Multi-colour optical photometry of V404 Cygni in outburst

Abstract

Context. This observational paper has been prepared in the context of the large multi-wavelength effort by many observers with the aim of following up the transient flaring event of V404 Cygni that took place for several weeks in 2015 June. Aims. Our main original aim was to contribute to the study of this transient source by acquiring broad-band photometric observations during its most active flaring phases. Nevertheless, after a detailed analysis of the data, several interesting results were obtained that encouraged a dedicated publication. Methods. The methodology used was based on broad-band differential CCD photometry. This outburst of V404 Cygni rendered the source a very bright target easily within reach of small educational telescopes. Therefore, the 41 cm telescope available at the Astronomical Observatory of the University of Jaén was used in this work. Results. We detected variability at different time scales, both in amplitude and colour. Individual optical flares appear every half hour on average during our 3 h long observation, although large-amplitude (∼1 mag) variations are also observed to occur on intervals as short as 10 min. Also, colour variations appear to be highly correlated in a colour-colour diagram. Another remarkable finding is the detection of time lag, from about one to a fraction of a minute between light curves in different filters (VR c I c ).Conclusions. The observed behaviour is tentatively interpreted in an scenario based on the ejection of non-thermal emitting, relativistic plasmons, with their synchrotron spectra extending up to optical wavelengths. This would render some of the V404 Cygni flares very similar to those of the well-know microquasar GRS 1915+105

Accretion and outflow in V404 Cyg

“…Many papers have dealt with the timing and spectral properties of the exceptional flares in different energy bands (e.g. Rodriguez et al 2015;Natalucci et al 2015;Roques et al 2015;Kimura et al 2015;Jenke et al 2016;Martí et al 2016;Gandhi et al 2016;Loh et al 2016;Jourdain et al 2017;Rodi et al 2017;Walton et al 2017;Motta et al 2017a;Sánchez-Fernández et al 2017;Maitra et al 2017;Tachibana et al 2017;Tetarenko et al 2017Tetarenko et al , 2019. Here in this paper we have focused instead on the optical study of the nebular phase and subsequent decay, with the aim of constraining the physics of the outflow.…”

Discovery of optical flickering from the symbiotic star EF Aquilae

“…During the period August–November 2016, we secured CCD photometric monitoring with five telescopes equipped with CCD cameras: the 2.0‐m RCC telescope of the National Astronomical Observatory Rozhen, Bulgaria (CCD VersArray 1300 B, 1,340×1,300 px); the 50/70‐cm Schmidt telescope of NAO Rozhen (SBIG STL11000M CCD, 4,008×2,672 px); the 60‐cm telescope of the Belogradchick Astronomical Observatory (SBIG ST8 CCD, 1,530×1,020 px); the 30‐cm astrograph of IRIDA Observatory (CCD camera ATIK 4000M, 2,048×2,048 px); the automated 41‐cm telescope of the University of Jaén, Spain—ST10‐XME CCD camera with 2,184×1,472 px (Martí et al ). …”

The 2015 Decay of the Black Hole X-Ray Binary V404 Cygni: Robust Disk-Jet Coupling and a Sharp Transition Into Quiescence

“…For about two weeks, V404 Cygni displayed spectacular variability from the radio through the gamma-ray (e.g., Mooley et al 2015;Motta et al 2015;Rodriguez et al 2015;Roques et al 2015;Tetarenko et al 2015b;Trushkin et al 2015;Gandhi et al 2016;Jenke et al 2016;Kimura et al 2016;Martí et al 2016;Walton et al 2016), while also launching powerful outflows in the form of ballistic synchrotron jets (Tetarenko et al 2015c) and fast disk winds (King et al 2015;Muñoz-Darias et al 2016). During these two weeks, V404 Cygni also contained a high column of absorbing material (» -10 cm 24 2 ), likely caused by material expelled from the accretion disk obscuring the central engine ).…”