Characterizing HR 3549 B using SPHERE

Abstract

Aims. In this work, we characterize the low-mass companion of the AO field star HR 3549.

Methods. We observed HR 3549B in imaging mode with the near-infrared branch (IFS and IRDIS) of SPHERE at the VLT, with IFS in YJ mode and IRDIS in the H band. We also acquired a medium-resolution spectrum with the IRDIS long-slit spectroscopy mode. The data were reduced using the dedicated SPHERE GTO pipeline, which is custom-designed for this instrument. We employed algorithms such as PCA and TLOCI to reduce the speckle noise.

Results. The companion was clearly visible with both IRDIS and IFS. We obtained photometry in four different bands and also the astrometric position for the companion. Based on our astrometry, we confirm that it is a bound object and set constraints on its orbit. Although several uncertainties still remain, we estimate an age of similar to 100-150 Myr for this system, yielding a most probable mass for the companion of 40-50 M-Jup and T-eff 2300-2400 K. Compared with template spectra, this points to a spectral type between M9 and L0 for the companion, commensurate with its position on the color-magnitude diagram.