Papers for Thursday, Aug 17 2023

We study the magneto-rotational instability (MRI) driven dynamo in a geometrically thin disc ($H/R\ll 1$) using stratified zero net flux (ZNF) shearing box simulations. We find that mean fields and EMFs oscillate with a primary frequency $f_{\rm dyn} = 0.017$ ($\approx 9$ orbital period), but also have higher harmonics at $3f_{\rm dyn}$. Correspondingly, the current helicity, has two frequencies $2f_{\rm dyn}$ and $4f_{\rm dyn}$ respectively, which appear to be the beat frequencies of mean fields and EMFs as expected from the magnetic helicity density evolution equation. Further, we adopt a novel inversion algorithm called the `Iterative Removal Of Sources' (IROS), to extract the turbulent dynamo coefficients in the mean-field closure using the mean magnetic fields and EMFs obtained from the shearing box simulation. We show that an $\alpha-$effect ($\alpha_{yy}$) is predominantly responsible for the creation of the poloidal field from the toroidal field, while shear generates back a toroidal field from the poloidal field; indicating that an $\alpha-\Omega$-type dynamo is operative in MRI-driven accretion discs. We also find that both strong outflow ($\bar{v}_z$) and turbulent pumping ($\gamma_z$ ) transport mean fields away from the mid-plane. Instead of turbulent diffusivity, they are the principal sink terms in the mean magnetic energy evolution equation. We find encouraging evidence that a generative helicity flux is responsible for the effective $\alpha$-effect. Finally, we point out potential limitations of horizontal ($x-y$) averaging in defining the `mean' on the extraction of dynamo coefficients and their physical interpretations.

Hydrogen sulfide (H$_2$S) is thought to be efficiently formed on grain surfaces through the successive hydrogenation of S atoms. Its non-detection so far in astronomical observations of icy dust mantles thus indicates that effective destruction pathways must play a significant role in its interstellar abundance. While chemical desorption has been shown to remove H$_2$S very efficiently from the ice, in line with H$_2$S gas-phase detections, possible solid-state chemistry triggered by the related HS radical have been largely disregarded so far -- despite it being an essential intermediate in the H$_2$S + H reaction scheme. We aim to thoroughly investigate the fate of H$_2$S upon H-atom impact under molecular cloud conditions, providing a comprehensive analysis combined with detailed quantification of both the chemical desorption and ice chemistry that ensues. Experiments are performed in an ultrahigh vacuum chamber at temperatures between 10--16 K. The changes in the solid phase during H-atom bombardment are monitored in situ by means of reflection absorption infrared spectroscopy (RAIRS), and desorbed species are measured with a quadrupole mass spectrometer (QMS). We confirm the formation of H$_2$S$_2$ via reactions involving H$_2$S + H, and quantify its formation cross section under the employed experimental conditions. Additionally, we directly assess the chemical desorption of H$_2$S by measuring the gas-phase desorption signals with the QMS, providing unambiguous desorption cross sections. Chemical desorption of H$_2$S$_2$ was not observed. The relative decrease of H$_2$S ices by chemical desorption changes from ~85% to ~74% between temperatures of 10 and 16 K, while the decrease as the result of H$_2$S$_2$ formation is enhanced from ~5% to ~26%, suggesting an increasingly relevant sulfur chemistry induced by HS radicals at warmer environments. The astronomical implications are further discussed.

Low surface brightness substructures around galaxies, known as tidal features, are a valuable tool in the detection of past or ongoing galaxy mergers, and their properties can answer questions about the progenitor galaxies involved in the interactions. The assembly of current tidal feature samples is primarily achieved using visual classification, making it difficult to construct large samples and draw accurate and statistically robust conclusions about the galaxy evolution process. With upcoming large optical imaging surveys such as the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST), predicted to observe billions of galaxies, it is imperative that we refine our methods of detecting and classifying samples of merging galaxies. This paper presents promising results from a self-supervised machine learning model, trained on data from the Ultradeep layer of the Hyper Suprime-Cam Subaru Strategic Program optical imaging survey, designed to automate the detection of tidal features. We find that self-supervised models are capable of detecting tidal features, and that our model outperforms previous automated tidal feature detection methods, including a fully supervised model. An earlier method achieved 76% completeness for 22% contamination, while our model achieves considerably higher (96%) completeness for the same level of contamination. We emphasise a number of advantages of self-supervised models over fully supervised models including maintaining excellent performance when using only 50 labelled examples for training, and the ability to perform similarity searches using a single example of a galaxy with tidal features.

XZ Tau AB is a frequently observed binary YSO in the Taurus Molecular Cloud; XZ Tau B has been classified as an EXOr object. We present new Chandra/HETG-ACIS-S observations of XZ Tau AB, complemented with variability monitoring of the system with XMM-Newton, to constrain the variability of this system and identify high-resolution line diagnostics to better understand the underlying mechanisms that produce the X-rays. We observe two flares with XMM-Newton, but find that outside of these flares the coronal X-ray spectrum of XZ Tau AB is consistent over twenty years of observations. We compare the ensemble of XZ Tau X-ray observations over time with the scatter across stars observed in point-in-time observations of the Orion Nebula Cluster and find that both overlap in terms of plasma properties, i.e., some of the scatter observed in the X-ray properties of stellar ensembles stems from intrinsic source variability.

We examine the population of simply periodic orbits in the Hill problem with radiation pressure included, in order to understand the distribution of gravitationally bound dust in orbit around a planet. We study a wide range of radiation pressure strengths, which requires the inclusion of additional terms beyond those discussed in previous analyses of this problem. In particular, our solutions reveal two distinct populations of stable wide, retrograde, orbits, as opposed to the single family that exists in the purely gravitational problem. We use the result of these calculations to study the observational shape of dust populations bound to extrasolar planets, that might be observable in scattered or reradiated light. In particular, we find that such dusty clouds should be elongated along the star--planet axis, and that the elongation of the bound population increases with $\beta$, a measure of the strength of the radiation pressure. As an application of this model, we consider the properties of the Fomalhaut system. The unusual orbital properties of the object Fomalhaut~b can be explained if the observed light was scattered by dust that was released from an object in a quasi-satellite orbit about a planet located in, or near, the observed debris ring. Within the context of the model of Hayakawa \& Hansen (2023), we find that the dust cloud around such a planet is still approximately an order of magnitude fainter than the limits set by current JWST data.

