Search Publications
Analysis of the DA white dwarf HZ 43A and its companion star.
Werner, K.; Jordan, S.; Barstow, M. A. +3 more
The DA white dwarf HZ 43 A (WD 1314+293) is analyzed based on a newly obtained optical spectrogram. We demonstrate that the derived parameters Teff = 49.000 K and log g = 7.7 are in agreement with the observed Ly-alpha line, the slope of the UV continuum, and the measured trigonometric parallax. The EXOSAT spectrograms of Paerels et al.…
The discovery and properties of the ultra-soft X-ray transient EXO 1846-031.
Parmar, A. N.; White, N. E.; Angelini, L. +1 more
We report the discovery of a previously uncataloged ultra-soft X-ray transient EXO 1846-031 which was in outburst during 1985 April to September. The X-ray spectrum consists of an ultra-soft component and a high-energy power-law tail that extends to at least 25 keV. The ultra-soft component may be modeled by either a cutoff power-law or a multicol…
The X-ray time variability and spectrum of gamma Cassiopeiae (X 0053+604).
Stella, L.; Parmar, A. N.; White, N. E. +1 more
A 30 h duration EXOSAT observation made in 1985 December is used to examine the X-ray time variability and spectrum of the Be star γ Cassiopeiae (X 0053+604). We find that the X-ray lightcurve is dominated by irregular energy-independent flaring on time-scales ≳ 100 s. This flaring markedly decreases the sensitivity to any periodic signals. We fin…
Compton modelling of spectral variations observed in Z sources.
Wijers, R. A. M. J.; Schulz, N. S.
We present a simple model to fit the spectra of Z sources: a neutron star radiating at the centre of a hot scattering cloud. It is shown that the EXOSAT data of GX 17+2, GX 5-1, GX 340+0, and Sco X-2 (GX 349+2) in all branches of their Z profiles are represented well by this model. The neutron star temperature increases from the Horizontal Branch …
Variability of the Seyfert galaxy MKN 766 in the ROSAT all sky survey.
Molendi, S.; Maccacaro, T.; Schaeidt, S.
Results are presented from the ROSAT All Sky Survey (RASS) observation of the Seyfert galaxy Mkn 766. Using a technique specifically developed for the analysis of point sources in the RASS we show that Mkn 766 is highly variable. Comparison of the soft X-ray spectrum (0.1-2 keV) with EXOSAT Medium Energy archive data (2-10 keV) clearly shows that …
On the nature of the 25-min periodicity from 4U 0142+614 : a nearby, slowly spinning neutron star/Be system ?
Mereghetti, S.; Stella, L.; de Nile, F.
The unidentified X-ray source 4U 0142+614 has an unusually soft spectrum and has shown a periodic modulation at approximately 25 minutes, which could be interpreted as the orbital period of a Low Mass X-ray Binary. Recently a new X-ray source, probably a Be/neutron star system, has been discovered at an angular distance of only 24 arcmin from 4U 0…
Hard X-ray spectrum of 4U 1907+09.
Rao, A. R.; Chitnis, V. R.; Agrawal, P. C. +1 more
We have studied the binary X-ray source 4U 1907+09 in the energy range 20-100 keV, using a xenon-filled multilayer proportional counter telescope flown with balloons from Hyderabad in 1985 and 1991. Results of these observations are reported. The source was detected above 20 keV at a significance level of 13 sigma in 1985 and marginally detected i…
The nature of the X-ray spectrum of VW Hydri.
Verbunt, Frank; van Teeseling, Andre; Heise, John
We analyze the EXOSAT data of the October 1984 superoutburst of the dwarf nova VW Hydri. We use the upper limit to the flux at 650 A, measured by VOYAGER, to argue that the spectral component that dominates at 1000 A does not significantly contribute to the counts in any of the EXOSAT filters. This is confirmed by analysis of a flux-ratio diagram,…
An extended correlation between the Balmer and soft X-ray emission from solar and stellar flares.
Butler, C. J.
The integrated soft X-ray (8-12 Å) fluxes for solar flares, given by Thomas & Teske (1971), have been scaled to the equivalent EXOSAT (0.04-2.0 keV) fluxes using spectra obtained from a variety of rocket-based experiments and a model by Mewe for a 1.5 keV plasma. The data show good agreement with the soft X-ray-Hγ correlation established earli…
The X Persei system in the ROSAT all-sky survey.
Mavromatakis, F.
We report the analysis of soft X-ray data from the X-ray pulsar 4U 0352+30, taken by the ROSAT satellite. The mean luminosity, in the ROSAT bandpass (0.1-2.4 keV), is 6 × 1O33 d2kpc erg s-1 and is consistent with that usually seen in the soft X-ray band. The energy spectrum can be described by a flat pow…