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Multi-Wavelength Observations of Stellar Flares
Byrne, P. B.
We present observational data on stellar flares from a range of wavelength regimes, many of which were obtained simultaneously. Physical parameters of these flares are derived and discussed in the frame-work of the general solar flare model. It is found that flares on dMe stars are solar-like, except in mean energy. The parameters of flares on RS …
Observations of a shock and a recombination layer at the contact surface of comet Halley
Schwenn, R.; Altwegg, K.; Balsiger, H. +6 more
Observations in the vicinity of the contact surface (ionopause) of comet Halley obtained by the Giotto ion mass spectrometer (IMS) are reported. Two specific events in this region were observed on the inbound pass. Two seconds before the contact surface was encountered, a burst of energized ions (about 20 eV, much greater than thermal energies) wa…
X-Ray Spectroscopy of the Ultrasoft Transient 4U 1543-47
White, N. E.; van der Woerd, H.; Kahn, S. M.
The X-ray transient 4U 1543 - 47 was observed in August 1983 by the Exosat observatory near the maximum of an outburst. The X-ray spectrum was measured using a gas scintillation proportional counter (GSPC) and a transmission grating spectrometer (TGS). A broad (FWHM about 2.7 keV) line at 5.9 keV is detected in the GSPC, which is interpreted as a …
Soft X-ray observations of the VELA pulsar PSR 0833-45.
Oegelman, H.; Zimmermann, H. -U.
X-ray maps produced from Exosat observations of the Vela pulsar in the 0.03-2.4 keV range confirm the components discussed by Harnden et al. (1985). Restricting the central source to a neutron star with an 8-15 km radium emitting blackbody-like radiation suggests a surface temperature in the 600,000 to 1,000,000 K. It is found that the observed bl…
Flux-flux relation : MG II H and K versus X-rays in dwarf M and K stars.
Doyle, J. G.; Mathioudakis, M.
Surface X-ray and Mg II h and k fluxes are presented for a group of dMe, dKe, dM, and dK stars. No correlation is apparent between the fluxes for the group of stars as a whole, although a good correlation is present for a subgroup, i.e., the dMe/dKe's. The Mg II and X-ray luminosities for these active stars define an upper boundary, which is depen…
Chromospheric Structure of Cool Carbon Stars
Johnson, Hollis R.; Luttermoser, Donald G.; Avrett, Eugene H. +1 more
A semiempirical chromospheric model is proposed for TX Psc which is a prototype for the N-type carbon stars. Observational data imply that the chromospheric temperature rise must begin at a low density, that the temperature gradient in the lower chromosphere must be steep, that partial redistribution must be employed in the Mg II calculation, and …
Rotational modulation and flares on RS CVn and BY Draconis stars. XIII. IUE spectroscopy and photometry of II Pegasi during September 1986.
Doyle, J. G.; Rodono, M.; Butler, C. J. +3 more
UV spectroscopy obtained for the RS CVn star II Pegasi in September, 1986, indicates the presence of a rotational modulation effect for the Mg II h and k and O I 1305 A lines; the largest flux is observed when the primary spot concentration is nearly on the opposite hemisphere, and the rotational modulation is noted to be of opposite sense to that…
Fast Winds from the Central Stars of NGC 6543 and NGC 6826
Lamers, H. J. G. L. M.; Perinotto, M.; Cerruti-Sola, M.
The Sobolev exact integration method and high-resolution IUE data are used to examine the properties of the fast winds exhibited by the central stars of the planetary nebulae NGC 6543 and NGC 6826. An attempt is made to evaluate the parameters of the central stars as accurately as possible. The associated mass-loss rates (M-dot) are (4.0 + 10 or -…
One-pole and two-pole X-ray emission in the AM Herculis binary BL Hyi.
Beuermann, K.; Schwope, A. D.
This paper reports the results of extensive X-ray observations of BL Hyi = H0139-68 with the Exosat satellite when the source was in states of low and intermediate brightness. In the low state, X-rays were observed only between orbital phases phi = 0.0 and about 0.4, coincident with the orbital hump of cyclotron emission from the main pole. In the…
The density of cometary protons upstream of comet Halley's bow shock
Schwenn, R.; Balsiger, H.; Neubauer, F. M. +3 more
Cometary protons picked up by the solar wind were detected by the high energy range spectrometer of the Giotto ion mass spectrometer starting at a cometocentric distance of ~12×106 km. On the average, the density of cometary protons varied approximately as the inverse square of the cometocentric distance, reaching a value of 0.11 cm