Papers for Friday, Mar 22 2024

An open or hyperbolic Friedmann-Robertson-Walker spacetime dominated by tachyonic dark matter can exhibit an ``inflected'' expansion -- initially decelerating, later accelerating -- similar but not identical to that of now-standard $\Lambda$CDM models dominated by dark energy. The features of the tachyonic model can be extracted by fitting the redshift-distance relation of the model to data obtained by treating Type Ia supernovae as standard candles. Here such a model is fitted to samples of 186 and 1048 Type Ia supernovae from the literature. The fits yield values of $H_0=(66.6\pm1.5)~\hbox{km/s/Mpc}$ and $H_0=(69.6\pm0.4)~\hbox{km/s/Mpc}$, respectively, for the current-time Hubble parameter, and $t_0=(8.35\pm0.68)~\hbox{Gyr}$ and $t_0=(8.15\pm0.36)~\hbox{Gyr}$, respectively, for the comoving-time age of the Universe. Tests of the model against other observations will be undertaken in subsequent works.

Strong gravitational lensing can be used as a tool for constraining the substructure in the mass distribution of galaxies. In this study we investigate the power spectrum of dark matter perturbations in a population of 23 Hubble Space Telescope images of strong galaxy-galaxy lenses selected from The Sloan Lens ACS (SLACS) survey. We model the dark matter substructure as a Gaussian Random Field perturbation on a smooth lens mass potential, characterized by power-law statistics. We expand upon the previously developed machine learning framework to predict the power-law statistics by using a convolutional neural network (CNN) that accounts for both epistemic and aleatoric uncertainties. For the training sets, we use the smooth lens mass potentials and reconstructed source galaxies that have been previously modelled through traditional fits of analytical and shapelet profiles as a starting point. We train three CNNs with different training set: the first using standard data augmentation on the best-fitting reconstructed sources, the second using different reconstructed sources spaced throughout the posterior distribution, and the third using a combination of the two data sets. We apply the trained CNNs to the SLACS data and find agreement in their predictions. Our results suggest a significant substructure perturbation favoring a high frequency power spectrum across our lens population.

Understanding the details of $r$-process nucleosynthesis in binary neutron star mergers (BNSMs) ejecta is key to interpret kilonovae observations and to identify the role of BNSMs in the origin of heavy elements. We present a self-consistent 2-dimensional (ray-by-ray) radiation-hydrodynamic evolution of BNSM ejecta with an online nuclear network (NN) up to the days timescale. For the first time, an initial numerical-relativity ejecta profile composed of the dynamical component, spiral-wave and disk winds is evolved including detailed $r$-process reactions and nuclear heating effects. A simple model for the jet energy deposition is also included. Our simulation highlights that the commonly assumed approach of relating the final nucleosynthesis yields to the initial thermodynamic profile of the ejecta can lead to inaccurate predictions. We also find significant deviations (up to four orders of magnitudes) in the abundance evolution of several analyzed elements compared to previous predictions employing the NN in post-processing. The presence of a jet affects elements production only in the innermost part of the polar ejecta, and it does not alter the global nucleosynthesis results. Overall, our analysis shows that employing an online NN is highly desiderable in order to obtain reliable predictions of $r$-process nucleosynthesis and ejecta evolution.

Measurements of Type Ia Supernovae (SNe Ia) in the near-infrared (NIR) have been used both as an alternate path to cosmology compared to optical measurements and as a method of constraining key systematics for the larger optical studies. With the DEHVILS sample, the largest published NIR sample with consistent NIR coverage of maximum light across three NIR bands ($Y$, $J$, and $H$), we check three key systematics: (i) the reduction in Hubble residual scatter as compared to the optical, (ii) the measurement of a "mass step" or lack thereof and its implications, and (iii) the ability to distinguish between various dust models by analyzing correlations between Hubble residuals in the NIR and optical. We produce accurate simulations of the DEHVILS sample and find, contrary to assumptions in the literature, it is $\textit{harder}$ to differentiate between various dust models than previously understood. Additionally, we find that fitting with the current SALT3 model does not yield accurate wavelength-dependent stretch-luminosity correlations, and we propose a limited solution for this problem. From the data, we see that (i) the standard deviation of Hubble residual values from NIR bands treated as standard candles are 0.007-0.042 mag smaller than those in the optical, (ii) the NIR mass step is not constrainable with the current sample size from DEHVILS, and (iii) Hubble residuals in the NIR and optical are correlated in both the simulations and the data. We test a few variations on the number and combinations of filters and data samples, and we observe that none of our findings or conclusions are significantly impacted by these modifications.

We present the observational mass-radius (M-R) relation for a sample of 47 magnetized white dwarfs (WDs) with the magnetic field strength (B) ranging from 1 to 773 MG, identified from the SDSS data release 7 (DR7). We derive their effective temperature, surface gravity (log g), luminosity, radius, and mass. While atmospheric parameters are derived using a Virtual Observatory Spectral Energy Distribution Analyzer (VOSA), the mass is derived using their location in the HR diagram in comparison with the evolutionary tracks of different masses. We implement this mass measurement instead of a more traditional method of deriving masses from log g, which is unreliable as is based on SED and generates errors from other physical parameters involved. The main disadvantage of this method is that we need to assume a core composition of WDs. As it is complicated to identify the exact composition of these WDs from low-resolution spectra, we use tracks for the masses 0.2 to 0.4 solar mass assuming a He-core, 0.5 to 1.0 solar mass assuming CO core, and above solar mass assuming O-Ne-Mg core. We compare the observed M-R relation with those predicted by the finite temperature model by considering different B, which are well in agreement considering their relatively low surface fields, less than or of the order of 10^9 G. Currently, there is no direct observational detection of magnetized WDs with B > 10^9 G. We propose that our model can be further extrapolated to higher B, which may indicate the existence of super-Chandrasekhar mass (M > 1.4 solar mass) WDs at higher B.

In the absence of a parallax distance to a pulsar or a surviving binary in a supernova remnant (SNR), distances to Galactic SNRs are generally very uncertain. However, by combining Gaia data with wide field, multi-fiber echelle spectroscopy, it is now possible to obtain accurate distances to many SNRs with limited extinction by searching for the appearance of high velocity CaII or NaI absorption lines in hot stars as a function of distance. We demonstrate this for the SNR S147 using the spectra of 259 luminous, blue stars. We obtain a median distance of 1.37 kpc (1.30 to 1.47 kpc at 90% confidence) that is consistent with the median parallax distance to the pulsar of 1.46 kpc (1.12 to 2.10 kpc at 90% confidence), but with significantly smaller uncertainties. Our distance is also consistent with the distance to the candidate unbound binary companion in this SNR, HD37424. The presence of high velocity absorption lines is correlated with the emission line flux of the SNR but not with the radio flux.

The Hubble function characterizes a given Friedmann-Robertson-Walker spacetime and can be related to the densities of the cosmological fluids and their equations of state. We show how physics-informed neural networks (PINNs) emulate this dynamical system and provide fast predictions of the luminosity distance for a given choice of densities and equations of state, as needed for the analysis of supernova data. We use this emulator to perform a model-independent and parameter-free reconstruction of the Hubble function on the basis of supernova data. As part of this study, we develop and validate an uncertainty treatment for PINNs using a heteroscedastic loss and repulsive ensembles.

Recent multi-wavelength observations of gamma-ray burst afterglows observed in the TeV energy range challenge the simplest Synchrotron Self-Compton (SSC) interpretation of this emission, and are consistent with a single power-law component spanning over eight orders of magnitude in energy. To interpret this generic behaviour in the single-zone approximation without adding further free parameters, we perform an exhaustive parameter space study using the public, time-dependent, multi-messenger transport software AM3. This description accounts for the radiation from non-thermal protons and the lepto-hadronic cascade induced by pp- and p{\gamma}-interactions. We summarise the main scenarios which we have found (SSC, Extended-syn, Proton-syn, pp-cascade, and p{\gamma}-cascade), and discuss their advantages and limitations. We find that possible high-density environments, as may be typical for surrounding molecular cloud material, offer an alternative explanation for producing flat hard (source) spectra up to and beyond energies of 10 TeV.

We present new catalogs of likely globular clusters (GCs) in 17 nearby spiral galaxies studied as part of the PHANGS-HST Treasury Survey. The galaxies were imaged in five broad-band filters from the near-ultraviolet through the $I$ band. PHANGS-HST has produced catalogs of stellar clusters of all ages by selecting extended sources (from multiple concentration index measurements) followed by morphological classification (centrally concentrated and symmetric or asymmetric, multiple peaks, contaminant) by visually examining the V-band image and separately by a machine-learning algorithm which classified larger samples to reach fainter limits. From both cluster catalogs, we select an initial list of candidate GCs to have $B-V \geq 0.5$ and $V-I \geq 0.73$~mag, then remove likely contaminants (including reddened young clusters, background galaxies misclassified by the neural network, and chance superpositions/blends of stars) after a careful visual inspection. We find that $\approx86$ % of the color-selected candidates classified as spherically symmetric, and $\approx68$ of those classified as centrally concentrated but asymmetric are likely to be GCs. The luminosity functions of the GC candidates in 2 of our 17 galaxies, NGC 628 and NGC 3627, are atypical, and continue to rise at least 1~mag fainter than the expected turnover near $M_V \sim -7.4$. These faint candidate GCs have more extended spatial distributions than their bright counterparts, and may reside in the disk rather than the bulge/halo, similar to faint GCs previously discovered in M101. These faint clusters may be somewhat younger since the age-metallicity degeneracy makes it difficult to determine precise cluster ages from integrated colors once they reach $\approx1$~Gyr.

