Keck/OSIRIS Pa\ensuremathβ High-contrast Imaging and Updated Constraints on PDS 70b
Abstract
We present a high-contrast imaging search for Pa\ensuremathβ line emission from protoplanets in the PDS 70 system with Keck/OSIRIS integral field spectroscopy. We applied the high- resolution spectral differential imaging technique to the OSIRIS J-band data but did not detect the Pa\ensuremathβ line at the level predicted using the parameters of Hashimoto et al. (2020). This lack of Pa\ensuremathβ emission suggests the MUSE-based study may have overestimated the line width of H\ensuremathα. We compared our Pa\ensuremathβ detection limits with the previous H\ensuremathα flux and H\ensuremathβ limits and estimated A_V to be \raisebox-0.5ex~0.9 and 2.0 for PDS 70 b and c, respectively. In particular, PDS 70 b's A_V is much smaller than implied by high-contrast near-infrared studies, which suggests the infrared-continuum photosphere and the hydrogen- emitting regions exist at different heights above the forming planet.