Papers for Tuesday, Sep 20 2022

The maximum mass of a nonrotating neutron star, $M_{\rm TOV}$, plays a very important role in deciphering the structure and composition of neutron stars and in revealing the equation of state (EOS) of nuclear matter. Although with a large-error bar, the recent mass estimate for the black-widow binary pulsar PSR J0952-0607, i.e. $M=2.35\pm0.17~M_\odot$, provides the strongest lower bound on $M_{\rm TOV}$ and suggests that neutron stars with very large masses can in principle be observed. Adopting an agnostic modelling of the EOS, we study the impact that large masses have on the neutron-star properties. In particular, we show that assuming $M_{\rm TOV}\gtrsim 2.35\,M_\odot$ constrains tightly the behaviour of the pressure as a function of the energy density and moves the lower bounds for the stellar radii to values that are significantly larger than those constrained by the NICER measurements, rendering the latter ineffective in constraining the EOS. We also provide updated analytic expressions for the lower bound on the binary tidal deformability in terms of the chirp mass and show how larger bounds on $M_{\rm TOV}$ lead to tighter constraints for this quantity. In addition, we point out a novel quasi-universal relation for the pressure profile inside neutron stars that is only weakly dependent from the EOS and the maximum-mass constraint. Finally, we study how the sound speed and the conformal anomaly are distributed inside neutron stars and show how these quantities depend on the imposed maximum-mass constraints.

We consider a phenomenological model of dark matter with an equation-of-state that is negative and changing at late times. We show this couples the $H_{0}$ and $\sigma_{8}$ tensions, providing an explanation for both simultaneously, while also providing an explanation for the anomalously large integrated Sachs-Wolfe (ISW) effect from cosmic voids. Observations of high ISW from cosmic voids may therefore be evidence that dark matter plays a significant role in the $H_{0}$ and $\sigma_{8}$ tensions. We predict the ISW from cosmic voids to be a factor of ~ 2 greater in this model than what is expected from the standard model $\Lambda$CDM.

Proximity zones of quasars with redshifts $z \gtrsim 6$ are unique probes of the growth of supermassive black holes. But simultaneously explaining proximity zone sizes and black hole masses at this redshift has proved to be challenging because of the very short quasar lifetimes implied by the proximity zones. We study the robustness of some of the assumptions that are usually made to infer quasar lifetimes from proximity zone sizes. We show that thanks to the short equilibration time of gas inside the proximity zones, small proximity zones can be readily explained by quasars that vary in brightness with a short duty cycle of $f_\mathrm{duty}\sim 0.1$ and short bright periods of $t_\mathrm{on}\sim 10^4$ yr, even for long lifetimes. We further show that reconciling this with black hole mass estimates requires the black hole to continue to grow and accrete during its obscured phase. The consequent obscured fractions of $\gtrsim$ 0.7 or higher are consistent with low-redshift measurements and models of black hole accretion. Further, the large dynamic range of our simulation, and its calibration to the Lyman-$\alpha$ forest, allows us to investigate the influence of the large-scale topology of reionization and the quasar's host halo mass on proximity zones. We find that incomplete reionization can impede the growth of proximity zones and make them smaller up to 30%, but the quasar host halo mass only affects proximity zones weakly and indirectly. Our work suggests that high-redshift proximity zones can be an effective tool to study quasar variability and black hole growth.

The Tayler instability is an important but poorly studied magnetohydrodynamic instability that likely operates in stellar interiors. The nonlinear saturation of the Tayler instability is poorly understood and has crucial consequences for dynamo action and angular momentum transport in radiative regions of stars. We perform three-dimensional MHD simulations of the Tayler instability in a cylindrical geometry, including strong buoyancy and Coriolis forces as appropriate for its operation in realistic rotating stars. The linear growth of the instability is characterized by a predominantly $m=1$ oscillation with growth rates roughly following analytical expectations. The non-linear saturation of the instability appears to be caused by secondary shear instabilities and is also accompanied by a morphological change of the flow. We argue, however, that non-linear saturation likely occurs via other mechanisms in real stars where the separation of scales is larger than those reached by our simulations. We also observe dynamo action via the amplification of the axisymmetric poloidal magnetic field, suggesting that Tayler instability could be important for magnetic field generation and angular momentum transport in the radiative regions of evolving stars.

We revisit the role that gravitational scattering off stars plays in establishing the steady-state distribution of collisionless dark matter (DM) around a massive black hole (BH). This is a physically interesting problem that has potentially observable signatures, such as $\gamma-$rays from DM annihilation in a density spike. The system serves as a laboratory for comparing two different dynamical approaches, both of which have been widely used: a Fokker-Planck treatment and a two-component conduction fluid treatment. In our Fokker-Planck analysis we extend a previous analytic model to account for a nonzero flux of DM particles into the BH, as well as a cut-off in the distribution function near the BH due to relativistic effects or, further out, possible DM annihilation. In our two-fluid analysis, following an approximate analytic treatment, we recast the equations as a "heated Bondi accretion" problem and solve the equations numerically without approximation. While both the Fokker-Planck and two-fluid methods yield basically the same DM density and velocity dispersion profiles away from the boundaries in the spike interior, there are other differences, especially the determination of the DM accretion rate. We discuss limitations of the two treatments, including the assumption of an isotropic velocity dispersion.

Tidal friction has long been recognized to circularize the orbits of binary stars over time. In this study, we use the observed distribution of orbital eccentricities in populations of binary stars to probe tidal dissipation. In contrast to previous studies, we incorporate a host of physical effects often neglected in other analyses, provide a much more general description of tides, model individual systems in detail (in lieu of population statistics), and account for all observational uncertainties. The goal is to provide a reliable measurement of the properties of tidal dissipation that is fully supported by the data, properly accounts for different dissipation affecting each tidal wave on each object separately, and evolves with the internal structure of the stars. We extract high precision measurements of tidal dissipation in short period binaries of Sun-like stars in three open clusters. We find that the tidal quality factor on the main sequence falls in the range $5.7 < \log_{10}Q_\star' < 6$ for tidal periods between 3 and 7.5 days. In contrast, the observed circularization in the 150 Myr old M 35 cluster requires that pre-main sequence stars are much more dissipative: $Q_\star' < 4\times10^4$. We test for frequency dependence of the tidal dissipation, finding that for tidal periods between 3 and 7.5 days, if a dependence exists, it is sub-linear for main-sequence stars. Furthermore, by using a more complete physical model for the evolution, and by accounting for the particular properties of each system, we alleviate previously observed tensions in the circularization in the open clusters analyzed.

Today, there exists a wide variety of algorithms dedicated to high-contrast imaging, especially for the detection and characterisation of exoplanet signals. These algorithms are tailored to address the very high contrast between the exoplanet signal(s), which can be more than two orders of magnitude fainter than the bright starlight residuals in coronagraphic images. The starlight residuals are inhomogeneously distributed and follow various timescales that depend on the observing conditions and on the target star brightness. Disentangling the exoplanet signals within the starlight residuals is therefore challenging, and new post-processing algorithms are striving to achieve more accurate astrophysical results. The Exoplanet Imaging Data Challenge is a community-wide effort to develop, compare and evaluate algorithms using a set of benchmark high-contrast imaging datasets. After a first phase ran in 2020 and focused on the detection capabilities of existing algorithms, the focus of this ongoing second phase is to compare the characterisation capabilities of state-of-the-art techniques. The characterisation of planetary companions is two-fold: the astrometry (estimated position with respect to the host star) and spectrophotometry (estimated contrast with respect to the host star, as a function of wavelength). The goal of this second phase is to offer a platform for the community to benchmark techniques in a fair, homogeneous and robust way, and to foster collaborations.

The heliosphere is the magnetic structure formed by the Sun's atmosphere extending into the local interstellar medium (ISM). The boundary separating the heliosphere from the ISM is a still largely unexplored region of space. Even though both Voyager spacecraft entered the local ISM and are delivering data, they are two points piercing a vast region of space at specific times. The heliospheric boundary regulates the penetration of MeV- GeV galactic cosmic rays (CR) in the inner heliosphere. Interstellar keV neutral atoms are crucial to the outer heliosphere since they can penetrate unperturbed and transfer energy to the solar wind. Missions such as NASA's IBEX and Cassini are designed to detect neutral atoms and monitor charge exchange processes at the heliospheric boundary. The heliosphere does not modulate the TeV CR intensity, but it does influence their arrival direction distribution. Ground-based CR observatories have provided accurate maps of CR anisotropy as a function of energy in the last couple of decades. Combining observations to produce all-sky coverage makes it possible to investigate the heliosphere's impact on TeV CR particles. We can numerically calculate the pristine TeV CR distribution in the local ISM with state-of-the-art heliosphere models. Only by subtracting the heliospheric influence is it possible to use TeV CR observations to infer propagation properties and the characteristics of magnetic turbulence in the ISM. Numerical calculations of CR particle trajectories through heliospheric models provide a complementary tool to probe the boundary region properties. A program boosting heliospheric modeling with emphasis on the boundary region and promoting combined CR experimental data analyses from multiple experiments benefits CR astrophysics and provides additional data and tools to explore the interaction between the heliosphere and the local ISM.

We present a new calibration of the J-band absolute magnitude of the JAGB method based on thermally pulsing AGB stars that are members of Milky Way open clusters, having distances and reddenings, independently compiled and published by Marigo et al (2022). 17 of these photometrically-selected J-Branch AGB stars give M_J = -6.40 mag with a scatter of +/-0.40 mag, and a sigma on the mean of +/-0.10 mag. Combining the Milky Way field carbon star calibration of Lee et al. (2021) with this determination gives a weighted average of M_J(MW) = -6.19 +/- 0.04 mag (error on the mean). This value is statistically indistinguishable from the value determined for this population of distance indicators in the LMC and SMC, giving further evidence that JAGB stars are extremely reliable distance indicators of high luminosity and universal applicability. Combining the zero points for JAGB stars in these three systems, a value of M_J = -6.20 +/- 0.01 (stat) +/- 0.04 (sys) mag becomes our best current estimate of the JAGB zero point and its associated errors. Finally, we note that no evidence is found for any statistically significant dependence of this zero point on metallicity.

