Sazuna/UAT_keywords huggingface dataset:
WASP-121 b's Transmission Spectrum Observed with JWST/NIRSpec G395H Reveals Thermal Dissociation and SiO in the Atmosphere. WASP-121 b has been established as a benchmark ultrahot Jupiter, serving as a laboratory for the atmospheric chemistry and dynamics of strongly irradiated extrasolar gas giants. Here, we present and analyze WASP-121 b's transmission spectrum observed with NIRSpec G395H on board the James Webb Space Telescope and find evidence for the thermal dissociation of H2O and H2 on the planet's permanent dayside. Additionally, we detect SiO at a statistical significance of 5.2σ, which is compatible with chemical equilibrium in the atmosphere. Constraining the abundance of SiO and abundance ratios between silicon and volatile atoms in WASP-121 b's atmosphere could help discriminate between possible migration histories of the planet. The three-dimensional nature of thermal dissociation on WASP-121 b's dayside and of recombination on its nightside, however, poses a challenge to constraining molecular abundances and elemental abundance ratios from the transmission spectrum. To account for this, we implemented an atmospheric model in the NEMESIS framework that splits the planet's atmosphere into dayside and nightside. A retrieval applying our atmospheric model to WASP-121 b's transmission spectrum favors a higher H2O abundance on the nightside than on the dayside, demonstrating the impact of hemispheric heterogeneity when attempting to constrain WASP-121 b's bulk H2O inventory.

Keywords: Exoplanet atmospheric composition , Infrared spectroscopy, Transmission spectroscopy
Observations and Studies on the Transiting Systems HAT-P-36, XO-2 and WASP-76. We conducted photometric observations for transit events of three exoplanetary systems HAT-P-36, XO-2 and WASP-76 using the 1 m and 2.4 m telescopes at Yunnan Observatories and the 0.85 m telescope at National Astronomical Observatories of China. By combining the photometric data from the TESS mission, we have performed a detailed analysis for the obtained transit light curves using the Markov chain Monte Carlo technique, and obtained precise transit midtimes for the three systems. Based on our new measurements and other available transit mid-times, we have determined more accurate orbital periods for these systems. From the analysis, we find that all of these planetary systems exhibit certain transit-timing variations (TTVs). The TTV patterns are simulated by using the constant period model, orbital decay model and apsidal precession model, but we do not obtain reasonable models to account for the TTVs. Furthermore, to assess the presence of additional planets in these systems, we have constrained the masses of perturbing planets using the root mean square (rms) values of the observed TTVs and the rms values of radial velocity residuals. The results demonstrate that, under the condition of mean motion resonances, these systems may harbor perturbing planets with masses from a few tenths to more than one hundred Earth mass.

Keywords: Markov chain Monte Carlo, Transits, Photometry, Transit timing variation method
Searching for GEMS: Two Super-Jupiters Around M Dwarfs that May have Formed via Gravitational Instability. We present the discovery of TOI-6303b and TOI-6330b, two massive transiting super-Jupiters orbiting a M0 and a M2 dwarf star, respectively, as part of the Searching for Giant Exoplanets around M-dwarf Stars (GEMS) survey. These were detected by NASA's Transiting Exoplanet Survey Satellite and then confirmed via ground-based photometry and radial velocity observations with the Habitable-zone Planet Finder. TOI-6303b has a mass of 7.84 ± 0.31 MJ, a radius of 1.03 ± 0.06 RJ, and an orbital period of 9.485 days. TOI-6330b has a mass of 10.00 ± 0.31 MJ, a radius of 0.97 ± 0.03 RJ, and an orbital period of 6.850 days. We put these planets in the context of super-Jupiters around M dwarfs discovered from radial-velocity surveys, as well as recent discoveries from astrometry. These planets have masses that can be attributed to two dominant planet formation mechanisms—gravitational instability and core accretion. Their masses necessitate massive protoplanetary disks that should either be gravitationally unstable, i.e., forming through gravitational instability, or be among the most massive protoplanetary disks known to date to form objects through core accretion. We also discuss their possible migration mechanisms via their eccentricity distribution.

