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Is PKS 2155 an extragalactic source?

Maraschi, L.; Tanzi, E. G.; Tarenghi, M. +1 more

The X-ray source H2155-304, identified with the radio source PKS 2155 and with a 14 mag star-like object, is commonly believed to be a BL Lac object on the basis of the blue featureless continuum, the presence of optical polarization, and the violent variability (m_B varies from 12.8 to 14.2 on a time scale of months). This paper present…

IUE high-dispersion spectrum of R Aqr.

Johnson, H. M.

Emission-line spectra of several ions were observed in R Aqr in the wavelength range 1900-3000 A. C II diagnostics gives an electron density of about 400,000/cu cm and an electron temperature of about 10,000 K. The Mg II doublet profiles are grossly asymmetric, of a P Cygni type with terminal ejection velocity of at least 200 km/s. This is like Mg…

History of the gamma-ray light curves of the pulsars PSR0531 plus 21 and PSR0833-45 as measured by COS-B

Caraveo, P. A.; Bignami, G. F.; Hermsen, W. +7 more

On the Evidence for High Energy γ -ray Emission from the Orion Nebula Stemming from COS-B Observations

Caraveo, P. A.

The E.S.A. COS-B satellite performed a one-month observation pointing in the direction of M42 in Orion, during July-August 1978. An excess of high energy (above 100 MeV) photons is seen in the data, well coinciding with the Orion cloud complex. Features of such an excess are discussed, such as flux value, spectral shape and possible spatial extens…

The transition region structure of kap Cet.

Rego, M.; Fernandez-Figueroa, M. J.; de Castro, E.

Ultraviolet emission lines of Kappa Ceti (HD 20630), obtained with the IUE satellite, are analyzed in order to study the higher chromospheric, transition region and the low corona structure. Three models are derived for the emission measurement distribution, and the best fit model has a pressure of log P_e equals 14.96 at log T_e

Molecular hydrogen ion (H2+) absorption in planetary nebulae.

Feibelman, W. A.; Hobbs, R. W.; Boggess, A. +1 more

Several IUE spectra of planetary nebulae show an absorption feature shortward of 1500 A which is believed to be due to H2(+). The nebulae are excited by stars of spectral type O3-O7 or continuum, and all but one have double-shell structure.

UV observations of the intermediate helium star CPD -46 3093.

Heber, U.; Hunger, K.

UV spectrograms of CPD-46 deg 3093 have been obtained with IUE in low resolution. No evidence for mass loss can be found at this resolution. A synthetic spectrum, calculated in LTE and including 800 atomic transitions matches the observations. Also the UV Si III/Si IV ionization equilibrium is reproduced as well as the Stromgren colors. The atmosp…

Gamma ray astronomy with COS-B

Swanenburg, B. N.

Observational results in the field of gamma-ray astronomy that have been obtained to date with the COS-B satellite are discussed and questions raised by these observations are summarized. Following a brief review of the instrumental characteristics of COS-B and the extent of COS-B gamma-ray coverage of the sky, particular attention is given to the…

IUE observations of high-velocity components in spectra of beta Orionis.

Bates, B.; Giaretta, D. L.; Brown-Kerr, W.

The high dispersion spectrum of R CrB in the long wavelength obtained near its maximum with the International Ultraviolet Explorer shows the presence of chromospheric Mg II emission. For comparison the spectrum of γ Cyg was obtained immediately afterwards. The Mg II emission width of R CrB is found to be the same as that of γ Cyg.

The ultraviolet spectrum of UW Canis Majoris

Kondo, Y.; Drechsel, H.; Rahe, J. +1 more

High resolution spectra of the eclipsing binary UW CMa have been obtained in the wavelength range 950 to 3200 A with the Copernicus (OAO-3) and IUE satellites. UW CMa is an interacting system, consisting of an 07f Ia primary and an O-B secondary. The spectra have been used to compile a list of stellar and interstellar lines. Identifications togeth…