Papers for Friday, Aug 06 2021

Spiral galaxies have distinct internal structures including a stellar bulge, disk and spiral arms. It is unknown when in cosmic history these structures formed. We analyze observations of BRI 1335-0417, an intensely star-forming galaxy in the distant Universe, at redshift 4.41. The [C II] gas kinematics show a steep velocity rise near the galaxy center and have a two-armed spiral morphology that extends from about 2 to 5 kiloparsecs in radius. We interpret these features as due to a central compact structure, such as a bulge, a rotating gas disk and either spiral arms or tidal tails. These features had been formed within 1.4 billion years after the Big Bang, long before the peak of cosmic star formation.

Velocity fields can be reconstructed at cosmological scales from their influence on the correlation between the cosmic microwave background and large-scale structure. Effects that induce such correlations include the kinetic Sunyaev Zel'dovich (kSZ) effect and the moving-lens effect, both of which will be measured to high precision with upcoming cosmology experiments. Galaxy measurements also provide a window into measuring velocities from the effect of redshift-space distortions (RSDs). The information that can be accessed from the kSZ or RSDs, however, is limited by astrophysical uncertainties and systematic effects, which may significantly reduce our ability to constrain cosmological parameters such as $f\sigma_8$. In this paper, we show how the large-scale transverse-velocity field, which can be reconstructed from measurements of the moving-lens effect, can be used to measure $f\sigma_8$ to high precision.

Stellar streams are the inevitable end product of star cluster evolution, with the properties of a given stream being related to its progenitor. We consider how the dynamical history of a progenitor cluster, as traced by the evolution of its stellar mass function, is reflected in the resultant stream. We generate model streams by evolving star clusters with a range of initial half-mass relaxation times and dissolution times via direct N-body simulations. Stellar streams that dissolve quickly show no variation in the stellar mass function along the stream. Variation is, however, observed along streams with progenitor clusters that dissolve after several relaxation times. The mass function at the edges of a stream is approximately primordial as it is populated by the first stars to escape the cluster before segregation occurs. Moving inwards the mass function steepens as the intermediate parts of the stream consist of mostly low-mass stars that escaped the cluster after some segregation has occurred. The centre of the stream is then marked by a flatter mass function, as the region is dominated by high-mass stars that quickly segregated to the progenitor cluster's centre and were the last stars to become unbound. We further find that the maximum slope of the mass function along the stream and the rate at which it decreases with distance from the dissolved progenitor serve as proxies for the dynamical state reached by the progenitor cluster before dissolution; this may be able to be applied to observed streams with near-future observations.

Large surveys are providing a diversity of spectroscopic observations with Gaia alone set to deliver millions of Ca-triplet-region spectra across the Galaxy. We aim to understand the dimensionality of the chemical abundance information in the Gaia-RVS data to inform galactic archaeology pursuits. We fit a quadratic model of four primary sources of variability, described by labels of $T_{\rm eff}$, $\log g$, [Fe/H], and [$\alpha$/Fe], to the normalized flux of 10,802 red-clump stars from the Gaia-RVS-like ARGOS survey. We examine the residuals between ARGOS spectra and the models and find that the models capture the flux variability across $85\%$ of the wavelength region. The remaining residual variance is concentrated to the Ca-triplet features, at an amplitude up to $12\%$ of the normalized flux. We use principal component analysis on the residuals and find orthogonal correlations in the Ca-triplet core and wings. This variability, not captured by our model, presumably marks departures from the completeness of the 1D-LTE label description. To test the indication of low-dimensionality, we turn to abundance-space to infer how well we can predict measured [Si/H], [O/H], [Ca/H], [Ni/H], and [Al/H] abundances from the Gaia-RVS-like RAVE survey with models of $T_{\rm eff}$, $\log g$, [Fe/H], and [Mg/Fe]. We find that we can near-entirely predict these abundances. Using high-precision APOGEE abundances, we determine that a measurement uncertainty of $<$ 0.03 dex is required to capture additional information from these elements. This indicates that a four-label model sufficiently describes chemical abundance variance for $\approx$ S/N $<$ 200 per pixel, in Gaia-RVS spectra.

Upcoming missions such as Euclid and the Nancy Grace Roman Space Telescope (Roman) will use emission-line selected galaxies to address a variety of questions in cosmology and galaxy evolution in the $z>1$ universe. The optimal observing strategy for these programs relies upon knowing the number of galaxies that will be found and the bias of the galaxy population. Here we measure the $\rm{[O\ III]}\ \lambda 5007$ luminosity function for a vetted sample of 1951 $m_{\rm J+JH+H} < 26$ galaxies with unambiguous redshifts between $1.90 < z < 2.35$, which were selected using HST/WFC3 G141 grism frames made available by the 3D-HST program. These systems are directly analogous to the galaxies that will be identified by the Euclid and Roman missions, which will utilize grism spectroscopy to find $\rm{[O\ III]}\ \lambda 5007$-emitting galaxies at $0.8 \lesssim z \lesssim 2.7$ and $1.7 \lesssim z \lesssim 2.8$, respectively. We interpret our results in the context of the expected number counts for these upcoming missions. Finally, we combine our dust-corrected $\rm{[O\ III]}$ luminosities with rest-frame ultraviolet star formation rates to present the first estimate of the SFR density associated with $1.90 < z < 2.35$ $\rm{[O\ III]}$-emitting galaxies. We find that these grism-selected galaxies contain roughly half of the total star formation activity at $z\sim2$.

Extreme high synchrotron peaked blazars (EHBLs) are amongst the most powerful accelerators found in nature. Usually the synchrotron peak frequency of an EHBL is above $10^{17}\,$Hz, i.e., lies in the range of medium to hard X-rays making them ideal sources to study particle acceleration and radiative processes. EHBL objects are commonly observed at energies beyond several TeV, making them also powerful probes of gamma-ray absorption in the intergalactic medium. During the last decade, several attempts have been made to increase the number of EHBL detected at TeV energies and probe their spectral characteristics. Here we report new detections of EHBLs in the TeV energy regime, each at a redshift of less than 0.2, by the High Energy Stereoscopic System (H.E.S.S.). Also, we report on X-ray observations of these EHBLs candidates with Swift XRT. In conjunction with the very high energy observations, this allows us to probe the radiation mechanisms and the underlying particle acceleration processes.

