Discovery of H-alpha Emission from the Close Companion Inside the Gap of   Transitional Disk HD142527
  We utilized the new high-order 585 actuator Magellan Adaptive Optics system (MagAO) to obtain very high-resolution visible light images of HD142527 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 microns). We detect a faint companion (HD142527B) 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 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 8m VLT. The H-alpha emission from the ~0.25 solar mass companion (EW=180 Angstroms) implies a mass accretion rate of ~5.9x10^-10 Msun/yr, and a total accretion luminosity of 1.2% Lsun. Assuming a similar accretion rate, we estimate that a 1 Jupiter mass gas giant could have considerably better (50-1,000x) planet/star contrasts at H-alpha than at H band (COND models) for a range of optical extinctions (3.4-0 mag). We suggest that ~0.5-5 Mjup 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 new MagAO GAPplanetS survey for extrasolar planets. 
L.M. Close, K.B. Follette, J.R. Males, A. Puglisi, M. Xompero, D.   Apai, J. Najita, A.J. Weinberger, K. Morzinski, T.J. Rod...
astro-ph.EP