Direct imaging of the young spectroscopic binary HD 160934

Abstract

Context: Members of nearby moving groups are promising candidates for the detection of stellar or substellar companions by direct imaging. Mass estimates and magnitude measurements of detected companions to young stars are valuable input data to facilitate the refinement of existing pre-main-sequence stellar models. In this paper we report on our detection of a close companion to HD 160934, a young active star, SB1 spectroscopic binary, and suggested member of the AB Doradus moving group.
Aims: We obtained high angular resolution images of nearby young stars, searching for close companions. In the case of HD 160934, direct imaging was combined with unresolved photometry to derive mass estimates.
Methods: High angular resolution was achieved by means of the so-called "Lucky Imaging" technique, allowing direct imaging close to the diffraction limit in the SDSS z' band with a 2.2 m telescope. Our results are combined with pre-discovery HST archive data, own UBV(RI)_C broadband photometry, published JHK magnitudes, and available radial velocity measurements to constrain the physical properties of the HD 160934 close binary.
Results: At an assumed age of ~80 Myr, we derive mass estimates of 0.69 M_⊙ and 0.57 M_⊙, respectively, for HD 160934 and its close companion. We suggest that the direct detection may be identical to the spectroscopically discovered companion, leading to a period estimate of ~8.5 years and a semimajor axis of a≈ 4.5 AU.

Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at

Calar Alto, operated jointly by the Max-Planck-Institut für Astronomie and the Instituto

de Astrofísica de Andalucía (CSIC). Based on observations obtained

with MPIA's Königstuhl mountain 70 cm telescope.