Papers for Wednesday, Jan 04 2023

Inspired by the combinatorial algebraic approach proposed by Dhurandhar et al., we propose two novel classes of second-generation time-delay interferometry (TDI) solution as well as their further generalization. The primary strategy of the algorithm is to enumerate specific types of residual laser frequency noise associated with second-order commutators in products of time-displacement operators. The derivations are based on analyzing the delay time residual when expanded in time derivatives of the armlengths order by order. It is observed that the solutions obtained by such a scheme are primarily captured by the geometric TDI approach and therefore possess an intuitive interpretation. Nonetheless, the fully-symmetric Sagnac and Sagnac-inspired combinations inherit the properties from the original algebraic approach, and subsequently lie outside of the scope of geometric TDI. Moreover, at its lowest order, the solution is furnished by commutator of rather compact form. Besides the original Michelson-type solution, we elaborate on other types of solutions such as the Monitor, Beacon, Relay, Sagnac, fully-symmetric Sagnac, and Sagnac-inspired ones. The average response functions, residual noise power spectral density, and sensitivity curves are evaluated for the obtained solutions. Also, the relations between the present scheme and other existing algorithms are discussed.

The Gaia satellite is cataloging the astrometric properties of an unprecedented number of stars in the Milky Way with extraordinary precision. This provides a gateway for conducting extensive surveys of transient astrometric lensing events caused by dark compact objects. In this work, we establish a data analysis pipeline capable of searching for such events in the upcoming Gaia data release 4 (DR4). We use Gaia early data release 3 (EDR3) and current dark matter and astrophysical black hole population models to create mock DR4 catalogs containing stellar trajectories perturbed by lensing. Our analysis of these mock catalogs suggests that Gaia DR4 is expected to contain about 4 astrometric lensing events from astrophysical black holes at a 5 sigma significance level. Furthermore, we project that our data analysis pipeline applied to Gaia DR4 will result in leading constraints on compact dark matter in the mass range $1$-$10^3~M_\odot$ down to a dark matter fraction of about one percent.

We present the ionised gas outflow morphology in the Circinus galaxy using the Narrow Field Mode (NFM) of the MUSE instrument on board the Very Large Telescope (VLT). The NFM observations provide a spatial resolution of $\sim$0.1", corresponding to a physical scale of $\sim$2 pc, one of the highest spatial resolution achievable using ground-based AO-assisted observations in the optical wavelengths. The MUSE observations reveal a collimated clumpy outflow profile originating near the AGN location and extending up to 1.5" ($\sim$30 pc) in the NW direction. The collimated structure then fragments into two filaments, giving the entire outflowing gas a ``tuning-fork'' morphology. These structures remain undetected in the lower spatial resolution MUSE Wide Field Mode data. We explain the origin of this tuning-fork structure to the interaction of the outflow with a dense clump in the interstellar medium (ISM) as the outflow propagates outward. The origin of the collimated structure itself could be from jet-ISM interactions on small scales. These observations also provide evidence to the origin of the ionised gas filaments previously observed in the Circinus galaxy out to kiloparsec scales. We find instantaneous and time-averaged mass outflow rates of 10$^{-2}$ M$_{\odot}$ yr$^{-1}$ and 10$^{-4}$ M$_{\odot}$ yr$^{-1}$, respectively. Based on the star formation rate in the Circinus galaxy reported in the literature, the observed ionised outflows are not expected to regulate star formation within the $\sim$100 pc scales probed by the NFM data.

Molecular hydrogen allows cooling in primordial gas, facilitating its collapse into Population III stars within primordial halos. Lyman-Werner (LW) radiation from these stars can escape the halo and delay further star formation by destroying H$_2$ in other halos. As cosmological simulations show that increasing the background LW field strength increases the average halo mass required for star formation, we perform follow-up simulations of selected halos to investigate the knock-on effects this has on the Population III IMF. We follow 5 halos for each of the $J_{21}$ = 0, 0.01 and 0.1 LW field strengths, resolving the pre-stellar core density of $10^{-6}$ g cm$^{-3}$ (10$^{18}$ cm$^{-3}$) before inserting sink particles and following the fragmentation behaviour for hundreds of years further. We find that the mass accreted onto sinks by the end of the simulations is proportional to the mass within the $\sim 10^{-2}$ pc molecular core, which is not correlated to the initial mass of the halo. As such, the IMF shows little dependence on the LW strength. As the range of background LW field strengths tested here covers the most likely values from literature, we conclude that the IMF for so-called Pop III.2 stars is not significantly different from the initial population of Pop III.1 stars. The primordial IMF therefore likely remains unchanged until the formation of the next generation of Population II stars.

We present a multi-wavelength analysis of the galaxy cluster SPT-CL J0607-4448 (SPT0607), which is one of the most distant clusters discovered by the South Pole Telescope (SPT) at $z=1.4010\pm0.0028$. The high-redshift cluster shows clear signs of being relaxed with well-regulated feedback from the active galactic nucleus (AGN) in the brightest cluster galaxy (BCG). Using Chandra X-ray data, we construct thermodynamic profiles and determine the properties of the intracluster medium. The cool core nature of the cluster is supported by a centrally-peaked density profile and low central entropy ($K_0=18_{-9}^{+11}$ keV cm$^2$), which we estimate assuming an isothermal temperature profile due to the limited spectral information given the distance to the cluster. Using the density profile and gas cooling time inferred from the X-ray data, we find a mass cooling rate of $\dot{M}_\mathrm{cool}=100_{-60}^{+90}~M_\odot$ yr$^{-1}$. From optical spectroscopy and photometry around the [O II] emission line, we estimate that the BCG star formation rate is SFR$_\mathrm{[O~II]}=1.7_{-0.6}^{+1.0}~M_\odot$ yr$^{-1}$, roughly two orders of magnitude lower than the predicted mass cooling rate. In addition, using ATCA radio data at 2.1 GHz, we measure a radio jet power of $P_\mathrm{cav}=3.2_{-1.3}^{+2.1}\times10^{44}$ erg s$^{-1}$, which is consistent with the X-ray cooling luminosity ($L_\mathrm{cool}=1.9_{-0.5}^{+0.2}\times10^{44}$ erg s$^{-1}$ within $r_\mathrm{cool}=43$ kpc). These findings suggest that SPT0607 is a relaxed, cool core cluster with AGN-regulated cooling at an epoch shortly after cluster formation, implying that the balance between cooling and feedback can be reached quickly. We discuss implications for these findings on the evolution of AGN feedback in galaxy clusters.

