Spin period evolution of GX 1+ 4

Abstract:

Aims. We aim both to complement the existing data on the spin history of the peculiar accreting X-ray pulsar GX 1+ 4 with more past and current data from BeppoSAX, INTEGRAL, and Fermi and to interpret the evolution in the framework of accretion theory. Methods. We used source light curves obtained from BeppoSAX/WFC and INTEGRAL/ISGRI to derive pulse periods using an epoch-folding analysis. Fermi/GBM data were analysed by fitting a constant plus a Fourier expansion to background-subtracted rates, and maximizing the Y 2 statistic. We completed the sample with hard X-ray light curves from Swift/BAT. The data were checked for correlations between flux and changes of the pulsar spin on different timescales. Results. The spin-down of the pulsar continues with a constant change in frequency, ie, an apparently accelerating change in the period. Over the past three decades, the pulse period has …

Año de publicación:

2012

Keywords:

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