We perform an analytical study of the stability of the background solution of the model in which an inflaton, through an axionic coupling to a $U(1)$ gauge field, causes an amplification of the gauge field modes that strongly backreact on its dynamics. To this goal, we study the evolution of the gauge field modes coupled to the inflaton zero mode, treating perturbatively the deviation of the inflaton velocity from its mean-field value. As long as the system is in the strong backreaction regime we find that the inflaton velocity performs oscillations of increasing amplitude about the value it would have in mean field approximation, confirming an instability that has been observed in numerical studies.

The Breakthrough Listen Initiative has embarked on a comprehensive SETI survey of nearby stars in the Milky Way that is vastly superior to previous efforts as measured by a wide range of different metrics. SETI surveys traditionally ignore the fact that they are sensitive to many background objects, in addition to the foreground target star. In order to better appreciate and exploit the presence of extragalactic objects in the field of view, the Aladin sky atlas and NED were employed to make a rudimentary census of extragalactic objects that were serendipitously observed with the 100-m Greenbank telescope observing at 1.1-1.9 GHz. For 469 target fields (assuming a FWHM radial field-of-view of 4.2 arcminutes), NED identified a grand total of 143024 extragalactic objects, including various astrophysical exotica e.g. AGN of various types, radio galaxies, interacting galaxies, and one confirmed gravitational lens system. Several nearby galaxies, galaxy groups and galaxy clusters are identified, permitting the parameter space probed by SETI surveys to be significantly extended. Constraints are placed on the luminosity function of potential extraterrestrial transmitters assuming it follows a simple power law and limits on the prevalence of very powerful extraterrestrial transmitters associated with these vast stellar systems are also determined. It is demonstrated that the recent Breakthrough Listen Initiative, and indeed many previous SETI radio surveys, place stronger limits on the prevalence of extraterrestrial intelligence in the distant Universe than is often fully appreciated.

The non-thermal filament (NTF) radio structures clustered within a few hundred parsecs of the Galactic Center (GC) are apparently unique to this region of the Galaxy. Recent radio images of the GC using MeerKAT at 1 GHz have revealed a multitude of faint, previously unknown NTF bundles (NTFBs), some of which are comprised of as many as 10 or more individual filaments. In this work we present Very Large Array (VLA) observations at C- and X-bands (4 - 12 GHz) at arcsecond-scale resolutions of three of these newly-discovered NTFBs, all located at southern Galactic latitudes. These observations allow us to compare their total-intensity properties with those of the larger NTF population. We find that these targets generally possess properties similar to what is observed in the larger NTF population. However, the larger NTF population generally has steeper spectral index values than what we observe for our chosen targets. The results presented here based on the total-intensity properties of these structures indicate that the NTFs are likely all formed from Cosmic Rays (CRs). These CRs are either generated by a nearby compact source and then diffuse along the NTF lengths or are generated by extended, magnetized structures whose magnetic field undergoes reconnection with the NTF magnetic field.

The Babcock-Leighton (BL) flux-transport model is a widely-accepted dynamo model of the Sun. This dynamo model has been extensively studied in a two-dimensional (2D) mean-field framework in both kinematic and non-kinematic regimes. Recent three-dimensional (3D) models have been restricted to the kinematic regime. In these models, the surface poloidal flux is produced by the emergence of bipolar magnetic regions (BMRs) that are tilted according to Joy's law. We investigate the prescription for emergence of a BMR in 3D non-kinematic simulations. We also report initial results of cyclic BL dynamo simulation. We extend a conventional 2D mean-field model of the BL flux-transport dynamo into 3D non-kinematic regime. The large-scale mean flows are driven by the parameterized $\Lambda$-effect in this model. For the induction equation, we use a BL source term by which the surface BMRs are produced in response to the dynamo-generated toroidal field inside the convection zone. We find that, in the 3D non-kinematic regime, the tilt angle of a newly-emerged BMR is very sensitive to the prescription for the subsurface structure of the BMR. Anti-Joy tilt angles are found unless the BMR is deeply embedded in the convection zone. We also find that the leading spot tends to become stronger than the following spot. The anti-Joy's law trend and the morphological asymmetry of the BMRs can be explained by the Coriolis force acting on the Lorentz-force-driven flows. Furthermore, we demonstrate that the solar-like magnetic cycles can be successfully obtained if the Joy's law is explicitly given in the BL $\alpha$-effect. In these cyclic dynamo simulation, a strong Lorentz force feedback leads to cycle modulations in the differential rotation and meridional circulation. The non-axisymmetric components of the flows are found to exist as inertial modes such as the equatorial Rossby modes.

Soon after the discovery of the first extrasolar X-Ray sources it was suggested that polarimetry could play a major role as a diagnostic tool. Attempts to measure polarization of X-Ray sources was performed by the team of Columbia University lead by Robert Novick. The technique of Bragg diffraction at 45{\deg} was successful to detect the polarization of the Crab with rockets and with OSO-8 satellite. In the following evolution of X-Ray Astronomy, Polarimetry was too mismatched with the improved sensitivity of imaging and spectroscopy, based on the use of optics. As a consequence no polarimeter was flown any more. At the beginning of the century a new class of instruments based on the photoelectric effect were developed. In the focus of an X-Ray telescope they can perform angular, energy and time resolved polarimetry and benefit of the large increase of sensitivity due to the optics. The Imaging X-Ray Polarimetry Explorer, exploiting this technique, was launched at the end of 2021.

Interstellar interlopers are bodies formed outside of the solar system but observed passing through it. The first two identified interlopers, 1I/`Oumuamua and 2I/Borisov, exhibited unexpectedly different physical properties. 1I/`Oumuamua appeared unresolved and asteroid-like whereas 2I/Borisov was a more comet-like source of both gas and dust. Both objects moved under the action of non-gravitational acceleration. These interlopers and their divergent properties provide our only window so far onto an enormous and previously unknown galactic population. The number density of such objects is $\sim$ 0.1 AU$^{-3}$ which, if uniform across the galactic disk, would imply 10$^{25}$ to 10$^{26}$ similar objects in the Milky Way. The interlopers likely formed in, and were ejected from, the protoplanetary disks of young stars. However, we currently possess too little data to firmly reject other explanations.

This work presents water emission spectra at wavelengths covered by JWST (2.9-12.8 $\mu$m) as spectrally-resolved with high resolving powers (R = 30,000-100,000) using ground-based spectrographs. Two new surveys with iSHELL and VISIR are combined with previous spectra from CRIRES and TEXES to cover parts of multiple ro-vibrational and rotational bands observable within telluric transmission bands, for a total of 85 disks and $\approx160$ spectra. The general expectation of a range of regions and excitation conditions traced by infrared water spectra is for the first time supported by the combined kinematics and excitation as spectrally resolved at multiple wavelengths. The main findings from this analysis are: 1) water lines are progressively narrower going from the ro-vibrational bands at 2-9 $\mu$m to the rotational lines at 12 $\mu$m, and partly match a broad (BC) and narrow (NC) emission components, respectively, as extracted from ro-vibrational CO spectra; 2) rotation diagrams of resolved water lines from upper level energies of 4000-9500 K show curvatures indicative of optically thick emission ($\approx 10^{18}$ cm$^{-2}$) from a range of excitation temperatures ($\approx$ 800-1100 K); 3) the new 5 $\mu$m spectra demonstrate that slab model fits to the rotational lines at $> 10 \mu$m strongly over-predict the ro-vibrational emission bands at $< 9 \mu$m, implying non-LTE excitation. We discuss these findings in the context of a emission from a disk surface and a molecular inner disk wind, and provide a list of detailed guidelines to support the analysis and interpretation of spectrally-unresolved JWST spectra.

We present the discovery of Bo\"otes V, a new ultra-faint dwarf galaxy candidate. This satellite is detected as a resolved overdensity of stars during an ongoing search for new Local Group dwarf galaxy candidates in the UNIONS photometric dataset. It has a physical half-light radius of 26.9$^{+7.5}_{-5.4}$ pc, a $V$-band magnitude of $-$4.5 $\pm$ 0.4 mag, and resides at a heliocentric distance of approximately 100 kpc. We use Gaia DR3 astrometry to identify member stars, characterize the systemic proper motion, and confirm the reality of this faint stellar system. The brightest star in this system was followed up using Gemini GMOS-N long-slit spectroscopy and is measured to have a metallicity of [Fe/H] $=$ -2.85 $\pm$ 0.10 dex and a heliocentric radial velocity of $v_r$ = 5.1 $\pm$ 13.4 km s$^{-1}$. Bo\"otes V is larger (in terms of scale radius), more distant, and more metal-poor than the vast majority of globular clusters. It is likely that Bo\"otes V is an ultra-faint dwarf galaxy, though future spectroscopic studies will be necessary to definitively classify this object.

We carry out a search for tidal tails in a sample of open clusters with known relatively elongated morphology. We identify the member stars of these clusters from the precise astrometric and deep photometric data from $Gaia$ Early Data Release 3 using the robust membership determination algorithm, ML-MOC. We identify 46 open clusters having a stellar corona beyond the tidal radius, 20 of which exhibit extended tails aligned with the cluster orbit direction in galactocentric coordinates. Notably we find NGC 6940 (at a distance of $\sim1$ kpc) is the furthest open cluster exhibiting tidal tails that are $\sim50$ pc from its center, while also identifying $\sim40$ pc long tidal tails for the nearby Pleiades. Using the minimum spanning tree length for the most massive stars relative to all cluster members, we obtain the mass segregation ratio ($\rm\lambda_{MSR}$) profiles as a function of the number of massive stars in each cluster. From these profiles, we can classify the open clusters into four classes based on the degree of mass segregation experienced by the clusters. We find that clusters in the most mass segregated classes are the oldest on average and have the flattest mass function slope. Of the 46 open clusters studied in this work, 41 exhibit some degree of mass segregation. Furthermore, we estimate the initial masses (M$\rm_{i}$) of these open clusters finding that some of them, having M$\rm_{i}\gtrsim 10^{4} M_{\odot}$, could be the dissolving remnants of Young Massive Clusters.

