EDP Sciences
Free access
Issue
A&A
Volume 424, Number 2, September III 2004
Page(s) 619 - 625
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20040016


A&A 424, 619-625 (2004)
DOI: 10.1051/0004-6361:20040016

X-ray detections of two young bona-fide brown dwarfs

H. Bouy

Max Planck für Extraterrestrische Phyisk, Giessenbachstraße, 85748 Garching bei München, Germany
    e-mail: hbouy@mpe.mpg.de Laboratoire d'Astrophysique de l'Observatoire de Grenoble, 414 rue de la piscine, 38400 Saint Martin d'Hères, France European Southern Observatory, Karl Schwarzschildtstraße 2, 85748 Garching bei München, Germany

(Received 6 January 2004 / Accepted 17 April 2004)

Abstract
I report the detection of two bona-fide brown dwarfs by XMM-Newton: [GY92] 141 in the $\rho$-Ophiuchus star-forming region and DENIS J155601-233809 in the Upper Scorpius OB association. The two objects have been detected with luminosities of $L_{\rm X} =8.35 \pm 2.86 \times 10^{28}$ erg s -1 and $L_{\rm X} =6.54 \pm 1.35 \times 10 ^{28}$ erg s -1 respectively, corresponding to luminosity ratios of log ( $L_{\rm X}/L_{\rm bol})=-2.07$ and log ( $L_{\rm X}/L_{\rm bol})=-2.69$. The two sources were close to the limit of detection of the instruments at only 2~3- $\sigma$ above the background level, and no significant flare or variation could be detected during the 48.3 ks and 33.9 ks observations. [GY92] 141 had already been observed 10 months earlier with Chandra by Imanishi et al. (2001) with a luminosity ~14 times fainter than the one reported here, indicating that the X-ray emission of this object is strongly variable.


Key words: stars: low-mass, brown dwarfs -- stars: coronae -- X-rays: individuals: [GY92] 141, DENIS J155601-233809

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