adsabs/SciX_UAT_keywords huggingface dataset:
Limits on Simultaneous and Delayed Optical Emission from Well-localized Fast Radio Bursts

We present the largest compilation to date of optical observations during and following fast radio bursts (FRBs). The data set includes our dedicated simultaneous and follow-up observations, as well as serendipitous archival survey observations, for a sample of 15 well-localized FRBs: eight repeating and seven one-off sources. Our simultaneous (and nearly simultaneous with a 0.4 s delay) optical observations of 13 (1) bursts from the repeating FRB 20220912A provide the deepest such limits to date for any extragalactic FRB, reaching a luminosity limit of ν L ν ≲ 1042 erg s-1 (≲2 × 1041 erg s-1) with 15-400 s exposures; an optical-flux-to-radio-fluence ratio of f opt/F radio ≲ 10-7 ms-1 (≲10-8 ms-1); and a flux ratio of f opt/f radio ≲ 0.02-≲2 × 10-5 (≲10-6) on millisecond to second timescales. These simultaneous limits provide useful constraints in the context of FRB emission models, such as the pulsar magnetosphere and pulsar nebula models. Interpreting all available optical limits in the context of the synchrotron maser model, we find that they constrain the flare energies to ≲1043-1049 erg (depending on the distances of the various repeating FRBs, with ≲1039 erg for the Galactic SGR 1935+2154). These limits are generally at least an order of magnitude larger than those inferred from the FRBs themselves, although in the case of FRB 20220912A our simultaneous and rapid follow-up observations severely restrict the model parameter space. We conclude by exploring the potential of future simultaneous and rapid-response observations with large optical telescopes.

Keywords: radio transient sources; transient sources; magnetars; pulsars
Estimation of Key Sunquake Parameters through Hydrodynamic Modeling and Cross-correlation Analysis

Sunquakes are one of the more distinct secondary phenomena related to solar flares, where energy deposition in the lower layers of the Sun's atmosphere excites acoustic waves easily visible in photospheric dopplergrams. We explore two possible excitation mechanisms of sunquakes in the context of the electron beam hypothesis: an instantaneous transfer of momentum and a gradual applied force due to flare eruption. We model the sunquake excitation and compare with five observed sunquake events using a cross-correlation analysis. We find that at least half the events studied are consistent with the electron beam hypothesis and estimate the energy required to excite the sunquakes to be within the range determined by previous studies.

Keywords: helioseismology; solar flares; solar physics
Multiwavelength Follow-up of FRB180309

We report on the results of multiwavelength follow-up observations with Gemini, Very Large Array (VLA), and Australia Telescope Compact Array to search for a host galaxy and any persistent radio emission associated with FRB 180309. This FRB is among the most luminous FRB detections to date, with a luminosity of >8.7 × 1032 erg Hz-1 at the dispersion-based redshift upper limit of 0.32. We used the high-significance detection of FRB 180309 with the Parkes Telescope and a beam model of the Parkes Multibeam Receiver to improve the localization of the FRB to a region spanning approximately $\sim 2^{\prime} \times 2^{\prime} $ . We aimed to seek bright galaxies within this region to determine the strongest candidates as the originator of this highly luminous FRB. We identified optical sources within the localization region above our r-band magnitude limit of 24.27, 14 of which have photometric redshifts whose fitted mean is consistent with the redshift upper limit (z < 0.32) of our FRB. Two of these galaxies are coincident with marginally detected "persistent" radio sources of flux density 24.3 μJy beam-1 and 22.1 μJy beam-1, respectively. Our redshift-dependent limit on the luminosity of any associated persistent radio source is comparable to the luminosity limits for other localized FRBs. We analyze several properties of the candidate hosts we identified, including chance association probability, redshift, and presence of radio emission; however, it remains possible that any of these galaxies could be the host of this FRB. Follow-up spectroscopy on these objects to explore their Hα emission and ionization contents, as well as to obtain more precisely measured redshifts, may be able to isolate a single host for this luminous FRB.

