Fading of V651 Mon

From Danie Overbeek dao@pixie.co.za

The above star appears to have reverted to its eclipsing mode.
1996 Sept 14.1    Mag 11.3
          16.0        11.3
          25.101      12.5
          26.089      12.0

On the fading

(vsnet-alert 550)

V651 Mon

V651 Mon is a binary central star of the planetary nebula NGC 2346. The 15.991-day binary consists of an A5V star and a hot (Te about 10^5K) subdwarf. This binary has received special attention since its fading (or eclipsing) episode starting in 1981 (Kohoutek 1982). The fadings recurred with the orbital period. Subsequent observations lead to a picture of a passing cloud in front of the binary: eclipses in the visual light occur when the orbiting A5V star passes behind the cloud (a good review article: Costero et al. 1986, Rev. Mexicana Astron. Astrof. 13, 149). Costero et al. expects from the amount of the dust from IRAS observations that the probability of such passages are very rare. In fact plate searches could not detect any similar events between 1899 and 1981.

Since the present fading episode may provide a unique chance in probing dust condensations (or planetesimals) around highly evolved stars (recall the recent fine images of such bodies in NGC 7293 by HST), observations in all wavelengths are urged. From the epoch of the fading by D. Overbeek, the next eclipse in the visual light will occur around Oct. 11. The UV eclipses will occur 8 days before and after this.

Regards,
Taichi Kato