We report upper-limits on the Epoch of Reionization (EoR) 21 cm power spectrum at redshifts 7.9 and 10.4 with 18 nights of data ($\sim36$ hours of integration) from Phase I of the Hydrogen Epoch of Reionization Array (HERA). The Phase I data show evidence for systematics that can be largely suppressed with systematic models down to a dynamic range of $\sim10^9$ with respect to the peak foreground power. This yields a 95% confidence upper limit on the 21 cm power spectrum of $\Delta^2_{21} \le (30.76)^2\ {\rm mK}^2$ at $k=0.192\ h\ {\rm Mpc}^{-1}$ at $z=7.9$, and also $\Delta^2_{21} \le (95.74)^2\ {\rm mK}^2$ at $k=0.256\ h\ {\rm Mpc}^{-1}$ at $z=10.4$. At $z=7.9$, these limits are the most sensitive to-date by over an order of magnitude. While we find evidence for residual systematics at low line-of-sight Fourier $k_\parallel$ modes, at high $k_\parallel$ modes we find our data to be largely consistent with thermal noise, an indicator that the system could benefit from deeper integrations. The observed systematics could be due to radio frequency interference, cable sub-reflections, or residual instrumental cross-coupling, and warrant further study. This analysis emphasizes algorithms that have minimal inherent signal loss, although we do perform a careful accounting in a companion paper of the small forms of loss or bias associated with the pipeline. Overall, these results are a promising first step in the development of a tuned, instrument-specific analysis pipeline for HERA, particularly as Phase II construction is completed en route to reaching the full sensitivity of the experiment.

The Solar Orbiter mission, with an orbit outside the Sun Earth line and leaving the ecliptic plane, opens up opportunities for the combined analysis of measurements obtained by solar imagers and spectrometers. For the first time, different space spectrometers will be located at wide angles to each other, allowing three-dimensional (3D) spectroscopy of the solar atmosphere. The aim of this work is to prepare the methodology to facilitate the reconstruction of 3D vector velocities from two stereoscopic LOS Doppler velocity measurements using the Spectral Imaging of the Coronal Environment (SPICE) onboard the Solar Orbiter and the near-Earth spectrometers, while widely separated in space. We develop the methodology using the libraries designed earlier for the STEREO mission but applied to spectroscopic data from the Hinode mission and the Solar Dynamics Observatory. We use well-known methods of static and dynamic solar rotation stereoscopy and the methods of EUV stereoscopic triangulation for optically thin coronal EUV plasma emissions. We develop new algorithms using analytical geometry in space to determine the 3D velocity in coronal loops. We demonstrate our approach with the reconstruction of 3D velocity vectors in plasma flows along "open" and "closed" magnetic loops. This technique will be applied to an actual situation of two spacecraft at different separations with spectrometers onboard (SPICE versus the Interface Region Imaging Spectrograph (IRIS) and Hinode imaging spectrometer) during the Solar Orbiternominal phase. We summarise how these observations can be coordinated.

We present here, follow-up observations of four Binary black hole BBH events performed with the High Energy Stereoscopic System (H.E.S.S.) in the Very High Energy (VHE) gamma-ray domain during the second and third LIGO/Virgo observation runs. Detailed analyses of the obtained data did not show significant VHE emission. We derive integral upper limit maps considering a generic $E^{-2}$ source spectrum in the most sensitive H.E.S.S energy interval ranging from 1 to 10 TeV. We also consider Extragalactic Background Light absorption effects and derive integral upper limits over the full accessible energy range. We finally derive upper limits of the VHE luminosity for each event and compare them with the expected VHE emission from GRBs. These comparisons allow us to assess the H.E.S.S. gravitational wave follow-up strategies. For the fourth GW observing run O4, we do not expect to fundamentally alter our observing strategy, and will continue to prioritize sky coverage like for the previous runs

The community commonly assumes that the Venusian atmosphere lacks organic (reduced) carbon. This is reflected in the literature, which now for almost a half a century does not mention organic carbon in connection with the Venus atmosphere. This assumption persists despite the failure of models that exclude organic carbon to account for many well-established observed features of the Venusian atmosphere. Here is presented a model summarizing reactions that almost certainly are occurring in the Venusian atmosphere. The model relies on reactions of reduced carbon compounds known to occur in concentrated sulfuric acid (CSA), under high pressure and high temperature, many used in industrial processes. Inclusion of this known chemistry into a model for the Venus atmosphere accounts for several as yet unexplained observations. These include the upper haze, the lower haze, and the "mysterious" UV-blue absorber. This article also suggests, as a historical perspective, that a long-forgotten dispute is responsible for the persistent assumption of absence of interesting organic chemistry in the clouds of Venus.

Galaxy clusters in a dark matter simulation are matched to nodes in several different cosmic webs found via Disperse. These webs are created by varying simulation smoothing and Disperse persistence. A few methods are used for Disperse node-cluster matching. There are usually many more Disperse nodes than clusters and more than one cluster can match the same Disperse node. For most matching methods and smoothing 2.5 Mpc/h or less, about 3/4 of the clusters always have a corresponding Disperse node. The nearest clusters and Disperse nodes within twice the smoothing length of each other obey a cluster mass-Disperse node density relation. Disperse node matched clusters can also be assigned Disperse filaments based upon their corresponding Disperse nodes, only about 1/10 of such cluster pairs frequently have filaments amongst the different Disperse webs. The average density profile along a line connecting cluster pairs separated by < 60 Mpc/h is enhanced, with more (on average)counts and mass enhancement for pairs assigned filaments via Disperse nodes. Clusters often lacking matched Disperse nodes have different trends in their local shear, and perhaps histories, compared to the majority of clusters. It might be interesting to see in what other ways, e.g., observational properties, these clusters differ. The approach here also lends itself to comparing nodes across many cosmic web constructions, using the fixed underlying cluster distribution to make a correspondence.

$\epsilon$~Eridani is a young planetary system hosting a complex multi-belt debris disk and a confirmed Jupiter-like planet orbiting at 3.48 AU from its host star. Its age and architecture are thus reminiscent of the early Solar System. The most recent study of Mawet et al. 2019, which combined radial velocity (RV) data and Ms-band direct imaging upper limits, started to constrain the planet's orbital parameters and mass, but are still affected by large error bars and degeneracies. Here we make use of the most recent data compilation from three different techniques to further refine $\epsilon$~Eridani~b's properties: RVs, absolute astrometry measurements from the Hipparcos~and Gaia~missions, and new Keck/NIRC2 Ms-band vortex coronagraph images. We combine this data in a Bayesian framework. We find a new mass, $M_b$ = $0.66_{-0.09}^{+0.12}$~M$_{Jup}$, and inclination, $i$ = $77.95_{-21.06}^{\circ+28.50}$, with at least a factor 2 improvement over previous uncertainties. We also report updated constraints on the longitude of the ascending node, the argument of the periastron, and the time of periastron passage. With these updated parameters, we can better predict the position of the planet at any past and future epoch, which can greatly help define the strategy and planning of future observations and with subsequent data analysis. In particular, these results can assist the search for a direct detection with JWST and the Nancy Grace Roman Space Telescope's coronagraph instrument (CGI).

We report the detection, for the first time in space, of a new non-functionalised hydrocarbon cycle in the direction of TMC-1: o-C6H4 (ortho-benzyne). We derive a column density for this hydrocarbon cycle of (5 +/- 1)e11 cm-2. The abundance of this species is around 30 times lower than that of cyclopentadiene and indene. We compare the abundance of benzyne with that of other pure hydrocarbons, cycles or chains, and find that it could be formed from neutral-radical reactions such as C2H + CH2CHCCH and C + C5H5, and possibly through C4H + C2H4, C3H + CH2CCH2, and C3H2 + C3H3. Hence, the rich content of hydrocarbon cycles observed in TMC-1 could arise through a bottom-up scenario involving reactions of a few radicals with the abundant hydrocarbons recently revealed by the QUIJOTE line survey.

We present results from long-term timing of 72 pulsars discovered by the Arecibo PALFA survey, including precise determination of astrometric and spin parameters, and flux density and scatter broadening measurements at 1.4 GHz. Notable discoveries include two young pulsars (characteristic ages $\sim$30 kyr) with no apparent supernova remnant associations, three mode changing, 13 nulling and two intermittent pulsars. We detected eight glitches in five pulsars. One of these, PSR~J1954+2529, is old (characteristic age $\sim$1 Gyr), and likely belongs to a newly-emerging class of binary pulsars. It is the only pulsar among the 72 that appears to be not isolated: a non-recycled neutron star with a 931 ms spin period in an eccentric ($e = 0.114$) wide ($P_b = 82.7 $d) orbit with a companion of undetermined nature having a minimum mass of $0.61 M_{\odot}$. Since operations at Arecibo ceased in 2020 August, we give a final tally of PALFA sky coverage, and compare its 207 pulsar discoveries to the known population. On average, they are 50% more distant than other Galactic plane radio pulsars; PALFA millisecond pulsars (MSP) have twice the dispersion measure per unit spin period than the known population of MSP in the Plane. The four intermittent pulsars discovered by PALFA more than double the population of such objects, which should help to improve our understanding of pulsar magnetosphere physics. The statistics for these, RRATS, and nulling pulsars suggest that there are many more of these objects in the Galaxy than was previously thought.

We present trigonometric parallax and proper motion measurements for two T-type brown dwarfs. We derive our measurements from infrared laser guide star adaptive optics observations spanning five years from the ShaneAO/SHARCS and NIRC2/medium-cam instruments on the Shane and Keck telescopes, respectively. To improve our astrometric precision, we measure and apply a distortion correction to our fields for both instruments. We also transform the Keck and ShaneAO astrometric reference frames onto the ICRS using five-parameter parallax and proper motion solutions for background reference stars from Gaia DR2. Fitting for parallax and proper motion, we measure parallaxes of $73.5\pm9.2$ mas and $70.1\pm6.7$ mas for WISEJ19010703+47181688 (WISE1901) and WISEJ21543294+59421370 (WISE2154), respectively. We utilize Monte Carlo methods to estimate the error in our sparse field methods, taking into account overfitting and differential atmospheric refraction. Comparing to previous measurements in the literature, all of our parallax and proper motion values fall within $2\sigma$ of the published measurements, and 4 of 6 measurements are within $1\sigma$. These data are among the first parallax measurements of these T dwarfs and serve as precise measurements for calibrating stellar formation models. These two objects are the first results of an ongoing survey of T dwarfs with Keck/NIRC2 and the Shane Adaptive Optics system at Lick Observatory.

We characterize the ionized gas outflows in 15 low-redshift star-forming galaxies, a Valpara\'iso ALMA Line Emission Survey (VALES) subsample, using MUSE integral field spectroscopy and GAMA photometric broadband data. We measure the emission-line spectra by fitting a double-component profile, with the second and broader component being related to the outflowing gas. This interpretation is in agreement with the correlation between the observed star-formation rate surface density ($\Sigma_{\mathrm{SFR}}$) and the second-component velocity dispersion ($\sigma_{\mathrm{2nd}}$), expected when tracing the feedback component. By modelling the broadband spectra with spectra energy distribution (SED) fitting and obtaining the star-formation histories of the sample, we observe a small decrease in SFR between 100 and 10 Myr in galaxies when the outflow H$\alpha$ luminosity contribution is increased, indicating that the feedback somewhat inhibits the star formation within these timescales. The observed emission-line ratios are best reproduced by photoionization models when compared to shock-ionization, indicating that radiation from young stellar population is dominant, and seems to be a consequence of a continuous star-formation activity instead of a bursty event. The outflow properties such as mass outflow rate ($\sim 0.1\,$M$_\odot$ yr$^{-1}$), outflow kinetic power ($\sim 5.2 \times 10^{-4}\% L_{\mathrm{bol}}$) and mass loading factor ($\sim 0.12$) point towards a scenario where the measured feedback is not strong and has a low impact on the evolution of galaxies in general.

We investigate the galaxy bispectrum induced by the nonlinear gravitational evolution as a possible probe to constrain degenerate higher-order scalar tensor (DHOST) theories. We find that the signal obtained from the leading kernel of second-order density fluctuations is partially hidden by the uncertainty in the nonlinear galaxy bias, and that the kernel of second-order velocity fields instead provides unbiased information on the modification of gravity theory. Based on this fact, we propose new phenomenological time-dependent functions, written as a combination of the coefficients of the second-order kernels, which is expected to trace the higher-order growth history. We then present approximate expressions for these variables in terms of parameters that characterize the DHOST theories. We also show that the resultant formulae provides new constraints on the parameter space of the DHOST theories.

A 2.5D numerical model of magnetoacoustic-Alfv\'en linear mode conversions in the partially ionised low solar atmosphere induced by the Hall effect is surveyed, varying magnetic field strength and inclination, and wave frequency and horizontal wave number. It is found that only the magnetic component of wave energy is subject to Hall-mediated conversions to Alfv\'en wave-energy via a process of polarisation rotation. This strongly boosts direct mode conversion between slow magneto\-acoustic and Alfv\'en waves in the quiet low chromosphere, even at mHz frequencies. However, fast waves there, which are predominantly acoustic in nature, are only subject to Hall- induced conversion via an indirect two-step process: (i) a geometry-induced fast-slow transformation near the Alfv\'en-acoustic equipartition height $z_{\rm eq}$; and (ii) Hall-rotation of the fast wave in $z>z_{\rm eq}$. Thus, for the two-stage process to yield upgoing Alfv\'en waves, $z_{\rm eq}$ must lie below or within the Hall-effective window $0\lesssim z\lesssim700$ km. Magnetic field strengths over 100 G are required to achieve this. Since the potency of this Hall effect varies inversely with the field strength but directly with the wave frequency, only frequencies above about 100 mHz are significantly affected by the two-stage process. Increasing magnetic field inclination $\theta$ generally strengthens the Hall convertibility, but the horizontal wavenumber $k_x$ has little effect. The direct and indirect Hall mechanisms both have implications for the ability of MHD waves excited at the photosphere to reach the upper chromosphere, and by implication the corona.

