Photometric Detection of a Transit of HD 80606b

We report a times series of B-band photometric observations initiated on the eve of Valentine’s day, February 14, 2009, at the anticipated time of a transit of the extrasolar planet HD 80606b. The same transit has been observed independently (Fossey et al. 2009; Moutou et al. 2009). For one transit model favored by the data, minimum light equals 0.990 times the nominal brightness of HD 80606 and occurs at HJD 2454876.33. The latter time, combined with the orbital period $P=111.4277\pm 0.0032$ days, longitude of periastron, $\omega = 300.4977 \pm 0.0045$degrees,andtimeofmid-secondaryeclipseHJD$2454424.736 \pm 0.003$ (Laughlin et al. 2009), refines the orbital eccentricity and inclination. The duration of the model transit is 0.47 days, and its four contacts occur at HJD 2454876 plus 0.10, 0.24, 0.42, and 0.57 days. We describe parameterizations of a transit model with mutually accommodating eccentricity, $e=0.9337_{-0.0006}^{+0.0009}$, inclination, $i = 89.26^{+0.24}_{-0.09}$ degrees, and the planetary radius in units of the stellar radius \RpRs$=0.11_{-0.02}^{+0.04}$.