Characterization of low-mass companion HD 142527 B^⋆

¹ Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
e-mail: valchris@das.uchile.cl
² Space sciences, Technologies & Astrophysics Research (STAR) Institute, Université de Liège, Allée du Six Août 19c, 4000 Sart Tilman, Belgium
³ Millenium Nucleus “Protoplanetary Disks”, Chile
⁴ Instituto de Astronomía, Universidad Católica del Norte, Avenida Angamos 0610 Antofagasta, Chile
⁵ Institut für Astro– und Teilchenpysik, Leopold–Franzens Universität Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austria
⁶ Space Telescope Science Institute, 3700 San Martin Dr. Baltimore, MD 21218, USA
⁷ Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
⁸ Núcleo de Astronomía, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile
⁹ Escuela de Ingeniería Industrial, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile
¹⁰ European Southern Observatory, Alonso de Córdova, 3107 Vitacura, Santiago, Chile
¹¹ Institute for Astronomy, University of Hawaii, 640 N. Aohoku Place, Hilo, HI, 96720 USA
¹² Department of Physics and Astronomy, Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, 890-0065 Japan
¹³ Instituto de Astrofísica, Pontificia Universidad Católica de Chile, Vicuña Mackenna 4860, 7820436 Macul, Santiago, Chile
¹⁴ Department of Astronomy, California Institute of Technology, 1200 E. California Blvd, Pasadena, 91125 USA
¹⁵ Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena, CA, 91109 USA

Received: 1 August 2016
Accepted: 12 June 2018

Abstract

Context. 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 ~14 au.

Aims. This study aims to better characterize this companion, which could help explain its impact on the peculiar geometry of the disk.

Method. 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).

Results. 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 ± 1.0 star with an effective temperature of 3500 ± 100 K, possibly surrounded with a hot (1700 K) circum-secondary environment. Pre-main sequence evolutionary tracks provide a mass estimate of 0.34 ± 0.06 M_⊙, 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 ± 0.05 R_⊙ (resp. 1.96 ± 0.10 R_⊙) and an age of 1.8_-0.5^+1.2 Myr (resp. 0.75 ± 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 of the companion yield a mass accretion rate of 4.1–5.8 × 10⁻⁹ M_⊙ yr⁻¹ (2–3% that of the primary).

Conclusions. We have constrained the physical properties of HD 142527 B, thereby illustrating 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.