Sazuna/UAT_keywords huggingface dataset:
Determining the Spectral Content of MOSES Images. The Multi-Order Solar Extreme Ultraviolet Spectrograph (MOSES) sounding rocket was launched from White Sands Missile Range on 2006 February 8th, to capture images of the Sun in the He II 303.8 Å emission line. MOSES is a slitless spectrograph that forms images in multiple spectral orders simultaneously using a concave diffraction grating in an effort to measure line profiles over a wide field of view from a single exposure. Early work on MOSES data showed evidence of solar features composed of neither He II 303.8 Å nor the nearby Si XI 303.3 Å spectral lines. We have built a forward model that uses cotemporal EIT images and the Chianti atomic database to fit synthetic images with known spectra to the MOSES data in order to quantify this additional spectral content. Our fit reveals a host of dim lines that alone are insignificant but combined contribute a comparable intensity to MOSES images as Si XI 303.3 Å. In total, lines other than He II 303.8 Å and Si XI 303.3 Å contribute approximately 10% of the total intensity in the MOSES zero order image. This additional content, if not properly accounted for, could significantly impact the analysis of MOSES and similar slitless spectrograph data, especially those using a zero-order (undispersed) image. More broadly, this serves as a reminder that multilayer EUV imagers are sensitive to a host of weak contaminant lines.

Keywords: Solar instruments, Solar transition region
Gaussian Processes and Effective Field Theory of f(T) Gravity under the H <SUB>0</SUB> Tension. We consider the effective field theory formulation of torsional gravity in a cosmological framework to alter the background evolution. Then we use the latest H 0 measurement from the SH0ES Team, as well as observational Hubble data from cosmic chronometer and radial baryon acoustic oscillations, and we reconstruct the f(T) form in a model-independent way by applying Gaussian processes. Since the special square-root term does not affect the evolution at the background level, we finally summarize a family of functions that can produce the background evolution required by the data. Lastly, performing a fitting using polynomial functions and implementing the Bayesian information criterion, we find an analytic expression that may describe the cosmological evolution in great agreement with observations.

Keywords: Cosmology, Cosmological parameters, Non-standard theories of gravity, Hubble constant, Dark energy
Y Gem: A White Dwarf Symbiotic Star?. In this work we conduct a thorough investigation of the X-ray and ultraviolet (UV) properties of Y Gem based on six archival XMM-Newton and Chandra observations to explore the nature of the system. The results show that Y Gem has strong (1032-34 erg s-1) X-ray emission, including a hard (with a maximum emission temperature of 8-16 keV) and a soft (with emission temperatures of 0.02-0.2 and 0.2-0.9 keV) component. The integrated UV luminosity of Y Gem reaches ~1035 erg s-1. We show that the previous asymptotic giant branch-main-sequence (AGB-MS) Roche-lobe overflow (RLOF) scenario is dynamically unstable and can hardly explain the ~10 keV X-ray emission temperature. We propose Y Gem as a symbiotic star, where a white dwarf (WD) accretes from its AGB companion based on its X-ray and UV properties. We make numerical simulations to examine the evolutionary history of this system. The simulations can produce the observed properties of Y Gem in the wind WRLOF scenario. An ~0.8M ☉ WD with a ~1.0-1.8M ☉ companion in a ~2000-32,000 day initial orbit may evolve to a Y Gem-like system. Our finding implies a potential population of symbiotic stars that may have been misclassified as AGB-MS binaries. What is more, their high mass accretion rates may enable mass accumulation to the WD and makes them candidates of Type Ia supernovae progenitors.

Keywords: White dwarf stars, Symbiotic binary stars, X-ray sources
Radiation Effects from the Interstellar Medium and Cosmic Ray Particle Impacts on Relativistic Spacecraft. Relativistic spacecraft, like those proposed by the NASA Starlight program and the Breakthrough Starshot Initiative, will have to survive radiation production that is unique when compared to that experienced by conventional spacecraft. In a relativistic interstellar spacecraft's reference frame, the interstellar medium (ISM) will look like a nearly monoenergetic beam of charged particles which impinges upon the leading edge of the spacecraft. Upon impact, ISM protons and electrons will travel characteristic lengths through the spacecraft shield and come to a stop via electronic and nuclear stopping mechanisms. As a result, bremsstrahlung photons will be produced within the spacecraft shield. In this work, we discuss the interstellar environment and its implications for radiation damage on relativistic spacecraft. We also explore expected radiation doses in terms of onboard device radiation tolerance.

