Papers for Wednesday, Nov 17 2021

CO-SLIDAR is a very promising technique for the metrology of near ground $C_n^2$ profiles. It exploits both phase and scintillation measurements obtained with a dedicated wavefront sensor and allows profiling on the full line of sight between pupil and sources. This technique is applied to an associated instrument based on a mid-IR Shack-Hartmann wavefront sensor, coupled to a 0.35 m telescope, which observes two cooperative sources. This paper presents the first comprehensive description of the CO-SLIDAR method in the context of near ground optical turbulence metrology. It includes the presentation of the physics principles underlying the measurements, of our unsupervised $C_n^2$ profile reconstruction strategy together with the error bar estimation on the reconstructed values. The application to data acquired in a heterogeneous rural landscape during an experimental campaign in Lannemezan (France) demonstrates the ability to obtain profiles with a sampling pitch of about 220 m over a 2.7 km line of sight. The retrieved $C_n^2$ profiles are presented and their variability in space and time is discussed.

The detection of life beyond Earth is an ongoing scientific endeavour, with profound implications. One approach, known as the search for extraterrestrial intelligence (SETI), seeks to find engineered signals (`technosignatures') that indicate the existence technologically-capable life beyond Earth. Here, we report on the detection of a narrowband signal-of-interest at ~982 MHz, recorded during observations toward Proxima Centauri with the Parkes Murriyang radio telescope. This signal, `BLC1', has characteristics broadly consistent with hypothesized technosignatures and is one of the most compelling candidates to date. Analysis of BLC1 -- which we ultimately attribute to being an unusual but locally-generated form of interference -- is provided in a companion paper (Sheikh et al., 2021). Nevertheless, our observations of Proxima Centauri are the most sensitive search for radio technosignatures ever undertaken on a star target.

Active galactic nuclei (AGN) are a promising source for high-energy astrophysical neutrinos (HEANs). By the end of 2022, the Vera C. Rubin Observatory (VRO) will begin to observe $\gtrsim10$ million AGN with a regular and high cadence. Here, we evaluate the capacity of VRO, in tandem with various current and upcoming neutrino telescopes, to establish AGN as HEAN emitters. To do so, we assume that the neutrino luminosity from any given AGN at any given time is proportional to the electromagnetic luminosity. We then estimate the error with which this fraction can be measured through spatial and temporal cross-correlation of VRO light curves with IceCube, KM3NeT, and Bakail-GVD. We find that it may be possible to detect AGN contributions at the $\sim3 \sigma$ level to the HEAN flux even if these AGN contribute only $\sim10\%$ of the HEAN flux. The bulk of this information comes from spatial correlations, although the temporal information improves the sensitivity a bit. The results also imply that if an angular correlation is detected with high signal-to-noise, there may be prospects to detect a correlation between AGN variability and neutrino arrival times. The small HEAN fraction estimated here to be accessible to the entirety of the VRO AGN sample suggests that valuable information on the character of the emitting AGN may be obtained through similar analyses on different sub-populations of AGN.

Understanding the preferences of transient types for host galaxies with certain characteristics is key to studies of transient physics and galaxy evolution, as well as to transient identification and classification in the LSST era. Here we describe a value-added database of extragalactic transients--supernovae, tidal disruption events, gamma-ray bursts, and other rare events--and their host galaxy properties. Based on reported coordinates, redshifts, and host galaxies (if known) of events, we cross-identify their host galaxies or most likely host candidates in various value-added or survey catalogs, and compile the existing photometric, spectroscopic, and derived physical properties of host galaxies in these catalogs. This new database covers photometric measurements from the far-ultraviolet to mid-infrared. Spectroscopic measurements and derived physical properties are also available for a smaller subset of hosts. For our 36333 unique events, we have cross-identified 13753 host galaxies using host names, plus 4480 using host coordinates. Besides those with known hosts, there are 18100 transients with newly identified host candidates. This large database will allow explorations of the connections of transients to their hosts, including a path toward transient alert filtering and probabilistic classification based on host properties.

Although the role of magnetic fields in launching molecular outflows in massive YSOs has been convincingly demonstrated by theoretical arguments, observationally, the alignment of the magnetic field lines with the molecular outflows is still under debate. We aim to complete the measurements of the direction of the magnetic fields at mas resolution around a sample of massive star-forming regions (MSFRs) to determine whether the magnetic field and outflows are aligned. In 2012, we started a large VLBI campaign with the EVN to measure the magnetic field orientation and strength toward a sample of 31 MSFRs (the flux-limited sample) by analyzing the polarized emission of 6.7GHz CH3OH masers. In the previous papers of the series, we have presented 80% of the sample. Here, we report the linearly and circularly polarized emission of 6.7GHz CH3OH masers toward the last five MSFRs of the flux-limited sample. The sources are G30.70-0.07, G30.76-0.05, G31.28+0.06, G32.03+0.06, and G69.52-0.97. We detected a total of 209 masers, 15% of which show linearly polarized emission (0.07%-16.7%), and 2% of which show circularly polarized emission (0.2%-4.2%). Zeeman splitting was measured toward G30.70-0.07, G32.03+0.06, and G69.52-0.97. The statistical analysis of the entire flux-limited sample shows that the observations are consistent with a bimodal distribution in the difference between the 3D magnetic field direction and the outflow axis, with half the magnetic field directions being perpendicular and the other half being parallel to the outflow. In addition, we determined that typical values of the linear and circular polarization fractions for 6.7 GHz CH3OH masers are Pl=1.0%-2.5% and Pv=0.5%-0.75%, respectively. We found that a typical Zeeman splitting is in the range between 0.5 m/s and 2.0 m/s. This would correspond to 9 mG<$|B_{||}|$<40 mG if F=3->4 is the most favored hyperfine transition.

Sampling-based inference techniques are central to modern cosmological data analysis; these methods, however, scale poorly with dimensionality and typically require approximate or intractable likelihoods. In this paper we describe how Truncated Marginal Neural Ratio Estimation (TMNRE) (a new approach in so-called simulation-based inference) naturally evades these issues, improving the $(i)$ efficiency, $(ii)$ scalability, and $(iii)$ trustworthiness of the inferred posteriors. Using measurements of the Cosmic Microwave Background (CMB), we show that TMNRE can achieve converged posteriors using orders of magnitude fewer simulator calls than conventional Markov Chain Monte Carlo (MCMC) methods. Remarkably, the required number of samples is effectively independent of the number of nuisance parameters. In addition, a property called \emph{local amortization} allows the performance of rigorous statistical consistency checks that are not accessible to sampling-based methods. TMNRE promises to become a powerful tool for cosmological data analysis, particularly in the context of extended cosmologies, where the timescale required for conventional sampling-based inference methods to converge can greatly exceed that of simple cosmological models such as $\Lambda$CDM. To perform these computations, we use an implementation of TMNRE via the open-source code \texttt{swyft}.

When a core-collapse supernova explodes in a binary star system, the ejecta might encounter an overdense shell, where the stellar winds of the two stars previously collided. In this work, we investigate effects of such interactions on supernova light curves on time-scales from the early flash ionization signatures to approximately one year after the explosion. We construct a model of the colliding-wind shell in an orbiting binary star system and we provide an analytical expression for the shell thickness and density, which we calibrate with three-dimensional adaptive mesh refinement hydrodynamical simulations probing different ratios of wind momenta and different regimes of radiative cooling efficiency. We model the angle-dependent interaction of supernova ejecta with the circumstellar medium and estimate the shock radiative efficiency with a realistic cooling function. We find that the radiated shock power exceeds typical Type IIP supernova luminosity only for double red supergiant binaries with mass ratios $q \gtrsim 0.9$, wind mass-loss rates $\dot{M} \gtrsim 10^{-4} M_\odot\,\text{yr}^{-1}$, and separations between about 50 and 1500 AU. The required $\dot{M}$ increases for binaries with smaller $q$ or primaries with faster wind. We estimate that $\ll 1\%$ of all collapsing massive stars satisfy the conditions on binary mass ratio and separation. Recombination luminosities due to colliding wind shells are at most a factor of 10 higher than for an otherwise unperturbed constant-velocity wind, but higher densities associated with wind acceleration close to the star provide much stronger signal.

