X-Ray-emitting Young Stars in the Orion Nebula

By Eric D. Feigelson, Patrick S. Broos, James A. Gaffney III, G. Garmire, L. Hillenbrand, S. Pravdo, L. Townsley, Y. Tsuboi. 2002

251 citations recorded by the source corpus.

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 log LX ≃ 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 log NH < 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. Results 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.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/2435ae5e6acb01709b334bf12e6969a672d913e4

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Atomic and Molecular Physics, and Optics

Citations in the corpus

A Deep Chandra Survey of the Globular Cluster 47 Tucanae: Catalog of Point Sources (2005, unknown): “Our source extraction procedure generally follows the methods of Feigelson et al. (2002) and Muno et al. (2003).”
Heating Protoplanetary Disk Atmospheres (2004, background): “A slightly smaller LX has been obtained for YSOs older than 1 Myr, but in a broader range of stellar masses, 0.7–1.4 M (Feigelson et al. 2002).”
Hard X-ray view of the past activity of Sgr A in a natural Compton mirror (2004, background): “…X-ray sources (mostly young, low mass stars) in nearby, well-studied molecular clouds such as Orion and ρ Oph is substantially softer (Revnivtsev et al. 2004b) than that of Sgr B2 and does not exhibit a strong intrinsic 6.4 keV emission line (Feigelson et al. 2002; Imanishi, Koyama & Tsuboi 2001).”
Flaring Activity of Sagittarius A* at 43 and 22 GHz: Evidence for Expanding Hot Plasma (2006, background): “Early B stars tend to contribute between 1030 and 1031 ergs s−1 per star in the 2-8 keV band (Feigelson et al. (2002).”
Determination of the gas-to-dust ratio in nearby dense clouds using X-ray absorption measurements (2003, methodology): “With much higher sensitivity and angular resolution, Chandrarecently detected more than 1000 sources in the ONC identified with previously known members (Feigelson et al. 2002).”
A Deep Chandra Catalog of X-Ray Point Sources toward the Galactic Center (2003, methodology): “Among ordinary stellar systems, about 10% of the X-ray stars in the Orion Nebula cluster (Feigelson et al. 2002) and 70% of RS CVn systems (Dempsey et al. 1993) lie within the luminosity range of the detected sources.”
10 MK Gas in M17 and the Rosette Nebula: X-Ray Flows in Galactic H II Regions (2003, methodology): “…evaluate this effect by comparing the M 17 and Rosette clusters to the Orion Nebula Cluster (ONC) and its environs, for which there is both a more complete stellar census and deeper ChandraX-ray coverage than for the clusters considered here (Feigelson et al. 2002, see their Tables 2, 3, and 5).”
The Evolution of X-Ray Emission in Young Stars (2005, background): “…or two-temperature optically thin thermal plasma MEKAL models (Mewe 1991), assuming 0.3 times solar abundances (Imanishi, Koyama, & Tsuboi 2001; Feigelson et al. 2002a) and X-ray absorption according to the atomic cross sections of Morrison & McCammon (1983) with traditional solar abundances…”
The Sun in Time: Activity and Environment (2007, background): “Although cosmic rays have long been suspected to be an effective disk ionization source (Gammie, 1996), the high-level, hard coronal emission and frequent stellar flares may be more effective ionizing sources (Glassgold et al., 1997; Feigelson et al., 2002b).”
TIME EVOLUTION OF VISCOUS CIRCUMSTELLAR DISKS DUE TO PHOTOEVAPORATION BY FAR-ULTRAVIOLET, EXTREME-ULTRAVIOLET, AND X-RAY RADIATION FROM THE CENTRAL STAR (2009, background): “There is a minimum value for LX and ΦEUV at ∼ 3M⊙ due to a drop in chromospheric activity as convection ceases near the stellar surface (e.g., Feigelson et al. 2002).”
The Origin of T Tauri X-Ray Emission: New Insights from the Chandra Orion Ultradeep Project (2005, methodology): “The results of two Advanced CCD Imaging Spectrometer observations with a combined exposure time of 23 hr were reported in Garmire et al. (2000) and Feigelson et al. (2002a, 2002b, 2003).”
Chandra Orion Ultradeep Project: Observations and Source Lists (2004, methodology): “Counterparts to earlier Einstein, ROSAT , and ASCA sources are given by Feigelson et al. (2002a).”
A Census of Optical and Near-Infrared Selected Star-forming and Passively Evolving Galaxies at Redshift z ~ 2 (2005, background): “′′5 for sources within 6′ of the average Chandra pointing origin, and set to the 50% encircled energy radius for sources with off-axis angles greater than 6′ (Feigelson et al. 2002).”
The distance to the Orion Nebula (2007, background): “In x-rays, GMR A is characterized as a “flare source” and the x-ray data indicate an absorbing column of 4 1022 cm−2, which is consistent with the extinction derived from the NIR data (Feigelson et al. 2002).”