Papers for Friday, Jan 27 2023

We study the link between gas flow events and key galaxy scaling relations: the relations between star formation rate (SFR) and stellar mass (the main sequence, MS), gas metallicity and stellar mass (the mass-metallicity relation, MZR) and gas metallicity, stellar mass and SFR (the fundamental metallicity relation, FMR). Using all star-forming galaxies (SFGs) in the 22 MUSE fields of the MusE GAs FLOw and Wind (MEGAFLOW) survey, we derive the MS, MZR and FMR scaling relations for 385 SFGs with $M = 10^8 - 10^{11.5}$ $M_\odot$ at redshifts 0.35 < z < 0.85. Using the MUSE data and complementary X-Shooter spectra at 0.85 < z < 1.4, we determine the locations of 21 SFGs associated with inflowing or outflowing circumgalactic gas (i.e. with strong MgII absorption in background quasar spectra) relative to these scaling relations. Compared to a control sample of galaxies without gas flows (i.e., without MgII absorption within 70 kpc of the quasar), SFGs with inflow events (i.e., MgII absorption along the major axis) are preferentially located above the MS, while SFGs with ouflow events (i.e., MgII absorption along the minor axis) are preferentially more metal rich. Our observations support the scenario in which gas accretion increases the SFR while diluting the metal content and where circumgalactic outflows are found in more metal-rich galaxies.

Quasar outflows might either quench (negative) or enhance (positive feedback) star formation in galaxies located in the quasar environment. The possible outcome depends on 4 parameters: the quasar ($\sigma$) and satellite ($\sigma_*$) halo velocity dispersion, their relative distance, $d$, and satellite disk radius, $r_d$. We find that: (i) small satellites with $\sigma _* < 164\ \sigma_{200}^{2/3}\, \rm km\ s^{-1}$ have their star formation quenched; (ii) in larger satellites, star formation, and hence UV/FIR luminosity, is instead boosted by $>80$\% in a burst with a typical duration of $5-10$ Myr, if the following positive feedback criterion is met: ${d}/{r_d} < 15 (Q/\eta)^{1/2} \sigma_{200}$, where $Q \approx 1$ is the satellite disk Toomre parameter; the disruption parameter (see eq. 17) must be $\eta>1$ to prevent complete satellite gas removal. We compare our predictions with ALMA data finding that observed satellites of $z\simeq 6$ QSOs on average form stars at a $3\times$ higher rate with respect to field galaxies at the same redshift. Further tests of the model are suggested.

One of the greatest uncertainties in any modeling of inner engine of core-collapse supernova (CCSN) is neutrino flavor conversions driven by neutrino self-interactions. We carry out large-scale numerical simulations of multi-energy, multi-angle, three-flavor framework, and general relativistic quantum kinetic neutrino transport in spherical symmetry with an essential set of neutrino-matter interactions under a realistic fluid profile of CCSN. Our result suggests that the neutrino heating in the gain region is reduced by $\sim 50\%$ due to fast neutrino-flavor conversion (FFC). We also find that the total luminosity of neutrinos is enhanced by $\sim 30 \%$, for which the substantial increase of heavy-leptonic neutrinos by FFCs are mainly responsible. This study provides evidence that FFC has a significant impact on the delayed neutrino-heating mechanism.

We study the statistical properties of O VI, C IV, and Ne VIII absorbers at low-$z$ (i.e., $z<0.5$) using Sherwood simulations with "WIND" only and "WIND+AGN" feedback and Massive black simulation that incorporates both "WIND" and AGN feedbacks. For each simulation, by considering a wide range of metagalactic ionizing UV background (UVB), we show the statistical properties such as distribution functions of column density ($N$), $b$-paramerer and velocity spread ($\Delta V_{90}$), the relationship between $N$ and $b$-parameter and the fraction of Lya absorbers showing detectable metal lines as a function of $N$(H I) are influenced by the UVB used. This is because UVB changes the range in density, temperature, and metallicity of gas contributing to a given absorption line. For simulations considered here, we show the difference in some of the predicted distributions between different simulations is similar to the one obtained by varying the UVB for a given simulation. Most of the observed properties of O VI absorbers are roughly matched by Sherwood simulation with "WIND+AGN" feedback when using the UVB with a lower O VI ionization rate. However, this simulation fails to produce observed distributions of C IV and fraction of H I absorbers with detectable metals. Therefore, in order to constrain different feedback processes and/or UVBs, using observed properties of H I and metal ions, it is important to perform simultaneous analysis of various observable parameters.

Strong lensing offers a precious opportunity for studying the formation and early evolution of super star clusters that are rare in our cosmic backyard. The Sunburst Arc, a lensed Cosmic Noon galaxy, hosts a young super star cluster with escaping Lyman continuum radiation. Analyzing archival HST images and emission line data from VLT/MUSE and X-shooter, we construct a physical model for the cluster and its surrounding photoionized nebula. We confirm that the cluster is $\sim 3\mbox{--}4\,$Myr old, is extremely massive $M_\star \sim 10^7\,M_\odot$ and yet has a central component as compact as several parsecs, and we find a metallicity $Z=(0.26\pm0.03)\,Z_\odot$. The cluster is surrounded by $\gtrsim 10^5\,M_\odot$ of dense clouds that have been pressurized to $P\sim 10^9\,{\rm K}\,{\rm cm}^{-3}$ by perhaps stellar radiation at within ten parsecs. These should have large neutral columns $N_{\rm HI} > 10^{22.5}\,{\rm cm}^{-2}$ to survive rapid ejection by radiation pressure. The clouds are likely dusty as they show gas-phase depletion of silicon, and may be conducive to secondary star formation if $N_{\rm HI} > 10^{24}\,{\rm cm}^{-2}$ or if they sink further toward the cluster center. Detecting strong ${\rm N III]}\lambda\lambda$1750,1752, we infer heavy nitrogen enrichment $\log({\rm N/O})=-0.23^{+0.08}_{-0.11}$. This requires efficiently retaining $\gtrsim 500\,M_\odot$ of nitrogen in the high-pressure clouds from massive stars heavier than $60\,M_\odot$ up to 4 Myr. We suggest a physical origin of the high-pressure clouds from partial or complete condensation of slow massive star ejecta, which may have important implication for the puzzle of multiple stellar populations in globular clusters.

A light ($m_{\nu d} \lesssim $ MeV) dark fermion mixing with the Standard Model neutrinos can naturally equilibrate with the neutrinos via oscillations and scattering. In the presence of dark sector interactions, production of dark fermions is generically suppressed above BBN, but then enhanced at later times. Over much of the parameter space, we find that the dark sector equilibrates, even for mixing angles $\theta_0$ as small as $10^{-13}$, and equilibration occurs at $T_{\rm equil} \simeq m_{\nu d} \left(\theta_0^2 M_{Pl}/ m_{\nu d} \right)^{1/5} $ which is naturally at most a few orders of magnitude above the dark fermion mass. The implications of this are twofold: one, that light states are often only constrained by the CMB and LSS without leaving an imprint on BBN, and two, that sectors which equilibrate before recombination will typically have a mass threshold before recombination, as well. This can result in dark radiation abruptly transitioning from non-interacting to interacting, or vice-versa, a ``step'' in the amount of dark radiation, and dark matter with similar transitions in its interactions, all of which can leave important signals in the CMB and LSS, and may be relevant for cosmological tensions in observables such as $H_0$ or $S_8$. Minimal models leave an unambiguous imprint on the CMB above the sensitivity of upcoming experiments.

A good understanding of the ionization rates of neutral species in the heliosphere is important for studies of the heliosphere and planetary atmospheres. So far, the intensities of the ionization reactions have been studied based on observations of the contributing phenomena, such as the solar spectral flux in the EUV band and the flux of the solar wind protons, alpha particles, and electrons. The results strongly depend on absolute calibration of these measurements, which, especially for the EUV measurements, is challenging. Here, we propose a novel method of determining the ionization rate of neutral species based on direct sampling of interstellar neutral gas from two locations in space distant to each other. In particular, we suggest performing observations from the vicinity of Earth's orbit and using ratios of fluxes of ISN He for the direct and indirect orbits of interstellar atoms. We identify the most favorable conditions and observations geometries, suitable for implementation on the forthcoming NASA mission Interstellar Mapping and Acceleration Probe.

We report the detection of a gas-giant planet in orbit around both stars of an eclipsing binary star system that also contains the smaller, inner transiting planet TOI-1338b. The new planet, called TOI-1338/BEBOP-1c, was discovered using radial-velocity data collected with the HARPS and ESPRESSO spectrographs. Our analysis reveals it is a $65.2~\rm{M_{\oplus}}$ circumbinary planet with a period of 215.5 days. This is the first detection of a circumbinary planet using radial-velocity observations alone, and makes TOI-1338/BEBOP-1 only the second confirmed multiplanet circumbinary system to date. We do not detect the smaller inner transiting planet with radial-velocity data, and can place an upper limit on the inner planet's mass at $21.8~\mathrm{M}_\oplus$ with $99\%$ confidence. The inner planet is the first circumbinary planet amenable for atmospheric characterisation, using the James Webb Space Telescope.

Context. The near-Earth orbital space is shared by natural objects and space debris that can be temporarily captured in geocentric orbits. Short-term natural satellites are often called mini-moons. Reflectance spectroscopy can determine the true nature of transient satellites because the spectral signatures of spacecraft materials and near-Earth asteroids (NEAs) are different. The recently discovered object 2022 NX1 follows an Earth-like orbit that turns it into a recurrent but ephemeral Earth companion. It has been suggested that 2022 NX1 could have an artificial origin or be lunar ejecta. Aims. Here, we use reflectance spectroscopy and N-body simulations to determine the nature and actual origin of 2022 NX1. Methods. We carried out an observational study of 2022 NX1, using the OSIRIS camera spectrograph at the 10.4 m Gran Telescopio Canarias, to derive its spectral class. N-body simulations were also performed to investigate how it reached NEA space. Results. The reflectance spectrum of 2022 NX1 is neither compatible with an artificial origin nor lunar ejecta; it is also different from the V type of the only other mini-moon with available spectroscopy, 2020 CD3. The visible spectrum of 2022 NX1 is consistent with that of a K-type asteroid, although it could also be classified as an Xk type. Considering typical values of the similar albedo of both K-type and Xk-type asteroids and its absolute magnitude, 2022 NX1 may have a size range of 5 to 15 m. We confirm that 2022 NX1 inhabits the rim of Earth's co-orbital space, the 1:1 mean-motion resonance, and experiences recurrent co-orbital engagements of the horseshoe-type and mini-moon events. Conclusions. The discovery of 2022 NX1 confirms that mini-moons can be larger than a few meters and also that they belong to a heterogeneous population in terms of surface composition.

The Jao Gap, a 17 percent decrease in stellar density at $M_G \sim10$ identified in both Gaia DR2 and EDR3 data, presents a new method to probe the interior structure of stars near the fully convective transition mass. The Gap is believed to originate from convective kissing instability wherein asymmetric production of $^{3}$He causes the core convective zone of a star to periodically expand and contract and consequently the stars' luminosity to vary. Modeling of the Gap has revealed a sensitivity in its magnitude to a population's metallicity primarily through opacity. Thus far, models of the Jao Gap have relied on OPAL high-temperature radiative opacities. Here we present updated synthetic population models tracing the Gap location modeled with the Dartmouth stellar evolution code using the OPLIB high-temperature radiative opacities. Use of these updated opacities changes the predicted location of the Jao Gap by $\sim0.05$ mag as compared to models which use the OPAL opacities. This difference is likely too small to be detectable in empirical data.

Global seismicity on all three solar system's bodies with in situ measurements -- Earth, Moon, and Mars -- is due mainly to mechanical Rieger resonance (RR) of the solar wind's macroscopic flapping, driven by the well-known PRg=~154-day Rieger period and detected commonly in most heliophysical data types and the interplanetary magnetic field (IMF). Thus, InSight mission marsquakes rates are periodic with PRg as characterized by a very high (>>12) fidelity {\Phi}=2.8 10^6 and by being the only 99%-significant spectral peak in the 385.8-64.3-nHz (1-180-day) band of highest planetary energies; the longest-span (v.9) release of raw data revealed the entire RR, excluding a tectonically active Mars. For check, I analyze rates of Oct 2015-Feb 2019, Mw5.6+ earthquakes, and all (1969-1977) Apollo mission moonquakes. To decouple magnetosphere and IMF effects, I study Earth and Moon seismicity during traversals of the Earth magnetotail vs. IMF. The analysis showed with 99-67% confidence and {\Phi}>>12 fidelity that (an unspecified majority of) moonquakes and Mw5.6+ earthquakes also recur at Rieger periods. About half of the spectral peaks split but also into clusters that average to the usual Rieger periodicities, where magnetotail reconnecting clears the signal. Earlier claims that solar plasma dynamics could be seismogenic due to electrical surging or magnetohydrodynamic interactions between magnetically trapped plasma and water molecules embedded within solid matter are confirmed. This result calls for reinterpreting the seismicity phenomenon and for reliance on global magnitude scales. The predictability of solar-wind macroscopic dynamics is now within reach for the first time, which will benefit seismic and weather prediction and the safety of space missions.

We present 850um imaging of the XMM-LSS field observed for 170 hours as part of the James Clerk Maxwell Telescope SCUBA-2 Large eXtragalactic Survey (S2LXS). S2LXS XMM-LSS maps an area of 9 square degrees, reaching a moderate depth of 1-sigma ~ 4 mJy/beam. This is the largest contiguous area of extragalactic sky mapped by JCMT at 850um to date. The wide area of the S2LXS XMM-LSS survey allows us to probe the ultra-bright (S_850um > 15 mJy), yet rare submillimetre population. We present the S2LXS XMM-LSS catalogue, which comprises 40 sources detected at >5-sigma significance, with deboosted flux densities in the range of 7 mJy to 48 mJy. We robustly measure the bright-end of the 850um number counts at flux densities >7 mJy, reducing the Poisson errors compared to existing measurements. The S2LXS XMM-LSS observed number counts show the characteristic upturn at bright fluxes, expected to be motivated by local sources of submillimetre emission and high-redshift strongly lensed galaxies. We find that the observed 850um number counts are best reproduced by model predictions that include either strong lensing or source blending from a 15 arcsec beam, indicating that both may make an important contribution to the observed over-abundance of bright single dish 850um selected sources. We make the S2LXS XMM-LSS 850um map and >5-sigma catalogue presented here publicly available.

A gold standard for the study of M dwarfs is the eclipsing binary CM Draconis. It is rare because it is bright (Jmag = 8.5) and contains twin fully convective stars on an almost perfectly edge-on orbit. Both masses and radii were previously measured to better than 1% precision, amongst the best known. We use 12 sectors of TESS data to show that CM Draconis is the gift that keeps on giving. Our paper has three main components. First, we present updated parameters, with radii and masses constrained to previously unheard of precisions of 0.06% and 0.12%, respectively. Second, we discover strong and variable spot modulation, suggestive of spot clustering and an activity cycle on the order of years. Third, we discover 125 flares. The flare rate is surprisingly not reduced during eclipse, but one flare may show evidence of being occulted. We suggest the flares may be preferentially polar, which has positive implications for the habitability of planets orbiting M dwarfs.

One of the most important problems vexing the $\Lambda$CDM cosmological model is the Hubble tension. It arises from the fact that measurements of the present value of the Hubble parameter performed with low-redshift quantities, e.g., the Type IA supernova, tend to yield larger values than measurements from quantities originating at high-redshift, e.g., fits of cosmic microwave background radiation. It is becoming likely that the discrepancy, currently standing at $5\sigma$, is not due to systematic errors in the measurements. Here we explore whether the self-interaction of gravitational fields in General Relativity, which are traditionally neglected when studying the evolution of the universe, can explain the tension. We find that with field self-interaction accounted for, both low- and high-redshift data are simultaneously well-fitted, thereby showing that gravitational self-interaction could explain the Hubble tension. Crucially, this is achieved without introducing additional parameters.

We present observations of the 1.35+/-0.07 Earth-radius planet L 98-59 c using Wide Field Camera~3 on the Hubble Space Telescope. L 98-59 is a nearby (10.6 pc), bright (H=7.4 mag), M3V star that harbors three small, transiting planets. As one of the closest known transiting multi-planet systems, L 98-59 offers one of the best opportunities to probe and compare the atmospheres of rocky planets that formed in the same stellar environment. We measured the transmission spectrum of L 98-59 c during a single transit, with the extracted spectrum showing marginal evidence for wavelength-dependent transit depth variations which would indicate the presence of an atmosphere. Forward modeling was used to constrain possible atmospheric compositions of the planet based on the shape of the transmission spectrum. Although L 98-59 is a fairly quiet star, we have seen evidence for stellar activity, and therefore we cannot rule out a scenario where the source of the signal originates with inhomogeneities on the host-star surface. While intriguing, our results are inconclusive and additional data is needed to verify any atmospheric signal. Fortunately, additional data will soon be collected from both HST and JWST. Should this result be confirmed with additional data, L 98-59 c would be the first planet smaller than 2 Earth-radii with a detected atmosphere, and among the first small planets with a known atmosphere to be studied in detail by the JWST.

We use images collected with the near-infrared camera (NIRCam) on board the James Webb Space Telescope and with the Hubble Space Telescope (HST) to investigate multiple populations at the bottom of the main sequence (MS) of 47 Tucanae. The F115W vs. F115W-F322W2 CMD from NIRCam shows that, below the knee, the MS stars span a wide color range, where the majority of M-dwarfs exhibit blue colors, and a tail of stars are distributed toward the red. A similar pattern is observed from the F160W vs. F110W-F160W CMD from HST, and multiple populations of M-dwarfs are also visible in the optical F606W vs. F606W-F814W CMD. The NIRCam CMD shows a poorly-populated sequence of faint MS stars that we tentatively associate with a population of very low-mass stars. We introduce a chromosome map of M-dwarfs that reveals an extended first population and three main groups of second-population stars. By combining isochrones and synthetic spectra with appropriate chemical composition, we simulate colors and magnitudes of different stellar populations in the NIRCam filters (at metallicities [Fe/H]=-1.5 and [Fe/H]=-0.75) and identify the photometric bands that provide the most efficient diagrams to investigate the multiple populations in globular clusters. Models are compared with the observed CMDs of 47 Tucanae to constrain M-dwarfs' chemical composition. Our analysis suggests that the oxygen range needed to reproduce the colors of first- and second-population M-dwarfs is similar to that inferred from spectroscopy of red giants, challenging the proposal that the chemical variations are due to mass transfer phenomena in proto-clusters.

The search for extraterrestrial intelligence (SETI) is to search for technosignatures associated with extraterrestrial life, such as engineered radio signals. In this paper, we apply the multibeam coincidence matching (MBCM) strategy, and propose a new search mode based on the MBCM which we call MBCM blind search mode. In our recent targeted SETI research, 33 exoplanet systems are observed by the Five-hundred-meter Aperture Spherical radio Telescope (FAST). With this blind search mode, we search for narrowband drifting signals across $1.05-1.45$ GHz in two orthogonal linear polarization directions separately. There are two special signals, one of which can only be detected by the blind search mode while the other can be found by both blind and targeted search modes. This result reveals huge advantages of the new blind search mode. However, we eliminate the possibility of the special signals being ETI signals based on much evidence, such as the polarization, drift, frequency and beam coverage characteristics. Our observations achieve an unprecedented sensitivity and our work provides a deeper understanding to the polarization analysis of extraterrestrial signals.

We present a new method to simultaneously/self-consistently model the mass distribution of galaxy clusters that combines constraints from strong lensing features, X-ray emission and galaxy kinematics measurements. We are able to successfully decompose clusters into their collisionless and collisional mass components thanks to the X-ray surface brightness, as well as using the dynamics of cluster members to obtain more accurate masses with the fundamental plane of elliptical galaxies. Knowledge from all observables is included through a consistent Bayesian approach in the likelihood or in physically motivated priors. We apply this method to the galaxy cluster Abell S1063 and produce a mass model that we publicly release with this paper. The resulting mass distribution presents a different ellipticities for the intra-cluster gas and the other large-scale mass components; and deviation from elliptical symmetry in the main halo. We assess the ability of our method to recover the masses of the different elements of the cluster using a mock cluster based on a simplified version of our Abell S1063 model. Thanks to the wealth of information provided by the mass model and the X-ray emission, we also found evidence for an on-going merger event with gas sloshing from a smaller infalling structure into the main cluster. In agreement with previous findings, the total mass, gas profile and gas mass fraction are consistent with small deviations from the hydrostatic equilibrium. This new mass model for Abell S1063 is publicly available as is the software used to construct it through the \textsc{Lenstool} package.

