INVESTIGATION OF SYSTEMATIC EFFECTS IN KEPLER DATA: SEASONAL VARIATIONS IN THE LIGHT CURVE OF HAT-P-7b

With years of Kepler data currently available, the measurement of variations in planetary transit depths over time can now be attempted. To do so, it is of primary importance to understand which systematic effects may affect the measurement of transits. We aim to measure the stability of Kepler meas...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2013-09, Vol.774 (2), p.1-6
Main Authors: VAN EYLEN, V, Nielsen, M Lindholm, HINRUP, B, Tingley, B, Kjeldsen, H
Format: Article
Language:English
Subjects:
ACCURACY
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
DIAGRAMS
Error analysis
Extrasolar planets
Gas giant planets
Jupiter satellites
Planet detection
PLANETS
SATELLITES
SEASONAL VARIATIONS
Seasons
Transit
VISIBLE RADIATION
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Summary:With years of Kepler data currently available, the measurement of variations in planetary transit depths over time can now be attempted. To do so, it is of primary importance to understand which systematic effects may affect the measurement of transits. We aim to measure the stability of Kepler measurements over years of observations. We present a study of the depth of about 500 transit events of the Hot Jupiter HAT-P-7b, using 14 quarters (Q0-Q13) of data from the Kepler satellite. We find a systematic variation in the depth of the primary transit, related to quarters of data and recurring yearly. These seasonal variations are about 1%. Within seasons, we find no evidence for trends. We speculate that the cause of the seasonal variations could be unknown field crowding or instrumental artifacts. Our results show that care must be taken when combining transits throughout different quarters of Kepler data. Measuring the relative planetary radius of HAT-P-7b without taking these systematic effects into account leads to unrealistically low error estimates. This effect could be present in all Kepler targets. If so, relative radius measurements of all Hot Jupiters to a precision much better than 1% are unrealistic.
ISSN:2041-8205
2041-8213
DOI:10.1088/2041-8205/774/2/L19