AAS 203rd Meeting, January 2004
Session 43 Nearby Stars: Observations
Poster, Tuesday, January 6, 2004, 9:20am-6:30pm, Grand Hall

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[43.06] Coordinated Chandra and HST Observations of Proxima Centauri

J.L. Linsky, T. VanVliet (JILA/University of Colorado and NIST)

We describe and analyze coordinated HST/STIS, Chandra ACIS-S and RXTE observations of the M5.5~Ve flare star Proxima Centauri (\alpha~Cen~C, GJ~551). The observing program includes three sessions with the Chandra ACIS-S, one of which includes the HETGS in the beam, and one session with the HST STIS instrument with the E140M grating. The second Chandra observation is simultaneous with the HST observation. Since the star was observed in the continuous viewing zone, we have long, uninterrupted observing sequences. We observe Prox Cen in quiescence and during several small and moderate sized flares. We derive an emission measure distribution for quiescence covering the temperature range \log T = 4.3--7.4, and discuss the change in the emission measure distribution during the flares. We model the moderate-sized flare as a large loop and infer its physical properties discussing the applicability of the 2-ribbon solar flare model to stellar astronomy. We also discuss the change in shape of transition region lines (e.g., Si IV, C IV), infer the electron density from the O IV intersystem lines, and compare the quiescence and flare emission measure distributions.

This work is supported by grants from NASA and the Space Telescope Science Institute to the University of Colorado.

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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.