Keywords: Interstellar dust, Deep space probes, Space probes, Astronomical radiation sources, Interstellar medium, Cosmic rays
Constraining Global Coronal Models with Multiple Independent Observables. Global coronal models seek to produce an accurate physical representation of the Sun's atmosphere that can be used, for example, to drive space-weather models. Assessing their accuracy is a complex task, and there are multiple observational pathways to provide constraints and tune model parameters. Here, we combine several such independent constraints, defining a model-agnostic framework for standardized comparison. We require models to predict the distribution of coronal holes at the photosphere, and neutral line topology at the model's outer boundary. We compare these predictions to extreme-ultraviolet (EUV) observations of coronal hole locations, white-light Carrington maps of the streamer belt, and the magnetic sector structure measured in situ by Parker Solar Probe and 1 au spacecraft. We study these metrics for potential field source surface (PFSS) models as a function of source surface height and magnetogram choice, as well as comparing to the more physical Wang-Sheeley-Arge (WSA) and the Magnetohydrodynamic Algorithm outside a Sphere (MAS) models. We find that simultaneous optimization of PFSS models to all three metrics is not currently possible, implying a trade-off between the quality of representation of coronal holes and streamer belt topology. WSA and MAS results show the additional physics that they include address this by flattening the streamer belt while maintaining coronal hole sizes, with MAS also improving coronal hole representation relative to WSA. We conclude that this framework is highly useful for inter- and intra-model comparisons. Integral to the framework is the standardization of observables required of each model, evaluating different model aspects.

Keywords: Solar coronal holes, Solar physics, Astronomical models, Solar corona
Solar Wind Charge Exchange Soft X-Ray Emissions in the Magnetosphere during an Interplanetary Coronal Mass Ejection Compared to Its Driven Sheath. Soft X-ray emissions from solar wind charge exchange (SWCX) are applied in a recently developed approach to study the magnetosphere using panoramic soft X-ray imaging. This study represents the first attempt to distinguish magnetospheric SWCX emissions observed by XMM-Newton during the impact of an interplanetary coronal mass ejection (ICME) and its driven sheath on Earth. In addition, data from the Advanced Composition Explorer (ACE) were available during this same observational period, which is rare in previous studies. Results showed that SWCX emissions peaked during the ICME at approximately 2.3 times the mean of the observation period, although the solar wind flux decreased to a much lower level. A comparison of spectral results with ion data probed by ACE revealed that high ionization states in the ICME effectively enhanced line emission intensity for heavy ions (e.g., Ne, Mg, and Al). Thus, despite a low proton flux, elevated high-valence ion abundance in the ICME favors magnetospheric soft X-ray observations. Furthermore, the fitted X-ray flux of ion line emissions was consistent with elemental abundance ratios determined in situ by ACE, particularly for C5+, C6+, Ne9+, Mg11+, and Mg12+. This confirms the viability of spectral diagnosis of SWCX emissions as a new method for remotely analyzing high-state ion distributions in solar wind. A time-correlated or two-stage efficiency factor is further suggested to better estimate X-ray intensity during an ICME impact, which was ~1.7 times higher in the ICME than in the sheath.

Keywords: X-ray astronomy, Solar wind, Solar coronal mass ejections, Diffuse x-ray background, Solar-terrestrial interactions
A Speed Bump: SN 2021aefx Shows that Doppler Shift Alone Can Explain Early Excess Blue Flux in Some Type Ia Supernovae. We present early-time photometric and spectroscopic observations of the Type Ia supernova (SN Ia) 2021aefx. The early-time u-band light curve shows an excess flux when compared to normal SNe Ia. We suggest that the early excess blue flux may be due to a rapid change in spectral velocity in the first few days post explosion, produced by the emission of the Ca II H&amp;K feature passing from the u to the B bands on the timescale of a few days. This effect could be dominant for all SNe Ia that have broad absorption features and early-time velocities over 25,000 km s-1. It is likely to be one of the main causes of early excess u-band flux in SNe Ia that have early-time high velocities. This effect may also be dominant in the UV filters, as well as in places where the SN spectral energy distribution is quickly rising to longer wavelengths. The rapid change in velocity can only produce a monotonic change (in flux-space) in the u band. For objects that explode at lower velocities, and have a more structured shape in the early excess emission, there must also be an additional parameter producing the early-time diversity. More early-time observations, in particular early spectra, are required to determine how prominent this effect is within SNe Ia.

