A1 Vertaisarvioitu alkuperäisartikkeli tieteellisessä lehdessä
Polarized X-Rays from Windy Accretion in Cygnus X-1
Tekijät: Poutanen Juri, Veledina Alexandra, Beloborodov Andrei M
Kustantaja: IOP Publishing Ltd
Julkaisuvuosi: 2023
Journal: Astrophysical Journal Letters
Tietokannassa oleva lehden nimi: ASTROPHYSICAL JOURNAL LETTERS
Lehden akronyymi: ASTROPHYS J LETT
Artikkelin numero: L10
Vuosikerta: 949
Numero: 1
Sivujen määrä: 9
ISSN: 2041-8205
DOI: https://doi.org/10.3847/2041-8213/acd33e
Verkko-osoite: https://iopscience.iop.org/article/10.3847/2041-8213/acd33e
Rinnakkaistallenteen osoite: https://research.utu.fi/converis/portal/detail/Publication/179723302
Recent X-ray polarimetric data on the prototypical black hole X-ray binary Cyg X-1 from the Imaging X-ray Polarimetry Explorer present tight constraints on accretion geometry in the hard spectral state. Contrary to general expectations of a low, less than or similar to 1% polarization degree (PD), the observed average PD was found to be a factor of 4 higher. Aligned with the jet position angle on the sky, the observed polarization favors geometry of the X-ray emission region stretched normally to the jet in the accretion disk plane. The high PD is, however, difficult to reconcile with the low orbital inclination of the binary i approximate to 30 degrees. We suggest that this puzzle can be explained if the emitting plasma is outflowing with a mildly relativistic velocity greater than or similar to 0.4 c. Our radiative transfer simulations show that Comptonization in the outflowing medium elongated in the plane of the disk and radiates X-rays with the degree and direction of polarization consistent with observations at i approximate to 30 degrees.
Ladattava julkaisu This is an electronic reprint of the original article. |  |
