adsabs/SciX_UAT_keywords huggingface dataset:
A Measurement of the Degree-scale CMB B-mode Angular Power Spectrum with POLARBEAR

We present a measurement of the B-mode polarization power spectrum of the cosmic microwave background (CMB) using data taken from 2014 July to 2016 December with the POLARBEAR experiment. The CMB power spectra are measured using observations at 150 GHz with an instantaneous array sensitivity of ${\mathrm{NET}}_{\mathrm{array}}=23\,\mu {\rm{K}}\sqrt{{\rm{s}}}$ on a 670 square degree patch of sky centered at (R.A., decl.) = (+0h12m0s, -59°18'). A continuously rotating half-wave plate is used to modulate polarization and to suppress low-frequency noise. We achieve 32 μK arcmin effective polarization map noise with a knee in sensitivity of ℓ = 90, where the inflationary gravitational-wave signal is expected to peak. The measured B-mode power spectrum is consistent with a ΛCDM lensing and single dust component foreground model over a range of multipoles 50 ≤ ℓ ≤ 600. The data disfavor zero ${C}_{{\ell }}^{\mathrm{BB}}$ at 2.2σ using this ℓ range of POLARBEAR data alone. We cross-correlate our data with Planck full mission 143, 217, and 353 GHz frequency maps and find the low-ℓ B-mode power in the combined data set to be consistent with thermal dust emission. We place an upper limit on the tensor-to-scalar ratio r < 0.90 at the 95% confidence level after marginalizing over foregrounds.

Keywords: observational cosmology; cosmic microwave background radiation; cosmic inflation; cosmology
Aerodynamic Roughness Height of Gravel-covered Plains in the Puna of Argentina

Plains covered by gravel-dominated desert pavement in the Puna of Argentina have an aerodynamic roughness height (or length) z 0 of ~1 cm, likely representing a skimming flow regime above the closely spaced gravel particles. Aerodynamic roughness height locally may transition from that of skimming flow over the gravels to a z 0 that includes the effects of obstacles considerably larger than those of the gravel particles alone. Among large (>60 cm tall) megaripples, z 0 is elevated beyond that of the gravels alone to values of 2-4 cm. These results represent an analog for an improved understanding of the aerodynamics of gravel-dominated desert pavement and megaripples documented by multiple rovers on Mars.

Keywords: earth (planet); surface processes; geological processes
Relative Velocities between 13CO Structures within 12CO Molecular Clouds

Velocity fields of molecular clouds (MCs) can provide crucial information on the merger and split between clouds, as well as their internal kinematics and maintenance, energy injection and redistribution, and even star formation within clouds. Using the CO spectral lines data from the Milky Way Imaging Scroll Painting survey, we measure the relative velocities along the line of sight (ΔV LOS) between 13CO structures within 12CO MCs. Emphasizing MCs with double and triple 13CO structures, we find that approximately 70% of ΔV LOS values are less than ∼1 km s‑1, and roughly 10% of values exceed 2 km s‑1, with a maximum of ∼5 km s‑1. Additionally, we compare ΔV LOS with the internal velocity dispersion of 13CO structures ( ${\sigma }_{{}^{13}\mathrm{CO},\mathrm{in}}$ ) and find that about 40% of samples in either double or triple regime display distinct velocity discontinuities, i.e., the relative velocities between 13CO structures are larger than the internal line widths of 13CO structures. Among these 40% samples in the triple regime, 33% exhibit signatures of combinations through the two-body motion, whereas the remaining 7% show features of configurations through the multiple-body motion. The ΔV LOS distributions for MCs with double and triple 13CO structures are similar, as well as their ΔV LOS/ ${\sigma }_{{}^{13}\mathrm{CO},\mathrm{in}}$ distributions. This suggests that relative motions of 13CO structures within MCs are random and independent of cloud complexities and scales.

