Papers for Wednesday, Nov 15 2023

In observational studies of infrared dark clouds, the number of detections of CO freeze-out onto dust grains (CO depletion) at pc-scale is extremely limited, and the conditions for its occurrence are, therefore, still unknown. We report a new object where pc-scale CO depletion is expected. As a part of Kagoshima Galactic Object survey with Nobeyama 45-m telescope by Mapping in Ammonia lines (KAGONMA), we have made mapping observations of NH3 inversion transition lines towards the star-forming region associated with the CMa OB1 including IRAS 07077-1026, IRAS 07081-1028, and PGCC G224.28-0.82. By comparing the spatial distributions of the NH3 (1,1) and C18O (J=1-0), an intensity anti-correlation was found in IRAS 07077-1026 and IRAS 07081-1028 on the ~1 pc scale. Furthermore, we obtained a lower abundance of C18O at least in IRAS 07077-1026 than in the other parts of the star-forming region. After examining high density gas dissipation, photodissociation, and CO depletion, we concluded that the intensity anti-correlation in IRAS 07077-1026 is due to CO depletion. On the other hand, in the vicinity of the centre of PGCC G224.28-0.82, the emission line intensities of both the NH3 (1,1) and C18O (J=1-0) were strongly detected, although the gas temperature and density were similar to IRAS 07077-1026. This indicates that there are situations where C18O (J=1-0) cannot trace dense gas on the pc scale and implies that the conditional differences that C18O (J=1-0) can and cannot trace dense gas are unclear.

We provide an explanation for the reduced dynamical friction on galactic bars in spinning dark matter halos. Earlier work based on linear theory predicted an increase in dynamical friction when dark halos have a net forward rotation, because prograde orbits couple to bars more strongly than retrograde orbits. Subsequent numerical studies, however, found the opposite trend: dynamical friction weakens with increasing spin of the halo. We revisit this problem and demonstrate that linear theory in fact correctly predicts a reduced torque in forward-rotating halos. We show that shifting the halo mass from retrograde to prograde phase space generates a positive gradient in the distribution function near the origin of the z-angular momentum (Lz=0), which results in a resonant transfer of Lz to the bar, making the net dynamical friction weaker. While this effect is subdominant for the major resonances, including the corotation resonance, it leads to a significant positive torque on the bar for the series of direct radial resonances, as these resonances are strongest at Lz=0. The overall dynamical friction from spinning halos is shown to decrease with the halo's spin, in agreement with the secular behavior of N-body simulations. We validate our linear calculation by computing the nonlinear torque from individual resonances using the angle-averaged Hamiltonian.

We present the integrated VLT-MUSE spectrum of the central 2'x2' (30x30 pc$^{2}$) of NGC 2070, the dominant giant HII region of the Tarantula Nebula in the Large Magellanic Cloud, together withan empirical far-ultraviolet spectrum constructed via LMC template stars from the ULLYSES survey and Hubble Tarantula Treasury Project UV photometry. NGC 2070 provides a unique opportunity to compare results from individual stellar populations (e.g. VLT FLAMES Tarantula Survey) in a metal-poor starburst region to the integrated results from the population synthesis tools Starburst99, Charlot & Bruzual and BPASS. The metallicity of NGC 2070 inferred from standard nebular strong line calibrations is 0.4$\pm$0.1 dex lower than obtained from direct methods. The Halpha inferred age of 4.2 Myr from Starburst99 is close to the median age of OB stars within the region, although individual stars span a broad range of 1-7 Myr. The inferred stellar mass is close to that obtained for the rich star cluster R136 within NGC 2070, although this contributes only 21% to the integrated far-UV continuum. HeII 1640 emission is dominated by classical WR stars and main sequence WNh+Of/WN stars. 18% of the NGC~2070 far UV continuum flux arises from very massive stars with >100 Msun, including several very luminous Of supergiants. None of the predicted population synthesis models at low metallicities are able to successfully reproduce the far-UV spectrum of NGC 2070. We attribute issues to the treatment of mass-loss in very massive stars, the lack of contemporary empirical metal-poor templates, plus WR stars produced via binary evolution.

Models of Jupiter s interior struggle to agree with measurements of the atmospheric composition. Interior models favour a subsolar or solar abundance of heavy elements Z while atmospheric measurements suggest a supersolar abundance. One potential solution may be the presence of an inverted Z-gradient, namely an inward decrease of Z, which implies a larger heavy element abundance in the atmosphere than in the outer envelope. We investigate two scenarios in which the inverted Z gradient is located either where helium rain occurs (Mbar level) or at upper levels (kbar level) where a radiative region could exist. We aim to assess how plausible these scenarios are. We calculate interior and evolution models of Jupiter with such inverted Z-gradient and use constraints on the stability and the formation of an inverted Z-gradient. We find that an inverted Z-gradient at the location of helium rain cannot work as it requires a late accretion and of too much material. We find interior models with an inverted Z-gradient at upper levels, due to a radiative zone preventing downward mixing, that could satisfy the present gravity field of the planet. However, our evolution models suggest that this second scenario might not be in place. An inverted Z-gradient in Jupiter could be stable. Yet, its presence either at the Mbar level or kbar level is rather unlikely.

We present results of a search for transiting exoplanets in 10-yr long photometry with thousands of epochs taken in the direction of the Galactic bulge. This photometry was collected in the fourth phase of the Optical Gravitational Lensing Experiment (OGLE-IV). Our search covered approx. 222 000 stars brighter than I = 15.5 mag. Selected transits were verified using a probabilistic method. The search resulted in 99 high-probability candidates for transiting exoplanets. The estimated distances to these targets are between 0.4 kpc and 5.5 kpc, which is a significantly wider range than for previous transit searches. The planets found are Jupiter-size, with the exception of one (named OGLE-TR-1003b) located in the hot Neptune desert. If the candidate is confirmed, it can be important for studies of highly irradiated intermediate-size planets. The existing long-term, high-cadence photometry of our candidates increases the chances of detecting transit timing variations at long timescales. Selected candidates will be observed by the future NASA flagship mission, the Nancy Grace Roman Space Telescope, in its search for Galactic bulge microlensing events, which will further enhance the photometric coverage of these stars.

Massive neutrinos have non-negligible impact on the formation of large-scale structures. We investigate the impact of massive neutrinos on the halo assembly bias effect, measured by the relative halo bias $\hat{b}$ as a function of the curvature of the initial density peak $\hat{s}$, neutrino excess $\epsilon_\nu$, or halo concentration $\hat{c}$, using a large suite of $\Sigma M_\nu{=}0.0$ eV and $0.4$ eV simulations with the same initial conditions. By tracing dark matter haloes back to their initial density peaks, we construct a catalogue of halo ``twins'' that collapsed from the same peaks but evolved separately with and without massive neutrinos, thereby isolating any effect of neutrinos on halo formation. We detect a $2\%$ weakening of the halo assembly bias as measured by $\hat{b}(\epsilon_\nu)$ in the presence of massive neutrinos. Due to the significant correlation between $\hat{s}$ and $\epsilon_\nu$~($r_{cc}{=}0.319$), the impact of neutrinos persists in the halo assembly bias measured by $\hat{b}(\hat{s})$ but reduced by an order of magnitude to $0.1\%$. As the correlation between $\hat{c}$ and $\epsilon_\nu$ drops to $r_{cc}{=}0.087$, we do not detect any neutrino-induced impact on $\hat{b}(\hat{c})$, consistent with earlier studies. We also discover an equivalent assembly bias effect for the ``neutrino haloes'', whose concentrations are anti-correlated with the large-scale clustering of neutrinos.

Nearly every massive galaxy contains a supermassive black hole (BH) at its center. For decades, both theory and numerical simulations have indicated that BHs play a central role in regulating the growth and quenching of galaxies. Specifically, BH feedback by heating or blowing out the interstellar medium (ISM) serves as the groundwork for current models of massive galaxy formation. However, direct evidence for such an impact on the galaxy-wide ISM from BHs has only been found in some extreme objects. For general galaxy populations, it remains unclear whether and how BHs impact the ISM. Here based on a large sample of nearby galaxies with measurements of masses of both black holes and atomic hydrogen, the major component of cold ISM, we reveal that the atomic hydrogen content ($f_{\rm HI} = M_{\rm HI}/M_{\star}$) is tightly and anti-correlated with black hole mass ($M_{\rm BH}$) with $f_{\rm HI} \propto M^{-\alpha}_{\rm BH}$ ($\alpha \sim 0.5-0.6$). This correlation is valid across five orders of magnitude in $M_{\rm BH}$. Once this correlation is taken into account, $f_{\rm HI}$ loses dependence on other galactic parameters, demonstrating that $M_{\rm BH}$ serves as the primary driver of $f_{\rm HI}$. These findings provide critical evidence for how the accumulated energy from BH accretion impacts galaxy-wide ISM, representing a crucial step forward in our understanding on the role of BHs in regulating the growth and quenching of massive galaxies.

Our understanding of how the size of galaxies has evolved over cosmic time is based on the use of the half-light (effective) radius as a size indicator. Although the half-light radius has many advantages for structurally parameterising galaxies, it does not provide a measure of the global extent of the objects, but only an indication of the size of the region containing the innermost 50% of the galaxy's light. Therefore, the observed mild evolution of the effective radius of disc galaxies with cosmic time is conditioned by the evolution of the central part of the galaxies rather than by the evolutionary properties of the whole structure. Expanding on the works by Trujillo et al. (2020) and Chamba et al. (2022), we study the size evolution of disc galaxies using as a size indicator the radial location of the gas density threshold for star formation. As a proxy to evaluate this quantity, we use the radial position of the truncation (edge) in the stellar surface mass density profiles of galaxies. To conduct this task, we have selected 1048 disc galaxies with M$_{\rm stellar}$ $>$ 10$^{10}$ M$_{\odot}$ and spectroscopic redshifts up to z=1 within the HST CANDELS fields. We have derived their surface brightness, colour and stellar mass density profiles. Using the new size indicator, the observed scatter of the size-mass relation (~0.1 dex) decreases by a factor of ~2 compared to that using the effective radius. At a fixed stellar mass, Milky Way-like (M$_{\rm stellar}$ ~ 5$\times$10$^{10}$ M$_{\odot}$) disc galaxies have on average increased their sizes by a factor of two in the last 8 Gyr, while the surface stellar mass density at the edge position has decreased by more than an order of magnitude from ~13 M$_{\odot}$/pc$^2$ (z=1) to ~1 M$_{\odot}$/pc$^2$ (z=0). These results reflect a dramatic evolution of the outer part of MW-like disc galaxies, growing ~1.5 kpc Gyr$^{-1}$.

The Advanced X-ray Imaging Satellite (AXIS) promises revolutionary science in the X-ray and multi-messenger time domain. AXIS will leverage excellent spatial resolution (<1.5 arcsec), sensitivity (80x that of Swift), and a large collecting area (5-10x that of Chandra) across a 24-arcmin diameter field of view to discover and characterize a wide range of X-ray transients from supernova-shock breakouts to tidal disruption events to highly variable supermassive black holes. The observatory's ability to localize and monitor faint X-ray sources opens up new opportunities to hunt for counterparts to distant binary neutron star mergers, fast radio bursts, and exotic phenomena like fast X-ray transients. AXIS will offer a response time of <2 hours to community alerts, enabling studies of gravitational wave sources, high-energy neutrino emitters, X-ray binaries, magnetars, and other targets of opportunity. This white paper highlights some of the discovery science that will be driven by AXIS in this burgeoning field of time domain and multi-messenger astrophysics.

