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X-Ray Variability of the Bright Bl-Lacertae Object PKS2155-304
Maccagni, D.; Maraschi, L.; Tanzi, E. G. +3 more
We have observed the BL Lac object PKS 2155-304 with the EXOSAT observatory and with IUE on 1983 October 31 and November 29. At the same time, optical photometry has been obtained. Variability has been observed both on a time scale of hours during the October 31 observation and on the time scale of one month. During the November 29 observation the…
The soft X-ray spectrum of NGC 4151
Culhane, J. L.; Warwick, R. S.; Pounds, K. A. +1 more
EXOSAT observations of the Seyfert galaxy NGC 4151 over the period July 1983 to April 1984 have revealed a decreasing flux in the 2 10 keV band. In accord with previous measurements a power law spectrum attenuated with a simple column of cold gas does not provide a satisfactory spectral fit below ∼3 keV, where a lower relative opacity is required.…
EXOSAT Observations of Late-Type Stars - the Application of Coronal Loop Models
Monsignori-Fossi, B. C.; Landini, M.; Pallavicini, R.
We apply solar-type coronal loop models to X-ray and UV observations of late-type stars. We derive from EXOSAT and IUE observations constraints on the temperature, pressure and size of the emitting structures.
Thermal radiation from a radio pulsar PSR 1055-52
Aschenbach, B.; Brinkmann, W.; Oegelman, H.
The radio pulsar PSR 1055 - 52 was studied in order to detect thermal radiation from the surface of a neutron star. Einstein satellite observations of PSR 1055 - 52 fitted to different spectra are described. These results and observations of an extended source around PSR 1055 - 52 were used by Cheng and Helfand (1983) to develop the theory of a sy…
EXOSAT 2 10 KeV observations of M87 and the Virgo cluster
Smith, A.; Stewart, G.
A series of observations of the Virgo cluster of galaxies with the Medium Energy experiment on board EXOSAT are presented. These take the form of two orthogonal scans meeting at M87. The observed count rates have been compared with those obtained with the IPC on board the EINSTEIN observatory and are found to be consistent with the the IPC surface…
EXOSAT Le-Canis Observations of the VELA Supernova Remnant
Smith, A.; Zimmermann, H. -U.
Presented here are Exosat LE1-CMA images of fields in the Vela SNR. Soft X-ray emission is observed in the north of the remnant indicating a filamentry structure. No X-ray emission was seen in two fields to the west and south-west which have optical filaments but were not studied by Einstein. The Vela pulsar is observed and is significantly broade…
EXOSAT Observations of the Iron Line Emission of HERCULES-X-1 during a 35-DAY Cycle
Pietsch, W.; Kahabka, P.; Truemper, J. +2 more
In March/April 1984 eleven EXOSAT observations of Her X-1 were performed sampling a full 35 day cycle. Spectral analysis of the ME and GSPC data shows that the iron line emission is present during all phases. During the main-on state we see an iron line at 6.65 ± 0.07 keV with a FWHM of 1 2 keV and an equivalent width of 300 to 400 eV. The high re…
CYG X-3: not Seen in High-Energy Gamma Rays by Cos-B
Caraveo, P. A.; Bignami, G. F.; Strong, A. W. +7 more
COS-B had Cyg X-3 within its field of view during 7 observation periods between 1975 and 1982 for in total approximately 300 days. In the skymaps (70 meV E 5000 meV) of the Cyg-X region produced for each of these observations and in the summed map, a broad complex structure is visible in the region 72 deg approximately less than 1 approximately le…
The nature of Weinberger-12.
Feibelman, W. A.; Kaler, J. B.
From IUE spectra of its central star, the authors conclude that Weinberger-12 is a small H II region, and not a planetary nebula. The star is substantially reddened with a color excess of 0m.75, is most likely a B0.5 - B1 giant or subgiant about three kpc distant, and possibly belongs to the Cas OB2 association.
Properties and Nature of Be Stars. 12. The UV Line Spectrum of KX And - Is There a Hot Primary?
Štefl, S.
Seven high-resolution IUE spectrograms of the Be star KX And were investigated by the standard method of comparison of the observed and theoretical spectra. The whole ultraviolet line spectrum can be described quite well by a model spectrum, corresponding to Kurucz's model with Teff = 9000 - 10000K and log g = 2.00. A detailed identific…