adsabs/SciX_UAT_keywords huggingface dataset:
Years-delayed X-Ray Afterglows of TDEs Originated from Wind-Torus Interactions

Tidal disruption events (TDEs) occurring in active galactic nuclei (AGNs) are a special class of sources with outstanding scientific significance. TDEs can generate ultrafast winds, which should almost inevitably collide with the preexisting AGN dusty tori. We perform analytical calculations and simulations on the wind-torus interactions and find such a process can generate considerable X-ray afterglow radiation several years or decades later after the TDE outburst. This provides a new origin for the years delayed X-rays in TDEs. The X-ray luminosity can reach 1041-42 erg s-1, and the light curve characteristics depend on the parameters of winds and tori. We apply the model to two TDE candidates, and provide lower limits on the masses of the disrupted stars, as well as rigorous constraints on the gas densities of tori. Our results suggest that the observations of the time delay, spectral shape, luminosity, and the light curve of the X-ray afterglow can be used to constrain the physical parameters of both TDE winds and tori, including the wind velocity, wind density, cloud density, and cloud size.

Keywords: active galaxies; supermassive black holes; hydrodynamical simulations; x-ray transient sources; shocks
Probing Protoplanetary Disk Winds with C II Absorption

We present an analysis of wind absorption in the C II λ1335 doublet toward 40 classical T Tauri stars with archival far-ultraviolet (FUV) spectra obtained by the Hubble Space Telescope. Absorption features produced by fast or slow winds are commonly detected (36 out of 40 targets) in our sample. The wind velocity of the fast wind decreases with disk inclination, which is consistent with expectations for a collimated jet. Slow wind absorption is mostly detected in disks with intermediate or high inclination, without a significant dependence of wind velocity on disk inclination. Both the fast and slow wind absorption are preferentially detected in FUV lines of neutral or singly ionized atoms. The Mg II λλ2796, 2804 lines show wind absorption consistent with the absorption in the C II lines. We develop simplified semi-analytical disk/wind models to interpret the observational disk wind absorption. Both fast and slow winds are consistent with expectations from a thermal-magnetized disk wind model and are generally inconsistent with a purely thermal wind. Both the models and the observational analysis indicate that wind absorption occurs preferentially from the inner disk, which offers a wind diagnostic in complement to optical forbidden line emission that traces the wind in larger volumes.

Keywords: protoplanetary disks; stellar winds; classical t tauri stars; stellar accretion; ultraviolet astronomy
How Much Do Underestimated Field Strengths from Zeeman-Doppler Imaging Affect Spin-down Torque Estimates?

Numerous attempts to estimate the rate at which low-mass stars lose angular momentum over their lifetimes fill the literature. One approach is to use magnetic maps derived from Zeeman-Doppler imaging (ZDI) in conjunction with so-called "braking laws." The use of ZDI maps has advantages over other methods because it allows information about the magnetic field geometry to be incorporated into the estimate. However, ZDI is known to underestimate photospheric field strengths due to flux cancellation effects. Recently, Lehmann et al. conducted synthetic ZDI reconstructions on a set of flux transport simulations to help quantify the amount by which ZDI underestimates the field strengths of relatively slowly rotating and weak activity solar-like stars. In this paper, we evaluate how underestimated angular momentum loss rate estimates based on ZDI maps may be. We find that they are relatively accurate for stars with strong magnetic fields but may be underestimated by a factor of up to ∼10 for stars with weak magnetic fields. Additionally, we re-evaluate our previous work that used ZDI maps to study the relative contributions of different magnetic field modes to angular momentum loss. We previously found that the dipole component dominates spin-down for most low-mass stars. This conclusion still holds true even in light of the work of Lehmann et al.

Keywords: low mass stars; stellar rotation; stellar winds; stellar magnetic fields
TESS Observations of the Pleiades Cluster: A Nursery for δ Scuti Stars

We studied 89 A- and F-type members of the Pleiades open cluster, including five escaped members. We measured projected rotational velocities ( $v\sin i$ ) for 49 stars and confirmed that stellar rotation causes a broadening of the main sequence in the color-magnitude diagram. Using time-series photometry from NASA's TESS Mission (plus one star observed by Kepler/K2), we detected δ Scuti pulsations in 36 stars. The fraction of Pleiades stars in the middle of the instability strip that pulsate is unusually high (over 80%), and their range of effective temperatures agrees well with theoretical models. On the other hand, the characteristics of the pulsation spectra are varied and do not correlate with stellar temperature, calling into question the existence of a useful ${\nu }_{\max }$ relation for δ Scutis, at least for young main-sequence stars. By including δ Scuti stars observed in the Kepler field, we show that the instability strip is shifted to the red with increasing distance by interstellar reddening. Overall, this work demonstrates the power of combining observations with Gaia and TESS for studying pulsating stars in open clusters.

