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C. J. Vicenik (University of Texas at Austin; Maria Mitchell Obs.), V. Strelnitski (Maria Mitchell Obs.)
The recently discovered unusual SiO maser source IRAS 19312+1950 was observed in several masing and quasi-thermal molecular radio lines with the 37m Haystack and 12m Steward Observatory radio telescopes in the summer of 2003. We confirm the suspected strong variability of the SiO masers in the J=1-0, v=1 and v=2 transitions and the "double-peaked" profile of these spectra. However, instead of the two narrow peaks at V(LSR)= 25 and 53 km/s observed before, we find two relatively broad (approx. 6-7 km/s wide ) regions of maser activity at 19-25 and 46-53 km/s. Narrow (1-2 km/s) and strongly variable peaks appear and disappear within these velocity intervals, with a time scale of no longer than 1 year and, possibly, considerably shorter. Narrow H2O maser peaks appear within the same velocity intervals. The two observed SiO transitions in its v=0 vibrational state (J=1-0 and J=2-1) show broad (15-20 km/s) spectral profiles centered at approx. V(LSR) = 36 km/s. We consider them to be quasi-thermal lines from a large expanding envelope of the source and thus we adopt V(LSR)=36 (+/-3) km/s as the radial velocity of the source. The two spectral regions of maser activity are located symmetrically relative to this radial velocity, and we suppose their velocity shift may be a result of rotation and/or expansion of the inner circumstellar molecular shell. More definite conclusions require interferometric mapping and simultaneous monitoring of the source in the masing lines and IR continuum - both planned projects. This project was supported by the NSF/REU grant AST-0097694 and the Nantucket Maria Mitchell Association.
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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.