We introduce a method to infer the vertical distribution of stars in the Milky Way using a Poisson likelihood function, with a view to applying our method to the Gaia catalogue. We show how to account for the sample selection function and for parallax measurement uncertainties. Our method is validated against a simulated sample drawn from a model with two exponential discs and a power-law halo profile. A mock Gaia sample is generated using the Gaia astrometry selection function, whilst realistic parallax uncertainties are drawn from the Gaia Astrometric Spread Function. The model is fit to the mock in order to rediscover the input parameters used to generate the sample. We recover posterior distributions which accurately fit the input parameters to within statistical uncertainties, demonstrating the efficacy of our method. Using the GUMS synthetic Milky Way catalogue we find that our halo parameter fits can be heavily biased by our overly simplistic model, however, the fits to the thin and thick discs are not significantly impacted. We apply this method to Gaia Early Data Release 3 in a companion paper where we also quantify the systematic uncertainties introduced by oversimplifications in our model.

We use Gaia photometry and astrometry to estimate the vertical spatial structure of the Milky Way at the Solar radius, formally accounting for sample incompleteness (the selection function) and parallax measurement uncertainty. Our results show impressive precision demonstrating the power of the Gaia data. However, systematic errors dominate the parameter value uncertainties. We thoroughly test and quantify the impacts of all systematic uncertainties. The vertical tracer density is modelled as a sum of two exponential profiles for the thin and thick discs, together with a spherically symmetric power-law for the stellar halo. We constrain the thin disc scale height as ${h_\mathrm{Tn}=260 \pm 3\, (\mathrm{stat}) \pm 26\,\mathrm{pc}\, (\mathrm{sys})}$ and thick disc ${h_\mathrm{Tk}=693 \pm 7 \,(\mathrm{stat}) \pm 121\,\mathrm{pc}\, (\mathrm{sys})}$. For the halo, we obtain a power law profile with $n_\mathrm{H}=3.543\pm0.023 \,(\mathrm{stat}) \pm0.259\, (\mathrm{sys})$. We infer a local stellar mass density for non-compact object stars of ${\rho_\mathrm{local}^* = 3.66\pm0.03\,(\mathrm{stat})\pm0.52 \times10^{-2}\,\mathrm{M}_\odot/\mathrm{pc}^3\,(\mathrm{sys})}$ and surface density of ${\Sigma_\mathrm{local}^* = 23.17\pm0.08\,(\mathrm{stat})\pm2.43\,\mathrm{M}_\odot/\mathrm{pc}^2\,(\mathrm{sys})}$. We find asymmetries above and below the disc with longer disc scale heights in the north but a flatter halo in the south at the $\lesssim 10$ per cent level.

Benzene ice contributes to an emission feature detected by the Cassini Composite InfraRed Spectrometer (CIRS) near 682 cm^{-1} in Titan's late southern fall polar stratosphere. It is as well one of the dominant components of the CIRS-observed High Altitude South Polar (HASP) ice cloud observed in Titan's mid stratosphere during late southern fall. Titan's stratosphere exhibits significant seasonal changes with temperatures that spatially vary with seasons. A quantitative analysis of the chemical composition of infrared emission spectra of Titan's stratospheric ice clouds relies on consistent and detailed laboratory transmittance spectra obtained at numerous temperatures. However, there is a substantial lack of experimental data on the spectroscopic and optical properties of benzene ice and its temperature dependence, especially at Titan-relevant stratospheric conditions. We have therefore analyzed in laboratory the spectral characteristics and evolution of benzene ice's vibrational modes at deposition temperatures ranging from 15 K to 130 K, from the far- to mid-IR spectral region (50 - 8000 cm^{-1}). We have determined the amorphous to crystalline phase transition of benzene ice and identified that a complete crystallization is achieved for deposition temperatures between 120 K and 130 K. We have also measured the real and imaginary parts of the ice complex refractive index of benzene ice from 15 K to 130 K. Our experimental results significantly extend the current state of knowledge on the deposition temperature dependence of benzene ice over a broad infrared spectral range, and provide useful new data for the analysis and interpretation of Titan-observed spectra.

The Gaia data give us an unprecedented view to the 3-dimensional (3D) structure of molecular clouds in the Solar neighbourhood. We study how the projected areas and masses of clouds, and consequently the Kennicutt-Schmidt relation (KS-relation), depend on the viewing angle. We derive the probability distributions of the projected areas and masses for nine clouds within 400 pc from the Sun using 3D dust distribution data from the literature. We find that the viewing angle can have a dramatic effect on the observed areas and masses of individual clouds. The joint probability distributions of the areas and masses are strongly correlated, relatively flat, and can show multiple peaks. The typical ranges and 50% quartiles of the distributions are roughly 100-200% and 20-80% of the median value, respectively, making viewing angle effects important for all individual clouds. The threshold value used to define the cloud areas is also important; our analysis suggests that the clouds become more anisotropic for smaller thresholds (larger scales). On average, the areas and masses of the plane-of-the-sky and face-on projections agree, albeit with a large scatter. This suggests that sample averages of areas and masses are relatively free of viewing angle effects, which is important to facilitate comparisons of extragalactic and galactic data. Ultimately, our results demonstrate that a cloud's location in the KS-relation is affected by viewing angle in a non-trivial manner. However, the KS-relation of our sample as a whole is not strongly affected by these effects, because the co-variance of the areas and masses causes the observed mean column density to remain relatively constant.

Continuum polarization over the UV-to-microwave range is due to dichroic extinction (or emission) by asymmetric, aligned dust grains. Because of both grain alignment and scattering physics, the wavelength dependence of the polarization, generally, traces the size of the aligned grains. Ultraviolet (UV) polarimetry therefore provides a unique probe of the smallest dust grains (diameter$<0.09\mu$m), their mineralogy and interaction with the environment. However, the current observational status of interstellar UV polarization is very poor with less than 30 lines of sight probed. With the modern, quantitative and well-tested, theory of interstellar grain alignment now available, we have the opportunity to advance the understanding of the interstellar medium by executing a systematic study of the UV polarization in the ISM of the Milky Way and near-by galaxies. The Polstar mission will provide the sensitivity and observing time needed to carry out such a program, addressing questions of dust composition as a function of size and location, radiation- and magnetic-field characteristics as well as unveiling the carrier of the 2175\AA\ extinction feature. In addition, using high-resolution UV line spectroscopy Polstar will search for and probe the alignment of, and polarization from, aligned atoms and ions - so called "Ground State Alignment", a potentially powerful new probe of magnetic fields in the diffuse ISM.

We present a comparative analysis of current observational constraints on three recently discussed alternative models for explaining the low-redshift acceleration of the universe: the so-called steady-state torsion model, the generalized coupling model, and the scale invariant model by Maeder (an example of a broader class which we also briefly study) These are compared to the traditional parameterization of Chevallier, Polarski and Linder. Each of the candidate models is studied under two different assumptions: as genuine alternatives to $\Lambda$CDM (where a new degree of freedom would be expected to explain the recent acceleration of the universe without any cosmological constant) and as parametric extensions of $\Lambda$CDM (where both a cosmological constant and the new mechanism can coexist, and the relative contributions of both are determined by the data). Our comparative analysis suggests that, from a phenomenological point of view, all such models neatly divide into two classes, with different observational consequences.

We previously reported a putative detection of a radio galaxy at z=10.15, selected from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey. The redshift of this source, GLEAM J0917-0012, was based upon three weakly detected molecular emission lines observed with the Atacama Large Millimetre Array (ALMA). In order to confirm this result, we conducted deep spectroscopic follow-up observations with ALMA and the Karl Jansky Very Large Array (VLA). The ALMA observations targeted the same CO lines previously reported in Band 3 (84-115GHz) and the VLA targeted the CO(4-3) and [CI(1-0)] lines for an independent confirmation in Q-band (41 and 44GHz). Neither observation detected any emission lines, removing support for our original interpretation. Adding publicly available optical data from the Hyper Suprime-Cam survey, WISE and Herschel Space Observatory in the infrared, as well as <10GHz polarisation and 162MHz inter-planetary scintillation observations, we model the physical and observational characteristics of GLEAM J0917-0012 as a function of redshift. Comparing these predictions and observational relations to the data, we are able to constrain its nature and distance. We argue that if GLEAM J0917-0012 is at z<3 then it has an extremely unusual nature, and that the more likely solution is that the source lies above z=7.

