Investigation of the Outburst Activity of the Black Hole Candidate GRS 1739-278

Bykov, S. D.; Filippova, E.V.; Mereminskiy, I. A.; Семена, А. Н.; Lutovinov, A.

doi:10.1134/s1063773719030022

Cited by 1 publication

(1 citation statement)

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“…Yan & Yu (2017) studied the X-ray spectra of the black hole candidate GRS 1739-278 during the 2 reflares observed after its 2014 outburst. These reflares underwent spectral state transitions and showed hysteresis loops in the HID (see also Bykov et al 2019). Yan & Yu defined the hard state as the period when a simple power law (with Γ < 2.1) fitted the spectra, the soft state when the disc component was > 80 per cent of the total flux (0.5−10 keV), and the intermediate state between those two.…”

Section: Spectral and Timing Analysis Of Reflares In Other Lmxbsmentioning

confidence: 99%

A NICER look at the state transitions of the black hole candidate MAXI J1535−571 during its reflares

Cúneo

Alabarta

Zhang

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The black hole candidate and X-ray binary MAXI J1535−571 was discovered in 2017 September. During the decay of its discovery outburst, and before returning to quiescence, the source underwent at least four reflaring events, with peak luminosities of ∼1035–36 erg s−1 (d/4.1 kpc)2. To investigate the nature of these flares, we analysed a sample of NICER (Neutron star Interior Composition Explorer) observations taken with almost daily cadence. In this work, we present the detailed spectral and timing analysis of the evolution of the four reflares. The higher sensitivity of NICER at lower energies, in comparison with other X-ray detectors, allowed us to constrain the disc component of the spectrum at ∼0.5 keV. We found that during each reflare the source appears to trace out a q-shaped track in the hardness–intensity diagram similar to those observed in black hole binaries during full outbursts. MAXI J1535−571 transits between the hard state (valleys) and softer states (peaks) during these flares. Moreover, the Comptonized component is undetected at the peak of the first reflare, while the disc component is undetected during the valleys. Assuming the most likely distance of 4.1 kpc, we find that the hard-to-soft transitions take place at the lowest luminosities ever observed in a black hole transient, while the soft-to-hard transitions occur at some of the lowest luminosities ever reported for such systems.

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Section: Spectral and Timing Analysis Of Reflares In Other Lmxbsmentioning

confidence: 99%