Several features in the mass spectrum of merging binary black holes (BBHs) have been identified using data from the Third Gravitational Wave Transient Catalog (GWTC-3). These features are of particular interest as they may encode the uncertain mechanism of BBH formation. We determine if the identified features are statistically significant or the result of Poisson noise due to a finite number of observations. We simulate realistic catalogs of BBHs whose underlying distribution does not have the features of interest, apply the analysis previously performed on GWTC-3, and determine how often such features are spuriously found. We find that two of the features found in GWTC-3, the peaks at $\sim10\,M_{\odot}$ and $\sim35\,M_{\odot}$, cannot be explained by Poisson noise alone: peaks as significant occur in $<0.33\%$ of catalogs generated from a featureless population. These features are therefore likely to be of astrophysical origin. However, additional structure beyond a power law, such as the purported dip at $\sim14\,M_{\odot}$, can be explained by Poisson noise. We provide a publicly-available package, GWMockCat, that creates simulated catalogs of BBH events with realistic measurement uncertainty and selection effects according to user-specified underlying distributions and detector sensitivities.

The heating and acceleration of the solar wind remains one of the fundamental unsolved problems in heliophysics. It is usually observed that the proton temperature $T_i$ is highly correlated with the solar wind speed $V_{SW}$, while the electron temperature $T_e$ shows anti-correlation or no clear correlation with the solar wind speed. Here we inspect both Parker Solar Probe (PSP) and WIND data and compare the observations with simulation results. PSP observations below 30 solar radii clearly show a positive correlation between proton temperature and wind speed and a negative correlation between electron temperature and wind speed. One year (2019) of WIND data confirm that proton temperature is positively correlated with solar wind speed, but the electron temperature increases with the solar wind speed for slow wind while it decreases with the solar wind speed for fast wind. Using a one-dimensional Alfv\'en-wave-driven solar wind model with different proton and electron temperatures, we for the first time find that if most of the dissipated Alfv\'en wave energy heats the ions instead of electrons, a positive $T_i-V_{SW}$ correlation and a negative $T_e-V_{SW}$ correlation arise naturally. If the electrons gain a small but finite portion of the dissipated wave energy, the $T_e-V_{SW}$ correlation evolves with radial distance to the Sun such that the negative correlation gradually turns positive. The model results show that Alfv\'en waves are one of the possible explanations of the observed evolution of proton and electron temperatures in the solar wind.

We present maps of the 3.3 micron polycyclic aromatic hydrocarbon (PAH) emission feature in NGC 628, NGC 1365, and NGC 7496 as observed with the Near-Infrared Camera (NIRCam) imager on JWST from the PHANGS-JWST Cycle 1 Treasury project. We create maps that isolate the 3.3 micron PAH feature in the F335M filter (F335M$_{\rm PAH}$) using combinations of the F300M and F360M filters for removal of starlight continuum. This continuum removal is complicated by contamination of the F360M by PAH emission and variations in the stellar spectral energy distribution slopes between 3.0 and 3.6 micron. We modify the empirical prescription from Lai et al. (2020) to remove the starlight continuum in our highly resolved galaxies, which have a range of starlight- and PAH-dominated lines-of-sight. Analyzing radially binned profiles of the F335M$_{\rm PAH}$ emission, we find that between 5-65% of the F335M intensity comes from the 3.3 micron feature within the inner 0.5 $r_{25}$ of our targets. This percentage systematically varies from galaxy to galaxy, and shows radial trends within the galaxies related to each galaxy's distribution of stellar mass, interstellar medium, and star formation. The 3.3 micron emission is well correlated with the 11.3 micron PAH feature traced with the MIRI F1130W filter, as is expected, since both features arise from C-H vibrational modes. The average F335M$_{\rm PAH}$/F1130W ratio agrees with the predictions of recent models by Draine et al. (2021) for PAHs with size and charge distributions shifted towards larger grains with normal or higher ionization.

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PHANGS-JWST mid-infrared (MIR) imaging of nearby spiral galaxies has revealed ubiquitous filaments of dust emission in intricate detail. We present a pilot study to systematically map the dust filament network (DFN) at multiple scales between 25-400 pc in NGC 628. MIRI images at 7.7, 10, 11.3 and 21$\mu$m of NGC 628 are used to generate maps of the filaments in emission, while PHANGS-HST B-band imaging yields maps of dust attenuation features. We quantify the correspondence between filaments traced by MIR thermal continuum / polycyclic aromatic hydrocarbon (PAH) emission and filaments detected via extinction / scattering of visible light; the fraction of MIR flux contained in the DFN; and the fraction of HII regions, young star clusters and associations within the DFN. We examine the dependence of these quantities with the physical scale at which the DFN is extracted. With our highest resolution DFN maps (25 pc filament width), we find that filaments in emission and attenuation are co-spatial in 40% of sight lines, often exhibiting detailed morphological agreement; that ~30% of the MIR flux is associated with the DFN; and that 75-80% of HII regions and 60% of star clusters younger than 5 Myr are contained within the DFN. However, the DFN at this scale is anti-correlated with looser associations of stars younger than 5 Myr identified using PHANGS-HST near-UV imaging. We discuss the impact of these findings for studies of star formation and the ISM, and the broad range of new investigations enabled with multi-scale maps of the DFN.

