Ashley Chontos
A5053477601- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Space Exploration and Technology
- Astronomical and nuclear sciences
- Solar and Space Plasma Dynamics
- History and Developments in Astronomy
- Geophysics and Gravity Measurements
- Planetary Science and Exploration
- High-pressure geophysics and materials
- Scientific Research and Discoveries
- Atmospheric Ozone and Climate
- Spacecraft and Cryogenic Technologies
- Calibration and Measurement Techniques
- Spectroscopy and Laser Applications
- Archaeology and ancient environmental studies
- Historical Astronomy and Related Studies
- Semiconductor Lasers and Optical Devices
- Astrophysical Phenomena and Observations
- Geophysics and Sensor Technology
- Adaptive optics and wavefront sensing
University of Hawaii System
2018-2024
Princeton University
2022-2024
University of Hawaiʻi at Mānoa
2022-2024
Kavli Institute for Particle Astrophysics and Cosmology
2015
Stanford University
2015
We present 2,241 exoplanet candidates identified with data from the Transiting Exoplanet Survey Satellite (TESS) during its two-year prime mission. list these in TESS Objects of Interest (TOI) Catalog, which includes both new planet found by and previously-known planets recovered observations. describe process used to identify TOIs investigate characteristics candidates, discuss some notable discoveries. The TOI Catalog an unprecedented number small around nearby bright stars, are...
We present a high-precision radial velocity (RV) survey of 719 FGKM stars, which host 164 known exoplanets and 14 newly discovered or revised substellar companions. This catalog updated the orbital parameters long-period candidates, some have decades-longer observational baselines than they did upon initial detection. The range from warm sub-Neptunes super-Earths to cold gas giants. sample selection criteria, as well over 100,000 RV measurements, come Keck-HIRES, APF-Levy, Lick-Hamilton...
Abstract We used high-precision radial velocity measurements of FGKM stars to determine the occurrence giant planets as a function orbital separation spanning 0.03–30 au. Giant are more prevalent at distances 1–10 au compared orbits interior or exterior this range. The increase in planet ∼1 by factor ∼4 is highly statistically significant. A fall-off larger favored over models with flat increasing occurrence. measure <?CDATA ${14.1}_{-1.8}^{+2.0}$?> <mml:math...
We present the discovery of TOI-197.01, first transiting planet identified by Transiting Exoplanet Survey Satellite (TESS) for which asteroseismology host star is possible. TOI-197 (HIP116158) a bright (V=8.2 mag), spectroscopically classified subgiant oscillates with an average frequency about 430 muHz and displays clear signature mixed modes. The oscillation amplitude confirms that redder TESS bandpass compared to Kepler has small effect on oscillations, supporting expected yield thousands...
We use a high-precision radial velocity survey of FGKM stars to study the conditional occurrence two classes planets: close-in small planets (0.023--1 au, 2--30 Earth masses) and distant giant (0.23--10 30--6000 masses). find that $41^{+15}_{-13}\%$ systems with close-in, planet also host an outer giant, compared $17.6^{+2.4}_{-1.9}\%$ for irrespective presence. This implies hosts may be enhanced in all $1.7\sigma$ significance. Conversely, we estimate $42^{+17}_{-13}\%$ cold inner planet,...
Convergent disk migration has long been suspected to be responsible for forming planetary systems with a chain of mean-motion resonances (MMR). Dynamical evolution over time could disrupt the delicate resonant configuration. We present TOI-1136, 700-Myr-old G star hosting at least 6 transiting planets between $\sim$2 and 5 $R_\oplus$. The orbital period ratios deviate from exact commensurability by only $10^{-4}$, smaller than $\sim$\,$10^{-2}$ deviations seen in typical Kepler near-resonant...
Mass, radius, and age measurements of young (<100 Myr) planets have the power to shape our understanding planet formation. However, stars tend be extremely variable in both photometry radial velocity, which makes constraining these properties challenging. The V1298 Tau system four ~0.5 Rjup transiting a pre-main sequence star presents an important, if stress-inducing, opportunity directly observe measure infant planets. Su\'arez-Mascare\~no et al. (2021) published radial-velocity-derived...