We have performed topographic and geological mapping of 19 large impact features on Ganymede and Callisto in order to gather morphometric and crater age data that allow us to quantify how the diverse morphologies of these features transition with size and age. The impact features are divided into two main morphological groups, craters and penepalimpsests/palimpsests. The morphologies of pit and dome craters are independent of age or geologic context, indicating that the impacts that formed them were small enough to only ever penetrate into a cold, rigid ice layer, with evolution of a pocket of impact melt contributing to the development of their central pits and surrounding raised annuli, while the domes formed mainly via viscous relaxation of the pit topography. The subdued rims of anomalous dome craters indicate the increasing effect of a warm subsurface ice layer on impact feature morphology with increasing size. The low topographic relief of penepalimpsests and palimpsests indicates that these impacts penetrated the ice shell to liberate large volumes of underlying, pre-existing liquid. Penepalimpsests show a higher frequency of concentric ridges within their interiors, indicating a more robust subsurface state that could support the rotation and uplift of solid material during impact. The size and age overlap of anomalous dome craters, penepalimpsests, and palimpsests, with a few impact features appearing to be transitional between anomalous dome craters and penepalimpsests, indicates that impactor size, time of impact, and variation in temperature gradient across the satellite are all factors in determining which of these morphologies emerges.

We present a new method for joint likelihood deconvolution (Jolideco) of a set of astronomical observations of the same sky region in the presence of Poisson noise. The observations may be obtained from different instruments with different resolution, and different point spread functions. Jolideco reconstructs a single flux image by optimizing the posterior distribution based on the joint Poisson likelihood of all observations under a patch-based image prior. The patch prior is parameterised via a Gaussian Mixture model which we train on high-signal-to-noise astronomical images, including data from the James Webb Telescope and the GLEAM radio survey. This prior favors correlation structures among the reconstructed pixel intensities that are characteristic of those observed in the training images. It is, however, not informative for the mean or scale of the reconstruction. By applying the method to simulated data we show that the combination of multiple observations and the patch-based prior leads to much improved reconstruction quality in many different source scenarios and signal to noise regimes. We demonstrate that with the patch prior Jolideco yields superior reconstruction quality relative to alternative standard methods such as the Richardson-Lucy method. We illustrate the results of Jolideco applied to example data from the Chandra X-ray Observatory and the Fermi-LAT Gamma-ray Space Telescope. By comparing the measured width of a counts based and the corresponding Jolideco flux profile of an X-ray filament in SNR 1E 0102.2-721} we find the deconvolved width of 0.58+- 0.02 arcsec to be consistent with the theoretical expectation derived from the known width of the PSF.

Detailed atmospheric characterization of exoplanets by transmission spectroscopy requires careful consideration of stellar surface inhomogeneities induced by starspots. This effect is particularly problematic for planetary systems around M-dwarfs, and their spot properties are not fully understood. We investigated the stellar activity of the young M-dwarf K2-25 and its effect on transit observations of the sub-Neptune K2-25b. From multi-band monitoring observations of stellar brightness variability using ground-based telescopes and TESS, we found that the temperature difference between the spots and photosphere is <190 K and the spot covering fraction is <61% (2$\sigma$). We also investigated the effect of starspot activity using multi-epoch, multi-band transit observations. We rule out cases with extremely low spot temperatures and large spot covering fractions. The results suggest that spots could distort the transmission spectrum of K2-25b by as much as $\sim$100 ppm amplitude, corresponding to the precision of JWST/NIRSPEC of the target. Our study demonstrates that simultaneous multi-band observations with current instruments can constrain the spot properties of M-dwarfs with good enough precision to support atmospheric studies of young M-dwarf planets via transmission spectroscopy.

Arp 220 is the nearest ULIRG; it shows evidence of 100 pc-scale molecular outflows likely connected with galaxy-scale outflows traced by ionised and neutral gas. The two highly obscured nuclei of Arp 220 are the site of intense star formation, with extreme star-formation rate surface densities (~ 10^3 Msun/yr/kpc2). Despite extensive investigations searching for AGN activity in the Arp 220 nuclei, direct evidence remains elusive. We present JWST/NIRSpec IFS observations covering the 0.9 - 5.1 um wavelength range of the innermost (5''x4'', i.e. 1.8x1.5 kpc) regions of Arp 220. The primary goal is to investigate the potential presence of AGN signatures in the nuclear regions by analysing the spectra extracted from circular apertures of radius 55 pc (0.15'') around each of the two nuclei. We identify ~ 70 ionised and ~ 50 molecular emission lines in the nuclear spectra of Arp 220; we use recombination line ratios to measure optical extinctions in the range AV ~ 11 - 14 mag. High ionisation lines are not detected, except the [Mg IV] line at 4.49 um which we interpret as due to shocks rather than to AGN ionisation. We identify broadening and multiple kinematic components in the HI and H2 lines caused by outflows and shocks, with velocities up to ~ 550 km/s. Significantly higher velocities (up to ~ 900 km/s) are detected in the off-nuclear regions; however, they do not conclusively represent evidence for AGN activity. Even with the unprecedented sensitivity of JWST/NIRSpec IFS, achieving an unambiguous identification or exclusion of the presence of an AGN in the Arp 220 system remains challenging, because of its extreme dust obscuration.

Eta Carinae underwent the Great Eruption in the 1840s and a Lesser Eruption in the 1890s. Its apparent spectrum, modified by intervening ejecta, the Homunculus and Little Homunculus, continues to evolve but contains information pertaining to events in the 19th century. The LOS spectrum contains narrow absorption velocities, from -122 to -1665 km/s: rungs of a broken ladder caused by shells formed by the interacting winds. Estimated shell origin dates correlate with origin dates of expanding emission structures preceding the Great Eruption. The LOS absorption velocities extend the record post Great Eruption to the Lesser Eruption. We suggest that these shells originated from a binary merger within a triple system. Shells formed not only from periastron passages of the current secondary, but also from ear-like extensions preceding and following the periastron event. Additional models need to be considered.

Using mass-radius-composition models, small planets ($\mathrm{R}\lesssim 2 \mathrm{R_\oplus}$) are typically classified into three types: iron-rich, nominally Earth-like, and those with solid/liquid water and/or atmosphere. These classes are generally expected to be variations within a compositional continuum. Recently, however, Luque & Pall\'e observed that potentially Earth-like planets around M dwarfs are separated from a lower-density population by a density gap. Meanwhile, the results of Adibekyan et al. hint that iron-rich planets around FGK stars are also a distinct population. It therefore remains unclear whether small planets represent a continuum or multiple distinct populations. Differentiating the nature of these populations will help constrain potential formation mechanisms. We present the RhoPop software for identifying small-planet populations. RhoPop employs mixture models in a hierarchical framework and a nested sampler for parameter and evidence estimates. Using RhoPop, we confirm the two populations of Luque & Pall\'e with $>4\sigma$ significance. The intrinsic scatter in the Earth-like subpopulation is roughly half that expected based on stellar abundance variations in local FGK stars, perhaps implying M dwarfs have a smaller spread in the major rock-building elements (Fe, Mg, Si) than FGK stars. We apply RhoPop to the Adibekyan et al. sample and find no evidence of more than one population. We estimate the sample size required to resolve a population of planets with Mercury-like compositions from those with Earth-like compositions for various mass-radius precisions. Only 16 planets are needed when $\sigma_{M_p} = 5\%$ and $\sigma_{R_p} = 1\%$. At $\sigma_{M_p} = 10\%$ and $\sigma_{R_p} = 2.5\%$, however, over 154 planets are needed, an order of magnitude increase.

We observed the nearby and relatively understudied ultraluminous X-ray source (ULX) NGC 4190 ULX-1 jointly with NICER and NuSTAR to investigate its broadband spectrum, timing properties, and spectral variation over time. We found NGC 4190 ULX-1 to have a hard spectrum characterized by two thermal components (with temperatures ~0.25keV and ~1.6keV) and a high-energy excess typical of the ULX population, although the spectrum turns over at an unusually low energy. While no pulsations were detected, the source shows significant stochastic variability and the covariance spectrum indicates the presence of a high-energy cut-off power-law component, potentially indicative of an accretion column. Additionally, when fitting archival XMM-Newton data with a similar model, we find that the luminosity-temperature evolution of the hot thermal component follows the behavior of a super-Eddington slim disk though the expected spectral broadening for such a disk is not seen, suggesting that the inner accretion disk may be truncated by a magnetic field. Therefore, despite the lack of detected pulsations, there is tantalizing evidence for NGC 4190 ULX-1 being a candidate neutron star accretor, although further broadband observations will be required to confirm this behavior.

