current BBN bound.

We present a multi-wavelength analysis of the star cluster NGC 2316 and its surroundings. We estimated the physical parameters of the NGC 2316 cluster, including its shape (elongated), size (Rcluster = 0.4 pc), distance (1.3 +/- 0.3 kpc), and minimum reddening (AV = 1.55 mag). We discovered two massive stars (B2.0V-B1.5V, age ~12 Myr) embedded (AV = 4 mag) within this cluster. The cluster region still forms young stars even though the most massive star was born ~12 Myr ago. We also found evidence of positive feedback from these massive stars. We identified a cold gas/dust lane extending westward from the cluster. The western end of the dust lane seems to favor low-mass star formation, whereas the cluster's end favors bit massive star formation, which seems to have started earlier than the western end. We found an elongated molecular cloud in this region, characterized by numerous filamentary structures. The morphology of the filaments, along with position-velocity (pv) maps, velocity dispersion maps, channel maps, etc., indicate a coalescence of filaments and a potential longitudinal flow of matter toward the cluster through the western end of the gas/dust lane. This entire region seems to be a Hub-filamentary system (HFS), in which the NGC 2316 cluster is probably the hub and the dark lane is the main filamentary structure. Being the gravity well of this HFS, star formation started first in the NGC 2316 region and went on to the other filamentary nodes.

Radio telescopes are susceptible to interference arriving through its sidelobes. If a reflector antenna could be retrofitted with an adaptive null steering system, it could potentially mitigate this interference. The design of a reflectarray which can be used to reconfigure a radio telescopes radiation pattern by driving a null to the angle of incoming interference is presented. The reflectarray occupies only a portion of the rim of the original reflector and lays conformal to the paraboloid within this region. The conformal reflectarray contains unit cells with 1-bit reconfigurability stemming from two symmetrically placed PIN diodes. It is found that the dielectric and switch losses introduced by the reflectarray do not significantly affect the radio telescopes efficiency since the reflectarray is placed only along the outer rim of the reflector which is weakly illuminated. Simulation results of an L-band reconfigurable reflectarray for an 18m prime focus fed parabola are presented.

Photonspheres, curved hypersurfaces on which massless particles can perform closed geodesic motions around highly compact objects, are an integral part of generic black-hole spacetimes. In the present compact paper we prove, using analytical techniques, that the innermost light rings of spherically symmetric hairy black-hole spacetimes whose external matter fields are characterized by a traceless energy-momentum tensor cannot be located arbitrarily close to the central black hole. In particular, we reveal the physically interesting fact that the non-linearly coupled Einstein-matter field equations set the lower bound $r_{\gamma}\geq {6\over5}r_{\text{H}}$ on the radii of traceless black-hole photonspheres, where $r_{\text{H}}$ is the radius of the outermost black-hole horizon.

We describe quantum correction to the accreting hot plasma onto black holes. This quantum correction is related with the Hawking radiation, which heats the accreting plasma. The hot accreting gas is heated additionally by the quantum Hawking radiation. It is demonstrated that Hawking radiation prevails over the Compton scattering of hot electrons in the accreting flow onto the small enough evaporating black holes with masses $M<M_q\simeq 4.61\cdot10^{29}$ grams. In result, the evaporating black holes with masses $M<M_q$ reverse the inflowing plasma into outflowing one and stop the black hole accretion at all. The black holes with masses $M<M_q$ made contribute to the enigmatic dark matter at the galactic disks, galactic halos and even in the intergalactic space, if these black holes are primordial in origin.

