adsabs/SciX_UAT_keywords huggingface dataset:
Prospects for Measuring Off-axis Spins of Binary Black Holes with Plus-era Gravitational-wave Detectors

The mass and spin properties of binary black holes (BBHs) inferred from their gravitational-wave signatures reveal important clues about how these systems form. BBHs originating from isolated binary evolution are expected to have spins preferentially aligned with their orbital angular momentum, whereas there is no such preference in binaries formed via dynamical assembly. The fidelity with which near-future gravitational-wave detectors can measure off-axis spins will have implications for the study of BBH formation channels. In this work, we examine the degree to which the Advanced LIGO Plus (A+) and Advanced Virgo Plus (AdV+) interferometric detectors can measure both aligned and misaligned spins. We compare spin resolution between the LIGO-Virgo network operating at either A+/AdV+ ("Plus") sensitivity or Advanced-era design ("Design") sensitivity using simulated BBH gravitational-wave signals injected into synthetic detector noise. The signals are distributed over the mass-spin parameter space of likely BBH systems, accounting for the effects of precession and higher-order modes. We find that the Plus upgrades yield significant improvements in spin estimation for systems with unequal masses and moderate or large spins. Using simulated signals modeled after different types of hierarchical BBH mergers, we also conclude that the Plus detector network will yield substantially improved spin estimates for 1G+2G binaries compared to the Design network.

Keywords: gravitational waves; compact binary stars; stellar mass black holes
Localized Magnetic-field Structures and Their Boundaries in the Near-Sun Solar Wind from Parker Solar Probe Measurements

One of the discoveries of the Parker Solar Probe during its first encounters with the Sun is ubiquitous presence of relatively small-scale structures standing out as sudden deflections of the magnetic field. They were named "switchbacks" since some of them show a full reversal of the radial component of the magnetic field and then return to "regular" conditions. We carried out an analysis of three typical switchback structures having different characteristics: I. Alfvénic structure, where the variations of the magnetic field components take place while conserving the magnitude of the magnetic field; II. Compressional structure, where the magnitude of the field varies together with changes of its components; and III. Structure manifesting full reversal of the magnetic field, presumably Alfvén, which is an extremal example of a switchback. We analyzed the properties of the magnetic fields of these structures and of their boundaries. Observations and analyses lead to the conclusion that they represent localized twisted magnetic tubes moving with respect to surrounding plasma. An important feature is the existence of a relatively narrow boundary layer at the surface of the tube that accommodates flowing currents. These currents are closed on the surface of the structure and typically have comparable azimuthal and tube-axis-aligned components. They are supported by the presence of an effective electric field due to strong gradients of the density and ion plasma pressure. The ion beta is typically larger inside the structure than outside. The surface of the structure may also accommodate electromagnetic waves that assist particles in carrying currents.

Keywords: alfven waves
VLBI Observations of Supernova PTF11qcj: Direct Constraints on the Size of the Radio Ejecta

We present High Sensitivity Array and enhanced Multi-Element Remotely Linked Interferometer Network observations of the radio-loud broad-lined Type Ic supernova PTF11qcj obtained ∼7.5 yr after the explosion. Previous observations of this supernova at 5.5 yr since explosion showed a double-peaked radio light curve accompanied by a detection in the X-rays, but no evidence for broad Hα spectral features. The Very Long Baseline Interferometry (VLBI) observations presented here show that the PTF11qcj GHz radio ejecta remains marginally resolved at the submilliarcsecond level ≈7.5 yr after the explosion, pointing toward a nonrelativistic expansion. Our VLBI observations thus favor a scenario in which the second peak of the PTF11qcj radio light curve is related to the strong interaction of the supernova ejecta with a circumstellar medium of variable density, rather than to the emergence of an off-axis jet. Continued VLBI monitoring of PTF11qcj in the radio may further strengthen this conclusion.

