Astronomy and Astrophysics – Astrophysics
Scientific paper
2002-09-24
Astrophys.J. 579 (2002) L9-L12
Astronomy and Astrophysics
Astrophysics
13 pages, 4 figures, to appear in Astrophisical Journal Letters
Scientific paper
10.1086/344831
We have observed Markarian 421 in January and March 2001 with the CANGAROO-II imaging Cherenkov telescope during an extraordinarily high state at TeV energies. From 14 hours observations at very large zenith angles, $\sim70^\circ$, a signal of 298 $\pm$ 52 gamma-ray--like events (5.7 $\sigma$) was detected at $E>10$ TeV, where a higher sensitivity is achieved than those of usual observations near the zenith, owing to a greatly increased collecting area. Under the assumption of an intrinsic power-law spectrum, we derived a differential energy spectrum $dN/dE = (3.3 \pm 0.9_{stat.} \pm 0.3_{syst.})\times10^{-13} (E/10 {Te V})^{-(4.0 ^{+0.9}_{-0.6}_{stat.} \pm 0.3_{syst.})}$ ph./cm$^2$/sec/TeV, which is steeper than those previously measured around 1 TeV, and supports the evidence for a cutoff in the spectrum of Markarian 421. However, the 4 $\sigma$ excess at energies greater than 20 TeV in our data favors a cutoff energy of $\sim$8 TeV, at the upper end of the range previously reported from measurements at TeV energies.
Asahara Akihiro
Bicknell Geoffrey V.
Edwards Philip G.
Enomoto Ryoji
Gunji Shuichi
No associations
LandOfFree
Observation of gamma-rays greater than 10 TeV from Markarian 421 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Observation of gamma-rays greater than 10 TeV from Markarian 421, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Observation of gamma-rays greater than 10 TeV from Markarian 421 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-611945