Sazuna/UAT_keywords huggingface dataset:
The DESI Survey Validation: Results from Visual Inspection of the Quasar Survey Spectra. A key component of the Dark Energy Spectroscopic Instrument (DESI) survey validation (SV) is a detailed visual inspection (VI) of the optical spectroscopic data to quantify key survey metrics. In this paper we present results from VI of the quasar survey using deep coadded SV spectra. We show that the majority (≈70%) of the main-survey targets are spectroscopically confirmed as quasars, with ≈16% galaxies, ≈6% stars, and ≈8% low-quality spectra lacking reliable features. A nonnegligible fraction of the quasars are misidentified by the standard spectroscopic pipeline, but we show that the majority can be recovered using post-pipeline "afterburner" quasar-identification approaches. We combine these "afterburners" with our standard pipeline to create a modified pipeline to increase the overall quasar yield. At the depth of the main DESI survey, both pipelines achieve a good-redshift purity (reliable redshifts measured within 3000 km s-1) of ≈99%; however, the modified pipeline recovers ≈94% of the visually inspected quasars, as compared to ≈86% from the standard pipeline. We demonstrate that both pipelines achieve a median redshift precision and accuracy of ≈100 km s-1 and ≈70 km s-1, respectively. We constructed composite spectra to investigate why some quasars are missed by the standard pipeline and find that they are more host-galaxy dominated (i.e., distant analogs of "Seyfert galaxies") and/or more dust reddened than the standard-pipeline quasars. We also show example spectra to demonstrate the overall diversity of the DESI quasar sample and provide strong-lensing candidates where two targets contribute to a single spectrum.

Keywords: Cosmology, Observational cosmology, Quasars
Planetary Orbit Eccentricity Trends (POET). I. The Eccentricity-Metallicity Trend for Small Planets Revealed by the LAMOST-Gaia-Kepler Sample. Orbital eccentricity is one of the basic planetary properties, whose distribution may shed light on the history of planet formation and evolution. Here, in a series of works on Planetary Orbit Eccentricity Trends (dubbed POET), we study the distribution of planetary eccentricities and their dependence on stellar/planetary properties. In this paper, the first work of the POET series, we investigate whether and how the eccentricities of small planets depend on stellar metallicities (e.g., [Fe/H]). Previous studies on giant planets have found a significant correlation between planetary eccentricities and their host metallicities. Nevertheless, whether such a correlation exists for small planets (e.g., super-Earths and sub-Neptunes) remains unclear. Here, benefiting from the large and homogeneous LAMOST-Gaia-Kepler sample, we characterize the eccentricity distributions of 244 (286) small planets in single (multiple) transiting systems with the TDR method. We confirm the eccentricity-metallicity trend whereby the eccentricities of single small planets increase with stellar metallicities. Interestingly, a similar trend between eccentricity and metallicity is also found in the radial velocity sample. We also found that the mutual inclination of multiple transiting systems increases with metallicity, which predicts a moderate eccentricity-metallicity rising trend. Our results of the correlation between eccentricity (inclination) and metallicity for small planets support the core accretion model for planet formation, and they could be footprints of self (and/or external) excitation processes during the history of planet formation and evolution.

Keywords: Exoplanets, Planet hosting stars
Target Selection and Validation of DESI Emission Line Galaxies. The Dark Energy Spectroscopic Instrument (DESI) will precisely constrain cosmic expansion and the growth of structure by collecting ~40 million extragalactic redshifts across ~80% of cosmic history and one-third of the sky. The Emission Line galaxy (ELG) sample, which will comprise about one-third of all DESI tracers, will be used to probe the universe over the 0.6 &lt; z &lt; 1.6 range, including the 1.1 &lt; z &lt; 1.6 range, which is expected to provide the tightest constraints. We present the target selection for the DESI Survey Validation (SV) and Main Survey ELG samples, which relies on the imaging of the Legacy Surveys. The Main ELG selection consists of a g-band magnitude cut and a (g - r) versus (r - z) color box, while the SV selection explores extensions of the Main selection boundaries. The Main ELG sample is composed of two disjoint subsamples, which have target densities of about 1940 deg-2 and 460 deg-2, respectively. We first characterize their photometric properties and density variations across the footprint. We then analyze the DESI spectroscopic data that have been obtained from 2020 December to 2021 December in the SV and Main Survey. We establish a preliminary criterion for selecting reliable redshifts, based on the [O II] flux measurement, and assess its performance. Using this criterion, we are able to present the spectroscopic efficiency of the Main ELG selection, along with its redshift distribution. We thus demonstrate that the Main selection 1940 deg-2 subsample alone should provide 400 deg-2 and 460 deg-2 reliable redshifts in the 0.6 &lt; z &lt; 1.1 and the 1.1 &lt; z &lt; 1.6 ranges, respectively.

