Synchrotron emission from double-peaked radio light curves of the symbiotic recurrent nova V3890 Sagitarii.

We present radio observations of the symbiotic recurrent nova V3890 Sagitarii following the 2019 August eruption obtained with the MeerKAT radio telescope at 1.28 GHz and Karl G. Janksy Very Large Array (VLA) at 1.26−35 GHz. The radio light curves span from day 1 to 540 days after eruption and are dominated by synchrotron emission produced by the expanding nova ejecta interacting with the dense wind from an evolved companion in the binary system. The radio emission is detected early on (day 6) and increases rapidly to a peak on day 15. The radio luminosity increases due to a decrease in the opacity of the circumstellar material in front of the shocked material and fades as the density of the surrounding medium decreases and the velocity of the shock decelerates. Modelling the light curve provides an estimated mass-loss rate of |${\overset{\hbox{$\bullet $}}{M}}_{\textrm {wind}} \approx 10^{-8}\, {\textrm {M}}_\odot ~{\textrm {yr}}^{-1}$| from the red giant star and ejecta mass in the range of M ej = 10−5––10−6 M⊙ from the surface of the white dwarf. V3890 Sgr likely hosts a massive white dwarf similar to other symbiotic recurrent novae, thus considered a candidate for supernovae type Ia (SNe Ia) progenitor. However, its radio flux densities compared to upper limits for SNe Ia have ruled it out as a progenitor for SN 2011fe like supernovae. [ABSTRACT FROM AUTHOR]