Keywords: M dwarf stars, Transits, Hot Jupiters, Exoplanets, Exoplanet astronomy, Radial velocity
Metallicity Distribution in M31 and M33 Based on the Tip of the Red Giant Branch Near-infrared Color. This study investigates the metallicity distribution in M31 and M33 by using the near-infrared color index J ‑ K of the tip of the red giant branch (TRGB) of the member stars from Y. Ren et al. after removing foreground dwarf stars by a near-infrared J ‑ H versus H ‑ K diagram as well as Gaia astrometric measurements. We employ the Voronoi binning technique to divide the galaxy into subregions, the Poisson noise method to determine the TRGB position in the J ‑ K versus K diagram, and the bootstrap method to estimate uncertainties. The TRGB positions are calculated to be J ‑ K = 1.195 ± 0.002 and 1.100 ± 0.003, and K = 17.615 ± 0.007 and 18.185 ± 0.053 for M31 and M33, respectively, consistent with previous results. The J ‑ K gradient of M31 is found to be ‑0.0055 kpc‑1 at RGC = (0, 24) kpc and ‑0.0002 kpc‑1 at RGC = (24, 150) kpc. Notably, two dust rings are evident at 11.5 and 14.5 kpc, in agreement with previous studies. The J ‑ K of M33 is analyzed in four directions and generally shows a trend of gradually decreasing from the inside to the outside, however, it shows an increasing trend of 0.022 kpc‑1 in the inner 0–2 kpc in the west. Through the color–metallicity relation of the TRGB, the metallicity gradient of M31 is ‑0.040 ± 0.0012 dex kpc‑1 for RGC &lt; 30 kpc and ‑0.001 ± 0.0002 dex kpc‑1 for RGC &gt; 30 kpc, and for M33, it is ‑0.269 ± 0.0206 dex kpc‑1 for RGC &lt; 9 kpc.

Keywords: Andromeda Galaxy, Red giant tip, Triangulum Galaxy, Metallicity
Searching for Additional Planets in TESS Multiplanet Systems: Testing Empirical Models Based on Kepler Data. Multiplanet system architectures are frequently used to constrain possible formation and evolutionary pathways of observed exoplanets. Therefore, understanding the predictive and descriptive power of empirical exoplanetary system models is critical to understanding their formation histories. We analyze 52 TESS multiplanet systems previously studied using DYNAMITE, which used TESS data alongside empirical models based on Kepler planets to predict additional planets in each system. We analyze additional TESS data to search for these predicted planets. We thereby evaluate the degree to which these models can be used to predict planets in TESS multiplanet systems. Specifically, we study whether the period ratio method or clustered period model is more predictive. We find that the period ratio model predictions are most consistent with the planets discovered since 2020, accounting for detection sensitivity. However, neither model is highly predictive, highlighting the need for additional data and more nuanced models to describe the full population. Improved eccentricity and dynamical stability prescriptions incorporated into DYNAMITE provide a modest improvement in the prediction accuracy. We also find that the current sample of 183 TESS multiplanet systems are highly dynamically packed, and appear truncated relative to detection biases. These attributes are consistent with the Kepler sample, and suggest an efficient formation process.

Keywords: Exoplanet astronomy, Exoplanet detection methods, Transit photometry
Serial MultiView: An Efficient Approach to Mitigating Atmospheric Spatial-structure Errors for Very-long-baseline-interferometry Astrometry. Atmospheric propagation errors are a main constraint on the accuracy of very-long-baseline-interferometry astrometry. For relative astrometry, differential techniques can mitigate these errors, but their effectiveness diminishes with decreasing elevation and increasing angular separations between target and calibrator, among others. The MultiView technique addresses atmospheric spatial-structure errors by observing multiple calibrators around the target and interpolating at the target position, thereby reducing atmospheric errors more effectively than phase referencing with only one calibrator. The first MultiView realisation at 1.6 GHz involved cyclically observing all calibrators and the target, fitting a phase plane from calibrator solutions in each cycle, and is a well-established technique. This implementation reduces on-target time and is constricted by the short atmospheric coherence time at high frequencies. We propose a new realisation, serial MultiView, which rotates the phase plane iteratively based on the time series of calibrator residual phases. This new strategy obviates the necessity of observing all calibrators within each cycle, thereby shortening the observing cycle and offering considerable potential at higher frequencies where the temporal structure is the dominant source of errors. Additionally, by incorporating time-domain information in the iterations, phase ambiguities can be accurately and automatically identified. We verify the astrometric accuracy of serial MultiView at 5 GHz by comparing it to conventional MultiView, achieving &lt;10 μas error in R.A. direction, and show the calibration overhead can be reduced in both approaches. This approach enables efficient, high-accuracy differential astrometry and artifact-reduced imaging for astrophysical studies, and we provide a user-friendly tool for it.

