MASTER optical polarization variability detection in the Microquasar V404 Cyg/GS2023+33

TL;DR

This paper reports the first detection of variable optical linear polarization in the microquasar V404 Cyg, revealing jet-related polarization changes correlated with optical brightness variations during its active phase.

Contribution

It introduces the first observation of polarization variability in V404 Cyg, linking polarization changes to jet activity and optical flux variations.

Findings

Variable polarization of 4-6% detected over ~1 hour

Polarization variability correlates with brightness decreases

Optical polarization linked to relativistic jet activity

Abstract

On 2015 June 15 the Swift space observatory discovered that the Galactic black hole candidate V404 Cyg was undergoing another active X-ray phase, after 25 years of inactivity (Barthelmy et al. 2015). Twelve telescopes of the MASTER Global Robotic Net located at six sites across four continents were the first ground based observatories to start optical monitoring of the microquasar after its gamma-ray wakeup at 18h 34m 09s U.T. on 2015 June 15 (Lipunov et al. 2015). In this paper we report, for the first time, the discovery of variable optical linear polarization, changing by 4-6% over a timescale of approximately 1 h, on two different epochs. We can conclude that the additional variable polarization arisies from the relativistic jet generated by the black hole in V404Cyg. The polarization variability correlates with optical brightness changes, increasing when the flux decreases.