New deep XMM-Newton observations to the west of the sigma Orionis cluster - AstrophysicsReportar como inadecuado

New deep XMM-Newton observations to the west of the sigma Orionis cluster - Astrophysics - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Abstract: Aims: The objective of this study is to determine the general X-rayproperties of the young stars in the external regions of the sigma Orioniscluster tau ~ 3 Ma, d ~ 385 pc and yield constraints on the X-ray emission ofbrown dwarfs. Methods: We carried out a careful analysis of public data takenin an unexplored region to the west of the centre of the cluster with the threeEPIC cameras onboard the XMM-Newton mission. We looked for new X-ray youngstars among the 41 identified X-ray sources in the area with maximum likelihoodparameters L > 15 by cross-correlation with the USNO-B1, DENIS, and 2MASSdatabases. Results: Based on colour-colour, colour-magnitude, and hardnessratio diagrams, and previous spectroscopic, astrometric, and infrared-fluxexcess information, we classified the optical-near-infrared counterparts of theX-ray sources into: young stars 15, field stars 4, galaxies 19, andsources of unknown nature 3. Most of the X-ray detections, including those ofnine young stars, are new. We derived the X-ray properties e.g. temperatures,metallicities, column densities of the twelve young stars with the largestsignal-to-noise ratios. The X-ray parameters determined here are in wellagreement with those found in the cluster centre, where the stellar density ishigher. There is no relation between infrared excess and column density fromX-ray measurement in our data. We detected flaring events in two young stars ofthe sample. One of them showed a very large ~ 30 relative increase in flux.Both stars showed high coronal temperatures during the observation. Finally, wedetermined upper limits to the flux of the young stars and bright brown dwarfsnot detected by our searching algorithm.

Autor: J. Lopez-Santiago, J. A. Caballero


Documentos relacionados