Home

About

Advanced Search

Browse by Discipline

Scientific Societies

E-print Alerts

Add E-prints

E-print Network
FAQHELPSITE MAPCONTACT US


  Advanced Search  

 
THE ASTROPHYSICAL JOURNAL, 541 : 396409, 2000 September 20 2000. The American Astronomical Society. All rights reserved. Printed in U.S.A.
 

Summary: THE ASTROPHYSICAL JOURNAL, 541 : 396»409, 2000 September 20
2000. The American Astronomical Society. All rights reserved. Printed in U.S.A.
(
EXTREME≠ULTRAVIOLET FLARE ACTIVITY IN LATE≠TYPE STARS
MARC AUDARD,1,2 MANUEL GU# DEL,1,2 JEREMY J. DRAKE,3 AND VINAY L. KASHYAP3
Received 2000 March 7 ; accepted 2000 May 2
ABSTRACT
Extreme Ultraviolet Explorer Deep Survey observations of cool stars (spectral type F to M) have been
used to investigate the distribution of coronal —are rates in energy and its relation to activity indicators
and rotation parameters. Cumulative and di+erential —are rate distributions were constructed and –tted
with di+erent methods. Power laws are found to approximately describe the distributions. A trend
toward —atter distributions for later type stars is suggested in our sample. Assuming that the power laws
continue below the detection limit, we have estimated that the superposition of —ares with radiated ener≠
gies of about 1029»1031 ergs could explain the observed radiative power loss of these coronae, while the
detected —ares are contributing only B10%. Although the power≠law index is not correlated with rota≠
tion parameters (rotation period, projected rotational velocity, Rossby number) and only marginally with
the X≠ray luminosity, the —are occurrence rate is correlated with all of them. The occurrence rate of
—ares with energies larger than 1032 ergs is found to be proportional to the average total stellar X≠ray
luminosity. Thus, energetic —ares occur more often in X≠ray bright stars than in X≠ray faint stars. The
normalized occurrence rate of —ares with energies larger than 1032 ergs increases with increasing L X /L bol

  

Source: Audard, Marc - INTEGRAL Science Data Centre & Observatory of Geneva, Universitť de GenŤve
Guedel, Manuel - Institut fŁr Astronomie, Universitšt Wien

 

Collections: Physics