Transition Region Emission From Very Low Mass Stars

Abstract

We present results from our cycle 10 HST program to search for transition region emission in very low-mass, main-sequence stars in the spectral range M7-M9. Our program is aimed at 1) detecting emission; and 2) distinguishing between flaring and quiescent origin for the emission. We have obtained HST/STIS time series observations of three active, very low mass stars (VB 8, VB 10, and LHS 2065) which show persistent activity in transition region lines including Si IV, C IV, He II. Emission in transition region lines appears to be variable between exposures, but is always observed. A strong flare was also observed in one 10 minute exposure on VB 10. Our results indicate that active, very low-mass stars maintain a persistent quiescent chromosphere and transition region that is similar to those observed in active, earlier type M dwarfs, in contrast to suggestions that these low-mass, main-sequence stars exhibit only relatively strong flares and no quiescent emission.

arXiv comment11 pages with 2 figures; accepted by ApJ Letters

References in corpus (11)

• New Neighbors from 2MASS: Activity and Kinematics at the Bottom of the Main Sequence
• The Palomar/MSU Nearby Star Spectroscopic Survey III: Chromospheric Activity, M-dwarf Ages and the Local Star Formation History
• X-ray emitting young stars in the Orion Nebula
• Activity in Very Cool Stars: Magnetic Dissipation in late-M and L Dwarf Atmospheres
• Flaring Up All Over -- Radio Activity in Rapidly-Rotating Late-Type M and L Dwarfs
• Chandra Detection of an X-ray Flare from the Brown Dwarf LP 944-20
• Are Coronae of Magnetically Active Stars Heated by Flares? II. EUV and X-Ray Flare Statistics and the Differential Emission Measure Distribution
• Flare Heating in Stellar Coronae
• An X-ray Flare Detected on the M8 Dwarf VB 10
• A Search for Variability in the Active T dwarf 2MASS 1237+6526
• XMM-Newton observations of the nearby brown dwarf LP 944-20

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