AAS 201st Meeting, January, 2003
Session 12. Activity in Cool Stars
Poster, Monday, January 6, 2003, 9:20am-6:30pm, Exhibit Hall AB

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[12.08] Transition Region Emission From Very Low Mass Stars

C. M. Johns-Krull (Rice University), S. L. Hawley (University of Washington)

We present results from our cycle 10 HST program to search for transition region emission in very low mass stars in the spectral range M7-M9. Our program is aimed at 1) detecting emission; and 2) distinguishing between flaring and persistent origin for the emission. We have obtained time series observations of HST/STIS spectra of three active, very low mass stars (VB8, VB10, and LHS 2065) which reveal persistent emission in transition region lines including Si IV, C IV, and He II. This emission does show variability from one exposure to the next, but is always observed. A strong flare was also observed in one 10 minute exposure on VB10. Our preliminary analysis indicates that active, very low mass stars maintain a chromosphere and transition region that is similar to those observed in active, earlier type M dwarfs, in contrast to suggestions that these low mass stars exhibit only flaring activity.

This research was made possible by grant HST-GO-9090 from the Space Telescope Science Institute, operated by AURA for NASA.

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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.