Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21725306k&link_type=abstract
American Astronomical Society, AAS Meeting #217, #253.06; Bulletin of the American Astronomical Society, Vol. 43, 2011
Astronomy and Astrophysics
Astronomy
Scientific paper
We present three transits of GJ 1214b, observed as part of the Apache Point Observatory Survey of Transit Lightcurves of Exoplanets (APOSTLE). We used our r-band (λ = 625nm) lightcurves in conjunction with previously gathered (longer wavelength) transit lightcurves of GJ 1214b to re-derive system parameters. By using parameters such as transit duration (tT) and ingress/egress length (tG), we were able to reduce the degeneracies in our transit model. This is a preferred condition for Markov Chain Monte Carlo techniques, which are typically used to quantify uncertainties in measured parameters. The joint analysis of this multi-wavelength dataset confirms earlier estimates of system parameters such as planetary orbital period, the planet-to-star radius ratio and stellar density. However, we show that estimates of the absolute radius and mass of the planet depend strongly on how the stellar mass and radius are determined. Planet radius and mass can range between 2.5-3.2 Rearth) and 6.4-8.5 Mearth) respectively; depending on whether we use stellar mass-radius or mass-luminosity relations.
The lightcurves resulting from our milli-magnitude photometry also show features that may be attributed to stellar activity. During the first night we observed a 0.8% rise in the out-of-eclipse flux of the host star lasting approximately 3 minutes. The trend has a characteristic fast-rise exponential decay shape commonly associated with stellar flares. During the second night we observed a minor brightening during the transit. Due to its symmetric shape we believe this feature might have been caused by the planet obscuring a star-spot on the stellar disk. Finally, from our derived transit times we find no evidence for transit timing variations in this system.
Agol Eric
Barnes Robin
Becker Andrew C.
Kundurthy Praveen
Williams Bruce
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