Recent studies on the environmental dependence of Type Ia supernova (SN Ia) luminosity focus on the local environment where the SN exploded, considering that this is more directly linked to the SN progenitors. However, there is a debate about the local environmental, specifically local star formation rate (SFR), dependence of the SN Ia luminosity. A recent study claims that the dependence is insignificant ($0.051 \pm 0.020$ mag; $2.6\sigma$), based on the local SFR measurement by fitting local $ugrizy$ photometry data. However, we find that this photometric local SFR measurement is inaccurate. We argue this based on the theoretical background of SFR measurement and the methodology used to make that claim with their local $ugrizy$ photometry data, especially due to a limited range of extinction parameters used when fitting the data. Therefore, we re-analyse the same host galaxies with the same fitting code, but with more physically motivated extinction treatments and global $ugriz$ photometry of host galaxies. We estimate global stellar mass and SFR. Then, local star formation environments are inferred by using the method which showed that SNe Ia in globally passive galaxies have locally passive environments, while those in globally star-forming low-mass galaxies have locally star-forming environments. We find that there is significant local environmental dependence of SN Ia luminosities: SNe Ia in locally star-forming environments are $0.072\pm0.021$ mag ($3.4\sigma$) fainter than those in locally passive environments, even though SN Ia luminosities have been further corrected by the BBC method that reduces the size of the dependence.

Recent discoveries of a super-virial hot phase of the Milky Way circumgalactic medium (CGM) has launched new questions regarding the multi-phase structure of the CGM around the Galaxy. We use 1.05 Ms of archival Chandra/HETG observations to characterize highly ionized metal absorption at z=0 along the line of sight of the quasar NGC 3783. We detect two distinct temperature phases with T$_1 = 5.83^{+0.15}_{-0.07}$ K, warm-hot virial temperature, and T$_2=6.61^{+0.12}_{-0.06}$ K, hot super-virial temperature. The super-virial hot phase coexisting with the warm-hot virial phase has been detected in absorption along only two other sightlines and in one stacking analysis. There is scatter in temperature of the hot as well as warm-hot gas. Similar to previous observations, we detect super-solar abundance ratios of metals in the hot phase, with a Ne/O ratio 2$\sigma$ above solar mixtures. These new detections continue the mystery of the mechanism behind the super-virial hot phase, but provide evidence that this is a true property of the CGM rather than an isolated observation. The super-virial CGM could hold the key to understanding the physical and chemical history of the Milky Way.

Stellar and black hole feedback heat and disperse surrounding cold gas clouds, launching gas flows off circumnuclear and galactic disks and producing a dynamic interstellar medium. On large scales bordering the cosmic web, feedback drives enriched gas out of galaxies and groups, seeding the intergalactic medium with heavy elements. In this way, feedback shapes galaxy evolution by shutting down star formation and ultimately curtailing the growth of structure after the peak at redshift 2-3. To understand the complex interplay between gravity and feedback, we must resolve both the key physics within galaxies and map the impact of these processes over large scales, out into the cosmic web. The Advanced X-ray Imaging Satellite (AXIS) is a proposed X-ray probe mission for the 2030s with arcsecond spatial resolution, large effective area, and low background. AXIS will untangle the interactions of winds, radiation, jets, and supernovae with the surrounding ISM across the wide range of mass scales and large volumes driving galaxy evolution and trace the establishment of feedback back to the main event at cosmic noon.

Pairs of active galactic nuclei (AGN) are observational flags of merger-driven SMBH growth, and represent an observable link between galaxy mergers and gravitational wave (GW) events. Thus, studying these systems across their various evolutionary phases can help quantify the role mergers play in the growth of SMBHs as well as future GW signals expected to be detected by pulsar timing arrays (PTAs). At the earliest stage, the system can be classified as a "dual AGN" where the SMBHs are gravitationally unbound and have typical separations <30 kpc, and at the latest stage the system can be classified as a "binary AGN" where the two massive host galaxies have likely been interacting for hundreds of megayears to gigayears. However, detecting and confirming pairs of AGN is non-trivial, and is complicated by the unique characteristics of merger-environments. To date, there are less than 50 X-ray confirmed dual AGN and only 1 strong binary AGN candidate. AXIS will revolutionize the field of dual AGN: the point-spread-function (PSF), field-of-view (FOV), and effective area (Aeff) are expected to result in the detection of hundreds to thousands of new dual AGN across the redshift range 0 < z < 4. The AXIS AGN surveys will result in the first X-ray study that quantifies the frequency of dual AGN as a function of redshift up to z = 3.5.

We present JWST imaging from 2$\mu$m to 21$\mu$m of the edge-on protoplanetary disk around the embedded young star IRAS04302+2247. The structure of the source shows two reflection nebulae separated by a dark lane. The source extent is dominated by the extended filamentary envelope at $\sim$4.4$\mu$m and shorter wavelengths, transitioning at 7$\mu$m and longer wavelengths to more compact lobes of scattered light from the disk itself. The dark lane thickness does not vary significantly with wavelength, which we interpret as an indication for intermediate-sized ($\sim10\mu$m) grains in the upper layers of the disk. Intriguingly, we find that the brightest nebula of IRAS40302 switches side between 12.8$\mu$m and 21$\mu$m. We explore the effect of a tilted inner region on the general appearance of edge-on disks. We find that radiative transfer models of a disk including a tilted inner region can reproduce an inversion in the brightest nebula. In addition, for specific orientations, the model also predicts strong lateral asymmetries, which can occur for more than half possible viewing azimuths. A large number of edge-on protoplanetary disks observed in scattered light show such lateral asymmetries (15/20), which suggests that a large fraction of protoplanetary disks might host a tilted inner region. Stellar spots may also induce lateral asymmetries, which are expected to vary over a significantly shorter timescale. Variability studies of edge-on disks would allow to test the dominant scenario for the origin of these asymmetries.

The nature and origin of supermassive black holes (SMBHs) remain an open matter of debate within the scientific community. While various theoretical scenarios have been proposed, each with specific observational signatures, the lack of sufficiently sensitive X-ray observations hinders the progress of observational tests. In this white paper, we present how AXIS will contribute to solving this issue. With an angular resolution of 1.5$^{\prime\prime}$ on-axis and minimal off-axis degradation, we have designed a deep survey capable of reaching flux limits in the [0.5-2] keV range of approximately 2$\times$10$^{-18}$ \fcgs~ over an area of 0.13 deg$^2$ in approximately 7 million seconds (7 Ms). Furthermore, we have planned an intermediate depth survey covering approximately 2 deg$^2$ and reaching flux limits of about 2$\times$10$^{-17}$ \fcgs ~ in order to detect a significant number of SMBHs with X-ray luminosities (L$_X$) of approximately 10$^{42}$ \lx up to z$\sim$10. These observations will enable AXIS to detect SMBHs with masses smaller than 10$^5$ \ms, assuming Eddington-limited accretion and a typical bolometric correction for Type II AGN. AXIS will provide valuable information on the seeding and population synthesis models of SMBH, allowing for more accurate constraints on their initial mass function (IMF) and accretion history from z$\sim$0-10. To accomplish this, AXIS will leverage the unique synergy of survey telescopes such as JWST, Roman, Euclid, LSST, and the new generation of 30m class telescopes. These instruments will provide optical identification and redshift measurements, while AXIS will discover the smoking gun of nuclear activity, particularly in the case of highly obscured AGN or peculiar UV spectra as predicted and recently observed in the early Universe.

The theory of superfluid dark matter is characterized by self-interacting sub-eV particles that thermalize and condense to form a superfluid core in galaxies. Massive black holes at the center of galaxies, however, modify the dark matter distribution and result in a density enhancement in their vicinity known as dark matter spikes. The presence of these spikes affects the evolution of binary systems by modifying their gravitational wave emission and inducing dynamical friction effects on the orbiting bodies. In this work, we assess the role of dynamical friction for bodies moving through a superfluid core enhanced by a central massive black hole. As a first step, we compute the dynamical friction force experienced by bodies moving in a circular orbit. Then, we estimate the gravitational wave dephasing of the binary, showing that the effect of the superfluid drag force is beyond the reach of space-based experiments like LISA, contrarily to collisionless dark matter, therefore providing an opportunity to distinguish these dark matter models.

Compact objects and supernova remnants provide nearby laboratories to probe the fate of stars after they die, and the way they impact, and are impacted by, their surrounding medium. The past five decades have significantly advanced our understanding of these objects, and showed that they are most relevant to our understanding of some of the most mysterious energetic events in the distant Universe, including Fast Radio Bursts and Gravitational Wave sources. However, many questions remain to be answered. These include: What powers the diversity of explosive phenomena across the electromagnetic spectrum? What are the mass and spin distributions of neutron stars and stellar mass black holes? How do interacting compact binaries with white dwarfs - the electromagnetic counterparts to gravitational wave LISA sources - form and behave? Which objects inhabit the faint end of the X-ray luminosity function? How do relativistic winds impact their surroundings? What do neutron star kicks reveal about fundamental physics and supernova explosions? How do supernova remnant shocks impact cosmic magnetism? This plethora of questions will be addressed with AXIS - the Advanced X-ray Imaging Satellite - a NASA Probe Mission Concept designed to be the premier high-angular resolution X-ray mission for the next decade. AXIS, thanks to its combined (a) unprecedented imaging resolution over its full field of view, (b) unprecedented sensitivity to faint objects due to its large effective area and low background, and (c) rapid response capability, will provide a giant leap in discovering and identifying populations of compact objects (isolated and binaries), particularly in crowded regions such as globular clusters and the Galactic Center, while addressing science questions and priorities of the US Decadal Survey for Astronomy and Astrophysics (Astro2020).

One of the key research themes identified by the Astro2020 decadal survey is Worlds and Suns in Context. The Advanced X-ray Imaging Satellite (AXIS) is a proposed NASA APEX mission that will become the prime high-energy instrument for studying star-planet connections from birth to death. This work explores the major advances in this broad domain of research that will be enabled by the AXIS mission, through X-ray observations of stars in clusters spanning a broad range of ages, flaring M-dwarf stars known to host exoplanets, and young stars exhibiting accretion interactions with their protoplanetary disks. In addition, we explore the ability of AXIS to use planetary nebulae, white dwarfs, and the Solar System to constrain important physical processes from the microscopic (e.g., charge exchange) to the macroscopic (e.g., stellar wind interactions with the surrounding interstellar medium).

The existence of large-scale anisotropy can not be ruled out by the cosmic microwave background (CMB) radiation. Over the years, several models have been proposed in the context of anisotropic inflation to account for CMB's cold spot and hemispheric asymmetry. However, any small-scale anisotropy, if exists during inflation, is not constrained due to its nonlinear evolution in the subsequent phase. This small-scale anisotropy during inflation can play a non-trivial role in giving rise to the cosmic magnetic field, which is the subject of our present study. Assuming a particular phenomenological form of an anisotropic inflationary universe, we have shown that it can generate a large-scale magnetic field at $1$-Mpc scale with a magnitude $\sim 4\times 10^{-20}~G$, within the observed bound. Because of the anisotropy, the conformal flatness property is lost, and the Maxwell field is generated even without explicit coupling. This immediately resolves the strong coupling problem in the standard magnetogenesis scenario. In addition, assuming very low conductivity during the reheating era, we can further observe the evolution of the electromagnetic field with the equation of state (EoS) $\omega_{eff}$ and its effects on the present-day magnetic field.

Microquasar stellar systems emit electromagnetic radiation and high-energy particles. Thanks to their location within our own galaxy, they can be observed in high detail. Still, many of their inner workings remain elusive; hence, simulations, as the link between observations and theory, are highly useful. In this paper, both high-energy particle and synchrotron radio emissions from simulated microquasar jets are calculated using special relativistic imaging. A finite ray speed imaging algorithm is employed on hydrodynamic simulation data, producing synthetic images seen from a stationary observer. A hydrodynamical model is integrated in the above emission models. Synthetic spectra and maps are then produced that can be compared to observations from detector arrays. As an application, the model synthetically observes microquasars during an episodic ejection at two different spatio-temporal scales: one on the neutrino emission region scale and the other on the synchrotron radio emission scale. The results are compared to the sensitivity of existing detectors.

