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arXiv · 1312.2379

A year in the life of the low-mass X-ray transient Aql X-1

F. Coti Zelati·S. Campana·P. D'Avanzo·A. Melandri
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Abstract

The Swift satellite monitored the quiescence of the low-mass X-ray binary transient Aql X-1 on a weekly basis during the March-November 2012 interval. A total of 42 observations were carried out in the soft X-ray (0.3-10 keV) band with the X-ray Telescope on board Swift. We investigated the X-ray variability properties of Aql X-1 during quiescence by tracking luminosity variations and characterising them with a detailed spectral analysis. The source is highly variable in this phase and two bright flares were detected, with peak luminosities of ~4x10^{34} erg s^{-1} (0.3-10 keV). Quiescent X-ray spectra require both a soft thermal component below ~2 keV and a hard component (a power law tail) above ~2 keV. Changes in the power law normalisation alone can account for the overall observed variability. Therefore, based on our data set, the quiescent X-ray emission of Aql X-1 is consistent with the cooling of the neutron star core and with mechanisms involving the accretion of matter onto the neutron star surface or magnetosphere.

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F. Coti Zelati, S. Campana, P. D'Avanzo, A. Melandri. 2013-12-09. A year in the life of the low-mass X-ray transient Aql X-1. https://doi.org/10.1093/mnras%2Fstt2384

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