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The Transient 42 Second X-Ray Pulsar EXO 2030+375. I. The Discovery and the Luminosity Dependence of the Pulse Period Variations
Stella, L.; Parmar, A. N.; White, N. E. +2 more
The discovery of a new transient X-ray pulsar, EXO 2030+375, that is associated with a Be star companion, is reported. The results of a series of EXOSAT observations, where the evolution of the pulsar's properties over two orders of magnitude in luminosity was monitored. The dependence of the change in pulsar period on luminosity is measured and c…
The Transient 42 Second X-Ray Pulsar EXO 2030+375. II. The Luminosity Dependence of the Pulse Profile
Stella, L.; Parmar, A. N.; White, N. E.
During an outburst from the transient, 42 s, X-ray pulsar EXO 2030+375, marked luminosity-dependent changes in pulsar profile were observed. At high luminosities the pulse profile consisted of a smooth asymmetric main pulse separated by about 180 deg in phase from a small interpulse. As the luminosity decreased by a factor of about 100, the relati…
Coronal Activity in F-, G-, and K-Type Stars. III. The Coronal Differential Emission Measure Distribution of Capella, sigma 2 Coronae Borealis, and Procyon
Mewe, R.; Schrijver, C. J.; Lemen, J. R. +1 more
EXOSAT soft X-ray spectra of three binary systems of cool stars are analyzed: Capella (G6 III + F9 III), Sigma-squared CrB (F8 V + G1 V), and Procyon (F5 IV-V + DF). The EXOSAT transmission grating spectrometer permits the study of individual spectral lines and line complexes between 10 and 200 A with approximately 3 A resolution. First it is demo…
The Discovery of 0.2 HZ Quasi-periodic Oscillations in the X-Ray Flux of the Transient 42 Second Pulsar EXO 2030+374
Stella, L.; Parmar, A. N.; Angelini, L.
The discovery of about 0.2 Hz quasi-periodic oscillations (QPOs) in the 1-15 keV X-ray flux of the transient 42 s pulsar EXO 2030 + 375 is reported. The detection of QPOs in the power spectra of this pulsar was made possible by the application of a newly developed technique to decouple the power spectrum peaks. QPOs were detected during an outburs…
An EXOSAT X-Ray Observation of One Orbital Cycle of 4U 1700-37/HD 153919
Haberl, F.; White, N. E.; Kallman, T. R.
Exosat observations of close to one complete binary cycle of 4U 1700-37/HD 153919 are presented, and X-ray absorption variations are determined as a function of orbital phase in order to study the properties of the stellar wind of the companion HD 153919. The decrease noted in absorption between eclipse egress and phase 0.5 may be due to X-rays fr…
X-Ray Observations of the Starburst Galaxy M82
Pietsch, W.; Schaaf, R.; Kronberg, P. P. +2 more
We report here on long (~ 10^5^ s) X-ray observations of the starburst galaxy M82 with the European X-ray satellite EXOSAT. The observations with the low-energy imaging instrument confirm that there is extended X-ray emission from above and below the disk, with an overall extent perpendicular to the disk of almost 6' corresponding to 6 kpc. We pre…
A Soft X-Ray Survey of Hot White Dwarfs with EXOSAT
Heise, J.; Paerels, F. B. S.
Broadband multicolor soft X-ray photometry of 34 hot white dwarfs is presented, obtained with the Low Energy Imaging Telescopes on Exosat. By combining the soft X-ray fluxes with measurements of the stellar parameters in the UV and optical bands, photospheric He abundances for 16 of the 21 hot DA white dwarfs are derived. Supplemented by five star…
Simultaneous X-Ray, Ultraviolet, and Optical Observations of the BL Lacertae Object PKS 2155-304
Maccagni, D.; Maraschi, L.; Tanzi, E. G. +6 more
X-ray observations of PKS 2155-304, performed at nine epochs in 1983-1985 with the EXOSAT satellite, are reported. The source was observed quasi-simultaneously in the far-UV with IUE, and in the optical and infrared with ESO telescopes. X-ray light curves with 400 s time resolution are derived. On two occasions the flux showed a rapid regular risi…
Two X-Ray--selected BL Lacertae Objects Observed with the HEAO 1 Scanning Modulation Collimator
Buckley, D. A. H.; Schwartz, D. A.; Tapia, S. +4 more
We have discovered two 16th magnitude BL Lac objects, H1101-232 and H1426+428, during an ongoing program to identify the optical counterparts of X-ray sources from the HEAO 1 survey. Each is a persistent and relatively bright X-ray source that was also detected by the Uhuru and Ariel 5 surveys. Our classifications are based on the combined observa…
Coronal Activity in F-, G-, and K-Type Stars. IV. Evidence for Expanding Loop Geometries in Stellar Coronae
Mewe, R.; Schrijver, C. J.; Lemen, J. R.
A detailed analysis is presented of X-ray spectra of Capella and of Sigma2 CrB. The spectra of both stars are compatible with coronae consisting of two different ensembles of static loops with different maximum temperatures and ratios of the cross sectional areas at the loop top and at the footpoint. The cool (5 MK) loop components in both stars s…