Observation of gamma rays greater than 10 TeV from Markarian 421

K. Okumura, A. Asahara, G. V. Bicknell, P. G. Edwards, R. Enomoto, S. Gunji, S. Hara, T. Hara, S. Hayashi, C. Itoh, S. Kabuki, F. Kajino, H. Katagiri, Jun Kataoka, A. Kawachi, T. Kifune, H. Kubo, J. Kushida, S. Maeda, A. Maeshiro & 25 others Y. Matsubara, Y. Mizumoto, M. Mori, M. Moriya, H. Muraishi, Y. Muraki, T. Naito, T. Nakase, K. Nishijima, M. Ohishi, J. R. Patterson, K. Sakurazawa, R. Suzuki, D. L. Swaby, K. Takano, T. Takano, T. Tanimori, F. Tokanai, K. Tsuchiya, H. Tsunoo, K. Uruma, A. Watanabe, S. Yanagita, T. Yoshida, T. Yoshikoshi

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

We have observed Markarian 421 in 2001 January and March with the CANGAROO-II imaging Cerenkov telescope during an extraordinarily high state at TeV energies. From 14 hr of observations at very large zenith angles, ∼70°, a signal of 298 ± 52 gamma-ray-like events (5.7 σ) 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 ± 0.9stat ± 0.3syst) × 10-13(E/10 TeV) -(4.0-0.6+0.9, stat±0.3syst) photons cm-2 s -1 TeV-1, which is steeper than those previously measured around 1 TeV and supports the evidence for a cutoff in the spectrum of Mrk 421. However, the 4 σ excess at energies greater than 20 TeV in our data favors a cutoff energy of ∼8 TeV, at the upper end of the range previously reported from measurements at TeV energies.

Original languageEnglish
JournalAstrophysical Journal
Volume579
Issue number1 II
DOIs
Publication statusPublished - 2002 Nov 1
Externally publishedYes

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gamma rays
zenith
energy
cut-off
zenith angle
energy spectra
telescopes
power law
sensitivity
photons

Keywords

  • BL Lacertae objects: individual (Markarian 421)
  • Gamma rays: observations

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Okumura, K., Asahara, A., Bicknell, G. V., Edwards, P. G., Enomoto, R., Gunji, S., ... Yoshikoshi, T. (2002). Observation of gamma rays greater than 10 TeV from Markarian 421. Astrophysical Journal, 579(1 II). https://doi.org/10.1086/344831

Observation of gamma rays greater than 10 TeV from Markarian 421. / Okumura, K.; Asahara, A.; Bicknell, G. V.; Edwards, P. G.; Enomoto, R.; Gunji, S.; Hara, S.; Hara, T.; Hayashi, S.; Itoh, C.; Kabuki, S.; Kajino, F.; Katagiri, H.; Kataoka, Jun; Kawachi, A.; Kifune, T.; Kubo, H.; Kushida, J.; Maeda, S.; Maeshiro, A.; Matsubara, Y.; Mizumoto, Y.; Mori, M.; Moriya, M.; Muraishi, H.; Muraki, Y.; Naito, T.; Nakase, T.; Nishijima, K.; Ohishi, M.; Patterson, J. R.; Sakurazawa, K.; Suzuki, R.; Swaby, D. L.; Takano, K.; Takano, T.; Tanimori, T.; Tokanai, F.; Tsuchiya, K.; Tsunoo, H.; Uruma, K.; Watanabe, A.; Yanagita, S.; Yoshida, T.; Yoshikoshi, T.

In: Astrophysical Journal, Vol. 579, No. 1 II, 01.11.2002.

