Interferometric Observation of the Highly Polarized SiO Maser Emission from the $v=1, J=5-4$ Transition Associated with VY Canis Majoris

Hiroko Shinnaga; James M. Moran; Ken H. Young; Paul T. P. Ho

doi:10.1086/425133

paper

Interferometric Observation of the Highly Polarized SiO Maser Emission from the $v = 1, J = 5 - 4$ Transition Associated with VY Canis Majoris

arXiv:astro-ph/0408298 · doi:10.1086/425133

Abstract

We used the Submillimeter Array to image the SiO maser emission in the $v = 1$ , $J=5-4 $t r an s i t i o na ssoc ia t e d w i t h t h e p ec u l ia r r e d s u p er g ian t V Y C ani s M aj or i s . W e i d e n t i f i e d se v e nma ser co m p o n e n t s an d m e a s u r e d t h e i r r e l a t i v e p os i t i o n s an d l in e a r p o l a r i z a t i o n p r o p er t i es . F i v eo f t h e ma ser co m p o n e n t s a r eco in c i d e n tt o w i t hinab o u t 150 ma s ($ \sim $200 A U a tt h e d i s t an ceo f 1.5 k p c); m os t o f t h e mma y or i g ina t e in t h ec i r c u m s t e l l a r e n v e l o p e a t a r a d i u so f ab o u t 50 ma s f r o m t h es t a r a l o n g w i t h t h e S i O ma ser s in t h e l o w es t r o t a t i o na l t r an s i t i o n s . O u r m e a s u r e m e n t ss h o w t ha ttw oo f t h e ma ser co m p o n e n t s ma y b eo f f se t f r o m t h e inn er s t e l l a r e n v e l o p e (a tt h e 3$ σ $l e v e l o f s i g ni f i c an ce) an d ma y b e p a r t o f a l a r g er bi p o l a r o u t f l o w a ssoc ia t e d w i t hV Y C M ai d e n t i f i e d b y S hinna g a e t a l . T h es t r o n g es t ma ser f e a t u r e a t a v e l oc i t y o f 35.9 k m s$ ^{-1}$ has a 60 percent linear polarization, and its polarization direction is aligned with the bipolar axis. Such a high degree of polarization suggests that maser inversion is due to radiative pumping. Five of the other maser features have significant linear polarization.

13 pages in total, 3 figures, 1 table; last two paragraphs has been replaced; accepted for publication in the ApJL; Also available at http://cfa-www.harvard.edu/~hshinnaga/hshinnaga-sma-vycma-sio54v1.pdf and http://cfa-www.harvard.edu/~hshinnaga/hshinnaga-sma-vycma-sio54v1.ps

Interferometric Observation of the Highly Polarized SiO Maser Emission from the v=1,J=5−4 Transition Associated with VY Canis Majoris

Abstract

Interferometric Observation of the Highly Polarized SiO Maser Emission from the $v = 1, J = 5 - 4$ Transition Associated with VY Canis Majoris