SETI bioastro: Radial velocity survey for planets and brown dwarf companions to very young brown dwarfs and very low-mass stars in ChaI with UVES at the VLT

• Previous message: LARRY KLAES: "SETI bioastro: The Demographics of Long-Period Comets"

Paper: astro-ph/0509134
Date: Tue, 6 Sep 2005 16:05:43 GMT (49kb)

Title: Radial velocity survey for planets and brown dwarf companions to very
young brown dwarfs and very low-mass stars in ChaI with UVES at the VLT

Authors: V. Joergens

Comments: accepted for publication in A&A
\\
We present results of a radial velocity (RV) survey for planets and brown
dwarf (BD) companions to very young BDs and (very) low-mass stars (VLMSs) in
ChaI. High-resolution echelle spectra have been taken with UVES / VLT between
2000 and 2004 of ChaHa1-8 and 12 (M6-M8) and B34, CHXR74, Sz23 (M2.5-M5). The
achieved precision (40 to 670 m/s) is sufficient to detect Jupitermass planets
around the targets. This first RV survey of very young BDs probes multiplicity,
which is a key parameter for formation in an as yet unexplored domain in terms
of age, mass and orbital separation. We find that on time scales of <40 days
the subsample of ten BDs and VLMSs (M<0.12 Msun, M5-M8) has constant RVs.
Estimates for upper limits for masses of hypothetical companions for them are
0.1 to 1.5 MJup (assuming 0.1 AU). This hints at a rather small multiplicity
fraction for very young BDs and VLMSs at <0.1 AU. Furthermore, the non-variable
objects demonstrate the lack of any significant RV noise due to stellar
activity down to the precision necessary to detect giant planets. Thus, very
young BDs and VLMSs are suitable targets for searches for RV planets. Three
objects of the sample exhibit significant RV variations. For Sz23, they might
be attributed by surface activity, while for ChaHa8 (M6.5) and CHXR74 (M4.5)
the detected RV variations are on times scales of >150 days, which cannot be
explained by rotational modulation. An alternative explanation are giant
planets / BDs of at least a few Jupiter masses orbiting with periods of several
months or longer. Thus, the presented RV data indicate that orbital periods of
companions to very young BDs and (V)LMSs are possibly several months or longer
and orbital separations > 0.2 AU. This parameter range has not been covered for
all targets yet but will be probed by follow-up observations.

\\ ( http://arXiv.org/abs/astro-ph/0509134 , 49kb)

• Previous message: LARRY KLAES: "SETI bioastro: The Demographics of Long-Period Comets"

This archive was generated by hypermail 2.1.6 : Sat Sep 10 2005 - 03:29:53 UTC