Keywords: asteroseismology; open star clusters; delta scuti variable stars
On the Role of Alfvénic Fluctuations as Mediators of Coherence within Interplanetary Coronal Mass Ejections: Investigation of Multi-spacecraft Measurements at 1 au

Interplanetary coronal mass ejections (ICMEs) are defined as "coherent" if they are capable of responding to external perturbations in a collective manner. This implies that information must be able to propagate across ICME structures, and if this is not the case, single-point in situ measurements cannot be considered as indicative of global ICME properties. Here, we investigate the role of Alfvénic fluctuations (AFs) as mediators of ICME coherence. We consider multipoint magnetic field and plasma measurements of 10 ICMEs observed by the ACE and Wind spacecraft at 1 au at longitudinal separations of 0.5°-0.7°. For each event, we analyze the Alfvénicity in terms of the residual energy and cross helicity of fluctuations, and the coherence in terms of the magnetic correlation between Wind and ACE. We find that ~65% and 90% of ICME sheaths and magnetic ejecta (MEs), respectively, present extended AFs covering at least 20% of the structure. Cross helicity suggests AFs of solar and interplanetary origin may coexist in the ICME population at 1 au. AFs are mainly concentrated downstream of shocks and in the back of MEs. The magnetic field is poorly correlated within sheaths, while the correlation decreases from the front to the back of the MEs for most magnetic field components. AFs are also associated with lower magnetic field correlations. This suggests either that ICME coherence is not mediated by Alfvén waves, implying that the coherence scale may be smaller than previously predicted, or that the magnetic field correlation is not a measure of coherence.

Keywords: solar coronal mass ejections; solar wind; interplanetary magnetic fields; alfven waves
CH3OH and Its Deuterated Species in the Disk/Envelope System of the Low-mass Protostellar Source B335

Deuterium fractionation in the closest vicinity of a protostar is important in understanding its potential heritage to a planetary system. Here, we have detected the spectral line emission of CH3OH and its three deuterated species, CH2DOH, CHD2OH, and CH3OD, toward the low-mass protostellar source B335 at a resolution of 0.″03 (5 au) with Atacama Large Millimeter/submillimeter Array. They have a ring distribution within the radius of 24 au with the intensity depression at the continuum peak. We derive the column densities and abundance ratios of the above species at six positions in the disk/envelope system as well as the continuum peak. The D/H ratio of CH3OH is ∼[0.03–0.13], which is derived by correcting the statistical weight of 3 for CH2DOH. The [CHD2OH]/[CH2DOH] ratio is derived to be higher ([0.14–0.29]). On the other hand, the [CH2DOH]/[CH3OD] ratio ([4.9–15]) is higher than the statistical ratio of 3 and is comparable to those reported for other low-mass sources. We study the physical structure on a few astronomical unit scales in B335 by analyzing the CH3OH (183,15 ‑ 182,16, A) and HCOOH (120,12 ‑ 110,11) line emission. Velocity structures of these lines are reasonably explained as the infalling-rotating motion. The protostellar mass and the upper limit to the centrifugal barrier are thus derived to be 0.03–0.07 M ⊙ and <7 au, respectively, showing that B335 harbors a young protostar with a tiny disk structure. Such youth of the protostar may be related to the relatively high [CH2DOH]/[CH3OH] ratio.

Keywords: young stellar objects; star formation; protostars; interstellar molecules; astrochemistry
The Second International Asteroid Warning Network Timing Campaign: 2005 LW3

The Earth close approach of near-Earth asteroid 2005 LW3 on 2022 November 23 represented a good opportunity for a second observing campaign to test the timing accuracy of astrometric observation. With 82 participating stations, the International Asteroid Warning Network collected 1046 observations of 2005 LW3 around the time of the close approach. Compared to the previous timing campaign targeting 2019 XS, some individual observers were able to significantly improve the accuracy of their reported observation times. In particular, U.S. surveys achieved good timing performance. However, no broad, systematic improvement was achieved compared to the previous campaign, with an overall negative bias persisting among the different observers. The calibration of observing times and the mitigation of timing errors should be important future considerations for observers and orbit computers, respectively.