This work aims at constraining the size, shape, and geometric albedo of the dwarf planet candidate 2002 MS4 through the analysis of nine stellar occultation events. Using multichord detection, we also studied the object's topography by analyzing the obtained limb and the residuals between observed chords and the best-fitted ellipse. We predicted and organized the observational campaigns of nine stellar occultations by 2002 MS4 between 2019 and 2022, resulting in two single-chord events, four double-chord detections, and three events with three to up to sixty-one positive chords. Using 13 selected chords from the 8 August 2020 event, we determined the global elliptical limb of 2002 MS4. The best-fitted ellipse, combined with the object's rotational information from the literature, constrains the object's size, shape, and albedo. Additionally, we developed a new method to characterize topography features on the object's limb. The global limb has a semi-major axis of 412 $\pm$ 10 km, a semi-minor axis of 385 $\pm$ 17 km, and the position angle of the minor axis is 121 $^\circ$ $\pm$ 16$^\circ$. From this instantaneous limb, we obtained 2002 MS4's geometric albedo and the projected area-equivalent diameter. Significant deviations from the fitted ellipse in the northernmost limb are detected from multiple sites highlighting three distinct topographic features: one 11 km depth depression followed by a 25$^{+4}_{-5}$ km height elevation next to a crater-like depression with an extension of 322 $\pm$ 39 km and 45.1 $\pm$ 1.5 km deep. Our results present an object that is $\approx$138 km smaller in diameter than derived from thermal data, possibly indicating the presence of a so-far unknown satellite. However, within the error bars, the geometric albedo in the V-band agrees with the results published in the literature, even with the radiometric-derived albedo.

We use the conjugate angle of radial action ($\theta_R$), the best representation of the orbital phase, to explore the "mid-plane, north branch, south branch" and "Monoceros area" disk structures that were previously revealed in the LAMOST K giants (Xu et al. 2020). The former three substructures, identified by their 3D kinematical distributions, have been shown to be projections of the phase space spiral (resulting from nonequilibrium phase mixing). In this work, we find that all of these substructures associated with the phase spiral show high aggregation in conjugate angle phase space, indicating that the clumping in conjugate angle space is a feature of ongoing, incomplete phase mixing. We do not find the $Z-V_Z$ phase spiral located in the "Monoceros area", but we do find a very highly concentrated substructure in the quadrant of conjugate angle space with the orbital phase from the apocenter to the guiding radius. The existence of the clump in conjugate angle space provides a complementary way to connect the "Monoceros area" with the direct response to a perturbation from a significant gravitationally interactive event. Using test particle simulations, we show that these features are analogous to disturbances caused by the impact of the last passage of the Sagittarius dwarf spheroidal galaxy.

The diffusion coefficients around the pulsar $\gamma$-ray halos are highly suppressed compared with the value in the interstellar medium. It is suggested in the literature that the $\gamma$-ray halos can be explained by a ballistic-diffusive (BD) propagation without slow diffusion. However our calculation shows that the BD propagation can not account for the $\gamma$-ray halo profile well. Furthermore the transfer efficiency of the pulsar spin down energy to the high energy electrons and positrons is even larger than 1 in the BD scenario. Therefore slow diffusion is necessary to account for the pulsar $\gamma$-ray halos. Taking the slow diffusion into account the contribution of positron flux originated from nearby pulsars to the AMS-02 data is reexamined. We may also expect a slow diffusion disk of the Milky Way as many such slow diffusion regions exist. The positron contribution to the AMS-02 data from dark matter annihilation in the new propagation model is also reexamined. We find that the dark matter scenario satisfies all the $\gamma$-ray limits in the new propagation model.

Using the linear polarimetric observations, we present a method to derive the membership probability of stars in cluster NGC 2345. The polarimetric observations of cluster NGC 2345 are performed using the instrument ARIES IMaging POLarimeter (AIMPOL) mounted as a backend of the 104-cm telescope of ARIES. Members of the cluster should exhibit comparable polarization since they are located nearly at the same distance. This concept is used to extract the membership probability of known member stars of cluster NGC 2345. The membership probability estimated using the polarimetric data for cluster NGC 2345 agrees with the membership probability derived from the proper motion method in the previous studies.

The Ice Cube Neutrino Observatory has been measuring an isotropic astrophysical neutrino flux in multiple detection channels for almost a decade. Galactic diffuse emission, which arises from the interactions between cosmic rays and the interstellar medium, is an expected signal in IceCube. The superposition of an extragalactic flux and a galactic flux results in directional structure and variations in the spectrum. In this work, we use 12.3 years of high-purity muon-neutrino induced muon track data to perform a dedicated search for this galactic emission, combined with a spectral measurement of the isotropic astrophysical neutrino flux. To distinguish a galactic component from the dominant atmospheric and isotropic astrophysical components, the precise directional information available for muon tracks is fully utilized in a three-dimensional forward folding likelihood fit. We test a state-of-the-art model prediction of galactic diffuse emission based on recent cosmic ray data (CRINGE). We fit this prediction as a template scaled by a factor $\Psi_{\mathrm{CRINGE}}$, and find $2.9\pm 1.1 \times \Psi_{\mathrm{CRINGE}}$ with a significance of $2.7\sigma$ in an energy range between 400 GeV and 60 TeV in the Northern Sky.