Recently a manuscript by Loeb et al. was uploaded to arXiv (preprint 2308.15623) that asserted that the CNEOS bolide 2014-01-08 was interstellar; that spherules recovered from the seafloor near the airburst were associated with this bolide; that they had Fe isotopic ratios indicating origin as micrometeorites; that they had unusual chemical compositions enriched in Be, La and U, never seen before in micrometeorite spherules; that these compositions were formed in the magma ocean stage of a differentiated extrasolar planet; and that the Be abundance reflected passage through the interstellar medium. Despite not being peer-reviewed, this uploaded manuscript has been reported by media outlets as "published", and its conclusions have been widely distributed as fact. The purpose of this manuscript is to provide potential peer reviewers and the general public with an appreciation of the multiple fatal flaws with the manuscript's arguments. We discuss the published evidence that the 2014-01-08 bolide is not interstellar. We show that there is no statistical spatial correlation of a chemical signature or even number of recovered spherules with the 2014-01-08 bolide. We demonstrate that the Fe isotopic ratios decisively indicate an origin in our Solar System, with > 99.995% probability. We demonstrate that the unusual enrichments in La, U, etc., have in fact been observed in micrometeorites before and attributed to terrestrial contamination; and that the Be abundances are similarly consistent with those of ferromanganese nodules, after reacting with sea water. Far from being exotic particles from an extrasolar planet, the spherules collected and analyzed by Loeb et al. appear to be just like those found around the world, with a Solar System origin and compositions modified by tens of thousands of years residence at the ocean bottom.

The performance of the proposed MATHUSLA detector as an instrument for studying the physics of cosmic rays by measuring extensive air showers is presented. The MATHUSLA detector is designed to observe and study the decay of long-lived particles produced at the pp interaction point of the CMS detector at CERN during the HL-LHC data-taking period. The proposed MATHUSLA detector will be composed of many layers of long scintillating bars that cannot measure more than one hit per bar and correctly report the hit coordinate in case of multiple hits. This study shows that adding a layer of RPC detectors with both analogue and digital readout significantly enhances the capabilities of MATHUSLA to measure the local densities and arrival times of charged particles at the front of air showers. We discuss open issues in cosmic-ray physics that the proposed MATHUSLA detector with an additional layer of RPC detectors could address and conclude by comparing with other air-shower facilities that measure cosmic rays in the PeV energy range.

We report on the results of a simulation based study of colliding magnetized plasma flows. Our set-up mimics pulsed power laboratory astrophysical experiments but, with an appropriate frame change, are relevant to astrophysical jets with internal velocity variations. We track the evolution of the interaction region where the two flows collide. Cooling via radiative loses are included in the calculation. We systematically vary plasma beta ($\beta_m$) in the flows, the strength of the cooling ($\Lambda_0$) and the exponent ($\alpha$) of temperature-dependence of the cooling function. We find that for strong magnetic fields a counter-propagating jet called a "spine" is driven by pressure from shocked toroidal fields. The spines eventually become unstable and break apart. We demonstrate how formation and evolution of the spines depends on initial flow parameters and provide a simple analytic model that captures the basic features of the flow.

We report the first detection of variability in the mid-infrared neon line emission of a protoplanetary disk by comparing a JWST MIRI MRS spectrum of SZ Cha taken in 2023 with a Spitzer IRS SH spectrum of this object from 2008. We measure the [Ne III]-to-[Ne II] line flux ratio, which is a diagnostic of the high-energy radiation field, to distinguish between the dominance of EUV- or X-ray-driven disk photoevaporation. We find that the [Ne III]-to-[Ne II] line flux ratio changes significantly from $\sim1.4$ in 2008 to $\sim0.2$ in 2023. This points to a switch from EUV-dominated to X-ray-dominated photoevaporation of the disk. We present contemporaneous ground-based optical spectra of the Halpha emission line that show the presence of a strong wind in 2023. We propose that this strong wind prevents EUV radiation from reaching the disk surface while the X-rays permeate the wind and irradiate the disk. We speculate that at the time of the Spitzer observations, the wind was suppressed and EUV radiation reached the disk. These observations confirm that the MIR neon emission lines are sensitive to changes in high-energy radiation reaching the disk surface. This highlights the [Ne III]-to-[Ne II] line flux ratio as a tool to gauge the efficiency of disk photoevaporation in order to provide constraints on the planet-formation timescale. However, multiwavelength observations are crucial to interpret the observations and properly consider the star-disk connection.

A proposed setting for thermonuclear (Type Ia) supernovae is a white dwarf that has gained mass from a companion to the point of carbon ignition in the core. There is a simmering phase in the early stages of burning that involves the formation and growth of a core convection zone. One aspect of this phase is the convective Urca process, a linking of weak nuclear reactions to convection that may alter the composition and structure of the white dwarf. Convective Urca is not well understood and requires 3D fluid simulations to realistically model. Additionally, the convection is relatively slow (Mach number less than 0.005) so a low-Mach method is needed to make simulating computationally feasible. Using the MAESTROeX low-Mach hydrodynamics code, we investigate recent changes to how the weak reactions are modeled in the convective Urca simulations. We present results that quantify the changes to the reaction rates and their impact on the evolution of the simulation.

The Axion Dark Matter eXperiment (ADMX) has previously excluded Dine-Fischler-Srednicki-Zhitnisky (DFSZ) axions between 680-790 MHz under the assumption that the dark matter is described by the isothermal halo model. However, the precise nature of the velocity distribution of dark matter is still unknown, and alternative models have been proposed. We report the results of a non-virialized axion search over the mass range 2.81-3.31 {\mu}eV, corresponding to the frequency range 680-800 MHz. This analysis marks the most sensitive search for non-virialized axions sensitive to Doppler effects in the Milky Way Halo to date. Accounting for frequency shifts due to the detector's motion through the Galaxy, we exclude cold flow relic axions with a velocity dispersion of order 10^-7 c with 95% confidence.

In this report, we present the results of our analysis of trace position changes during NIRISS/SOSS observations. We examine the visit-to-visit impact of the GR700XD pupil wheel (PW) position alignment on trace positions for spectral orders 1 and 2 using the data obtained to date. Our goal is to improve the wavelength solution by correlating the trace positions on the detector with the PW position angle. We find that there is a one-to-one correspondence between PW position and spectral trace rotation for both orders. This allowed us in turn to find an analytic model that is able to predict a trace position/shape as a function of PW position with sub-pixel accuracy of about ~0.1 pixels. Such a function can be used to predict the trace position in low signal-to-noise ratio cases, and/or as a template to track trace position changes as function of time in Time Series Observations (TSOs).

When utilizing the NIRISS/SOSS mode on JWST, the pupil wheel (tasked with orienting the GR700XD grism into the optical path) does not consistently settle into its commanded position resulting in a minor misalignment with deviations of a few fractions of a degree. These small offsets subsequently introduce noticeable changes in the trace positions of the NIRISS SOSS spectral orders between visits. This inconsistency, in turn, can lead to variations of the wavelength solution. In this report, we present the visit-to-visit characterization of the NIRISS GR700XD Wavelength Calibration for spectral orders 1 and 2. Employing data from Calibration Program 1512 (PI: Espinoza), which intentionally and randomly sampled assorted pupil wheel positions during observations of the A-star BD+60-1753, as well as data from preceding commissioning and calibration activities to model this effect, we demonstrate that the wavelength solution can fluctuate in a predictable fashion between visits by up to a few pixels. We show that via two independent polynomial regression models for spectral orders 1 and 2, respectively, using the measured x-pixel positions of known Hydrogen absorption features in the A-star spectra and pupil wheel positions as regressors, we can accurately predict the wavelength solution for a particular visit with an RMS error within a few tenths of a pixel. We incorporate these models in PASTASOSS, a Python package for predicting the GR700XD spectral traces, which now allows to accurately predict spectral trace positions and their associated wavelengths for any NIRISS/SOSS observation.

Recent laboratory experiments have revealed that destructive collisions of icy dust particles may occur at much lower velocities than previously believed. These low fragmentation velocities push down the maximum grain size in collisional growth models. Motivated by the smooth radial distribution of pebble sizes inferred from ALMA/VLA multi-wavelength continuum analysis, we propose a concise model to explain this feature and aim to constrain the turbulence level at the midplane of protoplanetary disks. Our approach is built on the assumption that the fragmentation threshold is the primary barrier limiting pebble growth within pressure maxima. Consequently, the grain size at the ring location can provide direct insights into the turbulent velocity governing pebble collisions and, by extension, the turbulence level at the disk midplane. We validate this method using the Dustpy code, which simulates dust transport and coagulation. We apply our method to 7 disks, TW Hya, IM Lup, GM Aur, AS 209, HL Tau, HD 163296, and MWC 480, for which grain sizes have been measured from multi-wavelength continuum analysis. A common feature emerges from our analysis, with an overall low turbulence coefficient of $\alpha\sim10^{-4}$ observed in five out of seven disks when taking fragmentation velocity $v_{\rm frag} = 1{\rm \,m\,s}^{-1}$. A higher fragmentation velocity would imply a turbulence coefficient significantly larger than the current observational constraints. IM Lup stands out with a relatively higher coefficient of $10^{-3}$. Notably, HL Tau exhibits an increasing trend in $\alpha$ with distance, which supports enhanced turbulence at its outer disk region, possibly associated with the infalling streamer onto HL~Tau. The current (sub)mm pebble size constrained in disks implies low levels of turbulence, as well as fragile pebbles consistent with recent laboratory measurements.

We develop two new highly efficient estimators to measure the polarization (Stokes parameters) in experiments that constrain the position angle of individual photons such as scattering and gas-pixel-detector polarimeters, and analyse in detail a previously proposed estimator. All three of these estimators are at least fifty percent more efficient on typical datasets than the standard estimator used in the field. We present analytic estimates of the variance of these estimators and numerical experiments to verify these estimates. Two of the three estimators can be calculated quickly and directly through summations over the measurements of individual photons.

Blue large-amplitude pulsators (BLAPs) are hot low-mass stars which show large-amplitude light variations likely due to radial oscillations driven by iron-group opacities. Period changes provide evidence of both secular contraction and expansion amongst the class. Various formation histories have been proposed, but none are completely satisfactory. \citet{Zhang2017} proposed that the merger of a helium core white dwarf with a low-mass main-sequence star (HeWD+MS) can lead to the formation of some classes of hot subdwarf. We have analyzed these HeWD+MS merger models in more detail. Between helium-shell ignition and full helium-core burning, the models pass through the volume of luminosity -- gravity-- temperature space occupied by BLAPs. Periods of expansion and contraction associated with helium-shell flashes can account for the observed rates of period change. We argue that the HeWD+MS merger model provides at least one BLAP formation channel.

Track reconstruction algorithms are critical for polarization measurements. In addition to traditional moment-based track reconstruction approaches, convolutional neural networks (CNN) are a promising alternative. However, hexagonal grid track images in gas pixel detectors (GPD) for better anisotropy do not match the classical rectangle-based CNN, and converting the track images from hexagonal to square results in loss of information. We developed a new hexagonal CNN algorithm for track reconstruction and polarization estimation in X-ray polarimeters, which was used to extract emission angles and absorption points from photoelectron track images and predict the uncertainty of the predicted emission angles. The simulated data of PolarLight test were used to train and test the hexagonal CNN models. For individual energies, the hexagonal CNN algorithm produced 15-30% improvements in modulation factor compared to moment analysis method for 100% polarized data, and its performance was comparable to rectangle-based CNN algorithm newly developed by IXPE team, but at a much less computational cost.

We present radio observations of 24 confirmed and candidate strongly lensed quasars identified by the Gaia Gravitational Lenses (GraL) working group. We detect radio emission from 8 systems in 5.5 and 9 GHz observations with the Australia Telescope Compact Array (ATCA), and 12 systems in 6 GHz observations with the Karl G. Jansky Very Large Array (VLA). The resolution of our ATCA observations is insufficient to resolve the radio emission into multiple lensed images, but we do detect multiple images from 11 VLA targets. We have analysed these systems using our observations in conjunction with existing optical measurements, including measuring offsets between the radio and optical positions, for each image and building updated lens models. These observations significantly expand the existing sample of lensed radio quasars, suggest that most lensed systems are detectable at radio wavelengths with targeted observations, and demonstrate the feasibility of population studies with high resolution radio imaging.

