Sazuna/UAT_keywords huggingface dataset:
Dynamical Structures under Nonrestricted Hierarchical Planetary Systems with Different Mass Ratios. Secular dynamics have been extensively studied in both the inner and outer restricted hierarchical three-body systems. In the inner restricted problem, the quadrupole-order resonance (i.e., the well-known Kozai resonance) causes large coupled oscillations of eccentricity and inclination when the maximum inclination is higher than 39.2°, and the octupole-order resonance leads to the behavior of orbital flips. In the outer restricted problem, the behavior of orbital flips is due to the quadrupole-order resonance. Secular dynamics under the inner and outer restricted systems are distinctly different. The mass ratio of inner and outer bodies could change the ratio of circular orbital angular momenta β, which significantly influences dynamical structures of the system. But this influence is still unclear. In this paper, we focus on nonrestricted hierarchical planetary systems where β &gt; 1 and investigate the secular dynamics by changing mass ratios. Dynamical structures are systematically explored from four aspects: periodic orbits, secular resonances, orbital flips, and chaos detection. We find that (a) it tends to lead to more bifurcations in the host family of prograde periodic orbits associated with Kozai resonance with smaller β; (b) with the decrease of β, fewer orbits inside the octupole-order resonance can realize flip; (c) for given initial conditions, the forbidden region appears in the retrograde region and becomes larger as β decreases, meaning that the mutual inclination cannot reach a very high value if β is small; and (d) chaotic orbits are distributed in the low-eccentricity, high-inclination region when β &gt; 1.

Keywords: Celestial mechanics, Three-body problem
Wide-spectral-band Nuller Insensitive to Finite Stellar Angular Diameter with a One-dimensional Diffraction-limited Coronagraph. Potentially habitable planets around nearby stars less massive than solar-type stars could join targets of the spectroscopy of the planetary reflected light with future space telescopes. However, the orbits of most of these planets occur near the diffraction limit for 6 m diameter telescopes. Thus, while securing contrast-mitigation ability under a broad spectral bandwidth and a finite stellar angular diameter, we must maintain planetary throughput even at the diffraction-limited angles to be able to reduce the effect of the photon noise within a reasonable observation time. A one-dimensional diffraction-limited coronagraph (1DDLC) observes planets near the diffraction limit with undistorted point spread functions but has a finite-stellar diameter problem in wideband use. This study presents a method for wide-spectral-band nulling insensitive to stellar-angular-diameter by adding a fiber nulling with a Lyot-plane phase mask to the 1DDLC. Designing the pattern of the Lyot-plane mask function focuses on the parity of the amplitude spread function of light. Our numerical simulation shows that the planetary throughput (including the fiber-coupling efficiency) can reach about 11% for about 1.35-λ/D planetary separation almost independently of the spectral bandwidth. The simulation also shows the raw contrast of about 4 × 10‑8 (the spectral bandwidth of 25%) and 5 × 10‑10 (the spectral bandwidth of 10%) for 3 × 10‑2 λ/D stellar angular diameter. The planetary throughput depends on the planetary azimuthal angle, which may degrade the exploration efficiency compared to an isotropic throughput but is partially offset the wide spectral band.

Keywords: High contrast techniques, Astronomical optics, Coronagraphic imaging, Astrobiology, Direct imaging
On the Rigidly Precessing, Eccentric Gas Disk Orbiting the White Dwarf SDSS J1228+1040. Metal pollution onto white dwarfs is a widespread phenomenon that remains puzzling. Some of these white dwarfs also harbor gaseous debris disks. Emission lines from these disks open a unique window to the physical properties of the polluting material, lending insights into their origin. We model the emission line kinematics for the gas disk around SDSS J1228+1040, a system that has been monitored for over two decades. We show that the disk mass is strongly peaked at 1 R ⊙ (modulo the unknown inclination), and the disk eccentricity decreases from a value of 0.44 at the inner edge, to nearly zero at the outer edge. This eccentricity profile is exactly what one expects if the disk is in a global eccentric mode, precessing rigidly under general relativity and gas pressure. The precession period is about two decades. We infer that the mass of the gas disk is roughly equivalent to that of a 50 km rocky body, while the mass of the accompanying dust disk is likely insignificant. The disk eccentricity confirms an origin in tidal disruption, while the short disk diffusion time suggests that the disruption event happened a few centuries ago. Moreover, we argue that the initial orbit for the disrupted body, and that of its putative planetary perturber, fall within an astronomical unit around the white dwarf. The total mass of the source population is likely orders of magnitude more massive than our own Asteroid belt and does not seem to exist around main-sequence stars.

