2014ApJ...781L..30C

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 6.5 m Magellan telescope (0.''5-0.''7), we find MagAO delivers 24%-19% Strehl at Hα (0.656 µm). We detect a faint companion (HD 142527B) embedded in this young transitional disk system at just 86.3±1.9 mas (∼12 AU) from the star. The companion is detected in both Hα and a continuum filter (Δmag = 6.33±0.20 mag at Hα 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 Hα emission from the ∼0.25 solar mass companion (EW = 180 Å) implies a mass accretion rate of ∼5.9x10^–10 M_sun/yr 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 Hα than at the H band (COND models) for a range of optical extinctions (3.4-0 mag). We suggest that ∼0.5-5 M_jup extrasolar planets in their gas accretion phase could be much more luminous at Hα than in the NIR. This is the motivation for our new MagAO GAPplanetS survey for extrasolar planets.