Keywords: interstellar medium; interstellar molecules; molecular clouds
Search for X-Ray Quasiperiodicity of Six AGNs Using the Gaussian Process Method

The quasiperiodic oscillations (QPOs) found in active galactic nuclei (AGNs) are a very interesting observational phenomenon implying an unknown physical mechanism around supermassive black holes. Several AGNs have been found to have QPO phenomena in the X-ray energy band. Long-duration X-ray observations were collected and reduced for six AGNs with a suspected QPO. The Gaussian process model celerite was used to fit the light curves and to search for the quasiperiodicity behavior. The power spectral density and parameter posterior distributions of each light curve were calculated with the optimal model. Of the six AGNs, only RE J1034+396 was found to have a QPO of about 3600 s. The other five sources do not show QPO modulation behavior. We propose that a hot spot on the accretion disk is a possible physical mechanism resulting in this quasiperiodic behavior of AGNs.

Keywords: active galactic nuclei; supermassive black holes; time series analysis; x-ray active galactic nuclei
Investigating the Superorbital Modulations in 4U 1909 + 07, IGR J16418-4532, and IGR J16479-4514 with Swift XRT, BAT, and NuSTAR Observations

A puzzling variety of superorbital modulations has been discovered in several supergiant high mass X-ray binaries (sgHMXBs). To investigate the mechanisms driving these superorbital modulations, we have analyzed long-term Neil Gehrels Swift Observatory (Swift) Burst Alert Telescope (BAT) observations of three sgHMXBs: 4U 1909 + 07, IGR J16418-4532, and IGR J16479-4514, and constructed their dynamic power spectra and superorbital intensity profiles. These Swift BAT observations are complemented by pointed Swift X-ray Telescope (XRT) and Nuclear Spectroscopic Telescope Array (NuSTAR) observations performed near the predicted maximum and minimum phase of a single superorbital cycle for each of these sources. The BAT dynamic power spectra show changes in the strength of the superorbital modulation on timescales of years, with either the peak at the fundamental frequency and/or the second harmonic present at different times for all three sources. The pointed Swift XRT and NuSTAR observations show no significant differences between the pulse profiles and spectral parameters at the superorbital maximum and minimum phase. This is likely due to the fact the superorbital modulation had weakened significantly during the times when the NuSTAR observations were carried out for all three sources. The results from the Swift XRT, BAT, and NuSTAR analysis indicate the possible presence of multiple corotating interaction regions (CIRs) in the stellar winds of the supergiant stars, although a structured stellar wind from the supergiant star due to tidal oscillations cannot be ruled out.

Keywords: high mass x-ray binary stars; astronomy data analysis; stellar winds
SNIascore: Deep-learning Classification of Low-resolution Supernova Spectra

We present SNIascore, a deep-learning-based method for spectroscopic classification of thermonuclear supernovae (SNe Ia) based on very low-resolution (R ~ 100) data. The goal of SNIascore is the fully automated classification of SNe Ia with a very low false-positive rate (FPR) so that human intervention can be greatly reduced in large-scale SN classification efforts, such as that undertaken by the public Zwicky Transient Facility (ZTF) Bright Transient Survey (BTS). We utilize a recurrent neural network architecture with a combination of bidirectional long short-term memory and gated recurrent unit layers. SNIascore achieves a <0.6% FPR while classifying up to 90% of the low-resolution SN Ia spectra obtained by the BTS. SNIascore simultaneously performs binary classification and predicts the redshifts of secure SNe Ia via regression (with a typical uncertainty of <0.005 in the range from z = 0.01 to z = 0.12). For the magnitude-limited ZTF BTS survey (≈70% SNe Ia), deploying SNIascore reduces the amount of spectra in need of human classification or confirmation by ≈60%. Furthermore, SNIascore allows SN Ia classifications to be automatically announced in real time to the public immediately following a finished observation during the night.

