STACEE Observations of Markarian 421 during an Extended Gamma-Ray Outburst

The active galaxy Markarian 421 underwent a substantial outburst in early 2001. Between January and May of that year, the STACEE detector was used to observe the source in γ-rays between the energies of 50 and 500 GeV. These observations represent the lowest energy γ-ray detection of this outburst by a ground-based experiment. Here we present results from these observations, which indicate an average integral γ-ray flux of (8.0 ± 0.7 ± 1.5) × 10-10 cm-2 s-1 above 140 GeV. We also present a light curve for Markarian 421 as observed by STACEE from March to May and compare our temporal, as well as spectral, measurements with those of other experiments.

[1]  J. A. Hinton,et al.  The STACEE-32 ground based gamma-ray detector , 2002 .

[2]  Martin J. Rees,et al.  Comptonization of Diffuse Ambient Radiation by a Relativistic Jet: The Source of Gamma Rays from Blazars? , 1994 .

[3]  P. J. Boyle,et al.  Extremely rapid bursts of TeV photons from the active galaxy Markarian 421 , 1996, Nature.

[4]  D. Bhattacharya,et al.  High-Energy Gamma-Ray Observations of the Crab Nebula and Pulsar with the Solar Tower Atmospheric Cerenkov Effect Experiment , 2000, astro-ph/0006304.

[5]  Paolo S. Coppi,et al.  Time-dependent models of magnetized pair plasmas , 1992 .

[6]  Felix A. Aharonian,et al.  Simultaneous X-Ray and Gamma-Ray Observations of TEV Blazars: Testing Synchro-Compton Emission Models and Probing the Infrared Extragalactic Background , 1998 .

[7]  R. J. Protheroe,et al.  A proton synchrotron blazar model for flaring in Markarian 501 , 2001 .

[8]  R Edelson,et al.  The Discrete Correlation Function: a New Method for Analyzing Unevenly Sampled Variability Data , 1988 .

[9]  Felix Aharonian,et al.  Astronomy: The cosmic accelerator , 2002, Nature.

[10]  H. Krawczynski,et al.  Complex Spectral Variability from Intensive Multiwavelength Monitoring of Markarian 421 in 1998 , 2000, astro-ph/0008505.

[11]  Trevor C. Weekes,et al.  Very High Energy Gamma-Ray Astronomy , 1999 .

[12]  F. A. Aharonian.  TeV gamma rays from BL Lac Objects due to synchrotron radiation of extremely high energy protons , 2000 .

[13]  M. Punch,et al.  Detection of TeV photons from the active galaxy Markarian 421 , 1992, Nature.

[14]  P. Espigat,et al.  Measurement of the Crab Flux above 60 GeV with the CELESTE Cerenkov Telescope , 2002 .