Keywords: radio transient sources; radio continuum emission; radio interferometry; optical observation; optical identification; radio galaxies; extragalactic radio sources; radio bursts; very large array
The Behavior of HgMn Stars in the Far UV-Paper 11: HD 53929 and HD 172044

The analysis of low and high resolution spectra of the chemically peculiar stars HD 53929 and HD 172044 recorded by the SWP camera on board the International Ultraviolet Explorer reveals no variations of the far-ultraviolet fluxes of these stars. The far-ultraviolet Ga II and Ga III resonance lines are strong absorbers in the spectrum of HD 172044. The TESS lightcurve of HD 172044 suggests a period close to 4.347 ± 0.135 days which could be the rotational period. On SWP 34118 the resonance lines of Si II and Ga II are blueshifted compared to SWP 34110 probably reflecting the orbital motion of HD 172044.

Keywords: chemically peculiar stars; mercury-manganese stars
The Cluster-central Compact Steep-spectrum Radio Galaxy 1321+045

The radio galaxy 1321+045 is a rare example of a young, compact steep-spectrum source located in the center of a z = 0.263 galaxy cluster. Using a combination of Chandra, VLBA, VLA, MERLIN, and IRAM 30 m observations, we investigate the conditions that have triggered this outburst. We find that the previously identified 5 kpc scale radio lobes are probably no longer powered by the active galactic nucleus, which seems to have launched a new ∼20 pc jet on a different axis, likely within the last few hundred years. We estimate the enthalpy of the lobes to be ${8.48}_{-3.56}^{+6.04}\times {10}^{57}\,\mathrm{erg}$ , only sufficient to balance cooling in the surrounding 16 kpc for ∼9 Myr. The properties of the cluster's intracluster medium (ICM) are similar to those of rapidly cooling nearby clusters, with a low central entropy (8.6 ${}_{-1.4}^{+2.2}$ keV cm2 within 8 kpc), short central cooling time (390 ${}_{-150}^{+170}$ Myr), and tcool/tff and tcool/teddy ratios indicative of thermal instability out to ∼45 kpc. Despite previous detection of Hα emission from the brightest cluster galaxy, our IRAM 30 m observations do not detect CO emission in either the (1-0) or (3-2) transitions. We place 3σ limits on the molecular gas mass of Mmol ≤ 7.7 × 109 M⊙ and ≤5.6 × 109 M⊙ from the two lines respectively. We find indications of a recent minor cluster merger that has left a ∼200 kpc tail of stripped gas in the ICM, and probably induced sloshing motions.

Keywords: galaxy clusters; radio galaxies; active galactic nuclei; intracluster medium; brightest cluster galaxies
Evolution of CAI-sized Particles during FU Orionis Outbursts. I. Particle Trajectories in Protoplanetary Disks with Beta Cooling

Solar-type young stellar objects undergo periodic, energetic outbursts that appear to be the result of enhanced mass accretion driven by the gravitational instability of their disks. Such FU Orionis outbursts may have profound consequences for the earliest solids in a protoplanetary disk, namely the refractory inclusions containing abundant calcium and aluminum (CAIs). We present models of the orbital evolution of centimeter-radius particles representing large CAIs in marginally gravitationally unstable disks. The hydrodynamical evolution of the disks is calculated with a fully three-dimensional code, including compressional heating and cooling in the beta cooling approximation. The particles are initially distributed uniformly throughout the disk, which extends from 1 to 10 au around a solar-mass protostar, but within ∼100 yr the particles are concentrated by gas drag into regions surrounding the spiral arms and rings formed by the gas disk. The particles settle down toward the disk midplane, only to be lofted repeatedly upward by shock fronts. Large-scale radial transport both outward and inward occurs, with significant numbers of particles reaching the outer disk (∼10 au) and surviving for considerably longer times than would be the case in a quiescent disk with gas pressure monotonically decreasing with distance from the protostar. Individual particles experience wide ranges of disk temperatures during their journeys, ranging from 60 K in the outer disk to nearly 2000 K in spiral features. Future work will consider the implications for CAI rims of the thermochemical processing experienced during FU Orionis outbursts.