We present the first sample of TDEs discovered during the SRG all-sky survey. These 13 events were selected among X-ray transients detected on the 0<l<180 hemisphere by eROSITA during its second scan of the sky (10 June-14 Dec. 2020) and confirmed as TDEs by our optical follow-up observations. The most distant event occurred at z=0.581. One TDE continued to brighten after its discovery for at least another 6 months. The X-ray spectra can be described by emission from a standard accretion disk with kT between 0.05 and 0.5 keV, consistent with near-critical accretion onto black holes of a few 10^3 to 10^8 Msun, although super-critical accretion is possibly taking place. In 2 TDEs, a spectral hardening is observed 6 months after the discovery, possibly indicating the formation of an accretion disk corona. 4 TDEs show an optical brightening concurring with or preceding the X-ray outburst. All 13 TDEs are optically faint, with Lg/Lx<0.1 in most cases, where Lg and Lx are the intrinsic g-band and 0.2-6 keV luminosities, respectively. This sample is thus drastically different from TDEs selected at optical wavelengths. We have constructed a TDE X-ray luminosity function in the 10^42.5-10^45 erg/s range. The TDE volume rate decreases with increasing X-ray luminosity approximately as a power law with alpha=-0.6+/-0.2. This is similar to a trend observed for optically selected TDEs. The total rate at z<0.6 is (1.1+/-0.5)10^-5 TDEs/galaxy/year, an order of magnitude lower than previously estimated from optical studies. This might indicate that X-ray bright events constitute a minority of all TDEs, which would provide support to models predicting a strong dependence on the viewing angle. Our current TDE detection threshold can be lowered by a factor of ~2, which should make it possible to find ~700 TDEs by the end of the SRG survey over the entire sky.

Star formation is known to occur more readily where more raw materials are available. This is often expressed by a 'Kennicutt-Schmidt' relation where the surface density of Young Stellar Objects (YSOs) is proportional to column density to some power, $\mu$. The aim of this work was to determine if column density alone is sufficient to explain the locations of Class 0/I YSOs within Serpens South, Serpens Core, Ophiuchus, NGC1333 and IC348, or if there is clumping or avoidance that would point to additional influences on the star formation. Using the O-ring test as a summary statistic, 95 per cent confidence envelopes were produced for different values of $\mu$ from probability models made using the Herschel column density maps. The YSOs were tested against four distribution models: the best-estimate of $\mu$ for the region, $\mu=0$ above a minimum column density threshold and zero probability elsewhere, $\mu=1$, and the power-law that best represents the five regions as a collective, $\mu=2.05 \pm 0.20$. Results showed that $\mu=2.05$ model was consistent with the majority of regions and, for those regions, the spatial distribution of YSOs at a given column density is consistent with being random. Serpens South and NGC1333 rejected the $\mu = 2.05$ model on small scales of $\sim 0.15 \mathrm{pc}$ which implies that small-scale interactions may be necessary to improve the model. On scales above 0.15 pc, the positions of YSOs in all five regions can be well described using column density alone.

Blazars are a sub-category of radio-loud active galactic nuclei with relativistic jets pointing towards the observer. They exhibit non-thermal variable emission, which practically extends over the whole electromagnetic spectrum. Despite the plethora of multi-wavelength observations, the origin of the emission in blazar jets remains an open question. In this work, we construct a two-zone leptonic model: particles accelerate in a small region and lose energy through synchrotron radiation and inverse Compton Scattering. Consequently, the relativistic electrons escape to a larger area where the ambient photon field, which is related to Accretion Disk MHD Winds, could play a central role in the gamma-ray emission. This model explains the Blazar Sequence and the broader properties of blazars, as determined by Fermi observations, by varying only one parameter, the mass accretion rate onto the central black hole. Flat Spectrum Radio Quasars have a strong ambient photon field and their gamma-ray emission is dominated by the more extensive zone, while in the case of BL Lac objects, the negligible ambient photons make the smaller, i.e. acceleration, zone dominant.

We examine the protoneutron star (PNS) stability in this study by solving the radial oscillation equations. For this purpose, we adopt the numerical results of massive PNS toward the black hole formation obtained by spherically symmetric numerical simulations for core-collapse supernova with general relativistic neutrino-radiation hydrodynamics. We find that the PNSs are basically stable in their evolution against the radial perturbations, while the PNS finally becomes unstable before the apparent horizon appears inside the PNS. We also examine the gravitational wave frequencies from PNS with the relativistic Cowling approximation. Then, we derive the empirical formula for the $f$-mode frequency, which weakly depends on the PNS models. This kind of universality tells us the PNS property, which is a combination of the PNS mass and radius in this study, once one would observe the $f$-mode gravitational waves.

We report a single-lens/single-source microlensing event designated as OGLE-2019-BLG-1058. For this event, the short timescale ($\sim 2.5$ days) and very fast lens-source relative proper motion ($\mu_{\rm rel} \sim 17.6\, {\rm mas\, yr^{-1}}$) suggest that this isolated lens is a free-floating planet (FFP) candidate located in the disk of our Galaxy. Because this is a high-magnification event that could have a nearby lens, we have the opportunity to measure the terrestrial microlens parallax (TPRX). We find a TPRX signal consistent with a disk FFP, but at low significance. A direct measurement of the source proper motion ($\mathbf{\mu}_{\rm S}$) shows that the large $\mu_{\rm rel}$ is due to an extreme $\mathbf{\mu}_{\rm S}$, and thus, the lens is consistent with being a very low-mass star in the bulge and the TPRX measurement is likely spurious. We show how a precise measurement of $\mathbf{\mu}_{\rm S}$ with the mean properties of the bulge proper motion distribution would have given the opposite result, i.e., provided supporting evidence for an FFP in the disk and the TPRX measurement. Because the conditions for producing TPRX (i.e., a nearby disk lens) will also tend to produce a large $\mu_{\rm rel}$, this case demonstrates how $\mathbf{\mu}_{\rm S}$ measurements in general provide a strong test of TPRX signals, which Gould et al. (2013) showed were an important probe of FFP candidates.