In this work, we consider the properties of compact stars in which quark matter has low- and high-density phases that are separated by a first-order phase transition. Thus, unlike the commonly considered case of a single-phase transition from hadronic to quark matter, our models of hybrid stars contain sequential phase transitions from hadronic matter to low- and then to high-density quark matter phases. We extend our previous study of the parameter space of hybrid stars with a single phase transition to those with sequential phase transitions, taking into account the constraints on the mass and radius of neutron stars from the NICER experiment, the experimental inferences of the neutron skin thickness of Lead nucleus by the PREX-II experiment and constraints on the tidal deformability from the gravitational wave event GW170817. We determine the range of the masses for which both twin and triplet configurations, i.e., identical-mass stars with two and three different values of radii arise.

Hyperactive comets are a small group of comets whose activity are higher than expected. They seem to emit more water than they should based on the size of their nucleus and comet 46P/Wirtanen is one of them. Investigating its activity and composition evolution could provide clues about its origins and formation region in the Solar nebulae. Given the exceptional close approach in 2018 of comet 46P to the Earth, we aim to study the evolution of its activity and composition as a function of heliocentric distances before and after perihelion. We used both TRAPPIST telescopes to monitor the comet for almost a year with broad-band and narrow-band filters. We derived the production rates of five gaseous species, e.g. OH, NH, CN, C$_3$ and C$_2$, using a Haser model as well as the A($\theta$)f$\rho$, dust proxy parameter. The comet was also observed with two optical high resolution spectrographs UVES and ESPRESSO mounted on the 8-m ESO VLT to measure the isotopic ratios of C and N, the oxygen forbidden lines ratios and the NH$_2$ ortho-to-para ratios. We followed during almost a year the rise and decline of the production rates of different species as well as the dust activity of 46P on both pre- and post-perihelion. Relative abundances with respect to CN and OH along the orbit of the comet show constant and symmetric abundance ratios and a typical coma composition. We determined the rotation period of the nucleus using high cadence observations and long series of CN images on several nights, and we obtained a value of (9.18$\pm$0.05) hr at perihelion. Using high resolution spectra of 46P coma, we derived C and N isotopic ratios of 100$\pm$20 and 150$\pm$30 and a green-to-red forbidden oxygen [OI] lines ratio of 0.23$\pm$0.02. We measured a NH$_2$ ortho-to-para ratio of 3.31$\pm$0.03 and derived an ammonia ratio of 1.19$\pm$0.03 corresponding to a spin temperature of 27$\pm$1 K.

Bimetric gravity is an interesting alternative to standard GR given its potential to provide a concrete theoretical framework for a ghost-free massive gravity theory. Here we investigate a class of Bimetric gravity models for their cosmological implications. We study the background expansion as well as the growth of matter perturbations at linear and second order. We use low-redshift observations from SnIa (Pantheon+ and SH0ES), Baryon Acoustic Oscillations (BAO), the growth ($f\sigma_{8}$) measurements and the measurement from Megamaser Cosmology Project to constrain the Bimetric model. We find that the Bimetric models are consistent with the present data alongside the $\Lambda$CDM model. We reconstructed the `` effective dark energy equation of state" ($\omega_{de}$) and "Skewness" ($S_{3}$) parameters for the Bimetric model from the observational constraints and show that the current low-redshift data allow significant deviations in $\omega_{de}$ and $S_{3}$ parameters with respect to the $\Lambda$CDM behaviour. We also look at the ISW effect via galaxy-temperature correlations and find that the best fit Bimetric model behaves similarly to $\Lambda$CDM in this regard.

We discovered Fe $K_{\alpha}$ complex emission and pulsation in two highly variable sources (4XMM J174917.7--283329, 4XMM J174954.6--294336). The equivalent widths of 6.4 and 6.7 keV lines of 4XMM J174917.7--283329 are $99^{+84}_{-72}$ and $220^{+160}_{-140}$ eV, respectively. The continuum is fitted by a partially absorbed apec model with plasma temperature of $kT=13^{+10}_{-2}$ keV. The inferred mass of the white dwarf (WD) is $0.9^{+0.3}_{-0.2}\ M_{\odot}$. We detected pulsations with a period of $1212\pm3$ s and a pulsed fraction of $26\pm6\%$. The light curves of 4XMM J174954.6--294336 display asymmetric eclipse and dipping behaviour. To date, this is only the second intermediate polar (IP) that shows a total eclipse in X-rays. The spectrum of the sources is characterized by a power-law model with photon index $\Gamma=0.4\pm0.2$. The equivalent widths of the 6.4 keV and 6.7 keV iron lines are $171^{+99}_{-79}$ and $136^{+89}_{-81}$ eV, respectively. The continuum is described by emission from optically thin plasma with a temperature of $kT\sim35$ keV. The inferred mass of the WD is $1.1^{+0.2}_{-0.3}\ M_{\odot}$. We discovered coherent pulsations from the source with a period of $1002\pm2$ s. The pulsed fraction is $66\pm15\%$. The measured spin period, hard photon index, and equivalent width of the fluorescent Fe $K_{\alpha}$ line in both sources are consistent with the values found in IP. While 4XMM J174954.6--294336 was already previously classified as an IP, we also suggest 4XMM J174917.7--283329 as a new IP. The X-ray eclipses in 4XMM J174954.6--294336 are most likely caused by a low-mass companion star obscuring the central X-ray source. The asymmetry in the eclipse is likely caused by a thick bulge that intercepts the line of sight during the ingress phase but not during the egress phase located behind the WD along the line of sight.

The Tunka Advanced Instrument for Gamma- and cosmic-ray Astronomy (TAIGA) is a multicomponent experiment for the measurement of TeV to PeV gamma- and cosmic rays. Our goal is to establish a novel hybrid direct air shower technique, sufficient to access the energy domain of the long-sought Pevatrons. The hybrid air Cherenkov light detection technique combines the strengths of the HiSCORE shower front sampling array, and two $\thicksim$4 m class, $\sim$9.6 deg field of view Imaging Air Cherenkov Telescopes (IACTs). The HiSCORE array provides good angular and shower core position resolution, while the IACTs provide the image shape and orientation for gamma-hadron separation. In future, an additional muon detector will be used for hadron tagging at $\ge$ 100 TeV energies. Here, only data from the first IACT of the TAIGA experiment are used. A random forest algorithm was trained using Monte Carlo (MC) simulations and real data, and applied to 85 h of selected observational data tracking the Crab Nebula at a mean zenith angle of 33.5 deg, resulting in a threshold energy of 6 TeV for this dataset. The analysis was performed using the gammapy package. A total of 163.5 excess events were detected, with a statistical significance of 8.5 sigma. The observed spectrum of the Crab Nebula is best fit with a power law above 6 TeV with a flux normalisation of $(3.20\pm0.42)\cdot10^{-10} TeV^{-1} cm^{-2} s^{-1})$ at a reference energy of 13 TeV and a spectral index of $-2.74\pm0.16$.

