Chandra Observations of variable embedded X-ray sources in Orion. I. Resolving Orion Trapezium

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dc.contributor.author Schulz, Norbert en_US
dc.contributor.author Canizares, Claude en_US
dc.contributor.author Huenemoerder, David en_US
dc.contributor.author Kastner, Joel en_US
dc.contributor.author Taylor, S. en_US
dc.contributor.author Bergstrom, Erik en_US
dc.date.accessioned 2006-05-23T15:56:04Z en_US
dc.date.available 2006-05-23T15:56:04Z en_US
dc.date.issued 2001-03-01 en_US
dc.identifier.citation Astrophys.J. 549 (2001) 441-451 en_US
dc.identifier.issn 1538-4365 en_US
dc.identifier.uri http://hdl.handle.net/1850/1862 en_US
dc.description Also archived in: arXiv: astro-ph/0011366 v1 20 Nov 2000 en_US
dc.description.abstract We used the High Energy Transmission Grating Spectrometer (HETGS) onboard the Chandra X-ray Observatory to perform two observations, separated by three weeks, of the Orion Trapezium region. The zeroth order images on the Advanced CCD Imaging Spectrometer (ACIS) provide spatial resolution of 0.5" and moderate energy resolution. Within a 160"x140" region around the Orion Trapezium we resolve 111 X-ray sources with luminosities between 7×10^28 erg s^-1 and 2×10^32 erg s^-1 . We do not detect any diffuse emission. All but six sources are identified. From spectral fits of the three brightest stars in the Trapezium we determine the line of sight column density to be NH = 1.93±0.29×10^21 cm^-2. Many sources appear much more heavily absorbed, with NH in the range of 10^22 to 10^23 cm^-2. A large fraction of sources also show excursions in luminosity by more than a factor 5 on timescales >50 ks; many are only detected in one of the observations. The main objective of this paper is to study the Orion Trapezium and its close vicinity. All five Trapezium stars are bright in X-rays, with Theta-1 Ori C accounting for about 60% of the total luminosity of the Trapezium. The CCD spectra of the three very early type members can be fit with a two-temperature thermal spectrum with a soft component of kT ~0.8 keV and a hard component of kT~2 to 3 keV. Theta-1 Ori B is an order of magnitude fainter than Theta-1 Ori E and shows only a hard spectrum of kT~3 keV. Theta-1 Ori D is another order of magnitude fainter than Theta-1 Ori B, with only a kT~0.7 keV component. We discuss these results in the context of stellar wind models. We detect eight additional, mostly variable X-ray sources in the close vicinity of the Trapezium. They are identified with thermal and non-thermal radio sources, as well as infrared and optical stars. Five of these X-rays sources are identified with proplyds and we argue that the X-ray emission originates from class I, II and III protostars at the cores of the proplyds (Refer to PDF file for exact formulas). en_US
dc.description.sponsorship The authors thank John Bally for generously providing us with the HST PC image of the Trapezium. We also thank all the members of the Chandra team for their enormous efforts. This research is funded in part by the Smithsonian Astrophysical Observatory contract SV-61010 (CXC) and NAS8-39073 (HETG) under the Marshall Space Flight Center. en_US
dc.format.extent 1295575 bytes en_US
dc.format.mimetype application/pdf en_US
dc.language.iso en_US en_US
dc.publisher Astrophysical Journal en_US
dc.relation.ispartofseries vol. 549 en_US
dc.relation.ispartofseries no. 1 en_US
dc.subject Open clusters and associations - individual - Trapezium en_US
dc.subject Stars - early-type en_US
dc.subject Stars - formation en_US
dc.subject Techniques - spectroscopic en_US
dc.subject X-rays - stars en_US
dc.title Chandra Observations of variable embedded X-ray sources in Orion. I. Resolving Orion Trapezium en_US
dc.type Article en_US

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