The Ultraviolet Transient Astronomical Satellite is a scientific space mission carrying an astronomical telescope. The mission is led by the Weizmann Institute of Science in Israel and the Israel Space Agency, while the camera in the focal plane is designed and built by Deutsches Elektronen Synchrotron in Germany. Two key science goals of the mission are the detection of counterparts to gravitational wave sources and supernovae. The launch to geostationary orbit is planned for 2024. The telescope with a field-of-view of $\approx200$deg$^2$, is optimized to work in the near-ultraviolet band between $220$ and $280$nm. The focal plane array is composed of four $22.4$-megapixel, backside-illuminated CMOS sensors with a total active area of 90x90mm$^2$. Prior to sensor production, smaller test sensors have been tested to support critical design decisions for the final flight sensor. These test sensors share the design of epitaxial layer and anti-reflective coatings (ARC) with the flight sensors. Here, we present a characterization of these test sensors. Dark current and read noise are characterized as a function of the device temperature. A temperature-independent noise level is attributed to on-die infrared emission and the read-out electronics` self-heating. We utilize a high-precision photometric calibration setup to obtain the test sensors` quantum efficiency (QE) relative to PTB/NIST-calibrated transfer standards ($220$-$1100$nm), the quantum yield for $\lambda < 300$nm, the non-linearity of the system, and the conversion gain. The uncertainties are discussed in the context of the newest results on the setup`s performance parameters. From three ARC options, Tstd, T1 and T2, the latter optimizes out-of-band rejection and peaks in the mid of the ULTRASAT operational waveband (max. QE $\approx80\%$ at $245\mathrm{nm}$). We recommend ARC option T2 for the final ULTRASAT UV sensor.

The peripheral regions of globular clusters (GCs) are extremely challenging to study due to their low surface brightness nature and the dominance of Milky Way contaminant populations along their sightlines. We have developed a probabilistic approach to this problem through utilising a mixture model in spatial and proper motion space which separately models the cluster, extra-tidal and contaminant stellar populations. We demonstrate the efficacy of our method through application to Gaia EDR3 photometry and astrometry in the direction of NGC 5139 ($\omega$ Cen), a highly challenging target on account of its Galactic latitude ($b\approx 15^{\circ}$) and low proper motion contrast with the surrounding field. We recover the spectacular tidal extensions, spanning the $10^{\circ}$ on the sky explored here, seen in earlier work and quantify the star count profile and ellipticity of the system out to a cluster-centric radius of $4^{\circ}$. We show that both RR Lyrae and blue horizontal branch stars consistent with belonging to $\omega$ Cen are found in the tidal tails, and calculate that these extensions contain at least $\approx 0.1$ per cent of the total stellar mass in the system. Our high probability members provide prime targets for future spectroscopic studies of $\omega$ Cen out to unprecedented radii.

Are we alone? In our quest to find life beyond Earth, we use our own planet to develop and verify new methods and techniques to remotely detect life. Our Life Signature Detection polarimeter (LSDpol), a snapshot full-Stokes spectropolarimeter to be deployed in the field and in space, looks for signals of life on Earth by sensing the linear and circular polarization states of reflected light. Examples of these biosignatures are linear polarization resulting from O2-A band and vegetation, e.g. the Red edge and the Green bump, as well as circular polarization resulting from the homochirality of biotic molecules. LSDpol is optimized for sensing circular polarization. To this end, LSDpol employs a spatial light modulator in the entrance slit of the spectrograph, a liquid-crystal quarter-wave retarder where the fast axis rotates as a function of slit position. The original design of LSDpol implemented a dual-beam spectropolarimeter by combining a quarter-wave plate with a polarization grating. Unfortunately, this design causes significant linear-to-circular cross-talk. In addition, it revealed spurious polarization modulation effects. Here, we present numerical simulations that illustrate how Fresnel diffraction effects can create these spurious modulations. We verified the simulations with accurate polarization state measurements in the lab using 100% linearly and circularly polarized light.

We introduce the STAR-MELT Python package that we developed to facilitate the analysis of time-resolved emission line spectroscopy of young stellar objects. STAR-MELT automatically extracts, identifies and fits emission lines. We summarise our analysis methods that utilises the time domain of high-resolution stellar spectra to investigate variability in the line profiles and corresponding emitting regions. This allows us to probe the innermost disc and accretion structures of YSOs. Local temperatures and densities can be determined using Boltzmann statistics, the Saha equation, and the Sobolev large velocity gradient approximation. STAR-MELT allows for new results to be obtained from archival data, as well as facilitating timely analysis of new data as it is obtained. We present the results of applying STAR-MELT to three YSOs, using spectra from UVES, XSHOOTER, FEROS, HARPS, and ESPaDOnS. We demonstrate what can be achieved for data with disparate time sampling, for stars with different inclinations and variability types. For EX Lupi, we confirm the presence of a localised and stable stellar-surface hot spot associated with the footprint of the accretion column. For GQ Lupi A, we find that the maximum infall rate from an accretion column is correlated with lines produced in the lowest temperatures. For CVSO109 we investigate the rapid temporal variability of a redshifted emission wing, indicative of rotating and infalling material in the inner disc. Our results show that STAR-MELT is a useful tool for such analysis, as well as other applications for emission lines.

The maximum mass of neutron stars (NSs) is of great importance for constraining equations of state of NSs and understanding the mass gap between NSs and stellar-mass black holes. NSs in X-ray binaries would increase in mass by accreting material from their companions (known as recycling process), and the uncertainties in the accretion process give challenge to study the NS mass at birth. {In this work, we investigate the NS accreted mass with considering the effect of NS spin evolution and give the maximum accreted mass for NSs in the recycling process. By exploring a series of binary evolution calculations, we obtain the final NS mass and the maximum accreted mass for a given birth mass of NS and a mass transfer efficiency. Our results show that the NSs can accrete relatively more material for binary systems with the donor masses in the range of $1.8\sim 2.4M_\odot$, the NSs accrete relatively more mass when the remnant WD mass is in the range of $\sim 0.25-0.30M_\odot$, and the maximum accreted mass is positively correlated with the initial NS mass. For a $1.4M_\odot$ NS at birth with a moderate mass transfer efficiency of 0.3, the maximum accreted mass could be $0.27M_\odot$. The results can be used to estimate the minimum birth mass for systems with massive NSs in observations.

Highly extended gamma-ray emission around the Geminga pulsar was discovered by Milagro and verified by HAWC. Despite many observations with Imaging Atmospheric Cherenkov Telescopes (IACTs), detection of gamma-ray emission on angular scales exceeding the IACT field-of-view has proven challenging. Recent developments in analysis techniques have enabled the detection of significant emission around Geminga in archival data with H.E.S.S.. In 2019, further data on the Geminga region were obtained with an adapted observation strategy. Following the announcement of the detection of significant TeV emission around Geminga in archival data, in this contribution we present the detection in an independent dataset. New analysis results will be presented, and emphasis given to the technical challenges involved in observations of highly extended gamma-ray emission with IACTs.

