Site Map
Contacts
Follow us on Facebook Follow us on Twitter YouTube channel
Centro de Astrofísica da Universidade do Porto

Transit timing variations in WASP-10b induced by stellar activity

S. C. C. Barros, G. Boué, N. P. Gibson, D. Pollacco, A. Santerne, F. P. Keenan, I. Skillen, R. A. Street

Abstract
The hot-Jupiter WASP-10b was reported by Maciejewski et al. to show transit timing variations (TTVs) with an amplitude of ∼3.5 min. These authors proposed that the observed TTVs were caused by a 0.1MJup perturbing companion with an orbital period of ∼5.23 d, and hence, close to the outer 5:3 mean-motion resonance with WASP-10b. To test this scenario, we present eight new transit light curves of WASP-10b obtained with the Faulkes Telescope North and the Liverpool Telescope. The new light curves, together with 22 previously published ones, were modelled with a Markov Chain Monte Carlo transit fitting code. Transit depth differences reported for WASP-10b are thought to be due to starspot-induced brightness modulation of the host star. Assuming the star is brighter at the activity minimum, we favour a small planetary radius. We find Rp=1.039+0.0430.049RJup in agreement with Johnson et al. and Maciejewski et al. Recent studies find no evidence for a significant eccentricity in this system. We present consistent system parameters for a circular orbit and refine the orbital ephemeris of WASP-10b. Our homogeneously derived transit times do not support the previous claimed TTV signal, which was strongly dependent on two previously published transits that have been incorrectly normalized. Nevertheless, a linear ephemeris is not a statistically good fit to the transit times of WASP-10b. We show that the observed transit time variations are due to spot occultation features or systematics. We discuss and exemplify the effects of occultation spot features in the measured transit times and show that despite spot occultation during egress and ingress being difficult to distinguish in the transit light curves, they have a significant effect in the measured transit times. We conclude that if we account for spot features, the transit times of WASP-10b are consistent with a linear ephemeris with the exception of one transit (epoch 143) which is a partial transit. Therefore, there is currently no evidence for the existence of a companion to WASP-10b. Our results support the lack of TTVs of hot-Jupiters reported for the Kepler sample.

Keywords
techniques: photometric - time - stars: activity - stars: individual: WASP-10 - planetary systems - starspots

Monthly Notices of the Royal Astronomical Society
Volume 430, Page 3032
April 2013

>> ADS>> DOI

Institute of Astrophysics and Space Sciences

Institute of Astrophysics and Space Sciences (IA) is a new but long anticipated research infrastructure with a national dimension. It embodies a bold but feasible vision for the development of Astronomy, Astrophysics and Space Sciences in Portugal, taking full advantage and fully realizing the potential created by the national membership of the European Space Agency (ESA) and the European Southern Observatory (ESO). IA resulted from the merging the two most prominent research units in the field in Portugal: the Centre for Astrophysics of the University of Porto (CAUP) and the Center for Astronomy and Astrophysics of the University of Lisbon (CAAUL). It currently hosts more than two-thirds of all active researchers working in Space Sciences in Portugal, and is responsible for an even greater fraction of the national productivity in international ISI journals in the area of Space Sciences. This is the scientific area with the highest relative impact factor (1.65 times above the international average) and the field with the highest average number of citations per article for Portugal.

Proceed on CAUP's website|Go to IA website