In this paper, we have carried out a detailed study of the `Clocked' burster GS $1826-238$ using $\sim$ 90 ks broad-band (0.7 - 60.0 keV) data obtained with {\it AstroSat} observatory. The source was observed during a soft spectral state and traced a `banana' type track in the colour-colour diagram (CCD). We find that a combination of thermal component (multi-colour disc/bbodyrad) and Comptonized component is statistically good description for all the sections of the track in the CCD. The corona becomes optically thick ($\tau$ increases from $\sim$ 5 to 21) and cooler ($kT_e$ decreases from $\sim$ 4.8 to 2.2 keV) as the source moves up in the `banana' branch. Probably cooling is caused by increase in the supply of soft-seed photons from the disc/boundary-layer. Reflection signature is observed at upper `banana' branch of the source. Two type-I X-ray bursts are detected during the {\it AstroSat} observations. During the bursts, hard X-rays increased unlike previous observations where a reduction in hard X-rays is observed during the bursts. Decrease in the electron temperature and increase in the optical depth are observed during the bursts. The PSD (Power Spectral Density) of all the sections of the CCD can be represented by a pure power-law component. The strength of this component increases from $\sim$ 1\% to 4.5\% as the source moves up in the `banana' track. Search for burst oscillations gave a null result. We discuss the implications of our results in the context of previous findings.

Binary stars are recognized to be important in driving the dynamical evolution of stellar systems and also in determining some of their observational features. In this study, we explore the role that binary stars have in modulating the estimates of the velocity dispersion of stellar systems. To this aim, we developed a tool which allows to investigate the dependence of synthetic velocity dispersion on a number of crucial quantities characterizing the binary content: binary fraction and the distributions of their mass ratio, eccentricity and semi-major axis. As an application, we evaluate the impact that binary stars have on the estimation of the dynamical mass of dwarf spheroidal and ultra-faint dwarf galaxies, finding that it can be particularly relevant, especially for low mass and low density systems. These results bear profound implications for the interpretation of the measured velocity dispersion in such systems, since it weakens or relieves the claim for the need of large amounts of dark matter.

Precise control of the optical path differences (OPD) in the Very Large Telescope Interferometer (VLTI) was critical for the characterization of the black hole at the center of our Galaxy - leading to the 2020 Nobel prize in physics. There is now significant effort to push these OPD limits even further, in-particular achieving 100nm OPD RMS on the 8m unit telescopes (UT's) to allow higher contrast and sensitivity at the VLTI. This work calculated the theoretical atmospheric OPD limit of the VLTI as 5nm and 15nm RMS, with current levels around 200nm and 100nm RMS for the UT and 1.8m auxillary telescopes (AT's) respectively, when using bright targets in good atmospheric conditions. We find experimental evidence for the $f^{-17/3}$ power law theoretically predicted from the effect of telescope filtering in the case of the ATs which is not currently observed for the UT's. Fitting a series of vibrating mirrors modelled as dampened harmonic oscillators, we were able to model the UT OPD PSD of the gravity fringe tracker to $<1nm/\sqrt{Hz}$ RMSE up to 100Hz, which could adequately explain a hidden $f^{-17/3}$ power law on the UTs. Vibration frequencies in the range of 60-90Hz and also 40-50Hz were found to generally dominate the closed loop OPD residuals of Gravity. Cross correlating accelerometer with Gravity data, it was found that strong contributions in the 40-50Hz range are coming from the M1-M3 mirrors, while a significant portion of power from the 60-100Hz contributions are likely coming from between the M4-M10. From the vibrating mirror model it was shown that achieving sub 100nm OPD RMS for particular baselines (that have OPD$\sim$200nm RMS) required removing nearly all vibration sources below 100Hz.

Hydrodynamic waves propagate through stellar interiors, transporting energy and angular momentum. They can also advect fluid elements to produce mixing, but this effect has not been quantified from first principles. We derive the leading order non-linear wave mixing due to internal gravity waves in a thermally and compositionally-stratified fluid. We find that this scales as the fourth power of wave velocity, that it is suppressed by compositional stratification, and that it depends on the thermal and compositional diffusivities.

The bright blazar OJ~287 routinely parades high brightness bremsstrahlung flares which are explained as being a result of a secondary supermassive black hole (SMBH) impacting the accretion disk of a primary SMBH in a binary system. We begin by showing that these flares occur at times predicted by a simple analytical formula, based on the Kepler equation, which explains flares since 1888. The next impact flare, namely the flare number 26, is rather peculiar as it breaks the typical pattern of two impact flares per 12 year cycle. This will be the third bremsstrahlung flare of the current cycle that follows the already observed 2015 and 2019 impact flares from OJ~287. Unfortunately, astrophysical considerations make it difficult to predict the exact arrival epoch of the flare number 26. In the second part of the paper, we describe our recent OJ~287 observations. They show that the pre-flare light curve of flare number 22, observed in 2005, exhibits similar activity as the pre-flare light curve in 2022, preceding the expected flare number 26 in our model. We argue that the pre-flare activity most likely arises in the primary jet whose activity is modulated by the transit of the secondary SMBH through the accretion disk of the primary. Observing the next impact flare of OJ~287 in October 2022 will substantiate the theory of disk impacts in binary black hole systems.

We revisit the dynamical stability of hierarchical triple systems using direct $N$-body simulations. While there exist several proposals for the triple stability condition, our systematic and long-term numerical integrations reveal that the transition from unstable to stable triples is not abrupt, but rather gradual in general. Thus, the stability "boundary" cannot be defined in an unambiguous fashion, since it is sensitive to the choice of the assumed integration time, in particular for those triples with large mutual inclinations $i_\mathrm{mut}$ between the inner and outer orbits. We show, instead, the distribution of the disruption timescales of triples for different orbital configurations, with particular attention to their $i_\mathrm{mut}$ dependence. We find that a fraction of "unstable" triples remain bound for a long timescale in inclined triples, and thus the stability can be defined only when its disruption timescale is specified. The behavior of stable-unstable transition is very sensitive to the mutual inclination, and we discuss how the stability dependence on $i_\mathrm{mut}$ is explained in terms of the von Zeipel-Kozai-Lidov oscillations.

The overabundance of gas molecules in the coldest regions of space point to a non-thermal desorption process. Laboratory simulations show an efficient desorption of CO ice exposed to ultraviolet radiation, known as photodesorption, which decreases for increasing ice deposition temperature. However, the understanding of this abnormal phenomenon has remained elusive. In this work we show the same phenomenon, and in particular, a dramatic drop in the photodesorption yield is observed when the deposition temperature is 19 K and higher. Also the minimum ice thickness that accounts for a constant photodesorption yield of CO ice is deposition temperature dependent, an observation reported here for the first time. We propose that the key parameters that dominate the absorbed photon energy transfer in CO ice, and contribute to the measured photodesorption yields are the energy transfer length, single ice layer contributed desorption yield, and relative effective surface area. This set of parameters should be incorporated in astrophysical models that simulate photodesorption of the top CO-rich ice layer on icy dust populations with the size distribution which is ice thickness related.

The cosmic curvature $\Omega_{K,0}$, which determines the spatial geometry of the universe, is an important parameter in modern cosmology. Any deviation from $\Omega_{K,0}=0$ would have a profound impact on primordial inflation paradigm and fundamental physics. In this work, we adopt a model-independent method to test whether $\Omega_{K,0}$ deviates from zero. We use the Gaussian process to reconstruct the reduced Hubble parameter $E(z)$ and the derivative of distance $D'(z)$ from observational data, and then determine $\Omega_{K,0}$ with a null test relation. The cosmic chronometer (CC) Hubble data, baryon acoustic oscillation (BAO) Hubble data, and supernovae Pantheon sample are considered. Our result is consistent with a spatially flat universe within the domain of reconstruction $0<z<2.3$, at the $1\sigma$ confidence level. In the redshift interval $0<z<1$, the result favors a flat universe, while at $z>1$, it tends to favor a closed universe. In this sense, there is still a possibility for a closed universe. We also carry out the null test of the cosmic curvature at $0<z<4.5$ using the simulated gravitational wave standard sirens, CC+BAO and redshift drift Hubble data. The result shows that in the future, with the synergy of multiple high-quality observations, we can tightly constrain the spatial geometry or exclude the flat universe.

We report 1,656 new star clusters found in the Galactic disk (|b|<20 degrees) beyond 1.2 kpc, using Gaia EDR3 data. Based on an unsupervised machine learning algorithm, DBSCAN, and followed our previous studies, we utilized a unique method to do the data preparation and obtained the clustering coefficients, which proved to be an effective way to search blindly for star clusters. We tabulated the physical parameters and member stars of the new clusters, and presented some interesting examples, including a globular cluster candidate. The cluster parameters and member stars are available at CDS via anonymous ftp to https://cdsarc.cds.unistra.fr/ftp/vizier.submit//he22c. We examined the new discoveries and discussed their statistical properties. The proper motion dispersions and radii of the new clusters were the same as the previously reported ones. The new star clusters beyond 1.2 kpc were older than those in the solar neighborhood, and the new objects found in the third Galactic quadrant presented the lowest line-of-sight extinctions. Combined with our previous results, the total population of new clusters detected through our method was 2,541, corresponding to 55% of all newly published clusters in the Gaia era. The number of cataloged Gaia star clusters was also increased to nearly six thousand. In the near future, it is necessary to make a unified confirmation and member star determination for all reported clusters.

We present a new two-component dust geometry model, the \textit{Chocolate Chip Cookie} model, where the clumpy nebular regions are embedded in a diffuse stellar/ISM disk, like chocolate chips in a cookie. By approximating the binomial distribution of the clumpy nebular regions with a continuous Gaussian distribution and omitting the dust scattering effect, our model solves the dust attenuation process for both the emission lines and stellar continua via analytical approaches. Our Chocolate Chip Cookie model successfully fits the inclination dependence of both the effective dust reddening of the stellar components derived from stellar population synthesis and that of the emission lines characterized by the Balmer decrement for a large sample of Milky-Way like disk galaxies selected from the main galaxy sample of the Sloan Digital Sky Survey (SDSS). Our model shows that the clumpy nebular disk is about 0.55 times thinner and 1.6 times larger than the stellar disk for MW-like galaxies, whereas each clumpy region has a typical optical depth $\tau_{\rm{cl,V}} \sim 0.5$ in $V$ band. After considering the aperture effect, our model prediction on the inclination dependence of dust attenuation is also consistent with observations. Not only that, in our model, the dust attenuation curve of the stellar population naturally depends on inclination and its median case is consistent with the classical Calzetti law. Since the modelling constraints are from the optical wavelengths, our model is unaffected by the optically thick dust component, which however could bias the model's prediction of the infrared emissions.