Young early-type HAeBe stars are still embedded in the molecular clouds in which they formed. They illuminate reflection nebulae, which shape the surrounding molecular cloud and may trigger star formation. They are therefore ideal places to search for ongoing star formation activity. NGC2023 is illuminated by the Herbig Be star HD37903. It is the most massive member of a small young cluster with about 30 PMS stars, several of which are Class I objects that still heavily accrete. It might therefore be expected that they might drive molecular outflows. We examined the whole region for outflows. We analyzed previously published APEX data to search for and characterize the outflows in the NGC2023 region. This is the first systematic search for molecular outflows in this region. Since the outflows were mapped in several CO transitions, we can determine their properties quite well. We have discovered four molecular outflows in the vicinity of NGC2023, three of which are associated with Class I objects. MIR-63, a bright mid-infrared and submillimeter Class I source, is a binary with a separation of 2.4" and drives two bipolar outflows orthogonal to each other. The large southeast-northwest outflow excites the Herbig-Haro flow HH247. MIR-73, a Class I object, which is also a far-infrared source, drives a pole-on outflow. MIR-62 is a Class II object with strong infrared excess and a luminosity of 7 Lsun. It is not detected in the far-infrared. The Class I sources have bolometric luminosities of about 20 Lsun or lower, that is, they are all low-mass stars. One other far-infrared source, MIR-75, may have powered an outflow in the past because it now illuminates an egg-shaped cavity. The four outflow sources are at a similar evolutionary stage, which suggests that their formation may have been triggered by the expanding C II region.

Persistent homology naturally addresses the multi-scale topological characteristics of the large-scale structure as a distribution of clusters, loops, and voids. We apply this tool to the dark matter halo catalogs from the Quijote simulations, and build a summary statistic for comparison with the joint power spectrum and bispectrum statistic regarding their information content on cosmological parameters and primordial non-Gaussianity. Through a Fisher analysis, we find that constraints from persistent homology are tighter for 8 out of the 10 parameters by margins of 13-50%. The complementarity of the two statistics breaks parameter degeneracies, allowing for a further gain in constraining power when combined. We run a series of consistency checks to consolidate our results, and conclude that our findings motivate incorporating persistent homology into inference pipelines for cosmological survey data.

We present an interpretation of the recent Daniel K. Inouye Solar Telescope (DKIST) observations of propagating wavefronts in the lower solar atmosphere. Using MPS/University of Chicago MHD (MURaM) radiative magnetohydrodynamic simulations spanning solar photosphere, overshoot region, and lower chromosphere, we identify three acoustic-wave source mechanisms, each occurring at a different atmospheric height. We synthesize the DKIST Visible Broadband Imager (VBI) G-band, blue-continuum, and CaIIK signatures of these waves at high spatial and temporal resolution, and conclude that the wavefronts observed by DKIST likely originate from acoustic sources at the top of the solar photosphere overshoot region and in the chromosphere proper. The overall importance of these local sources to the atmospheric energy and momentum budget of the solar atmosphere is unknown, but one of the excitation mechanism identified (upward propagating shock interaction with down-welling chromospheric plasma resulting in acoustic radiation) appears to be an important shock dissipation mechanism. Additionally, the observed wavefronts may prove useful for ultra-local helioseismological inversions and promise to play an important diagnostic role at multiple atmospheric heights.

Young massive star clusters, like the six red supergiant clusters in the Scutum complex, provide valuable insights into star-formation and galaxy structures. We investigated the high-resolution near-infrared spectra of 60 RSG candidates in these clusters using the Immersion Grating Infrared Spectrograph. Among the candidates in RSGC4, we found significant scattering in radial velocity ($-64$ km/s to $115$ km/s), unlike other clusters with velocities of $\sim$100 km/s. Most candidates in RSGC4 have $Q_{GK_s}$ values larger than 1.7, suggesting that they could be early AGB stars. Four candidates in RSGC4 exhibit infrared excess and distinct absorption features absent in other candidates. Two of these stars exhibit absorption lines resembling those of D-type symbiotic stars, showing radial velocity changes in multi-epoch observations. Analysis of relative proper motions revealed no runaway/walkaway stars in RSGC4. The dynamic properties of RSGC4 and RSGC1 differ from the disk-like motions of other clusters: RSGC4 has low normalized horizontal action $J_\mathrm{hor}=J_\mathrm{\phi}/J_\mathrm{tot}$ and vertical action $J_\mathrm{ver}=(J_\mathrm{z}-J_\mathrm{R})/J_\mathrm{tot}$ values and high eccentricities, while RSGC1 has vertical motions with high $J_\mathrm{ver}$ values and inclinations. We propose that RSGC4 may not be a genuine star cluster but rather a composite of RSGs and AGBs distributed along the line of sight at similar distances, possibly originating from various environments. Our results suggest a complex and hierarchical secular evolution of star clusters in the Scutum complex, emphasizing the importance of considering factors beyond density crowding when identifying star clusters in the bulge regions.

In this work we model stationary neutron star envelopes at high accretion rates and describe our new code for such studies. As a first step we put special emphasis on the rp-process which results in the synthesis of heavy elements and study in detail how this synthesis depends on the mass accretion rate and the chemical composition of the accreted matter. We show that at very low accretion rate, $\dot{M} \sim 0.01 \dot{M}_{\text{Edd}}$, mostly low mass ($A\leq$ 24) elements are synthesized with a few heavier ones below the $^{40}$Ca bottleneck. However, once $\dot{M}$ is above ${\buildrel \sim \over >} 0.1 \dot{M}_{\text{Edd}}$ this bottleneck is surpassed and nuclei in the iron peak region ($A\sim$ 56) are abundantly produced. At higher mass accretion rates progressively heavier nuclei are generated, reaching $A \sim 70$ at $\dot{M}_{\text{Edd}}$ and $A \sim 90$ at $5 \dot{M}_{\text{Edd}}$. We find that when the rp-process is efficient, the nucleosynthesis it generates is independent of the accreted abundance of CNO elements as these are directly and copiously generated once the $3\alpha$-reaction is operating. We also explore the efficiency of the rp-process under variations of the relative abundances of H and He. Simultaneously, we put special emphasis on the density profiles of the energy generation rate particularly at high density beyond the hydrogen exhaustion point. Our results are of importance for the study of neutron stars in systems in which X-ray bursts are absent but are also of relevance for other systems in describing the low density region, mostly below $10^6$ g cm\mmm, inbetween bursts.

The up-coming Vera Rubin Observatory's Legacy Survey of Space and Time (LSST) opens a new opportunity to rapidly survey the southern Sky at optical wavelenghts (\ie ugrizy bands). In this study, we aim to test the possibility of using LSST observations to constrain the mass and velocity of different KN ejecta components from the observation of a combined set of light curves from GRB afterglows and KN\ae. We used a sample of simulated light curves from the aforementioned events as they would have been seen during the LSST survey to study how observing strategies' choice impacts the parameters' estimation. We found that the observing strategy design to be the best compromise between light curves coverage, observed filters and fit reliability involves a high number of visits with long gap pairs of about 4 hours every 2 nights in the same or different filters. The features of the observing strategy will allow us to recognize the different stages of the light curve evolution and gather observations in at least 3 filters.

Period change studies give a window to probe into the evolution and dynamics of Cepheids. While evolutionary period changes have been well studied both observationally and theoretically, non-evolutionary period changes lack a systematic and quantitative description. The overall objective is to have a quantitative understanding of the full picture of non-evolutionary period changes in Cepheids, to develop a formalism to disentangle it from the secular evolutionary period change. In the first part of the series of works, we aim to conduct a systematic search for non-evolutionary period changes to search for Cepheids in likely binary configuration and quantify their incidence rates in the Magellanic Clouds. We collect more than decade-long time-series photometry from the publically available survey, Optical Gravitational Lensing Experiment (OGLE), with more than 7200 Cepheids collectively from the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC). Our sample contains both fundamental-mode and first overtone-mode Cepheids. Then we calculate observed minus calculated ($O-C$) diagrams to reveal the light-travel time effect (LTTE). In our search, out of an overall sample of more than 7200 Cepheids, we found 52 candidate Cepheid binary systems in the LMC (30 fundamental and 22 first overtone-mode) and 145 in the SMC (85 fundamental and 60 first overtone-mode). The majority of the sample is characterized by orbital periods of 2000-4000\,d and eccentricities of 0.2-0.5. Moreover, we report two candidates in each galaxy with the Cepheid likely existing with a giant companion. The incidence rate ratio for SMC to LMC calculated from our sample is in agreement with binary Cepheid population synthesis predictions.

Enlightening our understanding of the first galaxies responsible for driving reionisation requires detecting the 21-cm signal from neutral hydrogen. Interpreting the wealth of information embedded in this signal requires Bayesian inference. Parameter inference from the 21-cm signal is primarily restricted to the spherically averaged power spectrum (1D PS) owing to its relatively straightforward derivation of an analytic likelihood function enabling traditional Monte-Carlo Markov-Chain (MCMC) approaches. However, in recent years, simulation-based inference (SBI) has become feasible which removes the necessity of having an analytic likelihood, enabling more complex summary statistics of the 21-cm signal to be used for Bayesian inference. In this work, we use SBI, specifically marginal neural ratio estimation to learn the likelihood-to-evidence ratio with Swyft, to explore parameter inference using the cylindrically averaged 2D PS. Since the 21-cm signal is anisotropic, the 2D PS should yield more constraining information compared to the 1D PS which isotropically averages the signal. For this, we consider a mock 1000 hr observation of the 21-cm signal using the SKA and compare the performance of the 2D PS relative to the 1D PS. Additionally, we explore two separate foreground mitigation strategies, perfect foreground removal and wedge avoidance. We find the 2D PS outperforms the 1D PS by improving the marginalised uncertainties on individual astrophysical parameters by up to $\sim30-40$ per cent irrespective of the foreground mitigation strategy. Primarily, these improvements stem from how the 2D PS distinguishes between the transverse, $k_{\perp}$, and redshift dependent, $k_{\parallel}$ information which enables greater sensitivity to the complex reionisation morphology.

