Results for "Keivan G. Stassun"

total 105965took 0.28s
Evidence for a systematic offset of $-$0.25 mas in the Gaia DR1 parallaxes at $π\gtrsim 1$ masSep 17 2016Sep 21 2016We test the parallaxes reported in the Gaia first data release using the sample of eclipsing binaries with accurate, empirical distances from Stassun \& Torres (2016). We find a clear average offset of $-$0.25$\pm$0.05~mas in the sense of the Gaia parallaxes ... More
Temporal Evolution of Chromospheric Oscillations in Flaring Regions - A Pilot StudyMar 07 2018We have analyzed H-alpha intensity images obtained at a 1 minute cadence with the Global Oscillation Network Group (GONG) system to investigate the properties of oscillations in the 0-8 mHz frequency band at the location and time of strong M- and X-class ... More
Radius Inflation at Low Rossby Number in the Hyades ClusterNov 15 2018Jan 10 2019Radius inflation continues to be explored as a peculiar occurrence among magnetically active, low-mass stars. Recently Somers et. al. 2017 showed that radius inflation among low-mass stars in the young open cluster M45 (Pleiades Cluster) is correlated ... More
Filtergraph: An Interactive Web Application for Visualization of Astronomy DatasetsJul 15 2013Aug 27 2013Filtergraph is a web application being developed and maintained by the Vanderbilt Initiative in Data-intensive Astrophysics (VIDA) to flexibly and rapidly visualize a large variety of astronomy datasets of various formats and sizes. The user loads a flat-file ... More
Filtergraph: A Flexible Web Application for Instant Data Visualization of Astronomy DatasetsDec 18 2012Dec 20 2012Filtergraph is a web application being developed by the Vanderbilt Initiative in Data-intensive Astrophysics (VIDA) to flexibly handle a large variety of astronomy datasets. While current datasets at Vanderbilt are being used to search for eclipsing binaries ... More
Examining the relationships between colour, $T_{\rm eff}$, and [M/H] for APOGEE K and M dwarfsMay 12 2016We present the effective temperatures ($T_{\rm eff}$), metallicities, and colours in SDSS, 2MASS, and WISE filters, of a sample of 3834 late-K and early-M dwarfs selected from the Sloan Digital Sky Survey APOGEE spectroscopic survey ASPCAP catalog. We ... More
A Multi-color Optical Survey of the Orion Nebula Cluster. II. the H-R diagramAug 06 2010We present a new analysis of the stellar population of the Orion Nebula Cluster (ONC) based on multi-band optical photometry and spectroscopy. We study the color-color diagrams in BVI, plus a narrow-band filter centered at 6200A, finding evidences that ... More
Near-Infrared Emission Spectrum of WASP-103b using Hubble Space Telescope/Wide Field Camera 3Nov 28 2016Jan 10 2017We present here our observations and analysis of the dayside emission spectrum of the hot Jupiter WASP-103b. We observed WASP-103b during secondary eclipse using two visits of the Hubble Space Telescope with the G141 grism on Wide Field Camera 3 in spatial ... More
Radial Velocity Variations of Photometrically Quiet, Chromospherically Inactive Kepler Stars: A Link Between RV Jitter and Photometric FlickerOct 27 2013We compare stellar photometric variability, as measured from Kepler light curves by Basri et al. (2011), with measurements of radial velocity (RV) root-mean-square (RMS) variations of all California Planet Search overlap stars. We newly derive rotation ... More
Discovery of Resolved Magnetically Split Lines in SDSS/APOGEE Spectra of 157 Ap/Bp StarsMar 04 2019We report on magnetic field measurements of 157 chemically peculiar A/B stars (Ap/Bp) based on resolved, magnetically split absorption lines present in $H$-band spectra provided by the Sloan Digital Sky Survey (SDSS)/Apache Point Observatory Galactic ... More
Kepler-730: A hot Jupiter system with a close-in, transiting, Earth-sized planetDec 20 2018Jan 11 2019Kepler-730 is a planetary system hosting a statistically validated hot Jupiter in a 6.49-day orbit and an additional transiting candidate in a 2.85-day orbit. We use spectroscopic radial velocities from the APOGEE-2N instrument, Robo-AO contrast curves, ... More
A Low-Mass Exoplanet Candidate Detected By ${\it K2}$ Transiting the Praesepe M Dwarf JS 183Mar 29 2017We report the discovery of a repeating photometric signal from a low-mass member of the Praesepe open cluster that we interpret as a Neptune-sized transiting planet. The star is JS 183 (HSHJ 163, EPIC 211916756) with $T_{\rm eff} = 3325\pm100$ K, $M_{*} ... More