The transition region between the Sun's corona and chromosphere is important to the mass and energy transfer from the lower atmosphere to the corona; consequently, this region has been studied intensely with ultraviolet (UV) and extreme ultraviolet observations. A major result of these studies is that the amount of plasma at temperatures smaller than 100 000 K, is far too large to be compatible with the standard theory of thermal conductivity. However, it is not clear whether the disagreement lies with a problem in the observations or in the theory. We address this issue by analysing high-spatial and temporal resolution EUV observations from an X1.6-class flare taken with the Interface Region Imaging Spectrograph (IRIS) and the Solar Dynamic Observatory/Atmospheric Imaging Assembly (SDO/AIA). These data allow us to isolate the emission of flare loops from that of surrounding structures. We compare the Emission Measures (EMs) derived from the C II 1334.525Ang., Si IV 1402.770Ang transition region spectral lines, the Fe XXI 1354.066Ang flare line and the AIA 171Ang coronal images. We find that the EM ratios are incompatible with a standard conduction-dominated transition region model. Furthermore, the large increases in the EM magnitudes due to flare heating make it highly unlikely that the disagreement between data and theory is due to observational uncertainties in the source of the emission. We conclude that the standard Spitzer Harm thermal conductivity must be invalid for, at least, flare loops. We discuss the possibility that turbulent suppression of thermal conduction can account for our results.

Quasar feedback in the form of powerful outflows is invoked as a key mechanism to quench star formation in galaxies, although direct observational evidence is still scarce and debated. Here we present Early Release Science JWST NIRSpec IFU observations of the z=1.59 prototypical obscured quasar XID2028: this target represents a unique test case to study QSO feedback at the peak epoch of AGN-galaxy co-evolution thanks to its existing extensive multi-wavelength coverage and massive and extended outflow detected both in the ionised and molecular components. With the unprecedented sensitivity and spatial resolution of JWST, the NIRSpec dataset reveals a wealth of structures in the ionised gas kinematics and morphology previously hidden in the seeing-limited ground-based data. In particular, we find evidence of interaction between the interstellar medium of the galaxy and the QSO-driven outflow and radio jet, which is producing an expanding bubble from which the fast and extended wind detected in previous observations is emerging. The new observations confirm the complex interplay between the AGN jet/wind and the ISM of the host galaxy, highlighting the role of low luminosity radio jets in AGN feedback, and showcase the new window opened by NIRSpec on the detailed study of feedback at high redshift.

In this study, we estimate the fraction of binaries with high mass ratios for 202 open clusters in the extended solar neighbourhood (closer than 1.5 kpc from the Sun). This is one of the largest homogeneous catalogues of multiplicity fractions in open clusters to date, including the unresolved and total (close-binary) multiplicity fractions of main-sequence systems with mass ratio larger than $0.6_{-0.15}^{+0.05}$. The unresolved multiplicity fractions are estimated applying a flexible mixture model to the observed Gaia colour-magnitude diagrams of the open clusters. Then we use custom Gaia simulations to account for the resolved systems and derive the total multiplicity fractions. The studied open clusters have ages between 6.6 Myr and 3.0 Gyr and total high-mass-ratio multiplicity fractions between 6% and 80%, with a median of 18%. The multiplicity fractions increase with the mass of the primary star, as expected. The average multiplicity fraction per cluster displays an overall decreasing trend with the open cluster age up to ages about 100 Myr, above which the trend increases. Our simulations show that most of this trend is caused by complex selection effects (introduced by the mass dependence of the multiplicity fraction and the magnitude limit of our sample). Furthermore, the multiplicity fraction is not significantly correlated with the clusters' position in the Galaxy. The spread in multiplicity fraction decreases significantly with the number of cluster members (used as a proxy for cluster mass). We also find that the multiplicity fraction decreases with metallicity, in line with recent studies using field stars.

Meteoroids are pieces of asteroids and comets. They serve as unique probes to the physical and chemical properties of their parent bodies. We can derive some of these properties when meteoroids collide with the atmosphere of Earth and become a meteor or a bolide. Even more information can be obtained when meteoroids are mechanically strong and slow enough to drop meteorites. Through physical modeling of bright meteors, we describe their fragmentation in the atmosphere. We also derive their mechanical strength and the mass distribution of the fragments, some of which may hit the ground as meteorites. We developed a semi-automatic program for meteoroid fragmentation modeling using parallel genetic algorithms. This allowed us to determine the most probable fragmentation cascade of the meteoroid, and also to specify its initial mass and velocity. These parameters can be used in turn to derive the heliocentric orbit of the meteoroid and to place constraints on its likely age as a separate object. The program offers plausible solutions for the majority of fireballs we tested, and the quality of the solutions is comparable to that of manual solutions. The two solutions are not the same in detail, but the derived quantities, such as the fragment masses of the larger fragments and the proxy for their mechanical strength, are very similar. With this method, we would like to describe the mechanical properties and structure of both meteoroids belonging to major meteor showers and those that cause exceptional fireballs.

The Hubble tension, revealed by a $\sim 5\sigma$ discrepancy between measurements of the Hubble-Lemaitre constant from early- and local-Universe observations, is one of the most significant problems in modern cosmology. In order to better understand the origin of this mismatch, independent techniques to measure $H_0$, such as strong lensing time delays, are required. Notably, the sample size of such systems is key to minimising statistical uncertainties and cosmic variance, which can be improved by exploring the datasets of large-scale sky surveys like DESI (Dark Energy Spectroscopic Instrument). We identify possible strong lensing time-delay systems within DESI by selecting candidate multiply imaged lensed quasars from a catalogue of 24,440,816 candidate QSOs contained in the 9th data release of the DESI Legacy Imaging Surveys (DESI-LS). Using a friend-of-friends-like algorithm on spatial co-ordinates, our method generates an initial list of compact quasar groups. This list is subsequently filtered using a measure of the similarity of colours of a group's members and the likelihood that they are quasars. A visual inspection finally selects candidate strong lensing systems based on the spatial configuration of the group members. We identify 620 new candidate multiply imaged lensed quasars (101 Grade-A, 214 Grade-B, 305 Grade-C). This number excludes 53 known spectroscopically confirmed systems and existing candidate systems identified in other similar catalogues. When available, these new candidates will be further checked by combining the spectroscopic and photometric data from DESI. The catalogues and images of the candidates in this work are available online (https://github.com/EigenHermit/lensed_qso_cand_catalogue_He-22/).

