Optical spectroscopy of close companions to nearby Herbig Ae/Be and T Tauri stars

Abstract

We present VLT-FORS2 optical (5700 - 9400 A) spectroscopy of close (r < 1.5'') companions to three nearby (d < 200 pc) Herbig Ae/Be stars (HD 144432, HD 150193, KK Oph) and one T Tauri star (S CrA). We report the detection of Li I (6707 A) in absorption and emission lines (Halpha, Ca II triplet) in the spectra of the companions. Our observations strongly suggest that the companions are physically associated pre-main-sequence stars. The spectral type derived for the companions is K5Ve for HD 144432 B, F9Ve for HD 150193 B, and G6Ve for KK Oph B. S CrA A and B were observed simultaneously. The spatially resolved spectra indicate that S CrA A (primary, north) is a G star and that S CrA B (secondary, south) is a K star. Using photometry from the literature and estimations of the R and I magnitude derived from the spectra, we localized primaries and companions in the HR diagram, derived their masses and assuming coevality constrained the age of the systems. KK Oph B (7 Myr) and S CrA B (2 Myr) are actively accreting T Tauri stars and are very likely surrounded by disks. HD 150193 B (10 Myr) and HD 144432 B (8 Myr) are weak-line T Tauri stars. Three of the four systems studied (HD 144432, HD 150193, KK Oph) have ages > 7 Myr. These systems retained their disks for a longer time than typical of a young star. Our results suggest that binarity may be a key issue in understanding the lifetime of disks.

11 pages, 5 Postscript figures, accepted by A&A (18/12/2006)

References in corpus (2)

• Properties of planets in binary systems. The role of binary separation
• Terrestrial Planet Formation Surrounding Close Binary Stars

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• Mid-infrared size survey of Young Stellar Objects: Description of Keck segment-tilting experiment and basic results
• A family portrait of disk inner rims around Herbig Ae/Be stars: Hunting for warps, rings, self shadowing, and misalignments in the inner astronomical units
• The mass and size of Herbig disks as seen by ALMA
• A Census of Stars and Disks in Corona Australis
• ISPY-NACO Imaging Survey for Planets around Young stars. The demographics of forming planets embedded in protoplanetary disks
• The GRAVITY young stellar object survey XIV : Investigating the magnetospheric accretion-ejection processes in S CrA N
• The wind and the magnetospheric accretion onto the T Tauri star S Coronae Australis at sub-au resolution
• Planet formation in intermediate-separation binary systems