Sazuna/UAT_keywords huggingface dataset:
Dispersion Characteristics of the Multi-mode Fiber-fed VIPA Spectrograph. A high-resolution ( ${ \mathcal R }\gt {10}^{5}$ ), multi-mode fiber-fed spectrograph on large telescopes with a reasonable size is desirable in astronomy. In this work, the dispersion characteristics of a multi-mode fiber-fed Virtually Imaged Phased Array (VIPA) spectrograph are studied theoretically and experimentally. A VIPA spectrograph, fed by multi-mode optical fibers with the operating wavelength at 750 ~ 770 nm, is designed and built in our laboratory. After calibration with a homemade Yb:fiber ring laser frequency comb (with a repetition frequency of 808 MHz), the measured spectral resolution fed by multi-mode fibers with core diameters $\varnothing =10$ , 25, 50, and 105 μm is comparable with that of the single-mode fiber, i.e., ${ \mathcal R }=7.62\times {10}^{5}\sim 8.97\times {10}^{5}$ , with equivalent transmission efficiencies. This verifies experimentally that the spectral resolution is much less affected by the core diameters of the input fibers when compared with that of échelle spectrographs. It is also found that the diffraction envelope of the VIPA spectrograph relies on the coherence of light sources and the width of the point-spread function is inversely proportional to the spatial position on the detector. Since the VIPA spectrograph has no imaging process in the main dispersion direction, the spectral resolution is insensitive to the width of the input slit or the fiber diameter. This makes the VIPA spectrograph a promising instrument to attain an ultra-high spectral resolution ( ${ \mathcal R }\gt 3\times {10}^{5}$ ) on very large telescopes.

Keywords: High resolution spectroscopy, Astronomical techniques, Astronomical instrumentation, Astronomical methods
Faint but Not Forgotten. I. First Results from a Search for Astrospheres around AGB Stars in the Far-ultraviolet. Using the GALEX archive, we have discovered extended structures around ten asymptotic giant branch (AGB) stars (out of a total 92 searched) emitting in the far-ultraviolet (FUV) band. In all but one, we find the typical morphology expected for a spherical wind moving relative to, and interacting with, the interstellar medium (ISM) to produce an astrosphere. The exception is V Hya whose mass ejection is known to be highly aspherical, where we find evidence of its large parabolic outflows interacting with the ISM, and its collimated, extreme velocity outflows interacting with the circumstellar medium. For eight objects with relatively large proper motions, we find (as expected) that the termination-shock region lies in a hemisphere that contains the proper motion vector. Radial intensity cuts for each source have been used to locate the termination shock and the astropause's outer edge. In a few objects, the cuts also reveal faint emission just outside the astropause that likely arises in shocked ISM material. We have used these data, together with published mass-loss rates and wind expansion velocities, to determine the total mass lost and duration for each source-we find that the duration of and total mass in the shocked wind are significantly larger than their corresponding values for the unshocked wind. The combination of FUV and far-IR data on AGB astrospheres provides a unique database for theoretical studies (numerical simulations) of wind-ISM interactions. We show that a Cyclical Spatial Heterodyne Spectrometer on a small space-based telescope can provide high-resolution spectra of astrospheres to confirm the emission mechanism.

Keywords: Astrospheres, Circumstellar envelopes, Stellar bow shocks, Stellar mass loss, Ultraviolet astronomy, Asymptotic giant branch stars, Stellar winds
Detection of Rubidium and Samarium in the Atmosphere of the Ultrahot Jupiter MASCARA-4b. Ultrahot Jupiters (UHJs) possess the most extreme environments among various types of exoplanets, making them ideal laboratories to study the chemical composition and kinetics properties of exoplanet atmosphere with high-resolution spectroscopy. It has the advantage of resolving the tiny Doppler shift and weak signal from exoplanet atmosphere and has helped to detect dozens of heavy elements in UHJs including KELT-9b, WASP-76b, and WASP-121b. MASCARA-4b is a 2.8 days UHJ with an equilibrium temperature of ~2250 K, which is expected to contain heavy elements detectable with the Very Large Telescope (VLT). In this letter, we present a survey of atoms/ions in the atmosphere of the MASCARA-4b, using the two VLT/ESPRESSO transits data. Cross-correlation analyses are performed on the obtained transmission spectra at each exposure with the template spectra generated by petitRADTRANS for atoms/ions from element Li to U. We confirm the previous detection of Mg, Ca, Cr, and Fe, and report the detection of Rb, Sm, Ti+, and Ba+ with peak signal-to-noise ratios (S/Ns) &gt; 5. We report a tentative detection of Sc+, with peak S/Ns ~ 6 but deviating from the estimated position. The most interesting discovery is the first-time detection of elements Rb and Sm in an exoplanet. Rb is an alkaline element like Na and K, while Sm is the first lanthanide series element and is by far the heaviest one detected in exoplanets. Detailed modeling and acquiring more data are required to yield abundance ratios of the heavy elements and to understand better the common presence of them in UHJ's atmospheres.

