射电天文研究室知识库

The water maser emission from the unusual supergiant, VY CMa, has been observed with the Urumqi 25m radio telescope. A simple redshifted maser spectrum was detected in the 1.6 Jy noise level during our monitoring observations. All of the H2O maser features are redshifted with respect to the VY CMa stellar velocity of I 7.6 km .s(-1). The spectrum appears to consist of two striking like groups and each group has three features. The appearances and the ratio of these three features in the two maser groups are very similar. The H2O maser emission arises from a region close to the supergiant, about 10 stellar radii of the star. The simple redshifted spectrum could be due to infall masing gas on the near side of the disk. Pulsation of the central star causes oscillations in this portion of the envelope, with the shock wave propagating outward and with material falling inward. The masing gas motions are very complex, by which the dramatic changes or the quasi-sinusoidal fluctuation in Aux may be explained.