Keywords: asteroids; near-earth objects; optical telescopes; astrometry
Resilience of Planetesimal Formation in Weakly Reinforced Pressure Bumps

The discovery that axisymmetric dust rings are ubiquitous in protoplanetary disks has provoked a flurry of research on the role of pressure bumps in planet formation. High-resolution simulations by our group have shown that even a modest bump can collect enough dust to trigger planetesimal formation by the streaming instability. In this work, we probe the limits of planetesimal formation when the external source of pressure bump reinforcement is extremely weak. We conduct simulations of radially elongated shearing boxes to capture the entire bump, which is generated and maintained over some timescale ${t}_{\mathrm{reinf}}$ by a Newtonian relaxation scheme. We find that planetesimal formation is extremely resilient for centimeter-sized grains. We reduced the strength of reinforcement by up to a factor of 100 and the location and initial masses of planetesimals were essentially unaffected. However, we do find that strong reinforcement causes much faster pebble drift compared to the standard pebble drift rates. The resulting larger pebble flux enhances the planetesimal growth rate by pebble accretion. We hypothesize that, to sustain the bump, our code has to extract angular momentum (the strength of this negative torque depends on ${t}_{\mathrm{reinf}}$ ), and some of this torque is transferred to the particles, causing them to drift faster for a stronger torque (i.e., smaller ${t}_{\mathrm{reinf}}$ ). Since any physical process that sustains a pressure bump must do so by torquing the gas, we conjecture that the effect on pebble drift is a real phenomenon, motivating further work with physically realistic sources to generate the bump.

Keywords: exoplanet formation; planet formation; planetesimals; protoplanetary disks; planetary system formation
The Zwicky Transient Facility Bright Transient Survey. II. A Public Statistical Sample for Exploring Supernova Demographics

We present a public catalog of transients from the Zwicky Transient Facility (ZTF) Bright Transient Survey, a magnitude-limited (m < 19 mag in either the g or r filter) survey for extragalactic transients in the ZTF public stream. We introduce cuts on survey coverage, sky visibility around peak light, and other properties unconnected to the nature of the transient, and show that the resulting statistical sample is spectroscopically 97% complete at <18 mag, 93% complete at <18.5 mag, and 75% complete at <19 mag. We summarize the fundamental properties of this population, identifying distinct duration-luminosity correlations in a variety of supernova (SN) classes and associating the majority of fast optical transients with well-established spectroscopic SN types (primarily SN Ibn and II/IIb). We measure the Type Ia SN and core-collapse (CC) SN rates and luminosity functions, which show good consistency with recent work. About 7% of CC SNe explode in very low-luminosity galaxies (Mi > -16 mag), 10% in red-sequence galaxies, and 1% in massive ellipticals. We find no significant difference in the luminosity or color distributions between the host galaxies of SNe Type II and SNe Type Ib/c, suggesting that line-driven wind stripping does not play a major role in the loss of the hydrogen envelope from their progenitors. Future large-scale classification efforts with ZTF and other wide-area surveys will provide high-quality measurements of the rates, properties, and environments of all known types of optical transients and limits on the existence of theoretically predicted but as yet unobserved explosions. * An interactive catalog with all data used in this paper is available at https://sites.astro.caltech.edu/ztf/bts and is updated in real time.

Keywords: supernovae; catalogs; surveys; transient sources; time domain astronomy
A Comparison of Particle-in-cell and Hybrid Simulations of the Heliospheric Termination Shock

We compare hybrid (kinetic proton, fluid electron) and particle-in-cell (kinetic proton, kinetic electron) simulations of the solar wind termination shock with parameters similar to those observed by Voyager 2 during its crossing. The steady-state results show excellent agreement between the downstream variations in the density, plasma velocity, and magnetic field. The quasi-perpendicular shock accelerates interstellar pickup ions to a maximum energy limited by the size of the computational domain, with somewhat higher fluxes and maximal energies observed in the particle-in-cell simulation, likely due to differences in the cross-shock electric field arising from electron kinetic-scale effects. The higher fluxes may help address recent discrepancies noted between observations and large-scale hybrid simulations.