Keywords: High resolution spectroscopy, Exoplanet atmospheric composition , Exoplanet atmospheres
Comprehensive Study of the Chemical Composition and Spatial Outgassing Behavior of Hyperactive Comet 46P/Wirtanen Using Near-IR Spectroscopy during its Historic 2018 Apparition. We present a comprehensive analysis of the chemical composition of the Jupiter-family comet and potential spacecraft target 46P/Wirtanen, in the near-IR wavelength range. We used iSHELL at the NASA Infrared Telescope Facility to observe the comet on 11 pre-, near-, and postperihelion dates in 2018 December and 2019 January and February during its historic apparition. We report rotational temperatures, production rates, and mixing ratios with respect to H2O and C2H6 or 3σ upper limits of the primary volatiles H2O, HCN, CH4, C2H6, CH3OH, H2CO, NH3, CO, C2H2, and HC3N. We also discuss the spatial outgassing of the primary volatiles, to understand their sources and the spatial associations between them. The spatial profiles of H2O in 46P/Wirtanen suggest the presence of extended H2O outgassing sources in the coma, similar to the EPOXI target comet 103P/Hartley 2. 46P/Wirtanen is among the few known hyperactive comets, and we note that its composition and outgassing behavior are similar to those of other hyperactive comets in many ways. We note that the analyzed parent volatiles showed different variations (relative mixing ratios) during the apparition. We compared the chemical composition of 46P/Wirtanen with the mean abundances in Jupiter-family comets and the comet population as measured with ground-based near-IR facilities to date. The molecular abundances in 46P/Wirtanen suggest that although they were changing, the variations were small compared to the range in the comet population, with CH3OH showing notably more variation as compared to the other molecules.

Keywords: Comae, Short period comets, Molecular spectroscopy, Comets, Comet volatiles , Near infrared astronomy
Long-term 4.6 μm Variability in Brown Dwarfs and a New Technique for Identifying Brown Dwarf Binary Candidates. Using a sample of 361 nearby brown dwarfs, we have searched for 4.6 μm variability, indicative of large-scale rotational modulations or large-scale, long-term changes on timescales of over 10 yr. Our findings show no statistically significant variability in Spitzer's Infrared Array Camera (IRAC) channel 2 (ch2) or Wide-field Infrared Survey Explorer W2 photometry. For Spitzer the ch2 1σ limits are ~8 mmag for objects at 11.5 mag and ~22 mmag for objects at 16 mag. This corresponds to no variability above 4.5% at 11.5 mag and 12.5% at 16 mag. We conclude that highly variable brown dwarfs, at least two previously published examples of which have been shown to have 4.6 μm variability above 80 mmag, are very rare. While analyzing the data, we also developed a new technique for identifying brown dwarf binary candidates in Spitzer data. We find that known binaries have IRAC ch2 point response function (PRF) flux measurements that are consistently dimmer than aperture flux measurements. We have identified 59 objects that exhibit such PRF versus aperture flux differences and are thus excellent binary brown dwarf candidates.

Keywords: Brown dwarfs, Binary stars, L subdwarfs, Low mass stars, Atmospheric variability
Observation Strategy Optimization for Distributed Telescope Arrays with Deep Reinforcement Learning. Time-domain astronomy is an active research area now, which requires frequent observations of the whole sky to capture celestial objects with temporal variations. In the optical band, several telescopes in different locations could form a distributed telescope array to capture images of celestial objects continuously. However, there are millions of celestial objects to observe each night, and only limited telescopes could be used for observation. Besides, the observation capacity of these telescopes would be affected by different effects, such as the sky background or the seeing condition. It would be necessary to develop an algorithm to optimize the observation strategy of telescope arrays according to scientific requirements. In this paper, we propose a novel framework that includes a digital simulation environment and a deep reinforcement learning algorithm to optimize observation strategy of telescope arrays. Our framework could obtain effective observation strategies given predefined observation requirements and observation environment information. To test the performance of our algorithm, we simulate a scenario that uses distributed telescope arrays to observe space debris. Results show that our algorithm could obtain better results in both discovery and tracking of space debris. The framework proposed in this paper could be used as an effective strategy optimization framework for distributed telescope arrays, such as the Sitian project or the TIDO project.