We present EUV solar observations showing evidence for omnipresent jetting activity driven by small-scale magnetic reconnection at the base of the solar corona. We argue that the physical mechanism that heats and drives the solar wind at its source is ubiquitous magnetic reconnection in the form of small-scale jetting activity (i.e., a.k.a. jetlets). This jetting activity, like the solar wind and the heating of the coronal plasma, are ubiquitous regardless of the solar cycle phase. Each event arises from small-scale reconnection of opposite polarity magnetic fields producing a short-lived jet of hot plasma and Alfv\'en waves into the corona. The discrete nature of these jetlet events leads to intermittent outflows from the corona, which homogenize as they propagate away from the Sun and form the solar wind. This discovery establishes the importance of small-scale magnetic reconnection in solar and stellar atmospheres in understanding ubiquitous phenomena such as coronal heating and solar wind acceleration. Based on previous analyses linking the switchbacks to the magnetic network, we also argue that these new observations might provide the link between the magnetic activity at the base of the corona and the switchback solar wind phenomenon. These new observations need to be put in the bigger picture of the role of magnetic reconnection and the diverse form of jetting in the solar atmosphere.

We present a 0.3--4.5 $\mu$m 16-band photometric catalog for the Spitzer/HETDEX Exploratory Large-Area (SHELA) survey. SHELA covers a $\sim 27$ deg$^2$ field within the footprint of the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). Here we present new DECam imaging and a $rizK_s$-band-selected catalog of four million sources extracted using a fully model-based approach. We validate our photometry by comparing with the model-based DECam Legacy Survey. We analyze the differences between model-based and aperture photometry by comparing with the previous SHELA catalog, finding that our model-based photometry can measure point sources to fainter fluxes and better capture the full emission of resolved sources. The catalog is $80\%$ ($50\%$) complete at $riz \sim 24.7$ ($25.1$) AB mag, and the optical photometry reaches a $5\sigma$ depth of $\sim 25.5$ AB mag. We measure photometric redshifts and achieve $1\sigma$ scatter of $\Delta z/(1+z)$ of 0.04 with available spectroscopic redshifts at $0 \le z \le 1$. This large area, multi-wavelength photometric catalog, combined with spectroscopic information from HETDEX, will enable a wide range of extragalactic science investigations.

Long-duration GRB~200829A was detected by Fermi-GBM and Swift-BAT/XRT, and then rapidly observed by other ground-based telescopes. It has a weak $\gamma$-ray emission in the very early phase and followed by a bright spiky $\gamma$-ray emission pulse. The radiation spectrum of the very early emission is best fitted by a power-law function with index $\sim -1.7$. However, the bright spiky $\gamma$-ray pulse, especially the time around the peak, exhibits a distinct two-component radiation spectra, i.e., Band function combined with a blackbody radiation spectrum. We infer the photospheric properties and reveal a medium magnetization at photospheric position by adopting the initial size of the outflow as $r_0=10^9$~cm. It implies that Band component in this pulse may be formed during the dissipation of magnetic field. The power-law radiation spectra found in the very early prompt emission may imply the external-shock origination of this phase. Then, we perform Markov Chain Monte Carlo method fitting on the light-curves of this burst, where the jet corresponding to the $\gamma$-ray pulses at around $20$~s is used to refresh the external-shock. It is shown that the light-curves of very early phase and X-ray afterglow after $40$~s, involving the X-ray bump at around $100$~s, can be well modelled in the external-shock scenario. For the obtained initial outflow, we estimate the minimum magnetization factor of the jet based on the fact that the photospheric emission of this jet is missed in the very early phase.

We use the single-dish radio telescope FAST to map the HI in the tidally interacting NGC 4631 group with a resolution of 3.24$'$ (7 kpc), reaching a 5-$\sigma$ column density limit of $10^{17.9}$ cm$^{-2}$ assuming a line width of 20 km s$^{-1}$. Taking the existing interferometric HI image from the HALOGAS project of WSRT as reference, we are able to identify and characterize a significant excess of large-scale, low-density, and diffuse HI in the group. This diffuse HI extends for more than 120 kpc across, and accounts for more than one fourth of the total HI detected by FAST in and around the galaxy NGC 4631. In the region of the tidal tails, the diffuse HI has a typical column density above $10^{19.5}$ cm$^{-2}$, and is highly turbulent with a velocity dispersion around 50 km s$^{-1}$. It increases in column density with the dense HI, and tends to be associated with the kinematically ``hotter'' part of the dense HI. Through simple modeling, we find that the majority of the diffuse HI in the tail region is likely to induce cooling out of the hot IGM instead of evaporating or being radiatively ionized. Given these relations of gas in different phases, the diffuse HI may represent a condensing phase of the IGM. Active tidal interactions on-going and in the past may have produced the wide-spreading HI distribution, and triggered the gas accretion to NGC 4631 through the phase of the diffuse HI.

Using VSNET, VSOLJ, ASAS-SN and ATLAS observations, I found that the Z Cam star PY Per spent a long, faint low state reaching 19.1 mag at least between 2022 June and November. No dwarf nova outburst was recorded during this interval. TESS data during this low state showed two maxima in one orbital cycle and can be interpreted as an ellipsoidal modulation arising from the secondary. These observations suggest that the mass-transfer almost stopped during this low state and strengthen the identification of PY Per as a VY Scl star. PY Per had shown an unusual outburst resembling an SU UMa-type superoutburst less than half a year before (Kato 2022, arXiv:2204.12056) and these phenomena may have been physically related.

Spectral variability offers a new technique to identify small scale structures from scintillation, as well as determining the absorption mechanism for peaked-spectrum (PS) radio sources. In this paper, we present very long baseline interferometry (VLBI) imaging using the Long Baseline Array (LBA) of two PS sources, MRC0225-065 and PMNJ0322-4820, identified as spectrally variable from observations with the Murchison Widefield Array (MWA). We compare expected milliarcsecond structures based on the detected spectral variability with direct LBA imaging. We find MRC0225-065 is resolved into three components, a bright core and two fainter lobes, roughly 430pc projected separation. A comprehensive analysis of the magnetic field, host galaxy properties, and spectral analysis implies that MRC0225-065 is a young radio source with recent jet activity over the last 10^2-10^3years. We find PMNJ0322-4820 is unresolved on milliarcsecond scales. We conclude PMNJ0322-4820 is a blazar with flaring activity detected in 2014 with the MWA. We use spectral variability to predict morphology and find these predictions consistent with the structures revealed by our LBA images.

