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M. J. Claussen (NRAO), K. R. Healy, S. Starrfield (ASU), H. E. Bond (STScI)
The outburst of the enigmatic eruptive variable V838 Monocerotis in early 2002 has been followed by expansion of the star to supergiant dimensions with a very cool photosphere and copious dust formation. We report on observations of V838 Mon in the J = 1 arrow 0, v = 1 and v = 2 SiO maser emission lines at 43 GHz. Using the NRAO Very Large Array (VLA), we did not detect SiO emission in November 2003. Deguchi et al. (2005) made the first positive detection in February 2005 using the Nobeyama 45m radio telescope, and the SiO masers had strengthened by April 2005. We made a VLA observation in September 2005 and found that the SiO lines had further strengthened by factors of 3--5 relative to April 2005. The spectra have a narrow peak (velocity width ~1 km/s) superposed on a pedestal of about 10 km/s (FWZI). The overall profile appears typical of that seen from AGB/Mira circumstellar envelopes, where the masers are found within a few stellar radii above the photosphere. We will present results from continued VLA monitoring of V838 Mon, as well as results of a sensitive search for high-velocity SiO maser features using the NRAO Green Bank Telescope, and the first direct images of the masers using the NRAO Very Long Baseline Array.
The NRAO is operated by Associated Universities, Inc. under cooperative agreement with the National Science Foundation. SS acknowledges partial support to ASU from the NSF and NASA.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.