Seminars at FGG
When the funnel changes the plan. Optical Polarization Across Outburst and Quiescence in the black hole X-ray binary V4641 Sgr
Speaker: Anita Maria Vena (INAF - Osservatorio Astronomico di Brera (Italy))
Date and time: 2026-09-28 12:00
Polarimetric observations provide valuable insight into the geometry and physical mechanisms responsible for optical emission in compact binary systems. In this work, we present multiwavelength (BVRI) optical polarimetric measurements of the X-ray bi- nary V4641 Sgr obtained during both outburst and quiescent phases, as part of a broader multi-band campaign linking the optical behavior of the system to its Radio and X ray properties. We characterize the polarization properties of the source across different epochs and wavelengths, including a careful assessment of the contribution from interstel- lar polarization. The resulting intrinsic polarization estimates are compared with previous polarimetric measurements of V4641 Sgr. Although the degree of polarization is low, it exhibits notable band-dependent variations between outburst and quiescence. These re- sults allow us to explore several possible origins for the observed polarization, including contributions from the jet, the hot inner accretion flow, and the accretion disc.