We present the results of a new selection technique to identify powerful ($L_{\rm 500\,MHz}>10^{27}\,$WHz$^{-1}$) radio galaxies towards the end of the Epoch of Reionisation. Our method is based on the selection of bright radio sources showing radio spectral curvature at the lowest frequency ($\sim 100\,$MHz) combined with the traditional faintness in $K-$band for high redshift galaxies. This technique is only possible thanks to the Galactic and Extra-galactic All-sky Murchison wide-field Array (GLEAM) survey which provides us with 20 flux measurements across the $70-230\,$MHz range. For this pilot project, we focus on the GAMA 09 field to demonstrate our technique. We present the results of our follow-up campaign with the Very Large Telescope, Australian Telescope Compact Array and the Atacama Large Millimetre Array (ALMA) to locate the host galaxy and to determine its redshift. Of our four candidate high redshift sources, we find two powerful radio galaxies in the $1<z<3$ range, confirm one at $z=5.55$ and present a very tentative $z=10.15$ candidate. Their near-infrared and radio properties show that we are preferentially selecting some of the most radio luminous objects, hosted by massive galaxies very similar to powerful radio galaxies at $1<z<5$. Our new selection and follow-up technique for finding powerful radio galaxies at $z>5.5$ has a high $25-50\%$ success rate.

Brightenings observed in the solar extreme-ultraviolet (EUV) images are generally interpreted as signatures of micro- or nanoflares occurring at the transition region or coronal temperatures. Recent observations with the Extreme Ultraviolet Imager (EUI) on board Solar Orbiter have revealed the smallest of such brightenings (termed campfires) in the quiet-Sun corona. Analyzing EUI 174 {\AA} data at a resolution of about 400 km on the Sun with a cadence of 5 s from 30-May-2020, we report here a number of cases where these campfires exhibit propagating signatures along their apparent small (3-5 Mm) loop-like structures. Measured propagation speeds are generally between 25 km s$^{-1}$ and 60 km s$^{-1}$. These apparent motions would be slower than the local sound speed if the loop plasma is assumed to be at a million Kelvin. Furthermore, these brightenings exhibit non-trivial propagation characteristics such as bifurcation, merging, reflection and repeated plasma ejections. We suggest that these features are manifestations of the internal dynamics of these small-scale magnetic structures and could provide important insights into the dynamic response ($\sim$40 s) of the loop plasma to the heating events as well as into the locations of the heating events themselves.

The detection rate of electromagnetic (EM) and gravitational wave (GW) transients is growing exponentially. As the accuracy of the transient rates will significantly improve over the coming decades, so will our understanding of their evolution through cosmic history. To this end, we present predicted rates for EM and GW transients over the age of the Universe using Binary Population and Spectral Synthesis (BPASS) results combined with four cosmic star formation histories (SFH). These include a widely used empirical SFH of Madau & Dickinson and those from three cosmological simulations: MilliMillennium, EAGLE and IllustrisTNG. We find that the choice of SFH significantly changes our predictions: transients with short delay times are most affected by the star formation rate, while long-delay time events tend to depend on the metallicity evolution of star formation. Importantly we find that the cosmological simulations have very different metallicity evolution that cannot be reproduced by the widely used metallicity model of Langer & Norman, which impacts the binary black hole merger and stripped-envelope supernovae rates in the local Universe most acutely. We recommend against using simple prescriptions for the metallicity evolution of the Universe when predicting the rates of events that can have long delay times and that are sensitive to metallicity evolution.

Context: Filamentary structures in nearby molecular clouds have been found to exhibit a characteristic width of 0.1 pc, as observed in dust emission. Understanding the origin of this universal width has become a topic of central importance in the study of molecular cloud structure and the early stages of star formation. Aims: We investigate how the recovered widths of filaments depend on distance from the observer, by using previously published results from the Herschel Gould Belt Survey. Methods: We obtain updated estimates on the distances to nearby molecular clouds observed with Herschel, by using recent results based on 3D dust extinction mapping and Gaia. We examine the widths of filaments from individual clouds separately, as opposed to treating them as a single population. We use these per-cloud filament widths to search for signs of variation amongst the clouds of the previously published study. Results: We find a significant dependence of the mean per-cloud filament width with distance. The distribution of mean filament widths for nearby clouds is incompatible with that of farther away clouds. The mean per-cloud widths scale with distance approximately as 4-5 times the beam size. We examine the effects of resolution by performing a convergence study of a filament profile in the Herschel image of the Taurus Molecular Cloud. We find that resolution can severely affect the shapes of radial profiles over the observed range of distances. Conclusions: We conclude that the data are inconsistent with 0.1 pc being the universal characteristic width of filaments.

Infrared emission features at 3.3, 6.2, 7.7, 8.6, and 11.2 $\mu$m, attributed to polycyclic aromatic hydrocarbons, show variations in relative intensity, shape, and peak position. These variations depend on the physical conditions of the photodissociation region (PDR) in which strong PAH emission arises, but their relationship has yet to be fully quantified. We aim to better calibrate the response of PAH species to their environment using observations with matching apertures and spatial resolution. We present observations from the Field-Imaging Far-Infrared Line Spectrometer (FIFI-LS) on board the Stratospheric Observatory for Infrared Astronomy (SOFIA) of the gas cooling lines [OI] 63, 146 $\mu$m and [CII] 158 $\mu$m in the reflection nebula NGC 1333 and use archival dust continuum observations from the Photodetector Array Camera and Spectrometer (PACS) on board Herschel. We employ PDR modelling to derive the physical conditions and compare these with the characteristics of the PAH emission as observed with the Infrared Spectrometer (IRS) on board Spitzer. We find distinct spatial characteristics for the various PAH spectral components. We conclude that the ionic bands (6.2, 7.7, 8.6, and 11.0) and the 7-9 $\mu$m emission are due to multiple PAH sub-populations and that the plateaus are distinct from the features perched on top. The 6-9 $\mu$m PAH emission exhibit a significant change in behaviour between the irradiated PDR and diffuse outskirts, confirming these bands arise from multiple PAH sub-populations with different underlying molecular properties. We find multiple promising relationships between PAH ratios and the FUV radiation field strength but no clear correlations with the PAH ionization parameter.

The 99942 Apophis close encounter with Earth in 2029 may provide information about asteroid's physical characteristics and measurements of Earth's effects on the asteroid surface. In this work, we analysed the surface and the nearby dynamics of Apophis. The possible effects of its 2029 encounter on the surface and environment vicinity are also analysed. We consider a 340 metres polyhedron with a uniform density (1.29 g$\cdot$cm$^{-3}$, 2.2 g$\cdot$cm$^{-3}$ and 3.5 g$\cdot$cm$^{-3}$). The slope angles are computed, as well their variation that arises during the close approach. Such variation reaches 4$^{\circ}$ when low densities are used in our simulations and reaches 2$^{\circ}$ when the density is high. The zero-velocity curves, the equilibrium points, and their topological classification are obtained. We found four external equilibrium points and two of them are linearly stable. We also perform numerical simulations of bodies orbiting the asteroid, taking into account the irregular gravitational field of Apophis and two extra scenarios of perturbations: the solar radiation pressure and the Earth's perturbation during the close approach. The radiation pressure plays an important role in the vicinity of the asteroid, only cm-sized particles survived for the time of integration. For densities of 2.2 g$\cdot$cm$^{-3}$ and 3.5 g$\cdot$cm$^{-3}$, a region of 5 cm radius particles survived for 30 years of the simulation, and for 1.29 g$\cdot$cm$^{-3}$, only particles with 15 cm of radius survived. The ejections and collisions are about 30-50 times larger when the close encounter effect is added, but around 56-59% of particles still survive the encounter.