Keywords: type ic supernovae; very long baseline interferometry; gamma-ray bursts; stellar astronomy
Eight-year Simultaneous Monitoring Observations of H2O and SiO Masers toward V627 Cas

Simultaneous monitoring observations of H2O 61,6 - 52,3 and SiO v = 1, 2, J = 1 → 0, v = 1, J = 2 → 1, J = 3 → 2 masers were performed toward the suspected D-type symbiotic star V627 Cas from 2011 October to 2020 March using the Korean Very Long Baseline Interferometry (VLBI) Network (KVN) single-dish telescopes. All spectra of the H2O masers showed highly redshifted emissions with respect to the stellar velocity of -52 km s-1 with high asymmetries. In addition, the spectra of the H2O maser showed three components which varied according to observational dates. On the other hand, the SiO v = 1, 2, J = 1 → 0 and v = 1, J = 2 → 1 masers exhibited a predominantly blueshifted emission in most epochs. The SiO v = 1, J = 3 → 2 maser has arisen around the stellar velocity from 2016 November 19 and shows a predominantly redshifted emission from 2018 June 15. We analyze time variations of the H2O and SiO maser intensities, their intensity ratios, peak and mean velocities, and full width zero power. Based on these analyses, the asymmetries of the H2O and SiO masers' spectra in V627 Cas and the variation characteristics of the maser properties of the different maser lines are discussed. As a possible cause of asymmetries, the influence of a hot component located at the eastern part of the red giant can be suggested based on the KVN VLBI results. The differences in the variation characteristics of the maser properties may originate from the differences in their locations and excitation conditions.

Keywords: circumstellar masers; symbiotic binary stars; water masers; silicon monoxide masers
Two Different Weak Modulations in ab-type RR Lyrae Variable V838 Cyg, and Potential Influence of Metal Abundance on Blazhko Modulation

Noting the weakest modulation and relatively high metal abundance of the ab-type RR Lyrae star V838 Cyg, we collected the photometric data of this star from several sky surveys to carry out an in-depth analysis. The O - C diagram shows that the pulsation period of V838 Cyg increases linearly over a long timescale. In a reanalysis of the high-precision Kepler data, we confirmed the modulation with a period of 59.45 ± 0.07 days found by Benkő et al., and also found an additional weak modulation with a longer period (840 ± 21 days). After a series of analyses, we incline to the view that the mechanisms causing the two modulations are different: the former is more similar to the typical Blazhko effect, while the mechanism leading to the latter may be an extrinsic factor. We also collected and compared the modulation and physical parameters of other Blazhko RR Lyrae stars from several works in the literature, and find that there is a potential negative correlation between the modulation amplitude (or upper limit of amplitude) and the metal abundance. We infer that the relatively high metal abundance will promote convection in the outer stellar atmosphere, and then inhibit those factors (turbulence, shock wave, etc.) that may cause Blazhko modulation. Future observations and research work can be carried out with reference to this viewpoint. We also introduce the moiré effects that appear in the Kepler long-cadence light curves and their possible interference in the previous analyses.

Keywords: rr lyrae variable stars; photometry; fundamental parameters of stars; space telescopes
A Subsurface Magma Ocean on Io: Exploring the Steady State of Partially Molten Planetary Bodies

Intense tidal heating within Io produces active volcanism on the surface, and its internal structure has long been a subject of debate. A recent reanalysis of the Galileo magnetometer data suggested the presence of a high-melt-fraction layer with >50 km thickness in the subsurface region of Io. Whether this layer is a "magmatic sponge" with interconnected solid or a rheologically liquid "magma ocean" would alter the distribution of tidal heating and would also influence the interpretation of various observations. To this end, we explore the steady state of a magmatic sponge and estimate the amount of internal heating necessary to sustain such a layer with a high degree of melting. Our results show that the rate of tidal dissipation within Io is insufficient to sustain a partial-melt layer of ϕ > 0.2 for a wide range of parameters, suggesting that such a layer would swiftly separate into two phases. Unless melt and/or solid viscosities are at the higher end of the estimated range, a magmatic sponge would be unstable, and thus a high-melt-fraction layer suggested in Khurana et al. is likely to be a subsurface magma ocean.

