The photometric evolution of the final helium flash object V4334 Sgr from 1994 to 2001 is described. The rise to optical maximum (1994-1996) is characterized by a continuous increase of color indices, indicating a slowly expanding, cooling pseudo-photosphere. This photosphere became stationary in 1997. In the following years, the object underwent brightness declines of increasing strength, which are similar in character to the "red declines'' of R CrB stars. The fading of V4334 Sgr is more dramatic than any brightness decline of an R CrB star. Most radiation is absorbed by the dust envelope and re-radiated in the infrared; at present only 10^-5 of the visual light reaches the observer. The sparse optical data of 2000 and 2001 indicate that the increase of obscuration has begun to slow down. The light curve of V4334 Sgr is similar to that of the final helium flash object V605 Aql which erupted in 1919. Refinements of theoretical models are required to explain the rapid evolution of these final helium flash objects.
Observational Aspects of Pulsating B- and A Stars
- Pub Date:
- February 2002