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Multi-Wavelength Observations of EV Lacertae

  • Rachel A. Osten (a1), Suzanne L. Hawley (a2), Joel Allred (a2), Christopher M. Johns-Krull (a3), Christine Roark (a4), Carol Ambruster (a5), Alexander Brown (a6), Thomas R. Ayres (a6) and Jeffrey L. Linsky (a6)...

Abstract

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.

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References

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Proceedings of the International Astronomical Union
  • ISSN: -
  • EISSN: 0074-1809
  • URL: /core/journals/proceedings-of-the-international-astronomical-union
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