Characterization of low-mass companion HD 142527 B

• Published in: arXiv.org 2018-09
• Main Authors: Christiaens, V, Casassus, S, Absil, O, Kimeswenger, S, Gomez Gonzalez, C A, Girard, J, Ramírez, R, Wertz, O, Zurlo, A, Flores, C, Salinas, V, Jordán, A, Mawet, D
• Format: Article
• Language: English
• Subjects: Algorithms; Deposition; Pre-main sequence stars; Spectra; Star & galaxy formation; Stellar age
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1806.04792

The circumstellar disk of the Herbig Fe star HD 142527 is host to several remarkable features including a warped inner disk, a 120 au-wide annular gap, a prominent dust trap and several spiral arms. A low-mass companion, HD 142527 B, was also found orbiting the primary star at \(\sim\)14 au. This study aims to better characterize this companion, which could help explain its 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 post-processed with several algorithms based on angular differential imaging (ADI). HD 142527 B is conspicuously re-detected in most spectral channels, which enables us to extract the first medium-resolution spectrum of a low-mass companion within 0.1'' from its central star. Fitting our spectrum with both template and synthetic spectra suggests that the companion is a young M2.5\(\pm\)1.0 star with an effective temperature of \(3500\pm100\) K, possibly surrounded with a hot (1700 K) circum-secondary environment. Pre-main sequence evolutionary tracks provide a mass estimate of \(0.34\pm0.06 M_{\odot}\), independent of the presence of a hot environment. However, the estimated stellar radius and age do depend on that assumption; we find a radius of \(1.37 \pm 0.05 R_{\odot}\) (resp. \(1.96 \pm 0.10 R_{\odot}\)) and an age of \(1.8^{+1.2}_{-0.5}\) Myr (resp. \(0.75 \pm 0.25\) Myr) in the case of the presence (resp. absence) of a hot environment contributing in \(H\)+\(K\). Our new values for the mass and radius yield a mass accretion rate of \(\sim\)5 \(\times 10^{-9} M_{\odot}\) yr\(^{-1}\) (2-3% that of the primary). Our results illustrate thus the potential for SINFONI+ADI to characterize faint close-in companions. The new spectral type makes HD 142527 B a twin of the well known TW Hya T-Tauri star, and the revision of its mass to higher values further supports its role in shaping the disk.