Keywords: Surveys, Emission line galaxies, Large-scale structure of the universe
Optical Spectroscopic Observations of Gamma-Ray Blazar Candidates. XII. Follow-up Observations from SOAR, Blanco, NTT, and OAN-SPM. Roughly one third of the sources in the Fermi-LAT catalogs are listed as unidentified/unassociated γ-ray sources (UGS), i.e., they lack a low-energy counterpart. In addition, there is a growing population of blazars of uncertain type (BCUs). Spectroscopic observations are crucial to confirm the blazar nature of the UGSs candidate counterparts and BCUs. Hence, in 2013 we started an optical spectroscopic campaign to carry out the identifications and classifications. In this paper, as a continuation of the campaign we report the spectra of 39 sources: the sample comprises 37 sources classified as BCUs, one source classified as a BL Lac in the Fourth Source Catalog of the Fermi-LAT (4FGL), and one source classified as UGS. We classify 19 of the sources in the sample as BL Lacs, 13 as blazars with nonnegligible host-galaxy emission, six as Flat Spectrum Radio Quasars, and one as a normal elliptical galaxy. The source listed as BL Lac in the 4FGL seems to be a blazar with nonnegligible host-galaxy emission in our observations, most likely due to an ongoing quiescent state. We classified the UGS source as a BL Lac. Six out of the 39 sources were previously reported in the campaign; in general, both the classifications and redshifts are in agreement, except for one of them with no redshift reported before. Altogether, we provided reliable redshift estimates to 21 out of the 39 sources. Finally, we describe the statistics of the data collected in our campaign so far.

Keywords: Optical identification, Flat-spectrum radio quasars, BL Lacertae objects, Blazars
Precise Distance Measurement for a Near-Earth Asteroid by the Refined Rotational Reflex Velocity Method. The rotational reflex velocity (RRV) method was proposed by Heinze and Metchev in 2015 and was used to measure the distances of main-belt asteroids (MBAs). Later, Lin et al. generalized this method using spherical astronomy in 2016. The method measures the distances of MBAs using the observations from a single ground-based telescope over two nights. We refined this method and extend it further to the distance measurement of near-Earth asteroids (NEAs). In practice, we measure the distance of the potentially hazardous asteroid (99942) Apophis from the acquired CCD frames using the newly refined method. According to the requirement of the newly refined method, we also simulate the distance measurements of the four typical NEAs, (1221) Amor, (1862) Apollo, (2062) Aten, and (163693) Atira, on their discovery dates and follow-up dates. The measurement results of Apophis based on the newly refined RRV method show that the mean relative errors for the independent exposure frames on the successive two nights is ~0.08% (about a factor of 2 improvement in comparison with the research of Lin et al.) compared with the distance from JPL ephemeris. Our simulation results also show that this refined method can accurately and precisely measure the distances of newly discovered NEAs in an astrometric way without performing orbital determination. The accurate and precise distances of newly discovered asteroids help us to conveniently evaluate their impact risks within a shorter time, leaving us more time to take defense precautions.

Keywords: Asteroids, Astronomy data analysis, Astrometry, Astronomy image processing
Measuring the Obliquities of the TRAPPIST-1 Planets with MAROON-X. A star's obliquity with respect to its planetary system can provide us with insight into the system's formation and evolution, as well as hinting at the presence of additional objects in the system. However, M dwarfs, which are the most promising targets for atmospheric follow-up, are underrepresented in terms of obliquity characterization surveys due to the challenges associated with making precise measurements. In this paper, we use the extreme-precision radial velocity (RV) spectrograph MAROON-X to measure the obliquity of the late M dwarf TRAPPIST-1. With the Rossiter-McLaughlin effect, we measure a system obliquity of $-2{^\circ }_{-{19}^{\circ }}^{+{17}^{\circ }}$ and a stellar rotational velocity of 2.1 ± 0.3 km s-1. We were unable to detect stellar surface differential rotation, and we found that a model in which all planets share the same obliquity was favored by our data. We were also unable to make a detection of the signatures of the planets using Doppler tomography, which is likely a result of the both the slow rotation of the star and the low signal-to-noise ratio of the data. Overall, TRAPPIST-1 appears to have a low obliquity, which could imply that the system has a low primordial obliquity. It also appears to be a slow rotator, which is consistent with past characterizations of the system and estimates of the star's rotation period. The MAROON-X data allow for a precise measurement of the stellar obliquity through the Rossiter-McLaughlin effect, highlighting the capabilities of MAROON-X and its ability to make high-precision RV measurements around late, dim stars.