Broad-band observations of the solar photosphere began in Meudon in 1875 under the auspices of Jules Janssen. For his part, Henri Deslandres initiated imaging spectroscopy in 1892 at Paris observatory. He invented, concurrently with George Hale in Kenwood (USA) but quite independently, the spectroheliograph designed for monochromatic imagery of the solar atmosphere. Deslandres developed two kinds of spectrographs: the ''spectroh{\'e}liographe des formes'', i.e. the narrow bandpass instrument to reveal chromospheric structures (such as filaments, prominences, plages and active regions); and the ''spectroh{\'e}liographe des vitesses'', i.e. the section spectroheliograph to record line profiles of cross sections of the Sun with a 20''-30'' spatial step. This second apparatus was intended to measure the velocities (more exactly the Dopplershifts) of dynamic features. Deslandres moved to Meudon in 1898 with his instruments and tested various combinations, in order to improve the spectral and spatial resolutions, leading to the final large quadruple spectroheliograph in 1908. CaII K systematic observations started at this date and were followed in 1909 by H$\alpha$. The service was organized by Lucien d'Azambuja and continues today. Optical and mechanical parts were revisited in 1989 and the digital technology was introduced in 2002. Full line profiles are registered for all pixels of the Sun since 2018, so that the instrument produces now data-cubes. The collection is one of the longest available (more than 100 000 observations). It contains sporadic images from 1893 to 1907 (during the development phase) and systematic observations along 10 solar cycles since 1908, in H$\alpha$ and CaII K lines. This paper summarizes 130 years of observations, instrumental research and technical advances.

In this study, a W Ursae Majoris (W UMa) type system LO Andromedae (LO And) was observed over nine nights at Durham to fully investigate its physical properties and update its stellar parameters. After obtaining the observational data in both V-filter and B-filter, the Gaia CCD images of LO And were extracted from the Astrolab internal archive using Linux commands. By applying the "Nightfall" program and local Python scripts, the calibrated light curves of LO And can be plotted, phase-folded, and fitted to derive the period of this system as $0.3804573 \pm 0.0000482\, \mathrm{d}$. Then, 2D chi-squared heat maps were illustrated to determine LO And's best-fit stellar parameters and estimate their uncertainties, including the mass ratio $q = 0.371 \pm 0.207$, the inclination $i = 78.5 \pm 3.8\, \mathrm{deg}$, the primary temperature $T_1 = 6290 \pm 358\, \mathrm{K}$, the secondary temperature $T_2 = 6449 \pm 445\, \mathrm{K}$, and two fill factors $f_1 = f_2 = 1.02258$. In addition, the "Nightfall" program built the 3D models and evaluated the spot distribution parameters to visualize the configuration of LO And. There were seven new eclipsing timings added in this study to reconstruct the O-C diagram together with LO And's previous observational data. It was clearly found that the period of LO And is currently undergoing an accelerated increase with a change rate $d\mathrm{P}/d\mathrm{t} = 2.27 \times 10^{-7}\, \mathrm{day\, yr^{-1}}$, which was attributed to the mass transfer in this system with a transfer rate $dM_1/d\mathrm{t} = 1.43 \times 10^{-7}\, \mathrm{M_\odot\, yr^{-1}}$ and the light time effect caused by the possible existence of a third star $M_3 = 0.224\, M_\odot$ orbiting around LO And.

We present extensive optical photometry of the afterglow of GRB 221009A. Our data cover $0.9 - 59.9$ days from the time of Swift and Fermi GRB detections. Photometry in $rizy$-band filters was collected primarily with Pan-STARRS and supplemented by multiple 1- to 4-meter imaging facilities. We analyzed the Swift X-ray data of the afterglow and found a single decline rate power-law $f(t) \propto t^{-1.556\pm0.002}$ best describes the light curve. In addition to the high foreground Milky Way dust extinction along this line of sight, we find a further 0.8 magnitudes of extinction in the optical is required to consistently model the optical to X-ray flux with optically thin synchrotron emission. We fit the X-ray-derived power-law to the optical light curve and find good agreement with the measured data up to $5-6$ days. Thereafter we find a flux excess in the $riy$ bands which peaks in the observer frame at $\sim20$ days. This excess shares similar light curve profiles to the type Ic broad-lined supernovae SN 2016jca and SN 2017iuk once corrected for the GRB redshift of $z=0.151$ and arbitrarily scaled. We propose this is representative of a supernova emerging from the declining afterglow (named SN 2022xiw). We measure rest-frame absolute peak AB magnitudes of $M_g=-19.8\pm0.6$ and $M_r=-19.5\pm0.3$ and $M_z=-20.1\pm0.3$. Bayesian modelling of the supernova flux of SN 2022xiw leads to estimated explosion parameters of $M_{\rm ej}=7.1^{+2.4}_{-1.7}$ M$_{\odot}$, $M_{\rm Ni}=1.0^{+0.6}_{-0.4}$ M$_{\odot}$, and $v_{\rm ej}=33,900^{+5,900}_{-5,700}$ $kms^{-1}$ for the ejecta mass, nickel mass and ejecta velocity respectively, inferring an explosion energy of $E_{\rm kin}\simeq 2.6-9.0\times10^{52}$ ergs.

X-ray observations of galaxy clusters are impacted by the presence of active galactic nuclei (AGN) in a manner that is challenging to quantify, leading to biases in the detection and measurement of cluster properties for both astrophysics and cosmological applications. Using automated X-ray pipeline techniques, we introduce a new automated class for AGN-contaminated (AC) clusters in the XXL source detection software. The majority of these systems are otherwise missed by current X-ray cluster detection methods. The AC selection is also effective at distinguishing AGN and cool core presence using supplementary optical and infrared information. We present 33 AC objects, consisting of 25 clusters in the redshift range, $0.14 \leq z \leq 1.03$, and 8 other sources with significantly peaked central emission based on X-ray observations. Six of these are new confirmed clusters. We compute the missed fraction of the XXL survey, defined as the fraction of genuine clusters that are undetected due to their centrally peaked X-ray profiles. We report seven undetected AC clusters above $z > 0.6$, in the range where X-ray cluster detection efficiency drops significantly. The missed fraction is estimated to be at the level of $5\%$ for the 50 square degree XXL area. The impact on cosmological estimates from missed clusters is negligible for XXL, but produces a $\sim 3\sigma$ tension with the fiducial cosmology when considering larger survey areas. This work demonstrates the first systematic attempt to quantify the percentage of missed clusters in X-ray surveys as a result of central AGN contamination. Looking towards surveys such as eROSITA and Athena, larger areas and increased sensitivity will significantly enhance cluster detection, therefore robust methods for characterising AGN contamination will be crucial for precise cluster cosmology, particularly in the redshift $z > 1$ regime.

Tension between cosmic microwave background-based and distance ladder-based determinations of the Hubble constant H0 motivates pursuit of independent methods that are not subject to the same systematic effects. A promising alternative, proposed by Refsdal in 1964, relies on the inverse scaling of H0 with the delay between the arrival times of at least two images of a strongly-lensed variable source such as a quasar. To date, Refsdal's method has mostly been applied to quasars lensed by individual galaxies rather than by galaxy clusters. Using the three quasars strongly lensed by galaxy clusters (SDSS J1004+4112, SDSS J1029+2623, and SDSS J2222+2745) that have both multiband Hubble Space Telescope data and published time delay measurements, we derive H0, accounting for the systematic and statistical sources of uncertainty. While a single time delay measurement does not yield a well-constrained H0 value, analyzing the systems together tightens the constraint. Combining the six time delays measured in the three cluster-lensed quasars gives H0 = 71.5 +/- 6.1 km/s/Mpc. To reach 1% uncertainty in H0, we estimate that a sample size of order of 500 time delay measurements of similar quality as those from SDSS J1004+4112, SDSS J1029+2623, and SDSS J2222+2745 would be needed. Improving the lens modeling uncertainties by a factor of two may reduce the needed sample size to 120 time delays, potentially reachable in the next decade.

