EXOTIME: searching for planets around pulsating subdwarf B stars

Abstract

In 2007, a companion with planetary mass was found around the pulsating subdwarf B star V391 Pegasi with the timing method, indicating that a previously undiscovered population of substellar companions to apparently single subdwarf B stars might exist. Following this serendipitous discovery, the EXOTIME (http://www.na.astro.it/~silvotti/exotime/) monitoring program has been set up to follow the pulsations of a number of selected rapidly pulsating subdwarf B stars on time-scales of several years with two immediate observational goals: 1) determine Pdot of the pulsational periods P 2) search for signatures of substellar companions in O-C residuals due to periodic light travel time variations, which would be tracking the central star's companion-induced wobble around the center of mass. These sets of data should therefore at the same time: on the one hand be useful to provide extra constraints for classical asteroseismological exercises from the Pdot (comparison with "local" evolutionary models), and on the other hand allow to investigate the preceding evolution of a target in terms of possible "binary" evolution by extending the otherwise unsuccessful search for companions to potentially very low masses. While timing pulsations may be an observationally expensive method to search for companions, it samples a different range of orbital parameters, inaccessible through orbital photometric effects or the radial velocity method: the latter favours massive close-in companions, whereas the timing method becomes increasingly more sensitive towards wider separations. In this paper we report on the status of the on-going observations and coherence analysis for two of the currently five targets, revealing very well-behaved pulsational characteristics in HS 0444+0458, while showing HS 0702+6043 to be more complex than previously thought.

Contribution to: The Fourth Meeting on Hot Subdwarf Stars and Related Objects, 20 - 24 July 2009, Shanghai, China, published 03/2010 by Ap&SS (Open access publication). 12 pages, 14 figures, 5 tables

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Cited by in corpus (10)

• The Great Escape: How Exoplanets and Smaller Bodies Desert Dying Stars
• Connecting planets around horizontal branch stars with known exoplanets
• EXOTIME: searching for planets and measuring Pdot in sdB pulsators
• New Variable Hot Subdwarf Stars Identified from Anomalous Gaia Flux Errors, Observed by TESS, and Classified via Fourier Diagnostics
• Radial Velocity Confirmation of a Binary Detected from Pulse Timings
• Fortnightly Fluctuations in the O-C Diagram of CS 1246
• Planetary influences on photometric variation of the extreme helium subdwarf KIC10449976
• Pulsating stars harbouring planets
• The EXOTIME project: Signals in the $O-C$ diagrams of the rapidly pulsating subdwarfs DW Lyn, V1636 Ori, QQ Vir, and V541 Hya
• Acoustic and buoyancy modes throughout stellar evolution - Seismic properties of stars at different stellar ages and masses