adsabs/SciX_UAT_keywords huggingface dataset:
The Adaptive Optics System for the Gemini Infrared Multi-Object Spectrograph: Performance Modeling

The Gemini Infrared Multi-Object Spectrograph (GIRMOS) will be a near-infrared, multi-object, medium spectral resolution, integral field spectrograph (IFS) for Gemini North Telescope, designed to operate behind the future Gemini North Adaptive Optics system (GNAO). In addition to a first ground layer Adaptive Optics (AO) correction in closed loop carried out by GNAO, each of the four GIRMOS IFSs will independently perform additional multi-object AO correction in open loop, resulting in an improved image quality that is critical to achieve top level science requirements. We present the baseline parameters and simulated performance of GIRMOS obtained by modeling both the GNAO and GIRMOS AO systems. The image quality requirement for GIRMOS is that 57% of the energy of an unresolved point-spread function ensquared within a 0.1 × 0.1 arcsecond at 2.0 μ m. It was established that GIRMOS will be an order 16 × 16 adaptive optics (AO) system after examining the tradeoffs between performance, risks and costs. The ensquared energy requirement will be met in median atmospheric conditions at Maunakea at 30° from zenith.

Keywords: astronomical instrumentation; astronomical simulations; telescopes
A Self-consistent Simulation of Proton Acceleration and Transport Near a High-speed Solar Wind Stream

Solar wind stream interaction regions (SIRs) are often characterized by energetic ion enhancements. The mechanisms accelerating these particles, as well as the locations where the acceleration occurs, remain debated. Here, we report the findings of a simulation of a SIR event observed by Parker Solar Probe at ∼0.56 au and the Solar Terrestrial Relations Observatory-Ahead at ∼0.95 au in 2019 September when both spacecraft were approximately radially aligned with the Sun. The simulation reproduces the solar wind configuration and the energetic particle enhancements observed by both spacecraft. Our results show that the energetic particles are produced at the compression waves associated with the SIR and that the suprathermal tail of the solar wind is a good candidate to provide the seed population for particle acceleration. The simulation confirms that the acceleration process does not require shock waves and can already commence within Earth's orbit, with an energy dependence on the precise location where particles are accelerated. The three-dimensional configuration of the solar wind streams strongly modulates the energetic particle distributions, illustrating the necessity of advanced models to understand these particle events.

Keywords: solar wind; corotating streams; interplanetary particle acceleration
On the Nature of Propagating Intensity Disturbances in Polar Plumes during the 2017 Total Solar Eclipse

The propagating intensity disturbances (PIDs) in plumes are still poorly understood, and their identity (magnetoacoustic waves or flows) remains an open question. We investigate PIDs in five plumes located in the northern polar coronal hole observed during the 2017 total solar eclipse. Three plumes are associated with coronal bright points, jets, and macrospicules at their base (active plumes), and the other two plumes are not (quiet plumes). The electron temperature at the base of the plumes is obtained from the filter ratio of images taken with the X-ray Telescope on board Hinode and the passband ratio around 400 nm from an eclipse instrument, the Diagnostic Coronagraph Experiment. The phase speed (vr), frequency (ω), and wavenumber (k) of the PIDs in the plumes are obtained by applying a Fourier transformation to the spacetime (r - t plane) plots in images taken with the Atmospheric Imaging Assembly (AIA) in three different wavelength channels (171, 193, and 211 Å). We found that the PIDs in the higher-temperature AIA channels, 193 and 211 Å, are faster than that of the cooler AIA 171 Å channel. This tendency is more significant for the active plumes than the quiet ones. The observed speed ratio (∼1.3) between the AIA 171 and 193 Å channels is similar to the theoretical value (1.25) of a slow magnetoacoustic wave. Our results support the idea that PIDs in plumes represent a superposition of slow magnetoacoustic waves and plasma outflows that consist of dense cool flows and hot coronal jets.