High-Resolution Spectroscopy during Eclipse of the Young Substellar Eclipsing Binary 2MASS 0535-0546. II. Secondary Spectrum: No Evidence that Spots Cause the Temperature ReversalAug 01 2012Aug 13 2012We present high-resolution optical spectra of the young brown-dwarf eclipsing binary 2M0535-05, obtained during eclipse of the higher-mass (primary) brown dwarf. Combined with our previous spectrum of the primary alone (Paper I), the new observations ... More
A Direct Measurement with Gaia of Radius Inflation in the Pleiades and its Relation to Rotation and Lithium DepletionSep 15 2016Sep 20 2016Boutique measurements of eclipsing binary parameters and statistical studies of young clusters have suggested that some magnetically active low-mass dwarfs possess radii inflated by $\sim$5-15% relative to theoretical expectations. If true, this effect ... More
Evidence for a systematic offset of -80 micro-arcseconds in the Gaia DR2 parallaxesMay 08 2018Jun 05 2018We reprise the analysis of Stassun & Torres (2016), comparing the parallaxes of the eclipsing binaries reported in that paper to the parallaxes newly reported in the Gaia second data release (DR2). We find evidence for a systematic offset of $-82 \pm ... More
Magnetic Accretion and Photopolarimetric Variability in Classical T Tauri StarsAug 24 1998We employ a Monte Carlo radiation transfer code to investigate the multi- wavelength photopolarimetric variability arising from a spotted T Tauri star surrounded by a dusty circumstellar disk. Our aim is to assess the ability of the magnetic accretion ... More
Angular Momentum Evolution of Young Stars: Toward a Synthesis of Observations, Theory, and ModelingMar 17 2003The aim of this AAS Topical Session was to update the community on the current state of knowledge about the angular momentum evolution of young stars. For newcomers to the subject, the session was intended to provide an introduction and general overview ... More
Evidence for a systematic offset of $-$0.25 mas in the Gaia DR1 parallaxesSep 17 2016Oct 13 2016We test the parallaxes reported in the Gaia first data release using the sample of eclipsing binaries with accurate, empirical distances from Stassun \& Torres (2016). We find an average offset of $-$0.25$\pm$0.05 mas in the sense of the Gaia parallaxes ... More
The canonical Luminous Blue Variable AG Car and its neighbor Hen 3-519 are much closer than previously assumedOct 20 2016The strong mass loss of Luminous Blue Variables (LBVs) is thought to play a critical role in the evolution of massive stars, but the physics of their instability and their place in the evolutionary sequence remains uncertain and debated. A key to understanding ... More
Eclipsing Binary Stars as Benchmarks for Trigonometric Parallaxes in the Gaia EraSep 08 2016We present fits to the broadband photometric spectral energy distributions (SEDs) of 158 eclipsing binaries (EBs) in the Tycho-2 catalog. These EBs were selected because they have highly precise stellar radii, effective temperatures, and in many cases ... More
A Multi-Color Optical Survey of the Orion Nebula Cluster. Part I: the CatalogJun 23 2009We present U, B, V, I broad-band, 6200A TiO medium-band and Halpha photometry of the Orion Nebula Cluster obtained with the WFI imager at the ESO/MPI 2.2 telescope. The nearly-simultaneous observations cover the entire ONC in a field of about 34x34 arcmin. ... More
Time-Series Photometry of Stars in and around the Lagoon Nebula. I. Rotation Periods of 290 Low-Mass Pre-Main-Sequence Stars in NGC 6530Dec 09 2011Dec 31 2011We have conducted a long-term, wide-field, high-cadence photometric monitoring survey of ~50,000 stars in the Lagoon Nebula \ion{H}{2} region. This first paper presents rotation periods for 290 low-mass stars in NGC 6530, the young cluster illuminating ... More
The First APOKASC Catalog of Kepler Dwarf and Subgiant StarsOct 18 2017Nov 02 2017(Abridged) We present the first APOKASC catalog of spectroscopic and asteroseismic data for 415 dwarfs and subgiants. Asteroseismic data have been obtained by Kepler in short cadence. The spectroscopic parameters are based on spectra taken as part of ... More
Characterizing the Cool KOIs III. KOI-961: A Small Star with Large Proper Motion and Three Small PlanetsJan 10 2012We present the characterization of the star KOI 961, an M dwarf with transit signals indicative of three short-period exoplanets, originally discovered by the Kepler Mission. We proceed by comparing KOI 961 to Barnard's Star, a nearby, well-characterized ... More
TESS full orbital phase curve of the WASP-18b systemNov 14 2018Mar 15 2019We present a visible-light full orbital phase curve of the transiting planet WASP-18b measured by the TESS Mission. The phase curve includes the transit, secondary eclipse, and sinusoidal modulations across the orbital phase shaped by the planet's atmospheric ... More