The inner-most region of the Seyfert galaxy NGC 2992 has long been suspected to be the location of intense AGN-host galaxy interaction, but photon pile-up in previous high-resolution observations hampered the study of soft X-ray excess and the interaction near its nucleus. We present an X-ray imaging spectroscopic analysis of the circumnuclear ($1^{\prime\prime}$--$3^{\prime\prime}$) region of NGC 2992 using the zeroth-order image of a 135 ks grating observation obtained with Chandra, which captured the nucleus in a historically low flux state. Extended soft X-ray emission is detected in the circumnuclear region with observed luminosity $L_{\rm X} \sim 7 \times 10^{39}\rm\ erg\ s^{-1}$. The majority of previously puzzling detection of soft excess could be associated with the outflow, indicated by the morphological correspondences between soft X-ray emission and figure-eight-shaped radio bubbles. An anomalous narrow emission line with the centroid energy $\sim4.97$ keV is found. If attributed to redshifted highly ionized iron emission (e.g., Fe xxv), the required outflow velocity is $\sim0.23\,c$. An alternative explanation is that this line emission could be produced by the nuclear spallation of iron. We also find asymmetric extended Fe K$\alpha$ emission along the galactic disk, which could originate from reflection by cold gas on $\sim 200$ pc scale.

Many stars across all classes possess strong enough magnetic fields to influence dynamical flow of material off the stellar surface. For the case of massive stars (O and B types), about 10\% of them harbour strong, globally ordered (mostly dipolar) magnetic fields. The trapping and channeling of their stellar winds in closed magnetic loops leads to {\it magnetically confined wind shocks} (MCWS), with pre-shock flow speeds that are some fraction of the wind terminal speed that can be a few thousand km s$^{-1}$. These shocks generate hot plasma, a source of X-rays. In the last decade, several developments took place, notably the determination of the hot plasma properties for a large sample of objects using \xmm\ and \ch, as well as fully self-consistent MHD modelling and the identification of shock retreat effects in weak winds. In addition, these objects are often sources of H$\alpha$ emission which is controlled by either sufficiently high mass loss rate or centrifugal breakout. Here we review the theoretical aspects of such magnetic massive star wind dynamics.

The epoch of reionization probes the state of our universe when the very first stars formed and ionized the hydrogen atoms in the surrounding medium. Since the epoch has not yet been probed observationally, it is often called the "final frontier" of observational cosmology. This final frontier is attracting a lot of attention because of the availability of a large number of telescopes in a wide variety of wavebands. This review article summarizes some of the concepts required to understand the interesting physics of reionization and how to analyze the high-redshift universe using related observations.

We test the hypothesis of starburst galaxies as sources of ultra-high energy cosmic rays and high-energy neutrinos. The computation of interactions of ultra-high energy cosmic rays in the starburst environment as well as in the propagation to the Earth is made using a modified version of the Monte Carlo code {\it SimProp}, where hadronic processes in the environment of sources are implemented for the first time. Taking into account a star-formation-rate distribution of sources, the fluxes of ultra-high energy cosmic rays and high-energy neutrinos are computed and compared with observations, and the explored parameter space for the source characteristics is discussed. We find that, depending on the density of the gas in the source environment, spallation reactions could exceed theoutcome in neutrinos from photo-hadronic interactions in the source environment and in the extra-galactic space.

This paper presents a model to unify the diverse range of magnetar activity, through the building and release of elastic stress from the crust. A cellular automaton drives both local and global yielding of the crust, leading to braiding of coronal loops and energy release. The model behaves like a real magnetar in many ways: giant flares and small bursts both occur, as well as periods of quiescence whose typical duration is either $\lesssim 1$ yr or $\sim 10-30$ yr. The burst energy distribution broadly follows an earthquake-like power law over the energy range $10^{40}-10^{45}\,{\rm erg}$. The local nature of coronal loops allows for the possibility of high-energy and fast radio bursts from the same magnetar. Within this paradigm, magnetar observations can be used to constrain the poorly-understood mechanical properties of the neutron-star crust.

Our main aim is to test the non-variability of the radial velocity (RV) of a sample of 2351 standard stars used for wavelength calibration of the RVS instrument onboard Gaia. In this paper, we present the spectroscopic analysis of these stars with the determination of their physical parameters by matching observed and synthetic spectra. We estimate the offset between different instruments after determining the shift between measured and archived RVs since the instrument pipelines use various numerical masks. Through the confirmation of the stability of the target RVs, we find 68 stars with a long-term variation having an acceleration which exceeds $10 \,\rm{m\, s^{-1}yr^{-1}}$. This suggests a barycentric reflex motion caused by a companion. As activity phenomena may be the source of periodic and trend-like RV variations in stars with putative planetary companions, we analysed various activity indicators in order to check their correlations to the RV changes. Among the trend stars, 18 have a trend model scatter greater than $100 \,\rm{m\, s^{-1}}$ over a time span from 10 to 12 years. We also confirm that six stars with known substellar companions have a total model scatter, $3\sigma$, exceeding the threshold set by Gaia, that is, $300 \,\rm{m\, s^{-1}}$. In addition, TYC8963-01543-1 an SB2 star has data scatter $\sigma = 176.6\, \rm{m\, s^{-1}}$. Four more other stars are revealed to be variable after combining data from different instruments. Despite the presence of low-amplitude changes, a very large fraction of our sample (98.8\%) appears suitable as RV calibrators for Gaia RVS.

The cold dark matter (CDM) structure formation scenario faces challenges on (sub)galactic scales, central among them being the `cusp-core' problem. A known remedy, driving CDM out of galactic centres, invokes interactions with baryons, through fluctuations in the gravitational potential arising from feedback or orbiting clumps of gas or stars. Here we interpret core formation in a hydrodynamic simulation in terms of a theoretical formulation, which may be considered a generalisation of Chandrasekhar's theory of two body relaxation to the case when the density fluctuations do not arise from white noise; it presents a simple characterisation of the effects of complex hydrodynamics and `subgrid physics'. The power spectrum of gaseous fluctuations is found to follow a power law over a range of scales, appropriate for a fully turbulent compressible medium. The potential fluctuations leading to core formation are nearly normally distributed, which allows for the energy transfer leading to core formation to be described as a standard diffusion process, initially increasing the velocity dispersion of test particles as in Chandrasekhar's theory. We calculate the energy transfer from the fluctuating gas to the halo and find it consistent with theoretical expectations. We also examine how the initial kinetic energy input to halo particles is redistributed to form a core. The temporal mass decrease inside the forming core may be fit by an exponential form; a simple prescription based on our model associates the characteristic timescale with an energy relaxation time. We compare the resulting theoretical density distribution with that in the simulation.

Context. Stellar tidal streams are the result of tidal interactions between a central galaxy and lower mass systems like satellite galaxies or globular clusters. For the Local Group, many diffuse substructures have been identified and their link to the galaxy evolution has been traced. However it cannot be assumed that the Milky Way or M31 are representative of their galaxy class, and a larger sample of analogue galaxies beyond the Local Group is required to be able to generalise the underlying theory. Aims. We want to characterise photometrically the stellar streams around Milky Way analogues in the local Universe with the goal to deepen our understanding of the interaction between host and satellite galaxies, and ultimately of the galaxy formation and evolution processes. Methods. In the present work we identified and analysed stellar tidal streams around Milky Way analogue galaxies from the SAGA sample, using deep images of the DESI Legacy Imaging Surveys (for this sample, we obtain a range of r-band surface brightness limit between 27.8 and 29 mag / arcsec2). We measure the surface brightness and colours of the detected streams using GNU Astronomy Utilities software. Results. We identified 16 new stellar tidal streams around Milky Way analogue galaxies at distances between 25 and 40 Mpc. Applying statistical analysis to our findings for the SAGA II galaxy sample, we obtained a frequency of 12.2% +/- 2.4% for stellar streams. We measured surface brightness and colours of the detected streams, and the comparison to the dwarf satellite galaxies population around galaxies belonging to the same SAGA sample shows that the mean colour of the streams is 0.20 mag redder than that of the SAGA satellites; also, the streams are, in average, 0.057 +/- 0.021 mag redder that their progenitor, for those cases when a likely progenitor could be identified.

The mechanism(s) driving the early- and late-time accelerated expansion of the Universe represent one of the most compelling mysteries in fundamental physics today. The path to understanding the causes of early- and late-time acceleration depends on fully leveraging ongoing surveys, developing and demonstrating new technologies, and constructing and operating new instruments. This report presents a multi-faceted vision for the cosmic survey program in the 2030s and beyond that derives from these considerations. Cosmic surveys address a wide range of fundamental physics questions, and are thus a unique and powerful component of the HEP experimental portfolio.

Cosmological models and their corresponding parameters are widely debated because of the current discrepancy between the results of the Hubble constant, $H_{0}$, obtained by SNe Ia, and the Planck data from the Cosmic Microwave Background Radiation. Thus, considering high redshift probes like Gamma-Ray Bursts (GRBs) is a necessary step. However, using GRB correlations between their physical features to infer cosmological parameters is difficult because GRB luminosities span several orders of magnitude. In our work, we use a 3-dimensional relation between the peak prompt luminosity, the rest-frame time at the end of the X-ray plateau, and its corresponding luminosity in X-rays: the so-called 3D Dainotti fundamental plane relation. We correct this relation by considering the selection and evolutionary effects with a reliable statistical method, obtaining a lower central value for the intrinsic scatter, $\sigma_{int}=0.18 \pm 0.07$ (47.1 \%) compared to previous results, when we adopt a particular set of GRBs with well-defined morphological features, called the platinum sample. We have used the GRB fundamental plane relation alone with both Gaussian and uniform priors on cosmological parameters and in combination with SNe Ia and BAO measurements to infer cosmological parameters like $H_{0}$, the matter density in the universe ($\Omega_{M}$), and the dark energy parameter $w$ for a $w$CDM model. Our results are consistent with the parameters given by the $\Lambda$CDM model but with the advantage of using cosmological probes detected up to $z=5$, much larger than the one observed for the furthest SNe Ia.