Complementary metal-oxide semiconductor (CMOS) sensors have been widely used as soft X-ray detectors in several fields owing to their recent developments and unique advantages. The parameters of CMOS detectors have been extensively studied and evaluated. However, the key parameter signal-to-noise ratio in certain fields has not been sufficiently studied. In this study, we analysed the charge distribution of the CMOS detector GSENSE2020BSI and proposed a two-dimensional segmentation method to discriminate signals according to the charge distribution. The effect of the two-dimensional segmentation method on the GSENSE2020BSI dectector was qualitatively evaluated. The optimal feature parameters used in the two-dimensional segmentation method was studied for G2020BSI. However, the two-dimensional segmentation method is insensitive to feature parameters.

Helioseismology has discovered a thin layer beneath the solar surface where the rotation rate increases rapidly with depth. The normalized rotational shear in the upper 10 Mm of the layer is constant with latitude. Differential rotation theory explains such a rotational state by a radial-type anisotropy of the near-surface convection and a short correlation time of convective turbulence compared to the rotation period. The shear layer is the main driver of the global meridional circulation.

We present an analysis of spectroscopic data of the cool, highly magnetic and polluted white dwarf 2MASS J0916-4215. The atmosphere of the white dwarf is dominated by hydrogen, but numerous spectral lines of magnesium, calcium, titanium, chromium, iron, strontium, along with Li I, Na I, Al I, and K I lines, are found in the incomplete Paschen-Back regime, most visibly, in the case of Ca II lines. Extensive new calculations of the Paschen-Back effect in several spectral lines are presented and results of the calculations are tabulated for the Ca II H&K doublet. The abundance pattern shows a large lithium and strontium excess, which may be viewed as a signature of planetary debris akin to Earth's continental crust accreted onto the star, although the scarcity of silicon indicates possible dilution in bulk Earth material. Accurate abundance measurements proved sensitive to the value of the broadening parameter due to collisions with neutral hydrogen (Gamma_HI), particularly in saturated lines such as the resonance lines of Ca I and Ca II. We found that Gamma_HI if formulated with values from the literature could be overestimated by a factor of 10 in most resonance lines.

J1935+2154 is known as a source of soft gamma radiation. Hyperflares from magnetar were detected at a frequency of 1.25 GHz on the FAST telescope in May 2020. The magnetar enters the survey conducted on LPA radio telescope at 111 MHz. A check of the previously published (Fedorova et al. 2021) pulse from the magnetar SGR1935+2154 was carried out. The data received on the LPA is recorded in parallel in two modes having low and high frequency-time resolution: 6 channels with a channel width of 415 kHz and a time resolution of \Delta t = 100 ms; 32 channels with a channel width of 78 kHz and a time resolution of \Delta t = 12.5 ms. The original search was carried out using data with low time-frequency resolution. The search for dispersed signals in the meter wavelength range is difficult, compared with the search in the decimeter range, due to scattering proportional to the fourth power of frequency and dispersion smearing of the pulse in frequency channels proportional to the second power of frequency. In order to collect a broadened pulse signal and obtain the best value of S/N, the search was carried out using an algorithm based on the convolution of multichannel data with a scattered pulse pattern. The shape of the template corresponds to the shape of a scattered pulse with a dispersion measure (DM) of 375 pc/cm3. For repeated verification, the same data was used in which the pulse from the magnetar was detected. An additional check of the published pulse was also carried out using data with a higher frequency-time resolution. Since the dispersion smearing in the frequency channel in the 32-channel data is 5 times less than in the 6-channel data, an increase approximately 2 times in the S/N pulse could be expected. Pulse radiation with S/N>4 having a pulse peak shift depending on DM from SGR1935+2154 was not detected in either 32-channel or 6-channel data.

RR Lyrae stars are pulsating stars, many of which also show a long-term variation called the Blazhko effect which is a modulation of amplitude and phase of the lightcurve. In this work, we searched for the incidence rate of the Blazhko effect in the first-overtone pulsating RR Lyrae (RRc) stars of the Galactic halo. The focus was on the Stripe 82 region in the Galactic halo which was studied by Sesar et al using the Sloan Digital Sky Survey (SDSS) data. In their work, 104 RR Lyrae stars were classified as RRc type. We combined their SDSS light curves with Zwicky Transient Facility (ZTF) data, and use them to document the Blazhko properties of these RRc stars. Our analysis showed that among the 104 RRc stars, 8 were rather RRd stars, and were excluded from the study. Out of remaining 96, 34 were Blazhko type, 62 were non-Blazhko type, giving the incidence rate of 35.42% for Blazhko RRc stars. The shortest Blazhko period found was 12.808 +/- 0.001 d for SDSS 747380, while the longest was 3100 +/- 126 d for SDSS 3585856. Combining SDSS and ZTF data sets increased the probability of detecting the small variations due to the Blazhko effect, and thus provided a unique opportunity to find longer Blazhko periods. We found that 85% of RRc stars had the Blazhko period longer than 200 d.

Galaxy angular momenta (spins) contain valuable cosmological information, complementing with their positions and velocities. The baryonic spin direction of galaxies have been probed as a reliable tracer of their host halos and the primordial spin modes. Here we use the TNG100 simulation of the IllustrisTNG project to study the spin magnitude correlations between dark matter, gas and stellar components of galaxy-halo systems, and their evolutions across the cosmic history. We find that these components generate similar initial spin magnitudes from the same tidal torque in Lagrangian space. At low redshifts, the gas component still traces the spin magnitude of dark matter halo and the primordial spin magnitude. However, the traceability of stellar component depends on the $ex$ $situ$ stellar mass fraction, $f_{\rm acc}$. Our results suggest that the galaxy baryonic spin magnitude can also serve as a tracer of their host halo and the initial perturbations, and the similarity of their evolution histories affects the galaxy-halo correlations.

We developed a comprehensive model atom of Sc II-Sc III. Abundances of scandium for a sample of eight unevolved A9-B3 type stars with well-determined atmospheric parameters were determined based on the non-local thermodynamic equilibrium (NLTE) line formation for Sc II-Sc III and high-resolution observed spectra. For the Sc II lines, the abundance differences between NLTE and LTE grow rapidly with increasing effective temperature (Teff), from slightly negative at Teff = 7250 K to positive ones of up to 0.6 dex at Teff = 10400 K. For Sc III in $\iota$ Her, NLTE reduces the line-to-line scatter substantially compared to the LTE case. The NLTE abundances of Sc in our five superficially normal stars are consistent within the error bars with the solar system Sc abundance, while the LTE abundances of the late B-type stars are greatly subsolar. NLTE reduces, but does not remove a deficiency of Sc in the Am stars HD 72660 and Sirius. Based on our own and the literature data, the Ca/Sc abundance ratios of the sample of 16 Am stars were found to be close together, with [Ca/Sc] = 0.6-0.7. We propose the Ca/Sc abundance ratio, but not abundances of individual Ca and Sc elements to be used for classifying a star as Am and for testing the diffusion models. We provide the NLTE abundance corrections for ten lines of Sc II in a grid of model atmospheres appropriate for A to late B-type stars.

Line observations of young stellar objects (YSOs) at (sub)millimeter wavelengths provide essential information of gas kinematics in star and planet forming environments. For Class 0 and I YSOs, identification of Keplerian rotation is of particular interest, because it reveals presence of rotationally-supported disks that are still being embedded in infalling envelopes and enables us to dynamically measure the protostellar mass. We have developed a python library SLAM (Spectral Line Analysis/Modeling) with a primary focus on analyses of emission line data at (sub)millimeter wavelengths. Here, we present an overview of the pvanalysis tool from SLAM, which is designed to identify Keplerian rotation of a disk and measure the dynamical mass of a central object using a position-velocity (PV) diagram of emission line data. The advantage of this tool is that it analyzes observational features of given data and thus requires few computational time and parameter assumptions, in contrast to detailed radiative transfer modelings. In this article, we introduce the basic concept and usage of this tool, present an application to observational data, and discuss remaining caveats.

Polarization of the cosmic microwave background (CMB) can help probe the fundamental physics behind cosmic inflation via the measurement of primordial $B$ modes. As this requires exquisite control over instrumental systematics, some next-generation CMB experiments plan to use a rotating half-wave plate (HWP) as polarization modulator. However, the HWP non-idealities, if not properly treated in the analysis, can result in additional systematics. In this paper, we present a simple, semi-analytical end-to-end model to propagate the HWP non-idealities through the macro-steps that make up any CMB experiment (observation of multi-frequency maps, foreground cleaning, and power spectra estimation) and compute the HWP-induced bias on the estimated tensor-to-scalar ratio, $r$. We find that the effective polarization efficiency of the HWP suppresses the polarization signal, leading to an underestimation of $r$. Laboratory measurements of the properties of the HWP can be used to calibrate this effect, but we show how gain calibration of the CMB temperature can also be used to partially mitigate it. On the basis of our findings, we present a set of recommendations for the HWP design that can help maximize the benefits of gain calibration.

We determine the ortho/para ratios of NH2D and NHD2 in two dense, starless cores, where their formation is supposed to be dominated by gas-phase reactions, which, in turn, is predicted to result in deviations from the statistical spin ratios. The Large APEX sub-Millimeter Array (LAsMA) multibeam receiver of the Atacama Pathfinder EXperiment (APEX) telescope was used to observe the prestellar cores H-MM1 and Oph D in Ophiuchus in the ground-state lines of ortho and para NH2D and NHD2. The fractional abundances of these molecules were derived employing 3D radiative transfer modelling, using different assumptions about the abundance profiles as functions of density. We also ran gas-grain chemistry models with different scenarios concerning proton or deuteron exchanges and chemical desorption from grains to find out if one of these models can reproduce the observed spin ratios. The observationally deduced ortho/para ratios of NH2D and NHD2 are in both cores within 10% of their statistical values 3 and 2, respectively, and taking 3-sigma limits, deviations from these of about 20% are allowed. Of the chemistry models tested here, the model that assumes proton hop (as opposed to full scrambling) in reactions contributing to ammonia formation, and a constant efficiency of chemical desorption, comes nearest to the observed abundances and spin ratios. The nuclear spin ratios derived here are in contrast with spin-state chemistry models that assume full scrambling in proton donation and hydrogen abstraction reactions leading to deuterated ammonia. The efficiency of chemical desorption influences strongly the predicted abundances of NH3, NH2D, and NHD2, but has a lesser effect on their ortho/para ratios. For these the proton exchange scenario in the gas is decisive. We suggest that this is because of rapid re-processing of ammonia and related cations by gas-phase ion-molecule reactions.

We present JCMT POL-2 850 um dust polarization observations and Mimir H band stellar polarization observations toward the starless core L1512. We detect the highly-ordered core-scale magnetic field traced by the POL-2 data, of which the field orientation is consistent with the parsec-scale magnetic fields traced by Planck data, suggesting the large-scale fields thread from the low-density region to the dense core region in this cloud. The surrounding magnetic field traced by the Mimir data shows a wider variation in the field orientation, suggesting there could be a transition of magnetic field morphology at the envelope scale. L1512 was suggested to be presumably older than 1.4 Myr in a previous study via time-dependent chemical analysis, hinting that the magnetic field could be strong enough to slow the collapse of L1512. In this study, we use the Davis-Chandrasekhar-Fermi method to derive a plane-of-sky magnetic field strength ($B_{pos}$) of 18$\pm$7 uG and an observed mass-to-flux ratio ($\lambda_{obs}$) of 3.5$\pm$2.4, suggesting that L1512 is magnetically supercritical. However, the absence of significant infall motion and the presence of an oscillating envelope are inconsistent with the magnetically supercritical condition. Using a Virial analysis, we suggest the presence of a hitherto hidden line-of-sight magnetic field strength of ~27 uG with a mass-to-flux ratio ($\lambda_{tot}$) of ~1.6, in which case both magnetic and kinetic pressures are important in supporting the L1512 core. On the other hand, L1512 may have just reached supercriticality and will collapse at any time.

