Search Publications
Variability pattern from X-ray to IR wavelengths in the active nucleus ofNGC 1566.
Alloin, D.; Pelat, D.; Baribaud, T. +1 more
This study presents the results of a multiwavelength monitoring of the active galactic nucleus in NGC 1566. Data collected in the X-rays, ultraviolet, visible and near-infrared domains have been combined together, in order to disentangle the various components and to better understand the patterns of variability in this active nucleus. At all wave…
Periodic outbursts in the peculiar X-ray binary 2S 0114+65.
Belloni, T.; Finley, J. P.; Cassinelli, J. P.
The peculiar X-ray binary system 2S 0114 + 65 has been observed by every X-ray satellite mission since its discovery by SAS 3 in 1977. A persistent feature of all the observations are outbursts on a time scale of about 3 hr. We have utilized the archival EXOSAT data, as well as published data and ROSAT all-sky survey data and show that the observe…
The origin of the X-ray emission in 3C 273 and 3C 120.
Walter, R.; Courvoisier, T. J. -L.
We present an analysis of simultaneous X-ray and ultraviolet observations of the two quasars 3C 273 and 3C 120 which exhibit very similar multi-waveband spectra. This investigation is limited to the long term variations observed in the two spectral bands and to their correlations. In both objects, the X-ray and ultraviolet lightcurves are not coup…
The X-ray variability of the Seyfert galaxy NGC 6814.
Fiore, F.; Massaro, E.; Barone, P.
We present the results of an accurate temporal analysis of five EXOSAT observations of the Seyfert 1 galaxy NGC 6814 covering about 2 yr. As firstly reported by Mittaz & Branduardi-Raymont (1989), the power spectrum of the longest (~1 d) observation is characterized by two major components: a low frequency noise which can be described, in the …
X-ray variability in a sample of Seyfert 1 type AGN.
Walter, R.; Courvoisier, T. J. -L.
X-ray observations of several Seyfert 1 type AGN observed many times with EXOSAT are presented and analysed. The spectral parameters are extracted independently in the medium and soft X-ray spectral ranges. The variations observed in the two spectral bands and their relation are discussed and compared to the spectral variations observed in other w…
X-ray spectrum of NGC 3783 : detection of soft excess and an emission line.
Ghosh, K. K.; Soundararajaperumal, S.; Sivarani, T. +1 more
Results of the X-ray (0.1-10 keV) spectral analysis of the Seyfert I galaxy, NGC 3783, which was observed with EXOSAT on three epochs between 1983 and 1985, are presented here. No low energy absorption, intrinsic to the source, was found in this galaxy and the spectral index of the power law fit did not vary during the EXOSAT observations. Soft ex…
First X-ray spectrum of the most luminous quasar PKS 2126-158.
Ghosh, K. K.; Soundararajaperumal, S.
For the first time the detailed results of the spectral analysis of the X-ray (0.1-10 keV) spectrum of the luminous (z = 3.27), radio-loud quasar, PKS 2126 - 158, are presented. The spectrum of this quasar was obtained from the EXOSAT database. Power law and fixed absorption model fits well with the spectrum. The parameters of this model suggest t…
EXOSAT measurement of the spectrum of Markarian 382.
Singh, K. P.; Rao, A. R.; Vahia, M. N.
The 0.1-10 keV X-ray spectrum of a Seyfert galaxy known as Markarian 382 (Mkn 382) is presented based on observations with the EXOSAT. The energy index (α) for the power-law X-ray continuum of Mkn 382 is measured to be 1.2^+0.16^_0.14_ which is higher than the canonical value found for the Seyfert galaxies. There is no evidence for intrinsic absor…