Accretion geometry of the neutron star low mass X-ray binary Cyg X-2 from X-ray polarization measurements

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F67985815%3A_____%2F23%3A00574444" target="_blank" >RIV/67985815:_____/23:00574444 - isvavai.cz</a>

Výsledek na webu

<a href="https://hdl.handle.net/11104/0345186" target="_blank" >https://hdl.handle.net/11104/0345186</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1093/mnras/stac3726" target="_blank" >10.1093/mnras/stac3726</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Accretion geometry of the neutron star low mass X-ray binary Cyg X-2 from X-ray polarization measurements

Popis výsledku v původním jazyce

We report spectro-polarimetric results of an observational campaign of the bright neutron star low-mass X-ray binary Cyg X-2 simultaneously observed by IXPE, NICER, and INTEGRAL. Consistently with previous results, the broad-band spectrum is characterized by a lower-energy component, attributed to the accretion disc with kT(in) approximate to 1 keV, plus unsaturated Comptonization in thermal plasma with temperature kT(e) = 3 keV and optical depth tau approximate to 4, assuming a slab geometry. We measure the polarization degree in the 2-8 keV band P = 1.8 +/- 0.3 percent and polarization angle phi = 140 degrees +/- 4 degrees, consistent with the previous X-ray polarimetric measurements by OSO-8 as well as with the direction of the radio jet which was earlier observed from the source. While polarization of the disc spectral component is poorly constrained with the IXPE data, the Comptonized emission has a polarization degree P = 4.0 +/- 0.7 percent and a polarization angle aligned with the radio jet. Our results strongly favour a spreading layer at the neutron star surface as the main source of the polarization signal. However, we cannot exclude a significant contribution from reflection off the accretion disc, as indicated by the presence of the iron fluorescence line.

Název v anglickém jazyce

Accretion geometry of the neutron star low mass X-ray binary Cyg X-2 from X-ray polarization measurements

Popis výsledku anglicky

We report spectro-polarimetric results of an observational campaign of the bright neutron star low-mass X-ray binary Cyg X-2 simultaneously observed by IXPE, NICER, and INTEGRAL. Consistently with previous results, the broad-band spectrum is characterized by a lower-energy component, attributed to the accretion disc with kT(in) approximate to 1 keV, plus unsaturated Comptonization in thermal plasma with temperature kT(e) = 3 keV and optical depth tau approximate to 4, assuming a slab geometry. We measure the polarization degree in the 2-8 keV band P = 1.8 +/- 0.3 percent and polarization angle phi = 140 degrees +/- 4 degrees, consistent with the previous X-ray polarimetric measurements by OSO-8 as well as with the direction of the radio jet which was earlier observed from the source. While polarization of the disc spectral component is poorly constrained with the IXPE data, the Comptonized emission has a polarization degree P = 4.0 +/- 0.7 percent and a polarization angle aligned with the radio jet. Our results strongly favour a spreading layer at the neutron star surface as the main source of the polarization signal. However, we cannot exclude a significant contribution from reflection off the accretion disc, as indicated by the presence of the iron fluorescence line.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10308 - Astronomy (including astrophysics,space science)

Projekt

—

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2023

Kód důvěrnosti údajů

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

Název periodika

Monthly Notices of the Royal Astronomical Society

ISSN

0035-8711

e-ISSN

1365-2966

Svazek periodika

519

Číslo periodika v rámci svazku

3

Stát vydavatele periodika

US - Spojené státy americké

Počet stran výsledku

10

Strana od-do

3681-3690

Kód UT WoS článku

001035850100014

EID výsledku v databázi Scopus

2-s2.0-85148270126