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Differential emission measure distributions of Capella and σ2 CrB
Mewe, R.; Schrijver, C. J.; Lemen, J. R. +1 more
The active late-type stars Capella (α Aur G6III+F9III) and σ2 CrB (F6V+GV) (X-ray candidate emitters underlined) were observed with the EXOSAT Transmission Grating Spectrometer (TGS) in the region 10-200 Å. We have made an analysis of the differential emission measure (DEM) distribution. The derived DEM peaks between 3 and 7 MK and abov…
Magnetic reconnection and energy release in a long-duration stellar flare
Pallavicini, R.; Poletto, G.; Kopp, R. A.
A dynamical model of magnetic reconnection in solar two-ribbon flares is applied to EXOSAT observations of a long-decay flare from the star EQ Peg. We show that the model is able of reproducing correctly the energy release rate and temporal evolution of the decay phase of the observed flare. We conclude that the flare was the stellar counterpart o…
Evolution of the chromospheric and coronal activity of intermediate mass stars
Brown, Alexander
Recent ultraviolet and X-ray observations pertaining to the outer atmospheric structure of intermediate mass (4-6 M0) stars and the evolution of their structure are presented. A distance-limited (d <= 200 pc) IUE ultraviolet survey of early K bright giants shows that C IV emission commonly is present. These stars are almost evenly sp…
EXOSAT observations of two gamma-ray burst sources
Hurley, K.; Motch, C.; Boer, M. +18 more
EXOSAT observations of the 19 Nov 1978 and 25 Mar 1979b gamma bursters are presented, for the 0.02-2.5 keV energy range. No source was detected in either case, leading to temperature upper limits for the neutron stars assumed to be present of 105-106 °K. Polar cap accretion rates are constrained to values of 10-12-…
X-ray, UV, optical and radio observations of the visual binary 53 AQR
Pasquini, L.; Monsignori-Fossi, B. C.; Pallavicini, R. +1 more
The authors present optical (ESO), ultraviolet (IUE), X-ray (EXOSAT) and radio (VLA) observations of the visual binary 53 Aquarii. They show that the two components of the system can be used to infer the properties of the Sun at a much earlier epoch.
Coronal models of late-type stars observed with EXOSAT
Monsignori-Fossi, B. C.; Landini, M.; Pallavicini, R. +1 more
Differential emission measure distributions for transition region and corona able to reproduce X-ray and UV emission are investigated. The EXOSAT, EINSTEIN and IUE data for the solar type star K Cet are analyzed. A multitemperature differential emission measure distribution gives a satisfactory fit of the data.
Coronal X-ray temperatures from Einstein and EXOSAT observations
Schmitt, J. H. M. M.; Monsignori-Fossi, B. C.; Pallavicini, R. +1 more
Spectral analysis of coronal X-ray emission from stars observed with both the Einstein and EXOSAT Observatories is presented. Using computer codes developed by Raymond and Smith /1/ and Landini and Fossi /2/ to calculate the X-ray emission from optically thin plasma in collisional equilibrium we find that the derived coronal parameters depend only…