Astrophys. J., 623, 291-301 (2005/April-2)
Discovery of extremely embedded X-ray sources in the R Coronae Australis star-forming core.
HAMAGUCHI K., CORCORAN M.F., PETRE R., WHITE N.E., STELZER B., NEDACHI K., KOBAYASHI N. and TOKUNAGA A.T.
Abstract (from CDS):
With the XMM-Newton and Chandra observatories, we detected two extremely embedded X-ray sources in the R Corona Australis (R CrA) star-forming core, near IRS 7. These sources, designated as XEand XW, have X-ray absorption columns of ∼3x1023/cm2 equivalent to AV∼180 mag. They are associated with the VLA centimeter radio sources 10E and 10W, respectively; XWis the counterpart of the near-infrared source IRS 7, whereas XEhas no K-band counterpart above 19.4 mag. This indicates that XEis 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 XEvaried between 29<logLX<31.2 ergs/s on timescales of 3-30 months; XEalso showed a monotonic increase in X-ray brightness by a factor of 2 in 30 ks 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. Although the X-ray spectrum from XEis similar to flare spectra from Class I protostars in luminosity and temperature, the light curve does not resemble the light curves of magnetically generated X-ray flares, because the variability timescale of XEis too long and variations in X-ray count rate were not accompanied by variations in spectral hardness. The short-term variation of XEmay be caused by the partial blocking of the X-ray plasma, while the month-long flux enhancement may be driven by mass accretion.
Stars: Activity - Stars: Magnetic Fields - Stars: Pre-Main-Sequence - Stars: Rotation - X-Rays: Stars
Table 2: [HCP2005] XW (Nos XE, XW).
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