Small-scale dynamos play important roles in modern astrophysics, especially on Galactic and extragalactic scales. Owing to dynamo action, purely hydrodynamic Kolmogorov turbulence hardly exists and is often replaced by hydromagnetic turbulence. Understanding the size of dissipative magnetic structures is important in estimating the time scale of Galactic scintillation and other observational and theoretical aspects of interstellar and intergalactic small-scale dynamos. Here we show that the thickness of magnetic flux tubes decreases more rapidly with increasing magnetic Prandtl number than previously expected. Also the theoretical scale based on the dynamo growth rate and the magnetic diffusivity decrease faster than expected. However, the scale based on the cutoff of the magnetic energy spectra scales as expected for large magnetic Prandtl numbers, but continues in the same way also for moderately small values - contrary to what is expected. For a critical magnetic Prandtl number of about 0.27, the dissipative and resistive cutoffs are found to occur at the same wavenumber. For large magnetic Prandtl numbers, our simulations show that the peak of the magnetic energy spectrum occurs at a wavenumber that is twice as large as previously predicted.

The power spectrum of cosmic microwave background lensing is a powerful tool for constraining fundamental physics such as the sum of neutrino masses and the dark energy equation of state. Current lensing measurements primarily come from distortions to the microwave background temperature field, but the polarization lensing signal will dominate upcoming experiments with greater sensitivity. Cosmic birefringence refers to the rotation of the linear polarization direction of microwave photons propagating from the last scattering surface to us, which can be induced by parity-violating physics such as axion-like dark matter or primordial magnetic fields. We find that, for an upcoming CMB-S4-like experiment, if there exists the scale-invariant anisotropic birefringence with an amplitude corresponding to the current $95\%$ upper bound, the measured lensing power spectrum could be biased by up to a factor of few at small scales, $L\gtrsim 1000$. We show that the bias scales linearly with the amplitude of the scale-invariant birefringence spectrum. The signal-to-noise of the contribution from anisotropic birefringence is larger than unity even if the birefringence amplitude decreases to $\sim 5\%$ of the current upper bound. Our results indicate that a measurement and characterization of the anisotropic birefringence is important for lensing analysis in future low-noise polarization experiments.

Measurements of the stellar coronal magnetic field are of great importance in understanding the stellar magnetic activity, yet the measurements have been extremely difficult. Recent studies proposed a new method of magnetic field measurements based on the magnetic-field-induced-transition (MIT) of the Fe~{\sc{x}} ion. Here we construct a series of stellar coronal magnetohydrodynamics (MHD) models and synthesize several Fe~{\sc{x}} emission lines at extreme-ultraviolet wavelengths, and then diagnose the magnetic field strength at the bases of the coronae using the MIT technique. Our results show that the technique can be applied to some stars with magnetic fields more than three times higher than that of the Sun at solar maximum. Furthermore, we investigate the uncertainty of the derived magnetic field strength caused by photon counting error and find that a signal-noise ratio of $\sim$50 for the Fe~{\sc{x}} 175 {\AA}~line is required to achieve effective measurements of the stellar coronal magnetic field.

We present results from nine simulations that compare the standard $\Lambda$ Cold Dark Matter cosmology ($\Lambda$CDM) with counterfactual universes, for approximately $100\,{\rm Gyr}$ using the Enzo simulation code. We vary the value of $\Lambda$ and the fluctuation amplitude to explore the effect on the evolution of the halo mass function (HMF), the intergalactic medium (IGM) and the star formation history (SFH). The distinct peak in star formation rate density (SFRD) and its subsequent decline are both affected by the interplay between gravitational attraction and the accelerating effects of $\Lambda$. The IGM cools down more rapidly in models with a larger $\Lambda$ and also with a lower $\sigma_8$, reflecting the reduced SFRD associated with these changes -- although changing $\sigma_8$ is not degenerate with changing $\Lambda$, either regarding the thermal history of the IGM or the SFH. However, these induced changes to the IGM or ionizing background have little impact on the calculated SFRD. We provide fits for the evolution of the SFRD in these different universes, which we integrate over time to derive an asymptotic star formation efficiency. Together with Weinberg's uniform prior on $\Lambda$, the estimated probability of observers experiencing a value of $\Lambda$ no greater than the observed value is 13%, substantially larger than some alternative estimates. Within the Enzo model framework, then, observer selection within a multiverse is able to account statistically for the small value of the cosmological constant, although $\Lambda$ in our universe does appear to be at the low end of the predicted range.

The next generation of Extremely Large Telescope (24 to 39m diameter) will suffer from the so-called "pupil fragmentation" problem. Due to their pupil shape complexity (segmentation, large spiders ...), some differential pistons may appear between some isolated part of the full pupil during the observations. Although classical AO system will be able to correct for turbulence effects, they will be blind to this specific telescope induced perturbations. Hence, such differential piston, a.k.a petal modes, will prevent to reach the diffraction limit of the telescope and ultimately will represent the main limitation of AO-assisted observation with an ELT. In this work we analyse the spatial structure of these petal modes and how it affects the ability of a Pyramid Wavefront sensor to sense them. Then we propose a variation around the classical Pyramid concept for increasing the WFS sensitivity to this particular modes. Nevertheless, We show that one single WFS can not accurately and simultaneously measure turbulence and petal modes. We propose a double path wavefront sensor scheme to solve this problem. We show that such a scheme,associated to a spatial filtering of residual turbulence in the second WFS path dedicated to petal mode sensing, allows to fully measure and correct for both turbulence and fragmentation effects and will eventually restore the full capability and spatial resolution of the future ELT.

The equation of state (EoS) that describes extremely dense matter under strong interactions is not completely understood. One reason is that the first-principle calculations of the EoS at finite chemical potential are challenging in nuclear physics. However, neutron star observables like masses, radii, moment of inertia and tidal deformability are direct probes to the EoS and hence make the EoS reconstruction task feasible. In this work, we present results from a novel deep learning technique that optimizes a parameterized equation of state in the automatic differentiation framework. We predict stellar structures from a pre-trained Tolman-Oppenheimer-Volkoff (TOV) solver network, given an EoS represented by neural networks. The latest observational data of neutron stars, specifically their masses and radii, are used to implement the chi-square fitting. We optimize the parameters of the neural network EoS by minimizing the error between observations and predictions. The well-trained neural network EoS gives an estimate of the relationship between the pressure and the mass density. The results presented are consistent with those from conventional approaches and the experimental bound on the tidal deformability inferred from the gravitational wave event, GW170817.

Primordial black holes (PBHs), as a potential macroscopic candidate for dark matter, can encounter other compact objects in dark matter halos because of their random distribution. Besides, the detection of gravitational waves (GWs) related to the stellar-mass black hole-neutron star (BH-NS) mergers raises the possibility that the BHs involved in such events may have a primordial origin. In this work, we calculate the merger rate of PBH-NS binaries within the framework of ellipsoidal-collapse dark matter halo models and compare it with the corresponding results derived from spherical-collapse dark matter halo models. Our results exhibit that ellipsoidal-collapse dark matter halo models can potentially amplify the merger rate of PBH-NS binaries in such a way that it is very close to the range estimated by the LIGO-Virgo observations. While spherical-collapse dark matter halo models cannot justify PBH-NS merger events as consistent results with the latest GW data reported by the LIGO-Virgo collaboration. In addition, we calculate the merger rate of PBH-NS binaries as a function of PBH mass and fraction within the context of ellipsoidal-collapse dark matter halo models. The results indicate that PBH-NS merger events with the mass of $(M_{PBH}\le 5 M_{\odot}, M_{NS}\simeq 1.4 M_{\odot})$ will be consistent with the LIGO-Virgo observations if $f_{PBH}\simeq 1$. We also show that to have at least on $(M_{PBH}\simeq 5 M_{\odot}, M_{NS}\simeq 1.4 M_{\odot})$ event in the comoving volume $1 Gpc^{3}$ annually, ellipsoidal-collapse dark matter halo models constrain the abundance of PBHs as $f_{PBH} \geq 0.1$.

The last two decades have seen a major expansion in the availability, size, and precision of time-domain datasets in astronomy. Owing to their unique combination of flexibility, mathematical simplicity and comparative robustness, Gaussian Processes (GPs) have emerged recently as the solution of choice to model stochastic signals in such datasets. In this review we provide a brief introduction to the emergence of GPs in astronomy, present the underlying mathematical theory, and give practical advice considering the key modelling choices involved in GP regression. We then review applications of GPs to time-domain datasets in the astrophysical literature so far, from exoplanets to active galactic nuclei, showcasing the power and flexibility of the method. We provide worked examples using simulated data, with links to the source code, discuss the problem of computational cost and scalability, and give a snapshot of the current ecosystem of open source GP software packages. Driven by further algorithmic and conceptual advances, we expect that GPs will continue to be an important tool for robust and interpretable time domain astronomy for many years to come.

In the earliest phases of their evolution, stars gain mass through the acquisition of matter from their birth clouds. The widely accepted classical concept of early stellar evolution neglects the details of this accretion phase and assumes the formation of stars with large initial radii that contract gravitationally. In this picture, the common idea is that once the stars begin their fusion processes, they have forgotten their past. By analysing stellar oscillations in recently born stars, we show that the accretion history leaves a potentially detectable imprint on the stars' interior structures. Currently available data from space would allow discriminating between these more realistic accretion scenarios and the classical early stellar evolution models. This opens a window to investigate the interior structures of young pulsating stars that will also be of relevance for related fields, such as stellar oscillations in general and exoplanet studies.