There is a class of binary post-AGB stars that are surrounded by Keplerian disks and that often present outflows resulting from gas escaping from the disk. We present maps and complex models of 12CO and 13CO J=2-1 emission lines for four objects: AC Herculis, 89 Herculis, IRAS 19125+0343, and R Scuti. Our maps and models allow us to study their morphology, kinematics, and mass distribution. Our maps and modeling of AC Her reveal that 95% of the total nebular mass is located in the disk. So this source is a disk-dominated source (like the Red Rectangle, IW Carinae, IRAS 08544-4431). On the contrary, our maps and modeling of 89 Herculis, IRAS 19125+0343, and R Scuti suggest that the outflow is the dominant component of the nebula, resulting in a new subclass nebulae around binary post-AGB stars: the outflow-dominated ones. Besides CO, the molecular content of this kind of sources was barely known. We also present the first and very deep single-dish radio molecular survey in the 1.3, 2, 3, 7, and 13 mm bands. Our results allow us to classify our sources as O- or C-rich. We also conclude that these sources present in general a low molecular richness, especially those that are disk-dominated, compared to circumstellar envelopes around AGB stars and other post-AGB stars. This thesis presents a comprehensive study at millimetre wavelengths. On the one hand, we perform a detailed kinetic study of these objects through NOEMA interferometric observations and complex models. On the other hand, we study the chemistry of these sources, thanks to our sensitive single-dish observations. The union of these different methods yields a comprehensive study of the molecular gas present in these sources. Hopefully, this Ph.D. thesis will become a reference for future studies of molecular gas in nebulae around binary post-AGB stars.

The various successes of Milgrom's MOND have led to suggestions that its critical acceleration parameter $a_0 \approx 1.2\times 10^{-10}\,mtrs/sec^2$ is a fundamental physical constant in the same category as the gravitational constant (for example), and therefore requiring no further explanation. There is no independent evidence supporting this conjecture. Motivated by empirical indications of self-similarities on the exterior part of the optical disk (the optical annulus), we describe a statistical analysis of four large samples of optical rotation curves and find that quantitative indicators of self-similar dynamics on the optical annulus are irreducibly present in each of the samples. These symmetries lead to the unambiguous identification of a characteristic point, $(R_c,V_c)$, on each annular rotation curve where $R_c \approx f(M,S)$ and $V_c \approx g(M)$ for absolute magnitude $M$ and surface brightness $S$. This opens the door to an investigation of the behaviour of the associated characteristic acceleration $a_c \equiv V_c^2/R_c$ across each sample. The first observation is that since $a_c \approx g^2(M)/f(M,S)$, then $a_c$ is a constant within any given disk, but varies between disks. Calculation then shows that $a_c$ varies in the approximate range $(1.2\pm0.5)\times 10^{-10}\,mtrs/sec^2$ for each sample. It follows that Milgrom's $a_0$ is effectively identical to $a_c$, and his critical acceleration boundary is actually the characteristic boundary, $R=R_c$, on any given disk. Since $a_c$ varies between galaxies, then so must $a_0$ also. In summary,Milgrom's critical acceleration boundary is an objective characteristic of the optical disk and $a_0$ cannot be a fundamental physical constant.

We constrain cosmology and baryonic feedback scenarios with a joint analysis of weak lensing, galaxy clustering, cosmic microwave background (CMB) lensing, and their cross-correlations (so-called 6$\times$2) using data from the Dark Energy Survey (DES) Y1 and the Planck satellite mission. Noteworthy features of our 6$\times$2 pipeline are: We extend CMB lensing cross-correlation measurements to a band surrounding the DES Y1 footprint (a $\sim 25\%$ gain in pairs), and we develop analytic covariance capabilities that account for different footprints and all cross-terms in the 6$\times$2 analysis. We also measure the DES Y1 cosmic shear two-point correlation function (2PCF) down to $0.^\prime 25$, but find that going below $2.^\prime 5$ does not increase cosmological information due to shape noise. We model baryonic physics uncertainties via the amplitude of Principal Components (PCs) derived from a set of hydro-simulations. Given our statistical uncertainties, varying the first PC amplitude $Q_1$ is sufficient to model small-scale cosmic shear 2PCF. For DES Y1+Planck 6$\times$2 we find $S_8=0.799\pm0.016$, comparable to the 5$\times$2 result of DES Y3+SPT/Planck $S_8=0.773\pm0.016$. Combined with our most informative cosmology priors -- baryon acoustic oscillation (BAO), big bang nucleosynthesis (BBN), type Ia supernovae (SNe Ia), and Planck 2018 EE+lowE, we measure $S_8=0.817\pm 0.011$. Regarding baryonic physics constraints, our 6$\times$2 analysis finds $Q_1=2.8\pm1.8$. Combined with the aforementioned priors, it improves the constraint to $Q_1=3.5\pm1.3$. For comparison, the strongest feedback scenario considered in this paper, the cosmo-OWLS AGN ($\Delta T_\mathrm{heat}=10^{8.7}$ K), corresponds to $Q_1=5.84$.

Brown dwarfs serve as ideal laboratories for studying the atmospheres of giant exoplanets on wide orbits as the governing physical and chemical processes in them are nearly identical. Understanding the formation of gas giant planets is challenging, often involving the endeavour to link atmospheric abundance ratios, such as the carbon-to-oxygen (C/O) ratio, to formation scenarios. However, the complexity of planet formation requires additional tracers, as the unambiguous interpretation of the measured C/O ratio is fraught with complexity. Isotope ratios, such as deuterium-to-hydrogen and 14N/15N, offer a promising avenue to gain further insight into this formation process, mirroring their utility within the solar system. For exoplanets only a handful of constraints on 12C/13C exist, pointing to the accretion of 13C-rich ice from beyond the disks' CO iceline. Here we report on the mid-infrared detection of the 14NH3 and 15NH3 isotopologues in the atmosphere of a cool brown dwarf with an effective temperature of 380 K in a spectrum taken with the Mid-InfraRed Instrument of the James Webb Space Telescope. As expected, our results reveal a 14N/15N value consistent with star-like formation by gravitational collapse, demonstrating that this ratio can be accurately constrained. Since young stars and their planets should be more strongly enriched in the 15N isotope, we expect that 15NH3 will be detectable in a number of cold, wide-separation exoplanets.

The wavelength-coverage and sensitivity of JWST now enables us to probe the rest-frame UV - optical spectral energy distributions (SEDs) of galaxies at high-redshift ($z>4$). From these SEDs it is, in principle, through SED fitting possible to infer key physical properties, including stellar masses, star formation rates, and dust attenuation. These in turn can be compared with the predictions of galaxy formation simulations allowing us to validate and refine the incorporated physics. However, the inference of physical properties, particularly from photometry alone, can lead to large uncertainties and potential biases. Instead, it is now possible, and common, for simulations to be \emph{forward-modelled} to yield synthetic observations that can be compared directly to real observations. In this work, we measure the JWST broadband fluxes and colours of a robust sample of $5<z<10$ galaxies using the Cosmic Evolution Early Release Science (CEERS) Survey. We then analyse predictions from a variety of models using the same methodology and compare the NIRCam/F277W magnitude distribution and NIRCam colours with observations. We find that the predicted and observed magnitude distributions are similar, at least at $5<z<8$. At $z>8$ the distributions differ somewhat, though our observed sample size is small and thus susceptible to statistical fluctuations. Likewise, the predicted and observed colour evolution show broad agreement, at least at $5<z<8$. There is however some disagreement between the observed and modelled strength of the strong line contribution. In particular all the models fails to reproduce the F410M-F444W colour at $z>8$, though, again, the sample size is small here.

Vast amounts of astronomical photometric data are generated from various projects, requiring significant efforts to identify variable stars and other object classes. In light of this, a general, widely applicable classification framework would simplify the task of designing custom classifiers. We present a novel deep learning framework for classifying light curves using a weakly supervised object detection model. Our framework identifies the optimal windows for both light curves and power spectra automatically, and zooms in on their corresponding data. This allows for automatic feature extraction from both time and frequency domains, enabling our model to handle data across different scales and sampling intervals. We train our model on datasets obtained from both space-based and ground-based multi-band observations of variable stars and transients. We achieve an accuracy of 87% for combined variables and transient events, which is comparable to the performance of previous feature-based models. Our trained model can be utilized directly to other missions, such as ASAS-SN, without requiring any retraining or fine-tuning. To address known issues with miscalibrated predictive probabilities, we apply conformal prediction to generate robust predictive sets that guarantee true label coverage with a given probability. Additionally, we incorporate various anomaly detection algorithms to empower our model with the ability to identify out-of-distribution objects. Our framework is implemented in the Deep-LC toolkit, which is an open-source Python package hosted on Github and PyPI.

Magnetar magnetospheres are strongly twisted, and are able to power sudden energetic events through the rapid release of stored electromagnetic energy. In this paper, we investigate twisted relativistic force-free axisymmetric magnetospheres of rotating neutron stars. We obtain numerical solutions of such configurations using the method of simultaneous relaxation for the magnetic field inside and outside the light-cylinder. We introduce a toroidal magnetic field in the region of closed field-lines that is associated with a poloidal electric current distribution in that region, and explore various mathematical expressions for that distribution. We find that, by increasing the twist, a larger fraction of magnetic field-lines crosses the light-cylinder and opens up to infinity, thus increasing the size of the polar caps and enhancing the spin-down rate. We also find that, for moderately to strongly twisted magnetospheres, the region of closed field-lines ends at some distance inside the light-cylinder. We discuss the implications of these solutions on the variation of magnetar spin-down rates, moding and nulling of pulsars, the relation between the angular shear and the twist and the overall shape of the magnetosphere.

Pulsar search is always the basis of pulsar navigation, gravitational wave detection and other research topics. Currently, the volume of pulsar candidates collected by Five-hundred-meter Aperture Spherical radio Telescope (FAST) shows an explosive growth rate that has brought challenges for its pulsar candidate filtering System. Particularly, the multi-view heterogeneous data and class imbalance between true pulsars and non-pulsar candidates have negative effects on traditional single-modal supervised classification methods. In this study, a multi-modal and semi-supervised learning based pulsar candidate sifting algorithm is presented, which adopts a hybrid ensemble clustering scheme of density-based and partition-based methods combined with a feature-level fusion strategy for input data and a data partition strategy for parallelization. Experiments on both HTRU (The High Time Resolution Universe Survey) 2 and FAST actual observation data demonstrate that the proposed algorithm could excellently identify the pulsars: On HTRU2, the precision and recall rates of its parallel mode reach 0.981 and 0.988. On FAST data, those of its parallel mode reach 0.891 and 0.961, meanwhile, the running time also significantly decrease with the increment of parallel nodes within limits. So, we can get the conclusion that our algorithm could be a feasible idea for large scale pulsar candidate sifting of FAST drift scan observation.

We study the resolved stellar populations and derive the star formation history of NGC 5474, a peculiar star-forming dwarf galaxy at a distance of $\sim 7$ Mpc, using Hubble Space Telescope Advanced Camera for Surveys data from the Legacy Extragalactic UV Survey (LEGUS) program. We apply an improved colour-magnitude diagram fitting technique based on the code SFERA and use the latest PARSEC-COLIBRI stellar models. Our results are the following. The off-centre bulge-like structure, suggested to constitute the bulge of the galaxy, is dominated by star formation (SF) activity initiated $14$ Gyr ago and lasted at least up to $1$ Gyr ago. Nevertheless, this component shows clear evidence of prolonged SF activity (lasting until $\sim 10$ Myr ago). We estimate the total stellar mass of the bulge-like structure to be $(5.0 \pm 0.3) \times 10^{8}$ \MSUN. Such a mass is consistent with published suggestions that this structure is in fact an independent system orbiting around and not within NGC 5474's disc. The stellar over-density located to the South-West of the bulge-like structure shows a significant SF event older than $1$ Gyr, while it is characterised by two recent peaks of SF, around $\sim10$ and $\sim100$ Myr ago. In the last Gyr, the behavior of the stellar disc is consistent with what is known in the literature as `gasping'. The synchronised burst at $10-35$ Myr in all components might hint to the recent gravitational interaction between the stellar bulge-like structure and the disc of NGC 5474.

