Two tracks in Three Dimensions: Correlations between optical, soft X-ray and hard X-ray brightness variations of the Neutron Star X-ray Binary Aquila X-1
Abstract
We present long-term multi-wavelength correlation among the fluxes in optical, soft x-ray, and hard x-ray wavelengths in the neutron star x-ray binary system Aquila X-1. We present over fourteen years of optical data obtained with the SMARTS 1.3m telescope, paired with quasi-simultaneous observations in the 2-10 keV soft X-ray range (from RXTE/ASM and MAXI), and in the 15-50 keV hard X-ray range (from Swift/BAT). We find no single correlation between the long-term optical, soft X-ray and hard X-ray fluxes, extending similar findings by Maitra & Bailyn (2008) using only the optical and soft X-ray data till 2007. In this work we show that there are in fact two distinct correlations among these 3 wavelength bands, viz., when quasi-simultaneous optical, soft X-ray, and hard X-ray fluxes are shown on a 3D plot they fall in two distinct branches. This is strongly indicative of two distinct physical mechanisms that may be operating during outbursts of Aql X-1. We speculate on plausible scenarios such as recently discovered transitions between radio-pulsar phase and an X-ray bright phase for some neutron star binaries.
- Publication:
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American Astronomical Society Meeting Abstracts #225
- Pub Date:
- January 2015
- Bibcode:
- 2015AAS...22534529S