The quest for companions to post-common envelope binaries

I. Searching a sample of stars from the CSS and SDSS

¹ Didaktik der Physik, Universität Duisburg-Essen, Universitätsstr. 2, 45117 Essen, Germany
² Leibniz-Gymnasium, Stankeitstr. 22, 45326 Essen, Germany
³ Institut für Astrophysik, Georg-August-Universität, Fr.-Hund-Platz 1, 37077 Göttingen, Germany
e-mail: beuermann@astro.physik.uni-goettingen.de
⁴ Max-Planck-Gymnasium, Theaterplatz 10, 37073 Göttingen, Germany
⁵ Don Bosco-Gymnasium, Theodor-Hartz-Straße 15, Essen, Germany
⁶ Evangelisches Gymnasium, Beckumer Str. 61, 59555 Lippstadt, Germany

Received: 15 September 2011
Accepted: 19 December 2011

Abstract

As part of an ongoing collaboration between student groups at high schools and professional astronomers, we have searched for the presence of circum-binary planets in a bona-fide unbiased sample of twelve post-common envelope binaries (PCEBs) from the Catalina Sky Survey (CSS) and the Sloan Digital Sky Survey (SDSS). Although the present ephemerides are significantly more accurate than previous ones, we find no clear evidence for orbital period variations between 2005 and 2011 or during the 2011 observing season. The sparse long-term coverage still permits O–C variations with a period of years and an amplitude of tens of seconds, as found in other systems. Our observations provide the basis for future inferences about the frequency with which planet-sized or brown-dwarf companions have either formed in these evolved systems or survived the common envelope (CE) phase.