Research output: Contribution to journalArticle

Okumura, K, Asahara, A, Bicknell, GV, Edwards, PG, Enomoto, R, Gunji, S, Hara, S, Hara, T, Hayashi, S, Itoh, C, Kabuki, S, Kajino, F, Katagiri, H, Kataoka, J, Kawachi, A, Kifune, T, Kubo, H, Kushida, J, Maeda, S, Maeshiro, A, Matsubara, Y, Mizumoto, Y, Mori, M, Moriya, M, Muraishi, H, Muraki, Y, Naito, T, Nakase, T, Nishijima, K, Ohishi, M, Patterson, JR, Sakurazawa, K, Suzuki, R, Swaby, DL, Takano, K, Takano, T, Tanimori, T, Tokanai, F, Tsuchiya, K, Tsunoo, H, Uruma, K, Watanabe, A, Yanagita, S, Yoshida, T & Yoshikoshi, T 2002, 'Observation of gamma rays greater than 10 TeV from Markarian 421', Astrophysical Journal, vol. 579, no. 1 II. https://doi.org/10.1086/344831
Okumura K, Asahara A, Bicknell GV, Edwards PG, Enomoto R, Gunji S et al. Observation of gamma rays greater than 10 TeV from Markarian 421. Astrophysical Journal. 2002 Nov 1;579(1 II). https://doi.org/10.1086/344831
Okumura, K. ; Asahara, A. ; Bicknell, G. V. ; Edwards, P. G. ; Enomoto, R. ; Gunji, S. ; Hara, S. ; Hara, T. ; Hayashi, S. ; Itoh, C. ; Kabuki, S. ; Kajino, F. ; Katagiri, H. ; Kataoka, Jun ; Kawachi, A. ; Kifune, T. ; Kubo, H. ; Kushida, J. ; Maeda, S. ; Maeshiro, A. ; Matsubara, Y. ; Mizumoto, Y. ; Mori, M. ; Moriya, M. ; Muraishi, H. ; Muraki, Y. ; Naito, T. ; Nakase, T. ; Nishijima, K. ; Ohishi, M. ; Patterson, J. R. ; Sakurazawa, K. ; Suzuki, R. ; Swaby, D. L. ; Takano, K. ; Takano, T. ; Tanimori, T. ; Tokanai, F. ; Tsuchiya, K. ; Tsunoo, H. ; Uruma, K. ; Watanabe, A. ; Yanagita, S. ; Yoshida, T. ; Yoshikoshi, T. / Observation of gamma rays greater than 10 TeV from Markarian 421. In: Astrophysical Journal. 2002 ; Vol. 579, No. 1 II.
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title = "Observation of gamma rays greater than 10 TeV from Markarian 421",
abstract = "We have observed Markarian 421 in 2001 January and March with the CANGAROO-II imaging Cerenkov telescope during an extraordinarily high state at TeV energies. From 14 hr of observations at very large zenith angles, ∼70°, a signal of 298 ± 52 gamma-ray-like events (5.7 σ) 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 ± 0.9stat ± 0.3syst) × 10-13(E/10 TeV) -(4.0-0.6+0.9, stat±0.3syst) photons cm-2 s -1 TeV-1, which is steeper than those previously measured around 1 TeV and supports the evidence for a cutoff in the spectrum of Mrk 421. However, the 4 σ excess at energies greater than 20 TeV in our data favors a cutoff energy of ∼8 TeV, at the upper end of the range previously reported from measurements at TeV energies.",
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T1 - Observation of gamma rays greater than 10 TeV from Markarian 421

AU - Okumura, K.

AU - Asahara, A.

AU - Bicknell, G. V.

AU - Edwards, P. G.

AU - Enomoto, R.

AU - Gunji, S.

AU - Hara, S.

AU - Hara, T.

AU - Hayashi, S.

AU - Itoh, C.

AU - Kabuki, S.

AU - Kajino, F.

AU - Katagiri, H.

AU - Kataoka, Jun

AU - Kawachi, A.

AU - Kifune, T.

AU - Kubo, H.

AU - Kushida, J.

AU - Maeda, S.

AU - Maeshiro, A.

AU - Matsubara, Y.

AU - Mizumoto, Y.

AU - Mori, M.

AU - Moriya, M.

AU - Muraishi, H.

AU - Muraki, Y.

AU - Naito, T.

AU - Nakase, T.

AU - Nishijima, K.

AU - Ohishi, M.

AU - Patterson, J. R.

AU - Sakurazawa, K.

AU - Suzuki, R.

AU - Swaby, D. L.

AU - Takano, K.

AU - Takano, T.

AU - Tanimori, T.

AU - Tokanai, F.

AU - Tsuchiya, K.

AU - Tsunoo, H.

AU - Uruma, K.

AU - Watanabe, A.

AU - Yanagita, S.

AU - Yoshida, T.

AU - Yoshikoshi, T.

PY - 2002/11/1

Y1 - 2002/11/1

N2 - We have observed Markarian 421 in 2001 January and March with the CANGAROO-II imaging Cerenkov telescope during an extraordinarily high state at TeV energies. From 14 hr of observations at very large zenith angles, ∼70°, a signal of 298 ± 52 gamma-ray-like events (5.7 σ) 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 ± 0.9stat ± 0.3syst) × 10-13(E/10 TeV) -(4.0-0.6+0.9, stat±0.3syst) photons cm-2 s -1 TeV-1, which is steeper than those previously measured around 1 TeV and supports the evidence for a cutoff in the spectrum of Mrk 421. However, the 4 σ excess at energies greater than 20 TeV in our data favors a cutoff energy of ∼8 TeV, at the upper end of the range previously reported from measurements at TeV energies.

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KW - BL Lacertae objects: individual (Markarian 421)

KW - Gamma rays: observations

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