English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Our simultaneous three-colour ($BVR$) polarimetric observations of thelow-mass black hole X-ray binary V404 Cyg show a small but statisticallysignificant change of polarization degree ($\Delta p \sim 1$ per cent) betweenthe outburst in June 2015 and the quiescence. The polarization of V404 Cyg inthe quiescent state agrees within the errors with that of the visually close(1\farcs4) companion ($p_{R} = 7.3\pm 0.1$ per cent), indicating that it ispredominantly of interstellar origin. The polarization pattern of thesurrounding field stars supports this conclusion. From the observed variablepolarization during the outburst we show that polarization degree of theintrinsic component peaks in the $V$-band, $p_{V} = 1.1\pm 0.1$ per cent, atthe polarization position angle of $\theta_{V}= -7\deg\pm 2\deg$, which isconsistent in all three passbands. We detect significant variations in theposition angle of the intrinsic polarization in $R$ band from $-30\deg$ to$\sim 0\deg$ during the outburst peak. The observed wavelength dependence ofthe intrinsic polarization does not support non-thermal synchrotron emissionfrom a jet as a plausible mechanism, but is in better agreement with thecombined effect of electron (Thomson) scattering and absorption in a flattenedplasma envelope or outflow surrounding the illuminating source. Alternatively,the polarization signal can be produced by scattering of the disc radiation ina mildly relativistic polar outflow. The position angle of the intrinsicpolarization, nearly parallel to the jet direction (i.e. perpendicular to theaccretion disc plane), is in agreement with these interpretations.

High-precision optical polarimetry of the accreting black hole V404 Cyg during the June 2015 outburst