We perform observational confrontation and cosmographic analysis of $f(T,T_G)$ gravity and cosmology. This higher-order torsional gravity is based on both the torsion scalar, as well as on the teleparallel equivalent of the Gauss-Bonnet combination, and gives rise to an effective dark-energy sector which depends on the extra torsion contributions. We employ observational data from the Hubble function and Supernova Type Ia Pantheon datasets, applying a Markov Chain Monte Carlo sampling technique, and we provide the iso-likelihood contours, as well as the best-fit values for the parameters of the power-law model. Additionally, we reconstruct the effective dark-energy equation-of-state parameter, which exhibits a quintessence-like behavior, while in the future the Universe enters into the phantom regime, before it tends asymptotically to the cosmological constant value. Furthermore, we perform a detailed cosmographic analysis, examining the deceleration, jerk, snap and lerk parameters, showing that the transition to acceleration occurs in the redshift range $ 0.52 \leq z_{tr} \leq 0.89 $, as well as the preference of the scenario for quintessence-like behavior. Finally, we apply the Om diagnostic analysis, as a cross-verification of the obtained behavior.

In this paper, we review the theoretical basis for generation of gravitational waves and the detection techniques used to detect a gravitational wave. To materialize this goal in a thorough way we first start with a mathematical background for general relativity from which a clue for gravitational wave was conceived by Einstein. Thereafter we give the classification scheme of gravitational waves such as (i) continuous gravitational waves, (ii) compact binary inspiral gravitational waves and (iii) stochastic gravitational wave. Necessary mathematical insight into gravitational waves from binaries are also dealt with which follows detection of gravitational waves based on the frequency classification. Ground based observatories as well as space borne gravitational wave detectors are discussed in a length. We have provided an overview on the inflationary gravitational waves. In connection to data analysis by matched filtering there are a few highlights on the techniques, e.g. (i) Random noise, (ii) power spectrum, (iii) shot noise, and (iv) Gaussian noise. Optimal detection statistics for a gravitational wave detection is also in the pipeline of the discussion along with detailed necessity of the matched filter and deep learning.

We show that high-energy astrophysical neutrinos produced in the cores of heavily obscured active galactic nuclei (AGNs) can undergo strong matter effects, thus significantly influencing their source flavor ratios. In particular, matter effects can completely modify the standard interpretation of the flavor ratio measurements in terms of the physical processes occurring in the sources (e.g., $pp$ versus $p\gamma$, full pion-decay chain versus muon-damped pion decay). We contrast our results with the existing flavor ratio measurements at IceCube, as well as with projections for next-generation neutrino telescopes like IceCube-Gen2. Signatures of these matter effects in neutrino flavor composition would not only bring more evidence for neutrino production in central AGN regions, but would also be a powerful probe of heavily Compton-thick AGNs, which escape conventional observation in $X$-rays and other electromagnetic wavelengths.

We formulate a renormalisation procedure for IR divergences of tree-level in-in late-time de Sitter correlators. These divergences are due to the infinite volume of spacetime and are analogous to the divergences that appear in AdS dealt with by holographic renormalisation. Regulating the theory using dimensional regularisation, we show that one can remove all infinities by adding local counterterms at the future boundary of dS in the Schwinger-Keldysh path integral. The counterterms amount to renormalising the late-time bulk field. We frame the discussion in terms of bulk scalar fields in dS, using tree-level correlators of massless and conformal scalars for illustration. The relation to AdS via analytic continuation is discussed, and we show that different versions of the analytic continuation appearing in the literature are equivalent to each other. In AdS, one needs to add counterterms that are related to conformal anomalies, and also to renormalise the source part of the bulk field. The analytic continuation to dS projects out the traditional AdS counterterms, and links the renormalisation of the sources to the renormalisation of the late-time bulk field. We use these results to establish holographic formulae that relate tree-level dS in-in correlators to CFT correlators at up to four points, and we provide two proofs: one using the connection between the dS wavefunction and the partition function of the dual CFT, and a second by direct evaluation of the in-in correlators using the Schwinger-Keldysh formalism. The renormalisation of the bulk IR divergences is mapped by these formulae to UV renormalisation of the dual CFT via local counterterms, providing structural support for a possible duality. We also recast the regulated holographic formulae in terms of the AdS amplitudes of shadow fields, but show that this relation breaks down when renormalisation is required.