We characterize the peculiar velocity field of the local large-scale structure reconstructed from the $2M++$ survey, by treating it as a fluid, extracting the gradient and the divergence via different approximations. This reconstructed field is important for cosmology, since it was used to correct the peculiar redshifts of the last SNIA compilation Pantheon+. We conclude that the local velocity field can be described on average as a slightly contracting fluid, with intriguing implications for the ``Tilted Cosmology'' model. We compute representative values of the apparent deceleration parameter ($\tilde{q}$) measured by observers inside the contracting region, in order to compare our results with the theoretical predictions of the tilted-universe scenario. As predicted, the computed values are found to be negative on a range of averaged scales, allowing for a possible explanation of dark energy as an effect induced by our peculiar motion relative to the universal expansion.

We present new observations of sixteen bright ($r=19-21$) gravitationally lensed galaxies at $z\simeq 1-3$ selected from the CASSOWARY survey. Included in our sample is the $z=1.42$ galaxy CSWA-141, one of the brightest known reionization-era analogs at high redshift (g=20.5), with a large sSFR (31.2 Gyr$^{-1}$) and an [OIII]+H$\beta$ equivalent width (EW$_{\rm{[OIII]+H\beta}}$=730~\r{A}) that is nearly identical to the average value expected at $z\simeq 7-8$. In this paper, we investigate the rest-frame UV nebular line emission in our sample with the goal of understanding the factors that regulate strong CIII] emission. Whereas most of the sources in our sample show weak UV line emission, we find elevated CIII] in the spectrum of CSWA-141 (EW$_{\rm{CIII]}}$=4.6$\pm1.9$~\r{A}) together with detections of other prominent emission lines (OIII], Si III], Fe II$^\star$, Mg II). We compare the rest-optical line properties of high redshift galaxies with strong and weak CIII] emission, and find that systems with the strongest UV line emission tend to have young stellar populations and nebular gas that is moderately metal-poor and highly ionized, consistent with trends seen at low and high redshift. The brightness of CSWA-141 enables detailed investigation of the extreme emission line galaxies which become common at $z>6$. We find that gas traced by the CIII] doublet likely probes higher densities than that traced by [OII] and [SII]. Characterisation of the spectrally resolved Mg II emission line and several low ionization absorption lines suggests neutral gas around the young stars is likely optically thin, potentially facilitating the escape of ionizing radiation.

Focal plane wavefront sensing and control is a critical approach to reducing non-common path errors between the a conventional astronomical adaptive optics (AO) wavefront sensor (WFS) detector and science camera. However, in addition to mitigating non-common path errors, recent focal plane wavefront sensing techniques have been developed to operate at speeds fast enough to enable "multi-WFS" AO, where residual atmospheric errors are further corrected by a focal plane WFS. Although a number of such techniques have been recently developed for coronagraphic imaging, here we present one designed for non-coronagraphic imaging. Utilizing conventional AO system components, this concept additionally requires (1) a detector imaging the focal plane of the WFS light source and (2) a pupil plane optical chopper device that is non-common path to the first WFS and is synchronized to the focal plane imager readout. These minimal hardware requirements enable the temporal amplitude modulation to resolve the sine ambiguity of even wavefront modes for both low, mid, and high wavefront spatial frequencies. Similar capabilities have been demonstrated with classical phase diversity by defocusing the detector, but such techniques are incompatible with simultaneous science observations. This optical chopping technique, however, enables science imaging at up to a 50% duty cycle. We present both simulations and laboratory validation of this concept on SEAL, the Santa Cruz Extreme AO Laboratory testbed.

We provide line luminosities and spectroscopic templates of prominent optical emission lines of 133 Galactic Wolf-Rayet stars by exploiting Gaia DR3 parallaxes and optical spectrophotometry, and provide comparisons with 112 counterparts in the Magellanic Clouds. Average line luminosities of the broad blue (He II 4686, C III 4647,51, N III 4634,41, N V 4603,20) and yellow (C IV 5801,12) emission features for WN, WN/C, WC and WO stars have application in characterising the Wolf-Rayet populations of star-forming regions of distant, unresolved galaxies. Early-type WN stars reveal lower line luminosities in more metal poor environments, but the situation is less clear for late-type WN stars. LMC WC4-5 line luminosities are higher than their Milky Way counterparts, with line luminosities of Magellanic Cloud WO stars higher than Galactic stars. We highlight other prominent optical emission lines, N IV 3478,85 for WN and WN/C stars, O IV 3403,13 for WC and WO stars and O VI 3811,34 for WO stars. We apply our calibrations to representative metal-poor and metal-rich WR galaxies, IC 4870 and NGC 3049, respectively, with spectral templates also applied based on a realistic mix of subtypes. Finally, the global blue and C IV 5801,12 line luminosities of the Large (Small) Magellanic Clouds are 2.6e38 erg/s (9e36 erg/s) and 8.8e37 erg/s (4e36 erg/s), respectively, with the cumulative WR line luminosity of the Milky Way estimated to be an order of magnitude higher than the LMC.

Solar radio bursts generated through the plasma emission mechanism produce radiation near the local plasma frequency (fundamental emission) and double the plasma frequency (harmonic). While the theoretical ratio of these two frequencies is close to 2, simultaneous observations give ratios ranging from 1.6 to 2, suggesting either a ratio different from 2, a delay of the fundamental emission, or both. To address this long-standing question, we conducted high frequency, high time resolution imaging spectroscopy of type III and type J bursts with fine structures for both the fundamental and harmonic components with LOFAR between 30 and 80 MHz. The short-lived and narrow frequency-band fine structures observed simultaneously at fundamental and harmonic frequencies give a frequency ratio of 1.66 and 1.73, similar to previous observations. However, frequency-time cross-correlations suggest a frequency ratio of 1.99 and 1.95 with a time delay between the F and H emissions of 1.00 and 1.67 s, respectively for each event. Hence, simultaneous frequency ratio measurements different from 2 are caused by the delay of the fundamental emission. Among the processes causing fundamental emission delays, anisotropic radio-wave scattering is dominant. Moreover, the levels of anisotropy and density fluctuations reproducing the delay of fundamental emissions are consistent with those required to simulate the source size and duration of fundamental emissions. Using these simulations we are able to, for the first time, provide quantitative estimates of the delay time of the fundamental emissions caused by radio-wave propagation effects at multiple frequencies, which can be used in future studies.