Keywords: Very long baseline interferometry, Radio astrometry
The Telescope Calibration of the Imaging X-Ray Polarimetry Explorer. Fifty years after the very first sounding rocket measurement of cosmic X-ray polarization, the Imaging X-ray Polarimetry Explorer (IXPE) mission has effectively opened a new window into the X-ray sky. Prior to launch of IXPE, an extensive calibration campaign was carried out to fully characterize the response of this new type of instrument. Specifically, the polarization-sensitive detectors were intensively calibrated in Italy, where they were developed and built. The X-ray optics, which collect and focus X-rays onto the detectors, were built and calibrated in the USA. A key question was whether the telescope (optics + detectors) calibrations could be synthesized from the individual component calibrations, avoiding time consuming and costly end-to-end calibrations for a flight program with a fixed schedule. The data presented here are from a calibration of the flight spare telescope utilizing the flight spare detector and flight spare mirror assembly combined. These data show that the presence of the mirror module does not affect the polarization response of the detectors (within the required calibration accuracy) and that the angular resolution of the telescopes could be accurately determined. Thus, the original extensive stand-alone ground calibration data of all the flight detectors and all the flight optic can be utilized in full to derive the flight telescopes calibrations.

Keywords: Calibration, Astronomical techniques, X-ray observatories, Flux calibration
Drone Beam Mapping of the TONE Radio Dish Array. Drone-based beam measurements are a promising avenue to tackle the critical challenge of calibration for 21 cm cosmology telescopes. In this paper, we introduce a new drone-based calibration system for 400–800 MHz radio observatories, describing its instrumentation and first deployment. We discuss measurements of the TONE array, a CHIME/FRB outrigger pathfinder, and present results, including full 2D high spatial resolution beam maps in both co- and cross-polarization, as well as comparisons to simulations. The polarized beam maps cover a 70∘ × 70∘ grid, capturing the first two sidelobes and measuring the TONE main beam and first sidelobe with 7%–9% statistical errors. We investigate polarization angle alignment with frequency, finding significant polarization leakage in the TONE antennas at frequencies above 600 MHz, and a polarization axis rotation with frequency. We describe statistical and systematic errors, as well as measurements of radio frequency interference (RFI) from the drone and equipment. Our drone system is the first to incorporate a broadband switched calibration source in the drone payload, enabling background subtraction and direct measurements of the RFI emitted by the drone. The results presented are the first drone-based 2D measurements of cross-polar beam structure and of polarization alignment of an array. The high frequency and spatial resolution achieved with this system have revealed the rich structure of the beam of each antenna, and enabled comparisons between individual dishes and to electromagnetic simulations.