This work is the seventh study in a series dedicated to investigating degeneracies of simultaneous age, mass, extinction, and metallicity determinations of partially resolved or unresolved star clusters with Hubble Space Telescope broadband aperture photometry. In the sixth work (hereafter, Paper I), it was demonstrated that the adaptive aperture photometry, performed to avoid the majority of the projected foreground and background stars falling within the apertures, gives more consistent colour indices for star clusters. In this study, we aim to supplement the homogeneous multi-colour aperture photometry results published in Paper~I and provide a complete M31 Panchromatic Hubble Andromeda Treasury (PHAT) survey star cluster photometry catalogue for further analysis. Following Paper I, we used a two-aperture approach for photometry. The first aperture is the standard one used to measure total cluster fluxes. The second (smaller) aperture is introduced to avoid the bright foreground and background stars projecting onto the clusters. We selected the radii of smaller apertures to be larger than the half-light radii of the clusters. We present the second part of the star cluster aperture photometry catalogues for a sample of 1477 star clusters from the M31 PHAT survey not covered in Paper I. Compared to the M31 PHAT star cluster aperture photometry catalogue published by Johnson et al., adjustments were made to the cluster centre coordinates, aperture sizes, and sky background levels.

We present fundamental scaling relationships between properties of the optical/UV light curves of tidal disruption events (TDEs) and the mass of the black hole that disrupted the star. We have uncovered these relations from the late-time emission of TDEs. Using a sample of 63 optically-selected TDEs, the latest catalog to date, we observed flattening of the early-time emission into a near-constant late-time plateau for at least two-thirds of our sources. Compared to other properties of the TDE lightcurves (e.g., peak luminosity or decay rate) the plateau luminosity shows the tightest correlation with the total mass of host galaxy ($p$-value of $2 \times 10^{-6}$, with a residual scatter of 0.3 dex). Physically this plateau stems from the presence of an accretion flow. We demonstrate theoretically and numerically that the amplitude of this plateau emission is strongly correlated with black hole mass. By simulating a large population of TDEs, we determine a plateau luminosity-black hole mass scaling relationship well described by $ \log_{10} \left(M_{\bullet}/M_{\odot} \right) = 1.50 \log_{10} \left( L_{\rm plat}/10^{43} {\rm erg \, s^{-1}} \right) + 9.0 $. The observed plateau luminosities of TDEs and black hole masses in our large sample are in excellent agreement with this simulation. Using the black hole mass predicted from the observed TDE plateau luminosity, we reproduce the well-known scaling relations between black hole mass and galaxy velocity dispersion. The large black hole masses of 10 of the TDEs in our sample allow us to provide constraints on their black hole spins, favouring rapidly rotating black holes. We add 49 (34) black hole masses to the galaxy mass (velocity dispersion) scaling relationships, updating and extending these correlations into the low black hole mass regime.

In recent years, arrays of radio antennas operating in the MHz regime have shown great potential as detectors in astroparticle physics. In particular, they fulfill an important role in the indirect detection of ultra-high energy cosmic rays. For a proper determination of the energy scale of the primary particles, accurate absolute calibration of radio detectors is crucial. Galactic calibration - i.e., using the Galaxy-dominated radio sky as a reference source - will potentially be the standard method for this task. However, uncertainties in the strength of the Galactic radio emission lead to uncertainties in the absolute calibration of the radio detectors and, thus, in the energy scale of the cosmic-ray measurements. To quantify these uncertainties, we present a study comparing seven sky models in the radio-frequency range of 30 to 408 MHz. By conversion to the locally visible sky, we estimate the uncertainties for the cases of the radio antenna arrays of GRAND, IceCube, LOFAR, OVRO-LWA, the Pierre Auger Observatory, RNO-G and SKA-low. Finally, we discuss the applicability of the Galactic calibration, for example, regarding the influence of the quiet Sun.

Twisted magnetic flux ropes are reservoirs of free magnetic energy. In a highly-conducting plasma such as the solar corona, energy release through multiple magnetic reconnections can be modelled as a helicity-conserving relaxation to a minimum energy state. One possible trigger for this relaxation is the ideal kink instability in a twisted flux rope. We show that this provides a good description for confined solar flares, and develop from idealised cylindrical models to realistic models of coronal loops. Using 3D magnetohydrodynamic simulations combined with test-particle simulations of non-thermal electrons and ions, we predict multiple observational signatures of such flares. We then show how interactions and mergers of flux ropes can release free magnetic energy, using relaxation theory to complement simulations of merging-compression formation in spherical tokamaks and heating avalanches in the solar corona.

The helium flash, occurring in stars of 0.6-2.0 M$_\odot$ at the end of the red giant branch, is not observable via optical means due to the energy of the process being used to lift the core out of degeneracy. Neutrinos, which are linked to the ignition of reactions triggered during the flash and serve as the only cooling process in the inert core, can help characterize changes in internal structure. In this work, we create 18 stellar models across three mass and six metallicity values, chosen in the context of the stellar abundance problem, to compare the evolutionary path up to and probe the helium flash by conducting a detailed study of neutrino emission throughout this crucial phase of stellar evolution. We demonstrate how thermal neutrino emissions could have an imprint on global asteroseismic parameters and use them as an additional tool to infer the impact of compositional changes. We find that a precision of 0.3 $\mu$Hz in the determination of $\Delta \nu$ is enough to distinguish between between the two most prominent solar composition models and confirm that asteroseismic observation can be enough to classify a star as undergoing the process of helium subflashes. We also predict nuclear neutrino emission fluxes and their evolution for all relevant sources.