Expected Large Synoptic Survey Telescope (LSST) Yield of Eclipsing Binary StarsMay 30 2011In this paper we estimate the Large Synoptic Survey Telescope (LSST) yield of eclipsing binary stars, which will survey ~20,000 square degrees of the southern sky during the period of 10 years in 6 photometric passbands to r ~ 24.5. We generate a set ... More
The Scientific Context of WFIRST Microlensing in the 2020sMar 19 2019[abridged] WFIRST is uniquely capable of finding planets with masses as small as Mars at separations comparable to Jupiter, i.e., beyond the current ice lines of their stars. These planets fall between the close-in planets found by Kepler and the wide ... More
EPIC 246851721 b: A Tropical Jupiter Transiting a Rapidly Rotating Star in a Well-Aligned OrbitJul 26 2018Sep 27 2018We report the discovery of EPIC 246851721 b, a "tropical" Jupiter in a 6.18-day orbit around the bright ($V=11.439$) star EPIC 246851721 (TYC 1283-739-1). We present a detailed analysis of the system using $K2$ and ground-based photometry, radial velocities, ... More
Accurate Atmospheric Parameters at Moderate Resolution Using Spectral Indices: Preliminary Application to the MARVELS SurveyJul 02 2014Studies of Galactic chemical and dynamical evolution in the solar neighborhood depend on the availability of precise atmospheric parameters (Teff, [Fe/H] and log g) for solar-type stars. Many large-scale spectroscopic surveys operate at low to moderate ... More
Chemical Abundances of Main-Sequence, Turn-off, Subgiant and red giant Stars from APOGEE spectra I: Signatures of Diffusion in the Open Cluster M67Mar 12 2018Detailed chemical abundance distributions for fourteen elements are derived for eight high-probability stellar members of the solar metallicity old open cluster M67 with an age of $\sim$4 Gyr. The eight stars consist of four pairs, with each pair occupying ... More
"Auxiliary" Science with the WFIRST Microlensing SurveyMar 21 2019The Wide Field Infrared Survey Telescope (WFIRST) will monitor $\sim 2$ deg$^2$ toward the Galactic bulge in a wide ($\sim 1-2~\mu$m) W149 filter at 15-minute cadence with exposure times of $\sim$50s for 6 seasons of 72 days each, for a total $\sim$41,000 ... More
Opening the Treasure Chest: A Newborn Star Cluster Emerges from its Dust Pillar in CarinaNov 08 2004We present detailed observations of the Treasure Chest, a compact nebula at the head of a dust pillar in the southern Carina nebula. This object is of interest because it is an example of a dense young cluster containing at least one massive star, the ... More
The EB Factory Project. II. Validation with the Kepler Field in Preparation for K2 and TESSSep 10 2014Large repositories of high precision light curve data, such as the Kepler data set, provide the opportunity to identify astrophysically important eclipsing binary (EB) systems in large quantities. However, the rate of classical "by eye" human analysis ... More
A Compact Multi-Planet System With A Significantly Misaligned Ultra Short Period PlanetJun 21 2018Oct 29 2018We report the discovery of a compact multi-planet system orbiting the relatively nearby (78pc) and bright ($K=8.9$) K-star, K2-266 (EPIC248435473). We identify up to six possible planets orbiting K2-266 with estimated periods of P$_b$ = 0.66, P$_{.02}$ ... More
A Multi-Year Search For Transits Of Proxima Centauri. II: No Evidence For Transit Events With Periods Between 1-30 DaysJan 21 2019Using a global network of small telescopes, we have obtained light curves of Proxima Centauri at 329 observation epochs from 2006 to 2017. The planet Proxima b discovered by Anglada-Escude et al. (2016) with an orbital period of 11.186 d has an a priori ... More
MARVELS-1: A face-on double-lined binary star masquerading as a resonant planetary system; and consideration of rare false positives in radial velocity planet searchesMay 01 2013Oct 21 2013We have analyzed new and previously published radial velocity observations of MARVELS-1, known to have an ostensibly substellar companion in a ~6- day orbit. We find significant (~100 m/s) residuals to the best-fit model for the companion, and these residuals ... More
Exploring the Brown Dwarf Desert: New Substellar Companions from the SDSS-III MARVELS SurveyFeb 06 2017Planet searches using the radial velocity technique show a paucity of companions to solar-type stars within ~5 AU in the mass range of ~10 - 80 M$_{\text{Jup}}$. This deficit, known as the brown dwarf desert, currently has no conclusive explanation. New ... More