Keywords: White dwarf stars, Circumstellar disks
High-precision Atmospheric Characterization of a Y Dwarf with JWST NIRSpec G395H Spectroscopy: Isotopologue, C/O Ratio, Metallicity, and the Abundances of Six Molecular Species. The launch of the James Webb Space Telescope (JWST) marks a pivotal moment for precise atmospheric characterization of Y dwarfs, the coldest brown dwarf spectral type. In this study, we leverage moderate spectral resolution observations (R ∼ 2700) with the G395H grating of the Near-Infrared Spectrograph (NIRSpec) on board JWST to characterize the nearby (9.9 pc) Y dwarf WISEPA J182831.08+265037.8. With the NIRSpec G395H 2.88–5.12 μm spectrum, we measure the abundances of CO, CO2, CH4, H2S, NH3, and H2O, which are the major carbon-, nitrogen-, oxygen-, and sulfur-bearing species in the atmosphere. Based on the retrieved volume mixing ratios with the atmospheric retrieval framework CHIMERA, we report that the C/O ratio is 0.45 ± 0.01, close to the solar C/O value of 0.458, and the metallicity is +0.30 ± 0.02 dex. Comparison between the retrieval results and the forward modeling results suggests that the model bias for C/O and metallicity could be as high as 0.03 and 0.97 dex, respectively. We also report a lower limit of the 12CO/13CO ratio of &gt;40, being consistent with the nominal solar value of 90. Our results highlight the potential for JWST to measure the C/O ratios down to percent-level precision and characterize isotopologues of cold planetary atmospheres similar to WISE 1828.

Keywords: Planetary atmospheres, Brown dwarfs, Y dwarfs, Exoplanet atmospheres
Planet Hunters NGTS: New Planet Candidates from a Citizen Science Search of the Next Generation Transit Survey Public Data. We present the results from the first two years of the Planet Hunters Next Generation Transit Survey (NGTS) citizen science project, which searches for transiting planet candidates in data from the NGTS by enlisting the help of members of the general public. Over 8000 registered volunteers reviewed 138,198 light curves from the NGTS Public Data Releases 1 and 2. We utilize a user weighting scheme to combine the classifications of multiple users to identify the most promising planet candidates not initially discovered by the NGTS team. We highlight the five most interesting planet candidates detected through this search, which are all candidate short-period giant planets. This includes the TIC-165227846 system that, if confirmed, would be the lowest-mass star to host a close-in giant planet. We assess the detection efficiency of the project by determining the number of confirmed planets from the NASA Exoplanet Archive and TESS Objects of Interest (TOIs) successfully recovered by this search and find that 74% of confirmed planets and 63% of TOIs detected by NGTS are recovered by the Planet Hunters NGTS project. The identification of new planet candidates shows that the citizen science approach can provide a complementary method to the detection of exoplanets with ground-based surveys such as NGTS.

Keywords: Exoplanet astronomy, Transit photometry
A Perfect Tidal Storm: HD 104067 Planetary Architecture Creating an Incandescent World. The discovery of planetary systems beyond the solar system has revealed a diversity of architectures, most of which differ significantly from our system. The initial detection of an exoplanet is often followed by subsequent discoveries within the same system as observations continue, measurement precision is improved, or additional techniques are employed. The HD 104067 system is known to consist of a bright K-dwarf host star and a giant planet in a ∼55 days period eccentric orbit. Here we report the discovery of an additional planet within the HD 104067 system, detected through the combined analysis of radial velocity (RV) data from the High Resolution Echelle Spectrometer and High Accuracy Radial velocity Planet Searcher instruments. The new planet has a mass similar to Uranus and is in an eccentric ∼14 days orbit. Our injection-recovery analysis of the RV data exclude Saturn-mass and Jupiter-mass planets out to 3 au and 8 au, respectively. We further present Transiting Exoplanet Survey Satellite observations that reveal a terrestrial planet candidate (R  p  = 1.30 ± 0.12 R ⊕) in a ∼2.2 days period orbit. Our dynamical analysis of the three planet model shows that the two outer planets produce significant eccentricity excitation of the inner planet, resulting in tidally induced surface temperatures as high as ∼2600 K for an emissivity of unity. The terrestrial planet candidate may therefore be caught in a tidal storm, potentially resulting in its surface radiating at optical wavelengths.