Neutral hydrogen (\ion{H}{i}) $21$-cm intensity mapping (IM) is a promising probe of the large-scale structures in the Universe. However, a few orders of magnitude brighter foregrounds obscure the IM signal. Here we use the Tapered Gridded Estimator (TGE) to estimate the multi-frequency angular power spectrum (MAPS) $C_{\ell}(\Delta\nu)$ from a $24.4\,\rm{MHz}$ bandwidth uGMRT Band $3$ data at $432.8\,\rm{MHz}$. In $C_{\ell}(\Delta\nu)$ foregrounds remain correlated across the entire $\Delta\nu$ range, whereas the $21$-cm signal is localized within $\Delta\nu\le[\Delta \nu]$ (typically $0.5-1\,\rm{MHz}$). Assuming the range $\Delta\nu>[\Delta \nu]$ to have minimal $21$-cm signal, we use $C_{\ell}(\Delta\nu)$ in this range to model the foregrounds. This foreground model is extrapolated to $\Delta\nu\leq[\Delta \nu]$, and subtracted from the measured $C_{\ell}(\Delta\nu)$. The residual $[C_{\ell}(\Delta\nu)]_{\rm res}$ in the range $\Delta\nu\le[\Delta\nu]$ is used to constrain the $21$-cm signal, compensating for the signal loss from foreground subtraction. $[C_{\ell}(\Delta\nu)]_{\rm{res}}$ is found to be noise-dominated without any trace of foregrounds. Using $[C_{\ell}(\Delta\nu)]_{\rm res}$ we constrain the $21$-cm brightness temperature fluctuations $\Delta^2(k)$, and obtain the $2\sigma$ upper limit $\Delta_{\rm UL}^2(k)\leq(18.07)^2\,\rm{mK^2}$ at $k=0.247\,\rm{Mpc}^{-1}$. We further obtain the $2\sigma$ upper limit $ [\Omega_{\ion{H}{i}}b_{\ion{H}{i}}]_{\rm UL}\leq0.022$ where $\Omega_{\ion{H}{i}}$ and $b_{\ion{H}{i}}$ are the comoving \ion{H}{i} density and bias parameters respectively. Although the upper limit is nearly $10$ times larger than the expected $21$-cm signal, it is $3$ times tighter over previous works using foreground avoidance on the same data.

Context. Clouds seem unavoidable in cool and dense environments, and hence, are necessary to explain observations of exoplanet atmospheres, most recently of WASP 96b with JWST. Understanding the formation of cloud condensation nuclei in non-terrestrial environments is therefore crucial to develop accurate models to interpret present and future observations. Aims. The goal of the paper is to support observations with infrared spectra for (TiO2)N clusters in order to study cloud formation in exoplanet atmospheres. Methods. Vibrational frequencies are derived from quantum-chemical calculations for 123 (TiO2)-clusters and their isomers, and line-broadening mechanisms are evaluated. Cluster spectra are calculated for several atmospheric levels for two example exoplanet atmospheres (WASP 121b-like and WASP 96b-like) to identify possible spectral fingerprints for cloud formation. Results. Rotational motion of and transitions in the clusters cause significant line broadening, so that individual vibrational lines are broadened beyond the spectral resolution of the medium resolution mode of the JWST mid-infrared instrument MIRI at R = 3000. However, each individual cluster isomer exhibits a "fingerprint" IR spectrum. In particular, larger (TiO2)-clusters have distinctly different spectra from smaller clusters. Morning and evening terminator for the same planet can exhibit different total absorbances due to different cluster sizes being more abundant. Conclusions. The largest (TiO2)-clusters are not necessarily the most abundant (TiO2)-clusters in the high-altitude regions of ultra-hot Jupiters, and the different cluster isomers will contribute to the local absorbance. Planets with a considerable day-night asymmetry will be most suitable to search for (TiO2)-cluster isomers in order to improve cloud formation modelling.

The disc instability mechanism (DIM) is widely accepted to account for the transient behaviour of dwarf novae (DNe), which experience short outbursts separated by long quiescence. The duty cycle (the ratio between the outburst duration and the recurrence time) determines the amount of accreted mass by the white dwarf (WDs) during outbursts, thus playing an important role in the long-term binary evolution. Employing the code of Modules for Experiments in Stellar Astrophysics, we systemically investigate the influence of the duty cycles on the evolution of DNe and the mass growth of accreting carbon-oxygen (CO) WDs. Our calculations show that, while the DIM can considerably influence the accretion process, efficient WD-mass growth requires a particular range of the duty cycle. For WDs with the initial masses of 0.6, 0.7 and 1.1 $M_\odot$, these duty cycles are 0.006$\,\leq$$d$$\,\leq$0.007, $d$\,=\,0.005 and $d$\,=\,0.003, and the accumulated mass of the WDs can reach 0.1, 0.13 and 0.21 $M_\odot$, respectively. In all of our simulations, no CO WDs can grow their masses to the explosion mass of Type Ia supernovae of about $1.38~M_\odot$. Because of a much short timescale of the outburst state, the final donor-star masses and orbital periods are insensitive to the duty cycles. Therefore, we propose that the DIM in DNe could alleviate the WD mass problem to some extent.

Fallback in core-collapse supernova explosions is potentially of significant importance for the birth spins of neutron stars and black holes. It has recently been pointed out that the angular momentum imparted onto a compact remnant by fallback material is subtly intertwined with its kick because fallback onto a moving neutron star or black hole will preferentially come for a conical region around its direction of travel. We show that contrary to earlier expectations such one-sided fallback accretion onto a neutron star will tend to produce spin-kick misalignment. Since the baroclinic driving term in the vorticity equation is perpendicular to the nearly radial pressure gradient, convective eddies in the progenitor as well as Rayleigh-Taylor plumes growing during the explosion primarily carry angular momentum perpendicular to the radial direction. Fallback material from the accretion volume of a moving neutron star therefore carries substantial angular momentum perpendicular to the kick velocity. We estimate the seed angular momentum fluctuations from convective motions in core-collapse supernova progenitors and argue that accreted fallback material will almost invariably be accreted with the maximum permissible specific angular momentum for reaching the Alfv\'en radius. This imposes a limit of $\mathord{\sim}10^{-2}M_\odot$ of fallback accretion for fast-spinning young neutron stars with periods of $\mathord{\sim}20\,\mathrm{ms}$ and less for longer birth spin periods.

Radio-frequency, indirect dark matter searches have recently been gaining prevalence, due to the high sensitivity and resolution capabilities of the new generation of radio interferometers. MeerKAT is currently one of the most sensitive instruments of its kind, making it ideal for indirect dark matter searches. By making use of publicly available data from the MeerKAT Galaxy Cluster Legacy Survey we are able to use both the observed diffuse synchrotron emission and non-detections to constrain the WIMP dark matter parameter space. In addition to a subset of generic WIMP annihilation channels, we probe the dark matter candidate within the 2HDM+S particle physics model, which was developed as an explanation for anomalies observed in the Large Hadron Collider data from runs 1 and 2. By undertaking a statistical analysis of the radio flux densities within galaxy clusters we are able to exclude the thermal relic value for WIMP masses $< \, \sim 800 $ GeV for annihilation into bottom quarks. This is competitive with the best constraints in the current literature.

