Astronomy and Astrophysics – Astrophysics
Scientific paper
2007-01-04
Astrophys.J.660:1507-1516,2007
Astronomy and Astrophysics
Astrophysics
ApJ, in press, 26 pages
Scientific paper
10.1086/512662
(Abridged) We present near-IR photometry and spectroscopy of HD 3651B, the low-luminosity, wide-separation (480 AU) companion to the K0V exoplanet host star HD 3651A. We find a spectral type of T7.5+/-0.5, a temperature of 780-840 K, and a mass of 40-72 Mjup; its bolometric luminosity and effective temperature are among the lowest measured for any brown dwarf. We estimate an age of 3-12 Gyr for the primary star HD 3651A and find that it is ~3x older than the K4V star Gl 570A (1-5 Gyr), the host star of the T7.5 dwarf Gl 570D. HD 3651B belongs to the rare class of substellar objects that are companions to main-sequence stars and thus provides a new benchmark for studying very low-temperature objects. Given their similar temperatures (within ~30 K) and metallicities (within ~0.1 dex) but different ages, a comparison of HD 3651B and GL 570D allows us to examine gravity-sensitive diagnostics in ultracool spectra. We find that the expected signature of HD 3651B's higher surface gravity due to its older age, namely a suppressed K-band flux relative to GL 570D, is not seen. Instead, the K-band flux of HD 3651B is enhanced compared to GL 570D, indicative of a younger age. Thus, the relative ages derived from interpretation of T dwarf spectra and from stellar activity indicators appear to be in discord. One likely explanation is that the K-band fluxes are also very sensitive to metallicity differences. Metallicity variations may be as important as surface gravity variations in causing spectral differences among field late-T dwarfs.
Chiu Kuenley
Leggett Sandy K.
Liu Michael C.
No associations
LandOfFree
The Late-T Dwarf Companion to the Exoplanet Host Star HD 3651: A New Benchmark for Gravity and Metallicity Effects in Ultracool Spectra does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The Late-T Dwarf Companion to the Exoplanet Host Star HD 3651: A New Benchmark for Gravity and Metallicity Effects in Ultracool Spectra, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Late-T Dwarf Companion to the Exoplanet Host Star HD 3651: A New Benchmark for Gravity and Metallicity Effects in Ultracool Spectra will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-15585