Keywords: supernovae; type ia supernovae; neural networks; classification; surveys
cuHARM: A New GPU-accelerated GRMHD Code and Its Application to ADAF Disks

We introduce a new GPU-accelerated general relativistic magnetohydrodynamic code based on HARM, which we call cuHARM. The code is written in CUDA-C and uses OpenMP to parallelize multi-GPU setups. Our code allows us to run high-resolution simulations of accretion disks and the formation and structure of jets without a need for multinode supercomputer infrastructure. A 2563 simulation is well within the reach of an Nvidia DGX-V100 server, with the computation being about 10 times faster than if only the CPU is used. We use this code to examine several disk structures all in the SANE state. We find that (i) increasing the magnetic field in the SANE state does not affect the mass accretion rate; (ii) simultaneously increasing the disk size and the magnetic field, while keeping the ratio of energies fixed, leads to the destruction of the jet once the magnetic flux through the horizon decreases below a certain limit (this demonstrates that the existence of a jet is a function of the initial mass distribution, and not of the initial intensity of the magnetic field, since the magnetorotational instability dictates the evolution of the magnetic field); and (iii) the structure of the jet is a weak function of the adiabatic index of the gas, with relativistic gas tending to have a wider jet.

Keywords: accretion; magnetohydrodynamical simulations; magnetohydrodynamics; black hole physics; computational methods; gpu computing
ALMA Observations of NGC 6334S. I. Forming Massive Stars and Clusters in Subsonic and Transonic Filamentary Clouds

We present Atacama Large Millimeter/submillimeter Array (ALMA) and Karl G. Jansky Very Large Array (JVLA) observations of the massive infrared dark cloud NGC 6334S (also known as IRDC G350.56+0.44), located at the southwestern end of the NGC 6334 molecular cloud complex. The H13CO+ and NH2D lines covered by the ALMA observations at a ∼3″ angular resolution (∼0.02 pc) reveal that the spatially unresolved nonthermal motions are predominantly subsonic and transonic, a condition analogous to that found in low-mass star-forming molecular clouds. The observed supersonic nonthermal velocity dispersions in massive star-forming regions, often reported in the literature, might be significantly biased by poor spatial resolutions that broaden the observed line widths owing to unresolved motions within the telescope beam. Our 3 mm continuum image resolves 49 dense cores, whose masses range from 0.17 to 14 M⊙. The majority of them are resolved with multiple velocity components. Our analyses of these gas velocity components find an anticorrelation between the gas mass and the virial parameter. This implies that the more massive structures tend to be more gravitationally unstable. Finally, we find that the external pressure in the NGC 6334S cloud is important in confining these dense structures and may play a role in the formation of dense cores and, subsequently, the embedded young stars.

Keywords: early-type stars; star formation; massive stars; protoclusters; protostars; radio spectroscopy; radio continuum emission; radio interferometers; submillimeter astronomy; molecular spectroscopy
Deconstructing Photospheric Spectral Lines in Solar and Stellar Flares

During solar flares, spectral lines formed in the photosphere have been shown to exhibit changes to their profiles despite the challenges of energy transfer to these depths. Recent work has shown that deep-forming spectral lines are subject to significant contributions from regions above the photosphere throughout the flaring period, resulting in a composite emergent intensity profile from multiple layers of the atmosphere. We employ radiative–hydrodynamic and radiative transfer calculations to simulate the response of the solar/stellar atmosphere to electron beam heating and synthesize spectral lines of Fe I to investigate the line-of-sight velocity fields information available from Doppler shifts of the emergent intensity profile. By utilizing the contribution function to deconstruct the line profile shape into its constituent sources, we show that variations in the line profiles are primarily caused by changes in the chromosphere. Up-flows in this region were found to create blueshifts or false redshifts in the line core dependent on the relative contribution of the chromosphere compared to the photosphere. In extreme solar and stellar flare scenarios featuring explosive chromospheric condensations, redshifted transient components can dominate the temporal evolution of the profile shape, requiring a tertiary component consideration to fully characterize. We conclude that deep-forming lines require a multicomponent understanding and treatment, with different regions of the spectral line being useful for probing individual regions of the atmosphere's velocity flows.