Keywords: Calibration, Radio astronomy, Radio interferometers
Improving Harmonic Analysis Using Multitapering: Precise Frequency Estimation of Stellar Oscillations Using the Harmonic F-test. In Patil et al., we developed a power spectrum estimation method, mtNUFFT (or multitaper nonuniform fast Fourier transform), for analyzing time series with quasi-regular spacing, and showed that it not only improves upon the statistical issues of the Lomb–Scargle (LS) periodogram, but also provides a factor of 3 speedup in some applications. In this paper, we extend mtNUFFT to include a multitaper F-test, a hypothesis test to assess whether a strictly periodic signal or its harmonic (as opposed to, e.g., a quasi-periodic signal) is present at a given frequency. This extension is possible because the F-test is an accompaniment to the multitaper power spectrum estimator (as opposed to other estimators such as the LS periodogram). The mtNUFFT/F-test combination allows detection of strictly periodic signals embedded in noise and precise estimation of their frequencies, in addition to power spectrum estimation. Using asteroseismic time-series data for the Kepler-91 red giant, we show that the F-test automatically picks up the harmonics of its transiting exoplanet as well as certain dipole (l = 1) mixed modes. We use this example to highlight that we can distinguish between different types of stellar oscillations, e.g., transient (damped, stochastically excited) and strictly periodic (undamped, heat driven). We also illustrate the technique of dividing a time series into chunks to further examine the transient versus periodic nature of stellar oscillations. The harmonic F-test combined with mtNUFFT is implemented in the public Python package tapify, which opens opportunities to perform detailed investigations of periodic signals in time-domain astronomy.

Keywords: Astrostatistics, Stellar physics, Time domain astronomy, Exoplanet detection methods, Asteroseismology, Time series analysis
Measuring Interstellar Carbon Abundance via 158 μm [C II] Absorption with SOFIA—A Potential Detection and Proof-of-concept for Depletion Studies with Future Far-IR Facilities. Carbon plays key roles in the interstellar medium (ISM)—as a constituent of dust, as the carrier of the dominant far-infrared (FIR) cooling line, and as a component of various important molecules. But despite this, there are very few measurements of the abundance and depletion of carbon in the diffuse ISM. As with other elements, these measurements are traditionally performed in the ultraviolet. But for carbon, such measurements are extremely difficult, and fewer than 20 have been reported in the literature to date. Here, we present a novel method of measuring the abundance and depletion of carbon in the diffuse ISM: by observing absorption of the 158 μm [C II] line in the FIR. We present a catalog of 432 candidate sightlines that use bright nearby galaxies as background sources, and predict the [C II] absorption expected toward each. We conducted a pilot study using SOFIA, targeting sightlines toward the galaxies IC 342 and Circinus. We report a potential detection of Galactic [C II] absorption along the IC 342 sightline, although it requires disentangling [C II] emission from IC 342 itself. The Circinus sightline had an insufficiently stable instrumental baseline to allow a detection. This SOFIA study informs the prospects for [C II] absorption measurements with future facilities. To that end, we explore the potential for four proposed future FIR telescopes—PRIMA, FIRSST, SALTUS, and Origins—to detect [C II] absorption. We find that all four facilities would be able to detect [C II] absorption along a significant number of sightlines.

Keywords: Interstellar line absorption, Interstellar abundances, Far infrared astronomy, Astronomical techniques, Infrared telescopes, Space telescopes
RVSNUpy: A Python Package for Spectroscopic Redshift Measurement Based on Cross Correlation. We introduce RVSNUpy, a new Python package designed to measure spectroscopic redshifts. Based on inverse-variance-weighted cross correlation, RVSNUpy determines redshifts by comparing observed spectra with various rest-frame template spectra. We test the performance of RVSNUpy based on ∼6000 objects in the HectoMAP redshift survey observed with both the Sloan Digital Sky Survey (SDSS) and MMT/Hectospec. We demonstrate that a slight redshift offset (∼40 km s−1) between the SDSS and MMT/Hectospec measurements reported from previous studies results from the small offsets in the redshift template spectra used for SDSS and Hectospec reductions. We construct a universal set of template spectra, including empirical SDSS template spectra, carefully calibrated to the rest frame. Our test for the HectoMAP objects with duplicated observations shows that RVSNUpy with the universal template spectra yields homogeneous redshifts for spectra obtained with different spectrographs. We highlight that RVSNUpy is a powerful redshift measurement tool for current and future large-scale spectroscopy surveys, including A-SPEC, DESI, 4MOST, and the Subaru Prime Focus Spectrograph.