Keywords: protoplanetary disks; stellar accretion disks; hydrodynamical simulations; planet formation; gravitational instability
Interstellar Communication Network. I. Overview and Assumptions

It has recently been suggested in this journal by Benford that "Lurkers" in the form of interstellar exploration probes could be present in the solar system. Similarly, extraterrestrial intelligence could send long-lived probes to many other stellar systems to report back science and surveillance. If probes and planets with technological species exist in more than a handful of systems in our Galaxy, it is beneficial to use a coordinated communication scheme. Due to the inverse square law, data rates decrease strongly for direct connections over long distances. The network bandwidth could be increased by orders of magnitude if repeater stations (nodes) are used in an optimized fashion. This introduction to a series of papers makes the assumptions of the communication scheme explicit. Subsequent papers will discuss technical aspects such as transmitters, repeaters, wavelengths, and power levels. The overall purpose is to gain insight into the physical characteristics of an interstellar communication network, allowing us to describe the most likely sizes and locations of nodes and probes.

Keywords: deep space probes
V899 Mon: A Peculiar Eruptive Young Star Close to the End of Its Outburst

The eruptive young star V899 Mon shows characteristics of both FUors and EXors. It reached a peak brightness in 2010, then briefly faded in 2011, followed by a second outburst. We conducted multifilter optical photometric monitoring, as well as optical and near-infrared spectroscopic observations, of V899 Mon. The light curves and color-magnitude diagrams show that V899 Mon has been gradually fading after its second outburst peak in 2018, but smaller accretion bursts are still happening. Our spectroscopic observations taken with Gemini/IGRINS and VLT/MUSE show a number of emission lines, unlike during the outbursting stage. We used the emission line fluxes to estimate the accretion rate and found that it has significantly decreased compared to the outbursting stage. The mass-loss rate is also weakening. Our 2D spectroastrometric analysis of emission lines recovered jet and disk emission of V899 Mon. We found that the emission from permitted metallic lines and the CO bandheads can be modeled well with a disk in Keplerian rotation, which also gives a tight constraint for the dynamical stellar mass of 2 M ⊙. After a discussion of the physical changes that led to the changes in the observed properties of V899 Mon, we suggest that this object is finishing its second outburst.

Keywords: young stellar objects; fu orionis stars; circumstellar disks; multi-color photometry; photometry; spectroscopy; light curves
Numerical Simulation of Photospheric Emission in Long Gamma-Ray Bursts: Prompt Correlations, Spectral Shapes, and Polarizations

We explore the properties of photospheric emission in the context of long gamma-ray bursts (GRBs) using three numerical models that combine relativistic hydrodynamical simulations and Monte Carlo radiation transfer calculations in three dimensions. Our simulations confirm that photospheric emission gives rise to correlations between the spectral peak energy and luminosity that agree with the observed Yonetoku, Amati, and Golenetskii correlations. It is also shown that the spectral peak energy and luminosity correlate with the bulk Lorentz factor, as indicated in the literature. On the other hand, synthetic spectral shapes tend to be narrower than those of the observations. This result indicates that an additional physical process that can provide nonthermal broadening is needed to reproduce the spectral features. Furthermore, the polarization analysis finds that, while the degree of polarization is low for the emission from the jet core (Π < 4%), it tends to increase with viewing angle outside of the core and can be as high as Π ∼ 20%–40% in an extreme case. This suggests that the typical GRBs show systematically low polarization compared to softer, dimmer counterparts (X-ray-rich GRBs and X-ray flashes). Interestingly, our simulations indicate that photospheric emission exhibits large temporal variation in the polarization position angle (Δψ ∼ 90°), which may be compatible with those inferred in observations. A notable energy dependence of the polarization property is another characteristic feature found in the current study. Particularly, the difference in the position angle among different energy bands can be as large as ∼90°.

