adsabs/SciX_UAT_keywords huggingface dataset:
The Width, Density, and Outflow of Solar Coronal Streamers

Characterizing the large-scale structure and plasma properties of the inner corona is crucial to understanding the source and subsequent expansion of the solar wind and related space weather effects. Here, we apply a new coronal rotational tomography method, along with a method to narrow streamers and refine the density estimate, to COR2A/Solar Terrestrial Relations Observatory observations from a period near solar minimum and maximum, gaining density maps for heights between 4 and 8R⊙. The coronal structure is highly radial at these heights, and the streamers are very narrow: in some regions, only a few degrees in width. The mean densities of streamers is almost identical between solar minimum and maximum. However, streamers at solar maximum contain around 50% more total mass due to their larger area. By assuming a constant mass flux, and constraints on proton flux measured by Parker Solar Probe (PSP), we estimate an outflow speed within solar minimum streamers of 50-120 kms-1 at 4R⊙, increasing to 90-250 kms-1 at 8R⊙. Accelerations of around 6 ms-2 are found for streamers at a height of 4R⊙, decreasing with height. The solar maximum slow wind shows a higher acceleration to extended distances compared with solar minimum. To satisfy the solar wind speeds measured by PSP, there must be a mean residual acceleration of around 1-2 ms-2 between 8 and 40R⊙. Several aspects of this study strongly suggest that the coronal streamer belt density is highly variable on small scales, and that the tomography can only reveal a local spatial and temporal average.

Keywords: solar corona; quiet solar corona; solar coronal streamers; astronomical methods; computational astronomy; optical astronomy; coronagraphic imaging; solar wind; solar physics
New Growth Mechanism of Dust Grains in Protoplanetary Disks with Magnetically Driven Disk Winds

We discovered a new growth mode of dust grains to kilometer-size bodies in protoplanetary disks that evolve via viscous accretion and magnetically driven disk winds (MDWs). We solved an approximate coagulation equation of dust grains with time-evolving disks that consist of both gas and solid components using a one-dimensional model. With grain growth, all solid particles initially drift inward toward the central star due to the gas drag force. However, the radial profile of gas pressure, P, is modified by the MDW that disperses the gas in an inside-out manner. Consequently, a local concentration of solid particles is created by the converging radial flux of drifting dust grains at the location with a convex-upward profile of P. When the dimensionless stopping time, St, exceeds unity there, the solid particles spontaneously reach the growth-dominated state because of the positive feedback between the suppressed radial drift and the enhanced accumulation of dust particles that drift from the outer part. Once the solid particles are in the drift-limited state, the above-mentioned condition of St $\gtrsim \,1$ for dust growth is equivalent to Σd/Σg ≳ η, where Σd/Σg is the dust-to-gas surface-density ratio and η is the dimensionless radial pressure-gradient force. As a consequence of the successful growth of dust grains, a ring-like structure containing planetesimal-size bodies is formed at the inner part of the protoplanetary disks. Such a ring-shaped concentration of planetesimals is expected to play a vital role in the subsequent planet formation.

Keywords: planet formation; planetary system formation; protoplanetary disks; planetesimals
Geometric Distances of Quasars Measured by Spectroastrometry and Reverberation Mapping: Monte Carlo Simulations

Recently, GRAVITY on board the Very Large Telescope Interferometer (VLTI) first spatially resolved the structure of the quasar 3C 273 with an unprecedented resolution of ∼10 μas. A new method of measuring parallax distances has been successfully applied to the quasar through joint analysis of spectroastrometry (SA) and reverberation mapping (RM) observation of its broad-line region (BLR). The uncertainty of this SA and RM (SARM) measurement is about 16% from real data, showing its great potential as a powerful tool for precision cosmology. In this paper, we carry out detailed analyses of mock data to study impacts of data qualities of SA observations on distance measurements and establish a quantitative relationship between statistical uncertainties of distances and relative errors of differential phases. We employ a circular disk model of the BLR for the SARM analysis. We show that SARM analyses of observations generally generate reliable quasar distances, even for relatively poor SA measurements with error bars of 40% at peaks of phases. Inclinations and opening angles of BLRs are the major parameters governing distance uncertainties. It is found that BLRs with inclinations ≳10° and opening angles ≲40° are the most reliable regimes from SARM analysis for distance measurements. Through analysis of a mock sample of AGNs generated by quasar luminosity functions, we find that if the GRAVITY/GRAVITY+ can achieve a phase error of 0°1 per baseline for targets with magnitudes K ≲ 11.5, the SARM campaign can constrain H0 to an uncertainty of 2% by observing 60 targets.