We report the multi-wavelength study for a high-synchrotron-peaked BL Lac 1ES 1218+304 using near-simultaneous data obtained during the period from January 1, 2018, to May 31, 2021 (MJD 58119-59365) from various instruments including Fermi-LAT, Swift-XRT, AstroSat, and optical from Swift-UVOT $\&$ TUBITAK observatory in Turkey. The source was reported to be flaring in TeV $\gamma$-ray during 2019 but no significant variation in Fermi-LAT is observed. A minute scale variability is seen in SXT light curve suggesting a compact emission region for their variability. However, Hour's scale variability is observed in the $\gamma$-ray light curve. A "softer-when-brighter" trend is observed in $\gamma$-ray and an opposite trend is seen in X-ray suggesting both emissions are produced via two different processes as expected from an HBL source. We have chosen the two epochs in January 2019 to study and compare their physical parameters. A joint fit of SXT and LAXPC provides a great constraint on the synchrotron peak roughly estimated to be $\sim$2.68$\times$10$^{17}$ Hz. A clear shift in the synchrotron peak is observed from 10$^{17-18}$ to 10$^{20}$ Hz revealing its extreme nature or behaving like an EHBL-type source. The optical observation provides color-index variation as "blue-when-brighter". The broadband SED is fitted with a single-zone SSC model and their parameters are discussed in the context of a TeV blazar and possible mechanism behind the broadband emission.

We present the Deep Synoptic Array (DSA-110) discovery and interferometric localization of the so far non-repeating FRB 20220319D. The FRB originates in a young, rapidly star-forming barred spiral galaxy, IRAS 02044$+$7048, at just 50 Mpc. Although the NE2001 and YMW16 models for the Galactic interstellar-medium (ISM) contribution to the DM of FRB 20220319D exceed its total observed DM, we show that uncertainties in these models accommodate an extragalactic origin for the burst. We derive a conservative upper limit on the DM contributed by the circumgalactic medium (CGM) of the Milky Way: the limit is either 28.7 pc cm$^{-3}$ and 47.3 pc cm$^{-3}$, depending on which of two pulsars nearby on the sky to FRB 20220319D is used to estimate the ISM DM. These limits both imply that the total Galactic CGM mass is $<10^{11}M_{\odot}$, and that the baryonic mass of the Milky Way is $\lesssim60\%$ of the cosmological average given the total halo mass. More stringent albeit less conservative constraints are possible when the DMs of pulsars in the distant globular cluster M53 are additionally considered. Although our constraints are sensitive to possible anisotropy in the CGM and to the assumed form of the radial-density profile, they are not subject to uncertainties in the chemical and thermal properties of the CGM. Our results strongly support scenarios commonly predicted by galaxy-formation simulations wherein feedback processes expel baryonic matter from the halos of galaxies like the Milky Way.

Brown dwarfs display Jupiter-like auroral phenomena such as magnetospheric H$\alpha$ emission and coherent radio emission. Coherent radio emission is a probe of magnetospheric acceleration mechanisms and provides a direct measurement of the magnetic field strength at the emitter's location, both of which are difficult to access by other means. Observations of the coldest brown dwarfs (spectral types T and Y) are particularly interesting as their magnetospheric phenomena may be very similar to those in gas-giant exoplanets. Here we present 144 MHz radio and infrared adaptive optics observations of the brown dwarf WISEP J101905.63+652954.2 made using the LOFAR and Keck telescopes respectively. The radio data shows pulsed highly circularly polarised emission which yields a rotation rate of $0.32\pm0.03$ hr$^{-1}$. The infrared imaging reveals the source to be a binary with a projected separation of $423.0\pm1.6$ mas between components of spectral type T5.$5\pm0.5$ and T7.$0\pm0.5$. With a simple "toy model" we show that the radio emission can in principle be powered by the interaction between the two dwarfs with a mass-loss rates of at least $25$ times the Jovian value. WISEP J101905.63+652954.2 is interesting because it is the first pulsed methane dwarf detected in a low radio-frequency search. Unlike previous gigahertz-frequency searches that were only sensitive to objects with kiloGauss fields, our low-frequency search is sensitive to surface magnetic fields of $\approx 50$ Gauss and above which might reveal the coldest radio-loud objects down to planetary mass-scales.

We test the homogeneity of the Pantheon+ sample with respect to the intrinsic absolute luminosity $M=m_{Bi}-\mu_i$ of the type Ia supernovae (SnIa) in Cepheid hosts and in the Hubble flow. Here, $m_{Bi}$ is the corrected/standardized SnIa apparent magnitude and $\mu_i$ is the $i^{th}$ SnIa distance modulus obtained either from Cepheids (for SnIa in Cepheid hosts) or from the parametrized Hubble expansion rate $H(z)$ (for the rest of the SnIa). When $M$ is allowed to take a single value in the context of flat \lcdm cosmological background $H(z)$, we find the expected best fit values $M=-19.25\pm 0.03$, $\Omega_{0m}=0.33\pm 0.02$, $H_0=(73.4 \pm 1)$~km~s$^{-1}$~Mpc$^{-1}$ consistent with the original analysis of Brout et. al. When we introduce a new degree of freedom allowing $M$ to take two values, one ($M_<$) for nearby SnIa (distance $d_i<d_{crit}$, $\mu_i<5\;log_{10}(d_{crit}/Mpc)+25$) and one ($M_>$) for more distant SnIa, we find a $2-3\sigma$ tension between the two best fit values of $M_>=-19.215\pm 0.03$ and $M_<=-19.362\pm 0.05$ for $d_{crit}\simeq 20Mpc$. However, in contrast to the pure SH0ES data, this degree of freedom does not affect significantly the best fit values for the cosmological parameters $H_0$ and $\Omega_{0m}$ obtained from Pantheon+, for any value of $d_{crit}$, due to the dominant effects of the covariance matrix. When $M$ is allowed to take distinct values $M_i$ for each SnIa in Cepheid hosts we find using a KS test, that the $M_i$ of nearby SnIa ($d_i<20Mpc$) have less than 2.5\% probability to have been drawn from the same probability distribution as the $M_i$ of more distant SnIa ($d>20Mpc$). These results constitute hints of inhomogeneities in the Pantheon+ sample which could be due to large statistical fluctuations, unaccounted systematic effects or new physics.