Keywords: Optical observation, Optical telescopes, Astronomical simulations, Neural networks
A High-Eccentricity Warm Jupiter Orbiting TOI-4127. We report the discovery of TOI-4127 b, which is a transiting, Jupiter-sized exoplanet on a long-period ( $P={56.39879}_{-0.00010}^{+0.00010}$ days) and a high-eccentricity orbit around a late F-type dwarf star. This warm Jupiter was first detected and identified as a promising candidate from a search for single-transit signals in TESS Sector 20 data, and was later characterized as a planet following two subsequent transits (TESS Sectors 26 and 53) and follow-up ground-based RV observations with the NEID and SOPHIE spectrographs. We jointly fit the transit and RV data to constrain the physical ( ${R}_{p}={1.096}_{-0.032}^{+0.039}{R}_{{\rm{J}}}$ , ${M}_{p}={2.30}_{-0.11}^{+0.11}{M}_{{\rm{J}}}$ ) and orbital parameters of the exoplanet. Given its high orbital eccentricity ( $e={0.7471}_{-0.0086}^{+0.0078}$ ), TOI-4127 b is a compelling candidate for studies of warm Jupiter populations and of hot Jupiter formation pathways. We show that the present periastron separation of TOI-4127 b is too large for high-eccentricity tidal migration to circularize its orbit, and that TOI-4127 b is unlikely to be a hot Jupiter progenitor unless it is undergoing angular momentum exchange with an undetected outer companion. Although we find no evidence for an external companion, the available observational data are insufficient to rule out the presence of a perturber that can excite eccentricity oscillations and facilitate tidal migration.

Keywords: Exoplanet dynamics, Elliptical orbits, Exoplanet astronomy, Radial velocity, Transit photometry
Hyades Member K2-136c: The Smallest Planet in an Open Cluster with a Precisely Measured Mass. K2-136 is a late-K dwarf (0.742 ± 0.039 M ☉) in the Hyades open cluster with three known, transiting planets and an age of 650 ± 70 Myr. Analyzing K2 photometry, we found that planets K2-136b, c, and d have periods of 8.0, 17.3, and 25.6 days and radii of 1.014 ± 0.050 R ⊕, 3.00 ± 0.13 R ⊕, and 1.565 ± 0.077 R ⊕, respectively. We collected 93 radial velocity (RV) measurements with the High-Accuracy Radial-velocity Planet Searcher for the Northern hemisphere (HARPS-N) spectrograph (Telescopio Nazionale Galileo) and 22 RVs with the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) spectrograph (Very Large Telescope). Analyzing HARPS-N and ESPRESSO data jointly, we found that K2-136c induced a semi-amplitude of 5.49 ± 0.53 m s-1, corresponding to a mass of 18.1 ± 1.9 M ⊕. We also placed 95% upper mass limits on K2-136b and d of 4.3 and 3.0 M ⊕, respectively. Further, we analyzed Hubble Space Telescope and XMM-Newton observations to establish the planetary high-energy environment and investigate possible atmospheric loss. K2-136c is now the smallest planet to have a measured mass in an open cluster and one of the youngest planets ever with a mass measurement. K2-136c has ~75% the radius of Neptune but is similar in mass, yielding a density of ${3.69}_{-0.56}^{+0.67}$ g cm-3 (~2-3 times denser than Neptune). Mass estimates for K2-136b (and possibly d) may be feasible with more RV observations, and insights into all three planets' atmospheres through transmission spectroscopy would be challenging but potentially fruitful. This research and future mass measurements of young planets are critical for investigating the compositions and characteristics of small exoplanets at very early stages of their lives and providing insights into how exoplanets evolve with time.

