Search Publications
The EXOSAT medium-energy slew survey catalog
Parmar, A. N.; Pollock, A. M. T.; Taylor, B. G. +4 more
We present a catalog of X-ray sources observed during slew maneuvers by the Medium Energy Detector Array onboard the EXOSAT Observatory. The EXOSAT Medium Energy slew-survey catalog (EXMS) provides a unique record of the 1-8 keV X-ray sky between 1983 and 1986. 98% of the sky was observed, with 85% receiving an exposure of >60 s. 1210 sources w…
F, G and K stars in the ROSAT all-sky survey. I. Photometry
Pasquini, L.; Krautter, J.; Cutispoto, G. +2 more
We present accurate BV(RI)_c photometry for a sample of F, G and K stars detected in selected areas of the ROSAT all-sky survey (RASS). We have used the photometry, in addition to low-resolution spectroscopy, to estimate spectral classifications, distances and X-ray luminosities. The log (L_X / L_V) in the sample lies below -2. Although the sample…
Analyzing X-ray variability by linear state space models
Timmer, J.; Konig, M.
In recent years, autoregressive models have had a profound impact on the description of astronomical time series as the observation of a stochastic process. These methods have advantages compared with common Fourier techniques concerning their inherent stationarity and physical background. However, if autoregressive models are used, it has to be t…
Photometric and spectroscopic studies of cool stars discovered in EXOSAT X-ray images. III. Photometric properties.
Tagliaferri, G.; Pasquini, L.; Pallavicini, R. +2 more
We present high-precision UBV(RI)_c_ photometry for a sample of active stars detected serendipitously by the EXOSAT satellite. Fourteen objects, out of 47 likely optical counterparts, turned out to be clearly variable, with periods in the range 1-8 days, including a newly discovered eclipsing binary. For most of them the optical variability is con…
The canonical X-ray/gamma-ray spectrum of Seyfert 1s and low-state Galactic black hole candidates.
Zdziarski, A. A.; Magdziarz, P.; Gierlinski, M. +1 more
We review broad-band X-ray/γ-ray spectra of radio-quiet Seyfert 1s as well as of Galactic black hole candidates in the low state. The spectra share their basic components: an underlying power law, a Compton-reflection component with an Fe Kα line, low-energy absorption by cold matter, and a high-energy cutoff above ~200keV. The X-ray energy spectr…
X-ray map from the EXOSAT galactic plane survey and a direct demodulation technique.
Lu, F. J.; Li, T. P.; Page, C. G. +2 more
In 1984 the EXOSAT observatory scanned the galactic plane with its medium-energy array which had a spatial resolution of about 0.75deg. The data analysis used at that time was unable to resolve some of the more complex regions near the galactic centre. The direct demodulation method is a technique to solve the image reconstruction problem in high …
Radio to X-ray energy distribution of BL Lacertae objects.
Giommi, P.; Micol, A.; Ansari, S. G.
We present multifrequency spectra of a large number of radio and X-ray selected BL Lacertae objects constructed using non-simultaneous archival data. The data were obtained using the European Space Information System (ESIS) and are from several radio and optical catalogues, the IRAS Faint Source Catalogue, the Einstein and the EXOSAT databases. Th…
The EXOSAT GSPC iron line catalog.
Parmar, A. N.; White, N. E.; Taylor, B. G. +3 more
We report on the global properties of the Fe feature seen in the 6-7keV spectra of X-ray sources observed with the EXOSAT Gas Scintillation Proportional Counter (GSPC). Of a total of 431 spectra extracted from the EXOSAT archive, 205 required the addition of a Gaussian emission line to the continuum spectrum in order to obtain satisfactory fits. T…
X-ray observations of flat spectrum radio sources with the HEAO-A, Einstein and EXOSAT observatories.
Pietsch, W.; Schaaf, R.; Witzel, A. +3 more
This paper presents X-ray data collected with the satellites HEAO-A, EINSTEIN (HEAO-B) and EXOSAT for flat spectrum radio sources. Most of the sources are from a complete sample of the high-declination 5 GHz survey.
Photometric and spectroscopic studies of cool stars discovered in EXOSAT X-ray images. I. Time variability and spectral classification of eight southern stars.
Tagliaferri, G.; Pasquini, L.; Pallavicini, R. +4 more
As part of a larger program to study the optical properties of serendipitous Exosat sources, optical photometry and low-resolution spectroscopy are presented for eight southern stars which have been identified as optical counterparts of Exosat sources. X-ray flux variability has been detected for three of them. In all three cases the optical count…