An Experiment to Locate the Site of TeV Flaring in M87
  We describe a Chandra X-ray ToO project designed to isolate the site of TeV
flaring in the radio galaxy M87. To date, we have triggered the Chandra
observations only once (2010 April) and by the time of the first of our 9
observations, the TeV flare had ended. However, we found that the X-ray
intensity of the unresolved nucleus was at an elevated level for our first
observation. Of the more than 60 Chandra observations we have made of the M87
jet covering 9 years, the nucleus was measured at a comparably high level only
3 times. Two of these occasions can be associated with TeV flaring, and at the
time of the third event, there were no TeV monitoring activities. From the
rapidity of the intensity drop of the nucleus, we infer that the size of the
emitting region is of order a few light days times the unknown beaming factor;
comparable to the same sort of estimate for the TeV emitting region. We also
find evidence of spectral evolution in the X-ray band which seems consistent
with radiative losses affecting the non-thermal population of the emitting
electrons within the unresolved nucleus.
