Tomography of polars

SIGLEAvailable from TIB Hannover: RR 7310(2000-27) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Magnetic fields and accretion streams in polars

The flow of matter, the accretion geometry and the energy release in polars (AM Herculis binaries) are to a large extent dominated by the strong magnetic field of the accreting white dwarf. In this review I summarize the main tools used to investigate the magnetic fields and the accretion streams, using optical and X-ray spectroscopy and photometry. (orig.)Available from TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Phase-resolved spectroscopy and photometry of the eclipsing polar EP Draconis (=H1907+690)

We present phase-resolved optical spectroscopy and CCD photometry of the faint eclipsing polar EP Dra (H1907+690). A revised ephemeris is derived which connects all 32000 binary cycles since its discovery by Remillard et al. (1991). We found no difference between spin and and orbital periods of the white dwarf. Changes in the light curve morphology are attributed to a different beaming behaviour which might change on timescales as short as one or several orbital periods. Optical light curve modelling was used to estimate the co-latitude of the accretion spot, which must be larger than 40 . We have detected Zeeman absorption lines of H#alpha# originating in an accretion halo in a field of 16 MG. The low-resolution spectra reveal no indication of resolved cyclotron harmonics, which is also suggestive of a relatively low field strength in the accretion region. The Balmer emission lines contain significant contributions from the UV-illuminated hemisphere of the companion star, whereas the HeII #lambda#4686 emission originates predominantly from the accretion stream. The emission lines have a multi-component structure and we could single out a narrow emission line in the H#beta# and H#gamma# lines. Its radial velocity amplitude suggests a low mass for the white dwarf, if the lines are interpreted as being of reprocessed origin from the whole illuminated hemisphere of the companion star. (orig.)Available from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Zeeman lines and a single cyclotron line in the low-accretion rate polar 1RXS JO12851.9-233931(RBS0206)

We present a low-resolution discovery spectrum and CCD-photometry of the bright X-ray source 1RXS J012851.9-233931 found in the ROSAT All-Sky Survey. These first observations suggest that the source is an AM Herculis star (polar) accreting at a low rate. The optical specturm is dominated by Zeeman absorption features from the white dwarf, indicating a mean photospheric magnetic field of 36#+-#1 MG. Only weak Balmer line emission was observed. In the near infra-red, a single intense cyclotron hump was observed. The inferred magnetic field strength in the accretion plasma is 45#+-#1 MG, the temperature in the plasma is below 2 keV. Likely orbital periods are #propor to#90min or #propor to#146 min, the latter inside the cataclysmic variable period gap. The system is an ideal target for further detailed investigations of the field structure on a magnetic white dwarf by phase-resolved spectropolarimetry. (orig.)SIGLEAvailable from TIB Hannover: RR 7310(99-21) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Photometry of the low accretion rate polar HS 1023+3900

SIGLEAvailable from TIB Hannover: RR 7310(2001-26) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

System parameters of the long-period polar V1309 Ori

SIGLEAvailable from TIB Hannover: RR 7310(2001-22) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Accretion stream mapping of HU Aqr

SIGLEAvailable from TIB Hannover: RR 7310(2000-25) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Accretion Stream Mapping

We present a new mapping algorithm, the accretion stream mapping, which uses the complete emission-line light curve to derive spatially resolved intensity distributions along the stream on a surface created as a duodecadon shaped tube. We successfully test this method on artificial data and then applied it to emission line light curves in H#beta#, H#gamma# and He II 4686 of the magnetic CV HU Aqr. We find Balmer emission near the threading point in the stream facing the white dwarf and helium emission all over the magnetic part of the stream. (orig.)Proceedings of the Annapolis workshop on magnetic cataclysmic variables (MCV2), 4 refs.Available from TIB Hannover: RR 7310(98-27) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

AGN/galaxy separation in the ROSAT bright survey

The X-ray luminosity function (XLF) of galaxies is dominated by AGN (classified by their optical spectra) above L_x = 10"4"2 erg s"-"1, below this value by normal galaxies. The X-ray flux of AGN at low X-ray luminosity therefore contains contributions from stellar processes (winds, supernova explosions etc.). Until now it is not clear which fraction of the observed X-ray flux has to be associated to the underlying stellar emission. We started to investigate a complete luminosity-limited sample of AGN and galaxies with log L_x#<=#42.5 to discriminate between the nuclear and galaxy flux. Using the ROSAT HRI data we calculated the radial wobble-corrected profiles of the sources which were compared to a new HRI point spread function (PSF) template derived from 21 X-ray bright stars. The majority of the low-luminosiy AGN shows evidence for a significant fraction of extended X-ray emission. (orig.)Proceedings of the symposium 'highlights in X-ray Astronomy', 16 refs.Available from TIB Hannover: RR 7310(98-28) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

The soft X-ray eclipses of HU Aqr

SIGLEAvailable from TIB Hannover: RR 7310(2001-24) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman