New Directions in Gamma Ray Astronomy above 10$^{14}$ eV
Session 33 -- Gamma-Rays and Cosmic Rays
Display presentation, Tuesday, 9:30-6:30, Heller Lounge Room

## [33.11] New Directions in Gamma Ray Astronomy above 10$^{14}$ eV

\newbox\grsign \setbox\grsign=\hbox{$>$} \newdimen\grdimen \grdimen=\ht\grsign \newbox\simlessbox \newbox\simgreatbox \setbox\simgreatbox=\hbox{\raise.5ex\hbox{$>$} \llap {\lower.5ex\hbox{$\sim$}}} \ht1=\grdimen\dp1=0pt \setbox\simlessbox=\hbox{\raise.5ex\hbox{$<$} \llap {\lower.5ex\hbox{$\sim$}}} \ht2=\grdimen\dp2=0pt \def\simgreat{\mathrel{\copy\simgreatbox}} \def\simless{\mathrel{\copy\simlessbox}} \newbox\simppropto \setbox\simppropto=\hbox{\raise.5ex\hbox{$\sim$} \llap {\lower.5ex\hbox{$\propto$}}} \ht2=\grdimen\dp2=0pt \def\simpropto{\mathrel{\copy\simppropto}} K.G. Gibbs, A.Borione, C.E.Covault, J.W.Cronin, B.E.Fick, T.A.McKay, B.J.Newport, R.A.Ong, L.J Rosenberg (EFI,U of Chicago), M.Catanese, K.D.Green, J.Matthews, D.Nitz, D.Sinclair, J.C. van der Velde (U of Michigan), D.B.Kieda (U of Utah)

The Chicago Air Shower Array (CASA) is the world's largest experiment for detecting extensive air showers from cosmic rays and gamma rays at 100 TeV energies. CASA operates in coincidence with a large area underground muon detector (MIA), thus making possible a significant degree of cosmic ray background rejection. CASA was designed to search for point sources of gamma rays, such as Cygnus X-3 and Hercules X-1, for which detections were claimed by a number of smaller experiments during the early 80's. However, analysis of CASA-MIA data from February 1989 through April 1991 shows no evidence for point sources, and CASA limits for continuous emission are significantly lower than have been previously reported. While the search for galactic point sources continues, we are pursuing several new classes of potential ultra-high energy gamma ray sources. Recent work includes a search for diffuse emission resulting from the interaction of galactic cosmic rays with large molecular clouds, a search for coincident emission from gamma ray bursts detected by the BATSE experiment, and a search for emission from extragalactic sources (AGN) detected by the EGRET experiment. At least one such source has been detected at TeV energies by the Whipple air \`{C}erenkov experiment. Observations of several AGN at 10-100 TeV might be used to probe the time-evolution of the CMBR. We present preliminary results for searches from all of these sources and summarize the implications for cosmic ray origins and cosmology.