Letter to the Editor

A brown dwarf companion to the intermediate-mass star HR 6037^*

¹ Centro de Astrobiología (CSIC-INTA) LAEFF, PO Box 78, 28691 Villanueva de la Cañada, Madrid, Spain e-mail: nhuelamo@cab.inta-csic.es
² European Southern Observatory, Alonso de Cordova 3107, Casilla 19, Santiago, Chile
³ Laboratoire d'Astrophysique, Observatoire de Grenoble, BP 53, 38041 Grenoble, Cedex 9, France
⁴ Universitá di Padova, vicolo Osservatorio 3, 35122, Padova, Italy
⁵ Gemini Observatory, Southern Operations Center, c/o AURA, Casilla 603, La Serena, Chile
⁶ Instituto de Astronomía, Geofísica e Ciencias Atmosféricas, Rua do Matão, 1226 - Cidade Universitaria, São Paulo, Brazil

Received: 7 September 2010
Accepted: 22 September 2010

Abstract

Context. The frequency of brown dwarf and planetary-mass companions around intermediate-mass stars is still unknown. Imaging and radial velocity surveys have revealed a small number of substellar companions to these stars.

Aims. In the course of an imaging survey we detected a visual companion to the intermediate-mass star HR 6037. We here confirm it as a co-moving substellar object.

Methods. We present two epoch observations of HR 6037, an A6-type star with a companion candidate at 667 and position angle of 294 degrees. We also analyze near-infrared spectroscopy of the companion.

Results. Two epoch observations of HR 6037 have allowed us to confirm HR 6037 B as a co-moving companion. Its J and H band spectra suggest that the object has a spectral type of M9, with a surface gravity that is intermediate between a 10 Myr dwarf and a field dwarf of the same spectral type. The comparison of its K_s-band photometry with evolutionary tracks allows us to derive a mass, effective temperature, and surface gravity of 62±20 M_Jup, T_eff = 2330±200 K, and log g = 5.1±0.2, respectively. The low binary mass ratio, q ~ 0.03, and its long orbital period, ~5000 yr, make HR 6037 a rare and uncommon binary system.