Discovery of Extremely Embedded X-ray Sources in the R Coronae Australis Star Forming Core.pdfVIP

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Discovery of Extremely Embedded X-ray Sources in the R Coronae Australis Star Forming Core.pdf

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Discovery of Extremely Embedded X-ray Sources in the R Coronae Australis Star Forming Core

a r X i v : a s t r o - p h / 0 5 0 3 0 2 9 v 1 2 M a r 2 0 0 5 Revision according to the second referee’s comments Discovery of Extremely Embedded X-ray Sources in the R Coronae Australis Star Forming Core Kenji Hamaguchi1, Michael F. Corcoran2, Rob Petre, Nicholas E. White Exploration of the Universe Division, Goddard Space Flight Center, Greenbelt, MD 20771, USA kenji@; corcoran@; robert.Petre-1@; nwhite@ and Beate Stelzer INAF, Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, I-90134 Palermo, Italy stelzer@astropa.unipa.it and Ko Nedachi, Naoto Kobayashi Institute of Astronomy, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan nedachi@; naoto@ioa.s.u-tokyo.ac.jp and Alan T. Tokunaga Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA tokunaga@ 1National Research Council, 500 Fifth Street, NW, Washington, D.C. 20001, USA 2Universities Space Research Association, 7501 Forbes Blvd, Ste 206, Seabrook, MD 20706, USA – 2 – ABSTRACT With the XMM-Newton and Chandra observatories, we detected two ex- tremely embedded X-ray sources in the R Corona Australis (R CrA) star forming core, near IRS 7. These sources, designated as XE and XW, have X-ray absorption columns of ～3×1023 cm?2 equivalent to AV ～180 m. They are associated with the VLA centimeter radio sources 10E and 10W, respectively. XW is the counterpart of the near-infrared source IRS 7, whereas XE has no K-band counterpart above 19.4m. This indicates that XE is younger than typical Class I protostars, probably a Class 0 protostar or in an intermediate phase between Class 0 and Class I. The X-ray luminosity of XE varied between 29 log LX 31.2 ergs s ?1 on timescales of 3–30 months. XE also showed a monotonic increase in X-ray brightness by a factor of two in 30 ksec during an XMM-Newton observation. The XMM-Newton spectra indicate emission from a hot plasma with kT ～3–4 keV and also show fluorescent emission from cold iron. Though the X-ray spe