Blazar jet structure can be indirectly resolved by analyzing the multiwavelength variability. In this work, we analyze the long-term variability of blazars in radio, optical and X-ray energies with the Gaussian process (GP) method. The multiwavelength variability can be successfully characterized by the damped-random walk (DRW) model. The nonthermal optical characteristic timescales of 38 blazars are statistically consistent with the $\gamma$-ray characteristic timescales of 22 blazars. For three individuals (3C 273, PKS 1510-089, and BL Lac), the nonthermal optical, X-ray, and $\gamma$-ray characteristic timescales are also consistent within the measured 95$\%$ errors, but the radio timescale of 3C 273 is too large to be constrained by the decade-long light curve. The synchrotron and inverse-Compton emissions have the same power spectral density, suggesting that the long-term jet variability is irrelevant to the emission mechanism. In the plot of the rest-frame timescale versus black hole mass, the optical-$\gamma$-ray timescales of the jet variability occupy almost the same space with the timescales of accretion disk emission from normal quasars, which may imply that the long-term variabilities of the jet and accretion disk are driven by the same physical process. It is suggested that the nonthermal optical-X-ray and $\gamma$-ray emissions are produced in the same region, while the radio core which can be resolved by very-long-baseline interferometry locates at a far more distant region from the black hole. Our study suggests a new methodology for comparing thermal and nonthermal emissions, which is achieved by using the standard GP method.

Context. The lack of sub-Jovian planets on orbits of $P_{\rm orb} < 3$ days is a puzzling aspect of galaxy formation with regard to the distribution of exoplanets whose origins are currently unresolved. Aims. The possible explanations behind the formation of the sub-Jovian or Neptunian desert include several scenarios that can lead to different shapes for the boundary, predicting various dependencies between the position of the boundary and the stellar parameters. Methods. We explored the exoplanet distribution in various 2D and 3D projections, revealing the stellar-dependent substructures in the $P_{\rm orb}-M_{P}$ and the $P_{\rm orb}-R_{P}$ parameter plane. Results. We demonstrate that the upper boundary includes a range of planets, namely, inflated hot Jupiters and normal hot Jupiters, in the two parameter planes, respectively. We confirm the dependence of the boundary on several stellar parameters and, based on a fuzzy clustering analysis, we provide quantitative formulae for the dependencies in groups of smaller and larger planets. The overall period-radius distribution shows chemical substructures as well, with the boundary being dependent on volatiles and alpha-elements, alongside marginal (to none) dependence found for refractory elements. Conclusions. These findings confirm multiple plausible causes for the formation of the desert, particularly preferring those scenarios related to the irradiation-driven loss of the atmospheres of moderately massive planets as the predominant process in shaping planetary distributions.

We present an update on the variable star survey performed on the TESS 30 min Full Frame Image (FFI) data reported by our first two papers in this series. This update includes a contamination analysis in order to identify false positives and analysis of the TESS 10 min FFI data collected during Years 3 and 4 of the mission. We clarify the variability status of 2 995 targets identifying 1 403 variable stars. In addition, we spectroscopically classify 24 pre-filtered targets sampled with the 10 min FFI data and discover 11 new sdB pulsators. Future follow-up space- and/or ground-based data of variables reported here, to identify the nature of their variability and reveal spectroscopic parameters of the stars, would complement this work.

Photochemical hazes are suspected to obscure molecular features, such as water, from detection in the transmission spectra of exoplanets with atmospheric temperatures < 800 K. The opacities of laboratory produced organic compounds (tholins) from Khare et al. (1984) have become a standard for modeling haze in exoplanet atmospheres. However, these tholins were grown in an oxygen-free, Titan-like environment that is very different from typical assumptions for exoplanets, where C/O~0.5. This work presents the 0.13-10 micron complex refractive indices derived from laboratory transmission measurements of tholins grown in environments with different oxygen abundances. With the increasing uptake of oxygen, absorption increases across the entire wavelength range, and a scattering feature around 6 micron shifts towards shorter wavelengths and becomes more peaked around 5.8 micron, due to a C=O stretch resonance. Using GJ 1214b as a test-case, we examine the transmission spectra of a sub-Neptune planet with C/O ratios of solar, 1, and 1000 to evaluate the effective differences between our opacities and those of Khare. For an atmosphere with solar hydrogen and helium abundances, we find a difference of 200-1500 ppm, but for high-metallicity (Z=1000) environments, the difference may only be 20 ppm. The 1-2 micron transmission data for GJ 1214b rule out the Titan-like haze model, and are more consistent with C/O=1 and C/O=solar haze models. This work demonstrates that using haze opacities that are more consistent with underlying assumptions about bulk atmospheric composition are important for building self-consistent models that appropriately constrain the atmospheric C/O ratio, even when molecular features are obscured.

