No abstract

The division of responsibilities between different institutions in the Whipple Gamma Ray Collaboration are listed below; however these are only guidelines and the divisions are not hard and fast. The observing program is agreed upon by the collaboration in biannual meetings in which all groups are represented. The observing mode and data reduction method to be used is also agreed upon at that time. The ongoing observing program is the prime responsibility of the local Smithsonian group (aided by the resident lSU postdoc, David Bird). This involves the detailed scheduling of observing (sources and observers). Fast-look analysis is performed locally and the data is prepared for distribution to the five other centers. The local group is responsible for routine maintenance of the telescopes and cameras. Observing is shared by all groups with visiting observers sharing shifts with local staff. Responsibility for data reduction on specific sources is assumed by individuals within the collaboration. Usually students are assigned specific sources for dissertation studies. Data on each source is independently reduced by at least two observers. New data reduction methods are developed and distributed for routine analysis. Some centers take responsibility for specific tasks e.g. spectrum analysis (ISU, Leeds), periodicity analysis (Michiga;n, Leeds), etc. Technical aspects of the experiment are the responsibility of the individual groups e.g. 11m electronics (Michigan), 10m electronics (SAO), phototubes (ISU), cabling (Purdue), tracking control, ccd cameras (UCD), data acquisition software (Leeds), CAMAC interface (Purdue), data acquisition upgrades (ISU), 10m optics (SAO), 11m optics (ISU, Michigan), etc. Simulations were originally the responsibility of lSU and Leeds; they are now carried out at all centers. Long-term planning has been the responsibility of Purdue. All groups are involved in the design studies for the Phase I development. Progress Reports: Science The May 1994 Markarian Flare at Whipple and EGRET Energies Since its discovery by us at TeV energies (Punch et al. 1992), we have continued a program of monitoring the emission from Markarian 421, coordinated with observations taken by the EGRET detector. (These coordinated observations are partially supported by NASA Gamma Ray Observatory guest investigator grants.) In May 1994, an outburst was detected in which the intensity of the source increased by nearly an order-of-magnitude over its pre-outburst, "quiescent" level. A paper describing these results has now been accepted for publication in the Astrophysical Journal Letters, and a copy in included in the appendix.

No abstract

No abstract

Very high energy gamma-ray emission from the BL Lac object Markarian 421 has been detected over three observing seasons on 59 nights between April 1992 and June 1994 with the Whipple 10-meter imaging Cherenkov telescope. During its initial detection in 1992, its flux above 500 GeV was 1.6$\times$10$^{-11}$photons cm$^{-2}$ s$^{-1}$. Observations in 1993 confirmed this level of emission. For observations made between December 1993 and April 1994, its intensity was a factor of 2.2$\pm$0.5 lower. Observations on 14 and 15 May, 1994 showed an increase over this quiescent level by a factor of $\sim$10 (Kerrick et al. 1995). This strong outburst suggests that 4 episodes of increased flux measurements on similar time scales in 1992 and 1994 may be attributed to somewhat weaker outbursts. The variability of the TeV gamma-ray emission from Markarian 421 stands in contrast to EGRET observations (Lin et al. 1994) which show no evidence for variability.Comment: gzip compressed tar file including LaTeX text and 4 postscript figures (14 pages total incl. 4 tables), accepted for publication in the Astrophysical Journal. Contact address is schubnel@umich.ed