The High Energy Stereoscopic System (H.E.S.S.) is an array of five Imaging Atmospheric Cherenkov Telescopes located in the Khomas Highland of Namibia. H.E.S.S. observes gamma rays above tens of GeV by detecting the Cherenkov light that is produced when Very High Energy gamma rays interact with the Earth's atmosphere. The H.E.S.S. Data Acquisition System (DAQ) coordinates the nightly telescope operations, ensuring that the various components communicate properly and behave as intended. It also provides the interface between the telescopes and the people on shift who guide the operations. The DAQ comprises both the hardware and software, and since the beginning of H.E.S.S., both elements have been continuously adapted to improve the data-taking capabilities of the array and push the limits of what H.E.S.S. is capable of. Most recently, this includes the upgrade of the entire computing cluster hosting the DAQ software, and the accommodation of a new camera on the large 28m H.E.S.S. telescope. We discuss the performance of the upgraded DAQ and the lessons learned from these activities.

In October 2019 the central 28m telescope of the H.E.S.S. experiment has been upgraded with a new camera. The camera is based on the FlashCam design which has been developed in view of a possible future implementation in the medium-sized telescopes of the Cherenkov Telescope Array (CTA). We report here on the results of the science verification program that has been performed after commissioning of the new camera, to show that the camera and software pipelines are working up to expectations.

The energy and spectral shape of radio bursts may help us understand the generation mechanism of solar eruptions, including solar flares, CMEs, eruptive filaments, and various scales of jets. The different kinds of flares may have different characteristics of energy and spectral distribution. In this work, we selected 10 mostly confined flare events during October 2014 to investigate their overall spectral behavior and the energy emitted in microwaves by using radio observations from microwaves to interplanetary radio waves, and X-ray observations of GOES, RHESSI, and Fermi/GBM. We found that: All the confined flare events were associated with a microwave continuum burst extending to frequencies of 9.4 - 15.4 GHz, and the peak frequencies of all confined flare events are higher than 4.995 GHz and lower than or equal to 17 GHz. The median value is around 9 GHz. The microwave burst energy (or fluence) as well as the peak frequency are found to provide useful criteria to estimate the power of solar flares. The observations imply that the magnetic field in confined flares tends to be stronger than that in 412 flares studied by Nita et al. 2004. All 10 events studied did not produce detectable hard X-rays with energies above 300 keV indicating the lack of efficient acceleration of electrons to high energies in the confined flares.

The Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO) returns high-resolution images of the solar atmosphere in seven extreme ultraviolet wavelength channels. The images are processed on the ground to remove intensity spikes arising from energetic particles hitting the instrument, and the despiked images are provided to the community. In this work a three-hour series of images from the 171 A channel obtained on 2017 February 28 was studied to investigate how often the despiking algorithm gave false positives caused by compact brightenings in the solar atmosphere. The latter were identified through spikes appearing in the same detector pixel for three consecutive frames, and 1096 examples were found from the 900 image frames. These "three-spikes" were assigned to 126 dynamic solar features, and it is estimated that the three-spike method identifies 25% of the total number of features affected by despiking. For any 10 minute sequence of AIA 171 A images there are therefore around 28 solar features that have their intensity modified by despiking. The features are found in active regions, quiet Sun and coronal holes and, in relation to solar surface area, there is a greater proportion within coronal holes. In 96% of the cases, the despiked structure is a compact brightening of size 2 arcsec or less and the remaining 4% have narrow, elongated structures. In all cases, the events are not rendered invisible by the AIA processing pipeline, but the total intensity over the event's lifetimes can be reduced by up to 67%. Scientists are recommended to always restore the original intensities to AIA data when studying short-lived or rapidly-evolving features that exhibit fine-scale structure.

Beams of ultra-relativistic electrons in blazar jets develop pair cascades interacting with ambient soft photons. Employing coupled kinetic equations with escape terms, we model the unsaturated pair cascade spectrum. We assume that the gamma rays predominantly scatter off recombination-line photons from clouds photoionised by the irradiation from the accretion disk and the jet. The cascade spectrum is rather insensitive to the injection of hard electron spectra associated with the short-time variability of blazars. Adopting physical parameters representative of Markarian 501 and 3C 279, respectively, we numerically obtain spectral energy distributions showing distinct features imprinted by the recombination-line photons. The hints for a peculiar feature at ~3 TeV in the spectrum of Markarian 501, detected with the MAGIC telescopes during a strong X-ray flux activity in 2014 July, can be explained in this scenario as a result of the up-scattering of line photons by beam electrons and the low pair-creation optical depth. Inspecting a high-fidelity Fermi-LAT spectrum of 3C 279 from January 2018 reveals troughs in the spectrum that coincide with the threshold energies for gamma rays producing pairs in collisions with recombination-line photons, and the absence of exponential attenuation. Our finding implies that the gamma rays in 3C 279 escape from the edge of the broad emission line region.

This paper presents a systematic and accurate treatment of the evolution of cosmological perturbations in self-interacting dark matter models, for particles which decoupled from the primordial plasma while relativistic. We provide a numerical implementation of the Boltzmann hierarchies developed in a previous paper [JCAP, 09 (2020) 041] in a publicly available Boltzmann code and show how it can be applied to realistic DM candidates such as sterile neutrinos either under resonant or non-resonant production mechanisms, and for different field mediators. At difference with traditional fluid approximations - also known as a $c_{\rm eff}-c_{\rm vis}$ parametrizations- our approach follows the evolution of phase-space perturbations under elastic DM interactions for a wide range of interaction models, including the effects of late kinetic decoupling. Finally, we analyze the imprints left by different self interacting models on linear structure formation, which can be constrained using Lyman-$\alpha$ forest and satellite counts. We find new lower bounds on the particle mass that are less restrictive than previous constraints.

The observations of global stellar oscillations of post main-sequence stars by space-based photometry missions allowed to directly determine their internal rotation. These constraints have pointed towards the existence of angular momentum transport processes unaccounted for in theoretical models. Constraining the properties of their internal rotation thus appears as the golden path to determine the physical nature of these missing dynamical processes. We wish to determine the robustness of a new approach to study the internal rotation of post main-sequence stars, using parametric rotation profiles coupled to a global optimization technique. We test our methodology on Kepler 56, a red giant observed by the Kepler mission. First, we carry out an extensive modelling of the star using global and local minimizations techniques, and seismic inversions. Then, using our best model, we study in details its internal rotation profile, we adopted a Bayesian approach to constrain stellar parametric predetermined rotation profiles using a Monte Carlo Markov Chain analysis of the rotational splittings of mixed modes. Our Monte Carlo Markov Chain analysis of the rotational splittings allows to determine the core and envelope rotation of Kepler 56 as well as give hints about the location of the transition between the slowly rotating envelope and the fast rotating core. We are able to discard a rigid rotation profile in the radiative regions followed by a power-law in the convective zone and show that the data favours a transition located in the radiative region, as predicted by processes originating from a turbulent nature. Our analysis of Kepler 56 indicates that turbulent processes whose transport efficiency is reduced by chemical gradients are favoured, while large scale fossil magnetic fields are disfavoured as a solution to the missing angular momentum transport.

