DISCOVERY OF H alpha EMISSION FROM THE CLOSE COMPANION INSIDE THE GAP OF TRANSITIONAL DISK HD 142527

We utilized the new high-order 585 actuator Magellan Adaptive Optics system (MagAO) to obtain very high-resolution visible light images of HD 142527 with MagAO's VisAO science camera. In the median seeing conditions of the 6.5m Magellan telescope (0 ''.5-0 ''.7), we find MagAO delivers 24%-19% Strehl at H alpha (0.656 mu m). We detect a faint companion (HD 142527B) embedded in this young transitional disk system at just 86.3 +/- 1.9 mas (similar to 12 AU) from the star. The companion is detected in both H alpha and a continuum filter (Delta mag = 6.33 +/- 0.20 mag at H alpha and 7.50 +/- 0.25 mag in the continuum filter). This provides confirmation of the tentative companion discovered by Biller and co-workers with sparse aperture masking at the 8 m Very Large Telescope. The H alpha emission from the similar to 0.25 solar mass companion (EW = 180 angstrom) implies a mass accretion rate of similar to 5.9 x 10(-10) M-sun yr(-1) and a total accretion luminosity of 1.2% L-sun. Assuming a similar accretion rate, we estimate that a 1 Jupiter mass gas giant could have considerably better (50-1000x) planet/star contrasts at H alpha than at the H band (COND models) for a range of optical extinctions (3.4-0 mag). We suggest that similar to 0.5-5M(jup) extrasolar planets in their gas accretion phase could be much more luminous at H alpha than in the NIR. This is the motivation for our newMagAO GAPplanetS survey for extrasolar planets.