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arXiv · 2212.05243

Revealing the spectral state transition of the Clocked Burster, GS 1826-238 with NuSTAR StrayCats

S. B. Yun·B. W. Grefenstette·R. M. Ludlam·M. C. Brumback·D. J. K. Buisson·G. Mastroserio·S. N. Pike
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Abstract

We present the long term analysis of GS 1826-238, a neutron star X-ray binary known as the "Clocked Burster", using data from NuSTAR StrayCats. StrayCats, a catalogue of NuSTAR stray light data, contains data from bright, off-axis X-ray sources that have not been focused by the NuSTAR optics. We obtained stray light observations of the source from 2014-2021, reduced and analyzed the data using nustar-gen-utils Python tools, demonstrating the transition of source from the "island" atoll state to a "banana" branch. We also present the lightcurve analysis of Type I X-Ray bursts from the Clocked Burster and show that the bursts from the banana/soft state are systematically shorter in durations than those from the island/hard state and have a higher burst fluence. From our analysis, we note an increase in mass accretion rate of the source, and a decrease in burst frequency with the transition.

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S. B. Yun, B. W. Grefenstette, R. M. Ludlam, M. C. Brumback, D. J. K. Buisson, G. Mastroserio, S. N. Pike. 2022-12-10. Revealing the spectral state transition of the Clocked Burster, GS 1826-238 with NuSTAR StrayCats. https://doi.org/10.3847/1538-4357%2Facb689

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