Keywords: solar flares; stellar flares; solar photosphere; stellar photospheres; radiative transfer simulations; solar activity; stellar activity
Gaia RR Lyrae Stars in Nearby Ultra-faint Dwarf Satellite Galaxies

We search for RR Lyrae stars (RRLs) in 27 nearby (<100 kpc) ultra-faint dwarf satellite galaxies using the Gaia DR2 catalog of RRLs. Based on proper motions, magnitudes, and location on the sky, we associate 47 Gaia RRLs with 14 different satellites. Distances based on RRLs are provided for those galaxies. We have identified RRLs for the first time in the Tucana II dwarf galaxy, and find additional members in Ursa Major II, Coma Berenices, Hydrus I, Bootes I, and Bootes III. In addition we have identified candidate extra-tidal RRLs in six galaxies, which suggests they may be undergoing tidal disruption. We found 10 galaxies have no RRLs either in Gaia or in the literature. However, given the known completeness of Gaia DR2 we cannot conclude these galaxies indeed lack variable stars of this type.

Keywords: dwarf galaxies; rr lyrae variable stars; galaxy distances; distance indicators; local group
Target Prioritization and Observing Strategies for the NEID Earth Twin Survey

NEID is a high-resolution optical spectrograph on the WIYN 3.5 m telescope at Kitt Peak National Observatory and will soon join the new generation of extreme precision radial velocity instruments in operation around the world. We plan to use the instrument to conduct the NEID Earth Twin Survey (NETS) over the course of the next 5 years, collecting hundreds of observations of some of the nearest and brightest stars in an effort to probe the regime of Earth-mass exoplanets. Even if we take advantage of the extreme instrumental precision conferred by NEID, it will be difficult to disentangle the weak (∼10 cm s-1) signals induced by such low-mass, long-period exoplanets from stellar noise for all but the quietest host stars. In this work, we present a set of quantitative selection metrics which we use to identify an initial NETS target list consisting of stars conducive to the detection of exoplanets in the regime of interest. We also outline a set of observing strategies with which we aim to mitigate uncertainty contributions from intrinsic stellar variability and other sources of noise.

Keywords: exoplanets; radial velocity; exoplanet detection methods; stellar properties; surveys
ACCESS and LRG-BEASTS: A Precise New Optical Transmission Spectrum of the Ultrahot Jupiter WASP-103b

We present a new ground-based optical transmission spectrum of the ultrahot Jupiter WASP-103b ( ${T}_{\mathrm{eq}}=2484$ K). Our transmission spectrum is the result of combining five new transits from the ACCESS survey and two new transits from the LRG-BEASTS survey with a reanalysis of three archival Gemini/GMOS transits and one VLT/FORS2 transit. Our combined 11-transit transmission spectrum covers a wavelength range of 3900-9450 Å with a median uncertainty in the transit depth of 148 parts per million, which is less than one atmospheric scale height of the planet. In our retrieval analysis of WASP-103b's combined optical and infrared transmission spectrum, we find strong evidence for unocculted bright regions (4.3σ) and weak evidence for H2O ( $1.9\sigma $ ), HCN ( $1.7\sigma $ ), and TiO ( $2.1\sigma $ ), which could be responsible for WASP-103b's observed temperature inversion. Our optical transmission spectrum shows significant structure that is in excellent agreement with the extensively studied ultrahot Jupiter WASP-121b, for which the presence of VO has been inferred. For WASP-103b, we find that VO can only provide a reasonable fit to the data if its abundance is implausibly high and we do not account for stellar activity. Our results highlight the precision that can be achieved by ground-based observations and the impacts that stellar activity from F-type stars can have on the interpretation of exoplanet transmission spectra.

