Dissemin is shutting down on January 1st, 2025

Published in

American Astronomical Society, Astrophysical Journal Supplement, 2(173), p. 673-681, 2007

DOI: 10.1086/516640

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The detection of M dwarf UV flare events in the GALEX data archives

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Data provided by SHERPA/RoMEO

Abstract

We present the preliminary results from implementing a new software tool that enables inspection of time-tagged photon data for the astronomical sources contained within individual GALEX ultraviolet (UV) images of the sky. We have inspected the photon data contained within 1802 GALEX images to reveal rapid, short-term (500 s) UV source variability in the form of stellar "flares." The mean associated change in near-UV (NUV) magnitude due to this flaring activity is 2.7 ± 0.3 mag. A list of 49 new UV variable star candidates is presented, together with their associated Sloan Digital Sky Survey (SDSS) photometric magnitudes. From these data we can associate the main source of these UV flare events with magnetic activity on M dwarf stars. Photometric parallaxes have been determined for 32 of these sources, placing them at distances ranging from approximately 25 to 1000 pc. The average UV flare energy for these flare events is 2.5 × 1030 ergs, which is of a similar energy to that of U-band, X-ray, and EUV flares observed on many local M dwarf stars. We have found that stars of classes M0 to M5 flare with energies spanning a far larger range and with an energy approximately 5 times greater than those of later (M6 to M8) spectral type.