Keywords: distance measure; reverberation mapping; optical interferometry; hubble constant
SPISEA: A Python-based Simple Stellar Population Synthesis Code for Star Clusters

We present Stellar Population Interface for Stellar Evolution and Atmospheres (SPISEA), an open-source Python package that simulates simple stellar populations. The strength of SPISEA is its modular interface which offers the user control of 13 input properties including (but not limited to) the initial mass function, stellar multiplicity, extinction law, and the metallicity-dependent stellar evolution and atmosphere model grids used. The user also has control over the initial-final mass relation in order to produce compact stellar remnants (black holes, neutron stars, and white dwarfs). We demonstrate several outputs produced by the code, including color-magnitude diagrams, HR-diagrams, luminosity functions, and mass functions. SPISEA is object-oriented and extensible, and we welcome contributions from the community. The code and documentation are available on GitHub (https://github.com/astropy/SPISEA) and ReadtheDocs (https://spisea.readthedocs.io/en/latest/), respectively.

Keywords: astronomy software; open source software; star clusters; stellar populations
Calcium-rich Transient SN 2019ehk in a Star-forming Environment: Yet Another Candidate for a Precursor of a Double Neutron-star Binary

We present optical and near-infrared observations of SN 2019ehk, which was initially reported as a Type Ib supernova (SN). We show that it evolved to a Ca-rich transient according to its spectral properties and evolution in late phases. However, it shows a few properties distinct from those of the canonical Ca-rich transients: a short-duration first peak in the light curve, high peak luminosity, and association with a star-forming environment. Indeed, some of these features are shared with iPTF14gqr and iPTF16hgs, which are candidates for a special class of core-collapse SNe: the so-called ultra-stripped envelope SNe, i.e., a relatively low-mass He (or C+O) star explosion in a binary as a precursor of short-period double neutron star (NS) binaries. The estimated ejecta mass (0.4M⊙) and explosion energy (1.7 × 1050 erg) are consistent with this scenario. The analysis of the first peak suggests the existence of dense circumstellar material in the vicinity of the progenitor, implying a CCSN origin. Based on this analysis, we suggest SN 2019ehk is another candidate for a low-mass He star explosion. It might create a double NS binary, but with a wide separation. These candidates for low-mass stripped envelope SNe, including ultra-stripped envelope SN candidates, seem to form a subpopulation among Ca-rich transients, associated with young population. We propose that the key to distinguishing this population is the early first peak in their light curves.

Keywords: supernovae
Hunting for Hydrated Minerals on Trans-Neptunian Objects

We present new optical reflectance spectra of three potentially silicate-rich trans-Neptunian objects (TNOs). These spectra were obtained with the aim of confirming past hints and detections of λ ∼ 0.7 μm absorption features associated with the presence of iron-bearing phyllosilicates. Our new spectrum of 120216 (2004 EW95) presents clearly detected absorption features that are similar in shape to hydrated mineral absorption bands present in the spectra of aqueously altered outer main belt asteroids. Four new reflectance spectra of 208996 (2003 AZ84) obtained at separate epochs all appear featureless, but they vary significantly in spectral gradient (between ∼3.5%/0.1 μm and ∼8.5%/0.1 μm) on a timescale consistent with this object's nominal rotational period. We report the first four optical reflectance spectra of 90568 (2004 GV9), finding them all to be featureless but consistent with colors previously reported for this object. We speculate that impacts are the only mechanism capable of delivering, excavating, or forming hydrated minerals at the surfaces of TNOs in detectable concentrations; as a result, any deposits of hydrated minerals on TNOs are predicted to be localized and associated with impact sites. Globally altered TNOs (as observationally suggested for 2004 EW95) plausibly formed more easily at smaller heliocentric distances (r H < 15 au) before being transplanted into the current trans-Neptunian population.

