A1 Refereed original research article in a scientific journal

Studying temporal variability of GRS 1739-278 during the 2014 outburst




AuthorsIlya A. Mereminskiy, Andrey N. Semena, Sergey D. Bykov, Ekaterina V. Filippova, Alexander A. Lutovinov, Juri Poutanen

PublisherOXFORD UNIV PRESS

Publication year2019

JournalMonthly Notices of the Royal Astronomical Society

Journal name in sourceMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Journal acronymMON NOT R ASTRON SOC

Volume482

Issue1

First page 1392

Last page1405

Number of pages14

ISSN0035-8711

eISSN1365-2966

DOIhttps://doi.org/10.1093/mnras/sty2752

Self-archived copy’s web addresshttps://research.utu.fi/converis/portal/detail/Publication/39604573


Abstract
We report a discovery of low-frequency quasi-periodic oscillation at 0.3-0.7 Hz in the power spectra of the accreting black hole GRS 1739-278 in the hard-intermediate state during its 2014 outburst based on the NuSTAR and Swift/XRT data. The QPO frequency strongly evolved with the source flux during the NuSTAR observation. The source spectrum became softer with rising QPO frequency and simultaneous increasing of the power-law index and decreasing of the cut-off energy. In the power spectrum, a prominent harmonic is clearly seen together with the main QPO peak. The fluxes in the soft and the hard X-ray bands are coherent, however, the coherence drops for the energy bands separated by larger gaps. The phase lags are generally positive (hard) in the 0.1-3 Hz frequency range, and negative below 0.1 Hz. The accretion disc inner radius estimated with the relativistic reflection spectral model appears to be R-in < 7.3R(g). In the framework of the relativistic precession model, in order to satisfy the constraints from the observed QPO frequency and the accretion disc truncation radius, a massive black hole with M-BH a parts per thousand 100 M-aS (TM) is required.

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