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2017ApJ...839...48V - Astrophys. J., 839, 48-48 (2017/April-2)

Evidence for binarity and possible disk obscuration in Kepler observations of the pulsating RV Tau variable DF Cygni.


Abstract (from CDS):

The Kepler light curve of DF Cyg is unparalleled in precision and cadence for any RV Tau star to date, spanning a baseline of ∼4 years and clearly displaying the signature pulsating behavior of alternating deep and shallow minima as well as the long-term trend indicative of an RVb-type variable. We measure DF Cyg's formal period (the time interval between two successive deep minima) to be 49.84 ± 0.02 days. The trend in the arrival times emulates that of the long-term period. There appear to be precisely 16 deep+shallow minima cycles in one long-term cycle, suggesting a long-term cycle period of ≃795 ± 5 days. We argue that binarity may naturally explain the long-term periodicity in DF Cyg. The spectral energy distribution of DF Cyg features an infrared excess indicative of a disk possibly linked to a binary companion. From a recent Gaia parallax measurement for DF Cyg, we calculated that it has a distance of 990 ± 372 pc and a physical radius of R*=10.3±3.8R. From kinematics and geometric arguments, we argue that the most likely interpretation for the decrease in flux from the long-period maximum to the long-period minimum, as well as the reduction of the short-term pulsation amplitude, is caused by an occulting body such as a disk surrounding DF Cyg and its binary companion.

Abstract Copyright: © 2017. The American Astronomical Society. All rights reserved.

Journal keyword(s): binaries: general - circumstellar matter - stars: AGB and post-AGB - stars: individual: DF Cygni - stars: variables: Cepheids - stars: variables: Cepheids

Simbad objects: 8

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