Papers for Friday, Jul 08 2022

Abell 1351 is a massive merging cluster that hosts a giant radio halo and a bright radio edge blended in the halo. In this paper, we present the first ever spectral analysis of this cluster using GMRT 610 MHz and VLA 1.4 GHz archival data and discuss the radio edge property. Using \textit{Chandra} data, we report the first tentative detection of shock front at the location of the edge in A1351 with discontinuities in both X-ray surface brightness and temperature. Our analysis strengthens the previous claim of the detected "edge" being a high luminosity radio relic. The radio relic has an integrated spectral index $\alpha = -1.63 \pm 0.33$ and radio power $P_{1.4 \mathrm{\ GHz}} = 4.46 \pm 0.61\times10^{24}$ W $Hz^{-1}$ with a largest Linear Size (LLS) of 570 kpc. The radio spectral index map shows steepening in the shock downstream region. Our analysis favours the scenario where the Diffusive Shock Acceleration (DSA) of particles is responsible for the origin of the radio relic in the presence of strong magnetic field. We have also estimated the magnetic field at the relic location assuming equipartition condition.

The Milky Way's stellar disk can tilt in response to torques that result from infalling satellite galaxies and their associated tidal debris. In this work, we explore the dynamics of disk tilting by running N-body simulations of mergers in an isolated, isotropic Milky Way-like host galaxy, varying over satellite virial mass, initial position, and orbit. We develop and validate a first-principles understanding of the dynamics that govern how the host galaxy's stellar disk responds to the satellite's dark matter debris. We find that the degree of disk tilting can be large for cosmologically-motivated merger histories. In particular, our results suggest that the Galactic disk may still be tilting in response to Gaia-Sausage-Enceladus, one of the most significant recent mergers in the Milky Way's history. These findings have implications for terrestrial direct detection experiments as disk tilting changes the relative location of the Sun with respect to dark matter substructure left behind by a merging galaxy.

The recent discovery of the extremely lensed Earendel object at $z=6.2$ is remarkable in that it is likely a single star or stellar multiple, observed within the first billion years of cosmic history. Depending on its mass, which is still uncertain but will soon be more tightly constrained with the James Webb Space Telescope, the Earendel star might even be a member of the first generation of stars, the so-called Population~III (Pop~III). By combining results from detailed cosmological simulations of the assembly of the first galaxies, including the enrichment of the pristine gas with heavy chemical elements, with assumptions on key stellar parameters, we quantify the probability that Earendel has indeed a Pop~III origin. We find that this probability is non-negligible throughout the mass range inferred for Earendel, specifically ranging from a few percent at the lower-mass end to near unity for some Pop~III initial mass function (IMF) models towards the high-mass end of the allowed range. For models that extend the metal-enriched IMF to $500$\,M$_\odot$, the likelihood of Earendel being a Pop~III star stays at the few to ten percent level. We discuss the implications of such a discovery for the overall endeavor to probe the hitherto so elusive first stars in the universe.

We present the third discovery from the COol Companions ON Ultrawide orbiTS (COCONUTS) program, the COCONUTS-3 system, composed of a young M5 primary star UCAC4 374-046899 and a very red L6 dwarf WISEA J081322.19$-$152203.2. These two objects have a projected separation of 61$''$ (1891 au) and are physically associated given their common proper motions and estimated distances. The primary star, COCONUTS-3A, has a mass of $0.123\pm0.006$ M$_{\odot}$ and we estimate its age as 100 Myr to 1 Gyr based on its kinematics and spectrophotometric properties. We derive its metallicity as $0.21 \pm 0.07$ dex using empirical calibrations established by older higher-gravity M dwarfs and find this [Fe/H] could be slightly underestimated according to PHOENIX models given COCONUTS-3A's younger age. The companion, COCONUTS-3B, has a near-infrared spectral type of L6$\pm$1 INT-G, and we infer physical properties of $T_{\rm eff} = 1362^{+48}_{-73}$ K, $\log{(g)}= 4.96^{+0.15}_{-0.34}$ dex, $R = 1.03^{+0.12}_{-0.06}$ R$_{\rm Jup}$, and $M = 39^{+11}_{-18}$ M$_{\rm Jup}$, using its bolometric luminosity, its host star's age, and hot-start evolution models. We construct cloudy atmospheric model spectra at the evolution-based physical parameters and compare them to COCONUTS-3B's spectrophotometry. We find this companion possesses ample condensate clouds in its photosphere with the data-model discrepancies likely due to the models using an older version of the opacity database. Compared to field-age L6 dwarfs, COCONUTS-3B has fainter absolute magnitudes and a 120 K cooler $T_{\rm eff}$. Also, the J-K color of this companion is among the reddest for ultracool benchmarks with ages older than a few 100 Myr. COCONUTS-3 likely formed in the same fashion as stellar binaries given the companion-to-host mass ratio of 0.3 and represents a valuable benchmark to quantify the systematics of substellar model atmospheres.

We calculate the observed luminosity and spectrum following the emergence of a relativistic shock wave from a stellar edges. Shock waves propagating at $0.6<\Gamma_\text{sh}\beta_\text{sh}$, where $\Gamma_\text{sh}$ is the shock Lorentz factor and $\beta_\text{sh}$ is its associated reduced velocity, heat the stellar envelope to temperatures exceeding $\sim 50$ keV, allowing for a vigorous production of electron and positron pairs. Pairs significantly increase the electron scattering optical depth and regulate the temperature through photon generation, producing distinct observational signatures in the escaping emission. Assuming Wien equilibrium, we find analytic expressions for the temperature and pair density profiles in the envelope immediately after shock passage, and compute the emission during the expansion phase. Our analysis shows that in pair loaded regions, photons are produced at a roughly uniform rest frame energy of $\sim 200$ keV, and reinforces previous estimates that the shock breakout signal will be detected as a short burst of energetic $\gamma$-ray photons, followed by a longer phase of X-ray emission. We test our model on a sample of low-luminosity gamma ray bursts using a closure relation between the $\gamma$-ray burst duration, the radiation temperature and the $\gamma$-ray isotropic equivalent energy, and find that some of the events are consistent with the relativistic shock breakout model. Finally, we apply our results to explosions in white dwarfs and neutron stars, and find that typical type Ia supernovae emit $\sim 10^{41}$ erg in the form of $\sim 1$ MeV photons.

We test the hypothesis that an embedded giant planet in the IM Lupi protostellar disc can produce velocity kinks seen in CO line observations as well as the spiral arms seen in scattered light and continuum emission. We inject planets into 3D hydrodynamics simulations of IM Lupi, generating synthetic observations using Monte Carlo radiative transfer. We find that an embedded planet of 2-3 times the mass of Jupiter can reproduce non-Keplerian velocity perturbations, or `kinks', in the 12CO J=2-1 channel maps. Such a planet can also explain the spiral arms seen in 1.25mm dust continuum emission and 1.6 micron scattered light images. We show that the wake of the planet can be traced in the observed peak velocity map, which appears to closely follow the morphology expected from our simulations and from analytic models of planet-disc interaction.

We present measurements of the dependence of the clustering amplitude of galaxies on their star formation rate (SFR) and stellar mass ($M_*$) at $0.7 < z < 1.5$ to assess the extent to which environment affects these properties. While these relations are well determined in the local universe, they are much more poorly known at earlier times. For this analysis we make use of the near-IR HST WFC3 grism spectroscopic data in the five CANDELS fields obtained as part of the 3D-HST survey. We make projected 2-point correlation function measurements using $\sim$6,000 galaxies with accurate redshifts, $M_*$ and H$\alpha$ luminosities. We find a strong dependence of clustering amplitude on H$\alpha$ luminosity and thus SFR. However, at fixed $M_*$, the clustering dependence on H$\alpha$ luminosity is largely eliminated. We model the clustering of these galaxies within the Halo Occupation Distribution framework using the conditional luminosity function model and the newly developed conditional stellar mass and H$\alpha$ luminosity distribution model. These show that galaxies with higher SFRs tend to live in higher mass haloes, but this is largely driven by the relationship between SFR and $M_*$. Finally, we show that the small residual correlation between clustering amplitude and H$\alpha$ luminosity at fixed $M_*$ is likely being driven by a broadening of the SFR-$M_*$ relationship for satellite galaxies.

We present observations of an extreme radio flare, VT J024345.70-284040.08, hereafter VT J0243, from the nucleus of a galaxy with evidence for historic Seyfert activity at redshift $z=0.074$. Between NRAO VLA Sky Survey observations in 1993 to VLA Sky Survey observations in 2018, VT J0243 rose from a ${\sim}$GHz radio luminosity of $\nu L_\nu \lesssim 10^{38}$ erg s$^{-1}$ to $\nu L_\nu{\sim}10^{40}$ erg s$^{-1}$, and still continues to brighten. The radio spectral energy distribution (SED) evolution is consistent with a nascent jet that has slowed over ${\sim}3000$ days with an average $0.1 < \langle \beta \rangle < 0.6$. The jet is energetic (${\sim}10^{51-52}$ erg), and had a radius ${\sim}0.7$ pc in Dec. 2021. X-ray observations suggest a persistent or evolving corona, possibly associated with an accretion disk, and IR and optical observations constrain any high-energy counterpart to be sub-Eddington. VT J0243 may be an example of a young, off-axis radio jet from a slowly evolving tidal disruption event. Other more mysterious triggers for the accretion enhancement and jet launching are possible. In either case, VT J0243 is a unique example of a nascent jet, highlighting the unknown connection between supermassive black holes, the properties of their accretion flows, and jet launching.

