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ASCA Observations of the Barnard 209 Dark Cloud and an Intense X-Ray Flare on V773 TauriASCA (Advanced Satellite for Cosmology and Astrophysics) detected an intense X-ray flare on the weak-lined T Tauri star V773 Tau (=HD 283447) during a 30 ks observation of the Barnard 209 dark cloud in 1995 September. This star is a spectroscopic binary and shows signs of strong magnetic surface activity including a spot-modulated optical light curve. The flare was seen only during its decay phase but is still one of the strongest ever recorded from a T Tauri star with a peak luminosity L(sub x) = 10(exp 32.4) ergs/s (0.5-10 keV), a maximum temperature of at least 42 million K, and energy release of greater than 10(exp 37) ergs. A shorter ASCA observation taken five months later showed V773 Tau in a quiescent state (L(sub x)= 10(exp 31.0) ergs/s) and detected variable emission from the infrared binary IRAS 04113+2758. The differential emission measure (DEM) distribution during the V773 Tau flare shows a bimodal temperature structure that is almost totally dominated by hot plasma at an average temperature of approx. 37 million K. Using information from time-resolved spectra, we examine the flare decay in terms of solar flare models (cooling loops and two-ribbon flares) and also consider possible nonsolar behavior (interbinary flares, star-disk flares, and rotational X-ray modulation). Solar models are unable to reproduce the unusual convex-shaped X-ray light curve, which decays slowly over a timespan of at least 1 day. However, the light curve decay is accurately modeled as a sinusoid with an inferred X-ray period of 2.97 days, which is nearly identical to the optical rotation period(s) of the two K-type components. This provides tantalizing evidence that the flaring region was undergoing rotational occultation, but periodic X-ray variability is not yet proven since our ASCA observation spans only one-third of a rotation cycle.
Document ID
19980076126
Acquisition Source
Goddard Space Flight Center
Document Type
Contractor Report (CR)
External Source(s)
doi:10.1086/304561
Authors
Skinner, Stephen L. (Colorado Univ. Boulder, CO United States)
Guedel, Manuel (Paul Scherrer Inst. Villigen, Switzerland)
Koyama, Katsuji (Kyoto Univ. Japan)
Yamauchi, Shigeo (Iwate Univ. Morioka, Japan)
Date Acquired
September 6, 2013
Publication Date
September 10, 1997
Publication Information
Publication: The Astrophysical Journal
Publisher: American Astronomical Society
Volume: 486
Issue: 2
Subject Category
Space Radiation
Report/Patent Number
NAS 1.26:207206
NASA/CR-97-207206
Funding Number(s)
CONTRACT_GRANT: NAG5-3224
Distribution Limits
Public
Copyright
Public Use Permitted.

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