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Bulgarian Journal of Physics
Print: 1310-0157 Online: 1314-2666
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RECOGNIZED BY THE EUROPEAN PHYSICAL SOCIETY 
Bulg. J. Phys. vol.51 no.3 (2024), pp. 263-267
Pre-Outburst Signal in the Light Curves of the Recurrent Novae RS~Oph and T~CrB
R.K. Zamanov1, V. Marchev1, J. Marti2, G. Latev1
1Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, Tsarigradsko Shose 72, BG-1784 Sofia, Bulgaria
2Departamento de Fisica, Escuela Politecnica Superior de Jaen, Universidad de Jaen, Campus Las Lagunillas, A3, 23071, Jaen, Spain
go back1Institute of Astronomy and National Astronomical Observatory, Bulgarian Academy of Sciences, Tsarigradsko Shose 72, BG-1784 Sofia, Bulgaria
2Departamento de Fisica, Escuela Politecnica Superior de Jaen, Universidad de Jaen, Campus Las Lagunillas, A3, 23071, Jaen, Spain
Abstract. Pre-outburst signal (a decrease of the optical brightness) just before the outburst is clearly detected in the observations of the T CrB obtained before and during the 1946 outburst. A similar decrease is also visible in the light curve of RS Oph during the 2021 outburst. We suppose that this is due to formation of a thick, dense envelope around the white dwarf, and we estimate its size (1000-2000 km), mass (5×10-8 - 6×10-7 M⊙) and average density (5-16 g/cm3).