The detection of the 21-cm signal at $z\gtrsim6$ will reveal insights into the properties of the first galaxies responsible for driving reionisation. To extract this information, we perform parameter inference which requires embedding 3D simulations of the 21-cm signal within a Bayesian inference pipeline. Presently, when performing inference we must choose which sources of uncertainty to sample and which to hold fixed. Since the astrophysics of galaxies are much more uncertain than those of the underlying halo-mass function (HMF), we usually parameterise and model the former while fixing the latter. However, in doing so we may bias our inference of the properties of these first galaxies. In this work, we explore the consequences of assuming an incorrect choice of HMF and quantify the relative biases in our inferred astrophysical model parameters when considering the wrong HMF. We then relax this assumption by constructing a generalised five parameter model for the HMF and simultaneously recover these parameters along with our underlying astrophysical model. For this analysis, we use 21cmFAST and perform Simulation-Based Inference by applying marginal neural ratio estimation to learn the likelihood-to-evidence ratio using Swyft. Using a mock 1000 hour observation of the 21-cm power spectrum from the forthcoming Square Kilometre Array, conservatively assuming foreground wedge avoidance, we find assuming the incorrect HMF can bias the recovered astrophysical parameters by up to $\sim3-4\sigma$ even when including independent information from observed luminosity functions. When considering our generalised HMF model, we recover constraints on our astrophysical parameters with a factor of $\sim2-4$ larger marginalised uncertainties. Importantly, these constraints are unbiased, agnostic to the underlying HMF and therefore more conservative.

In 2019, Neutron star Interior Composition ExploreR (NICER) mission released its findings on the mass and radius of the isolated neutron star (INS) PSR J0030+0451, revealing a mass of approximately 1.4 solar masses ($M_{\odot}$) and a radius near 13 kilometers. However, the recent re-analysis by the NICER collaboration \citep{vinciguerra2024updated} suggests that the available data primarily yields a precise inference of the compactness for this source while the resulting mass and radius are strongly model-dependent and diverse (the 68.3\% confidence counters just overlap slightly for the ST+PDT and PDT-U models). By integrating this compactness data with the equation of state (EoS) refined by our latest investigations, we have deduced the mass and radius for PSR J0030+0451, delivering estimates of $M=1.48^{+0.09}_{-0.10}~M_\odot$ and $R=12.39_{-0.70}^{+0.50}~{\rm km}$ for the compactness found in ST+PDT model, alongside $M=1.47^{+0.14}_{-0.20}~M_\odot$ and $R=12.37_{-0.70}^{+0.50}~{\rm km}$ for the compactness in PDT-U model. These two groups of results are well consistent with each other and the direct X-ray data inference within the ST+PDT model seems to be favored. Additionally, we have calculated the tidal deformability, moment of inertia, and gravitational binding energy for this NS. Furthermore, employing these refined EoS models, we have updated mass-radius estimates for three INSs with established gravitational redshifts.

Type IIn supernovae (SNe) exhibit narrow hydrogen lines that arise from the strong interaction between ejecta and circumstellar material. It remains poorly understood, however, what progenitor stars give rise to these explosions. In this work, we perform a detailed analysis of the progenitor and environment of the nearby Type IIn SN 2010jl. With newer images taken by the Hubble Space Telescope, we confirm that the previously reported progenitor candidate is a blend of the progenitor itself and a field star cluster in its close vicinity. SN 2010jl has now become much fainter than the progenitor. The progenitor is very blue and luminous with an effective temperature of log $T_{\rm eff}/{\rm K}$=4.26$^{+0.11}_{-0.09}$ and a luminosity of log $L/L_{\odot}$ =6.52$^{+0.20}_{-0.16}$. It is located in a very young star-forming region, but its luminosity is much higher than that expected from the environmental stellar populations. We suggest that the progenitor was in outburst when observed. Its nature and evolutionary history remain to be investigated.

Young protostellar binary systems, with expected ages less than $\sim$10$^5$ years, are little modified since birth, providing key clues to binary formation and evolution. We present a first look at the young, Class 0 binary protostellar system R CrA IRAS 32 from the Early Planet Formation in Embedded Disks (eDisk) ALMA large program, which observed the system in the 1.3 mm continuum emission, $^{12}$CO (2-1), $^{13}$CO (2-1), C$^{18}$O (2-1), SO (6$_5$-5$_4$), and nine other molecular lines that trace disk, envelope, shocks, and outflows. With a continuum resolution of $\sim$0.03$^{\prime\prime}$ ($\sim$5 au, at a distance of 150 pc), we characterize the newly discovered binary system with a separation of 207 au, their circumstellar disks, and a circumbinary disk-like structure. The circumstellar disk radii are 26.9$\pm$0.3 and 22.8$\pm$0.3 au for sources A and B, respectively, and their circumstellar disk dust masses are estimated as 22.5$\pm$1.1 and 12.4$\pm$0.6 M$_{\Earth}$. The circumstellar disks and the circumbinary structure have well aligned position angles and inclinations, indicating formation in a smooth, ordered process such as disk fragmentation. In addition, the circumstellar disks have a near/far-side asymmetry in the continuum emission suggesting that the dust has yet to settle into a thin layer near the midplane. Spectral analysis of CO isotopologues reveals outflows that originate from both of the sources and possibly from the circumbinary disk-like structure. Furthermore, we detect Keplerian rotation in the $^{13}$CO isotopologues toward both circumstellar disks and likely Keplerian rotation in the circumbinary structure; the latter suggests that it is probably a circumbinary disk.

The counter-rotation between black holes and accretion disk configuration was introduced over a decade ago to elucidate the nature of the radio loud/radio-quiet dichotomy and the jet-disk connection, but has since been applied to a plethora of observations across space and time. We briefly review the paradigm in which counter-rotation is key for the triggering of radio galaxies and its observational support, then apply it to a series of observations concerning FR0 radio galaxies. FR0 radio galaxies appear to be radio galaxies in transition, with low-spinning black holes and thus weaker but tilted jets with respect to an earlier radio quasar phase. As a result, FR0 radio galaxies are prescribed to be in an earlier phase of star formation suppression in radio galaxies, compared to a later phase that is unlikely to be less than tens of millions of years in the future if they have enough accretion fuel to evolve into more powerful FRI radio galaxies. FR0 radio galaxies will have a greater or lesser star formation suppression feedback effect depending on how long they live. Tilted jets also enhance stellar velocities in the bulge. Because FR0 jet lengths are of the same order of magnitude as the radius of the stellar bulge, FR0 jets are prescribed to have begun, more or less recently depending on their age, to affect stellar velocity dispersions as well. As a result, they will be associated with dispersion values that tend to be larger than for characteristically non-jetted active galaxies, but smaller than giant radio galaxies such as M87 that have experienced a long-term tilted and more powerful FRI jet. With these ideas it is possible to make a coarse-grained prediction for the slope of the M-{\sigma} plane for FR0 radio galaxies with values between 4 and 8.

The $\beta$-skeleton approach can be conveniently utilized to construct the cosmic web based on the spatial geometry distribution of galaxies, particularly in sparse samples. This method plays a key role in establishing the three-dimensional structure of the Universe and serves as a tool for quantitatively characterizing the nature of the cosmic web. This study is the first application of $\beta$-skeleton information as weights in mark weighted correlation functions (MCFs), presenting a novel statistical measure. We have applied the $\beta$-skeleton approach to the CMASS NGC galaxy samples from SDSS BOSS DR12 in the redshift interval $0.45 \leq z \leq 0.55$. Additionally, we applied this approach to three COLA cosmological simulations with different settings ($\Omega_m=0.25, \Omega_m=0.31, \Omega_m=0.4$) for comparison. We measured three MCFs, each weighted by: i) the number of neighboring galaxies around each galaxy; ii) the average distance of each galaxy from its surrounding neighbors; iii) the reciprocal of the average distance of each galaxy from its surrounding neighbors. By comparing measurements and calculating corresponding $\chi^2$ statistics, we observe high sensitivity to the cosmological parameter $\Omega_m$ through a joint analysis of the two-point correlation and three MCFs.