Keywords: galilean satellites; io; planetary interior
Red Supergiant Stars in IC 1613 and Metallicity-dependent Mixing Length in the Evolutionary Model

We report a spectroscopic study on red supergiant stars (RSGs) in the irregular dwarf galaxy IC 1613 in the Local Group. We derive the effective temperatures (T eff) and metallicities of 14 RSGs by synthetic spectral fitting to the spectra observed with the MMIRS instrument on the MMT telescope for a wavelength range from 1.16 to 1.23 μm. A weak bimodal distribution of the RSG metallicity centered on [Fe/H] = -0.65 is found, which is slightly lower than or comparable to that of the Small Magellanic Cloud (SMC). There is no evidence for spatial segregation between the metal-rich ([Fe/H] > -0.65) and -poor ([Fe/H] < -0.65) RSGs throughout the galaxy. The mean effective temperature of our RSG sample in IC 1613 is higher by about 250 K than that of the SMC. However, no correlation between T eff and metallicity within our RSG sample is found. We calibrate the convective mixing length (α MLT) by comparing stellar evolutionary tracks with the RSG positions on the H-R diagram, finding that models with α MLT = 2.2-2.4H P can best reproduce the effective temperatures of the RSGs in IC 1613 for both Schwarzschild and Ledoux convection criteria. This result supports our previous finding that a metallicity-dependent mixing length is needed to explain the RSG temperatures observed in the Local Group, but we find that this dependence becomes relatively weak for RSGs having a metallicity equal to or less than the SMC metallicity.

Keywords: red supergiant stars; late-type supergiant stars; dwarf irregular galaxies
Constraints on the Distances and Timescales of Solid Migration in the Early Solar System from Meteorite Magnetism

The migrations of solid objects throughout the solar system are thought to have played key roles in disk evolution and planet formation. However, our understanding of these migrations is limited by a lack of quantitative constraints on their timings and distances recovered from laboratory measurements of meteorites. The protoplanetary disk supported a magnetic field that decreased in intensity with heliocentric distance. As such, the formation distances of the parent asteroids of ancient meteorites can potentially be constrained by paleointensity measurements of these samples. Here, we find that the WIS 91600 ungrouped C2 chondrite experienced an ancient field intensity of 4.4 ± 2.8 μT. Combined with the thermal history of this meteorite, magnetohydrodynamical models suggest the disk field reached 4.4 μT at ∼9.8 au, indicating that the WIS 91600 parent body formed in the distal solar system. Because WIS 91600 likely came to Earth from the asteroid belt, our recovered formation distance argues that this body previously traveled from ∼10 au to 2-3 au, supporting the migration of asteroid-sized bodies throughout the solar system. WIS 91600 also contains chondrules, calcium-aluminum-rich inclusions and amoeboid olivine aggregates, indicating that some primitive millimeter-sized solids that formed in the innermost solar system migrated outward to ∼10 au within ∼3-4 Myr of solar system formation. Moreover, the oxygen isotopic compositions of proposed distal meteorites (WIS 91600, Tagish Lake and CI chondrites) argue that the CM, CO, and CR chondrites contain micrometer-scale dust and ice that originated in the distal solar system.

Keywords: meteorites; magnetic fields; primordial magnetic fields; asteroid belt; kuiper belt; protoplanetary disks; chondrules; chondrites
REST: A Java Package for Crafting Realistic Cosmic Dust Particles

The overall understanding of cosmic dust particles is mainly inferred from the different Earth-based measurements of interplanetary dust particles and space missions such as Giotto, Stardust, and Rosetta. The results from these measurements indicate the presence of a wide variety of morphologically significant dust particles. To interpret the light-scattering and thermal emission observations arising due to dust in different regions of space, it is necessary to generate computer-modeled realistic dust structures of various shapes, sizes, porosity, bulk density, aspect ratio, and material inhomogeneity. The present work introduces a Java package called Rough Ellipsoid Structure Tool (REST), which is a collection of multiple algorithms, that aims to craft realistic rough-surface cosmic dust particles from spheres, superellipsoids, and fractal aggregates depending on the measured bulk density and porosity. Initially, spheres having N d dipoles or lattice points are crafted by selecting random material and space seed cells to generate a strongly damaged structure, rough surface, and poked structure. Similarly, REST generates rough-surface superellipsoids and poked structure superellipsoids from initial superellipsoid structures. REST also generates rough fractal aggregates, which are fractal aggregates having rough-surface irregular grains. REST has been applied to create agglomerated debris, agglomerated debris superellipsoids, and mixed-morphology particles. Finally, the light-scattering properties of the respective applied structures are studied to ensure their applicability. REST is a flexible structure tool that shall be useful for generating various types of dust structures that can be applied to studying the physical properties of dust in different regions of space.

