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X-ray emission from a brown dwarf in the Pleiades

By K. R. Briggs and J. P. Pye


We report on the first detection of X-ray emission from a brown dwarf in the Pleiades, the M7-type Roque 14, obtained using the EPIC detectors on XMM–Newton. This is the first X-ray detection of a brown dwarf intermediate in age between ≈12 and ≈320 Myr. The emission appears persistent, although we cannot rule out flare-like behaviour with a decay time-scale >4 ks. The time-averaged X-ray luminosity of LX≈ 3.3 ± 0.8 × 1027 erg s−1 and its ratios with the bolometric (LX/Lbol≈ 10−3.05) and Hα (LX/LHα≈ 4.0) luminosities suggest magnetic activity similar to that of active main-sequence M dwarfs, such as the M7 old-disc star VB 8, although the suspected binary nature of Roque 14 merits further attention. No emission is detected from four proposed later-type Pleiades brown dwarfs, with upper limits to LX in the range 2.1–3.8 × 1027 erg s−1 and to log (LX/Lbol) in the range −3.10 to −2.91

Topics: stars: activity, stars: coronae, stars: individual: Roque 14, stars: low-mass, brown dwarfs, open clusters and associations: individual: the Pleiades, X-rays: stars
Publisher: Oxford University Press (OUP), Royal Astronomical Society
Year: 2004
DOI identifier: 10.1111/j.1365-2966.2004.08100.x
OAI identifier:

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