We analyze pre-explosion ultraviolet (UV) imaging of the nearby Type II supernova SN 2023ixf in search of precursor variability. No outbursts are seen in observations obtained 15-20 yr prior to explosion to a limit of $L_{NUV} \approx 1000~L_{sun}$ and $L_{NUV} \approx 2000~L_{sun}$. The time period of these non-detections roughly corresponds to changes in the circumstellar density inferred from early spectra and photometry.

In the last few years, the NICER collaboration has provided mass and radius inferences, via pulse profile modeling, for two pulsars: PSR J0030+0451 and PSR J0740+6620. Given the importance of these results for constraining the equation of state of dense nuclear matter, it is crucial to validate them and test their robustness. We therefore explore the reliability of these results and their sensitivity to analysis settings and random processes, including noise, focusing on the specific case of PSR J0030+0451. We use X-PSI, one of the two main analysis pipelines currently employed by the NICER collaboration for mass and radius inferences. With synthetic data that mimic the PSR J0030+0451 NICER data set, we evaluate the recovery performances of X-PSI under conditions never tested before, including complex modeling of the thermally emitting neutron star surface. For the test cases explored, our results suggest that X-PSI is capable of recovering the true mass and radius within reasonable credible intervals. This work also reveals the main vulnerabilities of the analysis: a significant dependence on noise and the presence of multi-modal structure in the posterior surface. Noise particularly impacts our sensitivity to the analysis settings and widths of the posterior distributions. The multi-modal structure in the posterior suggests that biases could be present if the analysis is unable to exhaustively explore the parameter space. Convergence testing, to ensure an adequate coverage of the parameter space and a suitable representation of the posterior distribution, is one possible solution to these challenges.

Galaxy rotation curve (RC) fitting is an important technique which allows the placement of constraints on different kinds of dark matter (DM) halo models. In the case of non-phenomenological DM profiles with no analytic expressions, the art of finding RC best-fits including the full baryonic $+$ DM free parameters can be difficult and time-consuming. In the present work, we use a gradient descent method used in the backpropagation process of training a neural network, to fit the so-called Grand Rotation Curve of the Milky Way (MW) ranging from $\sim$1 pc all the way to $\sim$$10^5$ pc. We model the mass distribution of our Galaxy including a bulge (inner $+$ main), a disk, and a fermionic dark matter (DM) halo known as the Ruffini-Arg\"uelles-Rueda (RAR) model. This is a semi-analytical model built from first-principle physics such as (quantum) statistical mechanics and thermodynamics, whose more general density profile has a dense core -- diluted halo morphology with no analytic expression. As shown recently and further verified here, the dark and compact fermion-core can work as an alternative to the central black hole in SgrA* when including data at milliparsec scales from the S-cluster stars. Thus, we show the ability of this state-of-the-art machine learning tool in providing the best-fit parameters to the overall MW RC in the $10^{-2}$--$10^5$ pc range, in a few hours of CPU time.

The large-scale magnetic fields of several pre-main sequence (PMS) stars have been observed to be simple and axisymmetric, dominated by tilted dipole and octupole components. The magnetic fields of other PMS stars are highly multipolar and dominantly non-axisymmetric. Observations suggest that the magnetic field complexity increases as PMS stars evolve from Hayashi to Henyey tracks in the Hertzsprung--Russell diagram. Independent observations have revealed that X-ray luminosity decreases with age during PMS evolution, with Henyey track PMS stars having lower fractional X-ray luminosities ($L_\textrm{X}/L_*$) compared to Hayashi track stars. We investigate how changes in the large-scale magnetic field topology of PMS stars influences coronal X-ray emission. We construct coronal models assuming pure axisymmetric multipole magnetic fields, and magnetic fields consisting of a dipole plus an octupole component only. We determine the closed coronal emitting volume, over which X-ray emitting plasma is confined, using a pressure balance argument. From the coronal volumes we determine X-ray luminosities. We find that $L_\textrm{X}$ decreases as the degree $\ell$ of the multipole field increases. For dipole plus octupole magnetic fields we find that $L_\textrm{X}$ tends to decrease as the octupole component becomes more dominant. By fixing the stellar parameters at values appropriate for a solar mass PMS star, varying the magnetic field topology results in two orders of magnitude variation in $L_\textrm{X}$. Our results support the idea that the decrease in $L_\textrm{X}$ as PMS stars age can be driven by an increase in the complexity of the large-scale magnetic field.

We study the simultaneous decay of global string loops into scalar particles (massless and massive modes) and gravitational waves (GWs). Using field theory simulations in flat space-time of %isolated loops with initial length $\sim 80-1700$ times their core width, we determine the power emitted by a loop into scalar particles, $P_{\varphi}$, and GWs, $P_{\rm GW}$, and characterize the loop-decay timescale as a function of its initial length, energy and angular momentum. We quantify infrared and ultraviolet lattice dependencies of our results. For all type of loops and initial conditions considered, GW emission is always suppressed compared to particles as $P_{\rm GW}/P_{\varphi} \approx \mathcal{O}(10)(v/m_\text{p})^2\ll 1$, where $v$ is the vacuum expectation value associated with string formation. Our results suggest that the GW background from a global string network, such as in dark matter axion scenarios, will be highly suppressed.

Essential insights on the characterization and quality of a detectable biosphere are gained by analyzing the effects of its environmental parameters. We compiled environmental and biological properties of the Phanerozoic Eon from various published data sets and conducted a correlation analysis to assess variations in parameters relevant to the habitability of Earth's biosphere. We showed that environmental parameters such as oxygen, global average surface temperatures, runoff rates and carbon dioxide are interrelated and play a key role in the changes of biomass and biodiversity. We showed that there were several periods with a highly thriving biosphere, with one even surpassing present day biodiversity and biomass. Those periods were characterized by increased oxygen levels and global runoff rates, as well as moderate global average surface temperatures, as long as no large or rapid positive and/or negative temperature excursions occurred. High oxygen contents are diagnostic of biomass production by continental plant life. We find that exceptionally high oxygen levels can at least in one instance compensate for decreased relative humidities, providing an even more habitable environment compared to today. Beyond Earth, these results will help us to understand how environmental parameters affect biospheres on extrasolar planets and guide us in our search for extraterrestrial life.

