Discovery of Strong Vibrationally Excited Water Masers at 658 GHz toward Evolved Stars

We report the astronomical discovery of the 110→101 rotational transition within the ν2 = 1 vibrationally excited state of water vapor (H2O). Using the 10.4 m telescope of the Caltech Submillimeter Observatory, we detect strong maser emission in this line, which has a frequency near 658 GHz, toward a diverse sample of oxygen-rich red giant and supergiant stars. In circumstellar envelopes these 658 GHz H2O masers appear to be as common as SiO masers and H2O masers in other transitions, while we fail to detect 658 GHz H2O emission toward the W49 N and W51 N star-forming regions. For all of the 11 stars detected, the luminosity in the 658 GHz H2O transition is comparable to or higher than the luminosity of any other known SiO or H2O maser line.

[1]  J. Moran,et al.  Interferometric Observations of the SiO Masers and Dust Shell of VX Sagittarii , 1995 .

[2]  R. Hills,et al.  Submillimetre water masers in circumstellar envelopes , 1995 .

[3]  A. Tielens,et al.  Molecular rotational line profiles from oxygen-rich red giant winds , 1994 .

[4]  A. Kemball,et al.  Observation of a Ring Structure in SiO Maser Emission from Late-Type Stars , 1994 .

[5]  P. Bowers,et al.  VLA positions and distributions of H2O masers associated with 15 Mira and semiregular variables , 1994 .

[6]  J. W. Kooi,et al.  A lownoise 665 GHz SIS quasi-particle waveguide receiver , 1994 .

[7]  K. Menten,et al.  Discovery of interstellar water lines at 437, 439, and 471 GHz : strong case for water maser formation behind C-type shocks , 1993 .

[8]  K. Menten,et al.  The excitation of vibrationally excited H 2 O masers. , 1993 .

[9]  R. Lees,et al.  Observations of new submillimeter maser lines of water and methanol , 1993 .

[10]  M. Elitzur,et al.  Modeling SiO Maser Emission from Late-Type Stars , 1992 .

[11]  Eric Herbst,et al.  Millimeter- and submillimeter-wave spectrum of highly excited states of water , 1991 .

[12]  K. Menten,et al.  321 CHz submillimeter water masers around evolved stars , 1991 .

[13]  P. Benson,et al.  A Catalog of Observations for Stellar Masers , 1990 .

[14]  Gary J. Melnick,et al.  A new submillimeter water maser transition at 325 GHz , 1990 .

[15]  S. Deguchi,et al.  H2O emission from evolved stars at the far-infrared and submillimeter wavelengths , 1990 .

[16]  K. Menten,et al.  A subarcsecond H2O maser shell surrounding a variable star , 1990 .

[17]  W. Welch,et al.  Absolute positions of SiO masers , 1990 .

[18]  J. Stutzki,et al.  Detection of an isotopic short submillimeter CO line - Column densities of warm gas in molecular clouds , 1990 .

[19]  K. Menten,et al.  Submillimeter water masers , 1990 .

[20]  K. Menten,et al.  Hot water around late-type stars - Detection of two millimeter-wave emission lines from the nu2 vibrationally excited state , 1989 .

[21]  Francis J. Lovas,et al.  NIST Recommended Rest Frequencies for Observed Interstellar Molecular Microwave Transitions -- 2002 Revision , 1986 .

[22]  Frank C. De Lucia,et al.  Continuously tunable coherent spectroscopy for the 0.1–1.0‐THz region , 1983 .

[23]  T. Barnes,et al.  Infrared spectroscopy of Mira variables. II. R Leonis, the H/sub 2/O vibration-rotation bands , 1979 .

[24]  N. Scoville,et al.  OH-IR stars. I. Physical properties of circumstellar envelopes , 1976 .

[25]  D. W. Strecker,et al.  SPECTROSCOPIC AND PHOTOMETRIC OBSERVATIONS OF M SUPERGIANTS IN CARINA. , 1972 .