Keywords: Extrasolar rocky planets, M dwarf stars
NICMOS Kernel-phase Interferometry. II. Demographics of Nearby Brown Dwarfs. Star formation theories have struggled to reproduce binary brown dwarf population demographics (e.g., frequency, separation, and mass ratio). Kernel-phase interferometry is sensitive to companions at separations inaccessible to classical imaging, enabling tests of these theories at new physical scales below the hydrogen burning limit. We analyze the detections and sensitivity limits from our previous kernel-phase analysis of archival HST/NICMOS surveys of field brown dwarfs. After estimating physical properties of the 105 late-M to T dwarfs using Gaia distances and evolutionary models, we use a Bayesian framework to compare these results to a model companion population defined by log-normal separation and power-law mass-ratio distributions. When correcting for Malmquist bias, we find a companion fraction of $F={0.11}_{-0.03}^{+0.04}$ and a separation distribution centered at $\rho ={2.2}_{-1.0}^{+1.2}$ au, smaller and tighter than seen in previous studies. We also find a mass-ratio power-law index that strongly favors equal-mass systems: $\gamma ={4.0}_{-1.5}^{+1.7}-{11}_{-3}^{+4}$ depending on the assumed age of the field population (0.9-3.1 Gyr). We attribute the change in values to our use of kernel-phase interferometry, which enables us to resolve the peak of the semimajor axis distribution with significant sensitivity to low-mass companions. We confirm the previously seen trends of decreasing binary fraction with decreasing mass and a strong preference for tight and equal-mass systems in the field-age substellar regime; only ${0.9}_{-0.6}^{+1.1}$ % of systems are wider than 20 au and $\lt {1.0}_{-0.6}^{+1.4}$ % of systems have a mass ratio q &lt; 0.6. We attribute this to turbulent fragmentation setting the initial conditions followed by a brief period of dynamical evolution, removing the widest and lowest-mass companions, before the birth cluster dissolves.

Keywords: Brown dwarfs, Binary stars, Direct detection interferometry, Hubble Space Telescope, L dwarfs, Infrared astronomy, Direct imaging, Star formation, T dwarfs
An Earth-sized Planet around an M5 Dwarf Star at 22 pc. We report on the discovery of an Earth-sized transiting planet (R  p  = 1.015 ± 0.051 R ⊕) in a P = 4.02 day orbit around K2-415 (EPIC 211414619), an M5V star at 22 pc. The planet candidate was first identified by analyzing the light-curve data obtained by the K2 mission, and it is here shown to exist in the most recent data from TESS. Combining the light curves with the data secured by our follow-up observations, including high-resolution imaging and near-infrared spectroscopy with IRD, we rule out false-positive scenarios, finding a low false-positive probability of 2 × 10‑4. Based on IRD's radial velocities of K2-415, which were sparsely taken over three years, we obtain a planet mass of 3.0 ± 2.7 M ⊕ (M  p  &lt; 7.5 M ⊕ at 95% confidence) for K2-415b. Being one of the lowest-mass stars (≈0.16 M ⊙) known to host an Earth-sized transiting planet, K2-415 will be an interesting target for further follow-up observations, including additional radial velocity monitoring and transit spectroscopy.

