Probing the accretion processes in soft X-ray selected polars

High-energy data of accreting white dwarfs give access to the regime of the primary accretion-induced energy release and the different proposed accretion scenarios. We perform XMM-Newton observations of polars selected due to their ROSAT hardness ratios close to -1.0 and model the emission processes in accretion column and accretion region. Our models consider the multi-temperature structure of the emission regions and are mainly determined by mass-flow density, magnetic field strength, and white-dwarf mass. To describe the full spectral energy distribution from infrared to X-rays in a physically consistent way, we include the stellar contributions and establish composite models, which will also be of relevance for future X-ray missions. We confirm the X-ray soft nature of three polars.Comment: Accepted for publication in Acta Polytechnica, Proceedings of "The Golden Age of Cataclysmic Variables and Related Objects II

Probing the Accretion Processes in Soft X-Ray Selected Polars

High-energy data of accreting white dwarfs give access to the regime of the primary accretion-induced energy release and the different proposed accretion scenarios. We perform XMM-Newton observations of polars selected due to their ROSAT hardness ratios close to -1.0 and model the emission processes in accretion column and accretion region. Our models consider the multi-temperature structure of the emission regions and are mainly determined by mass-flow density, magnetic field strength, and white-dwarf mass. To describe the full spectral energy distribution from infrared to X-rays in a physically consistent way, we include the stellar contributions and establish composite models, which will also be of relevance for future X-ray missions. We confirm the X-ray soft nature of three polars

Verhalten und Wachstum von Ferkeln nach der Kastration unter Injektions- oder Inhalationsnarkose

In German organic agriculture, general anaesthesia of male piglets before castration is commonly performed by injection of ketamine and azaperone, plus application of the analgesic meloxicam. Inhalation anaesthesia with isoflurane (plus meloxicam) is an alternative with a shorter recovery phase and widely used in Switzerland, but requires reclassification for pigs on a case to case basis in Germany. In order to provide data on piglets´ behavior after castration and potential long-term effects on growth until weaning, a trial under practical conditions on an experimental farm was conducted. Body weight development until weaning was not affected by the method of anaesthesia. However, piglets anaesthetised with injection showed significantly more motoric anomalies and were in danger of being crushed more frequently during the first eight hours after castration. We conclude that piglets recover faster after inhalation anaesthesia, therefore the approval and use of isoflurane can be recommended

XMM-Newton observations of the low-luminosity cataclysmic variable V405 Pegasi

V405 Peg is a low-luminosity cataclysmic variable (CV) that was identified as the optical counterpart of the bright, high-latitude ROSAT all-sky survey source RBS1955. The system was suspected to belong to a largely undiscovered population of hibernating CVs. Despite intensive optical follow-up its subclass however remained undetermined. We want to further classify V405 Peg and understand its role in the CV zoo via its long-term behaviour, spectral properties, energy distribution and accretion luminosity. We perform a spectral and timing analysis of \textit{XMM-Newton} X-ray and ultra-violet data. Archival WISE, HST, and Swift observations are used to determine the spectral energy distribution and characterize the long-term variability. The X-ray spectrum is characterized by emission from a multi-temperature plasma. No evidence for a luminous soft X-ray component was found. Orbital phase-dependent X-ray photometric variability by $\sim50\%$ occurred without significant spectral changes. No further periodicity was significant in our X-ray data. The average X-ray luminosity during the XMM-Newton observations was L_X, bol simeq 5e30 erg/s but, based on the Swift observations, the corresponding luminosity varied between 5e29 erg/s and 2e31 erg/son timescales of years. The CV subclass of this object remains elusive. The spectral and timing properties show commonalities with both classes of magnetic and non-magnetic CVs. The accretion luminosity is far below than that expected for a standard accreting CV at the given orbital period. Objects like V405 Peg might represent the tip of an iceberg and thus may be important contributors to the Galactic Ridge X-ray Emission. If so they will be uncovered by future X-ray surveys, e.g. with eROSITA.Comment: A&A, in pres

V902 Monocerotis: a likely disc-accreting intermediate polar

Aims: We aim to confirm whether the eclipsing cataclysmic variable V902 Mon is an Intermediate Polar, to characterise its X-ray spectrum and flux, and to refine its orbital ephemeris and spin period. Methods: We performed spectrographic observations of V902 Mon in 2016 with the 2.2m Calar Alto telescope, and X-ray photometry and spectroscopy with XMM-Newton in October 2017. This data was supplemented by several years of AAVSO visual photometry. Results: We have confirmed V902 Mon as an IP based on detecting the spin period, with a value of 2,208s, at multiple epochs. Spectroscopy of the donor star and Gaia parallax yield a distance of 3.5+1.3-0.9, kpc, suggesting an X-ray luminosity one or two orders of magnitude lower than the 10^33 erg/s typical of previously known IPs. The X-ray to optical flux ratio is also very low. The inclination of the system is more than 79deg, with a most likely value of around 82deg. We have refined the eclipse ephemeris, stable over 14,000 cycles. The Halpha line is present throughout the orbital cycle and is clearly present during eclipse, suggesting an origin distant from the white dwarf, and shows radial velocity variations at the orbital period. The amplitude and overall recessional velocity seem inconsistent with an origin in the disc. The \emph{XMM-Newton} observation reveals a partially absorbed plasma model typical of magnetic CVs, with a fluorescent iron line at 6.4keV showing a large equivalent width of 1.4keV. Conclusions: V902 Mon is an IP, and probably a member of the hypothesized X-ray underluminous class of IPs. It is likely to be a disc accretor, though the radial velocity behaviour of the Halpha line remains puzzling. The large equivalent width of the fluorescent iron line, the small FX/Fopt ratio, and the only marginal detection of X-ray eclipses suggests that the X-ray emission arises from scattering.Comment: 10 pages, 12 figure

XMM-Newton observations of the X-ray soft polar QS Telescopii

Context. On the basis of XMM-Newton observations, we investigate the energy balance of selected magnetic cataclysmic variables, which have shown an extreme soft-to-hard X-ray flux ratio in the ROSAT All-Sky Survey. Aims. We intend to establish the X-ray properties of the system components, their flux contributions, and the accretion geometry of the X-ray soft polar QS Tel. In the context of high-resolution X-ray analyses of magnetic cataclysmic variables, this study will contribute to better understanding the accretion processes on magnetic white dwarfs. Methods. During an intermediate high state of accretion of QS Tel, we have obtained 20 ks of XMM-Newton data, corresponding to more than two orbital periods, accompanied by simultaneous optical photometry and phase-resolved spectroscopy. We analyze the multi-wavelength spectra and light curves and compare them to former high- and low-state observations. Results. Soft emission at energies below 2 keV dominates the X-ray light curves. The complex double-peaked maxima are disrupted by a sharp dip in the very soft energy range (0.1-0.5 keV), where the count rate abruptly drops to zero. The EPIC spectra are described by a minimally absorbed black body at 20 eV and two partially absorbed MEKAL plasma models with temperatures around 0.2 and 3 keV. The black-body-like component arises from one mainly active, soft X-ray bright accretion region nearly facing the mass donor. Parts of the plasma emission might be attributed to the second, virtually inactive pole. High soft-to-hard X-ray flux ratios and hardness ratios demonstrate that the high-energy emission of QS Tel is substantially dominated by its X-ray soft component.Comment: Accepted for publication in Astronomy and Astrophysics. 7 pages, 4 figures, 2 table