Keywords: Redshift surveys, Astronomical techniques, Galaxy spectroscopy, Astronomical methods
Variable Polarization of WR 31a: Binary Companion or Corotating Interaction Region?. WR 31a (Hen 3-519) is likely a postluminous blue variable (LBV) star that is evolving to become a classical Wolf─Rayet star. Multicolor (UBVR) photopolarimetric observations of WR 31a were obtained over nine nights in early-2007. The linear polarization data of WR 31a trace a "loop" structure in a Stokes Q − U diagram, which is similar in all four passbands. After mean subtraction, the four loops align to form a single overall pattern. Such loops can be expected to arise from binary systems. We test the binary hypothesis with two models. The data are fitted for a strictly circular orbit to derive an orbital period of 16.7 days, requiring a high inclination perspective of i ∼ 80°. We also consider an elliptical orbit under simplifying assumptions, yielding a match for i ∼ 75° with eccentricity e ∼ 0.5 and a longer orbital period of about 70 days. The prevalence of binarity among massive stars is well known; the prospect of detecting a binary companion during the post-LBV stage of WR 31a would add to an emerging narrative of diverse interactions between massive multiple components as a function of the evolutionary stage. However, if the loop originates because of a corotating interaction region, then the rotation period could be 8.5 days or 17 days. This would give an estimated equatorial rotation speed of 95 or 190 km s−1. Either of these is a significant fraction of the estimated critical speed of rotational break-up at 320 km s−1 (for an Eddington factor of Γ = 0).

Keywords: Luminous blue variable stars, Stellar mass loss, Stellar winds, Wolf-Rayet stars, Polarimetry
Minimizing Star-spot Contamination of Exoplanet Transit Spectroscopy Using Alternate Normalization. Recently, M. H. Currie et al. (2023) simulated the detection of molecules in the atmospheres of temperate rocky exoplanets transiting nearby M-dwarf stars. They simulated detections via spectral cross correlation applied to high-resolution optical and near-infrared transit spectroscopy using the Extremely Large Telescopes. Currie et al. did not consider the effect of unocculted star spots, but we do that here for possible detections of molecular oxygen, carbon dioxide, methane, and water vapor. We find that confusion noise from unocculted star spots becomes significant for large programs that stack tens to hundreds of transits to detect these molecules. Noise from star spots increases with greater spot filling factors, and star-spot temperature has less effect than filling factor. Nevertheless, molecular oxygen, carbon dioxide, and methane could be detected in temperate rocky planets transiting nearby M-dwarfs without correcting for star spots. Water vapor detections are the most affected, with star spots contaminating the exoplanet signal as well as producing extra noise. Unocculted spots only affect transit spectroscopy when normalizing by dividing by the total flux from the star. We describe an alternate normalization method that minimizes star-spot effects by deriving and implementing an unspotted proxy spectrum for the normalization. We show that the method works in principle using realistic levels of random observational noise. Alternate normalization would be broadly applicable to all types of transit spectroscopy, and we discuss challenges to applying it in practice. We also outline a comprehensive approach that has the potential to overcome those challenges.

Keywords: Exoplanet astronomy, Starspots, Exoplanet atmospheres
Using Anomaly Detection to Search for Technosignatures in Breakthrough Listen Observations. We implement a machine learning algorithm to search for extraterrestrial technosignatures in radio observations of several hundred nearby stars, obtained with the Parkes and Green Bank Telescopes by the Breakthrough Listen collaboration. Advances in detection technology have led to an exponential growth in data, necessitating innovative and efficient analysis methods. This problem is exacerbated by the large variety of possible forms an extraterrestrial signal might take, and the size of the multidimensional parameter space that must be searched. It is then made markedly worse by the fact that our best guess at the properties of such a signal is that it might resemble the signals emitted by human technology and communications, the main (yet diverse) contaminant in radio observations. We address this challenge by using a combination of simulations and machine learning methods for anomaly detection. We rank candidates by how unusual they are in frequency, and how persistent they are in time, by measuring the similarity between consecutive spectrograms of the same star. We validate that our filters significantly improve the quality of the candidates that are selected for human vetting when compared to a random selection. Of the ∼1011 spectrograms that we analyzed, we visually inspected thousands of the most promising spectrograms, and thousands more for validation, about 20,000 in total, and report that no candidate survived basic scrutiny.

Keywords: Search for extraterrestrial intelligence