Sodium and Oxygen Abundances in the Open Cluster NGC 6791 from APOGEE H-Band SpectroscopyNov 07 2014The open cluster NGC 6791 is among the oldest, most massive and metal-rich open clusters in the Galaxy. High-resolution $H$-band spectra from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) of 11 red giants in NGC 6791 are analyzed ... More
Transiting Planets with LSST I: Potential for LSST Exoplanet DetectionAug 11 2014Oct 24 2014The Large Synoptic Survey Telescope (LSST) has been designed in order to satisfy several different scientific objectives that can be addressed by a ten-year synoptic sky survey. However, LSST will also provide a large amount of data that can then be exploited ... More
An observational correlation between stellar brightness variations and surface gravityAug 21 2013Surface gravity is one of a star's basic properties, but it is difficult to measure accurately, with typical uncertainties of 25-50 per cent if measured spectroscopically and 90-150 per cent photometrically. Asteroseismology measures gravity with an uncertainty ... More
The Impact of Chromospheric Activity on Observed Initial Mass FunctionsOct 18 2014Oct 21 2014Using recently established empirical calibrations for the impact of chromospheric activity on the radii, effective temperatures, and estimated masses of active low-mass stars and brown dwarfs, we reassess the shape of the initial mass function (IMF) across ... More
Transit Timing Variation Measurements of WASP-12b and Qatar-1b: No Evidence for Additional PlanetsDec 01 2015Aug 23 2016WASP-12b and Qatar-1b are transiting Hot Jupiters for which previous works have suggested the presence of transit timing variations (TTVs) indicative of additional bodies in these systems - an Earth-mass planet in WASP-12 and a brown-dwarf mass object ... More
Spectral Energy Distributions of Young Stars in IC 348: The Role of Disks in Angular Momentum Evolution of Young, Low-Mass StarsJun 07 2011Jun 14 2011Theoretical work suggests that a young star's angular momentum and rotation rate may be strongly influenced by magnetic interactions with its circumstellar disk. A generic prediction of these 'disk-locking' (DL) theories is that a disk-locked star will ... More
Circumstellar Environment and Effective Temperature of the Young Substellar Eclipsing Binary 2MASS J05352184-0546085Mar 11 2009We present new Spitzer IRAC/PU/MIPS photometry from 3.6 to 24 um, and new Gemini GMOS photometry at 0.48 um, of the young brown dwarf eclipsing binary 2MASS J05352184-0546085, located in the Orion Nebula Cluster. No excess disk emission is detected: The ... More
TOI-150: A transiting hot Jupiter in the TESS southern CVZFeb 26 2019We report the detection of a hot Jupiter ($M_{p}=1.72\pm0.09\ M_{J}$, $R_{p}=1.38\pm0.04\ R_{J}$) orbiting a middle-aged star ($\log g=4.152^{+0.030}_{-0.043}$) in the TESS southern continuous viewing zone ($\beta=-79.59^{\circ}$). We confirm the planetary ... More
AstroImageJ: Image Processing and Photometric Extraction for Ultra-Precise Astronomical Light CurvesJan 11 2016ImageJ is a graphical user interface (GUI) driven, public domain, Java-based, software package for general image processing traditionally used mainly in life sciences fields. The image processing capabilities of ImageJ are useful and extendable to other ... More
Larger Planet Radii Inferred from Stellar "Flicker" Brightness Variations of Bright Planet Host StarsMay 05 2014Most extrasolar planets have been detected by their influence on their parent star, typically either gravitationally (the Doppler method) or by the small dip in brightness as the planet blocks a portion of the star (the transit method). Therefore, the ... More
Gaia Assorted Mass Binaries Long Excluded from SLoWPoKES (GAMBLES): Identifying Wide Binary Pairs with Components of Diverse MassNov 23 2016Nov 27 2016Despite the maturity of stellar astrophysics, the formation and evolution of binary star systems still remain key questions in modern astronomy. Wide binary pairs (separations >10^3 AU) are particularly intriguing because their low binding energies makes ... More
Gaia Assorted Mass Binaries Long Excluded from SLoWPoKES (GAMBLES): Identifying Wide Binary Pairs with Components of Diverse MassNov 23 2016Despite the maturity of stellar astrophysics, the formation and evolution of binary star systems still remain key questions in modern astronomy. Wide binary pairs (separations >10^3 AU) are particularly intriguing because their low binding energies makes ... More
A Search for Star-Disk Interaction Among the Strongest X-ray Flaring Stars in the Orion Nebula ClusterMay 12 2010The Chandra Orion Ultradeep Project observed hundreds of young, low-mass stars undergoing highly energetic X-ray flare events. The 32 most powerful cases have been modeled with the result that the magnetic structures responsible for these flares can be ... More