Keywords: High resolution spectroscopy, Exoplanet formation, Radial velocity, Transit photometry, High angular resolution
Multibeam Blind Search of Targeted SETI Observations toward 33 Exoplanet Systems with FAST. The search for extraterrestrial intelligence (SETI) is to search for technosignatures associated with extraterrestrial life, such as engineered radio signals. In this paper, we apply the multibeam coincidence matching (MBCM) strategy, and propose a new search mode based on the MBCM which we call the MBCM blind search mode. In our recent targeted SETI research, 33 exoplanet systems are observed by the Five-hundred-meter Aperture Spherical radio Telescope (FAST). With this blind search mode, we search for narrowband drifting signals across 1.05-1.45 GHz in two orthogonal linear polarization directions separately. There are two special signals, one of which can only be detected by the blind search mode while the other can be found by both blind and targeted search modes. This result reveals huge advantages of the new blind search mode. However, we eliminate the possibility of the special signals being ETI signals based on much evidence, such as the polarization, drift, frequency, and beam coverage characteristics. Our observations achieve an unprecedented sensitivity and our work provides a deeper understanding to the polarization analysis of extraterrestrial signals.

Keywords: Search for extraterrestrial intelligence, Technosignatures, Astrobiology, Exoplanets
The Direct Mid-infrared Detectability of Habitable-zone Exoplanets around Nearby Stars. Giant planets within the habitable zones of the closest several stars can currently be imaged with ground-based telescopes. Within the next decade, the Extremely Large Telescopes (ELTs) will begin to image the habitable zones of a greater number of nearby stars with much higher sensitivity, potentially imaging exo-Earths around the closest stars. To determine the most promising candidates for observations over the next decade, we establish a theoretical framework for the direct detectability of Earth- to super-Jovian-mass exoplanets in the mid-infrared based on available atmospheric and evolutionary models. Of the 83 closest BAFGK-type stars, we select 37 FGK-type stars within 10 pc and 34 BA-type stars within 30 pc with reliable age constraints. We prioritize targets based on a parametric model of a planet's effective temperature based on a star's luminosity, distance, and age, and on the planet's orbital semimajor axis, radius, and albedo. We then predict the most likely planets to be detectable with current 8 m telescopes and with a 39 m ELT with up to 100 hr of observation per star. Putting this together, we recommend observation times needed for the detection of habitable-zone exoplanets spanning the range from very nearby temperate Earth-sized planets to more distant young giant planets. We then recommend ideal initial targets for current telescopes and the upcoming ELTs.

Keywords: Exoplanet astronomy, Direct imaging, Extrasolar rocky planets
Characterization of a Set of Small Planets with TESS and CHEOPS and an Analysis of Photometric Performance. The radius valley carries implications for how the atmospheres of small planets form and evolve, but this feature is visible only with highly precise characterizations of many small planets. We present the characterization of nine planets and one planet candidate with both NASA TESS and ESA CHEOPS observations, which adds to the overall population of planets bordering the radius valley. While five of our planets-TOI 118 b, TOI 262 b, TOI 455 b, TOI 560 b, and TOI 562 b-have already been published, we vet and validate transit signals as planetary using follow-up observations for four new TESS planets, including TOI 198 b, TOI 244 b, TOI 444 b, and TOI 470 b. While a three times increase in primary mirror size should mean that one CHEOPS transit yields an equivalent model uncertainty in transit depth as about nine TESS transits in the case that the star is equally as bright in both bands, we find that our CHEOPS transits typically yield uncertainties equivalent to between two and 12 TESS transits, averaging 5.9 equivalent transits. Therefore, we find that while our fits to CHEOPS transits provide overall lower uncertainties on transit depth and better precision relative to fits to TESS transits, our uncertainties for these fits do not always match expected predictions given photon-limited noise. We find no correlations between number of equivalent transits and any physical parameters, indicating that this behavior is not strictly systematic, but rather might be due to other factors such as in-transit gaps during CHEOPS visits or nonhomogeneous detrending of CHEOPS light curves.

