Ground-based transit observations of the HAT-P-18, HAT-P-19, HAT-P-27/WASP-40 and WASP-21 systems

Ground-based transit observations of the HAT-P-18, HAT-P-19, HAT-P-27/WASP-40 and WASP-21 systems

Authors:

Seeliger et al

Abstract:

As part of our ongoing effort to investigate transit timing variations (TTVs) of known exoplanets, we monitored transits of the four exoplanets HAT-P-18b, HAT-P-19b, HAT-P-27b/WASP-40b and WASP-21b. All of them are suspected to show TTVs due to the known properties of their host systems based on the respective discovery papers. During the past three years 46 transit observations were carried out, mostly using telescopes of the Young Exoplanet Transit Initiative. The analyses are used to refine the systems orbital parameters. In all cases we found no hints for significant TTVs, or changes in the system parameters inclination, fractional stellar radius and planet to star radius ratio. However, comparing our results with those available in the literature shows that we can confirm the already published values.

Looking for a Second Star for Exoplanetary Systems

A Lucky Imaging search for stellar sources near 74 transit hosts

Authors:

Wöllert et al

Abstract:

Many transiting planet host stars lack high resolution imaging and thus close stellar sources can be missed. Those unknown stars potentially bias the derivation of the planetary and stellar parameters from the transit light curve, no matter if they are bound or not. In addition, bound stellar companions interact gravitationally with the exoplanet host star, the disk and the planets and can thus influence the formation and evolution of the planetary system strongly. We extended our high-resolution Lucky Imaging survey for close stellar sources by 74 transiting planet host stars. 39 of these stars lack previous high-resolution imaging, 23 are follow up observations of companions or companion candidates, and the remaining stars have been observed by others with AO imaging though in different bands. We determine the separation of all new and known companion candidates and estimate the flux ratio in the observed bands. All observations were carried out with the Lucky Imaging camera AstraLux Norte at the Calar Alto 2.2 m telescope in i' and z' passbands. We find new stellar sources within 1 arcsec to HAT-P-27, HAT-P-28, HAT-P-35, WASP-76, and WASP-103, and between 1 and 4 arcsec to HAT-P-29 and WASP-56.