H2O Maser Outflow from the Red Supergiant Star NML Cygni Observed with Japanese VLBI Network

作者：Nagayama Takumi^*; Takeda Koji; Omodaka Toshihiro; Imai Hiroshi; Kameno Seiji; Sofue Yoshiaki; Doi Akihiro; Fujisawa Kenta; Habe Asao; Honma Mareki; Kawaguchi Noriyuki; Kawai Eiji; Kobayashi Hideyuki; Koyama Yasuhiro; Murata Yasuhiro; Sorai Kazuo; Sudou Hiroshi; Takaba Hiroshi; Tamura Sayaka; Wakamatsu Ken ichi

来源：Publications of the Astronomical Society of Japan, 2008, 60(5): 1069-1075.

• masers
• stars: individual (NML Cygni)
• stars: kinematics
• stars: supergiants

We present the proper motions of H2O masers in NML Cygni, observed with the Japanese VLBI Network at three epochs spanning 455 d. We detected about 15 maser features at each epoch. Overall, 13 features that were detected at least twice were tracked by their radial velocities and proper motions. The three-dimensional kinematics of the maser features indicate the presence of an expanding outflow. The major axis of the outflow is estimated to be at a position angle of similar to 108 degrees, and an inclination angle of similar to 8 degrees with respect to the line of sight. The H2O masers are located between an apparent minimum radius of similar to 9.6 x 10(12) m (64 AU) and a maximum radius of similar to 3.0 x 10(13) m (202 AU), where the expansion velocity increases from 12 to 27 km s(-1). A comparison with the distributions of SiO, H2O, and OH masers suggests that the outflow of NML Cygni is expanding outside a radius of similar to 1.5 x 10(13) m 100 AU. This radius corresponds to 6 stellar radii, and is consistent with the radius of the inner boundary for the dust shell.

• 出版日期2008
• 单位中国科学院国家天文台