Keywords: Exoplanet dynamics, Exoplanets, Orbits, Exoplanet systems, Exoplanet tides, Photometry, Radial velocity, Planetary dynamics
The Importance of Optical Wavelength Data on Atmospheric Retrievals of Exoplanet Transmission Spectra. Exoplanet transmission spectra provide rich information about the chemical composition, clouds, and temperature structure of exoplanet atmospheres. Most exoplanet transmission spectra only span infrared wavelengths (≳1 μm), which can preclude crucial atmospheric information from shorter wavelengths. Here, we explore how retrieved atmospheric parameters from exoplanet transmission spectra change with the addition of optical data. From a sample of 14 giant planets with transit spectra from 0.3─4.5 μm, primarily from the Hubble and Spitzer space telescopes, we apply a free chemistry retrieval to planetary spectra for wavelength ranges of 0.3─4.5 μm, 0.6─4.5 μm, and 1.1─4.5 μm. We analyze the posterior distributions of these retrievals and perform an information content analysis, finding wavelengths below 0.6 μm are necessary to constrain cloud scattering slope parameters (  $\mathrm{log}a$   and γ) and alkali species Na and K. There is limited improvement in the constraints on the remaining atmospheric parameters. Across the population, we find that limb temperatures are retrieved colder than planetary equilibrium temperatures but have an overall good agreement with Global Circulation Models. As the JWST extends to a minimum wavelength of 0.6 μm, we demonstrate that exploration into complementing JWST observations with optical HST data is important to further our understanding of aerosol properties and alkali abundances in exoplanet atmospheres.

Keywords: Hubble Space Telescope, Exoplanet atmospheres, Transmission spectroscopy
Planet Hunters TESS. V. A Planetary System Around a Binary Star, Including a Mini-Neptune in the Habitable Zone. We report on the discovery and validation of a transiting long-period mini-Neptune orbiting a bright (V = 9.0 mag) G dwarf (TOI 4633; R = 1.05 R ⊙, M = 1.10 M ⊙). The planet was identified in data from the Transiting Exoplanet Survey Satellite by citizen scientists taking part in the Planet Hunters TESS project. Modelling of the transit events yields an orbital period of 271.9445 ± 0.0040 days and radius of 3.2 ± 0.20 R ⊕. The Earth-like orbital period and an incident flux of   ${1.56}_{-0.16}^{+0.20}$   F ⊕ places it in the optimistic habitable zone around the star. Doppler spectroscopy of the system allowed us to place an upper mass limit on the transiting planet and revealed a non-transiting planet candidate in the system with a period of 34.15 ± 0.15 days. Furthermore, the combination of archival data dating back to 1905 with new high angular resolution imaging revealed a stellar companion orbiting the primary star with an orbital period of around 230 yr and an eccentricity of about 0.9. The long period of the transiting planet, combined with the high eccentricity and close approach of the companion star makes this a valuable system for testing the formation and stability of planets in binary systems.

Keywords: Exoplanet dynamics, Binary stars, Radial velocity, Exoplanet systems, Mini Neptunes, Transit photometry, Habitable zone
Foreground Dust Properties toward the Cluster NGC 7380. Using starlight polarization, we present the properties of foreground dust toward cluster NGC 7380 embedded in H II region Sh 2-142. Observations of starlight polarization are carried out in four filters using an imaging polarimeter equipped with a 104 cm ARIES telescope. Polarization vectors of stars are aligned along the Galactic magnetic field. Toward the east and southeast regions, the dust structure appears much denser than in other regions (inferred from extinction contours and a color composite image) and is also reflected in polarization distribution. We find that the polarization degree and extinction tend to increase with distance and indication for the presence of a dust layer at a distance of around 1.2 kpc. We have identified eight potential candidates exhibiting intrinsic polarization by employing three distinct criteria to distinguish between stars of intrinsic polarization and interstellar polarized stars. For interstellar polarized stars, we find that the maximum polarization degree increases with the color excess and has a strong scatter, with the mean value of 1.71% ± 0.57%. The peak wavelength spans 0.40–0.88 μm, with a mean value of 0.56 ± 0.07 μm, suggesting similar grain sizes in the region to those in the average diffuse interstellar medium. The polarization efficiency is also found to decrease with visual extinction as   ${P}_{\max }/{A}_{V}\propto {A}_{V}^{-0.61}$  . Our observational results are found to be consistent with the predictions by the radiative torque alignment theory.

