Strong H-alpha emission and signs of accretion in a circumbinary planetary mass companion from MUSE

With the recent addition of the Narrow Field Mode (NFM), the Multi Unit Spectroscopic Explorer (MUSE) integral-field spectrograph on VLT UT4 now offers an AO-corrected field of view of 7.5'' x 7.5'' with a mean resolution of 3000 at 480-930 nm. Using MUSE in NFM we have observed 2MASS J01033563-5515561 (AB) b (Delorme 1 (AB) b), a 47 pc distant 12-14 MJup object orbiting a pair of young M5 stars at 84 AU (Eriksson et al. 2020). Observations covered 2.5 hours and obtained a near-visual spectrum (4750-9350 Å) of this hot, young planet/brown dwarf, in addition to resolving both components of the 0.25’’ binary (Fig. 1).

Here we present some highlights from our analysis of Delorme 1 (AB) b in Eriksson et al. (2020, A&A 638, L6). The most interesting one being very strong H𝛼 emission, 17 times the local continuum with a mean equivalent width of -138+-13 Å, accompanied by H𝛽 and weaker He I lines. Together, these lines provide a strong indication that Delorme 1 (AB) b could be actively accreting, possibly putting it at tension with its estimated age of 30-45 Myr, or hinting at the presence of an unusually old disk.