Keywords: Astronomy data modeling, Transits, Exoplanets, Radial velocity, Exoplanet systems, Exoplanet evolution, Extrasolar gaseous planets, Exoplanet detection methods, Exoplanet atmospheres
Transit Depth Variations Reveal TOI-216 b to be a Super-puff. The planets of the TOI-216 system have been previously observed to exhibit large transit-timing variations, which enabled precise mass characterization of both transiting planets. In the first year of TESS observations, TOI-216 b exhibited grazing transits, precluding a measurement of its radius. In new observations, we demonstrate the orbit of the planet has precessed and it is now fully transiting, so we can accurately measure its radius. TOI-216 b is a puffy Neptune-mass planet, with a much larger radius that is now well constrained to ${7.84}_{-0.19}^{+0.21}$ R ⊕ and a density of 0.201 ± 0.017 g cm-3. We numerically integrate the system across the TESS observations to update and refine the masses and orbits of both planets, finding the uncertainty in the masses are now dominated by uncertainties in the stellar parameters. TOI-216 b represents a growing class of super-puff planets in orbital resonances and with a companion in a nearly circular orbit, suggesting the early evolution of these planets is driven by smooth disk migration.

Keywords: Transit photometry, Transit duration variation method, Transit timing variation method, Exoplanets
SKYSURF-4: Panchromatic Hubble Space Telescope All-Sky Surface-brightness Measurement Methods and Results. The diffuse, unresolved sky provides most of the photons that the Hubble Space Telescope (HST) receives, yet remains poorly understood. The HST Archival Legacy program SKYSURF aims to measure the 0.2-1.6 μm sky surface brightness (sky-SB) from over 140,000 HST images. We describe a sky-SB measurement algorithm designed for SKYSURF that is able to recover the input sky-SB from simulated images to within 1% uncertainty. We present our sky-SB measurements estimated using this algorithm on the entire SKYSURF database. Comparing our sky-SB spectral energy distribution (SED) to measurements from the literature shows general agreements. Our SKYSURF SED also reveals a possible dependence on the Sun angle, indicating either nonisotropic scattering of solar photons off interplanetary dust or an additional component to zodiacal light. Finally, we update the diffuse light limits in the near-IR based on the methods from Carleton et al., with values of 0.009 MJy sr-1 (22 nW m-2 sr-1) at 1.25 μm, 0.015 MJy sr-1 (32 nW m-2 sr-1) at 1.4 μm, and 0.013 MJy sr-1 (25 nW m-2 sr-1) at 1.6 μm. These estimates provide the most stringent all-sky constraints to date in this wavelength range. SKYSURF sky-SB measurements are made public on the official SKYSURF website and will be used to constrain diffuse light in future papers.

Keywords: Optical astronomy, Hubble Space Telescope, Sky brightness, Zodiacal cloud, Cosmic background radiation
The Infrared Colors of 51 Eridani b: Micrometeoroid Dust or Chemical Disequilibrium?. We reanalyze the near-infrared spectra of the young extrasolar giant planet 51 Eridani b, which was originally presented in Macintosh et al. and Rajan et al. using modern atmospheric models, including a self-consistent treatment of disequilibrium chemistry due to turbulent vertical mixing. In addition, we investigate the possibility that significant opacity from micrometeors or other impactors in the planet's atmosphere may be responsible for shaping the observed spectral energy distribution (SED). We find that disequilibrium chemistry is useful for describing the mid-infrared colors of the planet's spectra, especially in regard to photometric data at the M band around 4.5 μm, which is the result of superequilibrium abundances of carbon monoxide, while the micrometeors are unlikely to play a pivotal role in shaping the SED. The best-fitting, micrometeoroid dust-free, disequilibrium chemistry, patchy cloud model has the following parameters: effective temperature T eff = 681 K with clouds (or without clouds, i.e., the grid temperature T grid = 900 K), surface gravity g = 1000 m s-2, sedimentation efficiency f sed = 10, vertical eddy diffusion coefficient K zz = 103 cm2 s-1, cloud hole fraction f hole = 0.2, and planet radius R planet = 1.0 R Jup.

