Millimagnitude optical transit photometry for extrasolar planet host OGLE-TR-113

DÍAZ, R. F.; FERNÁNDEZ, J.; RAMÍREZ, S.; MINNITI, D.; MAUAS, P.J.D.

Córdoba

Congreso; Boletín de la Asociación Argentina de Astronomía, vol.49, p.106; 2006

Asociación Argentina de Astronomía

We obtained high-quality optical (V) images with VIMOS at the ESO VLT, in order to get a very precise lightcurve of the transit of planet OGLE-TR-113b in front of its parent star. We performed difference image photometry using a space-varying kernel (see C. Alard A&AS 144 363), which allows to fit variations of the PSF function throughout the CCD chip. The resulting lightcurve has a rms of about 0.002 mag, comparable to photon noise and allows to perform accurate measurements of the eclipse depth as well as the transit duration. A fit to the lightcurve provides the orbital inclination angle i=86.7-90, and the ratios between orbit radius and stellar radius, and between planetary radius and stellar radius. Assumming the stellar radius to be Rstar 0.77 Rsol we obtain the orbit radius a= (0.0232 +- 0.0038) AU and the planetary radius Rp = (1.09 +- 0.09) Rj. The results are in good agreement with previous works. In this way, we obtain an independent confirmation of the substellar nature of OGLE-TR-113b.