We conducted a study on the X-ray polarization properties of MGC-5-23-16 by analyzing long-term monitoring data from {\it NuSTAR} jointly with {\it IXPE} observations in May and November 2022. The re-analysis of {\it IXPE} data gives model-dependent polarization degree, PD (\%) = $1.55\pm0.99$ and $1.31\pm0.95$ in the energy band $2-8$ keV, agrees with previous studies within error bars. The model-independent analysis of PD poses an upper limit of $\leq3.8$ ($1\sigma$ level) for the same energy band. The observed upper limit of PD, along with broadband spectral analysis ($3-79$ keV), allowed us to derive corona geometry (i.e. length and height) and the accretion disk inclination ($\sim 33^\circ$). Additional {\it NuSTAR} observations were also analyzed to gain insights into the accretion flow properties of the source and to estimate the expected polarization during those epochs with PD $\sim 4.3\%$. The radius and height of the corona exhibited to vary between $28.2\pm3.1 - 39.8\pm4.6$ r$_s$ and $14.3\pm1.7-21.4\pm1.9$ r$_s$, with a mass outflow rate from the corona measuring $0.14\pm0.03-0.2\pm0.03$ Eddington rate ($\dot M_{\rm Edd}$). The estimated PD values were nearly constant up to a certain radial distance and height of the corona and then decreased for increasing corona geometry. The spectral analysis further provided an estimate for the mass of the central black hole $\sim 2\times 10^7$ M$_\odot$ and the velocity of the outflowing gas $\sim 0.16-0.19c$. Our modeling of the disk-corona-outflows and polarization connection can be extended and validated with data from recently launched India's first X-ray Polarimeter Satellite, offering potential applications to other sources.

A recently reported gravito-electrostatic sheath (GES) model is procedurally applied to study the turbumagnetoactive helioseismic oscillation features on the entire bi-fluidic solar plasma system. The bounded solar interior plasma (SIP, internally self-gravitating) and the unbounded solar wind plasma (SWP, externally point-gravitating) are coupled through the interfacial diffused solar surface boundary (SSB) due to an exact gravito-electrostatic interplay. A numerical platform on the developed theoretic formalism reveals the evolution of both dispersive and non-dispersive features of the modified GES mode fluctuations in new parametric windows. Different colourspectral profiles exhibit important features of the GES-based SIP-SWP perturbations elaborately. It is illustratively shown that the thermostatistical GES stability depends mainly on the radial distance, magnetic field, equilibrium plasma density, and plasma temperature. We see that their dispersive features are more pertinently pronounced in the self-gravitational domains (SIP) than the electrostatic ones (SWP). Besides, different characteristic parameters with accelerating (or decelerating) and stabilizing (or destabilizing) effects influencing the entire solar plasma stability are illustratively portrayed. We speculate that, in the SIP, the long-wave (gravitational-like) helioseismic fluctuations become highly dispersive showing more propagatory nature than the shorter ones (acoustic-like). The short waves show more propagatory propensity than the longer ones in the SSB and SWP regime. The reliability of our proposed investigation is bolstered along with the tentative applicability and future scope in light of the current solar observational scenarios, such as SOHO, STEREO, SDO, PSP, and SolO.

A fundamental goal of astrobiology is to detect life outside of Earth. This proves to be an exceptional challenge outside of our solar system, where strong assumptions must be made about how life would manifest and interact with its planet. Such assumptions are required because of the lack of a consensus theory of living systems, or an understanding of the possible extent of planetary dynamics. Here we explore a model of life spreading between planetary systems via panspermia and terraformation. Our model shows that as life propagates across the galaxy, correlations emerge between planetary characteristics and location, and can function as a population-scale agnostic biosignature. This biosignature is agnostic because it is independent of strong assumptions about any particular instantiation of life or planetary characteristic--by focusing on a specific hypothesis of what life may do, rather than what life may be. By clustering planets based on their observed characteristics, and examining the spatial extent of these clusters, we demonstrate (and evaluate) a way to prioritize specific planets for further observation--based on their potential for containing life. We consider obstacles that must be overcome to practically implement our approach, including identifying specific ways in which better understanding astrophysical and planetary processes would improve our ability to detect life. Finally, we consider how this model leads us to think in novel ways about hierarchies of life and planetary scale replication.

We conduct an asteroseismological analysis on the non-Blazhko ab-type RR Lyrae star EPIC 248846335 employing the Radial Stellar Pulsations (RSP) module of the Modules for Experiments in Stellar Astrophysics (MESA) based on the set of stellar parameters. The atmospheric parameters as $T_\mathrm{eff}$ = 6933$\pm$70 $K$, log $g$ = 3.35$\pm$ 0.50 and [Fe/H] = -1.18 $\pm$ 0.14 are estimated from the Low-Resolution Spectra of LAMOST DR9. The luminosity $L$ = 49.70$_{-1.80}^{+2.99}$ $L_\odot$ and mass M = 0.56 $\pm$ 0.07 $M_\odot$ are calculated, respectively, using the distance provided by Gaia and the metallicity estimated from the Low-Resolution Spectra. The Fourier parameters of the light curves observed by $K2$ and RV curves determined from the Medium-Resolution Spectra of LAMOST DR10 are also calculated in this work. The period of the fundamental mode of the star and the residuals $r$ of the Fourier parameters between the models and observations serve to select optimal model, whose stellar parameters are $T_\mathrm{eff}$ = 6700 $\pm$ 220 K, log $g$ = 2.70, [Fe/H] = -1.20 $\pm$ 0.2, M = 0.59 $\pm$ 0.05 $M_\odot$, and $L$ = 56.0 $\pm$ 4.2 $L_\odot$. The projection factors are constrained as 1.20 $\pm$ 0.02 and 1.59 $\pm$ 0.13 by the blue- and red-arm observed velocities with their corresponding RV curves derived from the best-fit model, respectively. The precise determination of stellar parameters in ab-type RR Lyrae stars is crucial for understanding the physical processes that occur during pulsation and for providing a deeper understanding of its Period-Luminosity relationship.

We study the evolution of the dark energy equation of the state parameter without tying ourselves to any specific cosmological model or parametrization except spatial homogeneity, isotropy, and flatness leading to a flat Friedmann-Lema\^itre-Robertson-Walker (FLRW) metric. Instead, we rely on actual observational data to guide our analysis. This is the first study in which we combine the cosmological background and the growth observations to reconstruct the equation of the state parameter of dark energy independent of the present values of the matter-energy density parameter and Hubble parameter. We use information about the Hubble parameter from cosmic chronometer data and the growth rate from observations related to growth rates. Our method involves a posterior approach of Gaussian process regression analysis to figure out the Hubble parameter and growth rate, plus their changes with redshift. The significant shift of paradigm in this study lies in the independence of the reconstruction of the dark energy equation of state from any prior knowledge of the present Hubble parameter and matter energy density parameter. We find a slight hint of dynamical behavior in dark energy. However, the evidence is not significant. We also find a leaning towards non-phantom behavior over phantom behavior. Intriguingly, we observe that the $\Lambda$CDM model nearly touches the lower boundary of the 1$\sigma$ confidence region for the reconstructed dark energy equation of state parameter in the redshift range $0.6 \lesssim z \lesssim 0.85$. However, it comfortably resides within the 1$\sigma$ confidence region in the redshift range under investigation, $0\leq z \leq 1.5$. Consequently, the non-parametric, model-independent reconstruction of dark energy provides no compelling evidence to deviate from the $\Lambda$CDM model when considering cosmic chronometer and growth rate observations.

We analyze the outer regions of M33, beyond 15 kpc in projected distance from its center using Subaru/HSC multi-color imaging. We identify Red Giant Branch (RGB) stars and Red Clump (RC) stars using the surface gravity sensitive $NB515$ filter for the RGB sample, and a multi-color selection for both samples. We construct the radial surface density profile of these RGB and RC stars, and find that M33 has an extended stellar population with a shallow power-law index of $\alpha > -3$. This result represents a flatter profile than the stellar halo which has been detected by the previous study focusing on the central region, suggesting that M33 may have a double-structured halo component, i.e. inner/outer halos or a very extended disk. Also, the slope of this extended component is shallower than those typically found for halos in large galaxies, implying intermediate-mass galaxies may have different formation mechanisms (e.g., tidal interaction) from large spirals. We also analyze the radial color profile of RC/RGB stars, and detect a radial gradient, consistent with the presence of an old and/or metal-poor population in the outer region of M33, thereby supporting our proposal that the stellar halo extends beyond 15 kpc. Finally, we estimate that the surface brightness of this extended component is $\mu_{\it V} = 35.72 \pm 0.08$ mag arcsec$^{-2}$. If our detected component is the stellar halo, this estimated value is consistent with the detection limit of previous observations.

We present source detection and catalogue construction pipelines to build the first catalogue of radio galaxies from the 270 $\rm deg^2$ pilot survey of the Evolutionary Map of the Universe (EMU-PS) conducted with the Australian Square Kilometre Array Pathfinder (ASKAP) telescope. The detection pipeline uses Gal-DINO computer-vision networks (Gupta et al., 2024) to predict the categories of radio morphology and bounding boxes for radio sources, as well as their potential infrared host positions. The Gal-DINO network is trained and evaluated on approximately 5,000 visually inspected radio galaxies and their infrared hosts, encompassing both compact and extended radio morphologies. We find that the Intersection over Union (IoU) for the predicted and ground truth bounding boxes is larger than 0.5 for 99% of the radio sources, and 98% of predicted host positions are within $3^{\prime \prime}$ of the ground truth infrared host in the evaluation set. The catalogue construction pipeline uses the predictions of the trained network on the radio and infrared image cutouts based on the catalogue of radio components identified using the Selavy source finder algorithm. Confidence scores of the predictions are then used to prioritize Selavy components with higher scores and incorporate them first into the catalogue. This results in identifications for a total of 211,625 radio sources, with 201,211 classified as compact and unresolved. The remaining 10,414 are categorized as extended radio morphologies, including 582 FR-I, 5,602 FR-II, 1,494 FR-x (uncertain whether FR-I or FR-II), 2,375 R (single-peak resolved) radio galaxies, and 361 with peculiar and other rare morphologies. We cross-match the radio sources in the catalogue with the infrared and optical catalogues, finding infrared cross-matches for 73% and photometric redshifts for 36% of the radio galaxies.