Recently, the mean free path of ionizing photons in the $z = 6$ intergalactic medium (IGM) was measured to be very short, presenting a challenge to existing reionization models. At face value, the measurement can be interpreted as evidence that the IGM clumps on scales $M\lesssim 10^8$ M$_\odot$, a key but largely untested prediction of the cold dark matter (CDM) paradigm. Motivated by this possibility, we study the role that the underlying dark matter cosmology plays in setting the $z > 5$ mean free path. We use two classes of models to contrast against the standard CDM prediction: (1) thermal relic warm dark matter (WDM), representing models with suppressed small-scale power; (2) an ultralight axion exhibiting a white noise-like power enhancement. Differences in the mean free path between the WDM and CDM models are subdued by pressure smoothing and the possible contribution of neutral islands to the IGM opacity. For example, comparing late reionization scenarios with a fixed volume-weighted mean neutral fraction of $20\%$ at $z=6$, the mean free path is $19~(45)~\%$ longer in a WDM model with $m_x = 3~(1)$ keV. The enhanced power in the axion-like model produces better agreement with the short mean free path measured at $z = 6$. However, drawing robust conclusions about cosmology is hampered by large uncertainties in the reionization process, extragalactic ionizing background, and thermal history of the Universe. This work highlights some key open questions about the IGM opacity during reionization.

Current models of the solar wind must approximate (or ignore) the small-scale dynamics within the solar atmosphere, however these are likely important in shaping the emerging wave-turbulence spectrum and ultimately heating/accelerating the coronal plasma. The Bifrost code produces realistic simulations of the solar atmosphere that facilitate the analysis of spatial and temporal scales which are currently at, or beyond, the limit of modern solar telescopes. For this study, the Bifrost simulation is configured to represent the solar atmosphere in a coronal hole region, from which the fast solar wind emerges. The simulation extends from the upper-convection zone (2.5 Mm below the photosphere) to the low-corona (14.5 Mm above the photosphere), with a horizontal extent of 24 Mm x 24 Mm. The twisting of the coronal magnetic field by photospheric flows, efficiently injects energy into the low-corona. Poynting fluxes of up to $2-4$ kWm$^{-2}$ are commonly observed inside twisted magnetic structures with diameters in the low-corona of 1 - 5 Mm. Torsional Alfv\'en waves are favourably transmitted along these structures, and will subsequently escape into the solar wind. However, reflections of these waves from the upper boundary condition make it difficult to unambiguously quantify the emerging Alfv\'en wave-energy flux. This study represents a first step in quantifying the conditions at the base of the solar wind using Bifrost simulations. It is shown that the coronal magnetic field is readily braided and twisted by photospheric flows. Temperature and density contrasts form between regions with active stirring motions and those without. Stronger whirlpool-like flows in the convection, concurrent with magnetic concentrations, launch torsional Alfv\'en waves up through the magnetic funnel network, which are expected to enhance the turbulent generation of magnetic switchbacks in the solar wind.

(Abridged) Life is distinctly homochiral. The origins of this homochirality are under active debate. Recently, propylene-oxide has been detected in the gas-phase interstellar medium (ISM) (McGuire et al. 2016). The enantiomeric composition of ISM propylene-oxide may be probed through circular polarization measurements, but accurate estimates of the circular dichroism properties of the microwave transitions of propylene-oxide are not available. We develop a model of the circular dichroic activity in torsion-rotation transitions of closed-shell chiral molecules, such as propylene-oxide. With this model, we estimate the viability, and optimize observation strategies, of enantiomeric excess detection in ISM propylene-oxide. We present estimates for the dichroic activity of the torsion-rotation transitions of propylene-oxide, where we predict that the circular polarization fractions of emission lines of enantiopure propylene-oxide relevant to astronomical detection of propylene-oxide are on the order of 10^(-6). Due to the low predicted circular polarization fractions, we conclude that enantiomeric characterization of propylene-oxide in the gas phase of the ISM is impossible with current astronomical observation techniques. We suggest that only chiral radical species may be viably employed for enantiomeric excess detection. We estimate that laboratory experiments may be successful in detecting the enantiomeric composition of a mixture of propylene-oxide through microwave dichroism spectroscopy. The theory we present in this paper provides a solid theoretical underpinning for such laboratory circular dichroism measurements in microwave transitions.

In laboratory experiments, high speed videos are used to detect and track mm-size surface particle motions caused by a low velocity normal impact into sand. Outside the final crater radius and prior to the landing of the ejecta curtain, particle displacements are measured via particle image velocimetry and with a cross-correlation method. Surface particles rebound and are also permanently displaced with both peak and permanent displacements rapidly decaying as a function of distance from the crater center. The surface begins to move before most of the ejecta curtain has landed, but continues to move after the subsurface seismic pulse has decayed. Ray angles for surface and subsurface velocities are similar to those described by a Maxwell's Z-model. This implies that the flow field outside the crater excavation region is a continuation of the crater excavation flow. The ratio of final particle displacement to crater radius resembles that measured for other impact craters.

We report the Fermi-LAT gamma-ray detection of the 2021 outburst of the symbiotic recurrent nova RS Ophiuchi. In this system, unlike classical novae from cataclysmic binaries, the ejecta from the white dwarf form shocks when interacting with the dense circumstellar wind environment of the red giant companion. We find the LAT spectra from 50 MeV to ~20-23 GeV, the highest-energy photons detected in some sub-intervals, are consistent with $\pi^{\rm 0}$-decay emission from shocks in the ejecta as proposed by Tatischeff & Hernanz (2007) for its previous 2006 outburst. The LAT light-curve displayed a fast rise to its peak >0.1 GeV flux of $\simeq$6x10^-6 ph cm^-2 s^-1 beginning on day 0.745 after its optically-constrained eruption epoch of 2021 August 8.50. The peak lasted for ~1 day, and exhibited a power-law decline up to the final LAT detection on day 45. We analyze the data on shorter timescales at early times and found evidence of an approximate doubling of emission over ~200 minutes at day 2.2, possibly indicating a localized shock-acceleration event. Comparing the data collected by the AAVSO, we measured a constant ratio of ~2.8x10^-3 between the gamma-ray and optical luminosities except for a ~5x smaller ratio within the first day of the eruption likely indicating attenuation of gamma rays by ejecta material and lower high-energy proton fluxes at the earliest stages of the shock development. The hard X-ray emission due to bremsstrahlung from shock-heated gas traced by the Swift-XRT 2-10 keV light-curve peaked at day ~6, later than at GeV and optical energies. Using X-ray derived temperatures to constrain the velocity profile, we find the hadronic model reproduces the observed >0.1 GeV light-curve.

It has been proposed that some black holes (BHs) in binary black hole (BBH) systems are born from ``hierarchical mergers" (HM); i.e. earlier mergers of smaller BHs. These HM products have spin magnitudes $\chi \sim 0.7$, and, if they are dynamically assembled into BBH systems, their spin orientations will be sometimes anti-aligned with the binary orbital angular momentum. In fact, as Baibhav et al. (2020) showed, $\sim16\%$ of BBH systems that include HM products will have an effective inspiral spin parameter, $\chi_\mathrm{eff} < -0.3$. Nevertheless, the LIGO-Virgo-Kagra (LVK) gravitational-wave (GW) detectors have yet to observe a BBH system with $\chi_\mathrm{eff} \lesssim -0.2$, leading to upper limits on the fraction of HM products in the population. We fit the astrophysical mass and spin distribution of BBH systems and measure the fraction of BBH systems with $\chi_\mathrm{eff} < -0.3$, which implies an upper limit on the HM fraction. We find that fewer than $26\%$ of systems in the underlying BBH population include HM products (90\%. credibility). Even among BBH systems with primary masses $m_1=60\,M_\odot$, the HM fraction is less than 69\%, which may constrain the location of the pair-instability mass gap. With 300 GW events (to be expected in the LVK's next observing run), if we fail to observe a BBH with $\chi_\mathrm{eff} < -0.3$, we can conclude that the HM fraction is smaller than $2.5^{+9.1}_{-2.2}\%$.

The speckle interferometry program at the the 4.1 m Southern Astrophysical Research Telescope (SOAR), started in 2008, now accumulated over 30,300 individual observations of 12,700 distinct targets. Its main goal is to monitor orbital motion of close binaries, including members of high-order hierarchies and low-mass dwarfs in the solar neighborhood. The results from 2021 are published here, totaling 2,623 measurements of 2,123 resolved pairs and non-resolutions of 763 targets. The median measured separation is 0.21", and 75 pairs were closer than 30 mas. The calibration of scale and orientation is based on the observations of 103 wide pairs with well-modeled motion. These calibrators are compared to the latest Gaia data release, and minor (0.5%) systematic errors were rectified, resulting in accurate relative positions with typical errors on the order of 1 mas. Using these new measurements, orbits of 282 binaries are determined here (54 first determinations and 228 corrections). We resolved for the first time 50 new pairs, including subsystems in known binaries. A list of 94 likely spurious pairs unresolved at SOAR (mostly close Hipparcos binaries) is also given.

