> You need to tell us the interval between observations.

Our final goal is to illustrate detailed structure of an AGN torus which is
composed by a mixture of molecular and ionized gas. Molecular and ionized gas
can be probed be H2O maser and free-free absorption, respectively.
In the target source, NGC 1052, we discovered an emerging narrow maser feature
whose flux density probably increased 16% in 3 days. At the same time, continuum
flux density also increased by 21%. We consider these variations are caused by
changes of optical depth along the line of sight toward the continuum photon
source, which is a counter-jet knot running behind inhomogeneous gaseous torus.
To confirm this model and illustrate gas structure of the torus, we requested
an H2O maser monitoring using GBT and VLBA imaging-monitor with VLBA.
We focus sensitive spectral variations with GBT, which we trace positions of
jets and masers with VLBA. Free-free opacity map will be also taken by multi-
frequency VLBA observations.

The interval of 10 days is derived from the time scale of the emerged narrow
maser feature. We probably detected flux variation, 16% in 3 days, of the narrow
feature. The time scale will be 2 x 10^6 sec, i.e. 23 days. We consider
it is adequate to set the interval half of the time scale.
Although positional shift of jets and maser spots would be hardly detected in
this interval (jet would move 0.1 mas in 10 days), we'd like to see flux
variations of individual maser spots and knots.

The monitoring observation with GBT has already started since Nov 3 and continues
until Dec 28. I hope VLBA observations will catch up as soon as possible.

 KAMENO Seiji : kameno@hotaka.mtk.nao.ac.jp
 < Space VLBI Project > National Astronomical Observatory
National Institutes of Natural Sciences
2-21-1 Osawa, Mitaka, Tokyo 181-8588 JAPAN
                           TEL: +81-422-34-3631
                           FAX: +81-422-34-3596