التفاصيل البيبلوغرافية
| العنوان: |
Discovery of evolving low-frequency QPOs in hard X-rays (∼100 keV) observed in black hole Swift J1727.8−1613 with AstroSat. |
| المؤلفون: |
Nandi, Anuj, Das, Santabrata, Majumder, Seshadri, Katoch, Tilak, Antia, H M, Shah, Parag |
| المصدر: |
Monthly Notices of the Royal Astronomical Society; Jun2024, Vol. 531 Issue 1, p1149-1157, 9p |
| مصطلحات موضوعية: |
BLACK holes, X-ray binaries, X-ray detection |
| مستخلص: |
We report the first detection of evolving low-frequency quasi-periodic oscillation (LFQPO) frequencies in hard X-rays upto 100 keV with AstroSat/ LAXPC during 'unusual' outburst phase of Swift J1727.8−1613 in hard intermediate state (HIMS). The observed LFQPO in 20–100 keV has a centroid |$\nu _{_{\rm QPO}}=1.43$| Hz, a coherence factor Q = 7.14 and an amplitude |${\rm rms_{_{\rm QPO}}} = 10.95{{\ \rm per\ cent}}$| with significance σ = 5.46. Type-C QPOs (1.09–2.6 Hz) are found to evolve monotonically during HIMS of the outburst with clear detection in hard X-rays (80−100 keV), where |${\rm rms_{_{\rm QPO}}}$| decreases (|$\sim 12\!-\!3{{\ \rm per\ cent}}$|) with energy. Further, |$\nu _{_{\rm QPO}}$| is seen to correlate (anticorrelate) with low- (high-) energy flux in 2–20 keV (15–50 keV). Wide-band (0.7−40 keV) energy spectrum of NICER/ XTI and AstroSat/ LAXPC is satisfactorily described by the 'dominant' thermal Comptonization contribution (∼88 per cent) in presence of a 'weak' signature of disc emissions (kT in ∼ 0.36 keV) indicating the harder spectral distribution. Considering source mass |$M_{\rm BH}=10\, \mathrm{M}_\odot$| and distance 1.5 < d (kpc) < 5, the unabsorbed bolometric luminosity is estimated as |$\sim 0.03\!-\!0.92{{\ \rm per\ cent}}\, L_{\rm Edd}$|. Finally, we discuss the implications of our findings in the context of accretion dynamics around black hole X-ray binaries. [ABSTRACT FROM AUTHOR] |
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