Terrestrial exoplanets in habitable zones are ubiquitous. It is, however, unknown which have Earth-like or Venus-like climates. Distinguishing different planet-types is crucial for determining whether a planet could be habitable. We investigate the potential of polarimetry for distinguishing exo-Earths from exo-Venuses. We present computed fluxes and polarisation of starlight that is reflected by exoplanets with atmospheres in evolutionary states from current Earth to current Venus, with cloud compositions ranging from pure water to 0.75 sulfuric acid solution, for wavelengths between 0.3 and 2.5 microns. The polarisation of the reflected light shows larger variations with the planetary phase angle than the total flux. Across the visible, the largest polarisation is reached for an Earth-like atmosphere with water clouds, due to Rayleigh scattering above the clouds and the rainbow near 40 deg phase angle. In the near-infrared, the planet with a Venus-like CO2 atmosphere and thin water clouds shows the most prominent polarisation features due to scattering by the small cloud droplets. A planet around Alpha Centauri A would leave temporal variations on the order of 10E-13 W/m3 in the reflected flux and 10E-11 in the degree of polarisation along the planet's orbit for a spatially unresolved star-planet system. Star-planet contrasts are on the order of 10E-10. Current polarimeters cannot distinguish between the possible evolutionary phases of spatially unresolved terrestrial exoplanets, as a sensitivity near 10E-10 is required to discern the planet signal on the background of unpolarised starlight. Telescopes capable of reaching planet-star contrasts lower than 10E-9 should be able to observe the variation of the planet's resolved degree of polarisation as a function of its phase angle and thus to discern an exo-Earth from an exo-Venus based on its clouds' unique polarisation signatures.

We report results from the first radiative particle-in-cell simulations of turbulence in plasmas of moderate optical depth. The simulations self-consistently follow the evolution of radiation as it interacts with the turbulent plasma via Compton scattering. Under conditions expected in magnetized coronae of accreting black holes, we obtain an emission spectrum consistent with the observed hard state of Cyg X-1 and find that most of the emitted power comes from Comptonization by the bulk turbulent motions. The method presented here shows promising potential for \emph{ab initio} modeling of various high-energy astrophysical sources and opens a window into a new regime of kinetic plasma turbulence.

Using lattice simulations we calculate the rate of baryon number violating processes, the sphaleron rate, in the Standard Model with an external (hyper)magnetic field for temperatures across the electroweak cross-over, focusing on the broken phase. Additionally, we compute the Higgs expectation value and the pseudocritical temperature. The electroweak cross-over shifts to lower temperatures with increasing external magnetic field, bringing the onset of the suppression of the baryon number violation with it. When the hypermagnetic field reaches the magitude $B_Y \approx 2 T^2$ the cross-over temperature is reduced from $160$ GeV to $145$ GeV. In the broken phase for small magnetic fields the rate behaves quadratically as a function of the magnetic flux. For stronger magnetic fields the rate reaches a linear regime which lasts until the field gets strong enough to restore the electroweak symmetry where the symmetric phase rate is reached.

We investigate how the speed of gravitational waves, $c_{GW}$, can be tested by upcoming black hole ringdown observations. We do so in the context of hairy black hole solutions, where the hair is associated with a new scalar degree of freedom, forecasting that LISA and TianQin will be able to constrain deviations of $c_{GW}$ from the speed of light at the ${\cal O}(10^{-4})$ level from a single supermassive black hole merger. We discuss how these constraints depend on the nature of the scalar hair, what different aspects of the underlying physics they are sensitive to in comparison with constraints derived from gravitational wave propagation effects, which observable systems will place the most stringent bounds, and that constraints are expected to improve by up to two orders of magnitude with multiple observations. This is especially interesting for dark energy-related theories, where existing bounds from GW170817 need not apply at lower frequencies and where upcoming bounds from lower-frequency missions will therefore be especially powerful. As such, we also forecast analogous bounds for the intermediate-frequency AEDGE and DECIGO missions. Finally, we discuss and forecast analogous black hole ringdown constraints at higher frequencies (so from LVK, the Einstein Telescope and Cosmic Explorer) and in what circumstances they can yield new information on top of existing constraints on $c_{GW}$. All calculations performed in this paper are reproducible via a companion Mathematica notebook.

Recently, it has been shown that the presence of a non-instantaneous era of reheating can significantly alter the charged lepton(s) equilibration temperature(s) which plays important role in flavor leptogenesis. In this work, we extend the analysis to a more general situation where RHNs are also produced from the decay of the inflaton. The presence of these RHNs along with the thermally generated ones (above its mass equivalent temperature only) redistributes different components of the energy density of the Universe during this reheating era, thereby affecting the charged lepton equilibration temperature (in addition to the Hubble effect) as well as the final reheating temperature $T_{\rm{RH}}$. Taking both the effects into account, we find that the decay of the lightest RHN in the set-up not only provides a platform to study flavor leptogenesis during reheating, but also an interesting paradigm of $quasi$-thermal leptogenesis emerges.

A dark photon is a hypothetical particle that is similar to a photon with a small mass and interact very weakly with ordinary matter through a kinetic mixing with ordinary photon. In this paper, we propose a new way to probe the existence of dark photons through the Bremsstrahlung effect on ultra-high-energy cosmic rays (UHECRs). Using the standard soft photon calculation, we demonstrate that the dark photon Bremsstrahlung process could lead to significant energy loss for protons in the ultralight dark photon scenario, and that this effect could be tested against observational data of UHECRs. We also provide exclusion limits which can be compared with existing limits on ultralight dark photons.

Scale-independent EMSG is a particular model of energy-momentum squared gravity (EMSG) in which the new terms in the Einstein field equations arising from the EMSG theory enter with the same power as the usual terms from Einstein-Hilbert part of the action. However, the model violates the local energy-momentum conservation and matter-current conservation in general and hence, permits a process of matter creation/annihilation in an expanding universe. Consequently, the scale factor dependencies of the energy densities are modified by the dimensionless model parameter $\alpha$. We revisit some nostalgias such as static universes and de Sitter/steady state universes. We reproduce the original ones, moreover, present some novelties, e.g., a spatially flat static universe, de Sitter expansion by negative vacuum energy, steady state universes in the presence of arbitrary fluids other than dust, etc. We also investigate the possible dynamics of dust dominated and radiation dominated universes. Depending on the value of $\alpha$, dust/radiation dominated universe exhibits power-law accelerated/decelerated expansion, corresponds to a steady state model or may end in a big rip. In the framework of anisotropic cosmology, we reproduce Barrow's quiescent universe in the presence of stiff fluid and extend it to fluids with arbitrary equation of state (EoS) parameter. We also relax the condition for isotropic initial singularity (big bang) owing to that EMSG effectively allows ultra-stiff EoS parameters.

The interaction between gravitational waves (GW) and electromagnetic waves (EMW) produces quadrirefringence, a phenomenon consisting in a frequency and polarization dependency of the speed of GW and EMW. Quadrirefringence can be due to the GW-EMW interaction in the source or during the propagation from the source to the observer. In the first case the astrophysical properties of the source can induce a unique characteristic imprint on GW and EMW for each source, the binaries rainbow, which could be observed in systems with EM counterparts, such as neutron stars or neutron star black hole binaries. Quadrirefringence could be used for example to investigate the equation of state or neutron starts, while its effect on the propagation from the source could be used to probe the large scale electromagnetic field using GW. The interaction of the graviton with other fields will also induce similar effects, and will allow to probe other fields using GW observations.