Abstract NASA’s Transiting Exoplanet Survey Satellite (TESS) mission promises to improve our understanding of hot Jupiters by providing an all-sky, magnitude-limited sample transiting suitable for population studies. Assembling such a requires confirming hundreds planet candidates with additional follow-up observations. Here we present 20 that were detected using TESS data and confirmed be planets through photometric, spectroscopic, imaging observations coordinated the Follow-up Observing...
Abstract Despite the importance of Jupiter and Saturn to Earth’s formation habitability, there has not yet been a comprehensive observational study how giant exoplanets correlate with architectural properties close-in, sub-Neptune-sized exoplanets. This is largely because transit surveys are particularly insensitive planets at orbital separations ≳1 au, so their census Jupiter-like incomplete, inhibiting our relationship between small that do transit. To investigate distant, planets, we...
Abstract JWST has ushered in an era of unprecedented ability to characterize exoplanetary atmospheres. While there are over 5000 confirmed planets, more than 4000 Transiting Exoplanet Survey Satellite (TESS) planet candidates still unconfirmed and many the best planets for atmospheric characterization may remain be identified. We present a sample TESS that we identify as “best-in-class” transmission emission spectroscopy with JWST. These targets sorted into bins across equilibrium...
We present an analysis of the first 20-second cadence light curves obtained by TESS space telescope during its extended mission. find a precision improvement data compared to 2-minute for bright stars when binned same (~10-25% better T<~8 mag, reaching equal at T~13 mag), consistent with pre-flight expectations based on differences in cosmic ray mitigation algorithms. two results enabled this improvement. First, we use detect oscillations three solar analogs (gamma Pav, zeta Tuc and pi Men)...
Abstract LTT 1445 is a hierarchical triple M-dwarf star system located at distance of 6.86 pc. The primary 1445A (0.257 M ⊙ ) known to host the transiting planet 1445Ab with an orbital period 5.36 days, making it second-closest exoplanet system, and closest one for which dwarf. Using Transiting Exoplanet Survey Satellite data, we present discovery second in 3.12 days. We combine radial-velocity measurements obtained from five spectrographs, Echelle Spectrograph Rocky Exoplanets Stable...
Giant planets on short-period orbits are predicted to be inflated and eventually engulfed by their host stars. However, the detailed timescales stages of these processes not well known. Here we present discovery three hot Jupiters (P $<$ 10 d) orbiting evolved, intermediate-mass stars ($M_\star$ $\approx$ 1.5 M$_\odot$, 2 R$_\odot$ $R_\star < $ 5 R$_\odot$). By combining \tess photometry with ground-based radial velocity measurements, report masses radii for between 0.4 1.8 M$_\mathrm{J}$...
We present evidence of tidally-driven inspiral in the Kepler-1658 (KOI-4) system, which consists a giant planet (1.1$R_\mathrm{J}$, 5.9$M_\mathrm{J}$) orbiting an evolved host star (2.9$R_\odot$, 1.5$M_\odot$). Using transit timing measurements from Kepler, Palomar/WIRC, and TESS, we show that orbital period Kepler-1658b appears to be decreasing at rate $\dot{P} = 131_{-22}^{+20}$~ms~yr$^{-1}$, corresponding infall timescale $P/\dot{P}\approx2.5$~Myr. consider other explanations for data...
Abstract The Kepler and TESS missions have demonstrated that planets are ubiquitous. However, the success of these heavily depends on ground-based radial velocity (RV) surveys, which combined with transit photometry can yield bulk densities orbital properties. While most host stars too faint for detailed follow-up observations, is detecting orbiting nearby bright more amenable to RV characterization. Here, we introduce TESS-Keck Survey (TKS), an program using ∼100 nights Keck/HIRES study...
In this study, we performed a homogeneous analysis of the planets around FGK dwarf stars observed by Kepler and K2 missions, providing spectroscopic parameters for 310 targets -- including 239 Scaling hosts with Keck/HIRES. For orbital periods less than 40 days, found that distribution as function period, stellar effective temperature, metallicity was consistent between Kepler, reflecting planet formation efficiency across numerous ~1 kpc sight-lines in local Milky Way. Additionally,...
