Possible new water maser flare in W49
Eduard Mol
Hi all,
For a few years I have been tracking the water masers in the star forming region Westerhout 49. Its spectrum has many different features, representing different maser clouds in the region.
Today I made a new observation of the region at 22.2GHz. Already during the recording I noticed something unusual. One feature was very obviously visible in the IFaverage window with only 1 minute of integration time. One could have easily mistaken it for the hydrogen line :-) (The spike on the left is a reference signal used to correct frequency drifting of the LNB LO).
I just did a quick processing of the data. The integration time is about 42 minutes. I have attached a plot showing the spectrum from previous observations over the past few months, plus the new one from today.
In recent months the peak at 6.9 km/s appears to have steadily increased in brightness, and is now by far the brightest feature. Of course my measurements are not calibrated to flux density so some change in the levels due to different atmospheric absorption or pointing errors would be expected. However, the cluster of features near -5 to -10 km/s has remained relatively stable over the past few months. So the rise of the 6.9 km/s feature (at least relative to the other features) is probably real. Apparently, whatever event triggered the possible new flare at 6.9 km/s has not had an effect on the other group of masers at -5 to -10 km/s.
Anyway, it will be interesting to continue observing this source over the coming weeks and months.
fasleitung3
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