EDP Sciences
Free Access
Issue
A&A
Volume 421, Number 2, July II 2004
Page(s) 715 - 727
Section Stellar atmospheres
DOI https://doi.org/10.1051/0004-6361:20047159
Published online 22 June 2004


A&A 421, 715-727 (2004)
DOI: 10.1051/0004-6361:20047159

XMM-Newton observations of the $\sigma$ Ori cluster

I. The complex RGS spectrum of the hot star $\sigma$ Ori AB
J. Sanz-Forcada, E. Franciosini and R. Pallavicini

INAF - Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy

(Received 28 January 2004 / Accepted 30 March 2004)

Abstract
We present XMM-Newton observations of the young ( ${\sim} 2{-}5$ Myr) cluster around the hot (O9.5V) star $\sigma$ Orionis AB, aimed at obtaining a high resolution RGS spectrum of the hot star as well as EPIC imaging data for the whole field. We show that the RGS spectrum of $\sigma$ Ori AB may be contaminated by weaker nearby sources which required the development of a suitable procedure to extract a clean RGS spectrum and to determine the thermal structure and wind properties of the hot star. We also report on the detection of a flare from the B2Vp star $\sigma$ Ori E and we discuss whether the flare originated from the hot star itself or rather from an unseen late-type companion. Other results of this observation include: the detection of 174 X-ray sources in the field of $\sigma$ Ori of which 76 are identified as cluster members, including very low-mass stars down to the substellar limit; the discovery of rotational modulation in a late-type star near $\sigma$ Ori AB; no detectable line broadenings and shifts ( ${\la}
800$  km s -1) in the spectrum of $\sigma$ Ori AB together with a remarkable low value of the $\ion{O}{vii}$ forbidden to intercombination line ratio and unusually high coronal abundances of CNO elements.


Key words: stars: coronae -- stars: winds, outflows -- stars: individual: $\sigma$ Ori -- stars: early-type -- stars: late-type

Offprint request: J. Sanz-Forcada, jsanz@rssd.esa.int

SIMBAD Objects



© ESO 2004

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.