Keywords: trans-neptunian objects; planetary thermal histories; asteroids; spectroscopy
Sample and Statistical Analysis of the Near-Earth Object Wide-field Infrared Survey Explorer Variability of the 6.7 GHz Methanol Maser Sources

We present a statistical study of infrared variability using the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) database for a sample consisting of 1085 high-mass young stellar objects (YSOs) related to 6.7 GHz methanol masers. A total of 383 maser sources were identified as NEOWISE variables and classified in two variability behavior classifications: 204 secular (linear, curved, and periodic) and 179 stochastic (burst, drop, and irregular) variables. Statistical analysis of the properties of these variables (e.g., the dust temperature, bolometric luminosity, hydrogen column density, W4 luminosity, and W1-W2 color) has revealed a potential evolutionary sequence among different light-curve types of variables. There is a possible general evolutionary (from less to more evolved) trend between the three variable types from secular to stochastic to nonvariable. For the specific classifications, the evolutionary trend for secular variables is linear to sin to sin+linear, and for stochastic variables it is burst to irregular to drop. These sequences may reflect the evolution of the envelope or accretion disk of high-mass YSOs, from large to small radii due to gravitational collapse. Although no significant variability correlation was established between the 6.7 GHz methanol maser and the W2-band emission based on the data collected so far, a number of candidates were found for further investigating the accretion burst events via future variability monitoring programs of both mid-infrared emission and masers.

Keywords: young stellar objects; massive stars; interstellar masers; infrared photometry
Strongly Lensed Supermassive Black Hole Binaries as Nanohertz Gravitational-wave Sources

Supermassive black hole binary systems (SMBHBs) should be the most powerful sources of gravitational waves (GWs) in the universe. Once pulsar timing arrays (PTAs) detect the stochastic GW background from their cosmic merger history, searching for individually resolvable binaries will take on new importance. Since these individual SMBHBs are expected to be rare, here we explore how strong gravitational lensing can act as a tool for increasing their detection prospects by magnifying fainter sources and bringing them into view. Unlike for electromagnetic waves, when the geometric optics limit is nearly always valid, for GWs the wave-diffraction-interference effects can become important when the wavelength of the GWs is larger than the Schwarzchild radius of the lens, i.e., ${M}_{\mathrm{lens}}\sim {10}^{8}{\left(\tfrac{f}{\mathrm{mHz}}\right)}^{-1}\,{M}_{\odot }$ . For the GW frequency range explored in this work, the geometric optics limit holds. We investigate GW signals from SMBHBs that might be detectable with current and future PTAs under the assumption that quasars serve as bright beacons that signal a recent merger. Using the black hole mass function derived from quasars and a physically motivated magnification distribution, we expect to detect a few strongly lensed binary systems out to z ≈ 2. Additionally, for a range of fixed magnifications 2 ≤ μ ≤ 100, strong lensing adds up to ~30 more detectable binaries for PTAs. Finally, we investigate the possibility of observing both time-delayed electromagnetic signals and GW signals from these strongly lensed binary systems-that will provide us with unprecedented multi-messenger insights into their orbital evolution.

Keywords: gravitational lensing; gravitational wave sources; gravitational wave astronomy; gravitational wave detectors; quasars; pulsar timing method
Influence of Ion-Neutral Damping on the Cosmic-Ray Streaming Instability: Magnetohydrodynamic Particle-in-cell Simulations

We explore the physics of the gyroresonant cosmic-ray streaming instability (CRSI) including the effects of ion-neutral (IN) damping. This is the main damping mechanism in (partially ionized) atomic and molecular gas, which are the primary components of the interstellar medium (ISM) by mass. Limitation of CRSI by IN damping is important in setting the amplitude of Alfvén waves that scatter cosmic rays (CRs) and control galactic-scale transport. Our study employs the magnetohydrodynamic (MHD)-particle-in-cell hybrid fluid-kinetic numerical technique to follow linear growth as well as post-linear and saturation phases. During the linear phase of the instability-where simulations and analytical theory are in good agreement-IN damping prevents wave growth at small and large wavelengths, with the unstable bandwidth lower for higher IN collision rates νin. Purely MHD effects during the post-linear phase extend the wave spectrum toward larger k. In the saturated state, the CR distribution evolves toward greater isotropy (lower streaming velocity) by scattering off of Alfvén waves excited by the instability. In the absence of low-k waves, CRs with sufficiently high momentum are not isotropized. The maximum wave amplitude and rate of isotropization of the distribution function decrease at higher νin. When the IN damping rate approaches the maximum growth rate of CRSI, wave growth and isotropization are suppressed. Implications of our results for CR transport in partially ionized ISM phases are discussed.