Many previous studies have explored models of dynamically interacting dark energy scenarios instead of a cosmological constant and cold dark matter. This work aims to offer a comprehensive investigation of the Yukawa-type interaction between dark energy and dark matter where dark matter mass is also a function of a dynamical scalar field value. Unlike previous work, instead of taking an approximate solution, we numerically solve the Klein-Gordon equation that governs the intricate interplay between these two components of the dark sector along with the corresponding perturbations, using a suitable shooting algorithm to determine precise initial conditions. We have conducted a thorough analysis of this interaction using the Markov Chain Monte Carlo method, incorporating diverse datasets such as Planck, BAO, Pantheon+, and SH$_0$ES. Our results, for the first time, reveal a discernible detection of the coupling constant, which encapsulates the strength of the dark sector interaction. We find non-zero $\beta$ values of 0.0487, 0.0680, 0.0712, and 0.0822 ($68\%$ Confidence Limit) corresponding to the inclusion of each dataset, respectively. Notably, the addition of SH$_0$ES data led to a significant increase in the prominence of $\beta$, suggesting the potential for new physics in the dark sector. This study serves as a strategic road map for future endeavours with non-linear cosmology, which will contribute to an enhanced understanding and refinement of constraints on the dark sector interaction.

In this study, we report a discovery from XMM-Newton, which involves the identification and subsequent examination of a newly discovered polar-type cataclysmic variable named XMM J152737.4-205305.9. The discovery was made by matching the XMM-Newton data archive with the cataclysmic variable candidate catalog provided by Gaia Data Release 3. The utilization of X-ray photometry has led to the identification of two distinct dips that exhibit a recurring pattern with a precise period of 112.4(1) minutes in two XMM-Newton observations that are one year apart. The data obtained from the photometry of Zwicky Transient Facility (ZTF) and ATLAS surveys consistently indicate the presence of the different mass accretion states of up to 2 mag. Following the optical data, the \textit{SRG}(Spectrum Roentgen Gamma)/eROSITA All Sky Survey observed the system in two different X-ray levels which may imply different accretion states. Following these observations, the low-resolution spectrum obtained using SALT spectroscopy exposes the prominent hydrogen Balmer and helium emission lines, strongly supporting that the system belongs to the category of polar-type magnetic cataclysmic variable. The XMM-Newton observations, conducted under various conditions of X-ray levels, reveal a consistent pattern of a deep dip-like feature with a width of $\approx 9.1$ min. This feature implies the presence of an eclipse in both observations. According to Gaia data, the object is located at a distance of $1156^{+720}_{-339}$,pc, and its X-ray luminosity lies within the $L_{\rm X}$= (3-6)$\times10^{31}$ \lergs range.

Context. Blazar flares provide a window into the extreme physical processes occurring in relativistic outflows. Most numerical codes used for modeling blazar emission during flares utilize a simplified continuous-loss description of particle cooling due to the inverse Compton (IC) process, neglecting non-continuous (discrete) effects that arise in the Klein-Nishina (KN) regime. The significance of such effects has not been explored in detail yet. Aims. In this study, we investigate the importance of non-continuous Compton cooling losses and their impact on the electron spectrum and spectral energy distribution (SED) of blazars during high flux states (flares), as well as in the low state. Methods. We solve numerically the full transport equation accounting for large relative jumps in energy, by extending our existing blazar flare modeling code EMBLEM. We perform a detailed physical modeling of the brightest gamma-ray flare of the archetypal Flat Spectrum Radio Quasar (FSRQ) 3C 279 detected in June 2015. We then compare results obtained using the full cooling term and using the continuous-loss approximation. Results. We show that during flaring states of FSRQs characterized by high Compton dominance, the non-continuous cooling can lead to a significant modification of the electron spectrum, introducing a range of distinct features, such as low-energy tails, hardening/softening, narrow and extended particle excesses, and shifts in the cooling break position. Such distortion translates to differences in the associated SED up to 50%. This highlights the importance of non-continuous effects and the need to consider them in blazar emission models, particularly applied to extreme gamma-ray flares.

The poorly studied variable star V390 Sco, previously classified as a Mira pulsator, was detected in a brightening event by the ESA Gaia satellite in September 2023. This work presents an analysis of available archival multifrequency photometric data of this target, along with our spectroscopic observations. Our findings lead to the conclusion that V390 Sco is a new symbiotic star identified by Gaia, currently undergoing a classical symbiotic outburst. Additionally, we uncovered three prior outbursts of this system through archival photometry. The outbursts recur approximately every 2330 - 2400 days, and we hypothesize the periastron passage in an eccentric orbit may trigger them, similarly to the case of BX Mon, DD Mic, or MWC 560. A detailed investigation into the nature of the donor star suggested that V390 Sco is an S-type symbiotic star, likely hosting a less evolved, semiregularly pulsating giant donor, but not a Mira variable.

Yellow Hypergiants (YHGs) are massive stars that are commonly interpreted to be in a post-red supergiant evolutionary state. These objects can undergo outbursts on timescales of decades, which are suspected to be due to instabilities in the envelope. To test this conjecture, the stability of envelope models for YHGs with respect to infinitesimal, radial perturbations is investigated. Violent strange mode instabilities with growth rates in the dynamical regime are identified if the luminosity to mass ratio exceeds $\approx 10^4$ in solar units. For the observed parameters of YHGs we thus predict instability. The strange mode instabilities persist over the entire range of effective temperatures from red to blue supergiants. Due to short thermal timescales and dominant radiation pressure in the envelopes of YHGs, a nonadiabatic stability analysis is mandatory and an adiabatic analysis being the basis of the common perception is irrelevant. Contrary to the prevailing opinion, the models considered here do not exhibit any adiabatic instability.

Our ability to trace the star-forming molecular gas is important to our understanding of the Universe. We can trace this gas using CO emission, converting the observed CO intensity into the H$_2$ gas mass of the region using the CO-to-H$_2$ conversion factor Xco. In this paper, we use simulations to study the conversion factor and the molecular gas within galaxies. We analysed a suite of simulations of isolated disc galaxies, ranging from dwarfs to Milky Way-mass galaxies, that were run using the FIRE-2 subgrid models coupled to the CHIMES non-equilibrium chemistry solver. We use the non-equilibrium abundances from the simulations, and we also compare to results using abundances assuming equilibrium, which we calculate from the simulation in post-processing. Our non-equilibrium simulations are able to reproduce the relation between CO and H$_2$ column densities, and the relation between Xco and metallicity, seen within observations of the Milky Way. We also compare to the xCOLD GASS survey, and find agreement with their data to our predicted CO luminosities at fixed star formation rate. We also find the multivariate function used by xCOLD GASS overpredicts the H$_2$ mass for our simulations, motivating us to suggest an alternative multivariate function of our fitting, though we caution that this fitting is uncertain due to the limited range of galaxy conditions covered by our simulations. We also find that the non-equilibrium chemistry has little effect on the conversion factor (<5\%) for our high-mass galaxies, though still affects the H$_2$ mass and Lco by $\approx$25\%.

Supernova (SN) 1987A offers a unique opportunity to study how a spatially resolved SN evolves into a young supernova remnant (SNR). We present and analyze Hubble Space Telescope (HST) imaging observations of SN 1987A obtained in 2022 and compare them with HST observations from 2009 to 2021. These observations allow us to follow the evolution of the equatorial ring (ER), the rapidly expanding ejecta, and emission from the center over a wide range in wavelength from 2000 to 11 000 AA. The ER has continued to fade since it reached its maximum ~8200 days after the explosion. In contrast, the ejecta brightened until day ~11000 before their emission levelled off; the west side brightened more than the east side, which we attribute to the stronger X-ray emission by the ER on that side. The asymmetric ejecta expand homologously in all filters, which are dominated by various emission lines from hydrogen, calcium, and iron. From this overall similarity, we infer the ejecta are chemically well-mixed on large scales. The exception is the diffuse morphology observed in the UV filters dominated by emission from the Mg II resonance lines that get scattered before escaping. The 2022 observations do not show any sign of the compact object that was inferred from highly-ionized emission near the remnant's center observed with JWST. We determine an upper limit on the flux from a compact central source in the [O III] HST image. The non-detection of this line indicates that the S and Ar lines observed with JWST originate from the O free inner Si - S - Ar rich zone and/or that the observed [O III] flux is strongly affected by dust scattering.