We present a simulation probing the formation of water in the remnant of low-mass Population III supernovae in a cosmological minihalo, and provide a tentative lower mass limit on host minihaloes that can recollapse on a short enough timescale and efficiently mix metals at high densities. We start from cosmological initial conditions and end the simulation when the central density undergoes catastrophic recollapse, whereby the water abundance is reported. During the Population III stars lifetime, the minihalo (M$ = 5 \times 10^5$ M$_{\odot}$) becomes blown out, and consequently the faint supernova explosion (E$_{\mathrm{SN}} = 5\times 10^{50}$ ergs) is completely unconfined to the virial radius of the minihalo. At the end of the simulation there is no significant water formation anywhere throughout the remnant, and the central recollapsing region is inefficient at incorporating the first metals into itself, remaining at low metallicity. The majority of metals are ejected from the core via bipolar outflow into the void and reach a peak metallicity of $\mathrm{Z} \sim 10^{-6}\ \mathrm{Z}_{\odot}$ at very low densities. The mass of the minihalo is low enough such that the recollapse timescale is unreasonable for this configuration to be the primary avenue of water formation in the early universe. We also provide a comparison with a regular CCSN (E$_{\mathrm{SN}} = 10^{51}$ ergs) and find the same effect, but amplified. As such, we can suggest that the minimum minihalo mass required for a confined explosion, and therefore the possibility of water formation is at least $10^{6}$ M$_{\odot}$ and the chemo-thermal evolution of a supernova remnant is more sensitive to the mass of the host minihalo than the mass of the Population III star residing within it.

Herbig Ae/Be stars are young contracting stars on the radiative track in the HR diagram on their way to the main sequence. These stars provide a valuable link between high and low mass stars. Here we review the progress that has been made in our understanding of these fascinating objects and their disks since the last major review on this topic published in 1998. We begin with a general overview of these stars and their properties. We then discuss the accretion of circumstellar material onto these stars. Next we discuss the dust and gas properties of the circumstellar disk before exploring the evidence for planet formation in these disks. We conclude with a brief discussion of future prospects for deepening our understanding of these sources and propose a new working definition of Herbig Ae/Be stars.

Misalignments between a forming star's rotation axis and its outer disk axis, although not predicted by standard theories of stellar formation, have been observed in several classical T Tauri stars (cTTs). The low-mass cTTs DK Tau is suspected of being among them. It is also an excellent subject to investigate the interaction between stellar magnetic fields and material accreting from the circumstellar disk, as it presents clear signatures of accretion. The goal of this paper is to study DK Tau's average line-of-sight magnetic field (Blos) in both photospheric absorption lines and emission lines linked to accretion, using spectropolarimetric observations, as well as to examine inconsistencies regarding its rotation axis. We used data collected with the ESPaDOnS and NARVAL spectropolarimeters, probing two distinct epochs (2010 and 2012). We first determined the stellar parameters, such as effective temperature and v sin i. Next, we removed the effect of veiling from the spectra, then obtained least-squares deconvolution profiles of the absorption lines, before determining the Blos. We also investigated emission lines, the 587.6 nm HeI line and the CaII infrared triplet, as tracers of the magnetic fields present in the accretion shocks. We find that DK Tau experiences accretion onto a magnetic pole at an angle of about 30 degrees from the pole of its rotation axis, with a positive field at the base of the accretion funnels. In 2010 we find a magnetic field of up to 1.77kG, and in 2012 up to 1.99kG. Additionally, using our derived values of period, v sin i and stellar radius, we find a value of 58 degrees (+18)(-11) for the inclination of the stellar rotation axis, which is significantly different from the outer disk axis inclination of 21 degrees given in the literature. We find that DK Tau's outer disk axis is likely misaligned compared to its rotation axis by 37 degrees.

Stellar winds of cool and pulsating asymptotic giant branch (AGB) stars enrich the interstellar medium with large amounts of processed elements and various types of dust. We present a first study on the influence of gas-to-dust drift on ab initio simulations of stellar winds of M-type stars driven by radiation pressure on forsterite particles. Our study is based on our radiation hydrodynamic model code T-800 that includes frequency-dependent radiative transfer, dust extinction based on Mie scattering, grain growth and ablation, gas-to-dust drift using one mean grain size, a piston that simulates stellar pulsations, and an accurate high spatial resolution numerical scheme. To enable this study, we calculated new gas opacities based on the \textsc{exomol} database, and we extended the model code to handle the formation of minerals that may form in M-type stars. We discern effects of drift by comparing drift models to our new and extant non-drift models. Compared to our recent results of C-rich stellar winds, our two new drift models based on an oxygen-rich chemistry show drift velocities that are higher by about a factor ten, that is 310-360 $\text{km}\,\text{s}^{-1}$. Our new drift model mass-loss rates are 8-20 times lower than our own non-drift models, but compared to extant models that use the same stellar parameters, our mass-loss rates are 10-420 times lower. Meanwhile, a comparison of other properties such as the expansion velocity and grain size show similar values. Our results show that the inclusion of gas-to-drift is of fundamental importance in stellar wind models driven by transparent grains such as forsterite. Assuming that the drift velocity is insignificant, properties such as the mass-loss rate may be off from more realistic values by a factor one hundred and more.

Supernova remnants (SNRs), the products of stellar explosions, are powerful astrophysical laboratories, which allow us to study the physics of collisionless shocks, thanks to their bright electromagnetic emission. Blast wave shocks generated by supernovae (SNe) provide us with an observational window to study extreme conditions, characterized by high Mach (and Alfvenic Mach) numbers, together with powerful nonthermal processes. In collisionless shocks, temperature equilibration between different species may not be reached at the shock front. In this framework, different particle species might be heated at different temperatures (depending on their mass) in the post-shock medium of SNRs. SNRs are also characterized by a broadband nonthermal emission stemming at the shock front as a result of nonthermal populations of leptons and hadrons. These particles, known as cosmic rays, are accelerated up to ultrarelativistic energies via diffusive shock acceleration. If SNRs lose a significant fraction of their ram energy to accelerate cosmic rays, the shock dynamics should be altered with respect to the adiabatic case. This shock modification should result in an increase of the total shock compression ratio with respect to the Rankine-Hugoniot value of 4. Here I show that the combination of X-ray high resolution spectroscopy (to measure ion temperatures) and moderate resolution spectroscopy (for a detailed diagnostic of the post-shock density) can be exploited to study both the heating mechanism and the particle acceleration in collisionless shocks. I report on new results in the temperatures measured for different ion species in the remnant of SN 1987A. I also discuss evidence of shock modification recently obtained in the remnant of SN 1006 a. D., where the shock compression ratio increases significantly as the angle between the shock velocity and the ambient magnetic field is reduced.