Keywords: dust physics; interplanetary dust; circumstellar dust; interstellar dust; radiative transfer simulations; software available on request
The Lowest-frequency Fast Radio Bursts: Sardinia Radio Telescope Detection of the Periodic FRB 180916 at 328 MHz

We report on the lowest-frequency detection to date of three bursts from the fast radio burst FRB 180916.J0158+65, observed at 328 MHz with the Sardinia Radio Telescope (SRT). The SRT observed the periodic repeater FRB 180916.J0158+65 for five days from 2020 February 20 to 24 during a time interval of active radio bursting, and detected the three bursts during the first hour of observations; no more bursts were detected during the remaining ∼30 hr. Simultaneous SRT observations at 1548 MHz did not detect any bursts. Burst fluences are in the range 37 to 13 Jy ms. No relevant scattering is observed for these bursts. We also present the results of the multi-wavelength campaign we performed on FRB 180916.J0158+65, during the five days of the active window. Simultaneously with the SRT observations, others with different time spans were performed with the Northern Cross at 408 MHz, with XMM-Newton, NICER, INTEGRAL, AGILE, and with the TNG and two optical telescopes in Asiago, which are equipped with fast photometers. XMM-Newton obtained data simultaneously with the three bursts detected by the SRT, and determined a luminosity upper limit in the 0.3-10 keV energy range of ∼1045 erg s-1 for the burst emission. AGILE obtained data simultaneously with the first burst and determined a fluence upper limit in the MeV range for millisecond timescales of ${10}^{-8}\,\mathrm{erg}\,{\mathrm{cm}}^{-2}$ . Our results show that absorption from the circumburst medium does not significantly affect the emission from FRB 180916.J0158+65, thus limiting the possible presence of a superluminous supernova around the source, and indicate that a cutoff for the bursting mechanism, if present, must be at lower frequencies. Our multi-wavelength campaign sensitively constrains the broadband emission from FRB 180916.J0158+65, and provides the best limits so far for the electromagnetic response to the radio bursting of this remarkable source of fast radio bursts.

Keywords: radio transient sources
Dissecting the Phase Space Snail Shell

The ongoing vertical phase-mixing, manifesting itself as a snail shell in the $Z-{V}_{Z}$ phase space, has been discovered with Gaia DR2 data. To better understand the origin and properties of the phase-mixing process, we study the vertical phase-mixing signatures in arches (including the classical "moving groups") of the ${V}_{R}-{V}_{\phi }$ phase space near the solar circle. Interestingly, the phase space snail shell exists only in the arches with $| {V}_{\phi }-{V}_{\mathrm{LSR}}| \,\lesssim 30$ km s-1, I.e., stars on dynamically "colder" orbits. The snail shell becomes much weaker and eventually disappears for increasingly larger radial action (JR), quantifying the "hotness" of orbits. Thus, one should pay closer attention to the colder orbits in future phase-mixing studies. We also confirm that the Hercules stream has two branches (at fast and slow Vφ), which may not be explained by a single mechanism, since only the fast branch shows the prominent snail shell feature. The hotter orbits may have phase-wrapped away already due to the much larger dynamical range in radial variation to facilitate faster phase-mixing. To explain the lack of a well-defined snail shell in the hotter orbits, the disk should have been perturbed at least 500 Myr ago. Our results offer more support to the recent satellite-disk encounter scenario than the internal bar-buckling perturbation scenario as the origin of the phase space mixing. The origin of the more prominent snail shell in the Vφ color-coded phase space is also discussed.

Keywords: milky way dynamics; milky way disk; galaxy structure; galaxy disks
Modeling Rotational Disruption of Grains and Microwave Emission from Spinning Dust in AGB Envelopes

