| Type |
Journal Article |
| Names |
R. D. Robinson, K. G. Carpenter, J. W. Percival |
| Publication |
The Astrophysical Journal |
| Volume |
516 |
| Issue |
2 |
| Pages |
916-923 |
| Date |
May 1, 1999 |
| URL |
http://adsabs.harvard.edu/abs/1999ApJ...516..916R |
| Library Catalog |
NASA ADS |
| Abstract |
We report on time-series photometric observations of the dM4.5e flare
star YZ Canis Minoris obtained in 1993 November with the High Speed
Photometer on board the Hubble Space Telescope. The data consist of five
30 minute time sequences with a sampling rate of 0.01 s that were taken
through the F240W filter (centered at 240 nm with an 80 nm width). At
these wavelengths the stellar photospheric background is small, so
relatively small flares can be detected. The observations show a stellar
background of 120 counts s^-1 on which are superposed 54 flare events
ranging in integrated flux from 2.0x10^28 to 3.0x10^30 ergs, as well as
longer term variations with an amplitude of up to 50% of the average
continuum intensity and timescales ranging from several minutes to
hours. A statistical analysis of this background suggests that it may be
composed of unresolved microflaring activity that has an energy
distribution considerably steeper than that deduced for the larger flare
events. This is consistent with previous observations as well as the
self-organized criticality and reconnecting current sheet flare
theories. These results are compared with data from the dM8e flare star
CN Leonis, which was obtained earlier with the same experimental setup.
CN Leo has both a smaller stellar background and a lower flare
occurrence rate than YZ CMi. The fact that CN Leo also has a quiescent
X-ray flux that is less than 10% of the YZ CMi emission suggests a link
between chromospheric and coronal heating. |
| Tags |
CN LEONIS), STARS: ACTIVITY, STARS: INDIVIDUAL (YZ CANIS MINORIS, Stars: Flare, ULTRAVIOLET: STARS |