TY - JOUR
T1 - Disc and wind in black hole X-ray binary MAXI J1820+070 observed through polarized light during its 2018 outburst
AU - Kosenkov, Ilia A.
AU - Veledina, Alexandra
AU - Berdyugin, Andrei V.
AU - Kravtsov, Vadim
AU - Piirola, Vilppu
AU - Berdyugina, Svetlana V.
AU - Sakanoi, Takeshi
AU - Kagitani, Masato
AU - Poutanen, Juri
N1 - Funding Information:
We acknowledge support from the Magnus Ehrnrooth Foundation, the Academy of Finland grants 309308 and 321722 (AV), the Russian Science Foundation grant 20-12-00364 (AV, VK, and JP), the Finnish National Agency for Education (EDUFI) Fellowship (VK), and ERC Advanced Grant HotMol ERC-2011-AdG-291659 (SVB and AVB). The Dipol-2 polarimeter was built in cooperation by the University of Turku, Finland, and the Leibniz Institut für Sonnenphysik, Germany, with support from the Leibniz Association grant SAW-2011-KIS-7. We are grateful to the Institute for Astronomy, University of Hawaii, for the allocated observing time. We acknowledge with thanks the variable star observations from the AAVSO International Database contributed by observers worldwide and used in this research.
Publisher Copyright:
© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.
PY - 2020/5/22
Y1 - 2020/5/22
N2 - We describe the first complete polarimetric data set of the entire outburst of a low-mass black hole X-ray binary system and discuss the constraints for geometry and radiative mechanisms it imposes. During the decaying hard state, when the optical flux is dominated by the non-thermal component, the observed polarization is consistent with the interstellar values in all filters. During the soft state, the intrinsic polarization of the source is small, ∼0.15 per cent in B and V filters, and is likely produced in the irradiated disc. A much higher polarization, reaching ∼0.5 per cent in V and R filters, at a position angle of ∼25a observed in the rising hard state coincides in time with the detection of winds in the system. This angle coincides with the position angle of the jet. The detected optical polarization is best explained by scattering of the non-thermal (hot flow or jet base) radiation in an equatorial wind.
AB - We describe the first complete polarimetric data set of the entire outburst of a low-mass black hole X-ray binary system and discuss the constraints for geometry and radiative mechanisms it imposes. During the decaying hard state, when the optical flux is dominated by the non-thermal component, the observed polarization is consistent with the interstellar values in all filters. During the soft state, the intrinsic polarization of the source is small, ∼0.15 per cent in B and V filters, and is likely produced in the irradiated disc. A much higher polarization, reaching ∼0.5 per cent in V and R filters, at a position angle of ∼25a observed in the rising hard state coincides in time with the detection of winds in the system. This angle coincides with the position angle of the jet. The detected optical polarization is best explained by scattering of the non-thermal (hot flow or jet base) radiation in an equatorial wind.
KW - X-rays: binaries
KW - polarization
KW - stars: black holes
KW - stars: individual: MAXI J1820+070
UR - http://www.scopus.com/inward/record.url?scp=85087024350&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85087024350&partnerID=8YFLogxK
U2 - 10.1093/mnrasl/slaa096
DO - 10.1093/mnrasl/slaa096
M3 - Article
AN - SCOPUS:85087024350
SN - 1745-3925
VL - 496
SP - L96-L100
JO - Monthly Notices of the Royal Astronomical Society: Letters
JF - Monthly Notices of the Royal Astronomical Society: Letters
IS - 1
ER -