658 GHz Vibrationally-Excited Water Masers with the Submillimeter Array

Abstract

Discovered in 1995 at the Caltech Submillimeter Observatory (CSO), the vibrationally-excited water maser line at 658 GHz (455 micron) is seen in oxygen-rich giant and supergiant stars. Because this maser can be so strong (up to thousands of Janskys), it was very helpful during the commissioning phase of the highest frequency band (620-700 GHz) of the Submillimeter Array (SMA) interferometer. From late 2002 to early 2006, brief attempts were made to search for emission from additional sources beyond the original CSO survey. These efforts have expanded the source count from 10 to 16. The maser emission appears to be quite compact spatially, as expected from theoretical considerations; thus these objects can potentially be used as atmospheric phase calibrators. Many of these objects also exhibit maser emission in the vibrationally-excited SiO maser at 215 GHz. Because both maser lines likely originate from a similar physical region, these objects can be used to test techniques of phase transfer calibration between millimeter and submillimeter bands. The 658 GHz masers will be important beacons to assess the performance of the Atacama Large Millimeter Array (ALMA) in this challenging high-frequency band.

8 pages, 6 figures, 3 tables; based on an oral presentation at IAU conference 242: Astrophysical Masers and Their Environments, held in Alice Springs, Australia (March 2007)

References in corpus (8)

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• Submillimeter vibrationally excited water emission from the peculiar red supergiant VY CMa
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• Inward Motions of the Compact SiO Masers Around VX Sagittarii
• 654 GHz Continuum and C18O (6-5) Observations of G240.31+0.07 with the Submillimeter Array
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Cited by in corpus (5)

• ALMA sub-mm maser and dust distribution of VY Canis Majoris
• ATOMIUM: Probing the inner wind of evolved O-rich stars with new, highly excited H${}_2$O and OH lines
• Vibrationally excited water emission at 658 GHz from evolved stars
• Submillimetre water masers at 437, 439, 471, and 474 GHz towards evolved stars. APEX observations and radiative transfer modelling
• Molecules and Chemistry in Red Supergiants