Radio observations of some asymptotic giant branch (AGB) star envelopes show excess emission at frequencies below 100 GHz that cannot be explained by thermal dust emission (hereafter anomalous microwave emission (AME)). Moreover, AGB envelopes are a common place where gas molecules condense to form nanoparticles (e.g., polycyclic aromatic hydrocarbons) and large grains. In this paper, we study whether electric dipole emission from rapidly spinning nanoparticles can reproduce the AME observed toward AGB stars. To properly model the size distribution of nanoparticles in the AGB envelope, we take into account both the increase of nanoparticles due to rotational disruption of large grains spun up by radiative torques and the decrease of the smallest nanoparticles due to rotational disruption driven by stochastic gas collisions. We then perform detailed modeling of microwave emission from rapidly spinning nanoparticles from both C-rich and O-rich AGB envelopes using the grain-size distribution constrained by rotational disruption. We find that spinning dust emission is dominant over thermal dust emission at frequencies below 100 GHz. We attempt to fit the observational data of AME using our spinning dust model and demonstrate that spinning dust can reproduce the observed AME in six AGB stars. Finally, we discuss how microwave emission from spinning dust in AGB envelopes could be observed with high-resolution upcoming radio telescopes such the Next Generation Very Large Array and Atacama Large Millimeter/submillimeter Array Band 1. This would be a major leap for understanding AGB envelopes' formation, evolution, and internal structures of dust. Observations would help to distinguish the carrier of AME via comparisons of C-rich and O-rich stars, because polycyclic aromatic hydrocarbons (PAHs) are formed in C-rich AGB stars, while silicates are formed in O-rich stars.

Keywords: circumstellar envelopes; interstellar dust extinction; asymptotic giant branch stars; radio continuum emission; interstellar extinction
Dual-band, Multi-aperture Polarization Measurements of β Pictoris

We present high precision, dual-band aperture polarimetry of the β Pictoris debris disk. The polarization is aperture dependent, increasing from 5″ to 19″ and peaking, after interstellar subtraction at around 230–240 ppm in both $g^{\prime} $ and $r^{\prime} $ bands; the polarization vector is oriented perpendicular to the disk major-axis. By simple calculations, lower limits are placed on the polarization of scattered light interior to 200 au. The observations and calculations are consistent with prior spatially resolved polarimetric measurements of the disk that probe greater angular separations, and models for the interior developed from them.

Keywords: circumstellar dust; debris disks; polarimetry; starlight polarization
Toward a Direct Measure of the Galactic Acceleration

High-precision spectrographs can enable not only the discovery of exoplanets, but can also provide a fundamental measurement in Galactic dynamics. Over about 10 year baselines, the expected change in the line-of-sight velocity due to the Galaxy's gravitational field for stars at ∼kiloparsec scale distances above the Galactic midplane is ∼few tens of cm s-1, and may be detectable by the current generation of high-precision spectrographs. Here, we provide theoretical expectations for this measurement based on both static models of the Milky Way and isolated Milky Way simulations, as well from controlled dynamical simulations of the Milky Way interacting with dwarf galaxies. We simulate a population synthesis model to analyze the contribution of planets and binaries to the Galactic acceleration signal. We find that while low-mass, long-period planetary companions are a contaminant to the Galactic acceleration signal, their contribution is very small. Our analysis of ∼10 years of data from the Lick-Carnegie Exoplanet Survey HIRES/Keck precision radial-velocity (RV) survey shows that slopes of the RV curves of standard RV stars agree with expectations of the local Galactic acceleration near the Sun within the errors, and that the error in the slope scales inversely as the square root of the number of observations. Thus, we demonstrate that a survey of stars with low intrinsic stellar jitter at kiloparsec distances above the Galactic midplane for realistic sample sizes can enable a direct determination of the dark matter density.

Keywords: dark matter; dark matter density; exoplanets; exoplanet astronomy
Rapid Postshock Cooling and Pressure-driven Shell-phase Evolution of the Galactic Halo SNR G70.0-21.5

The large, faint supernova remnant (SNR) G70.0-21.5 is believed to be the result of a Type Ia supernova some 90,000 yr ago at a distance of ∼1 kpc based on the Gaia proper motion and parallax of an unusual white dwarf. We have obtained narrow passband optical images and high-resolution spectroscopy to determine shock speeds of 70 to 110 km s-1. The shock itself is unusual in that the sharp Hα filaments arise from a very thin postshock zone where preshock neutral atoms are rapidly excited and ionized. Combining the shock speed with the remnant's estimated age, distance, and diameter, we investigate the SNR evolution in the post-Sedov phase. One-dimensional models that ignore such factors as magnetic fields, cosmic rays, and thermal conduction are marginally consistent with the observations.

Keywords: supernova remnants; shocks