X-ray emission from the young brown dwarfs of the Taurus Molecular Cloud

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dc.creatorGrosso, N.
dc.creatorBriggs, K. R.
dc.creatorGuedel, M.
dc.creatorGuieu, S.
dc.creatorFranciosini, E.
dc.creatorPalla, F.
dc.creatorDougados, C.
dc.creatorMonin, J. -L.
dc.creatorMenard, F.
dc.creatorBouvier, J.
dc.creatorAudard, M.
dc.creatorTelleschi, A.
dc.date2006-08-31
dc.date.accessioned2026-07-07T10:39:56Z
dc.date.available2026-07-07T10:39:56Z
dc.descriptionThe XMM-Newton Extended Survey of the TMC (XEST) is a large program designed to systematically investigate the X-ray properties of young stellar/substellar objects in the TMC. In particular, the area surveyed by 15 XMM-Newton pointings (of which three are archival observations), supplemented with one archival Chandra observation, allows us to study 17 BDs with M spectral types. Half of this sample (9 out of 17 BDs) is detected; 7 BDs are detected here for the first time in X-rays. We observed a flare from one BD. We confirm several previous findings on BD X-ray activity: a log-log relation between X-ray and bolometric luminosity for stars (with L*<10 Lsun) and BDs detected in X-rays; a shallow log-log relation between X-ray fractional luminosity and mass; a log-log relation between X-ray fractional luminosity and effective temperature; a log-log relation between X-ray surface flux and effective temperature. We find no significant log-log correlation between the X-ray fractional luminosity and EW(Halpha). Accreting and nonaccreting BDs have a similar X-ray fractional luminosity. The median X-ray fractional luminosity of nonaccreting BDs is about 4 times lower than the mean saturation value for rapidly rotating low-mass field stars. Our TMC BDs have higher X-ray fractional luminosity than BDs in the Chandra Orion Ultradeep Project. The X-ray fractional luminosity declines from low-mass stars to M-type BDs, and as a sample, the BDs are less efficient X-ray emitters than low-mass stars. We thus conclude that while the BD atmospheres observed here are mostly warm enough to sustain coronal activity, a trend is seen that may indicate its gradual decline due to the drop in photospheric ionization degree (abridged).
dc.description20 pages and 19 Figures. Accepted by A&A, to appear in a special section/issue dedicated to the XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST). Preprint with higher resolution figures is available at http://hal.ccsd.cnrs.fr/ccsd-00090499
dc.identifierhttps://arxiv.org/abs/astro-ph/0608696
dc.identifierhttp://arxiv.org/abs/astro-ph/0608696
dc.identifierAstron.Astrophys.468:391-403,2007
dc.identifierdoi:10.1051/0004-6361:20065559
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/181204
dc.subjectAstrophysics
dc.titleX-ray emission from the young brown dwarfs of the Taurus Molecular Cloud
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