2012A&A...537A..66G -
Astronomy and Astrophysics, volume 537A, 66-66 (2012/1-1)
Spin period evolution of GX 1+4.
GONZALEZ-GALAN A., KUULKERS E., KRETSCHMAR P., LARSSON S., POSTNOV K., KOCHETKOVA A. and FINGER M.H.
Abstract (from CDS):
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. 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 Y2 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. The spin-down of the pulsar continues with a constant change in frequency, i.e., an apparently accelerating change in the period. Over the past three decades, the pulse period has increased by about ∼50%. Short-term fluctuations on top of this long-term trend do show anti-correlation with the source flux. Possible explanations of the observed long-term frequency and its dependence on flux are discussed.
Abstract Copyright:
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Journal keyword(s):
accretion, accretion disks - X-rays: bursts - pulsars: individual: GX 1+4
Simbad objects:
6
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