Within the $\Lambda$CDM cosmological model, the absolute value of Einstein's cosmological constant $\Lambda$, sometimes expressed as the gravitating mass-energy density $\rho_\Lambda$ of the physical vacuum, is a fundamental constant of nature, whose accurate measurement plays a central role in testing some proposed theories of quantum gravity. Several combinations of currently public cosmological data and an assumed flat $\Lambda$CDM cosmological model are used here to make a joint Bayesian inference on the combination of conventional parameters $\Omega_\Lambda h^2$ that corresponds to the absolute physical density $\rho_\Lambda$. In physical units, we obtain $\rho_\Lambda = \left(60.3\pm{1.3}\right)\times 10^{-31}{\rm g/cm^3}$, the most accurate constraint to date, with an absolute calibration of cosmological measurements based on CMB temperature. Significantly different values are obtained with calibrations that use a local distance scale, mainly connected to systematic differences in the value of the Hubble constant. It is suggested that future comprehensive cosmological parameter studies include constraints on the vacuum density.

We study the gamma-ray spectra of 30 globular clusters (GCs) thus far detected with the Fermi Gamma-ray Space Telescope. Presuming that gamma-ray emission of a GC comes from millisecond pulsars (MSPs) contained in, a model that generates spectra for the GCs is built based on the gamma-ray properties of the detected MSP sample. We fit the GCs' spectra with the model, and for 27 of them, their emission can be explained with arising from MSPs. The spectra of the other three, NGC 7078, 2MS-GC01, and Terzan 1, can not be fit with our model, indicating that MSPs' emission should not be the dominant one in the first two and the third one has a unique hard spectrum. We also investigate six nearby GCs that have relatively high encounter rates as the comparison cases. The candidate spectrum of NGC 6656 can be fit with that of one MSP, supporting its possible association with the gamma-ray source at its position. The five others do not have detectable gamma-ray emission. Their spectral upper limits set limits of mostly $\leq 1$ MSPs in them, consistent with the numbers of radio MSPs found in them. The estimated numbers of MSPs in the gamma-ray GCs are generally larger than those reported for radio pulsars, suggesting more MSPs in them than those currently revealed. Our studies of the gamma-ray GCs and the comparison nearby GCs indicate that the encounter rate should not be the only factor determining the number of MSPs a GC contains.

We present the discovery of CWISE J052306.42$-$015355.4, which was found as a faint, significant proper motion object (0.52 $\pm$ 0.08 arcsec yr$^{-1}$) using machine learning tools on the unWISE re-processing on time series images from the Wide-field Infrared Survey Explorer. Using the CatWISE2020 W1 and W2 magnitudes along with a $J-$band detection from the VISTA Hemisphere Survey, the location of CWISE J052306.42$-$015355.4 on the W1$-$W2 vs. $J-$W2 diagram best matches that of other known, or suspected, extreme T subdwarfs. As there is currently very little knowledge concerning extreme T subdwarfs we estimate a rough distance of $\le$ 68 pc, which results in a tangential velocity of $\le$ 167 km s$^{-1}$, both of which are tentative. A measured parallax is greatly needed to test these values. We also estimate a metallicity of $-1.5 <$ [M/H] $< -0.5$ using theoretical predictions.

Two circumbinary planets have been recently discovered by TESS. The main aim of this work is to explore whether it is possible, besides the discovered circumbinary planet, to have an Earth-like planet within the habitable zone of the system. We carry out numerical simulations over the whole range of the two habitable zones in order to see whether an Earth mass planet can exist there. We find that both systems seem to be able to host an additional planet in their habitable zone. We construct dynamically informed habitable zones and we find that a large percentage of the habitable zone can be suitable for a planet to retain liquid water on its surface no matter what its orbital evolution will be. Moreover, we investigate the possibility to detect an Earth-like planet in the habitable zone of the two systems. We find that for both systems, if such a planet existed, the radial velocity and astrometry signals would be rather small to be detected by our current instruments. Some discussion is also made for the dynamical evolution of the existing planet.

Study of the polarization behaviour in blazars is a powerful tool to discern the role of magnetic field in the variable emission process in their relativistic jets. We present here results of our systematic investigation on the correlation between optical flux and polarization variations for eight flat-spectrum radio quasars on various timescales using data from the Steward Observatory that covers a period of $\sim$10 years. On long time scales ($\sim$several months), from a total of 79 observing cycles, in 34 observing cycles, we found a significant positive correlation between optical flux and optical polarization degree (PD), negative correlation in 3 cycles and no correlation in 42 cycles. On short time scales ($\sim$few days), in 47 out of a total of 55 epochs, we found a positive correlation between optical flux and PD, while, on the remaining 8 epochs, an anti-correlation was detected between the two quantities. Moreover, we noticed a significant positive correlation between optical and $\gamma-$ray fluxes on 14 epochs and a negative correlation between the two on one epoch. While the observed optical flux changes well fit in the shock-in-jet model, the observed changes in PD are not explainable by changes in the power-law spectral index of the relativistic electrons in the jet. Instead, the observed varied correlations between optical flux and PD could be due to multi-zone emission regions or the enhanced flux coinciding with the emergence of a new emission knot with its magnetic field either aligned or misaligned with the large scale magnetic field.

NGC1566 is a changing-look active galaxy that exhibited an outburst during 2017-2018 with a peak in June 2018. We triggered AstroSat observations of NGC 1566 twice in August and October 2018 during its declining phase. Using the AstroSat observations along-with two XMM-Newton observations in 2015 (pre-outburst) and June 2018 (peak-outburst), we found that the X-ray power-law, the soft X-ray excess, and the disk components showed extreme variability during the outburst. Especially, the soft excess was negligible in 2015 before the outburst, it increased to a maximum level by a factor of $>200$ in June 2018, and reduced dramatically by a factor of $\sim7.4$ in August 2018 and become undetectable in October 2018. The Eddington fraction ($L/L_{Edd})$ increased from $\sim0.1\%$ (2015) to $\sim 5\%$ (June 2018), then decreased to $\sim 1.5\%$ (August 2018) and $0.3\%$ (October 2018). Thus, NGC 1566 made a spectral transition from a high soft-excess state to a negligible soft-excess state at a few $\%$ of the Eddington rate. The soft-excess is consistent with warm Comptonization in the inner disk that appears to have developed during the outburst and disappeared towards the end of the outburst over a timescale comparable to the sound crossing time. The multi-wavelength spectral evolution of NGC 1566 during the outburst is most likely caused by the radiation pressure instability in the inner regions of the accretion disk in NGC 1566.

WASP-12b stands out among the planets of its class of hot Jupiters because of the observed fast orbital decay attributed to tidal dissipation. The measured rate of the orbital period is $\stackrel{\bf\centerdot}{\textstyle{P}}_{\rm orb}\,=\,-\,29\pm3\;\mbox{ms/yr}\;$=$\;(9.2\pm1.0)\times10^{-10}\;\mbox{s/s}$. In the literature heretofore, all attempts to explain this high rate were based on the assumption that the orbital evolution is dominated by the tides in the star. Since the modified tidal quality factor in yellow dwarfs is insufficient to warrant such a decay rate, a hypothesis was put forward that the star may actually be a subgiant. Using the latest data from the Gaia mission, we estimate the mass of WASP-12 at $1.28\,{M_{Sun}}$ and point out that it takes at least $600~\mbox{Myr}$ to evolve off the main sequence to its present state, which is roughly 20 times the inferred dynamical lifetime of the planet. The previous research neglected the tidal dissipation in the planet assuming it to be negligible due to the likely synchronisation of its rotation and a presumed high quality factor. We critically reassess this assumption in the light of recent astrometric results for Jupiter and Saturn, also employing more advanced theories of frequency-dependent tidal dissipation. Assuming that WASP-12b, like our Jupiter and Saturn, has a solid core, we find that the observed orbital decay is well explained by the tides in the planet. We calculate the exact value of the modified quality factor from the observed orbital decay and the upper bound eccentricity, which happens to coincide almost precisely with that of our Jupiter.