I report on a large-scale search for the orbital periods (P) of most known nova systems, by looking for significant, coherent, and stable optical photometric modulation in two or more independent light curves taken mostly from the large surveys of TESS, Kepler, AAVSO, SMARTS, OGLE, ASAS, and ZTF. I have discovered 31 new orbital periods. Further, I have measured new periods for 18 novae with evolved companions, to 30 per cent accuracy, as based on their spectral energy distribution. Also, I have confirmed, improved, and rejected prior claims for P in 46 novae. (As part of this effort, I recognize that 5 novae display 1--3 coherent, significant, and transient periodicities 0.12--4.1 days, with these being mysterious as not being the orbital, spin, or superhump periods.) In all, I have compiled a comprehensive list of 156 reliable P values for novae. The histogram of nova periods shows a minimum P at 0.059 hours (85 minutes), and a Period Gap from 0.071--0.111 days (1.70--2.66 hours). The upper edge of the Period Gap is significantly different between novae (0.111 days), nova-like systems (0.131 days), and dwarf novae (0.141 days). A further issue from the histogram is that 31 per cent of nova systems have evolved companions, for which there has been no models or understanding for their current state or evolution. For the novae with red giant companions, 15-out-of-20 are in the bulge population, despite novae with main-sequence and subgiant companions having bulge fractions near 0.11--0.32.

We investigate a correlation between the dark matter content of elliptical galaxies and their ellipticity that was initially reported in 2014. We use new determinations of dark matter and ellipticities that are posterior to that time. Our data set consists of 237 elliptical galaxies passing a strict set of criteria. We find a relation between the mass-to-light ratio and ellipticity that is well fit by M/L = (14.1 \pm 5.4)?, which agrees with the result reported in 2014.

We present the discovery of 17 double white dwarf (WD) binaries from our on-going search for extremely low mass (ELM) <0.3 Msun WDs, objects that form from binary evolution. Gaia parallax provides a new means of target selection that we use to evaluate our original ELM Survey selection criteria. Cross-matching the Gaia and Sloan Digital Sky Survey (SDSS) catalogs, we identify an additional 36 ELM WD candidates with 17<g<19 mag and within the 3-sigma uncertainties of our original color selection. The resulting discoveries imply the ELM Survey sample was 90% complete in the color range -0.4 < (g-r)_0 < -0.1 mag (approximately 9,000 K < Teff < 22,000 K). Our observations complete the sample in the SDSS footprint. Two newly discovered binaries, J123950.370-204142.28 and J232208.733+210352.81, have orbital periods of 22.5 min and 32 min, respectively, and are future LISA gravitational wave sources.

We present initial results of an ongoing engineering study on the feasibility of a space mission to the focal region of the solar gravitational lens (SGL). The mission goal is to conduct exoplanet imaging operations at heliocentric distances in the range ~548-900 astronomical units (AU). Starting at 548 AU from the Sun, light from an exoplanet located behind the Sun is greatly amplified by the SGL. The objective is to capture this light and use it for multipixel imaging of an exoplanet up to 100 light years distant. Using a meter-class telescope one can produce images of the exoplanet with a surface resolution measured in tens of kilometers and to identify signs of habitability. The data are acquired pixel-by-pixel while moving an imaging spacecraft within the image. Given the long duration of the mission, decades to 900 AU, we address an architecture for the fastest possible transit time while reducing mission risk and overall cost. The mission architecture implements solar sailing technologies and in-space aggregation of modularized functional units to form mission capable spacecraft. The study reveals elements of such a challenging mission, but it is nevertheless found to be feasible with technologies that are either extant or in active development.

Driven largely by multiple ground-based radial-velocity (RV) surveys and photometric space missions such as Kepler and K2, the discovery of new exoplanets has increased rapidly since the early 2000s. However, due to a target selection bias in favor of main-sequence stars, only a handful of transiting planets have been found orbiting evolved hosts. These planets, most of which are giants, hold important information regarding the formation and evolution of planetary systems. In this thesis, I sought to increase the sample of known giant planets orbiting red-giant stars, focusing on data from NASA's Transiting Exoplanet Survey Satellite (TESS) mission, and to improve their characterization. Specifically, I focused on close-in giant planets orbiting (preferably) oscillating low-luminosity red-giant branch (LLRGB) stars. To improve characterization, I developed a method to model planetary transits and stellar signals simultaneously, implementing Gaussian processes to model stellar granulation and the oscillations envelope in the time domain. My results show that the model enables time-domain asteroseismology, inferring the frequency of maximum oscillation amplitude, $\nu_\text{max}$, to within 1\%. The method's implementation is open-source and available to the community. Regarding the planet search, I assembled a pipeline, mostly comprised of third-party open-source software and explored a sample of $\sim$40,000 bright LLRGB stars in the southern hemisphere of TESS's field of view. The search identified four planet candidates, two of which are not currently known planets and orbit red-giant stars. Radial-velocity follow-up observations of both these candidates have tentatively confirmed their planetary nature. Finally, I also confirmed the planetary nature of an additional candidate, not part of the above sample, through RV observations.

We determine the time evolution of the dust particle size distribution during the collapse of a cloud core, accounting for both dust coagulation and dust fragmentation, to investigate the influence of dust growth on non-ideal magnetohydrodynamic effects.The density evolution of the collapsing core is given by a one-zone model. We assume two types of dust model: dust composed only of silicate (silicate dust) and dust with a surface covered by $\mathrm{H_{2}O}$ ice ($\mathrm{H_{2}O}$ ice dust). When only considering collisional coagulation, the non-ideal magnetohydrodynamic effects are not effective in the high-density region for both the silicate and $\mathrm{H_{2}O}$ ice dust cases. This is because dust coagulation reduces the abundance of small dust particles, resulting in less efficient adsorption of charged particles on the dust surface. For the silicate dust case, when collisional fragmentation is included, the non-ideal magnetohydrodynamic effects do apply at a high density of $n_{\mathrm{H}}>10^{12} \ \mathrm{cm^{-3}}$ because of the abundant production of small dust particles. On the other hand, for the $\mathrm{H_{2}O}$ ice dust case, the production of small dust particles due to fragmentation is not efficient. Therefore, for the $\mathrm{H_{2}O}$ ice dust case, non-ideal magnetohydrodynamic effects apply only in the range $n_{\mathrm{H}}\gtrsim 10^{14} \ \mathrm{cm^{-3}}$, even when collisional fragmentation is considered. Our results suggest that it is necessary to consider both dust collisional coagulation and fragmentation to activate non-ideal magnetohydrodynamic effects, which should play a significant role in the star and disk formation processes.

We present here a low-cost Raspberry Pi (RPi)-based star sensor StarberrySense using commercial-off-the-shelf (COTS) components, developed and built for applications in small satellites and CubeSat-based missions. A star sensor is one of the essential instruments onboard a satellite for attitude determination. However, most commercially available star sensors are expensive and bulky to be used in small satellite missions. StarberrySense is a configurable system -- it can operate as an imaging camera, a centroiding camera, or as a star sensor. We describe the algorithms implemented in the sensor, its assembly and calibration. This payload was selected by a recent Announcement of Opportunity call for payloads to fly on the PS4-Orbital Platform by the Indian Space Research Organization (ISRO).

Similarly to warm dark matter which features a cut-off in the matter power spectrum due to free-streaming, many interacting dark matter models predict a suppression of the matter power spectrum on small length scales through collisional damping. Forecasts for 21cm line intensity mapping have shown that the Square Kilometre Array (SKA) will be able to probe a suppression of power in warm dark matter scenarios in a statistically significant way. Here we investigate the implications of these findings on interacting dark matter scenarios, particularly dark matter-neutrino interactions, which we use as an example. Using a suite of cosmological $N$-body simulations, we demonstrate that SKA will be able to set the strongest limits yet on dark matter-neutrino scattering, improving the constraints by two orders of magnitude over current Lyman-$\alpha$ bounds, and by four orders of magnitude over cosmic microwave background and baryon acoustic oscillations limits. However, to distinguish between warm dark matter and interacting scenarios, our simulations show that percent-level precision measurements of the matter power spectrum at redshifts $z\gtrsim15$ are necessary, as the key features of interacting scenarios are washed out by non-linear evolution at later times.

We perform a Bayesian analysis for small field models of inflation, using the most recent datasets produced by Planck`18, ACTPol, and BICEP3. We employ Artificial Neural Networks (ANN) to perform analyses with model coefficients, instead of their proxy slow-roll parameters. The ANN connects the models with their projected scalar index $n_s$ and index running $\alpha$, in lieu of the less accurate Lyth-Riotto expressions. We recover the most likely coefficients for a sixth degree polynomial inflationary potential, which yields a tensor-to-scalar ratio $r\lesssim 0.03$. We do so for the case of joint Planck and ACTPol datasets, and for each dataset alone. The BICEP3 data is included in all three analyses. We show that these models are likely, with coefficients that are tuned to about $\Delta\gtrsim 1/60$. Curiously, we also find a significant tension between ACTPol and Planck datasets, which we try to account for.

We present two approaches to determine the dynamical stability of a hierarchical triple-star system. The first is an improvement on the semi-analytical stability criterion of Mardling & Aarseth (2001), where we introduce a dependence on inner orbital eccentricity and improve the dependence on mutual orbital inclination. The second involves a machine learning approach, where we use a multilayer perceptron (MLP) to classify triple-star systems as `stable' and `unstable'. To achieve this, we generate a large training data set of 10^6 hierarchical triples using the N-body code MSTAR. Both our approaches perform better than the original Mardling & Aarseth (2001) stability criterion, with the MLP model performing the best. The improved stability formula and the machine learning model have overall classification accuracies of 93 % and 95 % respectively. Our MLP model, which accurately predicts the stability of any hierarchical triple-star system within the parameter ranges studied with almost no computation required, is publicly available on Github in the form of an easy-to-use Python script.

Classic solar models put the Chromosphere-Corona Transition Region (CCTR} at $\sim2$Mm above the $\tau_{5000} = 1$ level, whereas rMHD models place it in a wider range of heights. Observational verification is scarce. We review and discuss recent results from various instruments and spectral domains. In SDO and TRACE images spicules appear in emission in the 1600, 1700 and 304 A bands and in absorption in the EUV bands; the latter is due to photo-ionization of H and He I. At the shortest available AIA wavelength and taking into account that the photospheric limb is $\sim0.34$Mm above the $\tau_{5000}=1$ level, we found that CCTR emission starts at $\sim3.7$Mm; extrapolating to $\lambda=0$, where there is no chromospheric absorption, we deduced a height of $3.0\pm 0.5$Mm, above the value of 2.14Mm of the Avrett & Loeser model. Another indicator of the extent of the chromosphere is the height of the network structures. Height differences produce a limbward shift of features with respect to their counterparts in magnetograms. Using this approach, we measured heights of $0.14\pm0.04$Mm (at 1700 A), $0.31\pm0.09$Mm (at 1600 A) and $3.31\pm 0.18$Mm (at 304 A) for the center of the solar disk. A previously reported possible solar cycle variation is not confirmed. A third indicator is the position of the limb in the UV, where IRIS observations of the Mg II triplet lines show that they extend up to $\sim2.1$Mm above the 2832 A limb, while AIA/SDO images give a limb height of $1.4 \pm 0.2$Mm (1600 A) and $5.7\pm 0.2$Mm (304 A). Finally, ALMA mm-$\lambda$ full-disk images provide useful diagnostics, though not very accurate; values of $2.4\pm0.7$Mm at 1.26mm and $4.2\pm2.5$Mm at 3mm were obtained. Putting everything together, we conclude that the average chromosphere extends higher than homogeneous models predict, but within the range of rMHD models.

Coronal mass ejections (CMEs) are large scale eruptions observed close to the Sun. They are travelling through the heliosphere and possibly interacting with the Earth environment creating interruptions or even damaging new technology instruments. Most of the time their physical conditions (velocity, density, pressure) are only measured in situ at one point in space, with no possibility to have information on the variation of these parameters during their journey from Sun to Earth. Our aim is to understand the evolution of internal physical parameters of a set of three particular fast halo CMEs. These CMEs were launched between 15 and 18 July 2002. Surprisingly, the related interplanetary CMEs (ICMEs), observed near Earth, have a low, and in one case even very low, plasma density. We use the EUropean Heliosphere FORecasting Information Asset (EUHFORIA) model to simulate the propagation of the CMEs in the background solar wind by placing virtual spacecraft along the Sun--Earth line. We set up the initial conditions at 0.1 au, first with a cone model and then with a linear force free spheromak model. A relatively good agreement between simulation results and observations concerning the speed, density and arrival times of the ICMEs is obtained by adapting the initial CME parameters. In particular, this is achieved by increasing the initial magnetic pressure so that a fast expansion is induced in the inner heliosphere. This implied the develop First, we show that a magnetic configuration with an out of force balance close to the Sun mitigates the EUHFORIA assumptions related to an initial uniform velocity. Second, the over-expansion of the ejected magnetic configuration in the inner heliosphere is one plausible origin for the low density observed in some ICMEs at 1 au. The in situ observed very low density has a possible coronal origin of fast expansion for two of the three ICMEs.

Dust polarization observations at optical wavelengths help to understand the dust grain properties and trace the plane-of-the-sky component of the magnetic field. In this study, we make use of the $I$-band polarization data acquired from AIMPOL along with the distances ($d$) and extinction ($A_{V}$) data to study the variation of polarization fraction ($P$) as a function of $A_{V}$ and $d$ towards the star-forming region, NGC 1893. We employ a broken power-law fit and Bayesian analysis on extinction ($A_{V}$) versus polarization efficiency ($P$/$A_{V}$) and distance ($d$) versus rate of polarization ($P$/$d$). We find that $P$/$A_{V}$ shows a break at an extinction of $\sim$0.9 mag, whereas $P/d$ exhibits a break at a distance of $\sim$1.5 kpc. Based on these, we categorize the dust towards NGC 1893 into two populations: (i) foreground dust confined to $A_{V}$ $<$ $\sim$1 mag and distance up to $\sim$2 kpc and (ii) Perseus spiral arm dust towards NGC 1893 characterized with $A_{V}$ $>$ $\sim$1 mag and distance beyond $\sim$2 kpc. Foreground dust exhibits higher polarization efficiency but a lower polarization rate, whereas Perseus dust shows a lower polarization efficiency but a slightly higher polarization rate. Hence, we suggest that while polarization efficiency reveals the dust grain alignment, the rate of polarization infers about the distribution of dust grains towards NGC 1893. Further, we also shed a light on the spatial variation of intrinsic polarization and magnetic field orientation, and other parameters within the intra-cluster medium of NGC 1893.

We present an astrometric and photometric wide-field study of the Galactic open star cluster M37 (NGC 2099). The studied field was observed with ground-based images covering a region of about four square degrees in the Sloan-like filters ugi. We exploited the Gaia catalogue to calibrate the geometric distortion of the large field mosaics, developing software routines that can be also applied to other wide-field instruments. The data are used to identify the hottest white dwarf (WD) member candidates of M37. Thanks to the Gaia EDR3 exquisite astrometry we identified seven such WD candidates, one of which, besides being a high-probability astrometric member, is the putative central star of a planetary nebula. To our knowledge, this is a unique object in an open cluster, and we have obtained follow-up low-resolution spectra that are used for a qualitative characterisation of this young WD. Finally, we publicly release a three-colour atlas and a catalogue of the sources in the field of view, which represents a complement of existing material.

The times of minima of the bright, eccentric eclipsing binary RR Lyncis are re-investigated. From the TESS data it is found that significant differences in the eclipse timings, particularly for the primary minima, are probably due to small, irregular changes in the eclipse profile due to pulsations, rather than light-curve asymmetries.

Our understanding of stellar structure and evolution coming from one-dimensional (1D) stellar models is limited by uncertainties related to multi-dimensional processes taking place in stellar interiors. 1D models, however, can now be tested and improved with the help of detailed three-dimensional (3D) hydrodynamics models, which can reproduce complex multi-dimensional processes over short timescales, thanks to the recent advances in computing resources. Among these processes, turbulent entrainment leading to mixing across convective boundaries is one of the least understood and most impactful. Here we present the results from a set of hydrodynamics simulations of the neon-burning shell in a massive star, and interpret them in the framework of the turbulent entrainment law from geophysics. Our simulations differ from previous studies in their unprecedented degree of realism in reproducing the stellar environment. Importantly, the strong entrainment found in the simulations highlights the major flaws of the current implementation of convective boundary mixing in 1D stellar models. This study therefore calls for major revisions of how convective boundaries are modelled in 1D, and in particular the implementation of entrainment in these models. This will have important implications for supernova theory, nucleosynthesis, neutron stars and black holes physics.

High-sensitivity X-ray polarimetric observations of black hole X-ray binaries, which will soon become available with the launches of space-borne X-ray observatories with sensitive X-ray polarimeters, will be able to put independent constraints on the black hole as well as the accretion flow, and possibly break degeneracies that cannot be resolved by spectral/timing observations alone. In this work we perform a series of general relativistic Monte-Carlo radiative transfer simulations to study the expected polarization properties of X-ray radiation emerging from lamp-post coronae in black hole X-ray binaries. We find that the polarization degree of the coronal emission of black hole X-ray binaries is sensitive to the spin of the black hole, the height of the corona, and the dynamics of the corona.

We measure escape fractions, $f_{\rm esc}$, of ionizing radiation from galaxies in the SPHINX suite of cosmological radiation-hydrodynamical simulations of reionization, resolving halos with $M_{\rm vir} \gtrapprox 7.5 \times 10^7 \ M_{\odot}$ with a minimum cell width of $\approx 10$ pc. Our new and largest $20$ co-moving Mpc wide volume contains tens of thousands of star-forming galaxies with halo masses up to a few times $10^{11} \ M_{\odot}$. The simulated galaxies agree well with observational constraints of the UV luminosity function in the Epoch of Reionization. The escape fraction fluctuates strongly in individual galaxies over timescales of a few Myrs, due to its regulation by supernova and radiation feedback, and at any given time a tiny fraction of star-forming galaxies emits a large fraction of the ionizing radiation escaping into the inter-galactic medium. Statistically, $f_{\rm esc}$ peaks in intermediate-mass, intermediate-brightness, and low-metallicity galaxies ($M_{*} \approx 10^7 \ M_{\odot}$, $M_{1500} \approx -17$, $Z\lesssim 5 \times 10^{-3} \ Z_{\odot}$), dropping strongly for lower and higher masses, brighter and dimmer galaxies, and more metal-rich galaxies. The escape fraction correlates positively with both the short-term and long-term specific star formation rate. According to SPHINX, galaxies too dim to be yet observed, with $M_{1500} \gtrapprox -17$, provide about $55$ percent of the photons contributing to reionization. The global averaged $f_{\rm esc}$ naturally decreases with decreasing redshift, as predicted by UV background models and low-redshift observations. This evolution is driven by decreasing specific star formation rates over cosmic time.

We have studied the spin-down induced phase transition in cold, isolated neutron stars in this work. After birth, as the star slows down, its central density rises and crosses the critical density of phase transition, and a quark core is seeded inside the star. Intermediate mass stars are more likely to have a quark seeding in their lifetime at birth. Smaller neutron stars do not have a quark core and remain neutron stars throughout their life, whereas in massive stars, a quark core exists at their center from birth. In intermediate and massive stars, the quark core grows further as the star slows down. The appearance of a quark core leads to a sudden change in the moment of inertia of the star in its evolutionary history, and it is also reflected in a sudden discontinuity in the braking index of the star (at the frequency where the quark core first seeds). The energy released during the phase transition process as the quark core is seeded can excite the f-mode oscillation in the star and is emitted in the form of the gravitational wave, which is in the range of detection with present operating detectors; however, future detectors will enable a more clean extraction of this signals. Also, neutrinos and bursts of gamma-rays can originate from phase transition events. The spin-down induced phase transition could be gradual or in the form of subsequent leaps producing persistent or multiple transient emissions.

Searching for variations of nature's fundamental constants is a crucial step in our quest to go beyond our current standard model of fundamental physics. If they exist, such variations will be very likely driven by the existence of a new fundamental field. The Bekenstein model and its extensions introduce such a scalar field in a purely phenomenological way, inducing a variation of the fine-structure constant on cosmological scales. This theoretical framework is as simple and general as possible while still preserving all the symmetries of standard quantum electrodynamics. When allowing for couplings to the other sectors of the Universe, such as baryons, dark matter, and the cosmological constant, the Bekenstein model is expected to reproduce the low energy limits of several grand unification, quantum gravity, and higher dimensional theories. In this work, we constrain different versions of the Bekenstein model by confronting the full cosmological evolution of the field with an extensive set of astrophysical, cosmological, and local measurements. We show that couplings of the order of parts per million (ppm) are excluded for all the cases considered, imposing strong restrictions on theoretical frameworks aiming to deal with variations of the fine-structure constant.

We present the detector performance and early science results from GRBAlpha, a 1U CubeSat mission, which is a technological pathfinder to a future constellation of nanosatellites monitoring gamma-ray bursts (GRBs). GRBAlpha was launched in March 2021 and operates on a 550 km altitude sun-synchronous orbit. The gamma-ray burst detector onboard GRBAlpha consists of a 75x75x5 mm CsI(Tl) scintillator, read out by a dual-channel multi-pixel (SiPM) photon counter (MPPC) setup. It is sensitive in the ~30-900 keV range. The main goal of GRBAlpha is the in-orbit demonstration of the detector concept, verification of the detector's lifetime, and measurement of the background level on low-Earth orbit, including regions inside the outer Van Allen radiation belt and in the South Atlantic Anomaly. GRBAlpha has already detected five, both long and short, GRBs and was even able to detect two GRBs within 8 hours, proving that nanosatellites can be used for routine detection of gamma-ray transients. For one GRB, we were able to obtain a high resolution spectrum and compare it with measurements from the Swift satellite. We find that, due to the variable background, about 67% of the low-Earth polar orbit is suitable for gamma-ray burst detection. One year after launch, the detector performance is good and the degradation of the SiPM photon counters remains at an acceptable level. The same detector system, but double in size, was launched in January 2022 on VZLUSAT-2 (3U CubeSat). It performs well and already detected three GRBs and two solar flares. Here, we present early results from this mission as well.

We investigate the exoplanet candidate TOI-1422b, which was discovered by the TESS space telescope around the high proper-motion G2V star TOI-1422 ($V=10.6$ mag), 155pc away, with the primary goal of confirming its planetary nature and characterising its properties. We monitored TOI-1422 with the HARPS-N spectrograph for 1.5 years to precisely quantify its radial velocity variation. The radial velocity measurements are analyzed jointly with TESS photometry and we also check for blended companions through high-spatial resolution images using the AstraLux instrument. We estimate that the parent star has a radius and a mass of $R^*=1.019_{-0.013}^{+0.014} R_{\odot}$, $M^*=0.981_{-0.065}^{+0.062} M_{\odot}$, respectively. Our analysis confirms the planetary nature of TOI-1422b and also suggests the presence of a Neptune-mass planet on a more distant orbit, the candidate TOI-1422c, which is not detected in TESS light curves. The inner planet, TOI-1422b, orbits on a period $P_{\rm b}=12.9972\pm0.0006$ days and has an equilibrium temperature $T_{\rm eq, b}=867\pm17$ K. With a radius of $R_{\rm b}=3.96^{+0.13}_{-0.11} R_{\oplus}$, a mass of $M_{\rm b}=9.0^{+2.3}_{-2.0} M_{\oplus}$ and, consequently, a density of $\rho_{\rm b}=0.795^{+0.290}_{-0.235}$ g cm$^{-3}$, it can be considered a warm Neptune-size planet. Compared to other exoplanets of similar mass range, TOI-1422b is among the most inflated ones and we expect this planet to have an extensive gaseous envelope that surrounds a core with a mass fraction around $10\%-25\%$ of the total mass of the planet. The outer non-transiting planet candidate, TOI-1422c, has an orbital period of $P_{\rm c}=29.29^{+0.21}_{-0.20}$ days, a minimum mass, $M_{\rm c}\sin{i}$, of $11.1^{+2.6}_{-2.3} M_{\oplus}$, an equilibrium temperature of $T_{\rm eq, c}=661\pm13$ K and, therefore, if confirmed, it could be considered as another warm Neptune.

The outstanding mass growth of supermassive black holes (SMBHs) at the Reionisation Epoch and how it is related to the concurrent growth of their host galaxies, poses challenges to theoretical models aimed at explaining how these systems formed in short timescales (<1 Gyr). To trace the average evolutionary paths of quasi-stellar objects (QSOs) and their host galaxies in the BH mass-host mass ($M_{\rm dyn}$) plane, we compare the star formation rate (SFR), derived from the accurate estimate of the dust temperature and the dust mass ($T_{\rm dust}, M_{\rm dust}$), with the BH accretion rate. To this aim, we analysed a deep, $900$ pc resolution ALMA observation of the sub-mm continuum, [CII] and H$_2$O of the $z\sim 6$ QSO J2310+1855, enabling a detailed study of dust properties and cold gas kinematics. We performed an accurate SED analysis obtaining a dust temperature of $T_{\rm dust} = 71$ K and a dust mass of $M_{\rm dust}= 4.4 \times 10^8\ \rm M_{\odot}$. The implied AGN-corrected SFR is $1240 \ \rm M_{\odot}yr^{-1}$, a factor of 2 smaller than previously reported for this QSO. We derived the best estimate of the dynamical mass $M_{\rm dyn} = 5.2\times 10^{10}\ \rm M_{\odot}$ within $r = 1.7$ kpc, based on a dynamical model of the system. We found that ${\rm SFR}/M_{\rm dyn}>\dot M_{\rm BH}/M_{\rm BH}$, suggesting that AGN feedback might be efficiently acting to slow down the SMBH accretion, while the stellar mass assembly is still vigorously taking place in the host galaxy. In addition, we were also able to detect high-velocity emission on the red and blue sides of the [CII] emission line, that traces a gaseous outflow, and for the first time, we mapped a spatially-resolved water vapour disk through the H$_2$O v=0 $3_{(2,2)}-3_{(1,3)}$ emission line detected at $\nu_{\rm obs} = 274.074$ GHz, whose kinematic properties and size are broadly consistent with those of the [CII] disk.

Over the last few years, the detection of gravitational waves from binary neutron star systems has rekindled our hopes for a deeper understanding of the unknown nature of ultra dense matter. In particular, gravitational wave constraints on the tidal deformability of a neutron star can be translated into constraints on several neutron star properties using a set of universal relations. Apart from binary neutron star mergers, supernova explosions are also important candidates for the detection of multimessenger signals. Such observations may allow us to impose significant constraints on the binding energy of neutron stars. The purpose of the present study is twofold. Firstly, we investigate the agreement of finite temperature equations of state with established universal relations. Secondly, we examine the possible existence of a universal relation between the binding energy and the dimensionless tidal deformability, which are the bulk properties connected to the most promising sources for multimessenger signals. We find that hot equations of state are not always compatible with accepted universal relations. Therefore, the use of such expressions for probing general relativity or imposing constraints on the structure of neutron stars would be inconclusive (when thermal effects are present). Additionally, we show that the binding energy and the dimensionless tidal deformability exhibit a universal trend at least for moderate neutron star masses. The latter allows us to set bounds on the binding energy of a 1.4 $M_\odot$ neutron star using data from the GW170817 event. Finally, we provide a relation between the compactness, the binding energy and the dimensionless tidal deformability of a neutron star, that is not only independent on the employed equation of state but also holds when thermal effects are present.

