VERA Observation of the W49N H2O Maser Outburst in 2003 October

We report on a strong outburst of the W49N H2O maser observed with VERA. Single-dish monitoring with VERA 20 m telescopes detected a strong outburst of the maser feature at V_LSR = -30.7 km/s in 2003 October. The outburst had a duration of ~100 days and a peak intensity of 7.9 x 10^4 Jy, being one of the strongest outbursts in W49N observed so far. VLBI observations with the VERA array were also carried out near to the maximum phase of the outburst, and the outburst spot was identified in the VLBI map. While the map was in good agreement with previous studies, showing three major concentrations of maser spots, we found a newly formed arc-like structure in the central maser concentration, which may be a shock front powered by a forming star or a star cluster. The outburst spot was found to be located on the arc-like structure, indicating a possible connection of the present outburst to a shock phenomenon.Comment: 4 pages, 2 figures included, to appear in PASJ letter (Vol.56, #3, 2004 June

INFRARED DIODE LASER SPECTROSCOPY OF NaCl

$^{1}$ G. Thompson, A. G. Maki, and A. Weber, J. Mol. Spectrosc. 118, 540 (1986). $^{2}$ P.L. Clouser and W. Gordy, Phys. Rev. A 134, 863 (1964).Author Institution: Department of Chemistry, Josai University, Keyakidai; Research Institute for Catalysis, Hokkaido UniversityA heat-pipe high temperature cell was incorporated into an optical system of a tunable diode laser spectrometer which covered an infrared range of $350-800 cm^{-1}$. The heat-pipe cell was made of an alumina tube and was similar in construction to that used by Maki $et al.^{1}$ Vibration-rotation spectrum of NaCl was observed in the gas phase under temperatures of 1153-1223 K. The spectral lines in the region of $365-390 cm^{-1}$ were measured. The analysis of the $v=l-0, 2-1, 3-2$, and 4-3 bands of $Na^{35}Cl$ has yielded accurate values of $\omega_{e}, \omega_{e}x_{e}$, and $\omega_{e}y_{e}$ the former two of which are in excellent agreement with those derived in a millimeter-wave molecular-beam $study.^{2}$ Under the high temperature, a small amount of $H_{2}O$ which could not be removed from the sample gas reacted with NaCl to have yielded the spectrum of NaOH. Some results of the spectra of NaOH and a related molecule of LiOH will be shown