Open AccessXMM–Newton observations of the eclipsing polar EP Dra
Author(s) -
Ramsay Gavin,
Bridge C. M.,
Cropper Mark,
Mason K. O.,
Córdova F. A.,
Priedhorsky W.
Publication year - 2004
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.08239.x
Subject(s) - physics , astrophysics , polar , accretion (finance) , intermediate polar , absorption (acoustics) , eclipse , astronomy , ultraviolet , spectral line , stars , white dwarf , optics
ABSTRACT We present XMM–Newton observations of the eclipsing polar EP Dra that cover nearly three binary orbital cycles. The X‐ray and ultraviolet data show evidence for a prominent dip before the eclipse, which is due to the accretion stream obscuring the accretion region. The dip ingress is rapid in hard X‐rays, suggesting that there is a highly collimated core of absorption. We find that a different level of absorption column density is required to match the observed count rates in different energy bands. We propose that this is due to the fact that different absorption components should be used to model the reprocessed X‐rays, the shocked X‐ray component and the ultraviolet emission, and we explore the effect that this has on the resulting fits to the spectrum. Further, there is evidence that absorption starts to obscure the softer X‐rays shortly after the onset of the bright phase. This suggests that material is threaded by an unusually wide range of magnetic field lines, consistent with the recent suggestion of Bridge et al. We find that the period is slightly greater than that determined some years ago by Schwope & Mengel.