Keywords: cosmic rays; magnetic fields; computational methods
Fast Luminous Blue Transients in the Reionization Era and Beyond

To determine the epoch of reionization precisely and to reveal the property of inhomogeneous reionization are some of the most important topics of modern cosmology. Existing methods to investigate reionization that use cosmic microwave background, Lyα emitters, quasars, or gamma-ray bursts have difficulties in terms of accuracy or event rate. We propose that recently discovered fast luminous blue transients (FLBTs) have potential as a novel probe of reionization. We study the detectability of FLBTs at the epoch of reionization with upcoming WFIRST Wide-Field Instrument, using a star formation rate (SFR) derived from galaxy observations and an event rate of FLBTs proportional to the SFR. We find that if FLBTs occur at a rate of 1% of the core-collapse supernova rate, 2 (0.3) FLBTs per year per deg2 at z > 6 (z > 8) can be detected by a survey with a limiting magnitude of 26.5 mag in the near-infrared band and a cadence of 10 days. We conclude that the WFIRST supernova deep survey can detect ∼20 FLBTs at the epoch of reionization in the near future.

Keywords: reionization; early universe; transient sources; high energy astrophysics
Probing Shocked Ejecta in SN 1987A: A Novel Diagnostic Approach Using XRISM-Resolve

Supernova (SN) 1987A is one of the best candidates to exploit the capabilities of the freshly launched XRISM satellite. This celestial object offers the unique opportunity to study the evolution of an SN into a young supernova remnant. To date, the X-ray emission has been dominated by the shocked circumstellar medium, with no shocked ejecta firmly detected. However, recent studies provide compelling evidence that in the forthcoming years, the X-ray emission from SN 1987A will increasingly stem from the ejecta. Our aim is to assess the proficiency of the XRISM-Resolve high-resolution spectrometer in pinpointing signatures of the shocked ejecta in SN 1987A. Taking advantage of a self-consistent state-of-the-art magneto-hydrodynamic simulation that describes the evolution from SN 1987A to its remnant, we synthesized the XRISM-Resolve spectrum of SN 1987A, as it would be collected in the allocated observation during the performance verification phase, which is foreseen for 2024. Our predictions clearly show the leading role of shocked ejecta in shaping the profile of the emission lines. The Doppler broadening associated with the bulk motion along the line of sight of the rapidly expanding ejecta is shown to increase the line widths well above the values observed so far. The quantitative comparison between our synthetic spectra and the XRISM spectra will enable us to establish a strong connection between the broadened line emission and the freshly shocked ejecta. This, in turn, will allow us to retrieve the ejecta dynamics and chemical composition from the X-ray emission.

Keywords: interstellar medium; supernova remnants; high energy astrophysics; plasma astrophysics
The ArgusSpec Prototype: Autonomous Spectroscopic Follow-up of Flares Detected by Large Array Telescopes