Keywords: Interstellar dust, Open star clusters, Starlight polarization, Interstellar medium
The Death of Vulcan: NEID Reveals That the Planet Candidate Orbiting HD 26965 Is Stellar Activity. We revisit the long-studied radial velocity (RV) target HD 26965 using recent observations from the NASA-NSF "NEID" precision Doppler facility. Leveraging a suite of classical activity indicators, combined with line-by-line RV analyses, we demonstrate that the claimed 45-day signal previously identified as a planet candidate is most likely an activity-induced signal. Correlating the bulk (spectrally averaged) RV with canonical line activity indicators confirms a multiday "lag" between the observed activity indicator time series and the measured RV. When accounting for this lag, we show that much of the observed RV signal can be removed by a linear detrending of the data. Investigating activity at the line-by-line level, we find a depth-dependent correlation between individual line RVs and the bulk RVs, further indicative of periodic suppression of convective blueshift causing the observed RV variability, rather than an orbiting planet. We conclude that the combined evidence of the activity correlations and depth dependence is consistent with an RV signature dominated by a rotationally modulated activity signal at a period of ∼42 days. We hypothesize that this activity signature is due to a combination of spots and convective blueshift suppression. The tools applied in our analysis are broadly applicable to other stars and could help paint a more comprehensive picture of the manifestations of stellar activity in future Doppler RV surveys. * HD 26965 is also known as 40 Eridani A, which is the host star of the planet Vulcan in the Star Trek universe.

Keywords: Radial velocity
First Detection of Outflowing Gas in the Outskirts of the Broad-line Region in 1H 0707‑495. We use near-infrared spectroscopy covering simultaneously the zJHK bands to look for outflowing gas from the nuclear environment of 1H 0707‑495 taking advantage that this region is dominated by low-ionization broad-line region lines, most of them isolated. We detect broad components in H I, Fe II, and O I, at rest to the systemic velocity, displaying FWHM values of ∼500 km s‑1, consistent with its classification as a narrow-line Seyfert 1 active galactic nucleus. Moreover, most lines display a conspicuous blue-asymmetric profile, modeled using a blueshifted component, whose velocity shift reaches up to ∼826 km s‑1. This last feature can be interpreted in terms of outflowing gas already observed in X-ray and UV lines in 1H 0707‑495 but not detected before in the low-ionization lines. We discuss the relevance of our findings within the framework of the wind scenario already proposed for this source and suggest that the wind extends well into the narrow-line region owing to the observation of a blueshifted component in the forbidden line of [S III] λ9531. *Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia e Inovações do Brasil (MCTI/LNA), the US National Science Foundation's NOIRLab, the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).

Keywords: Galaxy spectroscopy, Seyfert galaxies, X-ray active galactic nuclei
A Search for Temporal Atmospheric Variability of Kepler Hot Jupiters. We perform a systematic search for atmospheric variability in short-period gas-giant planets (hot Jupiters) observed by the Kepler mission, by looking for temporal variability of their secondary eclipse depths. This is motivated by a recent detection of a decrease in the dayside brightness of KELT-1 b between TESS Sectors 17 and 57, separated by about 3 yr. We fit the Kepler light curves of 53 hot Jupiters and measure their secondary eclipse depths during individual Kepler quarters and four-quarter windows. We detect the secondary eclipses in individual quarters or four-quarter windows for 17 out of the 53 systems. In those 17 systems we do not detect statistically significant astrophysical variation in the secondary eclipse depths. We show that the data is sensitive to the variability seen for KELT-1 b in TESS data. Therefore, the absence of detected secondary eclipse variability in Kepler data suggests that the atmospheric variability in KELT-1 b is not common. In addition, several of the 53 targets we investigated display variability in their transit depths with a period of four quarters (1 yr). This instrumental signal is likely present in the light curves of other transiting planets we did not analyze and other variable stars observed by Kepler. Finally, we find that Kepler-488 b has a secondary eclipse depth that is unphysically large for a planet, and thus is likely a misclassified red dwarf.