We show that Global Navigation Satellite Systems (GNSS) and gravimeters on Earth and in space can potentially offer the most accurate direct measurement of local density of near-Earth asteroid-mass Primordial Black Holes (PBHs) and Dark Matter (DM) clumps in the solar system by means of gravitational influence. Using semi-analytical methods and Monte Carlo simulation, this paper revisits the analysis of the trajectories of DM clumps in the solar system, including both captured objects and hyperbolic trajectories. A link is thus made between the frequency and distance of Earth overflights for a given mass flux, and a direct measure of dark matter clump density in the solar system. We then model the signature of a close flyby of a DM object on orbital data from GNSS satellites and gravity measurements from gravimeters. We thus obtain a first assessment of the single probe sensitivity. It paves the way for an exhaustive statistical analysis of 28 years of gravimeters and GNSS data to obtain observational constraints on the density of the PBHs and DM clumps within the solar system, for the mass range $[10^8-10^{17}]$ kg. In addition, our methodology offers a possibility of direct detection in cases where DM clumps are endowed with an additional long-range clump-matter fifth-force beyond gravity.

For many years, it has been claimed that the Galactic ridge X-ray emission at the Galactic Center (GC) is truly diffuse in nature. However, with the advancement of modern X-ray satellites, it has been found that most of the diffuse emission is actually comprised of thousands of previously unresolved X-ray point sources. Further, many studies suggest that a vast majority of these X-ray point sources are magnetic cataclysmic variables (mCVs) and active binaries. One unambiguous way to identify these mCVs and other sources is by detecting their X-ray periodicity. Therefore, we systematically searched for periodic X-ray sources in the inner Galactic disk, including the GC region. We have used data from our ongoing XMM-Newton Heritage survey of the inner Galactic disk ($350^{\circ}\lesssim l\lesssim+7^{\circ}$ and $-1^{\circ}\lesssim b\lesssim +1^{\circ}$) plus the XMM-Newton archival observations of the GC. We computed the Lomb-Scargle periodogram of the light curves for the periodicity search. We fitted the energy spectra of the sources using a simple power-law model plus three Gaussians at 6.4, 6.7, and 6.9 keV for the iron $K$ emission complex. We detected periodicity in 26 sources. For 14 of them, this is the first discovery of periodicity. For the other 12 sources, we found periods similar to those already known, indicating no significant period evolution. We also searched for the Gaia counterparts of the periodic sources to estimate their distances using the Gaia parallax. We found a likely Gaia counterpart for seven sources. We have classified the sources into four categories based on the periodicity, hardness ratio, and the equivalent width of Fe $K$ line emission. Of the 14 sources where we detect the periodicity for the first time, four are likely to be intermediate polars, five are likely to be polars, two are neutron star X-ray binaries, and three are of unknown nature.

The physical parameters of the sunspot are not fully understood, especially the height dependence of the magnetic field. So far, it is also an open question as to which heights the He I 1083 nm spectral line is formed at. Our aim is to investigate the magnetic and dynamical properties in the atmosphere above a sunspot, from the photosphere to the chromosphere. We analyzed the photospheric and chromospheric magnetic field properties of a stable sunspot in AR 12553 on June 20, 2016 using spectropolarimetric observations obtained with GRIS at GREGOR. A spectral-line inversion technique was used to infer the magnetic field vector and Doppler velocities from the full Stokes profiles. In total, three spectral lines were inverted and the variation of the magnetic properties was qualified using the average values of the radial circles. The sunspot is located close to the solar limb, and thus this allows us to make a geometrical determination of the height of the spectral line He I 1083 nm. We find the height of helium spectral line to be 970 km above the photospheric spectral lines directly from observation at a stable sunspot. The total magnetic field strength decreases with height over the sunspot; the rates are -0.34 G/km for the umbra and -0.28 G/km for the penumbra. The inclination increases with increasing height in the umbra, but decreases in the penumbra. In the umbra, the vertical component ($B_z$) decreases with height, while the horizontal component ($B_{hor}$) remains almost constant. In the penumbra this is reversed, as $B_z$ remains nearly constant over height, while $B_{hor}$ decreases. We also observe fast velocities with 30 km/s in small chromospheric patches on the central side of the spot. The key parameters depending on height in the sunspot are the $B_{z}$ component of the magnetic field for the umbra and the $B_{hor}$ component of the magnetic field for the penumbra.

The current literature is rather vague regarding how to calculate the exact numerical value of the resonant ion scattering cross-section that should be used for a specific bandpass of finite width. Such a value was needed in order to calculate the ion and mass densities in the shock fronts of hot, close binary star systems. This was done based on a modeling of ultraviolet wind-line profiles, using IUE spectra. Therefore, a numerical integration has been carried out, in wavelength-space, of the exact expression for the cross-section over two band-passes of astrophysical interest. The exact expression employed was that derived from a solution of the Abraham-Lorentz equation. The numerical results depend on the resonant wavelength, which is taken to be at the center of the bandpass. Most texts on the subject derive an expression for the scattering cross-section in frequency-space, based on the assumption that the radiation reaction term in the Abraham-Lorentz equation may be approximated by a resistive term. The integral of this cross-section over the entire spectrum is independent of the resonant frequency, except for the transition probability. This has limited practical use when dealing with fluxes measured in a bandpass of finite width expressed in wavelength units and scattering is the only mechanism for producing the observed fluxes. Such is the case when dealing with the low densities encountered in stellar winds and shock fronts. Integrated cross-sections that depend on the resonant wavelength are used to determine the number and mass densities of C IV and N V ions in the shock fronts found in some hot, eclipsing binary star systems, for which several IUE spectra have been obtained over a Keplerian orbital period. This then leans to a determination of the mass density and total mass in the shock once the volume of the shock is determined.

The in-in formalism provides a way to systematically organize the calculation of primordial correlation functions. Although its theoretical foundations are now firmly settled, the treatment of total time derivative interactions, incorrectly trivialized as ``boundary terms'', has been the subject of intense discussions and conceptual mistakes. In this work, we demystify the use of total time derivatives -- as well as terms proportional to the linear equations of motion -- and show that they can lead to artificially large contributions cancelling at different orders of the in-in operator formalism. We discuss the treatment of total time derivative interactions in the Lagrangian path integral formulation of the in-in perturbation theory, and we showcase the importance of interaction terms proportional to linear equations of motion. We then provide a new route to the calculation of primordial correlation functions, which avoids the generation of total time derivatives, by working directly at the level of the full Hamiltonian in terms of phase-space variables. Instead of integrating by parts, we perform canonical transformations to simplify interactions. We explain how to retrieve correlation functions of the initial phase-space variables from the knowledge of the ones after canonical transformations, and we provide diagrammatic rules to systematically classify all possible contributions. As an important first application, we find the explicit sizes of Hamiltonian cubic interactions in single-field inflation with canonical kinetic terms and for any background evolution [...]. Our results are important for performing complete calculations of exchange diagrams in inflation [...]. Being already written in a form amenable to characterize quantum properties of primordial fluctuations, they also promise to shed light on the non-linear dynamics of quantum states during inflation.

The cosmological principle posits that the universe is statistically homogeneous and isotropic on large scales, implying all matter share the same rest frame. This principle suggests that velocity estimates of our motion from various sources should agree with the cosmic microwave background (CMB) dipole's inferred velocity of 370 km/s. Yet, for over two decades, analyses of different radio galaxy and quasar catalogs have reported velocities with amplitudes in notable tension with the CMB dipole. In a blind analysis of BOSS and eBOSS spectroscopic data from galaxies and quasars across $0.2<z<2.2$, we applied a novel dipole estimator for a tomographic approach, robustly correcting biases and quantifying uncertainties with state-of-the-art mock catalogs. Our results, indicating a velocity of $v = 353^{+123}_{-111}$ km/s, closely align with the CMB dipole, demonstrating a $1.4\sigma$ agreement. This finding provides significant empirical support for the cosmological principle, affirming our motion's consistency with the CMB across vast cosmic distances.

We present the formation of quasi-periodic cool spicule-like jets in the solar atmosphere using 2.5-D numerical simulation in two-fluid regime (ions+neutrals) under the presence of thermal conduction and ion-neutral collision. The non-linear, impulsive Alfv\'enic perturbations at the top of the photosphere trigger field aligned magnetoacoustic perturbations due to ponderomotive force. The transport of energy from Alfv\'en pulse to such vertical velocity perturbations due to ponderomotive force is considered as an initial trigger mechanism. Thereafter, these velocity perturbations steepen into the shocks followed by quasi-periodic rise and fall of the cool jets transporting mass in the overlying corona.

Isolated black holes (BHs) and neutron stars (NSs) are largely undetectable across the electromagnetic spectrum. For this reason, our only real prospect of observing these isolated compact remnants is via microlensing; a feat recently performed for the first time. However, characterisation of the microlensing events caused by BHs and NSs is still in its infancy. In this work, we perform N-body simulations to explore the frequency and physical characteristics of microlensing events across the entire sky. Our simulations find that every year we can expect $88_{-6}^{+6}$ BH, $6.8_{-1.6}^{+1.7}$ NS and $20^{+30}_{-20}$ stellar microlensing events which cause an astrometric shift larger than 2~mas. Similarly, we can expect $21_{-3}^{+3}$ BH, $18_{-3}^{+3}$ NS and $7500_{-500}^{+500}$ stellar microlensing events which cause a bump magnitude larger than 1~mag. Leveraging a more comprehensive dynamical model than prior work, we predict the fraction of microlensing events caused by BHs as a function of Einstein time to be smaller than previously thought. Comparison of our microlensing simulations to events from in Gaia finds good agreement. Finally, we predict that in the combination of Gaia and GaiaNIR data there will be $14700_{-900}^{+600}$ BH and $1600_{-200}^{+300}$ NS events creating a centroid shift larger than 1~mas and $330_{-120}^{+100}$ BH and $310_{-100}^{+110}$ NS events causing bump magnitudes $< -1$. Of these, $<10$ BH and $5_{-5}^{+10}$ NS events should be detectable using current analysis techniques. These results inform future astrometric mission design, such as GaiaNIR, as they indicate that, compared to stellar events, there are fewer observable BH events than previously thought.

