A precessing accretion disc in the intermediate polar XY Ari?

Abstract

XY Ari is the only intermediate polar to show deep X-ray eclipses of its white dwarf. Previously published observations with Ginga and Chandra have also revealed a broad X-ray orbital modulation, roughly antiphased with the eclipse, and presumed to be due to absorption in an extended structure near the edge of an accretion disc. The X-ray pulse profile is generally seen to be double-peaked, although a single-peaked pulse was seen by RXTE during an outburst in 1996.We intended to investigate the cause of the broad orbital modulation in XY Ari to better understand the accretion flow in this system and other intermediate polars. We observed XY Ari with RXTE and analysed previously unpublished archival observations of the system made with ASCA and XMM-Newton. These observations comprise six separate visits and span about ten years. The various X-ray observations show that the broad orbital modulation varies in phase and significance, then ultimately disappears entirely in the last few years. In addition, the X-ray pulse profile shows variations in depth and shape, and in the recent RXTE observations displays no evidence for changes in hardness ratio. The observed changes indicates that both the pulse profile and the orbital modulation are solely due to geometrical effects at the time of the RXTE observations, rather than phase-dependent variations in photoelectric absorption as seen previously. We suggest that this is evidence for a precessing, tilted accretion disc in this system. The precession of the disc moves structures out of our line of sight both at its outer edge (changing the orbital modulation) and at its inner edge where the accretion curtains are anchored (changing the pulse profile).

Accepted for publication in Astronomy & Astrophysics

References in corpus (15)

• The spin periods and magnetic moments of white dwarfs in magnetic cataclysmic variables
• Long-term Properties of Accretion Disks in X-ray Binaries: II. Stability of Radiation-Driven Warping
• The size of the accretion region in intermediate polars: eclipses of XY Arietis observed with RXTE
• An outburst of the magnetic cataclysmic variable XY Arietis observed with RXTE
• Chandra Observations of MBM12 and Models of the Local Bubble
• Outbursts of EX Hydrae: mass-transfer events or disc instabilities?
• X-ray Orbital Modulations in Intermediate Polars
• Evidence of Precession of the White Dwarf in Cataclysmic Variables
• Three dimensional SPH simulations of radiation-driven warped accretion discs
• On the multi-periodicities in the X-ray dipper XB 1916-053
• On the magnetic accretor GK Persei in outburst
• Magnetically moderated outbursts of WZ Sagittae
• K-band spectroscopy of the intermediate polar XY Ari
• The Anisotropic Transfer of Resonance Photons in Hot Plasmas on Magnetized White Dwarfs
• An Observation of the Intermediate Polar XY Arietis with Chandra

Cited by in corpus (10)

• Hard X-ray properties of magnetic cataclysmic variables
• The defining characteristics of Intermediate Polars - the case of three candidate systems
• The Emergence of Negative Superhumps in Cataclysmic Variables: Smoothed Particle Hydrodynamics Simulations
• Exploring X-ray variability with unsupervised machine learning I. Self-organizing maps applied to XMM-Newton data
• X-ray Study of Rekindled Accretion in the Classical Nova V2491 Cygni
• IGR J14257-6117, a magnetic accreting white dwarf with a very strong X-ray orbital modulation
• Very fast photometric and X-ray observations of the intermediate polar V2069 Cygni (RX J2123.7+4217)
• An X-ray study for white dwarf binary AR Scorpii
• XMM-Newton confirmation of a new intermediate polar: XMMU J185330.7-012815
• Broad Observational Perspectives Achieved by the Accreting White Dwarf Sciences in the XMM-Newton and Chandra Eras