Detection of a type-C quasi-periodic oscillation during the soft-to-hard transition in Swift J1727.8-1613

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985815%3A_____%2F25%3A00642470" target="_blank" >RIV/67985815:_____/25:00642470 - isvavai.cz</a>

Alternative codes found

RIV/00216208:11320/25:10512566

Result on the web

<a href="https://hdl.handle.net/11104/0372435" target="_blank" >https://hdl.handle.net/11104/0372435</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1051/0004-6361/202555486" target="_blank" >10.1051/0004-6361/202555486</a>

Result language

angličtina

Original language name

Detection of a type-C quasi-periodic oscillation during the soft-to-hard transition in Swift J1727.8-1613

Original language description

Context. Timing analysis of accreting systems is key to probing the structure and dynamics around compact objects. In black-hole low-mass X-ray binaries (BH LMXBs), the compact object accretes matter from a low-mass companion star via Roche-Lobe overflow and forms an accretion disk that occasionally exhibits bright eruptions. The BH LMXB Swift J1727.8-1613 (hereafter J1727) underwent one of the brightest outbursts ever recorded in X-rays in August 2023. Aims. We study the timing properties of J1727 in the decaying phase of its outburst based on XMM-Newton data with a high-time resolution. Methods. We analyzed the power spectrum (PS) and cross spectrum (CS) of J1727, which we modeled with Lorentzians. The PS reveals the power distribution of the source across frequencies, and the real and imaginary parts of the CS compare the displacement of the light curves in different energy bands for the different observations. Finally, we simultaneously derived the phase lags and the coherence using a constant phase-lag model. Results. While the first (soft-state) observation shows no strong variability, the two harder observations exhibit quasi-periodic oscillations (QPOs). Because the QPO is more significantly detected in the imaginary part of the CS than in the PS, we refer to it as the imaginary QPO. The QPO is more prominent in the soft 0.3-2 keV band than in the hard 2-12 keV band. As the source evolves toward the hard state, the imaginary QPO shifts to lower frequencies, the broadband fractional rms amplitude in the 0.3-2 keV energy band increases, and the rms covariance of the imaginary QPO decreases. Simultaneously, the phase lags increase, and the coherence function drops at the imaginary QPO frequency. Conclusions. This analysis provides the first type-C QPO detection in a BH XB during the soft-to-hard transition using XMM-Newton data. The QPO is detected at particularly low energy (0.3-2 keV). Notably, the QPO is significantly detected in the imaginary part of the CS and the PS. Thus, we confirm the physical origin of the coherence drop and the phase-lag excess, which were only observed with NICER before.

Czech name

—

Czech description

—

Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

10308 - Astronomy (including astrophysics,space science)

Project

<a href="/en/project/GX21-06825X" target="_blank" >GX21-06825X: Accreting Black Holes in the new era of X-ray polarimetry missions</a><br>

Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2025

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Astronomy & Astrophysics

ISSN

0004-6361

e-ISSN

1432-0746

Volume of the periodical

703

Issue of the periodical within the volume

Nov.

Country of publishing house

FR - FRANCE

Number of pages

9

Pages from-to

A257

UT code for WoS article

001619462900004

EID of the result in the Scopus database

2-s2.0-105022436891