We present an experimental instrument that performs laboratory-based gas-phase Terahertz Desorption Emission Spectroscopy (THz-DES) experiments in support of astrochemistry. The measurement system combines a terahertz heterodyne radiometer that uses room temperature semiconductor mixer diode technology previously developed for the purposes of Earth observation, with a high-vacuum desorption gas cell and high-speed digital sampling circuitry to enable high spectral and temporal resolution spectroscopy of molecular species with thermal discrimination. During use, molecules are condensed onto a liquid nitrogen cooled metal finger to emulate ice structures that may be present in space. Following deposition, thermal desorption is controlled and initiated by means of a heater and monitored via a temperature sensor. The 'rest frequency' spectral signatures of molecules released into the vacuum cell environment are detected by the heterodyne radiometer in real-time and characterised with high spectral resolution. To demonstrate the viability of the instrument, we have studied Nitrous Oxide (N2O). This molecule strongly emits within the terahertz (sub-millimetre wavelength) range and provide a suitable test gas and we compare the results obtained with more traditional techniques such as quadrupole mass spectrometry. The results obtained allow us to fully characterize the measurement method and we discuss its potential use as a laboratory tool in support of astrochemical observations of molecular species in the interstellar medium and the Solar System.

We investigate the effect of mass-loading from embedded clouds on the evolution of wind-blown bubbles. We use 1D hydrodynamical calculations and assume that the clouds are numerous enough that they can be treated in the continuous limit, and that rapid mixing occurs so that the injected mass quickly merges with the global flow. The destruction of embedded clouds adds mass into the bubble, increasing its density. Mass-loading increases the temperature of the unshocked stellar wind due to the frictional drag, and reduces the temperature of the hot shocked gas as the available thermal energy is shared between more particles. Mass-loading may increase or decrease the volume-averaged bubble pressure. Mass-loaded bubbles are smaller, have less retained energy and lower radial momentum, but in all cases examined are still able to do significant $PdV$ work on the swept-up gas. In this latter respect, the bubbles more closely resemble energy-conserving bubbles than the momentum-conserving-like behaviour of ``quenched'' bubbles.

We investigate the mass structure of a strong lens galaxy at $z=0.35$, taking advantage of the milli-arcsecond angular resolution of very long baseline interferometric (VLBI) observations. In the first analysis of its kind at this resolution, we jointly infer the lens model parameters and the pixellated radio source surface brightness. We consider several lens models of increasing complexity, starting from a simple elliptical power-law density profile. We extend this model to include angular multipole structures, a separate stellar mass component, additional nearby field galaxies, and/or a generic external potential. We compare these models using their relative Bayesian log-evidence (Bayes factor). We find strong evidence for angular structure in the lens; our best model is comprised of a power-law profile plus multipole perturbations and external potential, with a Bayes factor of $+14984$ relative to the elliptical power-law model. It is noteworthy that the elliptical power-law mass distribution is a remarkably good fit on its own, with additional model complexity correcting the deflection angles only at the $\sim5$ mas level. We also consider the effects of added complexity in the lens model on time-delay cosmography and flux-ratio analyses. We find that an overly simplistic power-law ellipsoid lens model can bias the measurement of $H_0$ by $\sim3$ per cent and mimic flux ratio anomalies of $\sim8$ per cent. Our results demonstrate the power of high-resolution VLBI observations to provide strong constraints on the inner density profiles of lens galaxies.

We introduce the response function (RFs) approach to model the weak lensing statistics in the context of separate universe formalism. Numerical results for the RFs are presented for various semi-analytical models that include perturbative modelling and variants of halo models. These results extend the recent studies of the Integrated Bispectrum (IB) and Trispectrum to arbitrary order. We find that due to the line-of-sight (los) projection effects, the expressions for RFs are not identical to the squeezed correlation functions of the same order. We compute the RFs in three-dimensions (3D) using the spherical Fourier-Bessel (sFB) formalism which provides a natural framework for incorporating photometric redshifts, and relate these expressions to tomographic and projected statistics. We generalise the concept of $k$-cut power spectrum to $k$-cut response functions. In addition to the response function for high-order spectra, we also define their counterparts in real space, since they are easier to estimate from surveys with low sky-coverage and non-trivial survey boundaries.

We have analyzed the kinematics of 9750 OB2 stars with proper motions and parallaxes selected by Xu et al. from the Gaia EDR3 catalogue. The relative parallax errors for these stars do not exceed 10\%. Based on the entire sample of stars, we have found the velocities $(U,V)_\odot=(7.17,7.37)\pm(0.16,0.24)$ km s$^{-1}$ and the components of the angular velocity of Galactic rotation: $\Omega_0 =29.700\pm0.076$ km s$^{-1}$ kpc$^{-1}$, $\Omega^{'}_0 =-4.008\pm0.022$ km s$^{-1}$ kpc$^{-2}$, and $\Omega^{''}_0 = 0.671\pm0.011$ km s$^{-1}$ kpc$^{-3}$, where the linear rotation velocity of the Galaxy at the solar distance is $V_0=240.6\pm3.0$ km s$^{-1}$ for the adopted $R_0=8.1\pm0.1$ kpc. There are 1812 OB2 stars with measured line-of-sight velocities, and the space velocities $V_R$ and $\Delta V_{circ}$ have been calculated from them. Based on a spectral analysis independently for the radial and residual tangential velocities, we have obtained the following estimates: $f_R=4.8\pm0.7$ km s$^{-1}$, $f_\theta=4.1\pm0.9$ km s$^{-1}$, $\lambda_R=2.1\pm0.2$ kpc, $\lambda_\theta=2.2\pm0.4$ kpc, $(\chi_\odot)_R=-116\pm12^\circ$, and $(\chi_\odot)_\theta=-156\pm14^\circ$ for the adopted four-armed ($m = 4$) spiral pattern. Thus, both velocity perturbation amplitudes are nonzero at a high significance level.

The interstellar detections of isocyanic acid, methyl isocyanate, and very recently also ethyl isocyanate, open the question of the possible detection of vinyl isocyanate in the interstellar medium. The aim of this study is to extend the laboratory rotational spectrum of vinyl isocyanate into the millimeter wave region and to undertake a check for its presence in the high-mass star forming region Sgr B2. The rotational spectrum of vinyl isocyanate was recorded in the frequency regions 127.5-218 and 285-330 GHz using the Prague millimeter wave spectrometer. The spectral analysis was supported by high-level quantum-chemical calculations. We assumed local thermodynamic equilibrium to compute synthetic spectra of vinyl isocyanate and to search for it in the ReMoCA survey performed with ALMA toward Sgr B2(N). We also searched for ethyl isocyanate in the same source. Accurate values for the rotational and centrifugal distortion constants are reported for the ground vibrational states of trans and cis vinyl isocyanate. We report nondetections of vinyl and ethyl isocyanate toward the main hot core of Sgr B2(N). We find that vinyl and ethyl isocyanate are at least 11 and 3 times less abundant than methyl isocyanate in this source, respectively. Although the precise formation mechanism of interstellar methyl isocyanate itself remains uncertain, we infer from existing astrochemical models that our observational upper limit for the CH3NCO:C2H5NCO ratio in Sgr B2(N) is consistent with ethyl isocyanate being formed on dust grains via the abstraction or photodissociation of an H atom from methyl isocyanate, followed by the addition of a methyl radical. The dominance of such a process for ethyl isocyanate production, combined with the absence of an analogous mechanism for vinyl isocyanate, would indicate that the ratio C2H3NCO:C2H5NCO should be rather less than unity.

Data from ground-based gravitational-wave detectors contains numerous short-duration instrumental artifacts, called "glitches." The high rate of these artifacts in turn results in a significant fraction of gravitational-wave signals from compact binary coalescences overlapping glitches. In LIGO-Virgo's third observing run, $\approx 20\%$ of signals required some form of mitigation due to glitches. This was the first observing run that glitch subtraction was included as a part of LIGO-Virgo-KAGRA data analysis methods for a large fraction of detected gravitational-wave events. This work describes the methods to identify glitches, the decision process for deciding if mitigation was necessary, and the two algorithms, BayesWave and gwsubtract, that were used to model and subtract glitches. Through case studies of two events, GW190424_180648 and GW200129_065458, we evaluate the effectiveness of the glitch subtraction, compare the statistical uncertainties in the relevant glitch models, and identify potential limitations in these glitch subtraction methods. We finally outline the lessons learned from this first-of-its-kind effort for future observing runs.