Keywords: solar coronal waves; solar coronal plumes; x-ray bright point; solar eclipses; fast solar wind; solar coronal holes; solar coronal heating
Polarimetry of GRB 230818A

We present a preliminary analysis of optical photometric and polarimetric observations of GRB 230818A obtained with the Liverpool Telescope starting 3.2 minutes after the alert. The optical photometry suggests a reverse shock-dominated afterglow, transitioning to forward shock at around 15 minutes. The polarization shows a low degree (upper limit 6%) early in the light curve. This is in contrast to the expected result since this regime should be dominated by the reverse shock wave that, in turn, should present a higher degree of polarization.

Keywords: gamma-ray transient sources; gamma-ray bursts; stellar jets
Convective Overstability in Radially Global Protoplanetary Disks. I. Pure Gas Dynamics

Protoplanetary disks are prone to several hydrodynamic instabilities. One candidate, convective overstability (COS), can drive radial semiconvection that may influence dust dynamics and planetesimal formation. However, the COS has primarily been studied in local models. This paper investigates the COS near the midplane of radially global disk models. We first conduct a global linear stability analysis, which shows that linear COS modes exist only radially inward of their Lindblad resonance (LR). The fastest-growing modes have LRs near the inner radial domain boundary with effective radial wavelengths that can be a substantial fraction of the disk radius. We then perform axisymmetric global simulations and find that the COS's nonlinear saturation is similar to previous incompressible shearing box simulations. In particular, we observe the onset of persistent zonal and elevator flows for sufficiently steep radial entropy gradients. In full 3D, nonaxisymmetric global simulations, we find the COS produces large-scale, long-lived vortices, which induce the outward radial transport of angular momentum via the excitation of spiral density waves. The corresponding α-viscosity values of order 10‑3 agree well with those found in previous 3D compressible shearing box simulations. However, in global disks, significant modifications to their radial structure are found, including the formation of pressure bumps. Interestingly, the COS typically generates an outward radial mass transport, i.e., decretion. We briefly discuss the possible implications of our results for planetesimal formation and for interpreting dust rings and asymmetries observed in protoplanetary disks.

Keywords: protoplanetary disks; hydrodynamics; astrophysical fluid dynamics; planet formation; planetesimals
The Correlation between Black Hole Mass and Stellar Mass for Classical Bulges and the Cores of Ellipticals

The correlation between black hole mass and the stellar mass of the bulge of the host galaxy has attracted much attention ever since its discovery. While traditional investigations of this correlation have treated elliptical galaxies as single, monolithic spheroids, the recent realization that massive elliptical galaxies have undergone significant late-time ( $z\lesssim 2$ ) dissipationless assembly since their initially dense "red nugget" phase strongly suggests that black holes in present-day ellipticals should be associated only with their cores and not with their extended envelopes. We perform two-dimensional image decomposition of Two Micron All Sky Survey Ks-band images to derive the stellar mass of the cores of 35 nearby ellipticals with reliably measured black hole masses. We revisit the relation between black hole mass and bulge stellar mass by combining classical bulges with the cores of ellipticals. The new relation exhibits nearly identical slope ( ${M}_{\bullet }\propto {M}_{\mathrm{core}}^{1.2}$ ) as the conventional relation but a factor of ∼2 higher normalization and moderately larger intrinsic scatter (0.4 dex). At a core mass of ${10}^{11}\,{M}_{\odot }$ , ${M}_{\bullet }/{M}_{\mathrm{core}}=0.9 \% $ , but it rises to ${M}_{\bullet }/{M}_{\mathrm{core}}=1.5 \% $ for the most massive cores with mass ${10}^{12}\,{M}_{\odot }$ . Fast and slow rotator ellipticals follow the same correlation. The ${M}_{\bullet }\mbox{--}{M}_{\mathrm{core}}$ relation provides a revised benchmark for studies of black hole-galaxy coevolution in the high-redshift universe.