The classical nova, AT 2023prq, was discovered on 2023 August 15 and is located at a distance of 46 kpc from the Andromeda Galaxy (M 31). Here we report photometry and spectroscopy of the nova. The 'very fast' ($t_{2,r^{\prime}}\sim3.4$ d) and low luminosity ($M_{r^{\prime}}\sim-7.6$) nature of the transient along with the helium in its spectra would indicate that AT 2023prq is a 'faint-and-fast' He/N nova. Additionally, at such a large distance from the centre of M 31, AT 2023prq is a member of the halo nova population.

Here we explore the impact of all major factors, such as the non-homogeneous gas distribution, galactic rotation and gravity, on the observational appearance of superbubbles in nearly face-on spiral galaxies. The results of our 3D numerical simulations are confronted to the observed gas column density distribution in the largest South-East superbubble in the late-type spiral galaxy NGC 628. We make use of the star formation history inside the bubble derived from the resolved stellar population seen in the HST images to obtain its energy and demonstrate that the results of numerical simulations are in good agreement with the observed gas surface density distribution. We also show that the observed gas column density distribution constraints the gaseous disk scale height and the midplane gas density if the energy input rate could be obtained from observations. This implies that observations of large holes in the interstellar gas distribution and their stellar populations have the potential power to solve the midplane gas density - gaseous disk scale-height degeneracy problem in nearly face-on galaxies. The possible role of superbubbles in driving the secondary star formation in galaxies is also briefly discussed.

Convolutional neural networks (CNNs) are the state-of-the-art technique for identifying strong gravitational lenses. Although they are highly successful in recovering genuine lens systems with a high true-positive rate, the unbalanced nature of the data set (lens systems are rare), still leads to a high false positive rate. For these techniques to be successful in upcoming surveys (e.g. with Euclid) most emphasis should be set on reducing false positives, rather than on reducing false negatives. In this paper, we introduce densely connected neural networks (DenseNets) as the CNN architecture in a new pipeline-ensemble model containing an ensemble of classification CNNs and regression CNNs to classify and rank-order lenses, respectively. We show that DenseNets achieve comparable true positive rates but considerably lower false positive rates (when compared to residual networks; ResNets). Thus, we recommend DenseNets for future missions involving large data sets, such as Euclid, where low false positive rates play a key role in the automated follow-up and analysis of large numbers of strong gravitational lens candidates when human vetting is no longer feasible

The radio astronomy community is adopting deep learning techniques to deal with the huge data volumes expected from the next-generation of radio observatories. Bayesian neural networks (BNNs) provide a principled way to model uncertainty in the predictions made by deep learning models and will play an important role in extracting well-calibrated uncertainty estimates from the outputs of these models. However, most commonly used approximate Bayesian inference techniques such as variational inference and MCMC-based algorithms experience a "cold posterior effect (CPE)", according to which the posterior must be down-weighted in order to get good predictive performance. The CPE has been linked to several factors such as data augmentation or dataset curation leading to a misspecified likelihood and prior misspecification. In this work we use MCMC sampling to show that a Gaussian parametric family is a poor variational approximation to the true posterior and gives rise to the CPE previously observed in morphological classification of radio galaxies using variational inference based BNNs.

New photometry, including TESS data, have been combined with recent spectroscopic observations of the Orion Ib pulsating triple-star system VV Ori. This yields a revised set of absolute parameters with increased precision. Two different programs were utilized for the light curve analysis, with results in predictably close agreement. The agreement promotes confidence in the analysis procedures. The spectra were analysed using the {\sc FDBinary} program. The main parameters are as follows: $M_1 = 11.6 \pm 0.14$ and $M_2 = 4.8 \pm 0.06$ (M$_\odot$). We estimate an approximate mass of the wide companion as $M_3 = 2.0 \pm 0.3$ M$_\odot$. Similarly, $R_{1} = 5.11 \pm 0.03$, $R_2 = 2.51 \pm 0.02$, $R_3 = 1.8 \pm 0.1$ (R$_\odot$); $T_{\rm e 1} = 26600 \pm 300$, $T_{\rm e 2} = 16300 \pm 400$ and $T_{\rm e 3} = 10000 \pm 1000$ (K). The close binary's orbital separation is $a= 13.91$ (R$_\odot$); its age is $8 \pm 2$ (Myr) and its photometric distance is $396 \pm 7$ pc. The primary's $\beta$ Cep type oscillations support these properties and confirm our understanding of its evolutionary status. Examination of the well-defined $\lambda$6678 He I profiles reveals the primary to have a significantly low projected rotation: some 80\% of the synchronous value. This can be explained on the basis of the precession of an unaligned spin axis. This proposal can resolve also observed variations of the apparent inclination and address other longer-term irregularities of the system reported in the literature. This topic invites further observations and follow-up theoretical study of the dynamics of this intriguing young multiple star.

Milky-Way and intergalactic dust extinction and reddening must be accounted for in measurements of distances throughout the universe. This work provides a comprehensive review of the various impacts of cosmic dust focusing specifically on its effects on two key distance indicators used in the distance ladder: Cepheid variable stars and Type Ia supernovae. We review the formalism used for computing and accounting for dust extinction and reddening as a function of wavelength. We also detail the current state of the art knowledge of dust properties in the Milky Way and in host galaxies. We discuss how dust has been accounted for in both the Cepheid and SN distance measurements. Finally, we show how current uncertainties on dust modeling impact the inferred luminosities and distances, but that measurements of the Hubble constant remain robust to these uncertainties.

Revealing the temporal evolution of individual heavy elements synthesized in the merger ejecta from binary neutron star mergers not only improves our understanding of the origin of heavy elements beyond iron but also clarifies the energy sources of kilonovae. In this work, we present a comprehensive analysis of the temporal evolution of the energy fraction of each nuclide based on the $r$-process nucleosynthesis simulations. The heavy elements dominating the kilonova emission within $\sim100$~days are identified, including $^{127}$Sb, $^{128}$Sb, $^{129}$Sb, $^{130}$Sb, $^{129}$Te, $^{132}$I, $^{222}$Rn, $^{223}$Ra, $^{224}$Ra, and $^{225}$Ac. It is found that the late-time kilonova light curve ($t\gtrsim20$~days) is highly sensitive to the presence of the heavy element $^{225}$Ac (with a half-life of 10.0~days). Our analysis shows that the James Webb Space Telescope (JWST), with its high sensitivity in the near-infrared band, is a powerful instrument for the identification of these specific heavy elements.

Type II radio bursts arise as a consequence of shocks typically driven by coronal mass ejections (CMEs). When these shocks propagate outward from the Sun, their associated radio emissions drift down in frequency as excited particles emit at the local plasma frequency, creating the usual Type II patterns. In this work, we use dynamic spectra from the Wind/WAVES Thermal Noise Receiver (TNR) to identify Type II radio emissions in the kilometric wavelength range (kmTIIs, f < 300 kHz) between 1 January 2000 and 31 December 2012, i.e. over a solar cycle. We identified 134 kmTII events and compiled various characteristics for each of them. Of particular importance is the finding of 45 kmTII events not reported by the official Wind/WAVES catalog (based on RAD1 and RAD2 data). We search for associations with interplanetary structures and analyze their main characteristics, in order to reveal distinctive attributes that may correlate with the occurrence of kmTII emission. We find that the fraction of interplanetary coronal mass ejections (ICMEs) classified as magnetic clouds (MCs) that are associated with kmTIIs is roughly similar to that of MCs not associated with kmTIIs. Conversely, the fraction of ICMEs with bidirectional electrons is significantly larger for those ICMEs associated with kmTIIs (74% vs. 48%). Likewise, ICMEs associated with kmTIIs are on average 23% faster. The disturbance storm time (DsT) mean value is almost twice as large for kmTII-associated ICMEs, indicating that they tend to produce intense geomagnetic storms. In addition, the proportion of ICMEs producing moderate to intense geomagnetic storms is twice as large for the kmTII-associated ICMEs. After this investigation, TNR data prove to be valuable not only as complementary data for the analysis of kmTII events but also for forecasting the arrival of shocks at Earth.

We report the discovery of broad components with P-Cygni profiles of the hydrogen and helium emission lines in the two low-redshift low-metallicity dwarf compact star-forming galaxies (SFG), SBS 1420+540 and J1444+4840. We found small stellar masses of 10^{6.24} and 10^{6.59} M$_\odot$, low oxygen abundances 12+log O/H of 7.75 and 7.45, high velocity dispersions reaching $\sigma$ ~700 and ~1200km/s, high terminal velocities of the stellar wind of ~1000 and ~1000-1700km/s, respectively, and large EW(H$\beta$) of ~300A for both. For SBS 1420+540, we succeeded in capturing an eruption phase by monitoring the variations of the broad-to-narrow component flux ratio. We observe a sharp increase of that ratio by a factor 4 in 2017 and a decrease by about an order of magnitude in 2023. The peak luminosity of ~10^{40}ergs/s of the broad component in $L$(H$\alpha$) lasted for about 6 years out of a three-decades monitoring. This leads us to conclude that there is probably a LBV candidate (LBVc) in this galaxy. As for J1444+4840, its very high $L$(H$\alpha$) of about 10^{41}ergs/s, close to values observed in active galactic nuclei (AGNs) and Type IIn Supernovae (SNe), and the variability of no more than 20 per cent of the broad-to-narrow flux ratio of the hydrogen and helium emission lines over a 8-year monitoring do not allow us to definitively conclude that it contains a LBVc. On the other hand, the possibility that the line variations are due to a long-lived stellar transient of type LBV/SNIIn cannot be ruled out.

The Cosmic Microwave Background (CMB) radiation offers a unique window into the early Universe, facilitating precise examinations of fundamental cosmological theories. However, the quest for detecting B-modes in the CMB, predicted by theoretical models of inflation, faces substantial challenges in terms of calibration and foreground modeling. The COSMOCal (COsmic Survey of Millimeter wavelengths Objects for CMB experiments Calibration) project aims at enhancing the accuracy of the absolute calibration of the polarization angle $\psi$ of current and future CMB experiments. The concept includes the build of a very well known artificial source emitting in the frequency range [20-350] GHz that would act as an absolute calibrator for several polarization facilities on Earth. A feasibility study to place the artificial source in geostationary orbit, in the far field for all the telescopes on Earth, is ongoing. In the meanwhile ongoing hardware work is dedicated to build a prototype to test the technology, the precision and the stability of the polarization recovering in the 1 mm band (220-300 GHz). High-resolution experiments as the NIKA2 camera at the IRAM 30m telescope will be deployed for such use. Once carefully calibrated ($\Delta\psi$ < 0.1 degrees) it will be used to observe astrophysical sources such as the Crab nebula, which is the best candidate in the sky for the absolute calibration of CMB experiments.

The sunspot number record covers over three centuries.These numbers measure the activity of the Sun. This activity follows the solar cycle of about eleven years. In the dynamo-theory, the interaction between differential rotation and convection produces the solar magnetic field. On the surface of Sun, this field concentrates to the sunspots. The dynamo-theory predicts that the period, the amplitude and the phase of the solar cycle are stochastic. Here we show that the solar cycle is deterministic, and connected to the orbital motions of the Earth and Jupiter. This planetary-influence theory allows us to model the whole sunspot record, as well as the near past and the near future of sunspot numbers. We may never be able to predict the exact times of exceptionally strong solar flares, like the catastrophic Carrington event in September 1859, but we can estimate when such events are more probable. Our results also indicate that during the next decades the Sun will no longer help us to cope with the climate change. The inability to find predictability in some phenomenon does not prove that this phenomenon itself is stochastic.

