STRESS - STEREO transiting exoplanet and stellar survey

The Solar TErrestrial RElations Observatory - STEREO, is a system of two identical spacecraft in Heliocentric Earth orbit. We use the two Heliospheric Imagers (HI) on board, which are wide angle imagers with multi-baffle systems to do high precision stellar photometry in order to search for exoplanetary transits and understand stellar variables. The cadence (40 min for HI-1 and 2 hrs for HI-2), high precision (< 1% scatter for R < 8 and a few per cent for fainter objects), wide magnitude range (R mag - 4 to 12) and broad sky coverage (nearly 20 percent just for HI-1A and 60 per cent of the sky in the zodiacal region for all the instruments combined) of this instrument marks this in a space left largely devoid by other current projects. This thesis describes the instrument and its capabilities, the semi-automated pipeline devised for the reduction of this data and the general characteristics of the data obtained. This thesis explains the data analysis methods used in identifying exoplanetary transits and stellar variables along with some of the early results. The thesis concludes with a description of the work in progress and also outlines some of the future prospects of this massive STRESS data set

Detection of solar-like oscillations from Kepler photometry of the open cluster NGC 6819

Asteroseismology of stars in clusters has been a long-sought goal because the assumption of a common age, distance and initial chemical composition allows strong tests of the theory of stellar evolution. We report results from the first 34 days of science data from the Kepler Mission for the open cluster NGC 6819 -- one of four clusters in the field of view. We obtain the first clear detections of solar-like oscillations in the cluster red giants and are able to measure the large frequency separation and the frequency of maximum oscillation power. We find that the asteroseismic parameters allow us to test cluster-membership of the stars, and even with the limited seismic data in hand, we can already identify four possible non-members despite their having a better than 80% membership probability from radial velocity measurements. We are also able to determine the oscillation amplitudes for stars that span about two orders of magnitude in luminosity and find good agreement with the prediction that oscillation amplitudes scale as the luminosity to the power of 0.7. These early results demonstrate the unique potential of asteroseismology of the stellar clusters observed by Kepler.Comment: 5 pages, 4 figures, accepted by ApJ (Lett.