Keivan G. Stassun

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The Transiting Exoplanet Survey Satellite (TESS) will search for planets transiting bright and nearby stars. TESS has been selected by NASA for launch in 2017 as an Astrophysics Explorer mission. The spacecraft will be placed into a highly elliptical 13.7-day orbit around the Earth. During its 2-year mission, TESS will employ four wide-field optical(More)
We characterize the star KOI 961, an M dwarf with transit signals indicative of three short-period exoplanets discovered by the Kepler mission. We proceed by comparing KOI 961 to Barnard’s Star, a nearby, well-characterized mid-M dwarf. We compare colors, optical and near-infrared spectra, and find remarkable agreement between the two, implying similar(More)
We present a statistical analysis of simultaneous optical and X-ray light curves, spanning 600 ks, for 814 pre–main-sequence (PMS) stars in the Orion Nebula Cluster. The aim of this study is to establish the relationship, if any, between the sites of optical and X-ray variability, and thereby to elucidate the origins of X-ray production in PMS stars. In a(More)
We 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, and luminosities for both components. The measured masses for the primary and secondary,(More)
We 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 (NGC2168; ∼ 150 Myr) and M34 (NGC1039; ∼ 250 Myr). The binary orbital parameters and the rotation periods of the primary stars were(More)
We present the Sloan Low-mass Wide Pairs of Kinematically Equivalent Stars (SLoWPoKES), a catalog of 1342 very-wide (projected separation & 500 AU), low-mass (at least one mid-K – mid-M dwarf component) common proper motion pairs identified from astrometry, photometry, and proper motions in the Sloan Digital Sky Survey. A Monte Carlo based Galactic model is(More)
We report the discovery of a pre-main-sequence (PMS), low-mass, doublelined, spectroscopic, eclipsing binary in the Orion star-forming region. We present our observations including radial velocities derived from optical high-resolution spectroscopy, and present an orbit solution that permits the determination of precise empirical masses for both components(More)
Close pre–main-sequence binary stars are expected to clear central holes in their protoplanetary disks, but the extent to which material can flow from the circumbinary disk across the gap onto the individual circumstellar disks has been unclear. In binaries with eccentric orbits, periodic perturbation of the outer disk is predicted to induce mass flow(More)
We reanalyze 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 X-rays in PMS stars by seeking out connections between the X-rays and the mechanisms most likely driving(More)
The 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 is hotter than its higher-mass companion represents a challenge to brown-dwarf evolutionary models, none of(More)