We propose to learn latent space representations of radio galaxies, and train a very deep variational autoencoder (\protect\Verb+VDVAE+) on RGZ DR1, an unlabeled dataset, to this end. We show that the encoded features can be leveraged for downstream tasks such as classifying galaxies in labeled datasets, and similarity search. Results show that the model is able to reconstruct its given inputs, capturing the salient features of the latter. We use the latent codes of galaxy images, from MiraBest Confident and FR-DEEP NVSS datasets, to train various non-neural network classifiers. It is found that the latter can differentiate FRI from FRII galaxies achieving \textit{accuracy} $\ge 76\%$, \textit{roc-auc} $\ge 0.86$, \textit{specificity} $\ge 0.73$ and \textit{recall} $\ge 0.78$ on MiraBest Confident dataset, comparable to results obtained in previous studies. The performance of simple classifiers trained on FR-DEEP NVSS data representations is on par with that of a deep learning classifier (CNN based) trained on images in previous work, highlighting how powerful the compressed information is. We successfully exploit the learned representations to search for galaxies in a dataset that are semantically similar to a query image belonging to a different dataset. Although generating new galaxy images (e.g. for data augmentation) is not our primary objective, we find that the \protect\Verb+VDVAE+ model is a relatively good emulator. Finally, as a step toward detecting anomaly/novelty, a density estimator -- Masked Autoregressive Flow (\protect\Verb+MAF+) -- is trained on the latent codes, such that the log-likelihood of data can be estimated. The downstream tasks conducted in this work demonstrate the meaningfulness of the latent codes.

We conduct numerical simulations of multiple nova eruptions in detached, widely separated symbiotic systems that include an asymptotic giant branch (AGB) companion to investigate the impact of white dwarf (WD) mass and binary separation on the evolution of the system. The accretion rate is determined using the Bondi-Hoyle-Lyttleton method, incorporating orbital momentum loss caused by factors such as gravitational radiation, magnetic braking, and drag. The WD in such a system accretes matter coming from the strong wind of an AGB companion until it finishes shedding its envelope. This occurs on an evolutionary time scale of $\approx 3 \times 10^5$ years. Throughout all simulations, we use a consistent AGB model with an initial mass of $1.0 \mathrm {M_\odot}$ while varying the WD mass and binary separation, as they are the critical factors influencing nova eruption behavior. We find that the accretion rate fluctuates between high and low rates during the evolutionary period, significantly impacted by the AGB's mass loss rate. We show that unlike novae in cataclysmic variables, the orbital period may either increase or decrease during evolution, depending on the model, while the separation consistently decreases. Furthermore, we have identified cases in which the WDs produce weak, non-ejective novae and experience mass gain. This suggests that provided the accretion efficiency can be achieved by a more massive WD and maintained for long enough, they could potentially serve as progenitors for type Ia supernovae.

By coupling the EUropean Heliospheric FORcasting Information Asset (EUHFORIA) and the improved Particle Acceleration and Transport in the Heliosphere (iPATH) model, two energetic storm particle (ESP) events, originating from the same active region (AR 13088) and observed by Solar Orbiter (SolO) on August 31 2022 and September 05 2022, are modelled. While both events originated from the same active region, they exhibited notable differences, including: 1) the August ESP event lasted for 7 hours, while the September event persisted for 16 hours; 2) The time intensity profiles for the September event showed a clear cross-over upstream of the shock where the intensity of higher energy protons exceeds those of lower energy protons, leading to positive (``reverse'') spectral indices prior to the shock passage. For both events, our simulations replicate the observed duration of the shock sheath, depending on the deceleration history of the CME. Imposing different choices of escaping length scale, which is related to the decay of upstream turbulence, the modelled time intensity profiles prior to the shock arrival also agree with observations. In particular, the cross-over of this time profile in the September event is well reproduced. We show that a ``reverse'' upstream spectrum is the result of the interplay between two length scales. One characterizes the decay of upstream shock accelerated particles, which are controlled by the energy-dependent diffusion coefficient, and the other characterizes the decay of upstream turbulence power, which is related to the process of how streaming protons upstream of the shock excite Alfv\'{e}n waves. Simulations taking into account real-time background solar wind, the dynamics of the CME propagation, and upstream turbulence at the shock front are necessary to thoroughly understand the ESP phase of large SEP events.

Non-accreting neutron stars display diverse characteristics, leading us to classify them into several groups. This chapter is an observational driven review in which we survey the properties of the different classes of isolated neutron stars: from the 'normal' rotation-powered pulsars, to magnetars, the most magnetic neutron stars in the Universe we know of; from central compact objects (sometimes called also anti-magnetars) in supernova remnants, to the X-ray dim isolated neutron stars. We also highlight a few sources that have exhibited features straddling those of different sub-groups, blurring the apparent diversity of the neutron star zoo and pointing to a gran unification.

We present the first large-scale 3D kinematic study of ~2000 spectroscopically-confirmed young stars (<20 Myr) in 18 star clusters and OB associations (hereafter groups) from the combination of Gaia astrometry and Gaia-ESO Survey spectroscopy. We measure 3D velocity dispersions for all groups, which range from 0.61 to 7.4 km/s (1D velocity dispersions of 0.35 to 4.3 km/s). We find the majority of groups have anisotropic velocity dispersions, suggesting they are not dynamically relaxed. From the 3D velocity dispersions, measured radii and estimates of total mass we estimate the virial state and find that all systems are super-virial when only the stellar mass is considered, but that some systems are sub-virial when the mass of the molecular cloud is taken into account. We observe an approximately linear correlation between the 3D velocity dispersion and the group mass, which would imply that the virial state of groups scales as the square root of the group mass. However, we do not observe a strong correlation between virial state and group mass. In agreement with their virial state we find that nearly all of the groups studied are in the process of expanding and that the expansion is anisotropic, implying that groups were not spherical prior to expansion. One group, Rho Oph, is found to be contracting and in a sub-virial state (when the mass of the surrounding molecular cloud is considered). This work provides a glimpse of the potential of the combination of Gaia and data from the next generation of spectroscopic surveys.

The ages of young star clusters are fundamental clocks to constrain the formation and evolution of pre-main-sequence stars and their protoplanetary disks and exoplanets. However, dating methods for very young clusters often disagree, casting doubts on the accuracy of the derived ages. We propose a new method to derive the kinematic age of star clusters based on the evaporation ages of their stars. The method is validated and calibrated using hundreds of clusters identified in a supernova-driven simulation of the interstellar medium forming stars for approximately 40 Myr within a 250 pc region. We demonstrate that the clusters' evaporation-age uncertainty can be as small as about 10% for clusters with a large enough number of evaporated stars and small but realistic observational errors. We have obtained evaporation ages for a pilot sample of 10 clusters, finding a good agreement with their published isochronal ages. The evaporation ages will provide important constraints for modeling the pre-main-sequence evolution of low-mass stars, as well as to investigate the star-formation and gas-evaporation history of young clusters. These ages can be more accurate than isochronal ages for very young clusters, for which observations and models are more uncertain.

We propose a mechanism to explain the low-frequency QPOs observed in X-ray binary systems and AGNs. To do this, we perturbed stable accretion disks around Kerr and EGB black holes at different angular velocities, revealing the characteristics of shock waves and oscillations presented on the disk. Applying this perturbation to scenarios with different alpha values for EGB black holes and different spin parameters for Kerr black holes, we numerically observed changes in the dynamic structure of the disk and oscillations. Through various numerical modeling, we found that the formation of one- and two-armed spiral shock waves on the disk serves as a mechanism for the generation of QPOs. We compared the QPOs obtained from numerical calculations with the low-frequency QPOs observed in $X-$ray binary systems and AGN sources. We found that the results obtained are highly consistent with observations. We observed that the shock mechanism on the disk, which leads to quasi-periodic oscillations, explains the X-ray binaries and AGNs studied in this article. As a result of the numerical findings, we find that QPOs are more strongly dependent on the EGB constant rather than the black hole's spin parameter However, we highlighted that the primary impact on oscillations and QPOs is driven by the perturbation's angular velocity. According to the results obtained from the models, it has been observed that the perturbation's asymptotic speed at V_{\infty}=0.2 is responsible for generating QPO frequencies independently of the black hole's spin parameter and the EGB coupling constant. Therefore, for the moderate value of V_{\infty}, a two-armed spiral shock wave formed on the disk is suggested as a decisive mechanism in explaining low-frequency QPOs.

As early-type stars with a rotation speed close to their critical velocity, Be stars experience a kind of event called Be phenomenon. The material in their equator during the Be phenomenon, is ejected to the outside space and forms a circumstellar disk. The mechanism triggering these events remains poorly understood, and observations of these events are limited. Long-term epoch photometry in the infrared bands is expected to be ideal for detecting Be phenomena since the brightness variation is larger than that in the optical, and the effect of interstellar extinction is also smaller. In this work, we conducted a systematic search for Be phenomena among Milky Way OBA stars in the mid-infrared. We examined the brightness and colour variations of known classical Be stars using the WISE W1 and W2 photometry bands to quantify their characteristics. Subsequently, we established a set of criteria to identify similar photometric variations in a large sample of OBA stars. 916 OBA stars have been found to show Be phenomena in the past 13 years, with 736 newly discovered. The peak-to-peak variations in magnitude and colour were found to be correlated, indicating the common presence of a decretion disk. The increase in colour was observed to be strongly correlated with the emission of the H_alpha line, providing further evidence of the association with circumstellar disks. The brightness variation of a star with Be phenomena can be up to 1.5 mag, and colour variations up to 0.4 mag. The median durations for the disk build-up and decay phases are 474 and 524 days, respectively (while those less than 180 days are not sampled). The search for Be phenomena in the WISE bands greatly enlarges the number of stars showing disk variation, and makes multi-band photometry analysis of these events possible, with the help of current and future optical photometry surveys.

It is anticipated that the gravitational radiation detected in future gravitational wave (GW) detectors from binary neutron star (NS) mergers can probe the high-density equation of state (EOS). We perform the first simulations of binary NS mergers which adopt various parametrizations of the quark-hadron crossover (QHC) EOS. These are constructed from combinations of a hadronic EOS ($n_{b} < 2~n_0$) and a quark-matter EOS ($n_{b} >~5~n_0$), where $n_{b}$ and $n_0$ are the baryon number density and the nuclear saturation density, respectively. At the crossover densities ($2~ n_0 < n_{b} < 5~ n_0$) the QHC EOSs continuously soften, while remaining stiffer than hadronic and first-order phase transition EOSs, achieving the stiffness of strongly correlated quark matter. This enhanced stiffness leads to significantly longer lifetimes of the postmerger NS than that for a pure hadronic EOS. We find a dual nature of these EOSs such that their maximum chirp GW frequencies $f_{max}$ fall into the category of a soft EOS while the dominant peak frequencies ($f_{peak}$) of the postmerger stage fall in between that of a soft and stiff hadronic EOS. An observation of this kind of dual nature in the characteristic GW frequencies will provide crucial evidence for the existence of strongly interacting quark matter at the crossover densities for QCD.

We investigate the string solutions and cosmological implications of the gauge ${\rm U(1)_Z}\,\times$ global ${\rm U(1)_{PQ}}$ model. With two hierarchical symmetry-breaking scales, the model exhibits three distinct string solutions: a conventional global string, a global string with a heavy core, and a gauge string as a bound state of the two global strings. This model reveals rich phenomenological implications in cosmology. During the evolution of the universe, these three types of strings can form a Y-junction configuration. Intriguingly, when incorporating this model with the QCD axion framework, the heavy-core global strings emit more axion particles compared to conventional axion cosmic strings due to their higher tension. This radiation significantly enhances the QCD axion dark matter abundance, thereby opening up the QCD axion mass window. Consequently, axions with masses exceeding $\sim 10^{-5}\, {\rm eV}$ have the potential to constitute the whole dark matter abundance. Furthermore, in contrast to conventional gauge strings, the gauge strings in this model exhibit a distinctive behavior by radiating axions.

Many models of dark matter include self-interactions beyond gravity. A variety of astrophysical observations have previously been used to place limits on the strength of such self-interactions. However, previous works have generally focused either on short-range interactions resulting in individual dark matter particles scattering from one another, or on effectively infinite-range interactions which sum over entire dark matter halos. In this work, we focus on the intermediate regime: forces with range much larger than dark matter particles' inter-particle spacing, but still shorter than the length scales of known halos. We show that gradients in the dark matter density of such halos would still lead to observable effects. We focus primarily on effects in the Bullet Cluster, where finite-range forces would lead either to a modification of the collision velocity of the cluster or to a separation of the dark matter and the galaxies of each cluster after the collision. We also consider constraints from the binding of ultrafaint dwarf galaxy halos, and from gravitational lensing of the Abell 370 cluster. Taken together, these observations allow us to set the strongest constraints on dark matter self-interactions over at least five orders of magnitude in range, surpassing existing limits by many orders of magnitude throughout.