Keywords: exoplanet astronomy; exoplanet atmospheres; exoplanet atmospheric composition; extrasolar gaseous giant planets; hot jupiters; planet hosting stars
Comparison of Observed Galaxy Properties with Semianalytic Model Predictions Using Machine Learning

With current and upcoming experiments such as the Wide Field Infrared Survey Telescope, Euclid, and Large Synoptic Survey Telescope, we can observe up to billions of galaxies. While such surveys cannot obtain spectra for all observed galaxies, they produce galaxy magnitudes in color filters. This data set behaves like a high-dimensional nonlinear surface, an excellent target for machine learning. In this work, we use a lightcone of semianalytic galaxies tuned to match Cosmic Assembly Near-infrared Deep Legacy Survey (CANDELS) observations from Lu et al. to train a set of neural networks on a set of galaxy physical properties. We add realistic photometric noise and use trained neural networks to predict stellar masses and average star formation rates (SFRs) on real CANDELS galaxies, comparing our predictions to SED-fitting results. On semianalytic galaxies, we are nearly competitive with template-fitting methods, with biases of 0.01 dex for stellar mass, 0.09 dex for SFR, and 0.04 dex for metallicity. For the observed CANDELS data, our results are consistent with template fits on the same data at 0.15 dex bias in ${M}_{\mathrm{star}}$ and 0.61 dex bias in the SFR. Some of the bias is driven by SED-fitting limitations, rather than limitations on the training set, and some is intrinsic to the neural network method. Further errors are likely caused by differences in noise properties between the semianalytic catalogs and data. Our results show that galaxy physical properties can in principle be measured with neural networks at a competitive degree of accuracy and precision to template-fitting methods.

Keywords: galaxy counts; galaxy physics; computational methods
An ATA Search for a Repetition of the Wow Signal

The Allen Telescope Array was used to search for signals with characteristics similar to the "Wow" signal, the best candidate for an extraterrestrial radio signal found during Ohio State University's (OSU's) seven-year 21 cm 10-kHz channel sky survey for signals possibly due to extraterrestrial intelligence. While previous follow-up searches have reported null results, our observations covered a 5 deg2 field of view that extends well beyond the locus of all consistent directions of arrival (DOAs) of the original signal, and covered a 10 MHz bandwidth four times wider than the widest prior follow-up observations, using 12.8 kHz channels approximating OSU's 10 kHz resolution. Approximately 100 hours of data were accumulated, considerably more time than any previous follow-up campaigns. We used interferometric imaging with an angular resolution of approximately 0°07 and automated feature-finding to search for point-like features mimicking a Wow repetition, obtaining single-channel sensitivity of ∼1.2 Jy for one minute averages. This allows identification of the DOA of a very brief repetition, with strong discrimination from radio interference, and eliminates the usual constraint that the signal must persist for long periods of time (around one hour) before the true DOA can be verified (because interfering signals from the horizon sometimes masquerade as coming from the look direction). No point-like features significantly exceeding the noise were found inside the full width at half maximum of the OSU fields of view, although one 26σ point-like feature was detected during one 10 second integration about 1/3° away.

Keywords: astrobiology
Taxonomic Analysis of Asteroids with Artificial Neural Networks

We study the surface composition of asteroids with visible and/or infrared spectroscopy. For example, asteroid taxonomy is based on the spectral features or multiple color indices in visible and near-infrared wavelengths. The composition of asteroids gives key information to understand their origin and evolution. However, we lack compositional information for faint asteroids due to the limits of ground-based observational instruments. In the near future, the Chinese Space Survey Telescope (CSST) will provide multiple colors and spectroscopic data for asteroids of apparent magnitude brighter than 25 and 23 mag, respectively. With the aim of analyzing the CSST spectroscopic data, we applied an algorithm using artificial neural networks (ANNs) to establish a preliminary classification model for asteroid taxonomy according to the design of the survey module of CSST. Using the SMASS II spectra and the Bus-Binzel taxonomic system, our ANN classification tool composed of five individual ANNs is constructed, and the accuracy of this classification system is higher than 92%. As the first application of our ANN tool, 64 spectra of 42 asteroids obtained by us in 2006 and 2007 with the 2.16 m telescope in the Xinglong station (Observatory Code 327) of National Astronomical Observatory of China are analyzed. The predicted labels of these spectra using our ANN tool are found to be reasonable when compared to their known taxonomic labels. Considering its accuracy and stability, our ANN tool can be applied to analyze CSST asteroid spectra in the future.

Keywords: asteroids; main belt asteroids