Keywords: supermassive black holes; active galaxies; galaxy evolution; galaxy photometry; galaxy structure; elliptical galaxies; galaxy bulges; scaling relations
Latest Evolution of the X-Ray Remnant of SN 1987A: Beyond the Inner Ring

Based on our Chandra imaging-spectroscopic observations, we present the latest evolution of the X-ray remnant of SN 1987A. Recent changes in the electron temperatures and volume emission measures suggest that the blast wave in SN 1987A is moving out of the dense inner ring structure, also called the equatorial ring (ER). The 0.5–2.0 keV X-ray light curve shows a linearly declining trend (by ∼4.5% yr‑1) between 2016 and 2020 as the blast wave heats the hitherto unknown circumstellar medium (CSM) outside the ER. While the peak X-ray emission in the latest 0.3–8.0 keV image is still within the ER, the radial expansion rate in the 3.0–8.0 keV images suggests an increasing contribution of the X-ray emission from less dense CSM since 2012, at least partly from beyond the ER. It is remarkable that, since 2020, the declining soft X-ray flux has stabilized around ∼7 × 10‑12 erg s‑1 cm‑2, which may signal a contribution from the reverse-shocked outer layers of ejecta as predicted by the three-dimensional magnetohydrodynamic models. In the latest ACIS spectrum of supernova remnant 1987A in 2022 we report a significant detection of the Fe K line at ∼6.7 keV, which may be due to changing thermal conditions of the X-ray emitting CSM and/or the onset of reverse shock interactions with the Fe ejecta.

Keywords: supernova remnants; core-collapse supernovae
Optical Variability of the TeV Blazar 1ES 0806+524 on Diverse Timescales

We report the results of our optical (VRI) photometric observations of the TeV blazar 1ES 0806+524 on 153 nights during 2011-2019 using seven optical telescopes in Europe and Asia. We investigated the variability of the blazar on intraday as well as on long-term timescales. We examined 18 intraday light curves for flux and color variations using the most reliable power-enhanced F-test and the nested ANOVA test. Only on one night was a small, but significant, variation found, in both V-band and R-band light curves. The V-R color index was constant on every one of those nights. Flux density changes of around 80% were seen over the course of these eight years in multiple bands. We found a weighted mean optical spectral index of 0.639 ± 0.002 during our monitoring period by fitting a power law ( ${F}_{\nu }\propto {\nu }^{-\alpha }$ ) in 23 optical (VRI) spectral energy distributions of 1ES 0806+524. We discuss different possible mechanisms responsible for blazar variability on diverse timescales.

Keywords: active galactic nuclei; blazars; observational astronomy; ccd photometry; radio loud quasars; active galaxies; optical observation; relativistic jets; optical telescopes; bl lacertae objects
The Breakthrough Listen Search for Intelligent Life: A 3.95-8.00 GHz Search for Radio Technosignatures in the Restricted Earth Transit Zone

We report on a search for artificial narrowband signals of 20 stars within the restricted Earth Transit Zone (rETZ) as a part of the ten-year Breakthrough Listen (BL) search for extraterrestrial intelligence (ETI). The rETZ is the region of the sky from which an observer would see Earth transit the Sun with an impact parameter of less than 0.5. This region of the sky is geometrically unique, providing a potential way for an ETI to discover the solar system. The targets were nearby (7-143 pc) and the search covered an electromagnetic frequency range of 3.95-8.00 GHz. We used the Robert C. Byrd Green Bank Telescope to perform these observations with the standard BL data recorder. We searched these data for artificial narrowband (∼Hz) signals with Doppler drift rates of ±20 Hz s-1. We find no evidence for radio technosignatures from ETI in our observations. The observing campaign would have allowed for detections of emissions that were 10-3 to 0.88 times as powerful as the signaling capability of the Arecibo radar transmitter. We conclude that at least 0.6% of the systems in the rETZ within 150 pc do not possess the type of transmitters searched in this survey. To our knowledge, this is the first targeted search for ETI of the rETZ. All data used in this paper are publicly available via the BL Public Data Archive (http://seti.berkeley.edu/bldr2).

