Qatar-1: indications for possible transit timing variations ^⋆

¹ Hamburger Sternwarte, University of Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
e-mail: cessen@hs.uni-hamburg.de
² Dept. of Astronomy, Box 351580, University of Washington, Seattle, WA 98195, USA

Received: 5 March 2013
Accepted: 22 May 2013

Abstract

Aims. Variations in the timing of transiting exoplanets provide a powerful tool for detecting additional planets in the system. Thus, the aim of this paper is to discuss the plausibility of transit timing variations (TTVs) on the Qatar-1 system by means of primary transit light curves analysis. Furthermore, we provide an interpretation of the timing variation.

Methods. We observed Qatar-1 between March 2011 and October 2012 using the 1.2 m OLT telescope in Germany and the 0.6 m PTST telescope in Spain. We present 26 primary transits of the hot Jupiter Qatar-1b. In total, our light curves cover a baseline of 18 months.

Results. We report on indications for possible long-term TTVs. Assuming that these TTVs are true, we present two different scenarios that could explain them. Our reported ~190 days TTV signal can be reproduced by either a weak perturber in resonance with Qatar-1b, or by a massive body in the brown dwarf regime. More observations and radial velocity monitoring are required to better constrain the perturber’s characteristics. We also refine the ephemeris of Qatar-1b, which we find to be T₀ = 2456157.42204 ± 0.0001 BJD_TDB and P = 1.4200246 ± 0.0000007 days, and improve the system orbital parameters.