Re-awakening of GRS 1716-249 after 23 yr, observed by Swift/XRT and NuSTAR
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Date
Authors
Bharali, Priya
Chandra, Sunil
Böttcher, Markus
Chauhan, Jaiverdhan
García, Javier A.
Journal Title
Journal ISSN
Volume Title
Publisher
Oxford Univ Press
Abstract
In this work, we present a spectral and temporal analysis of Swift/XRT and NuSTAR
observations of GRS 1716–249 during its recent 2016–2017 outburst. This low-mass X-ray
binary underwent an extraordinary outburst after a long quiescence of 23 yr, since its last major
outburst in 1993. The source was observed over two different epochs during 2017 April 7 and
10. The best-fitting joint spectral fitting in the energy range 0.5–79.0 keV indicates that the
spectrum is best described by relatively cold, weak disc blackbody emission, dominant thermal
Comptonization emission, and a relativistically broadened fluorescent iron K α emission line.
We observed a clear indication of a Compton hump around 30 keV. We also detected an excess
feature of 1.3 keV. Assuming a lamp-post geometry of the corona, we constrained the inner
disc radius for both observations to 11.92+8.62 −11.92 RISCO (i.e. an upper limit) and 10.39+9.51 −3.02 RISCO
(where RISCO ≡ radius of the innermost stable circular orbit) for the first epoch (E1) and
second epoch (E2), respectively. A significant (5σ) type C quasi-periodic oscillation (QPO) at
1.20 ± 0.04 Hz is detected for the first time for GRS 1716–249, which drifts to 1.55 ± 0.04 Hz
(6σ) at the end of the second observation. The derived spectral and temporal properties show
a positive correlation between the QPO frequency and the photon index
Description
Citation
Bharali, P. et al. 2019. Re-awakening of GRS 1716-249 after 23 yr, observed by Swift/XRT and NuSTAR. Monthly notices of the Royal Astronomical Society, 487(3):3150-3161. [https://doi.org/10.1093/mnras/stz1492]