Issue |
A&A
Volume 404, Number 1, June II 2003
|
|
---|---|---|
Page(s) | 171 - 185 | |
Section | Galactic structure, stellar clusters, and populations | |
DOI | https://doi.org/10.1051/0004-6361:20030407 | |
Published online | 26 May 2003 |
The σ Orionis substellar population *,**
VLT/FORS spectroscopy and 2MASS photometry
1
Laboratorio de Astrofísica Espacial y Física Fundamental, INTA, PO Box 50727, 28080 Madrid, Spain
2
Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
3
Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
4
Institute of Astronomy. University of Hawaii at Manoa. 2680 Woodlawn Drive, Honolulu, HI 96822, USA
5
Consejo Superior de Investigaciones Científicas, CSIC, Spain
Corresponding author: D. Barrado y Navascués, barrado@laeff.esa.es
Received:
27
November
2002
Accepted:
12
March
2003
VLT/FORS spectroscopy and 2MASS near-infrared photometry,
together with previously known data, have been used to
establish the membership and the properties of a sample
of low-mass candidate members of the σ Orionis
cluster with masses spanning from 1 down to
about 0.013
(i.e., deuterium-burning mass
limit). We have observed K-band infrared excess and
remarkably intense Hα emission in various cluster
members, which, in addition to the previously detected
forbidden emision lines and the presence of Li i
in absorption at 6708 Å, have allowed us to
tentatively classify σ Orionis members as
classical or weak-line T Tauri stars and substellar
analogs. Variability of the Hα line has been
investigated and detected in some objects. Based on
the K-band infrared excesses and the
intensity of Hα emission, we estimate that the
minimum disk
frequency of the σ Orionis low-mass population is
in the range 5–12%.
Key words: open clusters and associations: individual: σ Orionis / stars: low-mass, brown dwarfs
© ESO, 2003
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.