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; J. Kataoka; A. Kawachi; T. Kifune; H. Kubo; J. Kushida; S. Maeda; A. Maeshiro; 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

doi:10.1086/344831

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, J. Kataoka, A. Kawachi, T. Kifune, H. Kubo, J. Kushida, S. Maeda, A. MaeshiroY. 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

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

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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 ± 0.9_stat ± 0.3_syst) × 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 language	English
Pages (from-to)	L9-L12
Journal	Astrophysical Journal
Volume	579
Issue number	1 II
DOIs	https://doi.org/10.1086/344831
Publication status	Published - 1 Nov 2002

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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, J., Kawachi, A., Kifune, T., Kubo, H., Kushida, J., Maeda, S., ... Yoshikoshi, T. (2002). Observation of gamma rays greater than 10 TeV from Markarian 421. Astrophysical Journal, 579(1 II), L9-L12. https://doi.org/10.1086/344831

@article{7d773a54e72f487f8c0c229892472483,

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.",

keywords = "BL Lacertae objects: individual (Markarian 421), Gamma rays: observations",

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

year = "2002",

month = nov,

day = "1",

doi = "10.1086/344831",

language = "English",

volume = "579",

pages = "L9--L12",

journal = "Astrophysical Journal",

issn = "0004-637X",

publisher = "American Astronomical Society",

number = "1 II",

}

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, pp. L9-L12. https://doi.org/10.1086/344831

TY - JOUR

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, J.

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.

AB - 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.

KW - BL Lacertae objects: individual (Markarian 421)

KW - Gamma rays: observations

UR - http://www.scopus.com/inward/record.url?scp=18244411395&partnerID=8YFLogxK

U2 - 10.1086/344831

DO - 10.1086/344831

M3 - Article

SN - 0004-637X

VL - 579

SP - L9-L12

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 1 II

ER -

Observation of gamma rays greater than 10 TeV from Markarian 421

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