The Galactic Plane was searched for transient, monochromatic light at optical and near-IR wavelengths to detect pulses shorter than 1 sec. An objective-prism Schmidt telescope and CMOS camera were used to observe 973 square degrees along the Galactic Plane within a strip 2.1 deg wide. The non-detections of laser pulses from the Galactic Plane add to the non-detections from more than 5000 stars. The absence of extraterrestrial beacons reveals more of a SETI desert at optical and radio wavelengths.

Context. Thanks to more than 20 years of monitoring, the radial velocity (RV) method has detected long-period companions (P > 10yr) around several dozens of stars. Yet, the true nature of these companions remains unclear because of the uncertainty as to the inclination of the companion orbital plane. Aims. We wish to constrain the orbital inclination and the true mass of long-period single companions. Methods. We used a Markov Chain Monte Carlo (MCMC) fitting algorithm to combine RV measurements with absolute astrometry and, when available, relative astrometry data. Results. We have lifted the sin(i) indetermination for 7 seven long-period companions. We find true masses in the planetary mass range for the candidate planets detected in the following systems: Epsilon Indi A, HD 13931, HD 115954, and HD 222155. The mass of HD 219077 b is close to the deuterium-burning limit and its nature is uncertain because of the imprecise mass of the host star. Using additional RV measurements, we refine the orbital parameters of HIP 70849 b and find a mass in the planetary range. By combining RV data with absolute and relative astrometry, we significantly improve the characterization of HD 211847 B and properly determine its mass, which appears to be in the low-mass star range. This work illustrates how Gaia and Hipparcos allow for the orbital properties and masses of long-period RV companions to be further constrained.

Observations of protoplanetary disks around binary and triple star systems suggest that misalignments between the orbital plane of the stars and the disks are common. Motivated by recent observations of polar circumbinary disks, we explore the possibility for polar circumtriple disks and therefore polar circumtriple planets that could form in such a disk. With n-body simulations and analytic methods we find that the inclusion of the third star, and the associated apsidal precession, significantly reduces the radial range of polar orbits so that circumtriple polar disks and planets can only be found close to the stellar system. Outside of a critical radius, that is typically in the range of 3-10 times the outer binary separation depending upon the binary parameters, the orbits behave the same as they do around a circular orbit binary. For some observed systems that have shorter period inner binaries, the critical radius is considerably larger. If polar circumtriple planets can form, we suggest that it is likely that they form in a disk that was subject to breaking.

Cold cores are an early step of star formation, characterized by densities > 10$^4$ cm$^{-3}$, low temperatures (< 15 K), and very low external UV radiation. We investigate the physico-chemical processes at play to tracing the origin of molecules that are predominantly formed via reactions on dust grain surfaces. We observed the cold core LDN 429-C with the NOEMA interferometer and the IRAM 30m single dish telescope in order to obtain the gas-phase abundances of key species, including CO and CH$_3$OH. Comparing the observed gas phase of methanol to its solid phase previously observed with Spitzer allows us to put quantitative constraints on the efficiency of the non-thermal desorption of this species. With physical parameters determined from available Herschel data, we computed abundance maps of 11 detected molecules with a non-local thermal equilibrium radiative transfer model. These observations allowed us to probe the molecular abundances as a function of density and visual extinction, with the variation in temperature being restrained between 12 and 18 K. We then compared the observed abundances to the predictions of the Nautilus astrochemical model. We find that all molecules have lower abundances at high densities and visual extinctions with respect to lower density regions, except for methanol. Comparing these observations with a grid of chemical models based on the local physical conditions, we were able to reproduce these observations, allowing only the parameter time to vary. Comparing the observed gas-phase abundance of methanol with previous measurements of the methanol ice, we estimate a non-thermal desorption efficiency between 0.002% and 0.09%, increasing with density. The apparent increase in the desorption efficiency cannot be reproduced by our model unless the yield of cosmic-ray sputtering is altered due to the ice composition varying as a function of density.

We introduce a new framework for point-spread function (PSF) subtraction based on the spatio-temporal variation of speckle noise in high-contrast imaging data where the sampling timescale is faster than the speckle evolution timescale. One way that space-time covariance arises in the pupil is as atmospheric layers translate across the telescope aperture and create small, time-varying perturbations in the phase of the incoming wavefront. The propagation of this field to the focal plane preserves some of that space-time covariance. To utilize this covariance, our new approach uses a Karhunen-Lo\'eve transform on an image sequence, as opposed to a set of single reference images as in previous applications of Karhunen-Lo\'eve Image Processing (KLIP) for high-contrast imaging. With the recent development of photon-counting detectors, such as microwave kinetic inductance detectors (MKIDs), this technique now has the potential to improve contrast when used as a post-processing step. Preliminary testing on simulated data shows this technique can improve contrast by at least 10-20% from the original image, with significant potential for further improvement. For certain choices of parameters, this algorithm may provide larger contrast gains than spatial-only KLIP.

In some scenarios, the dark matter particle predominantly scatters inelastically with the target, producing a heavier neutral particle in the final state. In this class of scenarios, the reach in parameter space of direct detection experiments is limited by the velocity of the dark matter particle, usually taken as the escape velocity from the Milky Way. On the other hand, it has been argued that a fraction of the dark matter particles in the Solar System could be bound to the envelope of the Local Group or to the Virgo Supercluster, and not to our Galaxy, and therefore could carry velocities larger than the escape velocity from the Milky Way. In this paper we estimate the enhancement in sensitivity of current direct detection experiments to inelastic dark matter scatterings with nucleons or electrons due to the non-galactic diffuse components, and we discuss the implications for some well motivated models.