As a consequence of the large (and growing) number of near-Earth objects discovered, some of them are lost before their orbit can be firmly established to ensure long-term recovery. A fraction of these present non-negligible chances of impact with the Earth. We present a method of targeted observations that allowed us to eliminate that risk by obtaining deep images of the area where the object would be, should it be on a collision orbit. 2006 QV89 was one of these objects, with a chance of impact with the Earth on 2019 September 9. Its position uncertainty (of the order of 1 degree) and faintness (below V$\sim$24) made it a difficult candidate for a traditional direct recovery. However, the position of the virtual impactors could be determined with excellent accuracy. In July 2019, the virtual impactors of 2006 QV89 were particularly well placed, with a very small uncertainty region, and an expected magnitude of V$<$26. The area was imaged using ESO's Very Large Telescope, in the context of the ESA/ESO collaboration on Near-Earth Objects, resulting in very constraining a non-detection. This resulted in the elimination of the virtual impactor, even without effectively recovering 2006 QV89, indicating that it did not represent a threat. This method of deep non-detection of virtual impactors demonstrated a large potential to eliminate the threat of other-wise difficult to recover near-Earth objects

Ellerman bombs (EBs) and UV bursts are both small-scale solar activities that occur in active regions. They are now believed to form at different heights in the lower atmosphere. In this paper, we use one-dimensional radiative hydrodynamic simulations to calculate various line profiles in response to heating in different atmospheric layers. We confirm that heating in the upper photosphere to the lower chromosphere can generate spectral features of typical EBs, while heating in the mid to upper chromosphere can generate spectral features of typical UV bursts. The intensity evolution of the H$\alpha$ line wing in EBs shows a rise--plateau pattern, while that of the Si IV 1403 \r{A} line center in UV bursts shows a rise--fall pattern. However, the predicted enhancement of FUV continuum near 1400 \r{A} for EBs is rarely reported and requires further observations to check it. With two heating sources or an extended heating source in the atmosphere, both EB and UV burst features could be reproduced simultaneously.

Recently, a class of Roche-lobe-filling binary systems consisting of hot subdwarf stars and white dwarfs with sub-hour periods has been discovered. At present, the hot subdwarf is in a shell He burning phase and is transferring some of its remaining thin H envelope to its white dwarf companion. As the evolution of the hot subdwarf continues, it is expected to detach, leaving behind a low mass C/O core white dwarf secondary with a thick He layer. Then, on a timescale of $\sim 10$ Myr, gravitational wave radiation will again bring the systems into contact. If the mass transfer is unstable and results in a merger and a catastrophic thermonuclear explosion is not triggered, it creates a remnant with a C/O-dominated envelope, but one still rich enough in He to support an R Corona Borealis-like shell burning phase. We present evolutionary calculations of this phase and discuss its potential impact on the cooling of the remnant white dwarf.

Surface abundances of 14 (11 majority class and 3 minority class) R Coronae Borealis stars (RCBs) along with the final flash object, V4334 Sgr (Sakurai's object) are revised based on their carbon abundances measured from the observed C2 bands; note that the earlier reported abundances were derived using an assumed carbon abundance due to the well known ``carbon problem''. The hot RCB MV Sgr is not subject to a carbon problem; it is remarkable to note that MV Sgr's carbon abundance lies in the range that is measured for the majority and minority class RCBs. The revised iron abundances for the RCBs are in the range log E(Fe)=3.8 to log E(Fe)=5.8 with the minority class RCB V854 Cen at lower end and the majority class RCB R CrB at the higher end of this range. Indications are that the revised RCBs' metallicity range is roughly consistent with the metal poor population contained within the bulge. The revised abundances of RCBs are then compared with extreme helium stars (EHes), the hotter relatives of RCBs. Clear differences are observed between RCBs and EHes in their metallicity distribution, carbon abundances, and the abundance trends observed for the key elements. These abundances are further discussed in the light of their formation scenarios.

Despite the success of the standard $\Lambda$CDM model of cosmology, recent data improvements have made tensions emerge between low- and high-redshift observables, most importantly in determinations of the Hubble constant $H_0$ and the (rescaled) clustering amplitude $S_8$. The high-redshift data, from the cosmic microwave background (CMB), crucially relies on recombination physics for its interpretation. Here we study how small-scale baryon inhomogeneities (i.e., clumping) can affect recombination and consider whether they can relieve both the $H_0$ and $S_8$ tensions. Such small-scale clumping, which may be caused by primordial magnetic fields or baryon isocurvature below kpc scales, enhances the recombination rate even when averaged over larger scales, shifting recombination to earlier times. We introduce a flexible clumping model, parametrized via three spatial zones with free densities and volume fractions, and use it to study the impact of clumping on CMB observables. We find that increasing $H_0$ decreases both $\Omega_m$ and $S_8$, which alleviates the $S_8$ tension. On the other hand, the shift in $\Omega_m$ is disfavored by the low-$z$ baryon-acoustic-oscillations measurements. We find that the clumping parameters that can change the CMB sound horizon enough to explain the $H_0$ tension also alter the damping tail, so they are disfavored by current {\it Planck} 2018 data. We test how the CMB damping-tail information rules out changes to recombination by first removing $\ell>1000$ multipoles in {\it Planck} data, where we find that clumping could resolve the $H_0$ tension. Furthermore, we make predictions for future CMB experiments, as their improved damping-tail precision can better constrain departures from standard recombination. Both the {\it Simons Observatory} and CMB-S4 will provide decisive evidence for or against clumping as a resolution to the $H_0$ tension.

The neutrino band above 10 PeV remains one of the last multi-messenger windows to be opened, a challenge that several groups tackle. One of the proposed instruments is Trinity, a system of air-shower imaging telescopes to detect Earth-skimming neutrinos with energies from $10^6$ GeV to $10^{10}$ GeV. We present updated sensitivity calculations demonstrating Trinity's capability of not only detecting the IceCube measured diffuse astrophysical neutrino flux but doing so in an energy band that overlaps with IceCube's. Trinity will distinguish between different cutoff scenarios of the astrophysical neutrino flux, which will help identify their sources. We also discuss Trinity's sensitivity to transient sources on timescales from hours to years.

The parity violating gravity models based on the symmetric teleparallel gravity have been considered in the literature, but their applications in cosmology and especially the modifications to cosmological perturbations have not been fully explored. In this paper we consider such a simple model which modifies general relativity by a parity non-conserved coupling, within the framework of the symmetric teleparallel gravity. We study in detail its cosmological applications and focus on its cosmological perturbation theory. Besides the already known parity violation in the tensor perturbations, we find that the vector perturbations in this model are promoted to be dynamical degrees of freedom, and the left- and right-handed vector modes propagate with different velocities. More importantly, we find that one of the vector modes is a ghost at high momentum scales, which will give rise to the problem of vacuum instability in the quantum theory of cosmological perturbations.

