Аннотация:We report a rapid decline in the brightness of the red nova remnant V838 Mon following its light maximum around September 25, 2025 (B = 15.03, V = 12.75, RC = 10.70, IC = 8.48 mag). On 2026 Feb 20.832 UT, the magnitudes decreased to B = 16.29, V = 14.10, RC = 11.78, IC = 9.05 mag. The mean fading rate over the past two months is 0.011 ± 0.001 mag over a day in filter V. Photometry was obtained with 0.5–1-m telescopes. Optical spectra secured on 2025 Dec 06.052 UT and 2026 Feb 19.00 UT with the SAO 1-m and SAI 2.5-m telescopes correspond to an M5-type supergiant with strong TiO molecular bands and Hα emission.The progenitor of V838 Mon was identified as a binary system composed of two B3V-type stars; the more luminous component underwent a red nova outburst in 2002 (ATel #803, #964, #966, #1821, #1996, and #2211; Astrophys. Bull., vol.75, 325, 2020). By 2007, the less luminous component became engulfed by the expanding envelope. Since then, the remnant has evolved as an M-type supergiant with a hot B3V companion embedded within a common envelope.Since 2015, we have detected quasi-periodic variability in the IC band with a characteristic period of about six months. The amplitude of this variability has steadily increased and extends toward shorter wavelengths. We suggest that these brightness variations are associated with the formation of a hot region on the surface of the common envelope above the embedded companion and possible contraction of the envelope. The observed fading is consistent with the passage of this hot region toward the limb and onto the far side of the common envelope due to orbital motion. Around February 23, 2026, the decline ceased, possibly indicating that the hot region had fully rotated out of view. The largest brightness decrease occurred at shorter wavelengths.