Keywords: Exoplanet astronomy, Mini Neptunes, Extrasolar rocky planets
A Survey of Herbig Ae/Be Multiplicity. Although the majority of Herbig Ae/Be (HAEBE) stars are likely multiple systems, relatively few multiples have been identified. We aim to create a statistically significant survey of HAEBE multiplicity as a function of stellar mass, to shed light on mixed-mass star formation. Two independent adaptive optics IR imaging surveys were conducted, between 1993 and 2007. A total of 143 stars were observed, including 126 HAEBE stars. These surveys are significantly more sensitive than previous imaging work and, combined with accurate distance and proper-motion data from GAIA Data Release 3, provide a broad survey of intermediate-mass multiplicity. We perform a statistical probability analysis to identify the likely physical companions, and analyze multiepoch observations for common proper motions. We find 250 stellar detections around 88 sample stars. Of these, 70 systems are likely multiple systems, and 42 companions around 29 systems are reported here for the first time. Correcting for completeness, we find a multiplicity fraction of 54%. Multiples are found randomly across all spectral types, but high-order multiples are more common among the hottest stars. Statistically likely companions are found at distances of up to several thousand astronomical units and ∆K magnitudes ranging from &lt;0.1 to ~9, although companions with ∆K &lt; 1.5 are rare. Companions around Herbig Ae stars tend to be closer than those around Herbig Be stars. We confirm 24 proper-motion companions in 21 systems, including roughly half of the statistically very likely companions; however, many proper-motion results are inconclusive.

Keywords: Surveys, Herbig Ae/Be stars, Multiple stars
A Distance Measurement to M33 Using Optical Photometry of Mira Variables. We present a systematic analysis to determine and improve the pulsation periods of 1637 known long-period Mira variables in M33 using gri-band light curves spanning ~18 yr from several surveys, including the M33 variability survey, Panoramic Survey Telescope and Rapid Response System, Palomar Transient Factory (PTF), intermediate PTF, and Zwicky Transient Facility. Based on these collections of light curves, we found that optical-band light curves that are as complete as possible are crucial to determine the periods of distant Miras. We demonstrated that the machine-learning techniques can be used to classify Miras into O-rich and C-rich based on the (J - K  s ) period-color plane. Finally, We derived the distance modulus to M33 using O-rich Miras at maximum light together with our improved periods as 24.67 ± 0.06 mag, which is in good agreement with the recommended value given in the literature.

Keywords: Asymptotic giant branch stars, Mira variable stars
Detecting Long-period Variability in the SDSS Stripe 82 Standards Catalog. We report the results of a search for long-period (100 &lt; P &lt; 600 days) periodic variability in the SDSS Stripe 82 standards catalog. The SDSS coverage of Stripe 82 enables such a search because there are on average 20 observations per band in ugriz bands for about one million sources, collected over about 6 yr, with a faint limit of r ~ 22 mag and precisely calibrated 1%-2% photometry. We calculated the periods of variable source candidates in this sample using the Lomb-Scargle periodogram and considered the three highest periodogram peaks in each of the gri filters as relevant. Only those sources with gri periods consistent within 0.1% were later studied. We use the Kuiper statistic to ensure uniform distribution of data points in phased light curves. We present five sources with the spectra consistent with quasar spectra and plausible periodic variability. This SDSS-based search bodes well for future sensitive large-area surveys, such as the Rubin Observatory Legacy Survey of Space and Time, which, due to its larger sky coverage (about a factor of 60) and improved sensitivity (~2 mag), will be more powerful for finding such sources.

Keywords: Period determination, Quasars, Astronomy data analysis, Gravitational wave sources, Time series analysis
The Celestial Reference Frame at K Band: Imaging. I. The First 28 Epochs. We present K-band (24 GHz) images of 731 compact extragalactic radio sources with submilliarcsecond resolution, based on radio interferometric observations made with the Very Long Baseline Array of 10 telescopes during 29 day long sessions spanning from 2015 to 2018 and recorded at 2048 Mbps. Many of these sources are imaged with submilliarcsecond resolution for the first time at frequencies above X band (8 GHz). From each of the K-band images, we derive the following source properties: peak brightness, core and total flux density, the ratio of peak and core to total flux (compactness measure), radial source extent, structure index, source size, and jet direction. The vast majority of sources are imaged at multiple epochs, providing insights into their temporal behavior. The use of K band was motivated by the fact that the sources are generally intrinsically more compact at higher frequencies, as well as by the factor of 3 improvement in interferometer resolution relative to the historically standard S/X band (2.3/8.4 GHz) used for a large amount of reference frame and calibrator work. Lastly, as most of the sources imaged here are in the K-band component of the third International Celestial Reference Frame, these images serve to characterize the objects used in that International Astronomical Union standard.

Keywords: Observational astronomy, Astronomical coordinate systems, Radio source catalogs, Extragalactic radio sources, Very long baseline interferometry, Radio astrometry, Radio continuum emission, High angular resolution