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Multi-Wavelength Observations of EV Lacertae

Published online by Cambridge University Press:  26 May 2016

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

Abstract

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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.

Type
Part 5: Stellar Magnetic Activity and Evolution
Information
Symposium - International Astronomical Union , Volume 219: Stars as Suns : Activity, Evolution and Planets , 2004 , pp. 249 - 253
Copyright
Copyright © Astronomical Society of the Pacific 2004 

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