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Activity in late-type stars. VII. Chromospheric and transition region line fluxes in 2 dM and dM(e) stars.
Doyle, J. G.; Byrne, P. B.
Ultraviolet spectra of the two dM stars Gl380 and Gl411 and the dM(e) Gl900 are presented. The dM stars show mean surface fluxes in a variety of emission lines arising throughout the chromosphere and the lower transition region which are very similar to those of the quiet sun. In the one star in which it could be determined the electron density at…
CO Observations of the Cepheus Flare. II. Gamma Rays from the Interstellar Gas and a Possible New COS B Source
Grenier, I. A.; Lebrun, F.
The correlation between the distribution of the interstellar gas in the Cepheus Flare region (100^deg^ <= l <= 141^deg^, 8^deg^ <= b <= 22^deg^) and that of the diffuse gamma radiation originating in these nearby clouds has been studied in detail. A maximum-likelihood analysis has been applied to compare maps of the atomic and molecula…
EXOSAT observation toward S 147 and A 0535+26.
Ballet, J.; Rothenflug, R.; Sauvageot, J. L.
Observations have been made in the direction of the old SNR S 147 with the X-ray satellite Exosat. No emission was detected with the low-energy experiment, constraining the SNR parameters (energy and ambient density) for a Sedov model or a radiative one. A weak source was detected with the medium-energy experiment which could be associated with th…
Massa's Star, HD 93840: A New Extreme BN Supergiant
Walborn, Nolan R.; Nichols-Bohlin, Joy; Fitzpatrick, Edward L.
New optical digital spectrograms of HD 93840 and several comparison objects are presented and discussed, together with IUE high-resolution data for the same stars. The optical observations confirm HD 93840 (BN1 Ib) as an extreme nitrogen-enhanced supergiant, as originally suggested by Massa (1989). The contrasts with HD 96248 (BC1.5 Iab) are espec…
Similarities in the wind characteristics of hot stars.
Prinja, R. K.
The direct observational similarities in the characteristics of winds in a wide selection of hot stars are considered. Data are presented which demonstrate that discrete absorption components are observed in the UV resonance line profiles of WR stars, WR + O type binaries, B supergiants, B emission-line stars, subdwarf O stars, and the central sta…
Mesures de vitesses radiales. IV. Accompagnement AU sol du programme d'observation du satellite Hipparcos.
Duflot, M.; Genty, V.; Mannone, C. +1 more
The paper presents 396 radial velocities of stars distributed in 19 fields of 4 x 4 degrees. The study employs the Fehrenbach objective prism method and the same measuring technique used in a previous paper (Fehrenbach et al., 1987).
Rapid Line Variations in the Far-Ultraviolet Spectrum of 21 Com. I. The 1979 Event
Monier, R.
An analysis of archival IUE spectra of 21 Com revealed an instance of large and rapid flux variations on a time scale of 1 hr which occurred on November 15, 1979. Deep and broad features developed in less than 60 min and vanished in about 45 min shortwards of 1720 A. The 1979 event is thought to reflect a transient and abrupt change in the outer l…
HD 43246 and HD 127208: Two Unusual F-G + B Binary Systems
Parsons, Sidney B.; Fekel, Francis C.; Dempsey, Robert C. +1 more
New optical spectroscopic observations along with ultraviolet IUE observations have been obtained for the two interacting F or G III + B V binaries: HD 43246 and HD 127208. Photometric observations indicate random changes superimposed on regular ellipsoidal light variations, the latter probably the result of tidal distortion of the giant primaries…
EXOSAT Observations of the Blazar PKS 1510-089
Singh, K. P.; Rao, A. R.; Vahia, M. N.
A detailed study of X-ray emission from the high-polarization quasar PKS 1510-089, also known as a blazar, is presented, based on the EXOSAT observations in 1984 and 1985. The data were obtained from the EXOSAT archives. There is no evidence for any variations in the X-ray intensity on hourly time scales during either of the two observations. The …
X-ray observations of the radio galaxy Pictor A.
Singh, K. P.; Rao, A. R.; Vahia, M. N.
strong X-ray emission is detected from the active nucleus of an emission- line radio galaxy Pictor A, during observations with the EXOSAT observatory. The nuclear X-ray emission is observed to be steady on time- scales of a few minutes to a few hours. The X-ray spectrum is adequately explained by a simple power law with the photon index {GAMMA} = …