We study $R^2$-Higgs inflation in a model with two Higgs doublets. The context is the general two Higgs doublet model where the Higgs sector of the Standard Model is extended by an additional Higgs doublet. We first discuss the required inflationary dynamics in this two Higgs doublet model, which includes four scalar fields, in the covariant formalism allowing a nonminimal coupling between the Higgs-squared and the Ricci scalar $R$, as well as the $R^2$ term. We find that the parameter space favored by $R^2$-Higgs inflation requires nearly degenerate $m_\mathsf{H}$, $m_A$ and $m_{\mathsf{H}^\pm}$, where $\mathsf{H}$, $A$, and $\mathsf{H}^\pm$ are the extra CP even, CP odd, and charged Higgs bosons in the general two Higgs doublet model taking renormalization group evolutions of the parameters into account. Discovery of such heavy scalars at the Large Hadron Collider are possible if they are in the sub-TeV mass range. Indirect evidences may also emerge at the LHCb and Belle-II experiments, however, to probe the quasi degenerate mass spectra one would likely require future lepton colliders such as the International Linear Collider and the Future Circular Collider.

We survey the prospective sensitivities of terrestrial and space-borne atom interferometers (AIs) to gravitat- ional waves (GWs) generated by cosmological and astrophysical sources, and to ultralight dark matter. We discuss the backgrounds from gravitational gradient noise (GGN) in terrestrial detectors, and also binary pulsar and asteroid backgrounds in space- borne detectors. We compare the sensitivities of LIGO and LISA with those of the 100m and 1km stages of the AION terrestrial AI project, as well as two options for the proposed AEDGE AI space mission with cold atom clouds either inside or outside the spacecraft, considering as possible sources the mergers of black holes and neutron stars, supernovae, phase transitions in the early Universe, cosmic strings and quantum fluctuations in the early Universe that could have generated primordial black holes. We also review the capabilities of AION and AEDGE for detecting coherent waves of ultralight scalar dark matter.

Well-tempering stands among the few classical methods of screening vacuum energy to deliver a late-time, low energy vacuum state. We build on the class of Horndeski models that admit a Minkowski vacuum state despite the presence of an arbitrarily large vacuum energy to obtain a much larger family of models in teleparallel Horndeski theory. We set up the routine for obtaining these models and present a variety of cases, all of which are able to screen a natural particle physics scale vacuum energy using degeneracy in the field equations. We establish that well-tempering is the unique method of utilizing degeneracy in Horndeski scalar-tensor gravity -- and its teleparallel generalisation -- that can accommodate self-tuned flat Minkowski solutions, when the explicit scalar field dependence in the action is minimal (a tadpole and a conformal coupling to the Ricci scalar). Finally, we study the dynamics of the well-tempered teleparallel Galileon. We generate its phase portraits and assess the attractor nature of the Minkowski vacuum under linear perturbations and through a phase transition of vacuum energy.

We consider the capture of dark matter (DM) in neutron stars via scattering on hadronic targets, including neutrons, protons and hyperons. We extend previous analyses by including momentum dependent form factors, which account for hadronic structure, and incorporating the effect of baryon strong interactions in the dense neutron star interior, rather than modelling the baryons as a free Fermi gas. The combination of these effects suppresses the DM capture rate over a wide mass range, thus increasing the cross section for which the capture rate saturates the geometric limit. In addition, variation in the capture rate associated with the choice of neutron star equation of state is reduced. For proton targets, the use of the interacting baryon approach to obtain the correct Fermi energy is essential for an accurate evaluation of the capture rate in the Pauli-blocked regime. For heavy neutron stars, which are expected to contain exotic matter, we identify cases where DM scattering on hyperons contributes significantly to the total capture rate. Despite smaller neutron star capture rates, compared to existing analyses, we find that the projected DM-nucleon scattering sensitivity greatly exceeds that of nuclear recoil experiments for a wide DM mass range.

We study the multi-dimensional radiative transfer phenomena using the ISMC scheme, in both gray and multi-frequency problems. Implicit Monte-Carlo (IMC) schemes have been in use for five decades. The basic algorithm yields teleportation errors, where photons propagate faster than the correct heat front velocity. Recently [Po\"ette and Valentin, J. Comp. Phys., 412, 109405 (2020)], a new implicit scheme based on the semi-analog scheme was presented and tested in several one-dimensional gray problems. In this scheme, the material energy of the cell is carried by material-particles, and the photons are produced only from existing material particles. As a result, the teleportation errors vanish, due to the infinite discrete spatial accuracy of the scheme. We examine the validity of the new scheme in two-dimensional problems, both in Cartesian and Cylindrical geometries. Additionally, we introduce an expansion of the new scheme for multi-frequency problems. We show that the ISMC scheme presents excellent results without teleportation errors in a large number of benchmarks, especially against the slow classic IMC convergence.

We present the new version v2.0 of the public code BlackHawk designed to compute the Hawking radiation of black holes, with both primary and hadronized spectra. This new version aims at opening an avenue toward physics beyond the Standard Model (BSM) in Hawking radiation. Several major additions have been made since version v1.0: dark matter/dark radiation emission, spin $3/2$ greybody factors, scripts for cosmological studies, BSM black hole metrics with their associated greybody factors and a careful treatment of the low energy showering of secondary particles; as well as bug corrections. We present, in each case, examples of the new capabilities of BlackHawk.

The LISA mission will likely be a signal dominated detector, such that one challenge is the separation of the different astrophysical sources, and to distinguish between them and the instrumental noise. One of the goals of LISA is to probe the early Universe by detecting stochastic GW backgrounds. As correlation with other detectors is not possible for LISA, discrimination of such a GW background from the instrumental noise requires a good estimate of the latter. To this purpose we have revisited Time Delay Interferometry (TDI) to look for new TDI signal combinations that fulfill the laser frequency noise suppression requirements. We illustrate that it is possible to do a linear combination of these TDI channels to find special null-combinations that suppress gravitational waves and mainly carry information about instrumental noise. We find that there exist many null-combinations that show different sensitivities to gravitational waves, some of which seem more suitable than the traditional T combination for estimating test-mass acceleration noise. In an idealised LISA configuration, they are all sensitive to a particular linear combination of the six test-masses acceleration, similar to a rigid rotation of the LISA triangle. In the following article, we illustrate what are the noise properties that can be extracted by monitoring these interferometry signals and discuss the implication of these findings for the detection of stochastic GW backgrounds.