Keywords: Time domain astronomy, Type Ia supernovae, Supernovae
A New Constraint on the Nuclear Equation of State from Statistical Distributions of Compact Remnants of Supernovae. Understanding how matter behaves at the highest densities and temperatures is a major open problem in both nuclear physics and relativistic astrophysics. Our understanding of such behavior is often encapsulated in the so-called high-temperature nuclear equation of state (EOS), which influences compact binary mergers, core-collapse supernovae, and other phenomena. Our focus is on the type (either black hole or neutron star) and mass of the remnant of the core collapse of a massive star. For each six candidates of equations of state, we use a very large suite of spherically symmetric supernova models to generate a sample of synthetic populations of such remnants. We then compare these synthetic populations to the observed remnant population. Our study provides a novel constraint on the high-temperature nuclear EOS and describes which EOS candidates are more or less favored by an information-theoretic metric.

Keywords: Neutron stars, Computational astronomy, Core-collapse supernovae, Astrostatistics techniques, Stellar mass black holes, Nuclear astrophysics, Astrophysical black holes
Inferring the Intermediate-mass Black Hole Number Density from Gravitational-wave Lensing Statistics. The population properties of intermediate-mass black holes remain largely unknown, and understanding their distribution could provide a missing link in the formation of supermassive black holes and galaxies. Gravitational-wave observations can help fill in the gap from stellar mass black holes to supermassive black holes with masses between ~100-104 M ⊙. In our work, we propose a new method for examining lens populations through lensing statistics of gravitational waves, here focusing on inferring the number density of intermediate-mass black holes through hierarchical Bayesian inference. Simulating ~200 lensed gravitational-wave signals, we find that existing gravitational-wave observatories at their design sensitivity could either constrain the number density of 106 Mpc-3 within a factor of 10, or place an upper bound of ≲104 Mpc-3 if the true number density is 103 Mpc-3. More broadly, our method leaves room for incorporation of additional lens populations, providing a general framework for probing the population properties of lenses in the universe.

Keywords: Intermediate-mass black holes, Gravitational lensing, Gravitational waves, Hierarchical models
The Large Superfast Rotators Discovered by the Zwicky Transient Facility. Two high-cadence surveys aiming for rotation period measurements of asteroids have been conducted in 2019 January and October using the Zwicky Transient Facility. From the surveys, 25 large superfast rotators (SFRs) were discovered and they are all main-belt asteroids (MBAs), except for one Mars crosser. These large SFRs have a diameter ranging from 0.43 to 7.87 km and a rotation period between 0.48 and 1.95 hr. Considering their diameters and fast rotations, they cannot be explained by rubble-pile structure unless using extraordinary high bulk densities. Cohesion, if available, can conserve these large SFRs. The estimated cohesion for these large SFRs could be up to thousands of pascals, much higher than the currently estimated cohesion for asteroids and that generated by the regolith of Moon and Mars. Such high-level cohesion can be produced from fine-grain regolith, like clay. However, the availability of such fine-grain regolith for asteroids is still unknown. Although the possibility of these large SFRs being large monolithic objects cannot be ruled out, this scenario is very unlikely given that the timescale of disruptive impact for MBAs in a similar diameter range is 107-108 yr.