Stellar Rotation in M35: Mass-Period Relations, Spin-Down Rates, and GyrochronologyMay 07 2008Nov 26 2008We present the results of a 5 month photometric time-series survey for stellar rotation over a 40'x40' field on the 150 Myr open cluster M35. We report rotation periods for 441 stars and determine their cluster membership and binarity based on a decade-long ... More
An Observational Study of Tidal Synchronization in Solar-Type Binary Stars in the Open Clusters M35 and M34Aug 07 2006We present rotation periods for the solar-type primary stars in 13 close (a~< 5 AU) single-lined spectroscopic binaries with known orbital periods (P) and eccentricities (e). All binaries are members of the open clusters M35 (150Myr) and M34 (250Myr). ... More
Accurate, Empirical Radii and Masses of Planets with Gaia ParallaxesSep 14 2016Sep 15 2016We present new, empirical measurements of the radii of 132 stars that host transiting planets. These stellar radii are determined using only direct observables---the bolometric flux at Earth, the stellar effective temperature, and the parallax newly provided ... More
A Granulation "Flicker"-based Measure of Stellar Surface GravityDec 10 2015In Bastien et al. (2013) we found that high quality light curves, such as those obtained by Kepler, may be used to measure stellar surface gravity via granulation-driven light curve "flicker". Here, we update and extend the relation originally presented ... More
Observations of the M82 SN 2014J with the Kilodegree Extremely Little TelescopeNov 15 2014We report observations of the bright M82 supernova 2014J serendipitously obtained with the Kilodegree Extremely Little Telescope (KELT). The SN was observed at high cadence for over 100 days, from pre-explosion, to early rise and peak times, through the ... More
Empirical Tests of Pre-Main-Sequence Stellar Evolution Models with Eclipsing BinariesJun 15 2014We examine the performance of standard PMS stellar evolution models against the accurately measured properties of a benchmark sample of 26 PMS stars in 13 EB systems. We provide a definitive compilation of all fundamental properties for the EBs. We also ... More
High Cadence Time-Series Photometry of V1647 OrionisAug 27 2011We present high cadence (1-10 hr^-1) time-series photometry of the eruptive young variable star V1647 Orionis during its 2003-2004 and 2008-2009 outbursts. The 2003 light curve was obtained mid-outburst at the phase of steepest luminosity increase of ... More
First Results from the Disk Eclipse Search with KELT (DESK) SurveySep 14 2015Using time-series photometry from the Kilodegree Extremely Little Telescope (KELT) exoplanet survey, we are looking for eclipses of stars by their protoplanetary disks, specifically in young stellar associations. To date, we have discovered two previously ... More
High Resolution Spectroscopy during Eclipse of the Young Substellar Eclipsing Binary 2MASS 0535-0546. I. Primary Spectrum: Cool Spots versus Opacity UncertaintiesAug 13 2010We present high-resolution Keck optical spectra of the very young substellar eclipsing binary 2MASS J05352184-0546085, obtained during eclipse of the lower-mass (secondary) brown dwarf. The observations yield the spectrum of the higher-mass (primary) ... More
Eclipsing Binary Stars as Tests of Stellar Evolutionary Models and Stellar AgesFeb 16 2009Eclipsing binary stars provide highly accurate measurements of the fundamental physical properties of stars. They therefore serve as stringent tests of the predictions of evolutionary models upon which most stellar age determinations are based. Models ... More
A Surprising Reversal of Temperatures in the Brown-Dwarf Eclipsing Binary 2MASS J05352184-0546085Apr 24 2007The newly discovered brown-dwarf eclipsing binary 2MASS J05352184-0546085 provides a unique laboratory for testing the predictions of theoretical models of brown-dwarf formation and evolution. The finding that the lower-mass brown dwarf in this system ... More
Reanalysis of the Radii of the Benchmark Eclipsing Binary V578 MonApr 04 2013V578 Mon is an eclipsing binary system in which both stars have masses above 10 Msun determined with an accuracy better than 3%. It is one of only five such massive eclipsing binaries known that also possess eccentric orbits and measured apsidal motions, ... More
Eclipsing Binary Science Via the Merging of Transit and Doppler Exoplanet Survey Data - A Case Study With the MARVELS Pilot Project and SuperWASPMay 10 2011Exoplanet transit and Doppler surveys discover many binary stars during their operation that can be used to conduct a variety of ancillary science. Specifically, eclipsing binary stars can be used to study the stellar mass-radius relationship and to test ... More
