出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：We present the latest results of a multi-line study of SiO circumstellar masers in oxygen-rich
AGB stars using the VLBA. In particular, we have studied several maser lines at 43 GHz (v=1
and v=2) and at 86 GHz (v=1 and v=2) of 28SiO, and for the first time we have been able to map
the emission of the ground state v=0 J=1–0 of 29SiO and the v=2 J=2–1 maser line of 28SiO. In
TXCam, the 3-mm emission is produced in an outer region of the circumstellar envelope, as it
has been already observed in other late-type stars. We also discuss the importance of these new
detections in the framework of the SiO maser pumping models.
