other querymodes : Identifierquery Coordinatequery Criteriaquery Referencequery Basicquery Scriptsubmission TAP Outputoptions Help

2002ApJ...574..258F - Astrophys. J., 574, 258-292 (2002/July-3)

X-ray-emitting young stars in the Orion nebula.

FEIGELSON E.D., BROOS P., GAFFNEY III J.A., GARMIRE G., HILLENBRAND L.A., PRAVDO S.H., TOWNSLEY L. and TSUBOI Y.

Abstract (from CDS):

The Orion Nebula Cluster and the molecular cloud in its vicinity have been observed with the ACIS-I detector on board the Chandra X-ray Observatory with 23 hr exposure in two observations. We detect 1075 X-ray sources, most with subarcsecond positional accuracy. Ninety-one percent of the sources are spatially associated with known stellar members of the cluster, and an additional 7% are newly identified deeply embedded cloud members. This provides the largest X-ray study of a pre-main-sequence stellar population and covers the initial mass function from brown dwarfs up to a 45 M O star. Source luminosities span 5 orders of magnitude from logLX≃28.0 to 33.3 ergs.s–1 in the 0.5-8 keV band, plasma energies range from 0.2 to >10 keV, and absorption ranges from logNH<20.0 to ∼23.5 cm–2. Comprehensive tables providing X-ray and stellar characteristics are provided electronically.

We examine here the X-ray properties of Orion young stars as a function of mass; other studies of astrophysical interest will appear in companion papers.
Result. include: (a) the discovery of rapid variability in the O9.5 31 M star θ2A Ori, and several early B stars, inconsistent with the standard model of X-ray production in small shocks distributed throughout the radiatively accelerated wind; (b) support for the hypothesis that intermediate-mass mid-B through A type stars do not themselves produce significant X-ray emission; (c) confirmation that low-mass G through M type T Tauri stars exhibit powerful flaring but typically at luminosities considerably below the saturation'' level; (d) confirmation that the presence or absence of a circumstellar disk has no discernable effect on X-ray emission; (e) evidence that T Tauri plasma temperatures are often very high with T≥100 MK, even when luminosities are modest and flaring is not evident; and (f) detection of the largest sample of pre-main-sequence very low-mass objects showing flaring levels similar to those seen in more massive T Tauri stars and a decline in magnetic activity as they evolve into L and T type brown dwarfs.

Journal keyword(s): Galaxy: Open Clusters and Associations: Individual: Name: Orion Nebula Cluster - Stars: Activity - Stars: Early-Type - Stars: Low-Mass, Brown Dwarfs - Stars: Pre-Main-Sequence - X-Rays: Stars

VizieR on-line data: <Available at CDS (J/ApJ/574/258): table2.dat notes2.dat table3.dat notes3.dat table4.dat table5.dat table6.dat>

Nomenclature: Table 2: [FBG2002] NNNN (Nos 1-1075) = CXOONC JHHMMSS.s+DDMMSS N=1075.