Variability of X-ray polarization of Cyg X-1

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985815%3A_____%2F25%3A00639182" target="_blank" >RIV/67985815:_____/25:00639182 - isvavai.cz</a>

Alternative codes found

RIV/00216208:11320/25:10512579

Result on the web

<a href="https://hdl.handle.net/11104/0369962" target="_blank" >https://hdl.handle.net/11104/0369962</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1051/0004-6361/202555411" target="_blank" >10.1051/0004-6361/202555411</a>

Result language

angličtina

Original language name

Variability of X-ray polarization of Cyg X-1

Original language description

We present the results of a three-year X-ray, optical, and radio polarimetric monitoring campaign of the prototypical black hole X-ray binary Cyg X-1, conducted from 2022 to 2024. The X-ray polarization of Cyg X-1 was measured 13 times with the Imaging X-ray Polarimetry Explorer (IXPE), covering both hard and soft spectral states. The X-ray polarization degree (PD) in the hard state was found to be approximate to 4.0%, roughly twice as high as in the soft state, where it was around 2.2%. In both states, a statistically significant increase in PD with the energy was found. Moreover, a linear relation between PD and spectral hardness suggests a gradual and continuous evolution of the polarization properties, rather than an abrupt change of polarization production mechanism between states. The polarization angle (PA) was independent of the spectral state and showed no trend with the photon energy. The X-ray PA is well aligned with the orientation of the radio jet, as well as the optical and radio PAs. We find significant orbital changes of PA in the hard state, which we attribute to scattering of X-ray emission at the intrabinary structure. No significant superorbital variability in PD or PA was found at the period P-so = 294 d. We detect, for the first time in this source, polarization of the radio emission, with the PA aligned with the jet, and a strong increase of the PD at a transition to the soft state. We also find no correlation between the X-ray and optical polarization, if any, there is a long-term anti-correlation between the X-ray PD and the radio PD.

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

701

Issue of the periodical within the volume

Sept.

Country of publishing house

FR - FRANCE

Number of pages

12

Pages from-to

A115

UT code for WoS article

001567142600008

EID of the result in the Scopus database

2-s2.0-105015569667