The Mysterious Dimmings of the T Tauri Star V1334 TauJan 11 2017Jan 30 2017We present the discovery of two extended $\sim$0.12 mag dimming events of the weak-lined T-Tauri star V1334. The start of the first event was missed but came to an end in late 2003, and the second began in February 2009, and continues as of November 2016. ... More
KELT-11b: A Highly Inflated Sub-Saturn Exoplanet Transiting the V=8 Subgiant HD 93396Jul 06 2016We report the discovery of a transiting exoplanet, KELT-11b, orbiting the bright ($V=8.0$) subgiant HD 93396. A global analysis of the system shows that the host star is an evolved subgiant star with $T_{\rm eff} = 5370\pm51$ K, $M_{*} = 1.438_{-0.052}^{+0.061} ... More
Randomized Caching in Cooperative UAV-Enabled Fog-RANFeb 22 2019We consider an unmanned aerial vehicle enabled (UAV-enabled) fog-radio access network (F-RAN) in which UAVs are considered as flying remote radio heads (RRH) equipped with caching and cooperative communications capabilities. We are mainly focus on probabilistic/randomized ... More
Coverage Performance of Aerial-Terrestrial HetNetsFeb 22 2019Providing seamless coverage under current cellular network technologies is surmountable only through gross overengineering. Alternatively, as an economically effective solution, the use of unmanned aerial vehicles (UAVs), augmented with the functionalities ... More
A Framework for Prioritizing the TESS Planetary Candidates Most Amenable to Atmospheric CharacterizationMay 09 2018Sep 14 2018A key legacy of the recently launched TESS mission will be to provide the astronomical community with many of the best transiting exoplanet targets for atmospheric characterization. However, time is of the essence to take full advantage of this opportunity. ... More
How Do Non-Ideal UAV Antennas Affect Air-to-Ground Communications?Feb 22 2019Analysis of the performance of Unmanned Aerial Vehicle (UAV)-enabled communications systems often relies upon idealized antenna characteristic, where the side-lobe gain of UAVs' antenna is ignored. In practice, however, side-lobe cause inevitable interference ... More
The Second APOKASC Catalog: The Empirical ApproachApr 26 2018We present a catalog of stellar properties for a large sample of 6676 evolved stars with APOGEE spectroscopic parameters and \textit{Kepler} asteroseismic data analyzed using five independent techniques. Our data includes evolutionary state, surface gravity, ... More
Community structure detection and evaluation during the pre- and post-ictal hippocampal depth recordingsMar 14 2018May 31 2018Detecting and evaluating regions of brain under various circumstances is one of the most interesting topics in computational neuroscience. However, the majority of the studies on detecting communities of a functional connectivity network of the brain ... More
Estimating Stellar Radial Velocity Variability from Kepler and GALEX: Implications for the Radial Velocity Confirmation of ExoplanetsNov 13 2013We cross-match the GALEX and Kepler surveys to create a unique dataset with both ultraviolet (UV) measurements and highly precise photometric variability measurements in the visible light spectrum. As stellar activity is driven by magnetic field modulations, ... More
Transiting Planets with LSST II. Period Detection of Planets Orbiting 1 Solar Mass HostsFeb 28 2015Jul 23 2015The Large Synoptic Survey Telescope (LSST) will photometrically monitor approximately 1 billion stars for ten years. The resulting light curves can be used to detect transiting exoplanets. In particular, as demonstrated by Lund et al. (2015), LSST will ... More
New BVIc Photometry of Low-mass Pleiades Stars: Exploring the Effects of Rotation on Broadband ColorsJul 01 2014We present new BVIc photometry for 350 Pleiades proper-motion members with 9 < V < 17. Importantly, our new catalog includes a large number of K and early-M type stars, roughly doubling the number of low-mass stars with well calibrated Johnson/Cousins ... More
Resolved Spectroscopy of M Dwarf/L Dwarf Binaries. IV. Discovery of an M9 + L6 BInary Separated by Over 100 AUOct 06 2010Oct 11 2010We report the discovery of a faint L6 \pm 1 companion to the previously known M9 dwarf, 2MASS J01303563-4445411, based on our near-infrared imaging and spectroscopic observations with the 3m Infrared Telescope Facility SpeX imager/spectrometer. The visual ... More
A Cautionary Tale: MARVELS Brown Dwarf Candidate Reveals Itself To Be A Very Long Period, Highly Eccentric Spectroscopic Stellar BinaryJun 13 2013We report the discovery of a highly eccentric, double-lined spectroscopic binary star system (TYC 3010-1494-1), comprising two solar-type stars that we had initially identified as a single star with a brown dwarf companion. At the moderate resolving power ... More
MARVELS-1b: A Short-Period, Brown Dwarf Desert Candidate from the SDSS-III MARVELS Planet SearchNov 23 2010We present a new short-period brown dwarf candidate around the star TYC 1240-00945-1. This candidate was discovered in the first year of the Multi-object APO Radial Velocity Exoplanets Large-area Survey (MARVELS), which is part of the third phase of the ... More
An Empirical Correction for Activity Effects on the Temperatures, Radii, and Estimated Masses of Low-Mass Stars and Brown DwarfsJun 21 2012Jul 17 2012We present empirical relations for determining the amount by which the effective temperatures and radii -- and therefore the estimated masses -- of low-mass stars and brown dwarfs are altered due to chromospheric activity. We base our relations on a large ... More
The Initial Mass Function of the Orion Nebula Cluster across the H-burning limitDec 12 2011We present a new census of the Orion Nebula Cluster (ONC) over a large field of view (>30'x30'), significantly increasing the known population of stellar and substellar cluster members with precisely determined properties. We develop and exploit a technique ... More
A statistical analysis of the accuracy of the digitized magnitudes of photometric plates on the time scale of decades with an application to the century-long light curve of KIC 8462852Jan 27 2016Apr 28 2016We present a statistical analysis of the accuracy of the digitized magnitudes of photometric plates on the time scale of decades. In our examination of archival Johnson B photometry from the Harvard DASCH archive, we find a median RMS scatter of lightcurves ... More
The Stability of F-star Brightness on Century TimescalesMay 09 2016The century-long photometric record of the DASCH project provides a unique window into the variability of stars normally considered to be photometrically inactive. In this paper, we look for long-term trends in the brightness of F stars, with particular ... More
A Strict Test of Stellar Evolution Models: The Absolute Dimensions of Massive Benchmark Eclipsing Binary V578 MonMay 04 2014We determine the absolute dimensions of the eclipsing binary V578 Mon, a detached system of two early B-type stars (B0V + B1V, P$=$2.40848 d) in the star-forming region NGC 2244 of the Rosette Nebula. From the light curve analysis of 40 yr of photometry ... More
Stellar Granulation as the Source of High-Frequency Flicker in Kepler Light CurvesDec 20 2013A large fraction of cool, low-mass stars exhibit brightness fluctuations that arise from a combination of convective granulation, acoustic oscillations, magnetic activity, and stellar rotation. Much of the short-timescale variability takes the form of ... More
Apsidal Motion of the Massive, Benchmark Eclipsing Binary V578 MonMay 06 2011May 11 2011V578 Mon is a system of two early B-type stars in the Rosette Nebula star-forming region (NGC 2244), and is one of only nine eclipsing binaries with component masses greater than 10 M\odot whose physical parameters have been determined with an accuracy ... More
Solar Flares and Coronal Mass Ejections: A Statistically Determined Flare Flux-CME Mass CorrelationNov 01 2010In an effort to examine the relationship between flare flux and corresponding CME mass, we temporally and spatially correlate all X-ray flares and CMEs in the LASCO and GOES archives from 1996 to 2006. We cross-reference 6,733 CMEs having well-measured ... More
The Color-Period Diagram and Stellar Rotational Evolution - New Rotation Period Measurements in the Open Cluster M34Mar 26 2011Mar 29 2011We present results from a 5-month photometric survey for stellar rotation periods combined with a 4-year radial-velocity survey for membership and binarity in the 220Myr open cluster M34. We report surface rotation periods for 120 stars, 83 of which are ... More
Detailed Abundances of Planet-Hosting Wide Binaries. II. HD80606 + HD80607Dec 31 2015We present a detailed chemical abundance analysis of 15 elements in the planet-hosting wide binary system HD80606 + HD80607 using Keck/HIRES spectra. As in our previous analysis of the planet-hosting wide binary HD20782 + HD20781, we presume that these ... More
The SLoWPoKES Catalog of Low-mass Ultra-wide Binaries: A Cool Stars Resource for Testing Fundamental Properties and for Constraining Binary Formation TheorySep 11 2012We present results from the Sloan Low-mass Wide Pairs of Kinematically Equivalent Stars (SLoWPoKES) catalog of ultra-wide (10^3-10^5.5 AU), low-mass (K5-M7) common proper motion binaries. We constructed a Galactic model, based on empirical stellar number ... More
