2005/03/02 by Kenji Hamaguchi, Michael F. Corcoran, M. F. Corcoran +9 · 3 citations
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Astrophysics and Star Formation Studies #Brightness #Corona (planetary geology) #Emission spectrum #Light curve #Luminosity #Optics #Physics #Protostar #Spectral line #Star formation #Stars #X-ray #astro-ph
paper · pdf · doi:10.1086/428434
published as Astrophys.J. 623 (2005) 291-301 · 26 pages, 8 figures, To be published in ApJ in April 2005
arxiv created 2005/03/02 · openalex publication_date 2005/04/10 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
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 X E and X W , have X-ray absorption columns of ~3 × 10 23 cm -2 equivalent to A V ~ 180 mag. They are associated with the VLA centimeter radio sources 10E and 10W, respectively; X W is the counterpart of the near-infrared source IRS 7, whereas X E has no K -band counterpart above 19.4 mag. This indicates that X E 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 X E varied between 29 < log L X < 31.2 ergs s -1 on timescales of 3-30 months; X E also 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 X E is 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 X E is too long and variations in X-ray count rate were not accompanied by variations in spectral hardness. The short-term variation of X E may be caused by the partial blocking of the X-ray plasma, while the month-long flux enhancement may be driven by mass accretion.