Characterization of the low-mass companion around HD 142527 with VLT/SINFONI

The circumstellar disk of the Herbig Fe star HD 142527 is host to several remarkable features in the context of planetary formation, including a warped inner disk, one of the largest annular gaps, a prominent dust trap and several spiral arms in its outer disk.
A low-mass companion, HD 142527 B, was also found orbiting the primary star at only ~10 au, possibly shaping the inclined inner disk (inclined with respect to the outer disk).
This study aims to provide a clarifying answer to the question of the true nature of this companion, which could help explaining its true impact on the peculiar geometry of the disk.
We observed the source with VLT/SINFONI in H+K band in pupil-tracking mode.
Data were then post-processed with several principal component analysis algorithms based on the principle of Angular Differential Imaging.
HD 142527 B is re-detected in most of the H+K spectral channels at a signal-to-noise ratio > 3.
This re-detection enables us to extract the first medium-resolution spectrum of a low-mass companion at less than 0.1'' from its central star.
The best fit to our spectrum was obtained with a BT-SETTL model spectrum corresponding to a temperature of 3400+-50K and a surface gravity log(g)=2.5+-1.0.
Using pre-main sequence tracks, this corresponds to an M3 star with a mass, radius and age of M_B ~0.3 M_Sun, R_B ~ 1.1 R_Sun and 3.6 Myr old, respectively.
We also suggest that most of the expected circum-secondary material is at a temperature lower than 1000K, hence not emitting in H and K band, but able to explain the excess measured at L- and M-bands.
Based on the new values of radius and mass of the companion, we provide a new estimate for the mass accretion rate on HD 142527 B of ~1% of the accretion rate on the primary, consistent with a non-significant detection in the Brackett-gamma line.
This result confirms the efficiency of the pupil-tracking mode implemented on VLT/SINFONI
for the spectral characterization of faint companions orbiting very close to their star.