The First Definite Detection of X-rays from an Extremely Young Protostar

Details The First Definite Detection of X-rays from an Extremely Young Protostar The First Definite Detection of X-rays from an Extremely Young Protostar

Jul 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005sfet.confe..13h&link_type=abstract

"Star Formation in the Era of Three Great Observatories, meeting abstracts from the conference held July 13-15, 2005 in Cambridg

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Class I protostars exhibit powerful X-ray emission. Their X-ray activity can exceed those of older stars such as T-Tauri and main-sequence stars. Without surface convection to drive a solar-type dynamo mechanism, X-ray activity is suspected to be driven by magnetic activity linked to the mass accretion process. Mass accretion is thought to be more intense in the earliest Class 0 protostar phase, but X-ray emission from them has not been conclusively detected so far. This could be due to stronger X-ray absorption to their protostellar cores, or a certain transition in high energy activity between the Class 0 and Class I phases. With two XMM-Newton observations on March 2003, we detected for the first time strong X-ray emission from an extremely embedded source in the R Corona Australis star forming core, IRS 7 region. (Hamaguchi et al. 2005, ApJ, 623, 291) The source has the radio counterpart 10E (IRS7B) but no near-IR counterpart. These facts plus the strong X-ray absorption of nH ˜3e23 cm-2 (equivalent to AV ˜180m) indicate that the source is a Class 0 or perhaps a Class 0/I protostar. The X-ray spectrum showed thermal emission with kT= 3-4 keV with the luminosity up to 1031.2 ergs/s. The light curve showed gradual flux increase by a factor of two during 30 ksec, unlike solar-type magnetically driven X-ray flares, which have smaller variation timescales. The source was 10-100 times fainter during Chandra observations which occurred before and after the XMM-Newton observations. The flux enhancement on month timescales might be driven by sporadic mass accretion episode, while the short-term variation during the XMM-Newton observation could be related to the proto-stellar core rotation. We will also discuss the relation to the sub-millimeter outflow activity of Class 0 protostars and absence of X-ray activity on other Class 0 protostars.

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