Keywords: termination shock; heliosphere
Circumgalactic Mg II Emission from an Isotropic Starburst Galaxy Outflow Mapped by KCWI

We present spatially resolved spectroscopy from the Keck Cosmic Web Imager (KCWI) of a star-forming galaxy at z = 0.6942, which shows emission from the Mg II λλ2796, 2803 doublet in the circumgalactic medium (CGM) extending ∼37 kpc at 3σ significance in individual spaxels (1σ detection limit 4.8 × 10-19 erg s-1 cm-2 arcsec-2). The target galaxy, selected from a near-UV spectroscopic survey of Mg II line profiles at 0.3 < z < 1.4, has a stellar mass log (M*/M⊙) = 9.9, a star formation rate of 50 M⊙ yr-1, and a morphology indicative of a merger. After deconvolution with the seeing, we obtain 5σ detections of Mg II line emission extending for ∼31 kpc measured in 7-spaxel (1.1 arcsec2) apertures. Spaxels covering the galaxy stellar regions show clear P Cygni-like emission/absorption profiles, with the blueshifted absorption extending to relative velocities of v = -800 km s-1; however, the P Cygni profiles give way to pure emission at large radii from the central galaxy. We have performed 3D radiative transfer modeling to infer the geometry and velocity and density profiles of the outflowing gas. Our observations are most consistent with an isotropic outflow rather than biconical wind models with half-opening angles φ ≤ 80°. Furthermore, our modeling suggests that a wind velocity profile that decreases with radius is necessary to reproduce the velocity widths and strengths of Mg II line emission profiles at large circumgalactic radii. The extent of the Mg II emission we measure directly is further corroborated by our modeling, where we rule out outflow models with extent <30 kpc.

Keywords: galaxy winds; starburst galaxies; circumgalactic medium; galaxy evolution
Accretion History of AGNs. II. Constraints on AGN Spectral Parameters Using the Cosmic X-Ray Background

We constrain X-ray spectral shapes for the ensemble of active galactic nuclei (AGNs) based on the shape of the cosmic X-ray background (CXB). Specifically, we rule out regions of X-ray spectral parameter space that do not reproduce the CXB in the energy range 1-100 keV. The key X-ray spectral parameters are the photon index, Γ; the cutoff energy, Ecutoff; and the reflection scaling factor, R. Assuming each parameter follows a Gaussian distribution, we first explore the parameter space using a Bayesian approach and a fixed X-ray luminosity function (XLF). For σE = 36 keV and σR = 0.14, fixed at the observed values from the Swift-BAT 70-month sample, we allow $\langle R\rangle ,\langle {E}_{\mathrm{cutoff}}\rangle $ and $\langle {\rm{\Gamma }}\rangle $ to vary subject to reproducing the CXB. We report results for σΓ = 0.1-0.5. In an alternative approach, we define the parameter distributions, then forward model to fit the CXB by perturbing the XLF using a neural network. This approach allows us to rule out parameter combinations that cannot reproduce the CXB for any XLF. The marginalized conditional probabilities for the four free parameters are: $\langle R\rangle \,={0.99}_{-0.26}^{+0.11},\langle {E}_{\mathrm{cutoff}}\rangle ={118}_{-23}^{+24},{\sigma }_{{\rm{\Gamma }}}={0.101}_{-0.001}^{+0.097}$ and $\langle {\rm{\Gamma }}\rangle ={1.9}_{-0.09}^{+0.08}$ . We provide an interactive online tool for users to explore any combination of $\langle {E}_{\mathrm{cutoff}}\rangle $ , σE, $\langle {\rm{\Gamma }}\rangle $ , σΓ, $\langle R\rangle $ , and σR, including different distributions for each absorption bin, subject to the integral CXB constraint. The distributions observed in many AGN samples can be ruled out by our analysis, meaning these samples cannot be representative of the full AGN population. The few samples that fall within the acceptable parameter space are hard-X-ray-selected, commensurate with their having fewer selection biases.

Keywords: x-ray active galactic nuclei; active galactic nuclei; diffuse x-ray background; x-ray sources; x-ray surveys; supermassive black holes; quasars; astrophysical black holes
Cosmological Constraints from Galaxy Cluster Sparsity, Cluster Gas Mass Fraction, and Baryon Acoustic Oscillation Data