The X-ray spectrum of Mkn 478 is known to be dominated by a strong soft excess which can be described using relativistic blurred reflection. Using observations from {\it XMM-Newton}, {\it AstroSat} and {\it Swift}, we show that for the long-term ($\sim$ years) and intermediate-term (days to months) variability, the reflection fraction is anti-correlated with the flux and spectral index, which implies that the variability is due to the hard X-ray producing corona moving closer to and further from the black hole. Using flux-resolved spectroscopy of the {\it XMM-Newton} data, we show that the reflection fraction has the same behaviour with flux and index on short time-scales of hours. The results indicate that both the long-term and short-term variability of the source is determined by the same physical mechanism of strong gravitational light bending causing enhanced reflection and low flux as the corona moves closer to the black hole.

The current theory predicts that hot subdwarf binaries are produced from evolved low-mass binaries that have undergone mass transfer and drastic mass loss during either a common envelope phase or a stable Roche lobe overflow while on the red giant branch (RGB). We perform a spectroscopic survey to find binary systems that include low-mass red giants near the tip of the RGB, which are predicted to be the direct progenitors of subdwarf B (sdB) stars. We aim to obtain a homogeneous sample to search for the observational evidence of correlations between the key parameters governing the formation of sdB stars and constrain the physics of stable mass transfer. In this work, we concentrated on the southern hemisphere targets and conducted a spectroscopic survey of 88 red giant stars to search for the long-period RGB + MS binary systems within 200\,pc. Combining radial velocity (RV) measurements from ground-based observations with CORALIE and RV measurements from $Gaia$ DR2 and early data release 3 (eDR3) as well as the astrometric excess noise and RUWE measurements from $Gaia$ DR3, we defined a robust binary classification method. In addition, we searched for known binary systems in the literature and in the $Gaia$ DR3. We select a total of 211 RGB candidates in the southern hemisphere within 200\,pc based on the $Gaia$ DR2 color-magnitude diagram. Among them, a total of 33 red giants were reported as binary systems with orbital periods between 100 and 900 days, some of which are expected to be the direct progenitors of wide binary sdB stars. In addition, we classified 37 new MS\,+\,RGB binary candidates, whose orbital parameters will be measured with future spectroscopic follow-up.

Galaxy surveys provide one of the best ways to constrain the theory of gravity at cosmological scales. They can be used to constrain the two gravitational potentials encoding time, $\Psi$, and spatial, $\Phi$, distortions, which are exactly equal at late time within General Relativity. Hence, any small variation leading to a non-zero anisotropic stress, i.e. a difference between these potentials, would be an indication for modified gravity. Current analyses usually consider gravitational lensing and redshift-space distortions to constrain the anisotropic stress, but these rely on certain assumptions like the validity of the weak equivalence principle, and a specific time evolution of the functions encoding deviations from General Relativity. In this work, we propose a reparametrization of the gravitational lensing observable, together with the use of the relativistic dipole of the correlation function of galaxies to directly measure the anisotropic stress with a minimum amount of assumptions. We consider the future Legacy Survey of Space and Time of the Vera C. Observatory and the future Square Kilometer Array, and show that combining gravitational lensing and gravitational redshift with the proposed approach we will achieve model-independent constraints on the anisotropic stress at the level of $\sim 20\,\%$.

Local measurements of the Hubble constant ($H_0$) based on Cepheids e Type Ia supernova differ by $\approx 5 \sigma$ from the estimated value of $H_0$ from Planck CMB observations under $\Lambda$CDM assumptions. In order to better understand this $H_0$ tension, the comparison of different methods of analysis will be fundamental to interpret the data sets provided by the next generation of surveys. In this paper, we deploy machine learning algorithms to measure the $H_0$ through a regression analysis on synthetic data of the expansion rate assuming different values of redshift and different levels of uncertainty. We compare the performance of different algorithms as Extra-Trees, Artificial Neural Network, Extreme Gradient Boosting, Support Vector Machines, and we find that the Support Vector Machine exhibits the best performance in terms of bias-variance tradeoff, showing itself a competitive cross-check to non-supervised regression methods such as Gaussian Processes.

In the Letter, interesting evidence is reported to support a central tidal disruption event (TDE) in the known AGN NGC 1097. Considering the motivations of TDE as one probable origination of emission materials of double-peaked broad emission lines and also as one probable explanation to changing-look AGN, it is interesting to check whether are there clues to support a TDE in NGC 1097, not only a changing-look AGN but also an AGN with double-peaked broad emission lines. Under the assumption that the onset of broad H$\alpha$ emission was due to a TDE, the 13years-long (1991-2004) variability of double-peaked broad H$\alpha$ line flux in NGC 1097 can be well predicted by theoretical TDE model, with a $(1-1.5){\rm M_\odot}$ main-sequence star tidally disrupted by the central BH with TDE model determined mass about $(5-8)\times10^7{\rm M_\odot}$. The results provide interesting evidence to not only support TDE-related origin of double-peaked broad line emission materials but also support TDE as an accepted physical explanation to physical properties of changing-look AGN.

In this paper, we present TESS photometry and high-resolution spectra of the short-period Algol EW Boo. We obtained double-lined radial velocities (RVs) from the time-series spectra and measured the effective temperature of the primary star as $T_{\rm{eff,1}}$ = 8560 $\pm$ 118 K. For the orbital period study, we collected all times of minima available for over the last 30 years. It was found that the eclipse timing variation of the system could be represented by a periodic oscillation of 17.6 $\pm$ 0.3 years with a semi-amplitude of 0.0041 $\pm$ 0.0001 d. The orbital and physical parameters were derived by simultaneously analyzing the TESS light and RV curves using the Wilson-Devinney (WD) binary star modeling code. The component masses and radii were showed over 3% precision: $M_{1}$ = 2.67 $\pm $ 0.08 M$_{\odot}$, $M_{2}$ = 0.43 $\pm $ 0.01 M$_{\odot}$, $R_{1}$ = 2.01 $\pm $ 0.02 R$_{\odot}$, and $R_{2}$ = 1.35 $\pm $ 0.01 R$_{\odot}$. Furthermore, multiple frequency analyses were performed for the light-curve residuals from the WD model. As a result, we detected 17 pressure-mode pulsations in the region of 40.15 - 52.37 d$^{-1}$. The absolute dimensions and pulsation characteristics showed that the $\delta$ Sct pulsator was the more massive and hotter primary star of the EW Boo.

The COS Legacy Archive Spectroscopic SurveY (CLASSY) HST/COS treasury program provides the first high-resolution spectral catalogue of 45 local high-z analogues in the UV (1200-2000{\AA}) to investigate their stellar and gas properties. We present a toolkit of UV interstellar medium (ISM) diagnostics, analyzing the main emission lines of CLASSY spectra (i.e., NIV]{\lambda}{\lambda}1483,87, CIV{\lambda}{\lambda}1548,51, HeII{\lambda}1640, OIII]{\lambda}{\lambda}1661,6, SiIII]{\lambda}{\lambda}1883,92, CIII]{\lambda}{\lambda}1907,9). Specifically, we focus our investigation on providing accurate diagnostics for reddening, electron density and temperature, gas-phase metallicity and ionization parameter, taking into account the different ionization zones of the ISM. We calibrate our UV toolkit using well-known optical diagnostics, analyzing archival optical spectra for all the CLASSY targets. We find that UV density diagnostics estimate ne values that are ~1-2 dex higher (e.g., ne(CIII]{\lambda}{\lambda}1907,9)~10^4cm^{-3}) than those inferred from their optical counterparts (e.g., ne([SII]{\lambda}{\lambda}6717,31)~10^2cm^{-3}). Te derived from the hybrid ratio OIII]{\lambda}1666/[OIII]{\lambda}5007 proves to be a reliable Te diagnostic, with differences in 12+log(O/H) within ~+/-0.3dex. We also investigate the relation between the stellar and gas E(B-V), finding consistent values at high specific star formation rates, while at low sSFR we confirm an excess of dust attenuation in the gas. Finally, we investigate UV line ratios and equivalent widths to provide correlations with 12+log(O/H) and log(U), but note there are degeneracies between the two. With this suite of UV-based diagnostics, we illustrate the pivotal role CLASSY plays in understanding the chemical and physical properties of high-z systems that JWST can observe in the rest-frame UV.

We analyzed the minor axis spectra of the elliptical planetary nebula (PN) NGC 7009 observed with the Keck HIRES with a 0.862$"$ $\times$ 10$"$ slit placed at about $\sim$7.5$"$ and 10$"$ away from the center and a 0.862$"$ $\times$ 14$"$ slit at the center. The mean densities derived from the integrated [SII] 6716/6731\r{A}, fluxes along the Keck HIRES slit length indicate a density range of 10$^{3.7}$ to 10$^{4.1}$ cm$^{-3}$, while the local densities derived from the slit spectral images show a large local density variation of about 10$^{2.8}$ - 10$^{4.6}$ cm$^{-3}$: local densities vary substantially more than values integrated over the line of sight. The expansion rates of the main and outer shells obtained by [SII] are about 21.7 and 30.0 kms$^{-1}$, respectively. The kinematic results of the [SII] spectral lines correspond to the outermost regions of the two shells and are not representative of the whole PN but are closely related to the other emission lines observed in the shell gas. We conclude that the density contrast leads to the formation of the inner shell, while the change in ionization state leads to the formation of the outer shell. We suggest that the inner main and outer shells result from two successive major ejections. The physical conditions of the central star must have been different when these shells first formed.

The observed excess radio background has remained a puzzle for over a decade. A recent new physics solution involves dark matter that decays into dark photons in the presence of a thermal dark photon background. The produced non-thermal dark photon spectrum then converts into standard photons around the reionization era, yielding an approximate power-law radio excess with brightness temperature $T(\nu)\simeq \nu^{-2.5}$ over a wide range of frequencies, $\nu$. This simple power-law model comes intriguingly close to the current data, even if several ingredients are required to make it work. In this paper, we investigate some of the details of this model, showcasing the importance of individual effects. In particular, significant deviation from a power law are present at $\nu\lesssim 100\,{\rm MHz}$ and $\nu\gtrsim 1\,{\rm GHz}$. These effects result in improving the fit to data compared to a power-law spectrum, and may become testable in future observations. We also highlight independent signatures that can be tested with future CMB spectral distortion experiments such as {\it PIXIE}.

