Chandra X-ray observatory study of the Orion Nebula cluster and BN/KL region

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

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98 Scopus citations


About 1000 X-ray emitting young pre-main-sequence (PMS) stars distributed in mass from ∼0.05 M brown dwarfs to a ∼ 50 M O star are detected in an image of the Orion Nebula obtained with the Advanced CCD Imaging Spectrometer on board the Chandra X-Ray Observatory. This is the richest field of sources ever obtained in X-ray astronomy. Individual X-ray luminosities in the Orion Nebula cluster range from the sensitivity limit of 2 × 1028 ergs s-1 to ∼1032 ergs s-1. ACIS sources include 85%-90% of V < 20 stars, plus a lower but substantial fraction of deeply embedded stars with extinctions as high as Av ≃ 60. The relationships between X-ray and other PMS stellar properties suggest that X-ray luminosity of lower-mass PMS stars depends more on mass, and possibly stellar rotation, than on bolometric luminosity, as widely reported. In a subsample of 17 unabsorbed stars with mass ≃ 1 M, X-ray luminosities are constant at a high level around Lx ≃ 2 × 1030 ergs s-1 for the first ≃ 2 Myr while descending the convective Hayashi track, but diverge during the 2-10 Myr phase with X-ray emission plummeting in some stars but remaining high in others. This behavior is consistent with the distribution of X-ray luminosities on the zero-age main sequence and with current theories of their rotational history and magnetic dynamos. The sources in the Becklin-Neugebauer/Kleinman-Low region of massive star formation are discussed in detail. They include both unabsorbed and embedded low-mass members of the Orion Nebula cluster, the luminous infrared Source n, and a class of sources without optical or infrared counterparts that may be new magnetically active embedded PMS stars. Several X-ray sources are also variable radio emitters, an association often seen in magnetically active PMS stars. Faint X-ray emission is seen close to, but apparently not coincident with, the Becklin-Neugebauer object. Its nature is not clear.

Original languageEnglish (US)
Pages (from-to)1426-1435
Number of pages10
JournalAstronomical Journal
Issue number3
StatePublished - Sep 2000

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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