We openly study dark energy through the viewpoints of parametric and nonparametric analyses of late-time cosmological data. We consider three Hubble parameter priors reflecting the Hubble tension and make use of two phenomenological functions, namely, a normalized dark energy density and a compactified dark energy equation of state. We predict the shape of both functions and present new constraints on the dark energy equation of state. The results hint at dark energy evolution regardless of the choice of the method and of the priors. Given that dark energy evolution is arrived at by drastically different approaches, it emphasizes the result that the cosmological data prefers a nontrivial evolution.

Photons propagating in an external magnetic field may oscillate into axions or axion-like particles (ALPs). Such oscillations will lead to characteristic features in the energy spectrum of high-energy photons from astrophysical sources that can be used to probe the existence of ALPs. In this work, we revisit the signatures of these oscillations and stress the importance of a proper treatment of turbulent magnetic fields. We implement axions into ELMAG, complementing thereby the usual description of photon-axion oscillations with a Monte Carlo treatment of high-energy photon propagation and interactions. We also propose an alternative method of detecting axions through the discrete power spectrum using as observable the energy dependence of wiggles in the photon spectra.

We have investigated the feasibilities and accuracies of the identifications of RR Lyrae stars and quasars from the simulated data of the Multi-channel Photometric Survey Telescope (Mephisto) W Survey. Based on the variable sources light curve libraries from the Sloan Digital Sky Survey (SDSS) Stripe 82 data and the observation history simulation from the Mephisto-W Survey Scheduler, we have simulated the $uvgriz$ multi-band light curves of RR Lyrae stars, quasars and other variable sources for the first year observation of Mephisto-W Survey. We have applied the ensemble machine learning algorithm Random Forest Classifier (RFC) to identify RR Lyrae stars and quasars, respectively. We build training and test samples and extract ~ 150 features from the simulated light curves and train two RFCs respectively for the RR Lyrae star and quasar classification. We find that, our RFCs are able to select the RR Lyrae stars and quasars with remarkably high precision and completeness, with $purity$ = 95.4 per cent and $completeness$ = 96.9 per cent for the RR Lyrae RFC and $purity$ = 91.4 per cent and $completeness$ = 90.2 per cent for the quasar RFC. We have also derived relative importances of the extracted features utilized to classify RR Lyrae stars and quasars.

The census of the globular clusters (GCs) in the Milky Way (MW) is still a work in progress. We explore the nature of 19 new GC candidates in the Galactic bulge, based on the analysis of their colour-magnitude diagrams (CMDs) in the near-IR, using the VISTA Variables in the Via L\'actea Survey (VVV) database. We estimate their main astrophysical parameters: reddening and extinction, distance, total luminosity, mean cluster proper motions (PMs), metallicity and age. We obtain the cluster catalogues including the likely cluster members by applying a decontamination procedure on the observed CMDs, based upon the vector PM diagrams from VIRAC2. We estimate a wide reddening range of the $0.25 \leqslant E(J-K_s) \leqslant 2.0$ mag and extinction $0.11 \leqslant A_{Ks} \leqslant 0.86$ mag for the sample clusters as expected in the bulge regions. The range of heliocentric distances is $6.8\leqslant D\leqslant 11.4$ kpc. This allows us to place these clusters between 0.56 and 3.25 kpc from the Galactic centre, assuming $R_{\odot}=8.2$ kpc. Also, their PMs are kinematically similar to the typical motion of the Galactic bulge, apart from VVV-CL160, which shows different PMs. We also derive their metallicities and ages, finding $-1.40 \leqslant$ [Fe/H] $\leqslant 0.0$ dex and $t\approx 8-13$ Gyr respectively. The luminosities are calculated both in $K_{s}-$ and V-bands, recovering $-3.4 \leqslant M_V \leqslant -7.5$. We also examine the possible RR Lyrae members found in the cluster fields. Based on their positions, kinematics, metallicities and ages and comparing our results with the literature, we conclude that 9 candidates are real GCs, 7 need more observations to be fully confirmed as GCs, whereas 3 candidates are discarded for being younger open clusters.

The radio emission from faint extra-galactic sources hugely improves the study of cosmic evolution of star-forming galaxies (SFGs) and active galactic nuclei (AGN). Here, we study the faint sources in the ELAIS-N1 field using deep uGMRT observations in the 300--500 MHz frequency range, covering an area of 1.8 deg$^2$ with a sensitivity of $15 \mu$Jy beam$^{-1}$. Using a host of multi-waveband data in the infrared and spectroscopy in the optical, we broadly classify the sources as SFGs and AGN, and study the statistical properties of the radio--infrared relations up to redshift $z =$ 2 by $k$-correcting the observed data to rest-frame. We study the redshift variation of the monochromatic $q$ parameters at 24 and $70\mu$m, $q_{\rm 24\mu m}$ and $q_{\rm 70\mu m}$, respectively, and of bolometric $q_{\rm TIR}$ after integrating the infrared spectrum between 8 and $1000\mu$m. In our study $q_{24\mu m}$ is found to increase with $z$ caused by an increase in dust temperature ($T_{\rm dust}$) of the flux-limited sample at mid-infrared wavelengths. The $q_{\rm 70\mu m}$ and $q_{\rm TIR}$ are largely unaffected by $T_{\rm dust}$ variation in the sample and show a mild decrease with $z$ given as $q_{\rm 70\mu m} = (2.34 \pm 0.03)(1+z)^{-0.13 \pm 0.03}$ and $q_{\rm TIR} = (2.60 \pm 0.03)(1+z)^{-0.11 \pm 0.02}$. We observe tight correlations between the radio luminosity at 1.4GHz ($L_{\rm 1.4GHz}$) with monochromatic infrared luminosities at $24\mu$m ($L_{\rm 24\mu m}$) and at $70\mu$m ($L_{\rm 70\mu m}$), and with bolometric infrared luminosity ($L_{\rm TIR}$) having scatter less than a factor of 2 for SFGs up to $z=2$. All the radio--infrared relations have significant non-linear slopes. Such non-linearity could result in the $q$ parameters varying with redshift making it a complication for using them to study the evolution of the radio--infrared relations.

Context: The size of the Einstein Radius in a microlensing event scales as a square root of the mass of the lens. Therefore, long-lasting microlensing events are the best candidates for massive lenses, including black holes. Aims: Here we present the analysis of the Gaia18cbf microlensing event reported by the Gaia Science Alerts system. It has exhibited a long timescale and features characteristic to the annual microlensing parallax effect. We deduce the parameters of the lens based on the derived best fitting model. Methods: We used photometric data collected by the Gaia satellite as well as the follow-up data gathered by the ground-based observatories. We investigate the range of microlensing models and use them to derive the most probable mass and distance to the lens using a Galactic model as a prior. Using known mass-brightness relation we determined how likely it is that the lens is a main sequence star. Results: This event is one of the longest ever detected, with the Einstein timescale of $t_\mathrm{E}=491.41^{+128.31}_{-84.94}$~days for the best solution and $t_\mathrm{E}=453.74^{+178.69}_{-105.74}$~days for the second-best. This translates to a lens mass of $M_\mathrm{L} = 2.91^{+6.02}_{-1.70} M_\odot$ and $M_\mathrm{L} = 1.88^{+4.40}_{-1.19} M_\odot$ respectively. The limits on the blended light suggest that this event was most likely not caused by a main sequence star, but rather by a dark remnant of stellar evolution.

We present a new analytic model describing gravitational wave emission in the post-merger phase of binary neutron star mergers. The model is described by a number of physical parameters that are related to various oscillation modes, quasi-linear combination tones or non-linear features that appear in the post-merger phase. The time evolution of the main post-merger frequency peak is taken into account and it is described by a two-segment linear expression. The effectiveness of the model, in terms of the fitting factor or, equivalently, the reduction in the detection rate, is evaluated along a sequence of equal-mass simulations of varying mass. We find that all parameters of the analytic model correlate with the total binary mass of the system. For high masses, we identify new spectral features originating from the non-linear coupling between the quasi-radial oscillation and the antipodal tidal deformation, the inclusion of which significantly improves the fitting factors achieved by the model. We can thus model the post-merger gravitational-wave emission with an analytic model that achieves high fitting factors for a wide range of total binary masses. Our model can be used for the detection and parameter estimation of the post-merger phase in upcoming searches with upgraded second-generation detectors, such as aLIGO+ and aVirgo+, with future, third-generation detectors (Einstein Telescope and Cosmic Explorer) or with dedicated, high-frequency detectors.

The rotation of the galactic halos is a fascinating topic which is still waiting to be addressed. Planck data has shown the existence of a temperature asymmetry towards the halo of several nearby galaxies, such as M31, NGC 5128, M33, M81, and M82. However, the cause of this asymmetry is an open problem. A possibility to explain the observed effect relies on the presence of "cold gas clouds" populating the galactic halos, which may be the answer to the so-called missing baryon problem. Here, we present a technique to estimate an upper limit to the rotational velocity of the halo of some nearby spiral galaxies by using both their dynamical masses and the Planck data.

We have developed two arrays of lumped element kinetic inductance detectors working in the D-band, and optimised for the low radiative background conditions of a satellite mission aiming at precision measurements of the Cosmic Microwave Background (CMB). The first detector array is sensitive to the total power of the incoming radiation to which is coupled via single-mode waveguides and corrugated feed-horns, while the second is sensitive to the polarisation of the radiation thanks to orthomode transducers. Here, we focus on the total power detector array, which is suitable, for instance, for precision measurements of unpolarised spectral distortions of the CMB, where detecting both polarisations provides a sensitivity advantage. We describe the optimisation of the array design, fabrication and packaging, the dark and optical characterisation, and the performance of the black-body calibrator used for the optical tests. We show that almost all the detectors of the array are photon-noise limited under the radiative background of a 3.6 K black-body. This result, combined with the weak sensitivity to cosmic rays hits demonstrated with the OLIMPO flight, validates the idea of using lumped elements kinetic inductance detectors for precision, space-based CMB missions.

We present the first results from the SuperWASP Variable Stars (SVS) citizen science project. The photometry archive of the Wide Angle Search for Planets has previously been searched for periodic variations and the results of this search formed the basis of the SVS project on the Zooniverse. The SVS project asks volunteers to visually inspect light curve plots and categorize each one according to a broad classification scheme. Results from the first two years of SVS have now been published online as the SuperWASP Variable Star Photometry Archive (VeSPA). The archive can be browsed online, downloaded in full, or queried, filtered, and sorted to export a refined set of results. An interactive light curve viewer also allows any light curve to be folded at a user-defined period. Analysis of citizen science results and development of VeSPA features are both ongoing. Updated results will be published every six months.

21cm intensity mapping experiments are bringing an influx of high spectral resolution observational data in the $\sim100$ MHz $- 1$ GHz regime. We use pilot $971-1075$ MHz data from MeerKAT in single-dish mode, recently used to test the calibration and data reduction scheme of the upcoming MeerKLASS survey, to probe the spectral index of diffuse synchrotron emission below 1 GHz within $145^{\circ} < \alpha < 180^{\circ}$, $-1^{\circ} < \delta < 8^{\circ}$. Through comparisons with data from the OVRO Long Wavelength Array and the Maipu and MU surveys, we find an average spectral index of $-2.75 < \beta < -2.71$ between 45 and 1055 MHz. By fitting for spectral curvature with a spectral index of the form $\beta + c \, {\rm{ln}}(\nu / 73~{\rm MHz})$, we measure $\beta = -2.55 \pm 0.13$ and $c = -0.12 \pm 0.05$ within our target field. Our results are in good agreement (within $1\sigma$) with existing measurements from experiments such as ARCADE2 and EDGES. These results show the calibration accuracy of current data and demonstrate that MeerKLASS will also be capable of achieving a secondary science goal of probing the interstellar medium.

Having accurate completeness functions is crucial to the determination of the rest-frame ultraviolet luminosity functions (UVLFs) all the way back to the epoch of reionization. Most studies use injection-recovery simulations to determine completeness functions. Although conceptually similar, published approaches have subtle but important differences in their definition of the completeness function. As a result, they implement different methods to determine the UVLFs. We discuss the advantages and limitations of existing methods using a set of mock observations, and then compare the methods when applied to the same set of Hubble Legacy Field (HLF) images. We find that the most robust method under all our mock observations is the one that defines completeness as a function of both input and output magnitude. Other methods considering completeness only as a function of either input or output magnitude may suffer limitations in a presence of photometric scatter and/or steep luminosity functions. In particular, when the flux scatter is >0.2 mag, the bias in the bright end of the UVLFs is on par with other systematic effects such as the lensing magnification bias. When tested on HLF images, all methods yield UVLFs that are consistent within 2 sigma confidence, suggesting that UVLF uncertainties in the literature are still dominated by small number statistics and cosmic variance. The completeness simulation code used in this study (GLACiaR2) is publicly released with this paper as a tool to analyze future higher precision datasets such as those expected from the James Webb Space Telescope.

We propose a novel approach to obtain the growth rate of cosmic structures, $f(z)$, from the evolution of the cosmic homogeneity scale, $R_{\text{H}}(z)$. Our methodology needs two ingredients in a specific functional form: $R_{\text{H}}(z)$ data and the matter two-point correlation function today, i.e., $\xi(r, z=0)$. We use a Gaussian Process approach to reconstruct the function $R_{\text{H}}$. In the absence of suitable observational information of the matter correlation function in the local Universe, $z \simeq 0$, we assume a fiducial cosmology to obtain $\xi(r, z=0)$. For this reason, our final result turns out to be a consistency test of the cosmological model assumed. Our results show a good agreement between: (i) the growth rate $f^{R_{\text{H}}}(z)$ obtained through our approach, (ii) the $f^{\Lambda\text{CDM}}(z)$ expected in the fiducial model, and (iii) the best-fit $f(z)$ from data compiled in the literature. Moreover, using this data compilation, we perform a Gaussian Process to reconstruct the growth rate function $f^{\text{data}}(z)$ and compare it with the function $f^{R_{\text{H}}}(z)$ finding a concordance of $< \!2 \,\sigma$, a good result considering the few data available for both reconstruction processes. With more accurate $R_{\text{H}}(z)$ data, from forthcoming surveys, the homogeneity scale function might be better determined and would have the potential to discriminate between $\Lambda$CDM and alternative scenarios as a new cosmological observable.

Simple and complex organic molecules (COMs) are observed along different phases of star and planet formation and have been successfully identified in prestellar environments such as dark and translucent clouds. Yet the picture of organic molecule formation at those earliest stages of star formation is not complete and an important reason is the lack of specific laboratory experiments that simulate carbon atom addition reactions on icy surfaces of interstellar grains. Here we present experiments in which CO molecules as well as C- and H-atoms are co-deposited with H$_2$O molecules on a 10 K surface mimicking the ongoing formation of an "H$_2$O-rich" ice mantle. To simulate the effect of impacting C-atoms and resulting surface reactions with ice components, a specialized C-atom beam source is used, implemented on SURFRESIDE$^3$, an UHV cryogenic setup. Formation of ketene (CH$_2$CO) in the solid state is observed "in situ" by means of reflection absorption IR spectroscopy. C$^1$$^8$O and D isotope labelled experiments are performed to further validate the formation of ketene. Data analysis supports that CH$_2$CO is formed through C-atom addition to a CO-molecule, followed by successive hydrogenation transferring the formed :CCO into ketene. Efficient formation of ketene is in line with the absence of an activation barrier in C+CO reaction reported in the literature. We also discuss and provide experimental evidence for the formation of acetaldehyde (CH$_3$CHO) and possible formation of ethanol (CH$_3$CH$_2$OH), two COM derivatives of CH$_2$CO hydrogenation. The underlying reaction network is presented and the astrochemical implications of the derived pathways are discussed.

Spinning neutron stars can emit long-lived gravitational waves. There are several mechanisms that can produce such continuous wave emission. These mechanisms relate to the strains in the elastic crust, the star's magnetic field, superfluidity of the neutron fluid, and bulk oscillations of the entire star. In this chapter we describe how the frequency content of the gravitational wave signal, and its relation to any electromagnetically observed spin frequency, can be used to constrain the mechanism producing the gravitational waves. These ideas will be of use in the event of the first detections of such signals, and help convert a detection into useful physical insight.