Keywords: Exoplanets, Exoplanet atmospheric variability, Hot Jupiters
Investigating the Origins of Hot Neptunes from Radial Velocity Data. Hot Neptunes are extrasolar planets that are similar in size to Neptune in our solar system but are much closer to their host stars, completing an orbit in 10 days or less. The origin of hot Neptunes is not fully understood. A potential large third body at a distance can lead to the migration of long-period planets to become much closer to the host star, and such a dynamical process helps explain the origin of hot Jupiters. We investigate whether hot Neptunes could share a similar origin by analyzing radial velocity data from multiple sources for a sample of 34 hot Neptune systems. Hot Neptune systems appear to have similar values of linear trend to hot Jupiter systems. We perform a maximum likelihood analysis to constrain the mass and distance distribution of the putative third body. The overall fraction of hot Neptune systems with third bodies is consistent with unity, higher than 71% at the 2σ level. On average, the mass and distance distribution of the third bodies for hot Neptune systems is consistent with that for hot Jupiter systems. Our results suggest that hot-Neptune systems share the same origin mechanism as hot Jupiters, e.g., through the gravitational effect of third bodies.

Keywords: Exoplanet dynamics, Exoplanet evolution, Exoplanet formation, Exoplanet migration
Stellar Variability and Distance Indicators in the Near-infrared in Nearby Galaxies. I. RR Lyrae and Anomalous Cepheids in Draco Dwarf Spheroidal. The Draco Dwarf spheroidal (dSph) galaxy is one of the nearest and the most dark-matter-dominated satellites of the Milky Way. We obtained multiepoch near-infrared (NIR, JHK  s ) observations of the central region of Draco dSph covering a sky area of ∼21' × 21' using the WIRCam instrument at the 3.6 m Canada–France–Hawaii Telescope. Homogeneous JHK  s  time-series photometry for 212 RR Lyrae (173 fundamental-mode, 24 first-overtone, and 15 mixed-mode variables) and five Anomalous Cepheids in Draco dSph are presented and used to derive their period–luminosity relations at NIR wavelengths for the first-time. The small scatter of ∼0.05 mag in these empirical relations for RR Lyrae stars is consistent with those in globular clusters and suggests a very small metallicity spread, up to ∼0.2 dex, among these centrally located variables. Based on empirically calibrated NIR period–luminosity–metallicity relations for RR Lyrae in globular clusters, we determined a distance modulus to Draco dSph of μ RRL = 19.557 ± 0.026 mag. The calibrated K  s -band period–luminosity relations for Anomalous Cepheids in the Draco dSph and the Large Magellanic Cloud exhibit statistically consistent slopes but systematically different zero points, hinting at possible metallicity dependence of ∼ ‑ 0.3 mag dex‑1. Finally, the apparent magnitudes of the tip of the red-giant branch in I and J bands also agree well with their absolute calibrations with the adopted RR Lyrae distance to Draco. Our recommended ∼1.5% precise RR Lyrae distance, D Draco = 81.55 ± 0.98(statistical) ± 1.17(systematic) kpc, is the most accurate and precise distance to Draco dSph galaxy.

Keywords: RR Lyrae variable stars, Dwarf spheroidal galaxies, Anomalous Cepheid variable stars
Modeling Circumstellar Gas Emission around a White Dwarf Using CLOUDY. The chemical composition of an extrasolar planet is fundamental to its formation, evolution, and habitability. In this study, we explore a new way to measure the chemical composition of the building blocks of extrasolar planets by measuring the gas composition of the disrupted planetesimals around white dwarf stars. As a first attempt, we used the photoionization code CLOUDY to model the circumstellar gas emission around white dwarf Gaia J0611−6931 under some simplified assumptions. We found that most of the emission lines are saturated, and the line ratios approach the ratios of thermal emission; therefore, only lower limits to the number density can be derived. Silicon is the best-constrained element in the circumstellar gas, and we derived a lower limit of 1010.3 cm−3. In addition, we placed a lower limit on the total amount of gas to be 1.8 × 1019 g. Further study is needed to better constrain the parameters of the gas disk and connect it to other white dwarfs with circumstellar gas absorption.

Keywords: Extrasolar rocky planets, White dwarf stars, Chemical abundances, Planetesimals, Debris disks, Circumstellar gas