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Multi-Wavelength Observations of EV Lacertae

Published online by Cambridge University Press:  26 May 2016

Rachel A. Osten
Jansky Fellow, National Radio Astronomy Observatory, Charlottesville, VA 22903, USA
Suzanne L. Hawley
University of Washington, Seattle, WA, USA
Joel Allred
University of Washington, Seattle, WA, USA
Christopher M. Johns-Krull
Rice University, Houston, TX, USA
Christine Roark
University of Iowa, Ames, lA, USA
Carol Ambruster
Villanova University, Villanova, PA, USA
Alexander Brown
University of Colorado, Boulder, CO, USA
Thomas R. Ayres
University of Colorado, Boulder, CO, USA
Jeffrey L. Linsky
University of Colorado, Boulder, CO, USA


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We report on a large, multi-wavelength campaign to observe variability across the electromagnetic spectrum in the M dwarf flare star EV Lacertae, in 2001 September. The campaign involved X-ray (Chandra ACIS-S+HETG), UV (HST/STIS), and optical (McDonald) spectra, as well as optical photometry and multi-frequency radio (VLA) observations. EV Lac demonstrated both frequent and extreme variability during the course of the two day intensive recordings. Dispersed X-ray spectra confirm the metal underabundance seen in other active stars. The increase in continuum fluxes at short X-ray wavelengths during flare intervals compared to quiescent intervals signals the creation of high temperature plasma, a signature of the flare process. Multi-wavelength comparisons reveal interesting trends: X-ray flare frequencies are within the range predicted by optical observations, yet there is no correspondence between X-ray flares and optical flares in our data. Two UV flares occur during the rise stages of X-ray flares; a major radio flare is accompanied by a large optical flare, which has no apparent counterpart in the X-ray. The results give conflicting evidence for the applicability of the Neupert effect interpretation in stellar coronae.

Part 5: Stellar Magnetic Activity and Evolution
Copyright © Astronomical Society of the Pacific 2004 


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