Abstract The consistently low activity level of the old solar analog 51 Peg not only facilitated discovery first hot Jupiter, but also led to suggestion that star could be experiencing a magnetic grand minimum. However, 50 yr time series showing minimal chromospheric variability associated with onset weakened braking (WMB), where sufficiently slow rotation disrupts cycling and production large-scale fields by stellar dynamo, thereby shrinking Alfvén radius inhibiting efficient loss angular...
Abstract The Transiting Exoplanet Survey Satellite (TESS) has discovered hundreds of new worlds, with TESS planet candidates now outnumbering the total number confirmed planets from Kepler. Owing to differences in survey design, continues provide that are better suited for subsequent follow-up studies, including mass measurement through radial velocity (RV) observations, compared Kepler targets. In this work, we present TESS-Keck Survey’s (TKS) Mass Catalog: a uniform analysis all TKS RV...
Abstract We present a radial velocity (RV) analysis of TOI-1136, bright Transiting Exoplanet Survey Satellite (TESS) system with six confirmed transiting planets, and seventh single-transiting planet candidate. All planets in the are amenable to transmission spectroscopy, making TOI-1136 one best targets for intra-system comparison exoplanet atmospheres. is young (∼700 Myr), exhibits transit timing variations (TTVs). The youth contributes high stellar variability on order 50 m s −1 , much...
Abstract The degree of alignment between a star’s spin axis and the orbital plane its planets (the stellar obliquity) is related to interesting poorly understood processes that occur during planet formation evolution. Hot Jupiters orbiting hot stars (≳6250 K) display wide range obliquities, while similar cool are preferentially aligned. Tidal dissipation expected be more rapid in with thick convective envelopes, potentially explaining this trend. Evolved provide an opportunity test damping...
We report the discovery of a warm sub-Saturn, TOI-257b (HD 19916b), based on data from NASA's Transiting Exoplanet Survey Satellite (TESS). The transit signal was detected by TESS and confirmed to be planetary origin radial velocity observations. An analysis photometry, Minerva-Australis, FEROS, HARPS velocities, asteroseismic stellar oscillations reveals that has mass $M_P=0.138\pm0.023$\,$\rm{M_J}$ ($43.9\pm7.3$\,$M_{\rm \oplus}$), radius $R_P=0.639\pm0.013$\,$\rm{R_J}$...
We report the discovery of TOI-561, a multi-planet system in galactic thick disk that contains rocky, ultra-short period planet (USP). This bright ($V=10.2$) star hosts three small transiting planets identified photometry from NASA TESS mission: TOI-561 b (TOI-561.02, P=0.44 days, $R_b = 1.45\pm0.11\,R_\oplus$), c (TOI-561.01, P=10.8 $R_c=2.90\pm0.13\,R_\oplus$), and d (TOI-561.03, P=16.3 $R_d=2.32\pm0.16\,R_\oplus$). The is chemically ([Fe/H]$=-0.41\pm0.05$, [$\alpha$/H]$=+0.23\pm0.05$)...
Abstract We measured the Rossiter–McLaughlin effect of WASP-107b during a single transit with Keck/HIRES. found sky-projected inclination WASP-107b’s orbit, relative to its host star’s rotation axis, be degrees. This confirms misaligned/polar orbit that was previously suggested from spot-crossing events and adds growing population hot Neptunes in polar orbits around cool stars. is also fourth such planet have known distant planetary companion. examined several dynamical pathways by which...
Abstract Exoplanet systems with multiple transiting planets are natural laboratories for testing planetary astrophysics. One such system is HD 191939 (TOI 1339), a bright ( V = 9) and Sun-like (G9V) star, which TESS found to host three (b, c, d). The have periods of 9, 29, 38 days each similar sizes from 3 3.4 R ⊕ . To further characterize the system, we measured radial velocity (RV) over 415 Keck/HIRES APF/Levy. We find that M b 10.4 ± 0.9 c 7.2 1.4 , low compared most known comparable...
We report the discovery of TOI-2180 b, a 2.8 $M_{\rm J}$ giant planet orbiting slightly evolved G5 host star. This transited only once in Cycle 2 primary Transiting Exoplanet Survey Satellite (TESS) mission. Citizen scientists identified 24 hr single-transit event shortly after data were released, allowing Doppler monitoring campaign with Automated Planet Finder telescope at Lick Observatory to begin promptly. The radial velocity observations refined orbital period b be 260.8$\pm$0.6 days,...