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X-ray variability of sigma Orionis young stars as observed with rosar

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Caballero, J. A. and López Santiago, J. and Castro Rubio, Elisa de and Cornide Castro-Piñeiro, Manuel (2009) X-ray variability of sigma Orionis young stars as observed with rosar. Astronomical journal, 137 (6). pp. 5012-5021. ISSN 0004-6256

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Official URL: http://dx.doi.org/10.1088/0004-6256/137/6/5012


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http://iopscience.iop.org/Publisher


Abstract

We used the Aladin Virtual Observatory tool and High Resolution Imager ROSAT archival data to search for X-ray variability in scale of days in 23 young stars in the sigma Orionis cluster and a background galaxy. Five stars displayed unambiguous flares and had probabilities p(var) >> 99% of being actual variables. Two of the detected flares were violent and long lasting, with maximum duration of six days and amplitude of eight times above the quiescent level. We classified another four stars as possible X-ray variables, including the binary system formed by the B2Vp star sigma Ori E and its close late-type companion. This makes a minimum frequency of high-amplitude X-ray variability in excess of a day of 39% among sigma Orionis stars. The incidence of this kind of X-ray variability seems to be lower among classical T Tauri stars with mid-infrared flux excesses than among fast-rotating, disk-less young stars.


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© 2009. The American Astronomical Society. All rights reserved. We are grateful to the anonymous referee, J. F. Albacete Colombo, and J. Sánz Forcada for helpful discussion and advice. Financial support was provided by the Universidad Complutense de Madrid, the Comunidad Autónoma de Madrid, the Spanish Ministerio Educación y Ciencia, and the European Social Fund under grants: AyA200502750, AyA2005-04286, AyA2005-24102-E, AyA2008-06423C03-03, AyA2008-00695, PRICITS-0505/ESP-0237, and CSD2006-0070. This research has made use of the SIMBAD, operated at Centre de Données astronomiques de Strasbourg, France, and the NASA's Astrophysics Data System.

Uncontrolled Keywords:Main-sequence stars; T-tauri stars; Serendipitous source catalog; XMM-Newton observations; All-sky survey; Brown dwarfs; Resolution spectroscopy; Energy-distributions; Molecular cloud; Space-telescope
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
ID Code:30760
Deposited On:11 Jun 2015 11:59
Last Modified:10 Dec 2018 15:05

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