A cosmological model based on two scalar fields is proposed. The first of these, $\varphi$, has mass $\mu$, while the second, $\chi$, is massless. The pair are coupled through a ``Higgs portal''. First, we show how the model reproduces the Friedmann equations if the square of the mass of $\varphi$ is proportional to the cosmological constant and $\chi$ represents the quintessence field. Quantum corrections break the conformal symmetry and $\chi$ acquires a mass that is equal to $\sqrt{3g \Lambda}$. Using dimensional analysis, we estimate the coupling constant and the mass of $\chi$ and obtain that $g\sim 10^{-26}$ and $m_\chi \sim 4.5\times10^{-10}\,$ eV, which is in accordance with what is expected in the quintessence scenario. the acceleration of the universe is proportional to $\chi^2$, we conclude that for very long times, the solution of the equation of motion goes to ${m_\chi}/{{\sqrt\lambda}}$ and the universe, although it continues to accelerate, the acceleration is constant

We propose a model of uniform rate inflation on the brane. The potential is given by a hyperbolic cosine function plus a negative cosmological constant. The equation of motion is solved analytically without using slow-roll approximation. The result is that the inflaton field is rolling at a constant speed. The prediction for cosmological perturbations depends on the field value at the end of inflation. The experimental constraints could be satisfied in the parameter space.

In GUT-scale constrained (GUTc) supersymmetric (SUSY) models, the mass of smuon $\tilde{\mu}_1$ is typically heavier than that of stau $\tilde{\tau}_1$, and stau co-annihilation is a typical annihilation mechanism of dark matter. However, light smuon is more favored by the muon $g-2$ anomaly, thus smuon-neutralino loop contribution to muon $g-2$ is usually smaller than that of sneutrino-chargino. Inspired by the latest muon $g-2$ results, we take the GUTc- Next-to-Minimal Supersymmetric Model (NMSSM) as an example, where the gaugino (Higgs) masses are not unified to the usual parameter $M_{1/2}$ ($M_0$), exploring its possibility of light smuon and its contribution to muon $g-2$. After complicated calculations and discussions, we conclude that in GUTc-NMSSM the smuon can be lighter than stau. In this light-smuon scenario, the contribution of smuon-neutralino loop to the muon $g-2$ can be larger than that of the sneutrino-chargino loop. The annihilation mechanisms of dark matter are dominated by multiple slepton or chargino co-annihilation. In our calculations, we consider also other latest related constraints like Higgs data, SUSY searches, dark matter relic density and direct detections, etc.

The correlation between Higgs-like scalars and light dark matter is an interesting topic, especially now that a $125 GeV$ Higgs was discovered and dark matter (DM) searches got negative results. The $95 GeV$ excess reported by the CMS collaboration with $132 fb^{-1}$ data recently, and the DM search results by XENONnT and LZ collaborations motivate us to revise that. In this work, we study that in the GUT-scale constrained (GUTc) Next-to-Minimal Supersymmetric Model (NMSSM), where most parameters are input at the GUT scale, but with scalar and gaugino masses not unified there. In the calculation we also consider other recent experimental constraints, such as Higgs data, Supersymmetry (SUSY) searches, DM relic density, etc. After detailed analysis and discussion, we find that: (i) The light DM can be bino- or singlino-dominated, but can be mixed with minor components of Higgsino. (ii) Both cases can get right relic density and sizable Higgs invisible decay, by adjusting the dimensionless parameters $\lambda, \kappa$, or suitably mixing with Higgsino. (iii) Both cases can have four funnel annihilation mechanisms, i.e., annihilating through $Z, a_1, h_2, h_1$. (iv) Samples with right relic density usually get weak signal of Higgs invisible decay at future lepton collider, but the $95 GeV$ scalar can have sizable $b\bar{b}$ signal.

It is well-known that the theory of Cotton gravity proposed by Harada is trivially solved by all isotropic and homogeneous cosmologies. We show that this under-determination is more general. More precisely, the degree of arbitrariness in the solutions increases with the degree of symmetry. We give two simple examples. The first is that of static spherically symmetric solutions, which depend on an arbitrary function of the radial coordinate. The second is that of anisotropic cosmologies, which depend on an arbitrary function of time.