Keywords: gamma-ray bursts; radiative transfer simulations; hydrodynamical simulations
3D Numerical Simulation of Kink-driven Rayleigh-Taylor Instability Leading to Fast Magnetic Reconnection

Fast magnetic reconnection involving non-MHD microscale physics is believed to underlie both solar eruptions and laboratory plasma current disruptions. While there is extensive research on both the MHD macroscale physics and the non-MHD microscale physics, the process by which large-scale MHD couples to the microscale physics is not well understood. An MHD instability cascade from a kink to a secondary Rayleigh-Taylor instability in the Caltech astrophysical jet laboratory experiment provides new insights into this coupling and motivates a 3D numerical simulation of this transition from large to small scale. A critical finding from the simulation is that the axial magnetic field inside the current-carrying dense plasma must exceed the field outside. In addition, the simulation verifies a theoretical prediction and experimental observation that, depending on the strength of the effective gravity produced by the primary kink instability, the secondary instability can be Rayleigh-Taylor or mini-kink. Finally, it is shown that the kink-driven Rayleigh-Taylor instability generates a localized electric field sufficiently strong to accelerate electrons to very high energy.

Keywords: magnetohydrodynamical simulations; magnetohydrodynamics; laboratory astrophysics; experimental models; plasma astrophysics
Large-scale Turbulent Driving Regulates Star Formation in High-redshift Gas-rich Galaxies

The question of what regulates star formation is a longstanding issue. To investigate this issue, we run simulations of a kiloparsec cube section of a galaxy with three kinds of stellar feedback: the formation of H II regions, the explosion of supernovae, and ultraviolet heating. We show that stellar feedback is sufficient to reduce the averaged star formation rate (SFR) to the level of the Schmidt-Kennicutt law in Milky Way-like galaxies but not in high-redshift gas-rich galaxies, suggesting that another type of support should be added. We investigate whether an external driving of the turbulence such as the one created by the large galactic scales could diminish the SFR at the observed level. Assuming that the Toomre parameter is close to 1 as suggested by the observations, we infer a typical turbulent forcing that we argue should be applied parallel to the plane of the galactic disk. When this forcing is applied in our simulations, the SFR within our simulations closely follows the Schmidt-Kennicutt relation. We found that the velocity dispersion is strongly anisotropic with the velocity dispersion alongside the galactic plane being up to 10 times larger than the perpendicular velocity.

Keywords: star formation; galaxy dynamics; galaxy physics; interstellar medium; radiative transfer simulations; magnetohydrodynamical simulations
Event Rate of Fast Radio Bursts from Binary Neutron Star Mergers

It is proposed that a one-off fast radio burst (FRB) with periodic structure may be produced during the inspiral phase of a binary neutron star (BNS) merger. In this paper, we study the event rate of such kind of FRB. We first investigate the properties of two one-off FRBs with periodic structure (i.e., FRB 20191221A and FRB 20210213A) in this scenario, by assuming a fast magnetosonic wave is responsible for their radio emission. For the luminosities and periods of these bursts, it is found that for the NSs in the premerger BNS, magnetic field strengths of B ≳ 1012 G are required. This is relatively high compared with those of most of the BNSs observed in our Galaxy, of which their magnetic fields are around 109 G. Since the observed BNSs in our Galaxy are binaries that have not suffered a merger, a credible event rate of BNS-merger-originated FRBs should be estimated by considering the evolution of both the BNS systems and their magnetic fields. Based on population synthesis and adopting decaying magnetic fields of the NSs, we estimate the event rate of BNS mergers relative to their final magnetic fields. We find that rapidly merging BNSs tend to merge with high magnetization, and the event rate of BNS-merger-originated FRBs, i.e., BNS mergers with both NSs' magnetic fields being higher than 1012 G, is ~8 × 104 yr-1 (19% of all BNS mergers) for redshifts z < 1.

Keywords: radio transient sources; close binary stars; neutron stars; magnetic fields
Rapid Ortho-to-para Nuclear Spin Conversion of H2 on a Silicate Dust Surface

