Search Publications
EXOSAT observations of Cygnus X-1 : study of the soft X-ray excess.
Hasinger, G.; Balucinska, M.
The paper presents results of a spectral analysis of the Cyg X-1 data collected during 1984-1985 by the Medium Energy instrument onboard the Exosat satellite. Emphasis is on two issues: the soft X-ray excess in the range below 3 keV and the iron-line intensity. The presence of a soft component in addition to the high-energy power-law component is …
A study of the flaring and quiscent X-ray and UV emission from II Pegasi.
Tagliaferri, G.; White, N. E.; Doyle, J. G. +3 more
An investigation has been conducted of the rotational modulation of the transition-region UV and coronal X-ray emission for the RS CVn system II Pegasi. The X-ray light curve is dominated by a strong flare detected at orbital phase, where the minimum of the photometric wave occurred. The flare parameters derived show that the flare originates with…
Scattering of X-rays on the winds of supergiant X-ray binaries.
Haberl, F.
Monte-Carlo simulations of Thomson scattering of X-rays in the stellar wind of OB stars in supergiant X-ray binaries show that at least part of the low-energy excess seen in the X-ray spectra during phases of high absorption can be explained by scattering of X-rays around a dense region in the wind obscuring the direct radiation. In the case of 4U…
EXOSAT observations of the X-ray burst source 4U 1702-42.
van Paradijs, J.; van der Klis, M.; Lewin, W. H. G. +2 more
The two Exosat observations of 4U 1702 - 42 are reported. In one of them three bursts are detected. The bursts and the spectral and fast-temporal behavior of the persistent emission are analyzed. It is concluded that 4U 1702 - 42 is an atoll source, which was in the banana state when the bursts were present. The characteristics of the burst are si…
Observations of X-ray spectra of two nearby QSO's : MRK 205 and MRK 1148.
Singh, K. P.; Rao, A. R.; Vahia, M. N.
The 0.1 - 10 keY X-ray spectra of two nearby quasistellar objects (QSO's) known as Markarian 205 (Mrk 205) and Mrk 1148 (PG 0049+171), are presented based on observations with the EXOSAT Observatory. Simple power law models with the line of sight absorption consistent with the values obtained from the 21 cm surveys are sufficient to explain the ob…
Quiscent and flaring X-rays from both Gliese 867A and Gliese 867B.
Tagliaferri, G.; Pallavicini, R.; Pollock, A. M. T.
X-ray observations of the flare-star binary system Gliese 867AB obtained with the Low Energy instrument on the Exosat Observatory were analyzed. By applying a likelihood method, it is shown that both components of the system were contributing to the observed X-ray emission with an intensity ratio A:B of about 3:1. It is also shown that X-ray flare…
The "noisy" pulsar in HER X-1.
Belloni, T.; Kahabka, P.; Hasinger, G.
The results of a comparative analysis of coherent and noncoherent variations in the X-ray emission of Hercules X-1 are presented, based on Exosat archive data. In the broad band power spectrum of the source a strong noise component, variable with the 35-days cycle, is present. These changes, and the relation between the noise rms and the pulsed rm…
X-ray spectrum of the radio-loud quasar PKS 1217+023.
Ghosh, K. K.; Soundararajaperumal, S.
A study of the X-ray (0.1-10 keV) spectrum from the radio-loud quasar, PKS 1217+023 is presented. This quasar was observed with EXOSAT on two epochs in 1984 January 29 and May 14. The data were obtained from the EXOSAT archives. The soft (0.1-2 keV) and hard (2-10 keV) X-ray fluxes have displayed significant changes between the two observations. T…
EXOSAT observations of the quasar PKS 2135-147
Singh, K. P.; Rao, A. R.; Vahia, M. N.
A study of X-ray emission from the low polarization quasar, PKS 2135-147 (PHL 1657), is presented based on the EXOSAT observations carried out on two occasions separated by a week in 1984. There is little evidence for any variations in the X-ray intensity on hourly time scales during either of the two observations. About 30% change in the soft X-r…
The soft X-ray variability of NGC 5548.
Kaastra, J. S.
The soft X-ray variability of NGC 5548 is studied using EXOSAT's low energy telescope in conjunction with the channel multiplyer array (CMA). For the first time, the pulse height distribution of the CMA data is used to infer information on the spectral variability. The spectrum of NGC 5548 consists of a hard power law and a soft component. During …