A5063003507- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Geophysics and Gravity Measurements
- Solar and Space Plasma Dynamics
- Space Exploration and Technology
- Adaptive optics and wavefront sensing
- Spaceflight effects on biology
- Historical Astronomy and Related Studies
- CCD and CMOS Imaging Sensors
- Inertial Sensor and Navigation
- History and Developments in Astronomy
- Geomagnetism and Paleomagnetism Studies
- Scientific Research and Discoveries
- Electric Motor Design and Analysis
- Optical Systems and Laser Technology
- Galaxies: Formation, Evolution, Phenomena
- Engineering and Information Technology
- Multidisciplinary Science and Engineering Research
- Astronomical and nuclear sciences
- Advanced Data Storage Technologies
- Cloud Computing and Resource Management
Flatiron Health (United States)
2019-2024
Flatiron Institute
2019-2024
American Museum of Natural History
2019-2024
Columbia University
2017-2024
Computational Physics (United States)
2023
National Museum of American History
2021
Simons Foundation
2021
University of Oxford
2015-2016
Center for Astrophysics Harvard & Smithsonian
2015-2016
University of Southampton
2013
The growing field of large-scale time domain astronomy requires methods for probabilistic data analysis that are computationally tractable, even with large datasets. Gaussian Processes a popular class models used this purpose but, since the computational cost scales, in general, as cube number points, their application has been limited to small In paper, we present novel method Process modeling one-dimension where requirements scale linearly size dataset. We demonstrate by applying it...
Variability in the light curves of spotted, rotating stars is often non-sinusoidal and quasi-periodic – spots move on stellar surface have finite lifetimes, causing flux variations to slowly shift phase. A strictly periodic sinusoid therefore cannot accurately model a rotationally modulated curve. Physical models surfaces many drawbacks preventing effective inference, such as highly degenerate or high-dimensional parameter spaces. In this work, we test an appropriate model: Gaussian Process...
Among the available methods for dating stars, gyrochronology is a powerful one because it requires knowledge of only star's mass and rotation period. Gyrochronology relations have previously been calibrated using young clusters, with Sun providing age dependence, are therefore poorly at late ages. We used period measurements 310 Kepler stars asteroseismic ages, 50 from Hyades Coma Berenices clusters 6 field (including Sun) precise to calibrate relation, whilst fully accounting measurement...
Abstract The existence of high- α stars with inferred ages <6 Gyr has been confirmed recently large spectroscopic and photometric surveys. However, stellar mergers or binary interactions can induce properties associated young ages, such as high mass, rapid rotation, activity, even in old populations. Literature studies have that at least some these apparently are merger products. none ruled out the possibility genuinely stars. Because cool GKM dwarfs spin down, rotation be used to...
Recent measurements of rotation periods ($P_\text{rot}$) in the benchmark open clusters Praesepe (670 Myr), NGC 6811 (1 Gyr), and 752 (1.4 Gyr) demonstrate that, after converging onto a tight sequence slowly rotating stars mass$-$period space, temporarily stop spinning down. These data also show that duration this epoch stalled spin-down increases toward lower masses. To determine when resume down, we use from $K2$ mission Palomar Transient Factory to measure $P_\text{rot}$ for 58 dwarf...
The Large Synoptic Survey Telescope is designed to provide an unprecedented optical imaging dataset that will support investigations of our Solar System, Galaxy and Universe, across half the sky over ten years repeated observation. However, exactly how LSST observations be taken (the observing strategy or "cadence") not yet finalized. In this dynamically-evolving community white paper, we explore detailed performance anticipated science expected depend on small changes strategy. Using...
We present a new age-dating technique that combines gyrochronology with isochrone fitting to infer ages for FGKM main-sequence and subgiant field stars. Gyrochronology are each capable of providing relatively precise stars in certain areas the Hertzsprung-Russell diagram: works optimally cool stars, can provide near turnoff. Combined, these two techniques accurate broader range stellar masses evolutionary stages than either method used isolation. demonstrate position star on Hertzsprung-...
Abstract Gyrochronology, the field of age dating stars using mainly their rotation periods and masses, is ideal for inferring ages individual main-sequence stars. However, due to lack physical understanding complex magnetic fields in stars, gyrochronology relies heavily on empirical calibrations that require consistent reliable stellar measurements across a wide range masses. In this paper, we obtain sample gyro-kinematic age-dating method, technique calculate kinematics Using Gaussian...
We report the first planet discovery from two-wheeled Kepler (K2) mission: HIP 116454 b. The host star is a bright (V = 10.1, K 8.0) K1 dwarf with high proper motion and parallax-based distance of 55.2 ± 5.4 pc. Based on high-resolution optical spectroscopy, we find that metal-poor [Fe/H] =−0.16 0.08 has radius R⋆ 0.716 0.024 R☉ mass M⋆ 0.775 0.027 M☉. was observed by spacecraft during its Two-Wheeled Concept Engineering Test in 2014 February. During 9 days observations, K2 single transit...
In this work, we calibrate the relationship between Halpha emission and M dwarf ages. We compile a sample of 892 dwarfs with equivalent width (HaEW) measurements from literature that are either co-moving white known age (21 stars) or in young association (871 stars). identify 7 new candidate members associations. By dividing stars into active inactive categories according to their HaEW spectral type (SpT), find fraction decreases increasing age, form decline depends on SpT. Using compiled...
Abstract In this work we examine M dwarf rotation rates at a range of ages to establish benchmarks for gyrochronology. This includes sample 713 spectroscopically classified M0–M8 dwarfs with new measured from K2 light curves. We analyze data and recover 179 these objects. add members clusters known (5–700 Myr), as well objects assumed have field (≳1 Gyr). use Gaia DR2 parallax <?CDATA $(G\mbox{--}{G}_{\mathrm{RP}})$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"...
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 combine stellar surface rotation periods determined from NASA's Kepler mission with spectroscopic temperatures to demonstrate the existence of pileups at long-period and short-period edges temperature-period distribution for main-sequence stars exceeding $\sim 5500$K. The pileup is well-described by a curve constant Rossby number, critical value $\mathrm{Ro_{crit}} \lesssim 2$. was predicted van Saders et al. (2019) as consequence weakened magnetic braking, in which wind-driven angular...
Abstract The rotational evolution of cool dwarfs is poorly constrained after ∼1–2 Gyr due to a lack precise ages and rotation periods for old main-sequence stars. In this work, we use velocity dispersion as an age proxy reveal the temperature-dependent low-mass Kepler demonstrate that kinematic could be useful tool calibrating gyrochronology in future. We find linear model, calibrated fit period– <?CDATA ${T}_{\mathrm{eff}}$?> relationship Praesepe cluster, does not apply stars older than...
Abstract We analyze light curves of 284,834 unique K2 targets using a Gaussian process model with quasi-periodic kernel function. By cross-matching stars to observations from Gaia Data Release 2, we have identified 69,627 likely main-sequence stars. From these select subsample 8977 on the main sequence highly precise rotation period measurements. With this sample recover gap in period−color diagram first reported by McQuillan et al. While was tentatively detected Reinhold & Hekker, work...
Estimating stellar ages is important for advancing our understanding of and exoplanet evolution investigating the history Milky Way. However, low-mass stars are hard to infer as they evolve slowly on main sequence. In addition, empirical dating methods difficult calibrate faint. this work, we calculate Kepler F, G, crucially K M dwarfs, using their rotation kinematic properties. We apply simple assumption that velocity dispersion increases over time adopt an age--velocity--dispersion...
Abstract The majority of observed pixels on the Transiting Exoplanet Survey Satellite (TESS) are delivered in form full-frame images (FFIs). However, FFIs contain systematic effects such as pointing jitter and scattered light from Earth Moon that must be removed (i.e., “detrended”) before downstream analysis. We present unpopular , an open-source Python package to obtain detrended TESS FFI curves optimized for variable sources. implements a variant causal pixel model remove systematics...
Abstract The intermediate period gap, discovered by Kepler, is an observed dearth of stellar rotation periods in the temperature–period diagram at ∼20 days for G dwarfs and up to ∼30 early-M dwarfs. However, because Kepler mainly targeted solar-like stars, there a lack measured M dwarfs, especially those fully convective limit. Therefore it unclear if gap exists mid- late-M Here, we present catalog containing 40,553 (9535 >10 days), using Zwicky Transient Facility (ZTF). To measure these...
Abstract We measure the exoplanet occurrence rate as a function of isochrone and gyrochronology ages using confirmed candidate planets identified in Q1–17 DR25 Kepler data. employ Kepler's pipeline detection efficiency to correct for expected number each age bin. examine rates with radii 0.2 ≤ Rp 20 R ⊕ orbital periods P 100 days FGK stars between 1.5 8 Gyr inverse detection-efficiency method. find no significant trend stellar age; slight decreasing (within σ –2.5 ) only emerges low-mass...
The cool temperatures of M dwarf atmospheres enable complex molecular chemistry, making robust characterization compositions a long-standing challenge. Recent modifications to spectral synthesis pipelines have enabled more accurate modeling atmospheres, but these methods are too slow for characterizing than handful stars at time. Data-driven such as Cannon viable alternatives, and can harness the information content many dwarfs from large spectroscopic surveys. Here, we train on with FGK...
Abstract The cool temperatures of M dwarf atmospheres enable complex molecular chemistry, making robust characterization compositions a long-standing challenge. Recent modifications to spectral synthesis pipelines have enabled more accurate modeling atmospheres, but these methods are too slow for characterizing than handful stars at time. Data-driven such as Cannon viable alternatives, and can harness the information content many dwarfs from large spectroscopic surveys. Here, we train on...
Abstract The vast majority of Milky Way stellar halo stars were likely accreted from a small number (≲3) relatively large dwarf galaxy accretion events. However, the timing these events is poorly constrained and predominantly relies on indirect dynamical mixing arguments or imprecise age measurements associated with debris structures. Here, we aim to infer robust ages for galactic substructures more directly constrain merger history Galaxy. By combining kinematic, asteroseismic,...
Abstract While the population of confirmed exoplanets continues to grow, sample transiting planets around evolved stars is still limited. We present discovery and confirmation a hot Jupiter orbiting TOI-2184 (TIC 176956893), massive subgiant ( M ⋆ = 1.53 ± 0.12 ⊙ , R 2.90 0.14 ) in Transiting Exoplanet Survey Satellite (TESS) Southern Continuous Viewing Zone. The planet was flagged as false positive by TESS Quick-Look Pipeline due periodic systematics introducing spurious depth difference...