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EXOSAT Observations of the Cassiopeia A Supernova Remnant
White, N. E.; Jansen, F.; Smith, A. +3 more
The young supernova remnant Cas A has been observed with the European X-ray observatory satellite Exosat. The remnant was observed with all instruments covering the range from 0.5 to 25 KeV. It is shown here that the emission from the remnant cannot be described by a two-temperature isothermal plasma in collisional ionization equilibrium. A simple…
Contemporaneous X-Ray and VLBI Radio Observations of the Quasar NRAO 140
Marscher, Alan P.
The quasar NRAO 140 was observed at various times between 1978 and 1985 at X-ray energies using HEAO I, the Einstein Observatory, and EXOSAT. The author also observed this source a number of times with multifrequency VLBI between 1980 and 1984. In this paper, the author combines new observations with those previously published to present a time hi…
EXOSAT Observations of the Supernova Remnant G109.1-1.0 and the X-Ray Pulsar 1E 2259+586
van der Klis, M.; Robba, N. R.; Smith, A. +1 more
The authors report on the EXOSAT observation of the supernova remnant (SNR) G109.1-1.0+1E 2259+586 system. The spatial distribution of the X-ray emission as derived from the low-energy (<2 keV) data is very similar to that obtained from the Einstein Observatory. The various components of the source (SNR shell, pulsar, and jet) have different sp…
Interstellar Absorption Lines in High-Resolution IUE Spectra of Cataclysmic Variables
Raymond, John C.; Mauche, Christopher W.; Cordova, France A.
High-resolution ultraviolet spectra of five cataclysmic variables obtained with the IUE are used to investigate the character of the interstellar medium in the vicinity of the sun. These spectra reveal narrow absorption features of neutral and singly ionized interstellar species, and, in SS Cyg, narrow velocity-shifted absorption features of C IV,…
The Carbon Chemistry in Interstellar Clouds toward Moderately Reddened Stars
Lambert, D. L.; Federman, S. R.
New data for C2 toward X Per, HD 206267, HD 207198, and Gamma Cep, for CH and CN toward X Per, and for CO toward HD 207198 have been obtained. The column densities of CH, C2, CN, and CO toward the stars in the Cepheus OB2 association are similar to reddened directions in Perseus and in Ophiuchus, indicating a similarity in physical conditions for …
Improved Bow Shock Models for Herbig-Haro Objects: Application to HH 2A
Hartigan, Patrick; Raymond, John C.; Hartmann, Lee
An improved version of the bow shock theory previously applied to Herbig-Haro objects is presented. The modifications provide a more accurate calculation of the ionization state of material entering the bow shock. The revised preionization does not drastically affect the emission-line predictions for a 200 km/s bow shock model, though the effects …
Quasi-periodic Oscillations in the X-Ray Flux of the Rapid Burster (MXB 1730-335)
Haberl, F.; Stella, L.; Parmar, A. N. +3 more
The authors report on the results of an EXOSAT observation of the "Rapid Burster" in 1985 August during an active state. Forty 1 - 10 minute long type 2 bursts were detected together with persistent emission. Quasi-periodic oscillations (QPO) were observed in 23 bursts with frequencies between 2 and 5 Hz. The average frequency of the QPO during th…
The Discovery of the 2 Hour Modulated X-Ray Source EXO 033319-2554.2, an AM Herculis System
Tagliaferri, G.; Stella, L.; Giommi, P. +2 more
The authors report the discovery of EXO 033319-2554.2, a soft X-ray source with 100% modulation of its soft X-ray flux, found during a systematic analysis of all of the EXOSAT soft X-ray data. The soft X-ray light curve, which has an on-off behavior, shows a period of 127.7±3.0 minutes. The bright part of the cycle lasts 0.55 in phase and is cut b…
High-Velocity Ultraviolet Iron, Silicon, Oxygen, and Sulfur Absorption Features Associated with the Remnant of SN 1006
Fesen, Robert A.; Wu, Chi-Chao; Hamilton, Andrew J. S. +1 more
New low-dispersion IUE spectra of a faint sdOb star located in a direction near the center of the SN 1006 remnant are presented. The UV spectrum of the star exhibits several strong absorption features which are uncharacteristic of its optical sdOB star classification. The identification by Wu et al. (1983) of very broad absorption features at 1610…
Mass Loss in a B2 IIIe Star: omega Orionis 1978--1984
Sonneborn, George; Grady, C. A.; Guinan, E. F. +4 more
Combination of long-term optical polarimetric, photometric, spectrometric, and ultraviolet spectral data have confirmed that all observed portions of ω Ori's outer atmosphere are variable on a variety of time scales. The spectacular polarization episodes are correlated with the presence of continuum flux and color changes but are not correlated wi…