Keywords: Exoplanet atmospheres, Direct imaging, Spectroscopy, Micrometeoroids
Contamination in TESS Light Curves: The Case of the Fast Yellow Pulsating Supergiants. Given its large plate scale of 21″ pixel-1, analyses of data from the Transiting Exoplanet Survey Satellite (TESS) space telescope must be wary of source confusion from blended light curves, which creates the potential to attribute observed photometric variability to the wrong astrophysical source. We explore the impact of light curve contamination on the detection of fast yellow pulsating supergiant (FYPS) stars as a case study to demonstrate the importance of confirming the source of detected signals in the TESS pixel data. While some of the FYPS signals have already been attributed to contamination from nearby eclipsing binaries, others are suggested to be intrinsic to the supergiant stars. In this work, we carry out a detailed analysis of the TESS pixel data to fit the source locations of the dominant signals reported for 17 FYPS stars with the Python package TESS_localize. We are able to reproduce the detections of these signals for 14 of these sources, obtaining consistent source locations for four. Three of these originate from contaminants, while the signal reported for BZ Tuc is likely a spurious frequency introduced to the light curve of this 127 day Cepheid by the data processing pipeline. Other signals are not significant enough to be localized with our methods, or have long periods that are difficult to analyze given other TESS systematics. Since no localizable signals hold up as intrinsic pulsation frequencies of the supergiant targets, we argue that unambiguous detection of pulsational variability should be obtained before FYPS are considered a new class of pulsator.

Keywords: CCD photometry, Light curve classification , Light curves, Variable stars, Photometry, Time series analysis
H I 21 cm Extended Structures to the Northeast and Southwest of NGC 5595: VLA Observations of the Disk Galaxy Pair NGC 5595 and NGC 5597. We report VLA B-configuration observations of the H I 21 cm line on the close disk galaxy pair NGC 5595 and NGC 5597. At the angular resolution of the observations, ~7.″1 × 4.″2, while most of the H I 21 cm in NGC 5595 and NGC 5597 has the same extent as the optical disk, we have detected for the first time extended structures (streamers) to the northeast (NE) and southwest (SW) of NGC 5595 with no counterparts in blue, red optical (continuum), 20 cm radio continuum, or Hα spectral line emission. One structure is extended by ~45″ to the NE with blueshifted velocities, and the other is extended by ~20″ to the SW with redshifted velocities with respect to the systemic velocity. No H I 21 cm emission is detected from the innermost central (nuclear) regions of either galaxy. Lower angular resolution H I 21 cm imaging indicates the nonexistence of any intergalactic hydrogen atomic H I 21 cm gas as tails or bridges between the two galaxies. Our new 20 cm radio continuum emission image of NGC 5597 shows a strong unresolved elongated structure in the central region, in the NE-SW direction, very similar to the spatial location of the innermost Hα spectral line emission. There is no 20 cm continuum emission from its northern spiral arm. In NGC 5595, the 20 cm radio continuum image shows no continuum emission from the NE or SW extended structures with H I 21 cm emission.

Keywords: Galaxy dynamics, Galaxy interactions, Galaxy tides, Galaxy kinematics, Galaxy rotation curves
A Measurement of the Kuiper Belt's Mean Plane From Objects Classified By Machine Learning. Mean plane measurements of the Kuiper Belt from observational data are of interest for their potential to test dynamical models of the solar system. Recent measurements have yielded inconsistent results. Here we report a measurement of the Kuiper Belt's mean plane with a sample size more than twice as large as in previous measurements. The sample of interest is the nonresonant Kuiper Belt objects, which we identify by using machine learning on the observed Kuiper Belt population whose orbits are well determined. We estimate the measurement error with a Monte Carlo procedure. We find that the overall mean plane of the nonresonant Kuiper Belt (semimajor axis range of 35-150 au) and also that of the classical Kuiper Belt (semimajor axis range of 42-48 au) are both close to (within ~0.°7) but distinguishable from the invariable plane of the solar system to greater than 99.7% confidence. When binning the sample into smaller semimajor axis bins, we find the measured mean plane is mostly consistent with both the invariable plane and the theoretically expected Laplace surface forced by the known planets. Statistically significant discrepancies are found only in the semimajor axis ranges 40.3-42 au and 45-50 au; these ranges are in proximity to the ν 8 secular resonance and Neptune's 2:1 mean motion resonance where the theory for the Laplace surface is likely to be inaccurate. These results do not support a previously reported anomalous warp at semimajor axes above 50 au.

Keywords: Celestial mechanics, Kuiper belt, Classical Kuiper belt objects, Orbital theory