We report the discovery of a new cataclysmic binary star from the ROSAT Galactic Plane Survey. The star has V >∼ 18.5 at minimum light and we have measured it as bright as V = 15.7. Spectroscopy shows broad hydrogen and helium emission lines; HeII λ4686 is not detected. Hα radial velocities yield an orbital period of 0.1429 ± 0.0004 d (3.430 ± 0.010 h). Timeseries photometry covering one orbita...

We have developed a method based on wavelet transforms (WT) to detect sources in ROSAT PSPC X-ray images. The WT, evaluated at a set of scale parameters a, detects eeciently both point-like and extended sources. This method is especially suitable when the PSF width changes strongly across the eld of view as in PSPC images. The reliability of the algorithm is ensured even in the presence of stro...

During a systematic search for periodic signals in a sample of ROSAT PSPC light curves, we discovered ∼ 8.9 s X–ray pulsations in 2E0050.1–7247, a variable X–ray source in the Small Magellanic Cloud. The source was detected several times between 1979 and 1993 at luminosity levels ranging from ∼ 5 × 10 erg s up to 1.4 × 10 erg s with both the Einstein IPC and ROSAT PSPC. The X–ray energy spectru...

We report on 40 kiloseconds of ROSAT HRI observations of the globular cluster M92 (NGC 6341) and 20 kiloseconds of observations of the globular cluster M13 (NGC 6205). We find that the low-luminosity (10 erg sec at 7.5 kpc) source previously observed near the core of M92 with the ROSAT PSPC remains unresolved at HRI resolution; we can identify it with M92 with 99 per cent confidence. In M13 we ...

A probabilistic technique for the joint estimation of background and sources in high-energy astrophysics is described. Bayesian inference is applied to gain insight into the coexistence of background and sources through a probabilistic two-component mixture model, which provides consistent uncertainties of background and sources. The present analysis is applied on ROSAT PSPC data in Survey Mode...

We present results of ROSAT/PSPC and HRI observations of the AWM7 group of galaxies, which is a poor galaxy cluster and forms part of the Perseus-Pisces lament. The X-ray emission originates from intracluster gas at temperatures of 1.7 to 4.5 keV. The cluster obviously is elliptical with a position angle perpendicular to the position angle of the dominant elliptical galaxy NGC1129, which is oos...

We present a new method that uses the Mexican Hat wavelet transform in a particularly simple manner to detect X-ray sources. We use an iterative approach to correlate data with the Mexican Hat function and to cleanse suspected sources from the data. This allows us to estimate the background and specify a threshold for source detection in the correlation map of the original (uncleansed) data. Th...