Search Publications
The chemical composition of the lambda Bootis stars.
Baschek, B.; Slettebak, A.
Measurements of the equivalent widhts of 24 UV lines from IUE spectra of 10 λ Bootis or suspected λ Bootis stars and 19 normal standard stars of spectral types B8-A7 are compared with line strengths calculated from model atmospheres. The light elements (C, N, and O) in the λ Boo stars are in the range slightly overabundant relative to the standard…
Co-ordinated VLA and EXOSAT observations of the flrae stars UV Ceti, EQ Pegasi, YZ Canis Minoris and AD Leonis.
Pallavicini, R.; Kundu, M. R.; White, S. M. +1 more
The authors have observed four flare stars (UV Cet, EQ Peg, YZ CMi and AD Leo) simultaneously with the VLA and the EXOSAT satellite over continuous periods of 7 - 10 h. This is the first time that flare stars were observed simultaneously in X-rays and at microwave frequencies with high sensitivity instrumentation. All stars were detected both at t…
Time variability in the X-ray emission of dM stars observed by EXOSAT.
Schmitt, J. H. M. M.; Pasquini, L.; Collura, A.
The authors studied the variability in the X-ray emission of 13 dMe stars observed with the LE+CMA onboard EXOSAT. The basic aim of this paper is to search for frequently occurring impulsive events with small energy releases in an effort to find out whether the "quiescent" X-ray emission from dM stars is really quiescent. The authors do not find, …
Rotational modulation and flares on RS CVn and BY DRA stars. IX. IUE spectroscopy and photometry of II Peg and V711 Tau during February 1983.
Linsky, J. L.; Catalano, S.; Rodono, M. +11 more
Evidence is presented for spots, plages, and flares on the noneclipsing RS CVn system II Peg and V 711 Tau. The large spot originally found on II Peg in 1981.8 could still be identified in 1983. Two spectroscopic flares of II Peg were detected. For the larger flare the fluxes in the strongest transition-region lines reached about six times their q…
IUE low resolution observations of the symbiotic star CH Cygni in 1979-1986.
Hack, M.; Mikolajewska, J.; Selvelli, P. L.
Data from IUE observations of the semiregular variable CH Cyg are presented compiled in extensive tables and graphs and analyzed with reference to theoretical models. The UV/optical continuum emission is accounted for by combining a Kurucz (1979) low-gravity A-type model atmosphere at Te = 8500-9000 K with hydrogen bound-free + free-free emission …
A correlation between Balmer and soft X-ray emission from stellar andsolar flares.
Foing, B. H.; Rodono, M.; Butler, C. J.
Simultaneous optical spectroscopy and X-ray monitoring of stellar and solar flares shows that a well-defined linear correlation exists between the integrated Hγ and soft X-ray flux that extends over four orders of magnitude. The existence of this relationship implies a direct proportionality between the emission from the cooler and denser regions …
The optical and UV spectrum of the Seyfert type 2 galaxy NGC 3393.
Prieto, M. A.; Wamsteker, W.; Diaz, A. I.
The combined UV and optical spectrum of the Seyfert type 2 galaxy NGC 3393 is presented and analyzed together with published IR and IRAS data. The conditions in the narrow line gas strongly suggest that the high ionization material is in a zone of higher density (N_e_=10^5^ cm^-3^) while the low ionization material is at N_e_=10^3^ cm^-3^. No evid…
New constraints on neutron star models of gamma-ray bursts. I. EXOSATobservations of two gamma-ray burst error boxes.
Hurley, K.; Boer, M.; Niel, M. +13 more
Two EXOSAT observations of gamma-ray burst error boxes and their possibly associated optical transients are discussed. No point source was detected in either box. A comparison with Einstein data (Pizzichini et al., 1986) is made for one of them (November 19, 1978). The data are interpreted in the framework of neutron star models for gamma-ray burs…
Rotational modulation and flares on RS CVn and BY DRA systems. VIII. Simultaneous EXOSAT and H alpha observations of a flare on the dMe star GL 644 AB (Wolf 630) on 24/25 August 1985.
Tagliaferri, G.; de La Reza, R.; White, N. E. +5 more
A large flare was detected simultaneously in X-rays and H-alpha on the visual binary Gl 644 AB at about 00:15 UT on August 25, 1985. The flare was detected with both the low (0.05-2 keV) and medium energy (2-7 keV) experiments onboard Exosat, with the flare rise time being similar in both the low and medium energy ranges, although in the low energ…
A 23h EXOSAT observation of the X-ray pulsar 1E 2259+586 and the associated supernova remnant G 109.1-1.0
Coe, M. J.; Dennerl, K.; Hanson, C. G. +1 more
The X-ray pulsar, 1E 2259+586, and the associated supernova remnant, G 109.1-1.0 were observed with the EXOSAT on 1984 December 1/2. The pulse period at this epoch was 6.978720±0.000006(1σ) s, indicating that between 1981 and 1984 the pulsar was spinning down with an average secular rate of change of the spin period given by P/P = +[3.3±0.2]×10