2006/10/09 by Michael W. McElwain, Stanimir Metchev, Stanimir A. Metchev +13 · 1 citation
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Brown dwarf #Integral field spectrograph #Photometry (optics) #Physics #Spectral line #Spectrograph #Stars #Stellar classification #Stellar, planetary, and galactic studies #Surface gravity #William Herschel Telescope #astro-ph
paper · pdf · doi:10.1086/510063
published as Astrophys.J.656:505-514,2007 · 27 pages, 6 figures; accepted for publication to ApJ
arxiv created 2006/10/09 · openalex publication_date 2007/02/03 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We present commissioning data from the OSIRIS integral field spectrograph (IFS) on the Keck II 10 m telescope that demonstrate the utility of adaptive optics IFS spectroscopy in studying faint close-in substellar companions in the halos of bright stars. Our R ≈ 2000 J - and H -band spectra of the substellar companion to the 1-10 Myr old GQ Lup complement existing K -band spectra and photometry and improve on the original estimate of its spectral type. We find that GQ Lup B is somewhat hotter (M6-L0) than reported in the discovery paper by Neuhäuser and collaborators (M9-L4), mainly due to the surface gravity sensitivity of the K -band spectral classification indices used by the discoverers. Spectroscopic features characteristic of low surface gravity objects, such as lack of alkali absorption and a triangular H -band continuum, are indeed prominent in our spectrum of GQ Lup B. The peculiar shape of the H -band continuum and the difference between the two spectral type estimates is well explained in the context of the diminishing strength of H 2 collision-induced absorption with decreasing surface gravity, as recently proposed for young ultracool dwarfs by Kirkpatrick and collaborators. Using our updated spectroscopic classification of GQ Lup B and a reevaluation of the age and heliocentric distance of the primary, we perform a comparative analysis of the available substellar evolutionary models to estimate the mass of the companion. We find that the mass of GQ Lup B is 0.010-0.040 M ☉ . Hence, it is unlikely to be a wide-orbit counterpart to the known radial velocity extrasolar planets, whose masses are ≲0.015 M ☉ . Instead, GQ Lup A/B is probably a member of a growing family of very low mass ratio widely separated binaries discovered through high-contrast imaging.