SIMBAD references

The photometric behaviour of the irregular variable Herbig Ae star V 351 Ori was investigated combining data from the literature with new photometric data in the Stroemgren system. It is shown that this enigmatic object changed its photometric behaviour from that of a Herbig Ae star with strong photometric variations, due to extinction by circumstellar dust clouds, to that of an almost non-variable star. Such a behaviour is not unique; it has been found also in the star BN Ori (Shevchenko et al. 1996). This suggests that such transitions must occur quite often during the evolution of intermediate mass HAeBe stars towards the main-sequence (MS). However, it is equally probable that before such a star arrives at the MS, it will become strongly variable again after collecting enough dust from its environment. During the process of V 351 Ori's transition from a Herbig Ae star with strong photometric variations to a non-variable one, the maximum brightness in the Stroemgren v, b and y magnitudes decreased, whereas that in u increased, causing a strong blueing effect in the colour-magnitude diagrams. It should be noted that this effect happened at a decrease in visual brightness by about 0.2mag magnitude only. It is therefore caused by a different mechanism than that in V 351 Ori before the transition and in UX Ori type stars, where the blueing effect occurs at a decrease in V of about 2.5mag. The transition, from a strongly variable star to the state in which V 351 Ori is nearly constant at a level equal to that of its maximum brightness before the transition, happened very fast (within 50 days), and went along the interstellar reddening line in the colour-magnitude diagrams. A provisional model to explain V 351 Ori's behaviour, in which it is assumed that a temporarily strong accretion of matter onto the star took place, is proposed.