Astronomy and Astrophysics – Astrophysics
Scientific paper
2003-06-24
Astrophys.J.593:L109-L112,2003
Astronomy and Astrophysics
Astrophysics
accepted for publication in The Astrophysical Journal Letters
Scientific paper
10.1086/378315
We present high-resolution optical spectroscopy of four candidate members of the nearby TW Hydrae young association including three brown dwarfs (2MASS 1207-3932, 2MASS 1139-3159 and TWA 5B) and one T Tauri multiple star (TWA 5A). Using echelle spectra from the Magellan Baade 6.5-meter telescope, we confirm the pre-main sequence status and cluster membership of the substellar candidates, through the detection of LiI, NaI consistent with low gravity, and radial velocity. Given their late spectral type (~M8) and the youth of the association (age ~10Myr), cluster membership certifies these three objects as very low-mass young brown dwarfs. One of them (2MASS 1207-3932) shows strong emission both in the Hydrogen Balmer series (H_alpha to H_epsilon) and in HeI (4471, 5876, 6678 and 7065 A), compared to other young brown dwarfs of similar spectral type. The H_alpha line is also relatively broad (10% width ~200 km/s) and asymmetric. These characteristics suggest that 2MASS 1207-3932 is a (weak) accretor. While we cannot rule out activity, comparison to a flaring field dwarf implies that such activity would have to be quite anomalous. The verification of accretion would make 2MASS 1207-3932 the oldest actively accreting brown dwarf known to date, suggesting that inner disk lifetimes in substellar objects can be comparable to those in stars, consistent with a similar formation mechanism. Finally, TWA 5A appears to be a variable accretor: observations separated by two days show broad accretion-like H_alpha (10% width \~270 km/s), with significant changes in the H_alpha profile, as well as in the strengths of HeI, Na D and [OI 6300]. TWA 5A is known to be a close triple; thus, our result implies that long-lived disks can exist even in multiple systems.
Jayawardhana Ray
Mohanty Subhanjoy
Navascues David Barrado y.
No associations
LandOfFree
Magellan Echelle Spectroscopy of TW Hydrae Brown Dwarfs 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 Magellan Echelle Spectroscopy of TW Hydrae Brown Dwarfs, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magellan Echelle Spectroscopy of TW Hydrae Brown Dwarfs will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-68526