Direct-imaging observations of terrestrial exoplanets will enable their atmospheric characterization and habitability assessment. Considering the Earth, the key atmospheric signatures for the biosphere is O$_2$ and the photochemical product O$_3$. However, this O$_2$-O$_3$ biosignature is not detectable in the visible wavelengths for most of the time after the emergence of oxygenic photosynthesis life (i.e., the Proterozoic Earth). Here we demonstrate spectroscopic observations in the ultraviolet wavelengths for detecting and characterizing O$_2$ and O$_3$ in Proterozoic Earth-like planets, using ExoReL$^\Re$. For an O$_2$ mixing ratio 2 to 3 orders of magnitude less than the present-day Earth, and an O$_3$ mixing ratio of $10^{-7}-10^{-6}$, we find that O$_3$ can be detected and its mixing ratio can be measured precisely (within $~1$ order of magnitude) in the ultraviolet ($0.25-0.4\ \mu$m) in addition to visible-wavelength spectroscopy. With modest spectral resolution ($R=7$) and S/N ($\sim10$) in the ultraviolet, the O$_3$ detection is robust against other potential gases absorbing in the ultraviolet (e.g., H$_2$S and SO$_2$), as well as the short-wavelength cutoff between 0.2 and 0.25 $\mu$m. While the O$_3$ detection does not rely on the near-infrared spectra, extending the wavelength coverage to the near-infrared ($1-1.8\ \mu$m) would provide essential information to interpret the O$_3$ biosignature, including the mixing ratio of H$_2$O, the cloud pressure, as well as the determination of the dominant gas of the atmosphere. The ultraviolet and near-infrared capabilities should thus be evaluated as critical components for future missions aiming at imaging and characterizing terrestrial exoplanets, such as the Habitable Worlds Observatory.

Galactic archaeology represents a multidisciplinary approach aimed at unraveling the intricate history of the Milky Way galaxy through the study of its stellar populations. This abstract delves into the significance of galactic archaeology as a vital tool for understanding the formation and evolution of the Milky Way. By examining the distribution, kinematics, chemical compositions, and ages of stars within the galaxy, researchers gain insights into the dynamic processes that have shaped its structure over billions of years. Stellar populations serve as invaluable relics of past epochs, preserving clues about the conditions prevalent during their formation. The utilization of spectroscopic and photometric data has enabled the classification and analysis of stars, allowing astronomers to discern distinct populations and unveil their origin stories. Through these studies, the emergence of the Milky Way's various components, such as the thin and thick disk, halo, and bulge, becomes discernible.

The IceCube Upgrade will augment the existing IceCube Neutrino Observatory by deploying 700 additional optical sensor modules and calibration devices within its center at a depth of 1.5 to 2.5 km in the Antarctic ice. One goal of the Upgrade is to improve the positioning calibration of the optical sensors to increase the angular resolution for neutrino directional reconstruction. An acoustic calibration system will be deployed to explore the capability of achieving this using trilateration of propagation times of acoustic signals. Ten Acoustic Modules (AM) capable of sending and receiving acoustic signals with frequencies from 5 to 30 kHz will be installed within the detector volume. Additionally, compact acoustic sensors inside 15 optical sensor modules will complement the acoustic calibration system. With this system, we aim for an accuracy of a few tens of cm to localize the Acoustic Modules and sensors. Due to the longer attenuation length of sound compared to light within the ice, acoustic position calibration is especially interesting for the upcoming IceCube-Gen2 detector, which will have a string spacing of around 240 m. In this contribution we present an overview of the technical design of the Acoustic Module as well as results of performance tests with a first complete prototype.

We analyse a sample of 21 `bare' Seyfert~1 Active Galactic Nuclei (AGNs), a sub-class of Seyfert~1s, with intrinsic absorption $\mathrm{N_{H}} \sim 10^{20}~ \mathrm{cm}^{-2}$, in the local universe (z $<$ 0.2) using {\it XMM-Newton} and {\it Swift}/XRT observations. The luminosities of the primary continuum, the X-ray emission in the 3 to 10 keV energy range and the soft-excess, the excess emission that appears above the low-energy extrapolation of the power-law fit of 3 to 10 keV X-ray spectra, are calculated. Our spectral analysis reveals that the long-term intrinsic luminosities of the soft-excess and the primary continuum are tightly correlated $(L_{PC}\propto L_{SE}^{1.1\pm0.04})$. We also found that the luminosities are correlated for each source. This result suggests that both the primary continuum and soft excess emissions exhibit a dependency on the accretion rate in a similar way.

The most conservative interpretation of the nHz stochastic gravitational wave background (SGWB) discovered by NANOGrav and other Pulsar Timing Array (PTA) Collaborations is astrophysical, namely that it originates from supermassive black hole (SMBH) binaries. However, alternative cosmological models have been proposed, including cosmic strings, phase transitions, domain walls, primordial fluctuations and "audible" axions. We perform a multi-model analysis (MMA) to compare how well these different hypotheses fit the NANOGrav data, both in isolation and in combination with SMBH binaries, and address the questions: Which interpretations fit the data best, and which are disfavoured? We also discuss experimental signatures that can help discriminate between different sources of the PTA GW signal, including fluctuations in the signal strength between frequency bins, individual sources and how the PTA signal extends to higher frequencies.

We calculate the effects of a light, very weakly-coupled boson $X$ arising from a spontaneously broken $U(1)_{B-L}$ symmetry on $\Delta N_{\rm eff}$ as measured by the CMB and $Y_p$ from BBN. Our focus is the mass range $1 \; {\rm eV} \lesssim m_X \lesssim 100 \; {\rm MeV}$; masses lighter than about an ${\rm eV}$ have strong constraints from fifth-force law constraints, while masses heavier than about $100$~MeV are constrained by other probes. We do not assume $X$ began in thermal equilibrium with the SM; instead, we allow $X$ to freeze-in from its very weak interactions with the SM. We find $U(1)_{B-L}$ is more strongly constrained by $\Delta N_{\rm eff}$ than previously considered. The bounds arise from the energy density in electrons and neutrinos slowly siphoned off into $X$ bosons, which become nonrelativistic, redshift as matter, and then decay, dumping their slightly larger energy density back into the SM bath causing $\Delta N_{\rm eff} > 0$. While some of the parameter space has complementary constraints from stellar cooling, supernova emission, and terrestrial experiments, we find future CMB observatories can access regions of mass and coupling space not probed by any other method. In gauging $U(1)_{B-L}$, we assume the $[U(1)_{B-L}]^3$ anomaly is canceled by right-handed neutrinos, and so our $\Delta N_{\rm eff}$ calculations have been carried out in two scenarios: neutrinos have Dirac masses, or, right-handed neutrinos acquire Majorana masses. In the latter scenario, we comment on the additional implications of thermalized right-handed neutrinos decaying during BBN. We also briefly consider the possibility that $X$ decays into dark sector states. If these states behave as radiation, we find weaker constraints, whereas if they are massive, there are stronger constraints, though now from $\Delta N_{\rm eff} < 0$.

In this article, we study the neutron stars with antikaon condensates and their radial oscillations. We incorporate the antikaons $(K^-,\bar{K}^0)$ within a relativistic mean field theory with density dependent couplings. A transition to the kaon condensed phase is treated as a second order phase transition for different possible antikaon optical potentials. Then, we solve the structure equations of stars and calculate the fundamental and higher order frequencies of their radial pulsations. We study the eigenfunctions of different radial modes for a $2M_\odot$ star with equations of state having different potential depths of antikaons. We also study the large frequency separations for the $2M_\odot$ star. We find distinct features of the appearances of antikaons on the eigenfunctions. The shape of the eigenfunctions corresponding to the radial perturbations is affected due to the appearance of the antikaons, but for the pressure perturbation, the shape remains unchanged.

The IceCube Neutrino Observatory is a cubic kilometer neutrino telescope located at the geographic South Pole. Understanding detector systematic effects is a continuous process. This requires the Monte Carlo simulation to be updated periodically to quantify potential changes and improvements in science results with more detailed modeling of the systematic effects. IceCube's largest systematic effect comes from the optical properties of the ice the detector is embedded in. Over the last few years there have been considerable improvements in the understanding of the ice, which require a significant processing campaign to update the simulation. IceCube normally stores the results in a central storage system at the University of Wisconsin-Madison, but it ran out of disk space in 2022. The Prototype National Research Platform (PNRP) project thus offered to provide both GPU compute and storage capacity to IceCube in support of this activity. The storage access was provided via XRootD-based OSDF Origins, a first for IceCube computing. We report on the overall experience using PNRP resources, with both successes and pain points.

Nuclear mass measurements and neutron matter theory tightly constrain the nuclear symmetry energy parameters $J$, $L$, $K_{sym}$ and $Q_{sym}$. Corroboration of these constraints on $J$ and $L$ can be found from measurements of the neutron skin thicknesses and dipole polarizabilities of neutron-rich nuclei. The experimental constraints on these parameters are compared with those obtained from consideration of astrophysical measurements of the neutron star radius, which we show is highly correlated with $L$. Attention is aimed at the recent PREX and CREX neutron skin measurements from Jefferson Lab, NICER neutron star radius measurements, and a new interpretation of the GW170817 tidal deformability measurement. We find joint satisfaction of PREX and CREX gives $J=32.2\pm1.7$ MeV and $L=52.9\pm13.2$ MeV, in excellent agreement with neutron matter predictions of $J=32.0\pm1.1$ MeV and $L=51.9\pm7.9$ MeV.

Modeling self-gravitating gas flows is essential to answering many fundamental questions in astrophysics. This spans many topics including planet-forming disks, star-forming clouds, galaxy formation, and the development of large-scale structures in the Universe. However, the nonlinear interaction between gravity and fluid dynamics offers a formidable challenge to solving the resulting time-dependent partial differential equations (PDEs) in three dimensions (3D). By leveraging the universal approximation capabilities of a neural network within a mesh-free framework, physics informed neural networks (PINNs) offer a new way of addressing this challenge. We introduce the gravity-informed neural network (GRINN), a PINN-based code, to simulate 3D self-gravitating hydrodynamic systems. Here, we specifically study gravitational instability and wave propagation in an isothermal gas. Our results match a linear analytic solution to within 1\% in the linear regime and a conventional grid code solution to within 5\% as the disturbance grows into the nonlinear regime. We find that the computation time of the GRINN does not scale with the number of dimensions. This is in contrast to the scaling of the grid-based code for the hydrodynamic and self-gravity calculations as the number of dimensions is increased. Our results show that the GRINN computation time is longer than the grid code in one- and two- dimensional calculations but is an order of magnitude lesser than the grid code in 3D with similar accuracy. Physics-informed neural networks like GRINN thus show promise for advancing our ability to model 3D astrophysical flows.

We propose a scenario, motivated by but not exclusive to trace dynamics, in which emergent quantum theory takes the form of two sectors coupled gravitationally (or very weakly at some high unification scale), one sector with complex unit $i$ and the other sector with complex unit $-i$. I postulate that as a result of symmetries of the pre-quantum theory, in the absence of coupling the two sectors both have Higgs potentials that lie precisely at the boundary between phases with nonzero and zero Higgs vaccum expectation. Turning on the coupling between the two sectors can break the degeneracy, pushing the Higgs potential in one sector into the domain of nonzero Higgs expectation (giving the visible sector), and pushing the Higgs potential in the other sector into the domain of zero Higgs expectation (giving the dark sector). The least massive baryon in the dark sector will then be a candidate self-interacting dark matter particle.

