Variations in the dip properties of the low-mass X-ray binary XB 1254-69 observed with XMM-Newton and INTEGRAL

Abstract

We have analysed data from five XMM-Newton observations of XB 1254-69, one of them simultaneous with INTEGRAL, to investigate the mechanism responsible for the highly variable dips durations and depths seen from this low-mass X-ray binary. Deep dips were present during two observations, shallow dips during one and no dips were detected during the remaining two observations. At high (1-4 s) time resolution ``shallow dips'' are seen to include a few, very rapid, deep dips whilst the ``deep'' dips consist of many similar very rapid, deep, fluctuations. The folded V-band Optical Monitor light curves obtained when the source was undergoing deep, shallow and no detectable dipping exhibit sinusoid-like variations with different amplitudes and phases. We fit EPIC spectra obtained from "persistent" or dip-free intervals with a model consisting of disc-blackbody and thermal comptonisation components together with Gaussian emission features at 1 and 6.6 keV modified by absorption due to cold and photo-ionised material. None of the spectral parameters appears to be strongly correlated with the dip depth except for the temperature of the disc blackbody which is coolest (kT ~ 1.8 keV) when deep dips are present and warmest (kT ~ 2.1 keV) when no dips are detectable. We propose that the changes in both disc temperature and optical modulation could be explained by the presence of a tilted accretion disc in the system. We provide a revised estimate of the orbital period of 0.16388875 +/- 0.00000017 day.

16 pages, 10 figures, 4 tables. Accepted for publication in A&A

References in corpus (7)

• The magnetic nature of disk accretion onto black holes
• Relativistic iron emission lines in neutron star low-mass X-ray binaries as probes of neutron star radii
• Evidence of a Broad Relativistic Iron Line from the Neutron Star Low-Mass X-ray Binary Serpens X-1
• The measurement errors in the Swift-UVOT and XMM-OM
• Chandra Observation of the Dipping Source XB 1254-690
• Detection of Highly Ionized Metal Absorption Lines in the Ultracompact X-ray Dipper 4U 1916-05
• Kinematical Studies of the Low Mass X-Ray Binary GR Mus (XB1254-690)

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