arXiv subjects

Jason D. Eastman

Publications and source records attributed to Jason D. Eastman.

110 records · Page 7Linked to original sources

arXiv2010

Discovery of a Low-Mass Companion to a Metal-Rich F Star with the MARVELS Pilot Project

We report the discovery of a low-mass companion orbiting the metal-rich, main sequence F star TYC 2949-00557-1 during the MARVELS (Multi-object APO Radial Velocity Exoplanet Large-area Survey) Pilot Project. The host star has an effective temperature T_eff = 6135 +/- 40 K, log(g) = 4.4 +/- 0.1 and [Fe/H] = 0.32 +/- 0.01, indicating a mass of M = 1.25 +/- 0.09 M_\odot and R = 1.15 +/- 0.15 R_\odot. The companion has an orbital period of 5.69449 +/- 0.00023 days and straddles the hydrogen burning limit with a minimum mass of 64 M_J, and may thus be an example of the rare class of brown dwarfs orbiting at distances comparable to those of "Hot Jupiters." We present relative photometry that demonstrates the host star is photometrically stable at the few millimagnitude level on time scales of hours to years, and rules out transits for a companion of radius greater than 0.8 R_J at the 95% confidence level. Tidal analysis of the system suggests that the star and companion are likely in a double synchronous state where both rotational and orbital synchronization have been achieved. This is the first low-mass companion detected with a multi-object, dispersed, fixed-delay interferometer.

astro-ph.SR↗

arXiv2005

Photometry of neglected open clusters in the First and Fourth Galactic Quadrants

CCD $BVI$ photometry is presented for 8 previously unstudied star clusters located in the First and Fourth Galactic Quadrants: AL~1, BH 150, NGC 5764, Lynga~9, Czernik~37, BH 261, Berkeley~80 and King~25. Color magnitude diagrams of the cluster regions suggest that several of them (BH 150, Lynga~9, Czernik~37 and BH 261 and King~25) are so embedded in the dense stellar population toward the galactic center that their properties, or even their existence as physical systems, cannot be confirmed. Lynga~9, BH 261 and King~25 appear to be slight enhancements of dense star fields, BH 150 is probably just a single bright star in a dense field, and Czernik~37 may be a sparse, but real cluster superimposed on the galactic bulge population. We derive preliminary estimates of the physical parameters for the remaining clusters. AL~1 appears to be an intermediate age cluster beyond the solar circle on the far side of the galaxy and the final two clusters, NGC 5764 and Berkeley 80 are also of intermediate age but located inside the solar ring. This set of clusters highlights the difficulties inherent in studying the stellar populations toward the inner regions of the galaxy.

astro-ph↗