X-ray-emitting young stars in the Orion Nebula

Eric D. Feigelson, Patrick Broos, James A. Gaffney, Gordon Garmire, Lynne A. Hillenbrand, Steven H. Pravdo, Leisa Townsley, Yohko Tsuboi

Research output: Contribution to journalArticle

228 Citations (Scopus)

Abstract

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.

Original languageEnglish (US)
Pages (from-to)258-292
Number of pages35
JournalAstrophysical Journal
Volume574
Issue number1 I
DOIs
StatePublished - Jul 20 2002

Fingerprint

Orion nebula
stars
x rays
M stars
T Tauri stars
luminosity
early stars
plasma
O stars
B stars
young
plasma temperature
molecular clouds
massive stars
erg
observatories
astrophysics
observatory
shock
saturation

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Feigelson, E. D., Broos, P., Gaffney, J. A., Garmire, G., Hillenbrand, L. A., Pravdo, S. H., ... Tsuboi, Y. (2002). X-ray-emitting young stars in the Orion Nebula. Astrophysical Journal, 574(1 I), 258-292. https://doi.org/10.1086/340936
Feigelson, Eric D. ; Broos, Patrick ; Gaffney, James A. ; Garmire, Gordon ; Hillenbrand, Lynne A. ; Pravdo, Steven H. ; Townsley, Leisa ; Tsuboi, Yohko. / X-ray-emitting young stars in the Orion Nebula. In: Astrophysical Journal. 2002 ; Vol. 574, No. 1 I. pp. 258-292.
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abstract = "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.",
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Feigelson, ED, Broos, P, Gaffney, JA, Garmire, G, Hillenbrand, LA, Pravdo, SH, Townsley, L & Tsuboi, Y 2002, 'X-ray-emitting young stars in the Orion Nebula', Astrophysical Journal, vol. 574, no. 1 I, pp. 258-292. https://doi.org/10.1086/340936

X-ray-emitting young stars in the Orion Nebula. / Feigelson, Eric D.; Broos, Patrick; Gaffney, James A.; Garmire, Gordon; Hillenbrand, Lynne A.; Pravdo, Steven H.; Townsley, Leisa; Tsuboi, Yohko.

In: Astrophysical Journal, Vol. 574, No. 1 I, 20.07.2002, p. 258-292.

Research output: Contribution to journalArticle

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AU - Feigelson, Eric D.

AU - Broos, Patrick

AU - Gaffney, James A.

AU - Garmire, Gordon

AU - Hillenbrand, Lynne A.

AU - Pravdo, Steven H.

AU - Townsley, Leisa

AU - Tsuboi, Yohko

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N2 - 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.

AB - 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.

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Feigelson ED, Broos P, Gaffney JA, Garmire G, Hillenbrand LA, Pravdo SH et al. X-ray-emitting young stars in the Orion Nebula. Astrophysical Journal. 2002 Jul 20;574(1 I):258-292. https://doi.org/10.1086/340936