Cold dark matter haloes are expected to be triaxial, and so appear elliptical in projection. We use weak gravitational lensing from the Canada-France Imaging Survey (CFIS) component of the Ultraviolet-Near Infrared Optical Northern Survey (UNIONS) to measure the ellipticity of the dark matter haloes around Luminous Red Galaxies (LRGs) from the Sloan Digital Sky Survey Data Release 7 (DR7) and from the CMASS and LOWZ samples of the Baryon Oscillation Spectroscopic Survey (BOSS), assuming their major axes are aligned with the stellar light. We find that DR7 LRGs with masses $M \sim 2.5\times10^{13} \textrm{M}_{\odot}/h$ have halo ellipticities $e=0.35\pm0.09$. Expressed as a fraction of the galaxy ellipticity, we find $f_h = 1.4\pm0.4$. For BOSS LRGs, the detection is of marginal significance: $e = 0.17\pm0.10$ and $f_h=0.1\pm0.4$. These results are in agreement with other measurements of halo ellipticity from weak lensing and, taken together with previous results, suggest an increase of halo ellipticity of $0.10\pm0.05$ per decade in halo mass. This trend agrees with the predictions from hydrodynamical simulations, which find that at higher halo masses, not only do dark matter haloes become more elliptical, but that the misalignment between major axis of the stellar light in the central galaxy and that of the dark matter decreases.

We report the first look at extragalactic Cepheid variables with the James Webb Space Telescope, obtained from a serendipitous (to this purpose) observation of NGC 1365, host of an SN Ia (SN 2012fr), a calibration path used to measure the Hubble constant. As expected, the high-resolution observations with NIRCam through F200W show better source separation from line-of-sight companions than HST images at similar near-infrared wavelengths, the spectral region that has been used to mitigate the impact of host dust on distance measurements. Using the standard star P330E as a zeropoint and PSF reference, we photometered 31 previously-known Cepheids in the JWST field, spanning 1.15 < log P < 1.75 including 24 Cepheids in the longer period interval of 1.35 < log P < 1.75. We compared the resultant Period-Luminosity relations to that of 49 Cepheids in the full period range including 38 in the longer period range observed with WFC3/IR on HST and transformed to the JWST photometric system (F200W, Vega). The P-L relations measured with the two space telescopes are in good agreement, with intercepts (at log P=1) of 25.74+/-0.04 and 25.72+\-0.05 for HST and JWST, respectively. Our baseline result comes from the longer period range where the Cepheids have higher signal-to-noise ratios where we find 25.75+\-0.05 and 25.75+\-0.06 mag for HST and JWST, respectively. We find good consistency between this first JWST measurement and HST, and no evidence that HST Cepheid photometry is "biased bright" at the ~0.2 mag level that would be needed to mitigate the Hubble Tension, though comparisons from more SN hosts are warranted and anticipated. We expect future JWST observations to surpass these in quality as they will be optimized for measuring Cepheids.

SPECULOOS is a ground-based transit survey consisting of six identical 1-m robotic telescopes. The immediate goal of the project is to detect temperate terrestrial planets transiting nearby ultracool dwarfs (late M-dwarf stars and brown dwarfs), which could be amenable for atmospheric research with the next generation of telescopes. Here, we report the developments of the northern counterpart of the project - SPECULOOS Northern Observatory, and present its performance during the first three years of operations from mid-2019 to mid-2022. Currently, the observatory consists of one telescope, which is named Artemis. The Artemis telescope demonstrates remarkable photometric precision, allowing it to be ready to detect new transiting terrestrial exoplanets around ultracool dwarfs. Over the period of the first three years after the installation, we observed 96 objects from the SPECULOOS target list for 6000 hours with a typical photometric precision of $0.5\%$, and reaching a precision of $0.2\%$ for relatively bright non-variable targets with a typical exposure time of 25 sec. Our weather downtime (clouds, high wind speed, high humidity, precipitation and/or high concentration of dust particles in the air) over the period of three years was 30% of overall night time. Our actual downtime is 40% because of additional time loss associated with technical problems.

Centaur 29P/Schwassmann-Wachmann 1 (SW1) is a highly active object orbiting in the transitional Gateway region (Sarid et al. 2019) between the Centaur and Jupiter Family Comet regions. SW1 is unique among the Centaurs in that it experiences quasi-regular major outbursts and produces CO emission continuously; however, the source of the CO is unclear. We argue that due to its very large size (approx. 32 km radius), SW1 is likely still responding, via amorphous water ice (AWI) conversion to crystalline water ice (CWI), to the rapid change in its external thermal environment produced by its dynamical migration from the Kuiper belt to the Gateway Region at the inner edge of the Centaur region at 6 au. It is this conversion process that is the source of the abundant CO and dust released from the object during its quiescent and outburst phases. If correct, these arguments have a number of important predictions testable via remote sensing and in situ spacecraft characterization, including: the quick release on Myr timescales of CO from AWI conversion for any few km-scale scattered disk KBO transiting into the inner system; that to date SW1 has only converted between 50 to 65% of its nuclear AWI to CWI; that volume changes upon AWI conversion could have caused subsidence and cave-ins, but not significant mass wasting or crater loss on SW1; that SW1s coma should contain abundant amounts of CWI CO2-rich icy dust particles; and that when SW1 transits into the inner system within the next 10,000 years, it will be a very different kind of JFC comet.

Red giants are unstable to radial pulsation. About a third of them also show a long secondary period, 5 to 10 times the pulsation period. The long secondary periods were recently ascribed to eclipses of the red giant by a low-mass dust-enshrouded companion. Long secondary periods have been known for over a century. In this paper, I use primarily American Association of Variable Star Observers visual and photoelectric observations to look for evidence of long secondary periods in 103 red giant stars listed by Nancy Houk in 1963 as having long secondary periods, based mostly on photographic photometry. I have determined long secondary periods in 37 stars, and upper limits (some of them not very stringent) in 25. In the former, the ratio of long secondary period to pulsation period peaks strongly at 10, which suggests that most of the stars are pulsating in the first overtone. The loong secondary periods are consistent with those o0f Houk in 33 of the 37 stars. I have identified 16 stars as bimodal pulsaters;their period ratios are consistent with previous observational and theoretical results. For 14 stars,the periods in the General Catalogue of Variable Stars are incorrect or absent.

We investigate the dependency with scale of the empirical probability distribution functions (PDF) of Elsasser increments using large sets of WIND data (collected between 1995 and 2017) near 1 au. The empirical PDF are compared to the ones obtained from high-resolution numerical simulations of steadily driven, homogeneous Reduced MHD turbulence on a $2048^3$ rectangular mesh. A large statistical sample of Alfv\'enic increments is obtained by using conditional analysis based on the solar wind average properties. The PDF tails obtained from observations and numerical simulations are found to have exponential behavior in the inertial range, with an exponential decrement that satisfies power-laws of the form $\alpha_l\propto l^{-\mu}$, where $l$ the scale size, with $\mu$ around 0.2 for observations and 0.4 for simulations. PDF tails were extrapolated assuming their exponential behavior extends to arbitrarily large increments in order to determine structure function scaling laws at very high orders. Our results points to potentially universal scaling laws governing the PDF of Elsasser increments and to an alternative methodology to investigate high-order statistics in solar wind observations.

Throughout the last decades, Zeeman-Doppler Imaging (ZDI) has been intensively used to reconstruct large-scale magnetic topologies of active stars from time series of circularly polarized (Stokes $V$) profiles. ZDI being based on the assumption that the topology to be reconstructed is constant with time (apart from being sheared by differential rotation), it fails at describing stellar magnetic fields that evolve on timescales similar to the observing period. We present a new approach, called TIMeS (for Time-dependent Imaging of Magnetic Stars), to derive the time-dependent large-scale magnetic topologies of active stars, from time series of high-resolution Stokes $V$ spectra. This new method uses the combined concepts of sparse approximation and Gaussian process regression to derive the simplest time-dependent magnetic topology consistent with the data. Assuming a linear relation between the Stokes $V$ data and the reconstructed magnetic image, TIMeS is currently applicable to cases in which the magnetic field is not too strong (with an upper limit depending on $v\sin{i}$). We applied TIMeS to several simulated data sets to investigate its ability to retrieve the poloidal and toroidal components of large-scale magnetic topologies. We find that the proposed method works best in conditions similar to those needed for ZDI, reconstructing reliable topologies with minor discrepancies at very low latitudes whose contribution to the data is small. We however note that TIMeS can fail at reconstructing the input topology when the field evolves on a timescale much shorter than the stellar rotation cycle

Photophoretic forces could levitate thin 10 centimeter-scale structures in Earth$'$s stratosphere indefinitely. We develop models of the thermal transpiration lofting force on a bilayer sandwich structure under stratospheric conditions driven by radiative fluxes in the thermal-infrared and solar-band. Similar structures have been levitated in the laboratory. Lofting is maximized when the layers are separated by an air gap equal to the mean free path (MFP), when about half of the layers$'$ surface area consists of holes with radii < MFP, and when the top layer is solar-transmissive and infrared-emissive while the bottom layer is solar-absorptive and infrared-transmissive. We describe a preliminary design of a 10 cm diameter device that combines a levitating structure made of two membranes 2 $\mu$m apart with the support structure required for stiffness and orientation control. We limit the design to components that could be fabricated with available methods. Structural analysis suggests that the device would have sufficient strength to withstand forces that might be encountered in transport, deployment, and flight. Our models predict a payload capacity of about 300 mg at 25 km altitude and our analysis suggests it could support bidirectional radio communication at over 10 Mb/s and could have limited navigational abilities. Such devices could be useful for atmospheric science or telecommunications, and similar devices might be useful on Mars. Structures a few times larger might have payloads of a few grams.

We use a catalogue of stellar binaries with wide separations (up to 1 pc) identified by the Gaia satellite to constrain the presence of extended substructure within the Milky Way galaxy. Heating of the binaries through repeated encounters with substructure results in a characteristic distribution of binary separations, allowing constraints to be placed independent of the formation mechanism of wide binaries. Across a wide range of subhalo density profiles, we show that subhalos with masses $\gtrsim 65 \ M_\odot$ and characteristic length scales similar to the separation of these wide binaries cannot make up 100% of the Galaxy's dark matter. Constraints weaken for subhalos with larger length scales and are dependent on their density profiles. For such large subhalos, higher central densities lead to stronger constraints. Subhalos with density profiles similar to those expected from cold dark matter must be at least $\sim 5,000$ times denser than predicted by simulation to be constrained by the wide binary catalogue.

