Disentangling the stellar atmosphere and the focused wind in different accretion states of Cygnus X-1

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985815%3A_____%2F25%3A00618572" target="_blank" >RIV/67985815:_____/25:00618572 - isvavai.cz</a>

Alternative codes found

RIV/00216208:11320/25:10512582

Result on the web

<a href="https://hdl.handle.net/11104/0365970" target="_blank" >https://hdl.handle.net/11104/0365970</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1051/0004-6361/202450910" target="_blank" >10.1051/0004-6361/202450910</a>

Result language

angličtina

Original language name

Disentangling the stellar atmosphere and the focused wind in different accretion states of Cygnus X-1

Original language description

In high-mass X-ray binaries (HMXBs), the compact object accretes the strong stellar wind of an O-B supergiant companion star. X-ray flux variations alter the stellar wind's ionization state and optical line profiles, which are important in the determination of the orbital parameters of the system. Aims. We analyzed the state-dependent variability of the line profiles by separating the components coming from the star's atmosphere and the accreted stream of matter located between the star and the accretion disk (i.e. the focused wind). We then determined the radial velocities and the intensities of the absorption and emission lines with respect to the continuum. Methods. We performed optical high-resolution spectroscopy of the HMXB Cyg X-1 in the hard and soft-intermediate X-ray spectral states, respectively from 2022 and 2023, over multiple orbital phases. We then applied the method of Fourier disentangling to combine the spectra and isolate the stellar atmosphere and focused wind components. Results. We observe P-Cygni profiles of the H alpha line in the stellar atmosphere and a wide emission from the focused wind, indicating an outflowing material. While He I lambda 6678 is in absorption in the stellar atmosphere and not detected in the focused wind, we see a broad emission feature of He II lambda 4686 in the focused wind. Moreover, we identify an X-ray/optical anticorrelation traced by the strength of the line intensity. The intensity of the lines drops in the soft-intermediate spectral state and the lines are more absorbed at the inferior conjunction of the star. Conclusions. Our results confirm that the He II emission comes from the focused wind rather than the stellar atmosphere and is produced from the re-scattering of the resonance line due to high-density clumps in the focused wind. The X-ray/optical anticorrelation shows a stronger wind in the low-hard state and the lines are stronger at the inferior conjunction of the star.

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

Result was created during the realization of more than one project. More information in the Projects tab.

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

695

Issue of the periodical within the volume

March

Country of publishing house

FR - FRANCE

Number of pages

15

Pages from-to

A115

UT code for WoS article

001442985200012

EID of the result in the Scopus database

2-s2.0-86000780355