In recent years Microwave Kinetic Inductance Detectors (MKIDs) have emerged as one of the most promising novel low temperature detector technologies. Their unrivaled scalability makes them very attractive for many modern applications and scientific instruments. In this paper we intend to give an overview of how and where MKIDs are currently being used or are suggested to be used in the future. MKID based projects are ongoing or proposed for observational astronomy, particle physics, material science and THz imaging, and the goal of this review is to provide an easily usable and thorough list of possible starting points for more in-depth literature research on the many areas profiting from kinetic inductance detectors.

Phase-resolved spectral and spectropolarimetric X-ray observations of magnetars present us with the opportunity to test models of the origin of the X-ray emission from these objects, and to constrain the properties of the neutron star surface and atmosphere. We present a new X-ray fitting model for magnetars that accounts for four different emission models including a blackbody emission model, a magnetized atmosphere model, and fixed-ions and free-ions surface emission models. We use the new model for a phase resolved fit of archival XMM-Newton observations of the magnetar 1RXS J170849.0-400910. We find that the fixed-ions condensed surface model gives the best description of the phase-resolved XMM-Newton spectra, followed by the blackbody and free-ions condensed surface models. The magnetized atmosphere model gives a poor description of the data and seems to be largely excluded. We use the new fitting model to evaluate the scientific potential of future spectropolarimetric observations of 1RXS J170849.0-400910 with the Imaging X-ray Polarimetry Explorer (IXPE) scheduled for launch in December 2021. Our simulations show that the IXPE observations of sources such as 1RXS J170849.0-400910 will allow us to cleanly distinguish between high-polarization (blackbody, magnetized atmosphere) and low-polarization (condensed surface) models. If the higher-polarization blackbody or magnetized atmosphere models apply, IXPE can easily prove QED effects based on a 200 ksec observation as studied here. Longer IXPE observation times will be needed for a clear detection in the case of the lower-polarization condensed surface models.

We report on the direct observation of an extended X-ray jet in the $z$=6.1 radio-loud Active Galactic Nucleus PSO J030947.49+271757.31 from a deep Chandra X-ray observation (128 ksec). This detection represents the most distant kpc off-nuclear emission resolved in the X-rays to date. The angular distance of the emission is $\sim$4" (corresponding to $\sim$20 kpc at $z$=6.1), along the same direction of the jet observed at parsec scales in previous VLBA high-resolution radio observations. Moreover, the 0.5-7.0 keV isophotes coincide with the extended radio emission as imaged by the VLA Sky Survey at 3 GHz. The rest-frame 2-10 keV luminosity of the extended component is L$_{2-10keV}$=5.9$\times$10$^{44}$ erg s$^{-1}$, about 8% of the core: this makes it one of the most luminous jets resolved in the X-rays so far. Through Spectral Energy Distribution modelling we find that this emission can be explained by the Inverse Compton interaction with the photons of the Cosmic Microwave Background assuming that the jet's physical parameters are similar to those in the local Universe. At the same time, we find that the radiation produced by a putative population of high-energetic electrons through the synchrotron process observed at low redshift is quenched at high redshift, hence becoming negligible.

Type I Be/X-ray binary outbursts are driven by mass transfer from a Be star decretion disc to a neutron star companion during each orbital period. Treiber et al. (2021) recently observed non-periodic type I outbursts in RX J0529.8-6556 that has unknown binary orbital properties. We show that non-periodic type I outbursts may be temporarily driven in a low eccentricity binary with a disc that is inclined sufficiently to be mildly unstable to Kozai-Lidov oscillations. The inclined disc becomes eccentric and material is transferred to the neutron star at up to three locations in each orbit: when the neutron star passes the disc apastron or one of the two nodes of the disc. The timing and magnitude of each vary with the disc argument of periapsis and longitude of the ascending node that precess in opposite directions. Calculating the orbital period of the RX J0529.8-6556 system is non-trivial but we suggest it maybe >300 day, longer than previous estimates.

Direct observations of young stellar objects are important to test established theories of planet formation. PDS 70 is one of the few cases where robust evidence favours the presence of two planetary mass companions inside the gap of the transition disk. Those planets are believed to be going through the last stages of accretion from the protoplanetary disk, a process likely mediated by a circumplanetary disk (CPD). We aim to develop a three dimensional radiative transfer model for the dust component of the PDS 70 system which reproduces the system's global features observed at two different wavelengths: 855 $\mu\, \mathrm{m}$ with ALMA and 1.25 $\mu\, \mathrm{m}$ with VLT/SPHERE. We use this model to investigate the physical properties of the planetary companion PDS 70 c and its potential circumplanetary disk. We select initial values for the physical properties of the planet and CPD through appropriate assumptions about the nature and evolutionary stage of the object. We modify iteratively the properties of the protoplanetary disk until the predictions retrieved from the model are consistent with both data sets. We provide a model that jointly explains the global features of the PDS 70 system seen in submillimeter and polarised-scattered light. Our model suggests that spatial segregation of dust grains is present in the protoplanetary disk. The submillimeter modelling of the PDS 70 c source favours the presence of an optically thick CPD and places an upper limit to its dust mass of 0.7 $M_\oplus$. Furthermore, analysis of the thermal structure of the CPD demonstrates that the planet luminosity is the dominant heating mechanism of dust grains inside 0.6 au from the planet while heating by stellar photons dominates at larger planetocentric distances.

V1298 Tau is a young (20-30 Myr) solar analogue hosting four transiting exoplanets with sizes between 0.5-0.9R$_J$. Given the system's youth, it provides a unique opportunity to understand the evolution of planetary radii at different separations in the same stellar environment. V1298 Tau was originally observed 6 years ago during K2 Campaign 4. Now, V1298 Tau has been re-observed during the extended mission of NASA's Transiting Exoplanet Survey Satellite (TESS). Here, we present new photometric observations of V1298 Tau from the 10-minute TESS Full-Frame Images. We use the TESS data to update the ephemerides for V1298 Tau bcde as well as compare newly observed radii to those derived from the K2 light curve, finding shallower transits for V1298 Tau bcd in the redder TESS bandpass at the 1-2 $\sigma$ level. We suspect the difference in radii is due to starspot-crossing events or contamination from nearby faint stars on the same pixels as V1298 Tau. We additionally catch a second transit of V1298 Tau e and present a new method for deriving the marginalized posterior probability of a planet's period from two transits observed years apart. We find the highest probability period for V1298 Tau e to be in a near 2:1 mean motion resonance with V1298 Tau b which, if confirmed, could make V1298 Tau bcde a 4 planet resonant chain. V1298 Tau is the target of several ongoing and future observations. These updated ephemerides will be crucial for scheduling future transit observations and interpreting future Doppler tomographic or transmission spectroscopy signals.

Primordial black holes (PBHs) formed in the early Universe constitute an attractive candidate for dark matter. Within the gaseous environment of the interstellar medium, PBHs with accretion disks naturally launch outflows such as winds and jets. PBHs with significant spin can sustain powerful relativistic jets and generate associated cocoons. Jets and winds can efficiently deposit their kinetic energies and heat the surrounding gas through shocks. Focusing on the Leo T dwarf galaxy, we demonstrate that these considerations can provide novel tests of PBHs over a significant $\sim 10^{-2} M_{\odot} - 10^6 M_{\odot}$ mass range, including the parameter space associated with gravitational wave observations by the LIGO and VIRGO Collaborations. Observing the morphology of emission could allow to distinguish between jet and wind contributions, and hence indirectly detect spinning PBHs.