Thermal electrons have gyroradii many orders of magnitude smaller than the finite width of a shock, thus need to be pre-accelerated before they can cross it and be accelerated by diffusive shock acceleration. One region where pre-acceleration may occur is the inner foreshock, which upstream electrons must pass through before any potential downstream crossing. In this paper, we perform a large scale particle-in-cell simulation that generates a single shock with parameters motivated from supernova remnants. Within the foreshock, reflected electrons excite the oblique whistler instability and produce electromagnetic whistler waves, which co-move with the upstream flow and as non-linear structures eventually reach radii of up to 5 ion-gyroradii. We show that the inner electromagnetic configuration of the whistlers evolves into complex non-linear structures bound by a strong magnetic field around 4 times the upstream value. Although these non-linear structures do not in general interact with co-spatial upstream electrons, they resonate with electrons that have been reflected at the shock. We show that they can scatter, or even trap, reflected electrons, confining around $0.8\%$ of the total upstream electron population to the region close to the shock where they can undergo substantial pre-acceleration. This acceleration process is similar to, yet approximately 3 times more efficient than, stochastic shock drift acceleration.

The images of supermassive black holes in M87 and our galaxy taken by Event Horizon Telescope might open up a new window for studying black hole physics at horizon scale. It is well-motivated to extract physical information about emission models and black hole geometries with the images. This paper investigates the two-point correlations of intensity fluctuation on the photon ring, as a result of existence of shock waves in Schwarzschild background. Following the approaches used in field of gravitational wave detectors, we introduce response functions of EHT for detecting the shock waves, and study shape of the overlap reduction functions. It is found that the shape of the correlations we obtained is different from that attributed to stochastic emission sources. It suggests that the intensity correlations can be used to distinguish the emission models and black hole geometries in the stochastic regime.

The rotating black holes in the quintessential dark energy correspond to three horizons: inner, outer, and quintessential horizon. The domain of outer communication is the region between outer and quintessential horizon. Here, in this work we study the photon region and shadows of the quintessential dark energy black holes when the observer stays statically in the domain of outer communication. The quintessential dark energy black holes shadow characterizes by its mass $(M)$, spin parameter $(a)$, quintessential dark energy parameter $(\omega_q)$, and normalization factor $(\gamma)$. The dark energy parameter $\omega_q$ can take values in between $-1.1<\omega_q<-1/3$ and follows the equation of state $\omega_q$=pressure$(p)$/energy density($\rho_q)$. This state parameter significantly affects the shape and size of the black hole shadow. We generalize all the geodesic equations of motion for $\omega_q$ and obtain relation to visualize the black hole shadow by a static observer at any arbitrary distance in the domain of outer communication. We analytically estimate the black hole shadow observables: radius $R_s$, distortion parameter $\delta_s$ and the shadow area $A$. Using the numerical values of shadow radius $R_s$ and area $A$, we obtain the angular diameter of the black hole shadow. The angular size of the M87 and Sgr A$^*$ black holes are $\ 42 \pm 3 \mu a s$ and $48.7 \pm 7 \mu a s $ respectively as observe by Event Horizon Telescope (EHT). In this case, the angular diameter of the black hole shadow increases with the quintessence parameter $\omega_q$ and takes values $\theta_d \approx 20 \pm 3{^o}$ with the parameter $-0.66 \leq \omega_q \leq -0.62$ for the static observer at $r_o=5M$ in the domain of outer communication.

It has recently been shown that the dynamics of perturbed non-rotating black holes (BHs) admits an infinite number of symmetries that are generated by the flow of the Korteweg-de Vries (KdV) equation. These symmetries lead to an infinite number of conserved quantities that can be obtained as integrals of differential polynomials in the potential appearing in the gauge-invariant master equations describing the BH perturbations, the KdV integrals. These conserved quantities are the same for all the possible potentials, which means that they are invariant under Darboux transformations, and they fully determine the BHs transmission amplitudes, or greybody factors, via a moment problem. In this paper we introduce a new semi-analytical method to obtain the greybody factors associated with BH scattering processes by solving the moment problem using only the KdV integrals. The method is based on the use of Pad\'e approximants and we check it first by comparing with results from the case of a P\"oschl-Teller potential, for which we have analytical expressions for the greybody factors. Then, we apply it to the case of a Schwarzschild BH and compare with results from computations based on the Wentzel-Kramers-Brillouin (WKB) approximation. It turns out that the new method provides accurate results for the BH greybody factors for all frequencies. The method is also computationally very efficient.

We expose the phenomenology of the massless dilaton theory in the Solar system for a non universal quadratic coupling between the scalar field which represents the dilaton, and the matter. Modified post-Newtonian equations of motion of an $N$-body system and the light time travel are derived from the action of the theory. We use the physical properties of the main planets of the Solar system to reduce the number of parameters to be tested to 3 in the linear coupling case. In the linear case, we have an universal coupling constant $\alpha_0$ and two coupling constants $\alpha_T$ and $\alpha_G$ related respectively to the telluric bodies and to the gaseous bodies. We then use the planetary ephemeris, INPOP19a, in order to constrain these constants. We succeeded to constrain the linear coupling scenario and the constraints read $\alpha_0=(1.01\pm23.7)\times 10^{-5}$, $\alpha_T=(0.00\pm24.5)\times 10^{-6}$, $\alpha_G=(-1.46\pm12.0)\times 10^{-5}$, at the 99.5 \% C.L.

In this review, we describe turbulent drag reduction in a variety of flows using a universal framework of energy flux. In a turbulent flow with dilute polymers and magnetic field, the kinetic energy injected at large scales cascades to the velocity field at intermediate scales, as well as to the polymers and magnetic field at all scales. Consequently, the kinetic energy flux, $ \Pi_u(k) $, is suppressed in comparison to the pure hydrodynamic turbulence. We argue that the suppression of $\Pi_u(k)$ is an important factor in the reduction of the inertial force $\langle {\bf u \cdot \nabla u} \rangle$ and \textit{turbulent drag}. This feature of turbulent drag reduction is observed in polymeric, magnetohydrodynamic, quasi-static magnetohydrodynamic, and stably-stratified turbulence, and in dynamos. In addition, it is shown that turbulent drag reduction in thermal convection is due to the smooth thermal plates, similar to the turbulent drag reduction over bluff bodies. In all these flows, turbulent drag reduction often leads to a strong large-scale velocity in the flow.