A long serendipitous XMM–Newton observation of the intermediate polar XY Ari1

Abstract

XY Ari is one of the few known eclipsing intermediate polars. We present results from a detailed analysis of an unpublished archival observation using XMM-Newton EPIC pn and MOS data in a quiescent state of XY Ari. The X-ray orbital modulation and spin pulse variations were investigated for energy dependent modulations in different energy bands. The broad orbital modulation observed with various observations was confirmed with XMM-Newton at hard X-ray (>1.6 keV). The EPIC light curves folded at the spin phases show a double peak profile as expected from two pole accretion. The pulse profile is found to be energy dependent. Hardness ratio variations and energy modulation depth during spin modulation can be explained by photoelectric absorption. The simultaneously fitted EPIC spectra with CEVMKL model yield maximum plasma temperature of 28 +3.1 −2.9 keV with an iron abundance Fe/Fe = 0.37 +0.06 −0.05 . We find two intrinsic partial covering absorption columns of 6.2 +1.0 −0.9 ×10 22 and 105.3 +35.4 −30.4 ×10 22 cm −2 with covering fractions of 0.53 +0.05 −0.04 , 0.41 +0.14 −0.13 respectively. In addition, a Gaussian emission line at 6.43 +0.01 −0.02 keV with an equivalent width of 51 +12 −10 eV is required to account for fluorescent emission from neutral iron. The X-ray luminosity of the source is 4.2 × 10 32 erg s −1 in the 0.2-10.0 keV energy band.

The Fe Line Flux Ratio as a Diagnostic of the Maximum Temperature and the White Dwarf Mass of Cataclysmic Variables

“…For CVs without NuSTAR observations, their T max are measured by fitting the 3-50 keV Suzaku spectra with the same model as for the NuSTAR spectra.The I 7.0 /I 6.7 values of individual CVs are adopted fromXu et al (2016) except XY Ari. The I 7.0 /I 6.7 of XY Ari is re-measured to be 0.94 ± 0.2, which is consistent with the recent XMM-Newton observations(Zengin Camurdan et al 2018), and is higher than the value (0.62 ± 0.10) obtained byXu et al (2016).…”

Dynamical mass of the white dwarf in XY Ari: a test for intermediate polar X-ray spectral models

“…While it would be ideal to obtain the duration from a very large number of X-ray eclipse observations with higher time resolution, we consider that the eclipse length in Allan et al ( 1996 ) is accurate enough for our purposes. In fact, even if it were biased by ±50 s, which is comparable to the length of the X-ray eclipse ingress/egress (Kamata et al 1991 ;Hellier 1997 ;Zengin Ćamurdan et al 2018 ), we would obtain an inclination i = 80.2 • ± 0.5 • for a 2000 ± 28 s eclipse duration, and i = 81.6 • ± 0.5 • for 2100 ± 28 s. This change in the inclination would have a < 1 per cent effect on the dynamical masses, which illustrates the robustness of our results.…”