The High-Order-Multiplicity of Unusually Wide M-dwarf Binaries: Eleven New Triple and Quadruple SystemsJul 21 2010M-dwarfs in extremely wide binary systems are very rare, and may thus have different formation processes from those found as single stars or close binaries in the field. In this paper we search for close companions to a new sample of 36 extremely wide ... More
Correcting for Activity Effects on the Temperatures, Radii, and Estimated Masses of Low-Mass Stars and Brown DwarfsSep 08 2012We present empirical relations for determining the amount by which the effective temperatures and radii---and therefore the estimated masses---of low-mass stars and brown dwarfs are altered due to chromospheric activity. Accurate estimates of stellar ... More
A Survey for a Coeval, Comoving Group Associated with HD 141569Sep 19 2008We present results of a search for a young stellar moving group associated with the star HD 141569, a nearby, isolated Herbig AeBe primary member of a 5+/-3 Myr-old triple star system on the outskirts of the Sco-Cen complex. Our spectroscopic survey identified ... More
Dynamical Mass Constraints on Low-Mass Pre-Main-Sequence Stellar Evolutionary Tracks: An Eclipsing Binary in Orion with a 1.0 Msun Primary and an 0.7 Msun SecondaryDec 22 2003We report the discovery of a double-lined, spectroscopic, eclipsing binary in the Orion star-forming region. We analyze the system spectroscopically and photometrically to empirically determine precise, distance-independent masses, radii, effective temperatures, ... More
A 10-micron Search for Inner-Truncated Disks Among Pre-Main-Sequence Stars With Photometric Rotation PeriodsOct 31 2000We use mid-IR (primarily 10 $\mu$m) photometry as a diagnostic for the presence of disks with inner cavities among 32 pre-main sequence stars in Orion and Taurus-Auriga for which rotation periods are known and which do not show evidence for inner disks ... More
Evidence for Binarity and Possible Disk Obscuration in Kepler Observations of the Pulsating RV Tau Variable DF CygniMar 24 2017Apr 14 2017The Kepler light curve of DF Cyg is unparalleled in precision and cadence for any RV Tau star to date spanning a baseline of $\sim$4 years and clearly displaying the signature pulsating behavior of alternating deep and shallow minima as well as the long-term ... More
KELT-22Ab: A Massive Hot Jupiter Transiting a Near Solar TwinMar 20 2018We present the discovery of KELT-22Ab, a hot Jupiter from the KELT-South survey. KELT-22Ab transits the moderately bright ($V\sim 11.1$) Sun-like G2V star TYC 7518-468-1. The planet has an orbital period of $P = 1.3866529 \pm 0.0000027 $ days, a radius ... More
A Simultaneous Optical and X-ray Variability Study of the Orion Nebula Cluster. I. Incidence of Time-Correlated X-ray/Optical VariationsJun 04 2006We present a database of $BVRI$ time-series photometry of the Orion Nebula Cluster obtained with two ground-based telescopes at different longitudes to provide simultaneous coverage with the 13-d Chandra observation of the cluster. The resulting database ... More
Metrics for Optimization of Large Synoptic Survey Telescope Observations of Stellar Variables and TransientsAug 13 2015Aug 17 2015The Large Synoptic Survey Telescope (LSST) will be the largest time-domain photometric survey ever. In order to maximize the LSST science yield for a broad array of transient stellar phenomena, it is necessary to optimize the survey cadence, coverage, ... More
An Improved Determination of the Lithium Depletion Boundary Age of Blanco 1 and a First Look on the Effects of Magnetic ActivitySep 17 2014Sep 23 2014The Lithium Depletion Boundary (LDB) is a robust method for accurately determining the ages of young clusters, but most pre-main-sequence models used to derive LDB ages do not include the effects of magnetic activity on stellar properties. In light of ... More
Constraining Explosion Type of Young Supernova Remnants Using 24 Micron Emission MorphologyJun 14 2013Determination of the explosion type of supernova remnants (SNRs) can be challenging, as SNRs are hundreds to thousands of years old and supernovae (SNe) are classified based on spectral properties days after explosion. Previous studies of thermal X-ray ... More
X-ray Properties of Pre--Main-Sequence Stars in the Orion Nebula Cluster with Known Rotation PeriodsMar 05 2004We re-analyze all archival Chandra/ACIS observations of the Orion Nebula Cluster (ONC) to study the X-ray properties of a large sample of pre--main-sequence (PMS) stars with optically determined rotation periods. Our goal is to elucidate the origins of ... More