In recent years, the availability of large, complete cluster samples has enabled numerous cosmological parameter inference analyses using cluster number counts. These have provided constraints on the cosmic matter density Ωm and the amplitude of matter density fluctuations σ8 alternative to that obtained from other standard probes. However, systematics uncertainties, such as the mass calibration bias and selection effects, may still significantly affect these data analyses. Hence, it is timely to explore other proxies of galaxy cluster cosmology that can provide cosmological constraints complementary to those obtained from cluster number counts. Here we use measurements of the cluster sparsity from weak-lensing mass estimates of the LC2-single and HSC-XXL cluster catalogs to infer constraints on a flat ΛCDM model. The cluster sparsity has the advantage of being insensitive to selection and mass calibration bias. On the other hand, it primarily constrains a degenerate combination of Ωm and σ8 (along approximately constant curves of ${S}_{8}={\sigma }_{8}\sqrt{{{\rm{\Omega }}}_{m}/0.3}$ and, to a lesser extent, the reduced Hubble parameter h. Hence, in order to break the internal parameter degeneracies, we perform a combined likelihood analysis of the cluster sparsity estimates with cluster gas mass fraction measurements and BAO data. We find marginal constraints that are competitive with those from other standard cosmic probes: Ωm = 0.316 ± 0.013, σ8 = 0.757 ± 0.067 (corresponding to S8 = 0.776 ± 0.064), and h = 0.696 ± 0.017 at 1σ. Moreover, assuming a conservative Gaussian prior on the mass bias of gas mass fraction data, we find a lower limit on the gas depletion factor Yb,500c ≳ 0.89.

Keywords: cosmological parameters from large-scale structure; cosmology; galaxy clusters
A Constraint on Primordial B-modes from the First Flight of the SPIDER Balloon-borne Telescope

We present the first linear polarization measurements from the 2015 long-duration balloon flight of SPIDER, which is an experiment that is designed to map the polarization of the cosmic microwave background (CMB) on degree angular scales. The results from these measurements include maps and angular power spectra from observations of 4.8% of the sky at 95 and 150 GHz, along with the results of internal consistency tests on these data. While the polarized CMB anisotropy from primordial density perturbations is the dominant signal in this region of sky, Galactic dust emission is also detected with high significance. Galactic synchrotron emission is found to be negligible in the SPIDER bands. We employ two independent foreground-removal techniques to explore the sensitivity of the cosmological result to the assumptions made by each. The primary method uses a dust template derived from Planck data to subtract the Galactic dust signal. A second approach, which constitutes a joint analysis of SPIDER and Planck data in the harmonic domain, assumes a modified-blackbody model for the spectral energy distribution of the dust with no constraint on its spatial morphology. Using a likelihood that jointly samples the template amplitude and r parameter space, we derive 95% upper limits on the primordial tensor-to-scalar ratio from Feldman-Cousins and Bayesian constructions, finding r < 0.11 and r < 0.19, respectively. Roughly half the uncertainty in r derives from noise associated with the template subtraction. New data at 280 GHz from SPIDER's second flight will complement the Planck polarization maps, providing powerful measurements of the polarized Galactic dust emission.

Keywords: cosmic microwave background radiation; observational cosmology; cosmological parameters; interstellar emissions
Simulating Jellyfish Galaxies: A Case Study for a Gas-rich Dwarf Galaxy

We investigate the formation of jellyfish galaxies using radiation-hydrodynamic simulations of gas-rich dwarf galaxies with a multiphase interstellar medium (ISM). We find that the ram-pressure-stripped (RPS) ISM is the dominant source of molecular clumps in the near wake within 10 kpc from the galactic plane, while in situ formation is the major channel for dense gas in the distant tail of the gas-rich galaxy. Only 20% of the molecular clumps in the near wake originate from the intracluster medium (ICM); however, the fraction reaches 50% in the clumps located at 80 kpc from the galactic center since the cooling time of the RPS gas tends to be short owing to the ISM-ICM mixing (≲10 Myr). The tail region exhibits a star formation rate of 0.001-0.01 M ⊙ yr-1, and most of the tail stars are born in the stripped wake within 10 kpc from the galactic plane. These stars induce bright Hα blobs in the tail, while Hα tails fainter than 6 × 1038 erg s-1 kpc-2 are mostly formed via collisional radiation and heating due to mixing. We also find that the stripped tails have intermediate X-ray-to-Hα surface brightness ratios (1.5 ≲ F X/F Hα ≲ 20), compared to the ISM (≲1.5) or pure ICM (≫20). Our results suggest that jellyfish features emerge when the ISM from gas-rich galaxies is stripped by strong ram pressure, mixes with the ICM, and enhances the cooling in the tail.

Keywords: galaxy environments; ram pressure stripped tails; hydrodynamical simulations