Keywords: Asteroids, Light curves, Asteroid rotation, Time domain astronomy, Time series analysis
The Young Stars in the Galactic Center. We present a large ~30″ × 30″ spectroscopic survey of the Galactic Center using the SINFONI IFU at the VLT. Combining observations of the last two decades we compile spectra of over 2800 stars. Using the Bracket-γ absorption lines, we identify 195 young stars, extending the list of known young stars by 79. In order to explore the angular momentum distribution of the young stars, we introduce an isotropic cluster prior. This prior reproduces an isotropic cluster in a mathematically exact way, which we test through numerical simulations. We calculate the posterior angular momentum space as a function of projected separation from Sgr A*. We find that the observed young star distribution is substantially different from an isotropic cluster. We identify the previously reported feature of the clockwise disk and find that its angular momentum changes as a function of separation from the black hole and thus confirm a warp of the clockwise disk (p ~ 99.2%). At large separations, we discover three prominent overdensities of the angular momentum. One overdensity has been reported previously, the counterclockwise disk. The other two are new. Determining the likely members of these structures, we find that as many as 75% of stars can be associated with one of these features. Stars belonging to the warped clockwise disk show a top-heavy K-band luminosity function, while stars belonging to the larger separation features do not. Our observations are in good agreement with the predictions of simulations of in situ star formation and argue for the common formation of these structures.

Keywords: Galactic center
Radioactively Powered Gamma-Ray Transient Associated with a Kilonova from Neutron Star Merger. The association of GW170817/GRB 170817A/AT2017gfo provides the first direct evidence for neutron star mergers as significant sources of r-process nucleosynthesis. A gamma-ray transient (GRT) would be powered by the radioactive decay of the freshly synthesized r-process elements. By analyzing the composition and gamma-ray opacity of the kilonova ejecta in detail, we calculate the lightcurve and spectrum of the GRT for a range of spherically symmetric merger ejecta models with mass M ej = 0.001 to ~0.05M ⊙ and expansion velocity v ej = 0.1c to ~0.4c. It is found that the peak of the GRT lightcurve depends on M ej and v ej as ${t}_{\mathrm{pk}}\approx 0.5\,\mathrm{days}\,{({M}_{\mathrm{ej}}/0.01{M}_{\odot })}^{1/2}{({v}_{\mathrm{ej}}/0.1c)}^{-1}$ and ${L}_{\mathrm{pk}}\approx 2.0\times {10}^{41}\,\mathrm{erg}\,{{\rm{s}}}^{-1}{({M}_{\mathrm{ej}}/0.01{M}_{\odot })}^{1/2}({v}_{\mathrm{ej}}/0.1c)$ . Most radiating photons are in the 100-3000 keV band and the spectrum peaks at about 800 keV for different nuclear physics inputs. The line features are blurred out by the Doppler broadening effect. Adopting the ejecta parameters reported in the literature, we examine the detection probability of the possible GRT associated with AT2017gfo. We show that the GRT cannot be convincingly detected with either current or proposed missions in the MeV band, such as ETCC and AMEGO. The low gamma-ray flux, together with the extremely low event rate at local universe, makes a discovery of GRTs a great challenge.

Keywords: Gamma-ray bursts, Explosive nucleosynthesis, Stellar mergers, R-process, Gamma-ray transient sources
Optical Light Curve of 4FGL J0935.3+0901: A Flaring Black Widow Candidate. I obtained time-series photometry of the compact binary candidate for the Fermi source 4FGL J0935.3+0901. Superposed on the 2.44 hr orbital modulation are day-to-day variations and frequent flaring as seen in several redback and black widow millisecond pulsars (MSPs). The short orbital period favors a black widow. While the modulation of ≤1 mag is smaller than that of most black widows, it could indicate a low orbital inclination. Although a published optical spectrum shows strong emission lines, the light curve evinces pulsar heating of the companion star rather than accretion-disk emission of a transitional MSP. Emission lines and flaring occur in the same objects, probably powered by shocks between the relativistic pulsar wind and a wind driven off the companion star. I also recovered the period in photometry from the Zwicky Transient Facility (ZTF). A phase-connected ephemeris derived from MDM Observatory and ZTF data spanning 4 yr yields a period of 0.10153276(36) days and an epoch for the ascending node of the putative pulsar.

