The First BVRcIc Precision Observations and Preliminary Photometric Analysis of the Near Contact TYC 1488-693-1

Volume 46 number 2 (2018)

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Ronald G. Samec

Faculty Research Associate, Pisgah Astronomical Research Institute, 1 PARI Drive, Rosman, NC 28772; ronaldsamec@gmail.com

Daniel B. Caton

Dark Sky Observatory, Appalachian State University, Department of Physics and Astronomy, 231 Garwood Hall, 525 Rivers Street, ASU Box 32106, Boone, NC 28608-2106

Danny R. Faulkner

Johnson Observatory, 1414 Bur Oak Court, Hebron, KY 41048

Robert Hill

Bob Jones University, 1700 Wade Hampton Boulevard, Greenville, SC 29614

Abstract

TYC 1488-693-1 is an ~F2 type (T ~ 6750 K) eclipsing binary. It was observed in April and May 2015 at Dark Sky Observatory in North Carolina with the 0.81-m reflector of Appalachian State University. Six times of minimum light were determined from our present observations, which include two primary eclipses and four secondary eclipses. In addition, six observations at minima were determined from archived NSVS Data. Improved linear and quadratic ephemerides were calculated from these times of minimum light which gave a possible period change of dP / dt = –5.2 (1.5) × 10^–6 d / yr. The period decrease may indicate that the binary is undergoing magnetic braking and is approaching a contact configuration due to the angular momentum loss. A BVRcIc simultaneous Wilson-Devinney (wd) Program solution indicates that the system has a mass ratio (q = M2 / M1) of ~0.58 (our solutions taken from q = 0.3 to 1.2 also indicate this is the value with the lowest sum of square residual), and a component temperature difference of ~2350 K. The large ΔT in the components verifies that the binary is not in contact. A binary maker fitted hot spot was maintained in the wd Synthetic Light Curve Computations. It remained on the larger component at the equator on the correct (following) side for a stream spot directed from the secondary component (as dictated by the Coriolis effect). This could indicate that the components are near filling their respective Roche Lobes. The fill-outs are nearly identical, 96% for the primary component and 95% for the secondary component. The inclination is ~79˚, which is not enough for the system to undergo a total eclipse. Caution is given for taking this solution as the definitive one.