Cosmological and astrophysical observations currently provide the the only robust, positive evidence for dark matter. Cosmic probes of dark matter, which seek to determine the fundamental properties of dark matter through observations of the cosmos, have emerged as a promising means to reveal the nature of dark matter. This report summarizes the current status and future potential of cosmic probes to inform our understanding of the fundamental nature of dark matter in the coming decade.

The scotogenic model is the Standard Model (SM) with Z_2 symmetry and the addition of Z_2 odd right-handed Majorana neutrinos and SU(2)_L doublet scalar fields. We have extended the original scotogenic model by an additional Z_2 odd singlet scalar field that plays a role in dark matter. In our model, the asymmetries of the lepton and Z_2 odd doublet scalar are simultaneously produced through CP-violating right-handed neutrino decays. While the former is converted into baryon asymmetry through the sphaleron process, the latter is relaid to the DM density through the decay of SU(2)_L doublet scalar that is named "asymmetric mediator". In this way, we provide an extended scotogenic model that predicts the energy densities of baryon and dark matter being in the same order of magnitude, and also explains the low-energy neutrino masses and mixing angles.

This report summarizes the envisioned research activities as gathered from the Snowmass 2021 CF5 working group concerning Dark Energy and Cosmic Acceleration: Cosmic Dawn and Before. The scientific goals are to study inflation and to search for new physics through precision measurements of relic radiation from the early universe. The envisioned research activities for this decade (2025-35) are constructing and operating major facilities and developing critical enabling capabilities. The major facilities for this decade are the CMB-S4 project, a new Stage-V spectroscopic survey facility, and existing gravitational wave observatories. Enabling capabilities include aligning and investing in theory, computation and model building, and investing in new technologies needed for early universe studies in the following decade (2035+).

We present novel realizations of E- and T-model inflation within Supergravity which are largely associated with the existence of a pole of order one and two respectively in the kinetic term of the inflaton superfield. This pole arises due to the selected logarithmic Kahler potentials K, which parameterize hyperbolic manifolds with scalar curvature related to the coefficient (-N)<0 of a logarithmic term. The associated superpotential W exhibits the same R charge with the inflaton-accompanying superfield and includes all the allowed terms. The role of the inflaton can be played by a gauge singlet or non-singlet superfield. Models with one logarithmic term in K for the inflaton, require N=2, some tuning -- of the order of 10^-5 -- between the terms of W and predict a tensor-to-scalar ratio r at the level of 0.001. The tuning can be totally eluded for more structured K's, with N values increasing with r and spectral index close or even equal to its present central observational value.

In this work we consider the effect of an $R^2$ term on the kinetic misalignment axion theory. By using the slow-roll assumptions during inflation and the field equations, we construct an autonomous dynamical system for the kinetic axion, including the effects of the $R^2$ term and we solve numerically the dynamical system. As we demonstrate, the pure kinetic axion attractor is transposed to the right in the field phase space, and it is no longer $(\phi,\dot{\phi})=(\langle \phi \rangle,0)$, but it is $(\phi,\dot{\phi})=(\langle \phi '\rangle,0)$, with $\langle \phi '\rangle\neq 0$ some non-zero value of the scalar field with $\langle \phi '\rangle> \langle \phi \rangle$. This feature indicates that the kinetic axion mechanism is enhanced, and the axion oscillations are further delayed, compared with the pure kinetic axion case. The phenomenological implications on the duration of the inflationary era, on the commencing of the reheating era and the reheating temperature, are also discussed.

The Holographic Space-time (HST) model of inflation has a potential explanation for dark matter as tiny primordial black holes. Motivated by a recent paper of Barrau\cite{barrau} we propose a version of this model where some of the Inflationary Black Holes (IBHs), whose decay gives rise to the Hot Big Bang, carry the smallest value of a discrete symmetry charge. The fraction $f$ of IBHs carrying this charge is difficult to estimate from first principles, but we fix it by requiring that the crossover between radiation and matter domination occurs at the correct temperature $T_{eq} \sim 1 eV = 10^{-28} M_P$. The fraction is small, $f \sim 2\times 10^{-9}$ so we believe this gives an extremely plausible model of dark matter.

We have computed the deflection angles caused by 195 objects in the solar system, including 177 satellites and eight asteroids. Twenty-one satellites and six asteroids can bend light from distant compact extragalactic sources by more than 0.1 $\mu$as, and fourteen satellites and the asteroid Ceres can deflect light by more than 1.0 $\mu$as. We calculated the zones and durations of perturbations posed by the gravitational fields of five planets (excluding Earth, Jupiter, and Saturn), Pluto, and Ceres, where the perturbations would affect astrometry measured with the Squared Kilometre Array (SKA). Perturbed zones with deflection angles larger than 0.1 and 1.0 $\mu$as appear as ribbons. Their widths range from dozens of degrees for Uranus, Neptune, and Venus to several degrees or less for other objects at 0.1 $\mu$as, and from $\sim$ 16$^{\circ}$ for Venus to several degrees or less for other objects at 1.0 $\mu$as. From the calculated perturbation durations, the influence of the gravitational fields of selected objects can be divided into four levels: hardly affect SKA astrometry (I), may have little effect (II), may have a great effect (III) on single-epoch astrometry, and may greatly affect both single- and multi-epoch astrometry (IV). The objects corresponding to these levels are Ceres (I), Pluto (II), Mercury and Mars (III), and other objects (IV).

We study the structural properties like the gravitational mass, radius and tidal deformability of dark matter (DM) admixed strange quark stars (SQSs). For the purpose we consider the vector MIT Bag model to describe the strange quark matter (SQM) and investigate the possible presence of accreted DM in the SQSs consequently forming DM admixed SQSs. We introduce feeble interaction between SQM and the accreted fermionic DM via a vector dark boson mediator. Considering the present literature, in the context of possible presence of DM in SQSs, this work is the first to consider interaction between DM and SQM in the DM admixed SQSs. The mass of the DM fermion ($m_{\chi}$) and the vector mediator ($m_{\xi}$) and the coupling ($y_{\xi}$) between them are determined in accordance with the constraint from Bullet cluster and the present day relic abundance, respectively. We find that the presence of DM reduces both the mass and radius of the star compared to the no-DM case. The massive the DM fermion, the lower the values of maximum mass and radius of the DM admixed SQSs. For the chosen values of $m_{\chi}$ and corresponding values of $m_{\xi}$ and $y_{\xi}$, the computed structural properties of the DM admixed SQSs satisfy all the various present day astrophysical constraints.We obtain massive DM admixed SQSs configurations consistent with the GW190814 observational data. Hence the secondary compact object associated with this event may be a DM admixed SQS.

This article discusses a number of incorrect statements appearing in textbooks on data analysis, machine learning, or computational methods; the common theme in all these cases is the relevance and application of statistics to the study of scientific or engineering data; these mistakes are also quite prevalent in the research literature. Crucially, we do not address errors made by an individual author, focusing instead on mistakes that are widespread in the introductory literature. After some background on frequentist and Bayesian linear regression, we turn to our six paradigmatic cases, providing in each instance a specific example of the textbook mistake, pointers to the specialist literature where the topic is handled properly, along with a correction that summarizes the salient points. The mistakes (and corrections) are broadly relevant to any technical setting where statistical techniques are used to draw practical conclusions, ranging from topics introduced in an elementary course on experimental measurements all the way to more involved approaches to regression.

The extraction of the nuclear matter properties from neutron star observations is nowadays an important issue, in particular, the properties that characterize the symmetry energy which are essential to describe correctly asymmetric nuclear matter. We use deep neural networks (DNN) to map the relation between cold $\beta$-equilibrium neutron star matter and the nuclear matter properties. Assuming a quadratic dependence on the isospin asymmetry for the energy per particle of homogeneous nuclear matter and using a Taylor expansion up to fourth order in the iso-scalar and iso-vector contributions, we generate a dataset of different realizations of $\beta$-equilibrium NS matter and the corresponding nuclear matter properties. The DNN model was successfully trained, attaining great accuracy in the test set. Finally, a real case scenario was used to test the DNN model, where a set of 33 nuclear models, obtained within a relativistic mean field approach or a Skyrme force description, were fed into the DNN model and the corresponding nuclear matter parameters recovered with considerable accuracy, in particular, the standard deviations $\sigma(L_{\text{sym}})= 12.85$ MeV and $\sigma(K_{\text{sat}})= 41.02$ MeV were obtained, respectively, for the slope of the symmetry energy and the nuclear matter incompressibility at saturation.

Recent work, using an effective field theory framework, has shown the number of possible couplings between nucleons and the dark-matter-candidate Weakly Interacting Massive Particles (WIMPs) is larger than previously thought. Inspired by an existing Mathematica script that computes the target response, we have developed a fast, modern Fortran code, including optional OpenMP parallelization, along with a user-friendly Python wrapper, to swiftly and efficiently explore many scenarios, with output aligned with practices of current dark matter searches. A library of most of the important target nuclides is included; users may also import their own nuclear structure data, in the form of reduced one-body density matrices. The main output is the differential event rate as a function of recoil energy, needed for modeling detector response rates, but intermediate results such as nuclear form factors can be readily accessed.

Liquid xenon and liquid argon detectors are leading the direct dark matter search and are expected to be the candidate technology for the forthcoming generation of ultra-sensitive large-mass detectors. At present, the scintillation light detection in those experiments is based on ultra-pure low-noise photo-multipliers. To overcome the issues in terms of the extreme radio-purity, costs, and technological feasibility of the future dark matter experiments, the novel SiPM-based photo-detector modules look promising candidates, capable of replacing the present light detection technology. However, the intrinsic features of SiPMs may limit the present expectations. In particular, interfering phenomena, especially related to the optical correlated noise, can degrade the energy and pulse shape resolutions. As a consequence, the projected sensitivity of the future detectors has to be reconsidered accordingly.