Jets and outflows are the early signposts of stellar birth. Using the UKIRT Wide Field Infrared Survey for H2 (UWISH2) at 2.12 micron, 127 outflows are identified in molecular cloud complexes Vulpecula OB1 and IRDC G53.2 covering 12 square degrees of the Galactic plane. Using multi-wavelength datasets, from 1.2 to 70 micron, 79 young stellar objects (YSOs) are proposed as potential driving sources, where, $\sim$ 79% are likely Class 0/I protostars, 17% are Class II YSOs and the remaining 4% are Class III YSOs. The outflows are characterized in terms of their length, flux, luminosity and knot-spacing. The identified outflows have a median lobe length of 0.22 pc and 0.17 pc for outflows in Vulpecula OB1 and IRDC G53.2, respectively. Our analysis, from the knot spacing, reveals a typical ejection frequency of $\sim$ 1.2 kyr suggesting an intermediate type between the FU-Ori and EX-Ori type of eruptions in both cloud complexes. Furthermore, the physical parameters of the driving sources are obtained by performing radiative transfer modelling to the observed spectral energy distributions (SEDs), which suggest that the outflows are driven by intermediate mass stars. Various observed trends between the outflow properties and the corresponding driving sources, and various interesting outflows and star forming sites, including sites of triggered star formation and protocluster forming clump with clusters of jets, are discussed. The obtained results and the identified jet-bearing protostellar sample will pave the way to understand many aspects of outflows with future high-resolution observations.

The redshifted 21-cm signal from the Cosmic Dawn and Epoch of Reionization carries invaluable information about the cosmology and astrophysics of the early Universe. Analyzing the data from a sky-averaged 21-cm signal experiment typically involves navigating through an intricate parameter space to accurately address various factors such as foregrounds, beam uncertainties, ionospheric distortions, and receiver noise for the search of the cosmological 21-cm signal. The traditional likelihood-based sampling methods for modeling these effects could become computationally demanding for such highly complex models, which makes it infeasible to include physically motivated 21-cm signal models in the analysis. Moreover, the inference with these traditional methods is driven by the assumed functional form of the likelihood function. This work demonstrates how Simulation-Based Inference through Truncated Marginal Neural Ratio Estimation (TMNRE) can naturally handle these issues at a significantly reduced computational cost than the likelihood-based methods. We estimate the posterior distribution on our model parameters with TMNRE for simulated mock observations, composed of beam-weighted foregrounds, physically motivated 21-cm signal, and radiometric noise. We find that maximizing the information content by simultaneously analyzing the data from multiple time slices and antennas significantly improves the parameter constraints and leads to a better exploration of the cosmological signal. We discuss the application of TMNRE for the current configuration of the REACH experiment and demonstrate how it can be utilized to explore potential avenues for REACH. The method presented here can be easily generalized for any sky-averaged 21-cm signal experiment.

This paper simplifies the induced four-dimensional gravitational equations originating from a five-dimensional bulk within the framework of Nash's embeddings, incorporating them into a well-known $\mu-\Sigma$ modified gravity (MG) parametrization. By leveraging data from Planck Public Release 4 (PR4), BICEP/Keck Array 2018, Planck cosmic microwave background lensing, and baryon acoustic oscillation observations, we establish a stringent lower limit for the tensor-to-scalar ratio parameter: $r < 0.0303$ at a confidence level (CL) of 95\%. This finding suggests the presence of extrinsic dynamics influencing standard four-dimensional cosmology. Notably, this limit surpasses those typically obtained through Bayesian analysis using Markov Chain Monte Carlo (MCMC) techniques, which yield $r<0.038$, or through the frequentist profile likelihood method, which yields $r<0.037$ at 95\% CL.

When gravitational waves pass near a gravitating object, they are deflected, or lensed. If the object is massive, such that the wavelength of the waves is small compared to its gravitational size, lensed gravitational wave events can be identified when multiple signals are detected at different times. However, when the wavelength is long, wave-optics diffraction effects will be important, and a lensed event can be identified by looking for frequency-dependent modulations to the gravitational waveform, without having to associate multiple signals. For current ground-based gravitational wave detectors observing stellar-mass binary compact object mergers, wave-optics effects are important for lenses with masses $\lesssim 1000 M_{\odot}$. Therefore, minihalos below this mass range could potentially be identified by lensing diffraction. The challenge with analyzing these events is that the frequency-dependent lensing modulation, or the amplification factor, is prohibitively expensive to compute for Bayesian parameter inference. In this work, we use a novel time-domain method to construct interpolators of the amplification factor for the Navarro-Frenk-White (NFW), generalized singular isothermal sphere (gSIS) and cored isothermal sphere (CIS) lens models. Using these interpolators, we perform Bayesian inference on gravitational-wave signals lensed by minihalos injected in mock detector noise, assuming current sensitivity of ground-based detectors. We find that we could potentially identify an event when it is lensed by minihalos and extract the values of all lens parameters in addition to the parameters of the GW source. All of the methods are implemented in Glworia, the accompanying open-source Python package, and can be generalized to study lensed signals detected by current and next-generation detectors.

Particle decays are always accompanied by the emission of graviton quanta of gravity through bremsstrahlung processes. However, the corresponding branching ratio is suppressed by the square of the ratio of particle's mass to the Planck scale. The resulting present abundance of gravitational waves (GWs), composed of gravitons, is analogously suppressed. We show that superheavy particles, as heavy as the Planck scale, can be naturally produced during the post-inflationary reheating stage in the early Universe and their decays yield dramatic amounts of GWs over broad frequency range. GW observations could hence directly probe Planck-scale physics, notoriously challenging to explore.

Sun-like stars can transmute into comparable mass black holes by steadily accumulating heavy non-annihilating dark matter particles over the course of their lives. If such stars form in binary systems, they could give rise to quasi-monochromatic, persistent gravitational waves, commonly known as continuous gravitational waves, as they inspiral towards one another. We demonstrate that next-generation space-based detectors, e.g., Laser Interferometer Space Antenna (LISA) and Big Bang Observer (BBO), can provide novel constraints on dark matter parameters (dark matter mass and its interaction cross-section with the nucleons) by probing gravitational waves from transmuted Sun-like stars that are in close binaries. Our projected constraints depend on several astrophysical uncertainties, nevertheless, are competitive with the existing constraints obtained from cosmological measurements as well as terrestrial direct searches, demonstrating a notable science-case for these space-based gravitational wave detectors as probes of particle dark matter.

We present a new inference framework for neutron star astrophysics based on conditional variational autoencoders. Once trained, the generator block of the model reconstructs the neutron star equation of state from a given set of mass-radius observations. While the pressure of dense matter is the focus of the present study, the proposed model is flexible enough to accommodate the reconstructing of any other quantity related to dense matter equation of state. Our results show robust reconstructing performance of the model, allowing to make instantaneous inference from any given observation set. The present framework contrasts with computationally expensive evaluation of the equation-of-state posterior probability distribution based on Markov chain Monte Carlo methods.

It has been recently proposed that Hawking evaporation might slow down after a black hole has lost about half of its mass. Such an effect, called "memory burden", is parameterized as a suppression in the mass loss rate by negative powers $n$ of the black hole entropy and could considerably extend the lifetime of a black hole. We study the impact of memory burden on the Primordial Black Hole (PBH) reheating scenario. Modified PBH evaporation leads to a significantly longer PBH dominated stage. Requiring that PBHs evaporate prior enough to Big Bang Nucleosynthesis shrinks the allowed PBH mass range. Indeed, we find that for $n>2.5$ the PBH reheating scenario is not viable. The frequency of the Gravitational Waves (GWs) induced by PBH number density fluctuations is bound to be larger than about a Hz, while the amplitude of the GW spectrum is enhanced due to the longer PBH dominated phase. Interestingly, we show that, in some models, the slope of the induced GW spectrum might be sensitive to the modifications to Hawking evaporation, proving it may be possible to test the "memory burden" effect via induced GWs. Lastly, we argue that our results could also apply to general modifications of Hawking evaporation.

In this work, we explore the properties and shadows of spin-induced scalarized black holes, as well as investigate how a Ricci coupling influences them. Our findings reveal significant deviations from the Kerr metric in terms of the location and geodesic frequencies of the innermost stable circular orbit and light ring, with the former exhibiting more pronounced disparities. The shadows of scalarized black holes exhibit relatively minor deviations when compared to those of Kerr black holes with the same mass and spin. Overall, the presence of a Ricci coupling is observed to mitigate deviations from the Kerr metric.