Keywords: Gamma-ray sources, Millisecond pulsars
Kink Oscillation of a Flux Rope During a Failed Solar Eruption. We report a decaying kink oscillation of a flux rope during a confined eruptive flare, observed off the solar limb by the Solar Dynamics Observatory's Atmospheric Imaging Assembly (AIA), which lacked a detectable white-light coronal mass ejection. The erupting flux rope underwent kinking, rotation, and apparent leg-leg interaction during the event. The oscillations were observed simultaneously in multiple AIA channels at 304, 171, and 193 Å, indicating that multithermal plasma was entrained in the rope. After reaching the overlying loops in the active region, the flux rope exhibited large-amplitude, decaying kink oscillations with an apparent initial amplitude of 30 Mm, a period of about 16 minutes, and a decay time of about 17 minutes. We interpret these oscillations as a fundamental standing kink mode of the flux rope. The oscillation polarization has a clear vertical component, while the departure of the detected waveform from a sinusoidal signal suggests that the oscillation could be circularly or elliptically polarized. The estimated kink speed is 1080 km s-1, corresponding to an Alfvén speed of about 760 km s-1. This speed, together with the estimated electron density in the rope from our differential emission measure analysis, n  e  ≈ (1.5-2.0) × 109 cm-3, yields a magnetic-field strength of about 15 G. To the best of our knowledge, decaying kink oscillations of a flux rope with nonhorizontal polarization during a confined eruptive flare have not been reported before. These oscillations provide unique opportunities for indirect measurements of the magnetic-field strength in low-coronal flux ropes during failed eruptions.

Keywords: Solar magnetic reconnection, Solar active regions, Solar filaments, Solar coronal mass ejections, Solar x-ray flares, Solar coronal seismology
Dynamical Friction in Globular Cluster-rich Ultra-diffuse Galaxies: The Case of NGC5846-UDG1. Ultra-diffuse galaxies that contain a large sample of globular clusters (GCs) offer an opportunity to test the predictions of galactic dynamics theory. NGC5846-UDG1 is an excellent example, with a high-quality sample of dozens of GC candidates. We show that the observed distribution of GCs in NGC5846-UDG1 is suggestive of mass segregation induced by gravitational dynamical friction. We present simple analytic calculations, backed by a series of numerical simulations, that naturally explain the observed present-day pattern of GC masses and radial positions. Subject to some assumptions on the GC population at birth, the analysis supports the possibility that NGC5846-UDG1 resides in a massive dark matter halo. This is an example for the use of GC-rich systems as dynamical (in addition to kinematical) tracers of dark matter.

Keywords: Globular star clusters, Galaxy formation, Galaxy dynamics, Dwarf galaxies, HST photometry, Dynamical friction, Low surface brightness galaxies
Isotropization and Evolution of Energy-containing Eddies in Solar Wind Turbulence: Parker Solar Probe, Helios 1, ACE, WIND, and Voyager 1. We examine the radial evolution of correlation lengths perpendicular ( ${\lambda }_{C}^{\perp }$ ) and parallel ( ${\lambda }_{C}^{\parallel }$ ) to the magnetic-field direction, computed from solar wind magnetic-field data measured by Parker Solar Probe (PSP) during its first eight orbits, Helios 1, Advanced Composition Explorer (ACE), WIND, and Voyager 1 spacecraft. Correlation lengths are grouped by an interval's alignment angle; the angle between the magnetic-field and solar wind velocity vectors (ΘBV). Parallel and perpendicular angular channels correspond to angles 0° &lt; ΘBV &lt; 40° and 50° &lt; ΘBV &lt; 90°, respectively. We observe an anisotropy in the inner heliosphere within 0.40 au, with ${\lambda }_{C}^{\parallel }/{\lambda }_{C}^{\perp }\approx 0.75$ at 0.10 au. This anisotropy reduces with increasing heliocentric distance and the correlation lengths roughly isotropize within 1 au. Results from ACE and WIND support a reversal of the anisotropy, such that ${\lambda }_{C}^{\parallel }/{\lambda }_{C}^{\perp }\approx 1.29$ at 1 au. The ratio does not appear to change significantly beyond 1 au, although the small number of parallel intervals in the Voyager data set precludes unambiguous conclusions from being drawn. This study provides insights regarding the radial evolution of the large, most energetic interacting turbulent fluctuations in the heliosphere. We also emphasize the importance of tracking the changes in sampling direction in PSP measurements as the spacecraft approaches the Sun, when using these data to study the radial evolution of turbulence. This can prove to be vital in understanding the more complex dynamics of the solar wind in the inner heliosphere and can assist in improving related simulations.

Keywords: Interplanetary turbulence, Solar wind, Heliosphere, Two-point correlation function