Oscillons are spatially localized, time-periodic and long-lived configurations that were primarily proposed in scalar field theories with attractive self-interactions. In this letter, we demonstrate that oscillons also exist in the low-energy effective theory of an interacting massive (real) vector field. We provide two types of vector oscillons with vanishing orbital angular momentum, and approximately spherically symmetric energy density, but not field configurations. These are: (1) "directional" oscillons (linearly polarized), with vanishing total intrinsic spin, and (2) "spinning" oscillons (circularly polarized) with a macroscopic instrinsic spin equal to $\hbar\times$ number of particles in the oscillon. In contrast to the case with only gravitational interactions, the two oscillons have different energy at a fixed particle number even in the nonrelativistic limit. By carrying out relativistic $3+1$d simulations, we show that these oscillons can be long-lived (compared to the oscillation time for the fields), and can arise from a range of Gaussian initial spatial profiles. These considerations make vector oscillons potentially relevant during the early universe and in dark photon dark matter, with novel phenomenology related to their polarization.

Gas-rich dwarf galaxies located outside the virial radius of their host are relatively pristine systems and have ultra-low gas cooling rates. This makes them very sensitive to heat injection by annihilation or decay of dark matter (DM). Such dwarfs are particularly sensitive to DM producing e$^\pm$ with energies 1$-$100 MeV or photons with energies 13.6 eV$-1$ keV, because these products can be efficiently thermalized in the neutral hydrogen gas of the dwarfs. Following the methodology of Wadekar and Farrar (2021), we require the rate of heat injection by DM to not exceed the ultra-low radiative cooling rate of gas in the Leo T dwarf galaxy. This gives model-independent bounds on $(i)$ the decay lifetime of DM to $e^\pm$ (photons) which are stronger than all the previous literature for $m_\mathrm{DM}\sim$ 1$-$10 MeV ($m_\mathrm{DM}\sim0.02-1$ keV), $(ii)$ annihilation of DM to $e^{\pm}$ comparable to constraints from CMB and X/$\gamma$-ray surveys. We also translate our bounds for the case of the following DM models: axion-like particles (ALPs), sterile neutrinos, excited DM states, higgs portal scalars and dark baryons. Observations of gas-rich low-mass dwarfs from upcoming 21cm and optical surveys can therefore be powerful probes of a multitude of models of DM.

I present a numerical fit to the peak harmonic gravitational wave (GW) frequency emitted by an eccentric binary system in the post-Newtonian approximation. This fit significantly improves upon a previous commonly-used fit, in particular for eccentricities $\lesssim 0.8$, with potentially important implications for some previous predictions of eccentric GW sources in both the LIGO and LISA detector bands. The new fit should be useful for future studies of eccentric sources which are motivated by the anticipation of the detection of eccentric sources in future GW observations.

We study the possibility of cogenesis of baryon and dark matter (DM) from the out-of-equilibrium CP violating decay of right handed neutrino (RHN) that are dominantly of non-thermal origin. While the RHN and its heavier partners can take part in light neutrino mass generation via Type-I seesaw mechanism, the decay of RHN into dark and visible sectors can create respective asymmetries simultaneously. The non-thermal sources of RHN considered are {\bf (a)} on-shell decay of inflaton, and {\bf (b)} evaporation of ultralight primordial black holes (PBH). After setting up the complete set of Boltzmann equations in both these scenarios, we constrain the resulting parameter space of the particle physics setup, along with inflaton and PBH sectors from the requirement of generating correct (asymmetric) DM abundance and baryon asymmetry, while being in agreement with other relevant cosmological bounds. Scenario {\bf (a)} links the common origin of DM and baryon asymmetry to post-inflationary reheating via RHNs produced in inflaton decay, whereas in scenario {\bf (b)} we find enhancement of baryon and DM abundance, compared to the purely thermal scenarios, in presence of PBH with appropriate mass and initial fraction. Although the minimal setup itself is very predictive with observational consequences, details of the UV completion of the dark sector can offer several complementary probes.

The study of inhomogeneous neutron matter can provide insights into the structure of neutron stars as well as their dynamics in neutron-star mergers. In this work we tackle pure neutron matter in the presence of a periodic external field by considering a finite (but potentially large) number of particles placed in periodic boundary conditions. We start with the simpler setting of a noninteracting gas and then switch to a Skyrme-Hartree-Fock approach, showing static-response results for five distinct Skyrme parametrizations. We explain both the technical details of our computational approach, as well as the significance of these results as a general finite-size extrapolation scheme that may be used by ab initi} practitioners to approach the static-response problem of neutron matter in the thermodynamic limit.

We investigate a systematic formulation of vector-tensor theories based on the effective field theory (EFT) approach. The input of our EFT is that the spacetime symmetry is spontaneously broken by the existence of a preferred timelike direction in accordance with the cosmological principle. After clarifying the difference of the symmetry breaking pattern from the conventional EFT of inflation/dark energy, we find an EFT description of vector-tensor theories around the cosmological background. This approach not only serves as a unified description of vector-tensor theories but also highlights universal differences between the scalar-tensor theories and the vector-tensor theories. The theories having different symmetry breaking patterns are distinguished by a phenomenological function and consistency relations between the EFT coefficients. We study the linear cosmological perturbations within our EFT framework and discuss the characteristic properties of the vector-tensor theories in the context of dark energy. In particular, we compute the effective gravitational coupling and the slip parameter for the matter density contrast in terms of the EFT coefficients.

In dense environments, standard and non-standard neutrino interactions with the background particles trigger a variety of flavor mechanisms, which can impact r-process nucleosynthetic abundances. Future observations of a(n) (extra)galactic supernova will tell us about properties of neutrinos and of the astrophysical source that produce them. The upcoming measurement of the diffuse supernova neutrino background constitute a unique source of information. We highlight some recent developments.

In this work, we elaborate on the finite action for wormholes in higher derivative theories. Both non-traversable and traversable wormholes in theories with higher curvature invariants posses finite action.

We present gas-phase InfraRed Multiple Photon Dissociation (IRMPD) spectroscopy of cationic phenanthrene, pyrene, and perylene over the 100$-$1700 cm$^{-1}$ (6-95 $\mu$m) spectral range. This range covers both local vibrational modes involving C$-$C and C$-$H bonds in the mid-IR, and large-amplitude skeletal modes in the far-IR. The experiments were done using the 7T Fourier-Transform Ion Cyclotron Resonance (FTICR) mass spectrometer integrated in the Free-Electron Laser for Intra-Cavity Experiments (FELICE), and findings were complemented with Density Functional Theory (DFT) calculated harmonic and anharmonic spectra, matching the experimental spectra well. The experimental configuration that enables this sensitive spectroscopy of the strongly-bound, photo-resistant Polycyclic Aromatic Hydrocarbons (PAHs) over a wide range can provide such high photon densities that even combination modes with calculated intensities as low as 0.01 km$\cdot$mol$^{-1}$ near 400 cm$^{-1}$ (25 $\mu$m) can be detected. Experimental frequencies from this work and all currently available IRMPD spectra for PAH cations were compared to theoretical frequencies from the NASA Ames PAH IR Spectroscopic Database to verify predicted trends for far-IR vibrational modes depending on PAH shape and size, and only a relatively small redshift (6$-$11 cm$^{-1}$) was found between experiment and theory. The absence of spectral congestion and the drastic reduction in bandwidth with respect to the mid-IR make the far-IR fingerprints viable candidates for theoretical benchmarking, which can aid in the search for individual large PAHs in the interstellar medium.

Raw light curve data from exoplanet transits is too complex to naively apply traditional outlier detection methods. We propose an architecture which estimates a latent representation of both the main transit and residual deviations with a pair of variational autoencoders. We show, using two fabricated datasets, that our latent representations of anomalous transit residuals are significantly more amenable to outlier detection than raw data or the latent representation of a traditional variational autoencoder. We then apply our method to real exoplanet transit data. Our study is the first which automatically identifies anomalous exoplanet transit light curves. We additionally release three first-of-their-kind datasets to enable further research.

We envisage a black hole perturbed by a force-free magnetic field (FFMF) outside and attempt to determine its structure. We suppose the metric that describes this black hole is of the static spherical type, that is Schwarzschild, and the energy-momentum tensor emanating from an FFMF source perturbs this background metric, in this regard one can imagine a magnetic accretion disk around the black hole. By solving the equations for such a configuration, we will show that in addition to modifying the diagonal elements of the background metric, we will also see the non-zeroing of the off-diagonal elements of the general metric, one of the immediate consequences of which will be a static to stationary transition.