Why do some intermediate polars show soft X-ray emission? A survey of XMM-Newton spectra

Abstract

We make a systematic analysis of the XMM-Newton X-ray spectra of intermediate polars (IPs) and find that, contrary to the traditional picture, most show a soft blackbody component. We compare the results with those from AM Her stars and deduce that the blackbody emission arises from reprocessing of hard X-rays, rather than from the blobby accretion sometimes seen in AM Hers. Whether an IP shows a blackbody component appears to depend primarily on geometric factors: a blackbody is not seen in those that have accretion footprints that are always obscured by accretion curtains or are only visible when foreshortened on the white-dwarf limb. Thus we argue against previous suggestions that the blackbody emission characterises a separate sub-group of IPs which are more akin to AM Hers, and develop a unified picture of the blackbody emission in these stars.

9 pages, 6 figures. Accepted for publication in ApJ

References in corpus (2)

• The X-ray properties of the magnetic Cataclysmic Variable UU Col
• XMM-Newton observations of the complex spin pulse of the intermediate polar PQ~Geminorum

Cited by in corpus (25)

• INTEGRAL/IBIS and Swift/XRT observations of hard cataclysmic variables
• Two new Intermediate Polars with a soft X-ray component
• Broad-band characteristics of seven new hard X-ray selected cataclysmic variables
• 1RXSJ173021.5-055933: a cataclysmic variable with a fast-spinning magnetic white dwarf
• Circular polarization survey of intermediate polars I. Northern targets in the range 17h<R.A.<23h
• XMM-Newton observations of the Galactic globular clusters NGC 2808 and NGC 4372
• PALOMA: A Magnetic CV between Polars and Intermediate Polars
• EXTraS discovery of two pulsators in the direction of the LMC: a Be/X-ray binary pulsar in the LMC and a candidate double-degenerate polar in the foreground
• Multi-mission observations of the old nova GK Per during the 2015 outburst
• The intermediate polar cataclysmic variable GK Persei 120 years after the nova explosion: a first dynamical mass study
• On the area of accretion curtains from fast aperiodic time variability of the intermediate polar EX Hya
• The role of complex ionized absorber in the soft X-ray spectra of Intermediate Polars
• DW Cancri in x-rays
• Discovery of spin modulated circular polarization from IGR J17014-4306, the remnant of Nova Scorpii 1437 A.D
• Discovery of four super-soft X-ray sources in XMM-Newton observations of the Large Magellanic Cloud
• Chandra, NuSTAR, and Optical Observations of the Cataclysmic Variables IGR J17528-2022 and IGR J20063+3641
• Features of the Accretion in the EX Hydrae System: Results of Numerical Simulation
• Comptonization as an origin of the continuum in Intermediate Polars
• X-ray confirmation of the intermediate polar IGR J16547-1916
• Timing analysis of a sample of five cataclysmic variable candidates observed by the XMM-Newton satellite
• Broad Observational Perspectives Achieved by the Accreting White Dwarf Sciences in the XMM-Newton and Chandra Eras
• Unravelling optical and X-ray properties of the disc-dominated intermediate polar IGR J15094-6649
• Disc-Magnetosphere interactions in Cataclysmic Variable Stars
• X-ray emission mechanisms in accreting white dwarfs
• Multiwavelength Characterization of a New Magnetic Cataclysmic Variable 2CXO J050740.7-091337