Keywords: technosignatures; radio astronomy; astrobiology; search for extraterrestrial intelligence
Mode Mixing and Rotational Splittings. II. Reconciling Different Approaches to Mode Coupling

In the mixed-mode asteroseismology of subgiants and red giants, the coupling between the p- and g-mode cavities must be understood well in order to derive localized estimates of interior rotation from measurements of mode multiplet rotational splittings. There exist now two different descriptions of this coupling: one based on an asymptotic quantization condition, and the other arising from the coupling matrices associated with "acoustic molecular orbitals." We examine the analytic properties of both, and derive closed-form expressions for various quantities-such as the period-stretching function τ-which previously had to be solved for numerically. Using these, we reconcile both formulations for the first time, deriving relations by which quantities in each formulation may be translated to and interpreted within the other. This yields an information criterion for whether a given configuration of mixed modes may meaningfully constrain the parameters of the asymptotic construction, which is likely not satisfied by the majority of first-ascent red giant stars in our observational sample. Since this construction has been already used to make rotational measurements of such red giants, we examine-through a hare-and-hounds exercise-whether, and how, such limitations affect these existing measurements. While averaged estimates of core rotation seem fairly robust, template-matching using the asymptotic construction has difficulty reliably assigning rotational splittings to individual multiplets, or estimating the mixing fractions ζ of the most p-dominated mixed modes, where such estimates are most needed. We finally discuss implications for extending the two-zone model of radial differential rotation, e.g., via rotational inversions, with these methods.

Keywords: asteroseismology; stellar oscillations; red giant stars; theoretical techniques; computational methods
Numerical Simulation of Hot Accretion Flows. IV. Effects of Black Hole Spin and Magnetic Field Strength on the Wind and the Comparison between Wind and Jet Properties

This is the fourth paper of our series studying winds from hot accretion flows around black holes. In the first two papers, we showed the existence of strong winds in hot accretion flows using hydrodynamical and magnetohydrodynamical (MHD) simulations. In the third paper, by using three-dimensional general relativity MHD numerical simulation data of hot accretion flows and adopting a "virtual particle trajectory" data analysis approach, we calculated the properties of wind, such as its mass flux and velocity. However, that paper focuses only on a nonspinning black hole and standard and normal accretion. In the present paper, we extend the third paper by including cases of a rapidly rotating black hole and magnetically arrested disk. We focus on investigating the effect of spin and magnetic field on the properties of the wind and jet. It is found that a larger spin and stronger magnetic field usually enhance the wind and jet. The formulae describing the mass flux, poloidal velocity, and fluxes of momentum, kinetic energy, and total energy of the wind and jet are presented. One interesting finding, among others, is that even in the case of a very rapidly spinning black hole, where the jet is supposed to be the strongest, the momentum flux of the jet is smaller than that of the wind, while the total energy flux of the jet is larger than that of the wind by at most a factor of 10. This result suggests that the wind potentially plays a more important role than the jet, at least for some problems in active galactic nucleus feedback.

Keywords: high energy astrophysics
Complex Water-ice Mixtures on NII Nereid: Constraints from NIR Reflectance

Nereid, Neptune's third-largest satellite, lies in an irregular orbit and is the only outer satellite in the system (apart from Triton) that can be spectroscopically characterized with the current generation of Earth-based telescopes. We report our results on the spectral characterization of Nereid using its reflectance spectrum from 0.8 to 2.4 μm, providing the first measurements over the range of 0.8-1.4 μm. We detect spectral absorption features of crystalline water ice in close agreement with previous measurements. We show that model fits of simple intimate mixtures including water ice do not provide simultaneous matches to absorption band depths at 1.5 and 2.0 μm when accounting for the spectral continuum. Possible solutions include invoking a more complex continuum, including both crystalline and amorphous water ice, and allowing for submicron-sized grains. We show that mixtures including magnetite and the CM2 chondrite Murchison provide a flexible framework for interpreting spectral variation of bodies with neutral-sloped spectra like that of Nereid. Magnetite in particular provides a good match to the spectral continuum without requiring the presence of tholin-like organics. We note that carbonaceous chondrites and their components may be useful analogs for the non-ice components of outer solar system bodies, consistent with recent findings by Fraser et al. Comparison to spectra of large trans-Neptunian objects and satellites of Uranus show that Nereid's low albedo, deep water bands, and neutral color is distinct from many other icy objects, but such comparisons are limited by an incomplete understanding of spectral variability among ~100 km-sized icy bodies.

Keywords: irregular satellites; natural satellites (solar system); neptunian satellites; near infrared astronomy; small solar system bodies
Discovery of 34 Low-mass Comoving Systems Using NOIRLab Source Catalog DR2

We present the discovery of 34 comoving systems containing an ultracool dwarf found by means of the NOIRLab Source Catalog (NSC) DR2. NSC's angular resolution of ~ 1″ allows for the detection of small separation binaries with significant proper motions. We used the catalog's accurate proper motion measurements to identify the companions by cross-matching a previously compiled list of brown dwarf candidates with NSC DR2. The comoving pairs consist of either a very low-mass star and an ultracool companion, or a white dwarf and an ultracool companion. The estimated spectral types of the primaries are in the K and M dwarf regimes, those of the secondaries in the M, L, and T dwarf regimes. We calculated angular separations between ~2″ and ~ 56″, parallactic distances between ~43 and ~261 pc, and projected physical separations between ~169 and ~8487 au. The lowest measured total proper motion is 97 mas yr-1, with the highest 314 mas yr-1. Tangential velocities range from ~23 to ~187 km s-1. We also determined comoving probabilities, estimated mass ratios, and calculated binding energies for each system. We found no indication of possible binarity for any component of the 34 systems in the published literature. The discovered systems can contribute to the further study of the formation and evolution of low-mass systems as well as to the characterization of cool substellar objects.

Keywords: binary stars; multiple stars; low mass stars; brown dwarfs; white dwarf stars
Mode Mixing and Rotational Splittings. I. Near-degeneracy Effects Revisited

Rotation is typically assumed to induce strictly symmetric rotational splitting into the rotational multiplets of pure p- and g-modes. However, for evolved stars exhibiting mixed modes, avoided crossings between different multiplet components are known to yield asymmetric rotational splitting, in particular for near-degenerate mixed-mode pairs, where notional pure p-modes are fortuitously in resonance with pure g-modes. These near-degeneracy effects have been described in subgiants, but their consequences for the characterization of internal rotation in red giants have not previously been investigated in detail, in part owing to theoretical intractability. We employ new developments in the analytic theory of mixed-mode coupling to study these near-resonance phenomena. In the vicinity of the most p-dominated mixed modes, the near-degenerate intrinsic asymmetry from pure rotational splitting increases dramatically over the course of stellar evolution, and it depends strongly on the mode-mixing fraction ζ. We also find that a linear treatment of rotation remains viable for describing the underlying p- and g-modes, even when it does not for the resulting mixed modes undergoing these avoided crossings. We explore observational consequences for potential measurements of asymmetric mixed-mode splitting, which has been proposed as a magnetic-field diagnostic. Finally, we propose improved measurement techniques for rotational characterization, exploiting the linearity of rotational effects on the underlying p/g-modes, while still accounting for these mixed-mode coupling effects.

Keywords: asteroseismology; computational methods; theoretical techniques; stellar rotation; stellar magnetic fields
Erosion and Accretion by Cratering Impacts on Rocky and Icy Bodies

During planet formation, numerous small impacting bodies result in cratering impacts on large target bodies. A fraction of the target surface is eroded, while a fraction of the impactor material accretes onto the surface. These fractions depend upon the impact velocities, the impact angles, and the escape velocities of the target. This study uses smoothed particle hydrodynamics simulations to model cratering impacts onto a planar icy target for which gravity is the dominant force and material strength is neglected. By evaluating numerical results, scaling laws are derived for the escape mass of the target material and the accretion mass of the impactor material onto the target surface. Together with recently derived results for rocky bodies in a companion study, a conclusion is formulated that typical cratering impacts on terrestrial planets, except for those on Mercury, led to a net accretion, while those on the moons of giant planets, e.g., Rhea and Europa, led to a net erosion. Our newly derived scaling laws would be useful for predicting the erosion of the target body and the accretion of the impactor for a variety of cratering impacts that would occur on large rocky and icy planetary bodies during planet formation and collisional evolution from ancient times to today.

Keywords: impact phenomena; planetary science; planet formation; dynamical evolution; planetary surfaces; surface processes