Recently we estimated that about 5 percent of supermassive black hole triple systems are fundamentally unpredictable. These gargantuan chaotic systems are able to exponentially magnify Planck length perturbations to astronomical scales within their interaction timescale. These results were obtained in the zero angular momentum limit, which we naively expected to be the most chaotic. Here, we generalise to triple systems with arbitrary angular momenta by systematically varying the initial virial ratio. We find the surprising result that increasing the angular momentum enhances the chaotic properties of triples. This is not only explained by the longer life times, allowing for a prolonged exponential growth, but also the maximum Lyapunov exponent itself increases. For the ensemble of initially virialised triple systems, we conclude that the percentage of unpredictable supermassive black hole triples increases to about 30 percent. A further increase up to about 50 percent is reached when considering triples on smaller astrophysical scales. Fundamental unpredictability is thus a generic feature of chaotic, self-gravitating triple populations.

We place limits on dark matter made up of compact objects significantly heavier than a solar mass, such as MACHOs or primordial black holes (PBHs). In galaxies, the gas of such objects is generally hotter than the gas of stars and will thus heat the gas of stars even through purely gravitational interactions. Ultrafaint dwarf galaxies (UFDs) maximize this effect. Observations of the half-light radius in UFDs thus place limits on MACHO dark matter. We build upon previous constraints with an improved heating rate calculation including both direct and tidal heating, and consideration of the heavier mass range above $10^4 \, M_\odot$. Additionally we find that MACHOs may lose energy and migrate in to the center of the UFD, increasing the heat transfer to the stars. UFDs can constrain MACHO dark matter with masses between about $10 M_\odot$ and $10^8 M_\odot$ and these are the strongest constraints over most of this range.

Domain walls (DWs) are topological defects originating from phase transitions in the early universe. In the presence of an energy imbalance between distinct vacua, enclosed DW cavities shrink until the entire network disappears. By studying the dynamics of thin-shell bubbles in General Relativity, we demonstrate that closed DWs with sizes exceeding the cosmic horizon tend to annihilate later than the average. This delayed annihilation allows for the formation of large overdensities, which, upon entering the Hubble horizon, eventually collapse to form Primordial Black Holes (PBHs). We rely on 3D percolation theory to calculate the number density of these late-annihilating DWs, enabling us to infer the abundance of PBHs. A key insight from our study is that DW networks with the potential to emit observable Gravitational Waves are also likely to yield detectable PBHs. Additionally, we study the production of wormholes connected to baby-universes and conclude on the possibility to generate a multiverse.

Despite having important cosmological implications, the reheating phase is believed to play a crucial role in cosmology and particle physics model building. Conventionally, the model of reheating with an arbitrary coupling of inflaton to massless fields naturally lacks precise prediction and hence difficult to verify through observation. In this paper, we propose a simple and natural reheating mechanism where the particle physics model, namely the Type-I seesaw is shown to play a major role in the entire reheating process where inflaton is coupled with all the fields only gravitationally. Besides successfully resolving the well-known neutrino mass and baryon asymmetry problems, the scenario offers successful reheating, predicts distinct primordial gravitational wave spectrum and non-vanishing lowest active neutrino mass. Our novel mechanism opens up a new avenue of integrating particle physics and cosmology in the context of reheating.

As electromagnetic showers may alter the abundance of Helium, Lithium, and Deuterium, we can place severe constraints on the lifetime and amount of electromagnetic energy injected by long-lived particles. Considering up-to-date measurements of the light element abundances that point to $Y_p=0.245\pm 0.003$,$({\rm D/H})= (2.527\pm 0.03)\times 10^{-5}$,$(^7{\rm Li/H})=1.58 ^{+0.35}_{-0.28} \times 10^{-10}$, $(^6{\rm Li/^7 Li})=0.05$, and the baryon-to-photon ratio obtained from the Cosmic Microwave Background data, $\eta=6.104 \times 10^{-10}$, we derive upper limits on the fraction of electromagnetic energy produced by long-lived particles. Our findings apply to decaying dark matter models, long-lived gravitinos, and other non-thermal processes that occurred in the early universe between $10^2-10^{10}$ seconds.

We study rotating compact stars that are mixtures of the ordinary nuclear matter in a neutron star and fermionic dark matter. After deriving equations describing a slowly rotating system made up of an arbitrary number of perfect fluids, we specialize to the two-fluid case, where the first fluid describes ordinary matter and the second fluid describes dark matter. Electromagnetic observations of the moment of inertia and angular momentum directly probe ordinary matter and not dark matter. Upon taking this into account, we show that the I-Love-Q relations for dark matter admixed neutrons stars can deviate significantly from the standard single-fluid relationships.

We explore the cosmological implications of the local limit of nonlocal gravity, which is a classical generalization of Einstein's theory of gravitation within the framework of teleparallelism. An appropriate solution of this theory is the modified Cartesian flat cosmological model. The main purpose of this paper is to study linear perturbations about the orthonormal tetrad frame field adapted to the standard comoving observers in this model. The observational viability of the perturbed model is examined using all available data regarding the cosmic microwave background. The implications of the linearly perturbed modified Cartesian flat model are examined and it is shown that the model is capable of alleviating the $H_0$ tension.

We present the first direct observations of acoustic waves in warm dense matter. We analyze wavenumber- and energy-resolved X-ray spectra taken from warm dense methane created by laser-heating a cryogenic liquid jet. X-ray diffraction and inelastic free electron scattering yield sample conditions of 0.3$\pm$0.1 eV and 0.8$\pm$0.1 g/cm$^3$, corresponding to a pressure of $\sim$13 GPa and matching the conditions predicted in the thermal boundary layer between the inner and outer envelope of Uranus. Inelastic X-ray scattering was used to observe the collective oscillations of the ions. With a highly improved energy resolution of $\sim$50 meV, we could clearly distinguish the Brillouin peaks from the quasi-elastic Rayleigh feature. Data at different wavenumbers were used to obtain a sound speed of 5.9$\pm$0.5 km/s, which enabled us to validate the use of Birch's law in this new parameter regime.

We investigate the dynamics of a rapid-turning dark energy model, which arises from certain inspiraling field-space trajectories. We find the speed of sound $c_s$ of the dark energy perturbations around the background and show that $c_s$ is monotonically decreasing with time. Furthermore, it has a positive-definite lower bound that implies a certain clustering scale. We also extend the previously known background solution for dark energy to an exact solution that includes matter. This allows us to address the implications of our model for two cosmological tensions. More precisely, we argue that the $\sigma_8$ tension can be alleviated generically, while reducing the Hubble tension requires certain constraints on the parameter space of the model. Notably, a necessary condition for alleviating the Hubble tension is that the transition from matter domination to the dark energy epoch begins earlier than in $\Lambda$CDM.

In the past few years, many mesoscale systems have been proposed as possible detectors of sub-GeV dark matter particles. In this work, we point out the feasibility of probing dark matter-nucleon scattering cross section using superconductor-based quantum devices with meV-scale energy threshold. We compute new limits on spin-independent dark matter scattering cross section using the existing power measurement data from three different experiments for MeV to 10 GeV mass. We derive the limits for both halo and thermalized dark matter populations.

Rotating black holes exhibit a remarkable set of hidden symmetries near their horizon. They have been shown to determine phenomena such as absorption scattering, superradiance and more recently tidal deformations, also known as Love numbers. They have also led to a proposal for a dual thermal CFT with left and right movers recovering the entropy of the black hole. In this work we provide a constructive explanation of these hidden symmetries via analytic continuation to Klein signature. We first show that the near-horizon region of extremal black holes is a Kleinian static solution with mass $M$ and NUT charge $N$. We then analyze the self-dual solution, namely a Kerr black hole with a NUT charge $N=\pm M$. Remarkably, the self-dual solution is self-similar to its near-horizon and hence approximate symmetries become exact: in particular, the original two isometries of Kerr are promoted to seven exact symmetries embedded in a conformal algebra. We analyze its full conformal group in Kleinian twistor space, where a breaking $SO(4,2) \to SL(2,\mathbb{R})\times SL(2,\mathbb{R})$ occurs due to the insertion of a preferred time direction for the black hole. Finally, we show that its spectrum is integrable and behaves as the Hydrogen atom, being solvable in terms of elementary polynomials. Perturbing to astrophysical black holes with $N=0$, we obtain a hyperfine splitting structure.

We consider a static, spherically symmetric space-time with an electric field arising from a quadratic metric-affine extension of General Relativity. Such a space-time is free of singularities in the centre of the black holes, while at large distances it quickly boils down to the usual Reissner-Nordstr\"om solution. We probe this space-time metric, which is uniquely characterized by two length scales, $r_q$ and $\ell$, using the astrometric and spectroscopic measurements of the orbital motion of the S2 star around the Galactic Center. Our analysis constrains $r_q$ to be below $2.7M$ for values $\ell<120 AU$, strongly favouring a central object that resembles a Schwarzschild black hole.

One approach to testing general relativity (GR) introduces free parameters in the post-Newtonian (PN) expansion of the gravitational-wave (GW) phase. If systematic errors on these testing GR (TGR) parameters exceed the statistical errors, this may signal a false violation of GR. Here, we consider systematic errors produced by unmodeled binary eccentricity. Since the eccentricity of GW events in ground-based detectors is expected to be small or negligible, the use of quasicircular waveform models for testing GR may be safe when analyzing a small number of events. However, as the catalog size of GW detections increases, more stringent bounds on GR deviations can be placed by combining information from multiple events. In that case, even small systematic biases may become significant. We apply the approach of hierarchical Bayesian inference to model the posterior probability distributions of the TGR parameters inferred from a population of eccentric binary black holes (BBHs). We assume each TGR parameter value varies across the BBH population according to a Gaussian distribution. We compute the posterior distributions for these Gaussian hyperparameters. This is done for LIGO and Cosmic Explorer (CE). We find that systematic biases from unmodeled eccentricity can signal false GR violations for both detectors when considering constraints set by a catalog of events. We also compute the projected bounds on the $10$ TGR parameters when eccentricity is included as a parameter in the waveform model. We find that the first four dimensionless TGR deformation parameters can be bounded at $90\%$ confidence to $\delta \hat{\varphi}_i \lesssim 10^{-2}$ for LIGO and $\lesssim 10^{-3}$ for CE [where $i=(0,1,2,3)$]. In comparison to the circular orbit case, the combined bounds on the TGR parameters worsen by a modest factor of $\lesssim 2$ when eccentricity is included in the waveform.

We apply the gradient expansion approximation to the light-cone gauge, obtaining a separate universe picture at non-linear order in perturbation theory within this framework. Thereafter, we use it to generalize the $\delta N$ formalism in terms of light-cone perturbations. As a consistency check, we demonstrate the conservation of the gauge invariant curvature perturbation on uniform density hypersurface $\zeta$ at the completely non-linear level. The approach studied provides a self-consistent framework to connect at non-linear level quantities from the primordial universe, such as $\zeta$, written in terms of the light-cone parameters, to late time observables.

Supergranule aggregation, i.e., the gradual aggregation of convection cells to horizontally extended networks of flow structures, is a unique feature of constant heat flux-driven turbulent convection. In the present study, we address the question if this mechanism of self-organisation of the flow is present for any fluid. Therefore, we analyse three-dimensional Rayleigh-B\'enard convection at a fixed Rayleigh number $\Ra \approx 2.0 \times 10^{5}$ across $4$ orders of Prandtl numbers $\Pr \in \left[ 10^{-2}, 10^{2} \right]$ by means of direct numerical simulations in horizontally extended periodic domains with aspect ratio $\Gamma = 60$. Our study confirms the omnipresence of the mechanism of supergranule aggregation for the entire range of investigated fluids. Moreover, we analyse the effect of $\Pr$ on the global heat and momentum transport, and clarify the role of a potential stable stratification in the bulk of the fluid layer. The ubiquity of the investigated mechanism of flow self-organisation underlines its relevance for pattern formation in geo- and astrophysical convection flows, the latter of which are often driven by prescribed heat fluxes.