The H2 molecule has two nuclear spin isomers, the so-called ortho and para isomers. Nuclear spin conversion (NSC) between these states is forbidden in the gas phase. The energy difference between the lowest ortho and para states is as large as 14.7 meV, corresponding to ∼170 K. Therefore, each state of H2 differently affects not only the chemistry but also the macroscopic gas dynamics in space; thus, the ortho-to-para abundance ratio (OPR) of H2 has significant impacts on various astronomical phenomena. For a long time, the OPR of nascent H2 upon formation on dust grains has been assumed to have a statistical value of 3 and to gradually equilibrate in the gas phase at the temperature of the circumstances. Recently, the NSC of H2 was experimentally revealed to occur on water ice at very low temperatures and thus incorporated into gas-dust chemical models. However, H2 molecules should form well before dust grains are coated by water ice. Information about how the OPR of H2 behaves on bare silicate dust before ice-mantle formation is lacking. Knowing the influence of the OPR of H2 is desirable, if the OPR changes even on a bare silicate surface within an astronomically meaningful timescale. We report the first laboratory measurements of the NSC of H2 physisorbed on amorphous silicate (Mg2SiO4) at temperatures up to 18 K. The conversion was found to occur very rapidly.

Keywords: astrochemistry; molecular clouds; dense interstellar clouds; interstellar molecules; interstellar dust; laboratory astrophysics
A Simulation Study of Ultra-relativistic Jets. II. Structures and Dynamics of FR-II Jets

We study the structures of ultra-relativistic jets injected into the intracluster medium and the associated flow dynamics, such as shocks, velocity shear, and turbulence, through three-dimensional relativistic hydrodynamic (RHD) simulations. To that end, we have developed a high-order accurate RHD code, equipped with a weighted essentially non-oscillatory scheme and a realistic equation of state. Using the code, we explore a set of jet models with the parameters relevant to FR-II radio galaxies. We confirm that the overall jet morphology is primarily determined by the jet power, and the jet-to-background density and pressure ratios play secondary roles. Jets with higher powers propagate faster, resulting in more elongated structures, while those with lower powers produce more extended cocoons. Shear interfaces in the jet are dynamically unstable, and hence, chaotic structures with shocks and turbulence develop. We find that the fraction of the jet-injected energy dissipated through shocks and turbulence is greater in less powerful jets, although the actual amount of the dissipated energy is larger in more powerful jets. In lower power jets, the backflow is dominant in the energy dissipation owing to the broad cocoon filled with shocks and turbulence. In higher power jets, by contrast, both the backflow and jet-spine flow are important for the energy dissipation. Our results imply that different mechanisms, such as diffusive shock acceleration, shear acceleration, and stochastic turbulent acceleration, may be involved in the production of ultra-high energy cosmic rays in FR-II radio galaxies.

Keywords: relativistic fluid dynamics; relativistic jets; radio galaxies; hydrodynamical simulations; cosmic rays
The Most Ordinary Formation of the Most Unusual Double Black Hole Merger

The Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo Collaboration reported the detection of the most massive black hole-black hole (BH-BH) merger to date with component masses of 85M⊙ and 66M⊙ (GW190521). Motivated by recent observations of massive stars in the 30 Doradus cluster in the Large Magellanic Cloud (M⋆ ≳ 200M⊙; e.g., R136a) and employing newly estimated uncertainties on pulsational pair-instability mass loss (that allow for the possibility of forming BHs with mass up to MBH ∼ 90M⊙), we show that it is trivial to form such massive BH-BH mergers through the classical isolated binary evolution (with no assistance from either dynamical interactions or exotica). A binary consisting of two massive (180M⊙ + 150M⊙) Population II stars (metallicity: Z ≈ 0.0001) evolves through a stable Roche lobe overflow and common envelope episode. Both exposed stellar cores undergo direct core collapse and form massive BHs while avoiding pair-instability pulsation mass loss or total disruption. LIGO/Virgo observations show that the merger rate density of light BH-BH mergers (both components: MBH < 50M⊙) is of the order of 10-100Gpc-3yr-1, while GW190521 indicates that the rate of heavier mergers is 0.02-0.43Gpc-3yr-1. Our model (with standard assumptions about input physics), but extended to include 200M⊙ stars and allowing for the possibility of stellar cores collapsing to 90M⊙ BHs, produces the following rates: 63Gpc-3yr-1 for light BH-BH mergers and 0.04Gpc-3yr-1 for heavy BH-BH mergers. We do not claim that GW190521 was formed by an isolated binary, but it appears that such a possibility cannot be excluded.

Keywords: black hole physics; stellar evolution; stellar remnants