ArgusSpec is a prototype autonomous spectroscopic follow-up instrument designed to characterize flares detected by the Argus Pathfinder telescope array by taking short exposure (30 s) broadband spectra (370–750 nm) at low resolutions (R ∼ 150 at 500 nm). The instrument is built from consumer off-the-shelf astronomical equipment, assembled inside a shipping container, and deployed alongside the Argus Pathfinder at a dark sky observing site in Western North Carolina. In this paper, we describe the hardware design, system electronics, custom control software suite, automated target acquisition procedure, and data reduction pipeline. We present initial on-sky test data used to evaluate system performance and show a series of spectra taken of a small flare from AD Leonis. The $35k prototype ArgusSpec was designed, built, and deployed in under a year, largely from existing parts, and has been operating on-sky since 2023 March. With current hardware and software, the system is capable of receiving an observation, slewing, performing autonomous slit acquisition, and beginning data acquisition within an average of 32 s. With Argus Pathfinder's 1 s cadence survey reporting alerts of rising sources within 2 s of onset, ArgusSpec can reach new targets well within a minute of the start of the event. As built, ArgusSpec can observe targets down to a 20σ limiting magnitude of m V ≈ 13 at 30 s cadence with an optical resolution of R ∼ 150 (at 500 nm). With automated rapid acquisition demonstrated, later hardware upgrades will be based on a clean-sheet optical design, solving many issues in the current system, significantly improving the limiting magnitude, and potentially enabling deep spectroscopy by the coaddition of data from an array of ArgusSpec systems. The primary science driver behind ArgusSpec is the characterization of the blackbody evolution of flares from nearby M-dwarfs. Large flares emitted by these stars could have significant impacts on the potential habitability of any orbiting exoplanets, but our current understanding of these events is in large part built on observations from a handful of active stars. ArgusSpec will characterize large numbers of flares from across the night sky, building a spectroscopic library of the most extreme events from a wide variety of stellar masses and ages.

Keywords: astronomical instrumentation; automated telescopes; stellar flares
Blind Search of the Solar Neighborhood Galactic Disk within 5 kpc: 1179 New Star Clusters Found in Gaia DR3

Studying open clusters (OCs) may help to provide a comprehensive understanding of the structure and evolution of the Milky Way. Many previous studies have systematically searched for OCs near the solar system within 1.2 kpc or 20° of Galactic latitude. However, few studies have searched for OCs at higher Galactic latitudes and deeper distances. In this study, based on a hybrid unsupervised clustering algorithm (friends-of-friends and pyUPMASK) and a binary classification algorithm (random forest), we extended the search region (i.e., Galactic latitude $\left|b\right|\geqslant 20^\circ )$ and performed a fine-grained blind search for Galactic clusters in Gaia DR3. After crossmatching, the newly discovered cluster candidates are fitted using isochrone fitting to estimate the main physical parameters (i.e., age and metallicity) of these clusters. These cluster candidates were then checked using manual visual inspection. Their statistical properties were also compared with previously exposed cluster catalogs. We found 1179 new clusters with considerable confidence within 5 kpc.

Keywords: open star clusters; star clusters
NGDEEP Epoch 1: Spatially Resolved Hα Observations of Disk and Bulge Growth in Star-forming Galaxies at z ∼ 0.6–2.2 from JWST NIRISS Slitless Spectroscopy

We study the Hα equivalent width (EW(Hα)) maps of 19 galaxies at 0.6 < z < 2.2 in the Hubble Ultra Deep Field using NIRISS slitless spectroscopy as part of the Next Generation Deep Extragalactic Exploratory Public Survey. Our galaxies mostly lie on the star formation main sequence with stellar masses between 109 and 1011 M ⊙, characterized as "typical" star-forming galaxies at these redshifts. Leveraging deep Hubble Space Telescope and JWST images, spanning 0.4–4.8 μm, we perform spatially resolved fitting of the spectral energy distributions for these galaxies and construct specific star formation rate (sSFR) and stellar-mass-weighted age maps with a spatial resolution of ∼1 kpc. The pixel-to-pixel EW(Hα) increases with increasing sSFR and with decreasing age. The average trends are slightly different from the relations derived from integrated fluxes of galaxies from the literature, suggesting complex evolutionary trends within galaxies. We quantify the radial profiles of EW(Hα), sSFR, and age. The majority (84%) of galaxies show positive EW(Hα) gradients, in line with the inside-out quenching scenario. A few galaxies (16%) show inverse (and flat) EW(Hα) gradients, possibly due to merging or starbursts. We compare the distributions of EW(Hα) and sSFR to star formation history (SFH) models as a function of galactocentric radius. We argue that the central regions of galaxies have experienced at least one rapid star formation episode, which leads to the formation of the bulge, while their outer regions (e.g., disks) grow via more smoothly varying SFHs. These results demonstrate the ability to study resolved star formation in distant galaxies with JWST NIRISS.

Keywords: high-redshift galaxies; star formation; galaxy stellar content; galaxy evolution