A comprehensive investigation of the variable overcontact system EH Cancri
- PDF / 2,382,348 Bytes
- 24 Pages / 595.276 x 790.866 pts Page_size
- 11 Downloads / 179 Views
J. Astrophys. Astr. (2020) 41:26 https://doi.org/10.1007/s12036-020-09641-y
Sadhana(0123456789().,-volV)FT3](012345 6789().,-volV)
A comprehensive investigation of the variable overcontact system EH Cancri ´4 KEVIN B. ALTON1,* , ROBERT H. NELSON2,3 and KAZIMIERZ STE¸PIEN 1
UnderOak Observatory, 70 Summit Ave., Cedar Knolls, NJ, USA. Mountain Ash Observatory, 1393 Garvin Street, Prince George, BC V2M 3Z1, Canada. 3 Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics, National Research Council of Canada, Ottawa, Canada. 4 Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warsaw, Poland. E-mail: [email protected] 2
MS received 2 December 2019; accepted 16 June 2020 Abstract. Precise multi-color CCD-derived photometric data were obtained from EH Cnc at two sites during 2010, 2014 and 2018 wherein each epoch used a different instrument. This has provided a unique opportunity to investigate parameter uncertainty following Roche modeling of light curves optimized by differential corrections using the Wilson–Devinney code. Furthermore, new radial velocity data from EH Cnc presented in this study for the first time has produced absolute physical and geometric parameters for this A-subtype W UMa-type variable. Analysis of eclipse timing data confirms the presence of sinusoidallike excursions in the eclipse timing residuals. We address whether these are due to magnetic activity cycles, the so-called ‘‘Applegate effect’’, or related to a light-time effect (LiTE) resulting from the presence of a third gravitationally bound cool low mass white dwarf. A model using the PAdova & TRieste Stellar Evolution Code (PARSEC) has provided valuable insight about the evolutionary history of EH Cnc as a trinary system. Keywords. CCD photometry—Roche modeling—radial velocity spectroscopy—period analysis—lighttime effect—Applegate mechanism—Wilson–Devinney code.
1. Introduction The variability of EH Cancri was first discovered in photographic plates by Kulikovski (1934); later on, Shakhovski (1955) suggested that this system was a W UMa-type binary. EH Cnc was largely ignored until Figer et al. (1985) published photoelectricallyderived (B- and V-passbands) light curves (LCs) revealing an orbital period equal to 0:418034 0:000004 d. Since that time, the main body of published data has included visual and CCD-derived times-of-minimum (ToM) light which were used to assess potential secular changes in the orbital period. Results first reported by Yang et al. (2011) indicated that there was a secular decrease in orbital period (dP=dt ¼ 1:01 0:05 107 d yr1 ) with an underlying cyclic variation (P3 ’ 16:6 yr). Furthermore, based on V- and Rc -photometric data, Yang
et al. (2011) provided a Roche model LC solution which suggested that EH Cnc was a W-type overcontact system. This finding was based solely upon a photometric mass ratio (qph ¼ 2:51) derived using the so-called ‘‘q-search’’ strategy. Pitfalls associated with determining a photometric mass ratio from overcontact systems which do not exhibit a to
Data Loading...
