8th HEAD Meeting, 8-11 September, 2004
Session 5 Stars and the Sun
Poster, Wednesday, September 8, 2004, 9:00am-10:00pm

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[5.05] Spectra, Flares, and Mass Loss from the dMe star, Ross 154

B.J. Wargelin, J.J. Drake, V.L. Kashyap, D. Garcia-Alvarez (SAO)

We present results from a Chandra observation of Ross 154, a nearby (2.93 pc) flaring M dwarf (M4.5Ve). During the 57-ksec ACIS-S exposure, a very large flare occurred in which the counting rate increased by over a factor of 100, with an even larger increase in total X-ray power. For the earlier part of the lightcurve, we analyze photon arrival times to determine whether microflaring can explain the quiescent temporal behavior. Following the solar analogy, we assume that flares are distributed as a power-law in energy, and seek to determine whether the power law is steep enough that all coronal emission can be accounted for by flaring activity, as in the case of other active dMe stars such as AD Leo. We also compare elemental abundances derived from the quiescent and flare spectra and place an upper limit on the mass-loss rate by searching for stellar-wind charge-exchange X-ray emission. BW, JD, and DG were supported by the NASA Chandra X-ray Center Guest Observer Program under Grant GO2-3020X during the course of this research. BW, JD, and VK were also supported by NASA contract NAS8-39073 to the CXC.

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Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.