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Unpredicted outburst of the symbiotic binary V694 Mon (MWC560)статья
- Авторы: Goranskij V.P., Zharova A.V., Barsukova E.A., Burenkov A.N.
- Журнал: The Astronomer’s Telegram
- Номер: 12227
- Год издания: 2018
- Первая страница: 1
- Последняя страница: 1
- Аннотация: The symbiotic binary V694 Mon shows regular outbursts with the period of 1930 days (Doroshenko et al., IBVS No.3824, 1993) above the secular trend of brightening from B = 14.1 mag in 1898 to B = 9.25 mag in 2016. The star reached the breaking-record brightness in the last 2016 outburst (ATel#8653) predicted with the known period. Broad and deep blue-shifted absorption components of Balmer emission lines in the spectra formed by high-velocity jets, and strong flickering of brightness in the scales of minutes and hours with the amplitude up to 0.8 mag in the V band and 1.0 mag in the U band are typical for this star. On 2018 Nov 4.12 UT we observed brightening of the star up to the UBVRc magnitudes of (9.15, 9.57, 9.25, 8.50), consequently. Observations were performed with the SAO 1-m Zeiss telescope and CCD photometer. Additional analysis of the photometry taken with the 50-cm Maksutov telescope of the Moscow University Crimean Station along with SAO data found the star in this state in five nights between 2018 Oct 11 and Nov 5. Its V brightness varied less than 0.07 mag, what suggests the disappearance of flickering. A previous observation taken on 2018 May 2 at the end of the past observational season gave UBVRc = (10.31, 10.52, 10.22, 9.41), and flickering was then observed. The recent brightening happened at the phase of 0.52 of 1930-day period, and it was not predicted. The spectral observations were performed with the SAO 1-m telescope and UAGS spectrograph. In the spectra of V694 Mon taken around 2018 Nov 16.04 UT in the range between 3870 and 5280 Å with the spectral resolution of 2.2 Å, we found the radical changes in comparison with the spectra of the previous season. No high-velocity absorption components are seen. Hβ line has wide emission shoulders spreading to the velocities up to 1000 km/s in both sides from the line center. There is a weak absorption component at the velocity of -260 km/s relative to the peak of the emission. Higher-number Balmer lines do not have emission shoulders but have the absorption components at the velocity of -260 km/s. The depths of them increase with the number. Wide and shallow He I absorptions changed to narrower ones located on the velocity of -260 km/s. Peaks of the Fe II emission lines are shifted by -50 km/s relative to the peaks of Balmer lines. The same features are presented in the UAGS spectrum taken on 2018 Oct 17.10 UT in the range of 3800 - 7880 Å with the lower resolution of 6.2 Å/pxl. While the last spectra taken at the past season from January 9 to March 9, 2018 looked typical for this star with the high-velocity absorption components. We explain this active state of the V694 Mon system as an episode of the formation of a common envelope due to the transit of the system to a dynamical mode of accretion with an increased rate. The accretion matter filling the Roche lobe of the compact companion blocked the jets and overlapped the direct visibility of the companion, so flickering was deleted. The shell of the companion generates a stellar wind with the velocity of 260 km/s. We observed similar episodes in the relativistic jet binary SS 433 with blocking jets and even the disappearance of eclipses. In SS 433, these episodes finish with an ejection of the envelope.
- Добавил в систему: Горанский Виталий Петрович