We systematically derive the chiral kinetic theory for chiral fermions with collisions, including the self-energy corrections, from quantum field theories. We find that the Wigner functions and chiral kinetic equations receive both the classical and quantum corrections from the self-energies and their spacetime gradients. We also apply this formalism to study non-equilibrium neutrino transport due to the interaction with thermalized electrons, as realized in core-collapse supernovae. We derive neutrino currents along magnetic fields and neutrino spin Hall effect induced by temperature and chemical potential gradients of electrons at first order in the Fermi constant $G_{\rm F}$ for anisotropic neutrino distributions.

Within the framework of the local limit of nonlocal gravity (NLG), we investigate a class of Bianchi type I spatially homogeneous but anisotropic cosmological models. The modified field equations are presented in this case and some special solutions are discussed in detail. This modified gravity theory contains a susceptibility function S(x) such that general relativity (GR) is recovered for S = 0. In the modified anisotropic cosmological models, we explore the contribution of S(t) and its temporal derivative to the local anisotropic cosmic acceleration. The implications of our results for observational cosmology are briefly discussed.

We consider the long-term evolution of an inhomogeneous long-range interacting $N$-body system. Placing ourselves in the dynamically hot limit, i.e. neglecting collective effects, we derive a large deviation principle for the system's empirical angle-averaged distribution function. This result extends the classical ensemble-averaged kinetic theory given by the so-called inhomogeneous Landau equation, as it specifies the probability of typical and large dynamical fluctuations. We detail the main properties of the associated large deviation Hamiltonian, in particular how it complies with the system's conservation laws and possesses a gradient structure.

Dual-phase liquid-xenon time projection chambers (LXe TPCs) deploying a few tonnes of liquid are presently leading the search for WIMP dark matter. Scaling these detectors to 10-fold larger fiducial masses, while improving their sensitivity to low-mass WIMPs presents difficult challenges in detector design. Several groups are considering a departure from current schemes, towards either single-phase liquid-only TPCs, or dual-phase detectors where the electroluminescence region consists of patterned electrodes. Here, we discuss the possible use of Thick Gaseous Electron Multipliers (THGEMs) coated with a VUV photocathode and immersed in LXe as a building block in such designs. We focus on the transfer efficiencies of ionization electrons and photoelectrons emitted from the photocathode through the electrode holes, and show experimentally that efficiencies approaching 100 % can be achieved with realistic voltage settings. The observed voltage dependence of the transfer efficiencies is consistent with electron transport simulations once diffusion and charging-up effects are included.

Asymmetric emission of gravitational waves during a compact binary coalescence results in the loss of linear momentum and a corresponding `kick' or recoil on the binary's center of mass. This leads to a direction-dependent Doppler shift of the ringdown gravitational waveform. We quantify the measurability of the kick imparted to the remnant black hole in a binary black hole merger. Future ground- and space-based gravitational wave detectors will measure this effect to within $\sim 2\%$ to $\sim 30\%$ for a subset of their expected observed sources. Certain binary configurations in the LISA band may allow a sub-percent-level measurement of this effect. This direct measurement of black hole kicks can also facilitate a novel test of general relativity based on linear momentum balance. We formulate this kick consistency test via measurement of a null variable that quantifies the difference between the inferred kick (using numerical relativity) and that observed via the Doppler-shifted ringdown signal. This null variable can be constrained (at 90% confidence) to $\sim 10\%$ to $30\%$ with Cosmic Explorer and to $\sim 3\%$ to $12\%$ with LISA.

We show the first results of a new cavity based haloscope searching for dark photons with masses around $34~\mu\text{eV}$. Dark photons are hypothetical vector particles and a compelling dark matter candidate. Having the same quantum numbers as photons a kinematic mixing between both is expected, leading to conversions from dark photons to standard model photons, where the photon frequency depends on the dark photon mass. For wavelengths in the microwave regime resonators are typically used to enhance the signal. A new experiment is setup at the University of Mainz. In this paper we present the initial results from the new setup searching for dark photons utilising a 8.3 GHz copper cavity at LHe temperatures. Limits on the kinetic mixing parameter $\chi < (6.20 \pm 3.15^\text{(exp.)} \pm 9.65^\text{(SG)}) \cdot 10^{-14}$ at 95\% CL are set at a single frequency as proof of concept. Finally the next steps of the experiment and expected sensitivity are detailed.

Gravitational wave detection has opened up new avenues for exploring and understanding some of the fundamental principles of the universe. The optimal method for detecting modelled gravitational-wave events involves template-based matched filtering and doing a multi-detector search in the resulting signal-to-noise ratio time series. In recent years, advancements in machine learning and deep learning have led to a flurry of research into using these techniques to replace matched filtering searches and for efficient and robust parameter estimation. This paper presents a novel approach that utilizes deep learning techniques to detect gravitational waves from the signal-to-noise ratio time series produced from matched filtering. We do this to investigate if an efficient deep-learning model could replace the computationally expensive post-processing in current search pipelines. We present a feasibility study where we look to detect gravitational waves from binary black hole mergers in simulated stationary Gaussian noise from the LIGO detector in Hanford, Washington. We show that our model can match the performance of a single-detector matched filtering search and that the ranking statistic from the output of our model was robust over unseen noise, exhibiting promising results for practical online implementation in the future. We discuss the possible implications of this work and its future applications to gravitational-wave detection.

Ultra-light Dark Matter (ULDM) is one of the most promising DM candidates. In the presence of background photon radiation, the annihilation rate of the ULDM can be greatly enhanced due to the Bose enhancement. We propose to utilize such stimulated annihilation to probe the ULDM by emitting a beam of radio into the space. This could lead to a distinctive reflected electromagnetic wave with an angular frequency equal to the ULDM mass. We show that low-frequency radio telescopes, such as LOFAR, UTR-2 and ngBOLO, can offer a new avenue of detecting this signal, especially for the Earth halo model. With a power of 50 MW emitter, the expected limits could be several orders of magnitude stronger than that from Big Bang nucleosynthesis (BBN) in the ULDM mass $m_\phi$ range, $2.07 \times 10^{-8}\mathrm{~eV} \sim 4.5 \times 10^{-8}\mathrm{~eV}$.