With the advent of ALMA, it is now possible to observationally constrain how disks form around deeply embedded protostars. In particular, the recent ALMA C3H2 line observations of the nearby protostar L1527 have been interpreted as evidence for the so-called "centrifugal barrier," where the protostellar envelope infall is gradually decelerated to a stop by the centrifugal force in a region of super-Keplerian rotation. To test the concept of centrifugal barrier, which was originally based on angular momentum conserving-collapse of a rotating test particle around a fixed point mass, we carry out simple axisymmetric hydrodynamic simulations of protostellar disk formation including a minimum set of ingredients: self-gravity, rotation, and a prescribed viscosity that enables the disk to accrete. We find that a super-Keplerian region can indeed exist when the viscosity is relatively large but, unlike the classic picture of centrifugal barrier, the infalling envelope material is not decelerated solely by the centrifugal force. The region has more specific angular momentum than its surrounding envelope material, which points to an origin in outward angular momentum transport in the disk (subject to the constraint of disk expansion by the infalling envelope), rather than the spin-up of the envelope material envisioned in the classic picture as it falls closer to the center in order to conserve angular momentum. For smaller viscosities, the super-Keplerian rotation is weaker or non-existing. We conclude that, despite the existence of super-Keplerian rotation in some parameter regime, the classic picture of centrifugal barrier is not supported by our simulations.

We study relativistic effects, arising from the light propagation in an inhomogeneous universe. We particularly investigate the effects imprinted in a cross-correlation function between galaxy positions and intrinsic galaxy shapes (GI correlation). Considering the Doppler and gravitational redshift effects as major relativistic effects, we present an analytical model of the GI correlation function, from which we find that the relativistic effects induce non-vanishing odd multipole anisotropies. Focusing particularly on the dipole anisotropy, we show that the Doppler effect dominates at large scales, while the gravitational redshift effect originated from the halo potential dominates at the scales below $10$-$30\, {\rm Mpc}/h$, with the amplitude of the dipole GI correlation being positive over all the scales. Also, we newly derive the covariance matrix for the modelled GI dipole. Taking into account the full covariance, we estimate the signal-to-noise ratio and show that the GI dipole induced by the relativistic effects is detectable in future large-volume galaxy surveys. We discuss how the measurement of dipole GI correlation could be helpful to detect relativistic effects in combination with the conventional galaxy-galaxy cross correlation.

We report high-precision X-ray monitoring observations in the 0.4-10 keV band of the luminous, long-period colliding-wind binary Eta Carinae up to and through its most recent X-ray minimum/periastron passage in February 2020. Eta Carinae reached its observed maximum X-ray flux on 7 January 2020, at a flux level of $3.30 \times 10^{-10}$ ergs s$^{-1}$ cm$^{-2}$, followed by a rapid plunge to its observed minimum flux, $0.03 \times 10^{-10}$ ergs s$^{-1}$ cm$^{-2}$ near 17 February 2020. The NICER observations show an X-ray recovery from minimum of only $\sim$16 days, the shortest X-ray minimum observed so far. We provide new constraints of the "deep" and "shallow" minimum intervals. Variations in the characteristic X-ray temperature of the hottest observed X-ray emission indicate that the apex of the wind-wind "bow shock" enters the companion's wind acceleration zone about 81 days before the start of the X-ray minimum. There is a step-like increase in column density just before the X-ray minimum, probably associated with the presence of dense clumps near the shock apex. During recovery and after, the column density shows a smooth decline, which agrees with previous $N_{H}$ measurements made by SWIFT at the same orbital phase, indicating that changes in mass-loss rate are only a few percent over the two cycles. Finally, we use the variations in the X-ray flux of the outer ejecta seen by NICER to derive a kinetic X-ray luminosity of the ejecta of $\sim 10^{41}$ ergs s$^{-1}$ near the time of the "Great Eruption'.

Measuring the structural parameters (size, total brightness, light concentration, etc.) of galaxies is a significant first step towards a quantitative description of different galaxy populations. In this work, we demonstrate that a Bayesian Neural Network (BNN) can be used for the inference, with uncertainty quantification, of such morphological parameters from simulated low-surface-brightness galaxy images. Compared to traditional profile-fitting methods, we show that the uncertainties obtained using BNNs are comparable in magnitude, well-calibrated, and the point estimates of the parameters are closer to the true values. Our method is also significantly faster, which is very important with the advent of the era of large galaxy surveys and big data in astrophysics.

One of the strongest ${\rm Na~I}$ features was observed in WASP-96b. To confirm this novel detection, we provide a new 475-825nm transmission spectrum obtained with Magellan/IMACS, which indeed confirms the presence of a broad sodium absorption feature. We find the same result when reanalyzing the 400-825nm VLT/FORS2 data. We also utilize synthetic data to test the effectiveness of two common detrending techniques: (1) a Gaussian processes (GP) routine, and (2) common-mode correction followed by polynomial correction (CMC+Poly). We find that both methods poorly reproduce the absolute transit depths but maintain their true spectral shape. This emphasizes the importance of fitting for offsets when combining spectra from different sources or epochs. Additionally, we find that for our datasets both methods give consistent results, but CMC+Poly is more accurate and precise. We combine the Magellan/IMACS and VLT/FORS2 spectra with literature 800-1644nm HST/WFC3 spectra, yielding a global spectrum from 400-1644nm. We used the PLATON and Exoretrievals retrieval codes to interpret this spectrum, and find that both yield relatively deeper pressures where the atmosphere is optically thick at log-pressures between $1.3^{+1.0}_{-1.1}$ and 0.29$^{+1.86}_{-2.02}$ bars, respectively. Exoretrievals finds a solar to super-solar ${\rm Na~I}$ and ${\rm H_2O}$ log-mixing ratios of $-5.4^{+2.0}_{-1.9}$ and $-4.5^{+2.0}_{-2.0}$, respectively, while PLATON finds an overall metallicity of $log_{10}(Z/Z_{\odot}) = -0.49^{+1.0}_{-0.37}$dex. Therefore, our findings are in agreement with literature and support the inference that the terminator of WASP-96b has few aerosols obscuring prominent features in the optical to near-infrared (near-IR) spectrum.

We propose a new probe of cosmic relic neutrinos (C$\nu$B) using their resonant scattering against cosmogenic neutrinos. Depending on the lightest neutrino mass and the energy spectrum of the cosmogenic neutrino flux, a Standard Model vector meson (such as a hadronic $\rho$) resonance can be produced via $\nu\bar{\nu}$ annihilation. This leads to a distinct absorption feature in the cosmogenic neutrino flux at an energy solely determined by the meson mass and the neutrino mass, apart from redshift. By numerical coincidence, the position of the $\rho$-resonance overlaps with the originally predicted peak of the Greisen-Zatsepin-Kuzmin (GZK) neutrino flux, which offers an enhanced absorption effect at higher redshifts. We show that this absorption feature in the GZK neutrino flux may be observable in future radio-based neutrino observatories, such as IceCube-Gen2 radio, provided there exists a large overdensity in the C$\nu$B distribution. This therefore provides a new probe of C$\nu$B clustering at large redshifts, complementary to the laboratory probes (such as KATRIN) at zero redshift.

We investigate a minimal singlet-scalar extension to the Standard Model that achieves a strong first-order electroweak phase transition. The singlet can be naturally light because of an approximate shift symmetry and no extra hierarchy problem beyond that of the Standard Model Higgs is introduced. We discuss the two-field dynamics of the phase transition in detail and find that the gravitational-wave signal is too weak to be detected by near-future observations. We also discuss the meta-stability of the zero-temperature scalar potential. Despite the apparent instability just above the electroweak scale, we show that the lifetime of the electroweak vacuum is much longer than the age of the universe and hence the setup does not require UV completion near the electroweak scale. The baryon asymmetry of the universe may be explained by local electroweak baryogenesis arising from a coupling between the singlet and weak gauge boson. The predicted electron electric dipole moment is much below the current bound. The viable parameter space can be probed by the observations of rare Kaon decay and the cosmic microwave background.

Hydrocarbon mixtures are extremely abundant in the Universe, and diamond formation from them can play a crucial role in shaping the interior structure and evolution of planets. With first-principles accuracy, we first estimate the diamond nucleation rate in pure liquid carbon, and then reveal the nature of chemical bonding in hydrocarbons at extreme conditions. We finally establish the pressure-temperature phase boundary where diamond can form from hydrocarbon mixtures with different atomic fractions of carbon. Notably, we find a depletion zone in Neptune (but not Uranus) where diamond formation is thermodynamically favorable regardless of the carbon atomic fraction, due to a phase separation mechanism. These findings can lead to a better understanding of the physics of planetary formation and evolution, and help explain the low luminosity of Uranus.

Gyroscopic systems in classical and quantum field theory are characterized by the presence of at least two scalar degrees of freedom and by terms that mix fields and their time derivatives in the quadratic Lagrangian. In Minkowski spacetime, they naturally appear in the presence of a coupling among fields with time-dependent vacuum expectation values and fields with space-dependent vacuum expectation values, breaking spontaneously Lorentz symmetry; this is the case for a supersolid. In a cosmological background a gyroscopic system can also arise from the time dependence of non-diagonal kinetic and mass matrices. We study the classical and quantum dynamics computing the correlation functions on the vacuum state that minimizes the energy. Two regions of stability in parameter space are found: in one region, dubbed normal, the Hamiltonian is positive defined, while in the second region, dubbed anomalous, it has no definite sign. Interestingly, in the anomalous region the 2-point correlation function exhibits a resonant behaviour in a certain region of parameter space. We show that dynamical dark energy models (with exact equation of state $w=-1$) can be realised as a gyroscopic system.

In this work we study the impact of new physics, stimulated by flavor anomalies, on neutrino oscillations through dense dark matter halo. Inspired by a model where a Majorana dark matter fermion and two new scalar fields contribute to $b \to s \mu^+ \mu^-$ transition at the one loop level, we study the impact of neutrino-dark matter interaction on the oscillation patterns of ultra-high energy cosmic neutrinos passing through this muonphilic halo located near the center of Milky Way. We find that due to this interaction, the flavor ratios of neutrinos reaching earth would be different from that of vacuum oscillations. We also consider a $Z'$ model driven by $L_{\mu}-L_{\tau}$ symmetry and containing a vector-like fermion as a dark matter candidate. It was previously shown that for such a model, the three flavors of neutrinos decouple from each other. This will render a flavor ratio similar to that of vacuum oscillations. Therefore, the interaction of neutrinos with dense dark matter halo can serve as an important tool to discriminate between flavor models with a dark connection.

We improve the current upper bound on the axion-photon coupling derived from stellar evolution using the $R_2$ parameter, the ratio of stellar populations on the Asymptotic Giant Branch to Horizontal Branch in Globular Clusters. We compare this with data from simulations using the stellar evolution code MESA which include the effects of axion production. Particular attention is given to quantifying in detail the effects of uncertainties on the $R$ and $R_2$ parameters due to the modelling of convective core boundaries. Using a semiconvective mixing scheme we constrain the axion-photon coupling to be $g_{a\gamma\gamma} < 0.47 \times 10^{-10}~\mathrm{GeV}^{-1}$. This rules out new regions of QCD axion and axion-like particle parameter space. Complementary evidence from asteroseismology suggests that this could improve to as much as $g_{a\gamma\gamma} < 0.34 \times 10^{-10}~\mathrm{GeV}^{-1}$ as the uncertainties surrounding mixing across convective boundaries are better understood.

In a general phenomenological model with local supersymmetry, the amount of massive gravitinos produced in early universe tends to violate the known dark matter density bound by many orders of magnitude. This problem is absent in the recently proposed non-linear supergravity model in the brane world scenario in Type IIB string theory, where we (i.e., the standard model of strong and electroweak interactions) live in a stack of $\overline{\rm D3}$-branes (i.e., anti-D3-branes) that span the 3 large spatial dimensions. These $\overline{\rm D3}$-branes break supersymmetry. As an open string mode in there, the Goldstino to be eaten by the gravitino is present only inside the $\overline{\rm D3}$-branes. So, although a gravitino can be massive (e.g., $\overline{m}_{3/2} \ge 100$ GeV) inside the $\overline{\rm D3}$-branes, it is (almost) massless outside the $\overline{\rm D3}$-branes. It follows that the massive gravitinos produced inside the $\overline{\rm D3}$-branes will be pushed out of the $\overline{\rm D3}$-branes, analogous to the Meissner effect for the massive photons in super-conductors. As a result, the massive gravitinos will be depleted so the gravitino problem is absent.

When training a machine learning classifier on data where one of the classes is intrinsically rare, the classifier will often assign too few sources to the rare class. To address this, it is common to up-weight the examples of the rare class to ensure it isn't ignored. It is also a frequent practice to train on restricted data where the balance of source types is closer to equal for the same reason. Here we show that these practices can bias the model toward over-assigning sources to the rare class. We also explore how to detect when training data bias has had a statistically significant impact on the trained model's predictions, and how to reduce the bias's impact. While the magnitude of the impact of the techniques developed here will vary with the details of the application, for most cases it should be modest. They are, however, universally applicable to every time a machine learning classification model is used, making them analogous to Bessel's correction to the sample variance.

We present the new version of BlackHawk v2.0. BlackHawk is a public code designed to compute the Hawking radiation spectra of (primordial) black holes. In the version 2.0, we have added several non-standard BH metrics: charged, higher dimensional and polymerized black holes, in addition to the usual rotating (Kerr) BHs. BlackHawk also embeds some additional scripts and numerical tables that can prove useful in e.g. dark matter studies. We describe these new features and provide some examples of the capabilities of the code. A tutorial for BlackHawk is available on the TOOLS2021 website: https://indico.cern.ch/event/1076291/contributions/4609967/

In this thesis, I present three projects I carried out during m PhD. In the first project, I introduce Conformal Transformations and the Galaxy Number County. I explicitly show that the Galaxy Number Counts is invariant under Conformal Transformations, which makes it a good physical observable. In the second project, I study how weak lensing, and in particular cosmic shear, affects the shape of the galaxy images. I show that, if the light polarisation is also measured, the rotation of the main axes of the elliptical galaxy shape becomes a cosmological observable. I show how this can be used to estimate cosmic shear and its correlation functions. In the third project, I define a higher order (Riemann-squared and -cubed) Lagrangian Effective Theory of Gravity. I compute the linear correction to the speed and the quasinormal frequencies of the gravitational waves in this theory around a Schwarzschild-like background.

Using the recent model-independent determination of the charge-weak form factor difference $\Delta F_{\rm CW}$ in $^{48}$Ca and $^{208}$Pb by the CREX and PREX-2 collaborations, we perform Bayesian inference of the symmetry energy $E_{\rm sym}(\rho)$ and the neutron skin thickness $\Delta r_{\rm np}$ of $^{48}$Ca and $^{208}$Pb within the Skyrme energy density functional (EDF). We find the inferred $E_{\rm sym}(\rho)$ and $\Delta r_{\rm np}$ separately from CREX and PREX-2 are compatible with each other at $90\%$ C.L., although they exhibit strong tension at $68.3\%$ C.L. with CREX (PREX-2) favoring a very soft (stiff) $E_{\rm sym}(\rho)$ and rather small (large) $\Delta r_{\rm np}$. By combining the CREX and PREX-2 data, we obtain $E_{\rm sym}(\rho_0)=30.2_{-3.0}^{+4.1}$ MeV, the symmetry energy slope parameter $L=15.3^{+46.8}_{-41.5}$ MeV at saturation density $\rho_0$, $\Delta r_{\rm np}(^{48}{\rm Ca}) = 0.149_{-0.032}^{+0.035}$ fm and $\Delta r_{\rm np}(^{208}{\rm Pb}) = 0.139_{-0.063}^{+0.070}$ fm at $90\%$ C.L.. The $E_{\rm{sym}}(\rho)$ and $\Delta r_{\rm np}$ from combining CREX and PREX-2 are closer to the corresponding results from CREX alone, implying the PREX-2 is less effective to constrain the $E_{\rm sym}(\rho)$ and $\Delta r_{\rm np}$ due to its lower precision of $\Delta F_{\rm CW}$. Furthermore, we find the Skyrme EDF results inferred by combining the CREX and PREX-2 data at $90\%$ C.L. nicely agree with the measured dipole polarizabilities $\alpha_D$ in $^{48}$Ca and $^{208}$Pb as well as the neutron matter equation of state from microscopic calculations.

Magnetohydrodynamic turbulence is central to laboratory and astrophysical plasmas, and is invoked for interpreting many observed scalings. Verifying predicted scaling law behaviour requires extreme-resolution direct numerical simulations (DNS), with needed computing resources excluding systematic parameter surveys. We here present an analytic generator of realistically looking turbulent magnetic fields, that computes 3D ${\cal{O}}(1000^3)$ solenoidal vector fields in minutes to hours on desktops. Our model is inspired by recent developments in 3D incompressible fluid turbulence theory, where a Gaussian white noise vector subjected to a non-linear transformation results in an intermittent, multifractal random field. Our $B\times C$ model has only few parameters that have clear geometric interpretations. We directly compare a (costly) DNS with a swiftly $B\times C$-generated realization, in terms of its (i) characteristic sheet-like structures of current density, (ii) volume-filling aspects across current intensity, (iii) power-spectral behaviour, (iv) probability distribution functions of increments for magnetic field and current density, structure functions, spectra of exponents, and (v) partial variance of increments. The model even allows to mimic time-evolving magnetic and current density distributions and can be used for synthetic observations on 3D turbulent data cubes.

We investigate neutron star solutions in scalar-tensor theories of gravity with first-order derivative self-interactions in the action and in the matter coupling. We assess the robustness of the kinetic screening mechanism present in these theories against general conformal couplings to matter. The latter include ones leading to the classical Damour-Esposito-Far\`ese scalarization, as well as ones depending on the kinetic term of the scalar field. We find that kinetic screening always prevails over scalarization, and that kinetic couplings with matter enhance the suppression of scalar gradients inside the star even more, without relying on the non-linear regime. Fine tuning the kinetic coupling with the derivative self-interactions in the action allows one to partially cancel the latter, resulting in a weakening of kinetic screening inside the star. This effect represents a novel way to break screening mechanisms inside matter sources, and provides new signatures that might be testable with astrophysical observations.