Study of Markarian 421 in the γ-ray energy range 30-100 Tev

P. L. Ghia; M. Aglietta; B. Allessandro; P. Antonioli; F. Arneodo; L. Bergamasco; M. Bertaina; C. Castagnoli; A. Castellina; A. Chiavassa; G. Cini Castagnoli; B. D'Ettorre Piazzoli; G. Di Sciascio; W. Fulgione; P. Galeotti; P. L. Ghia; M. Iacovacci; G. Mannocchi; C. Morello; G. Navarra; O. Saavedra; G. C. Trinchero; P. Vallania; S. Vernetto; C. Vigorito

doi:10.1016/S0920-5632(98)00484-8

Study of Markarian 421 in the γ-ray energy range 30-100 Tev

P. L. Ghia, M. Aglietta, B. Allessandro, P. Antonioli, F. Arneodo, L. Bergamasco, M. Bertaina, C. Castagnoli, A. Castellina, A. Chiavassa, G. Cini Castagnoli, B. D'Ettorre Piazzoli, G. Di Sciascio, W. Fulgione, P. Galeotti, P. L. Ghia, M. Iacovacci, G. Mannocchi, C. Morello, G. NavarraO. Saavedra, G. C. Trinchero, P. Vallania, S. Vernetto, C. Vigorito

Physics

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Abstract

The active galactic nucleus Markarian 421 (Mrk 421) is studied through the EAS-TOP extensive air shower array in the γ-ray energy ranges 20-50 TeV and 80-120 TeV. No evidence of d.c. emission is found in both datasets: the 90% flux limits are Φ(>25 TeV) < 1.3 · 10^-13 cm^-2 s^-1 and Φ(>90 TeV) < 2.5 · 10^-4 cm^-2 s^-1. A straight power law extrapolation up to E₀ ≈ 10¹⁵ eV of the spectrum obtained from the observations by the EGRET and Whipple experiments - above 100 MeV and 0.5 TeV respectively - is excluded with a confidence level >99.99%, as expected from the absorption of VHE γ-rays by the 2.7K cosmic microwave background radiation. An indication (at ≈ 90% c.l.) of a steepening of the spectrum, with respect to such extrapolation, at γ-ray energies lower than expected from the 2.7K cutoff is derived. This could be due either to a break in the source spectrum or to the absorption of VHE γ-rays by intergalactic infrared photons of wavelength ≈ 100 μm.

Original language	English (US)
Pages (from-to)	506-508
Number of pages	3
Journal	Nuclear Physics B - Proceedings Supplements
Volume	70
Issue number	1-3
DOIs	https://doi.org/10.1016/S0920-5632(98)00484-8
State	Published - Jan 1999

ASJC Scopus subject areas

Atomic and Molecular Physics, and Optics
Nuclear and High Energy Physics

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10.1016/S0920-5632(98)00484-8

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Ghia, P. L., Aglietta, M., Allessandro, B., Antonioli, P., Arneodo, F., Bergamasco, L., Bertaina, M., Castagnoli, C., Castellina, A., Chiavassa, A., Cini Castagnoli, G., D'Ettorre Piazzoli, B., Di Sciascio, G., Fulgione, W., Galeotti, P., Ghia, P. L., Iacovacci, M., Mannocchi, G., Morello, C., ... Vigorito, C. (1999). Study of Markarian 421 in the γ-ray energy range 30-100 Tev. Nuclear Physics B - Proceedings Supplements, 70(1-3), 506-508. https://doi.org/10.1016/S0920-5632(98)00484-8

Ghia, PL, Aglietta, M, Allessandro, B, Antonioli, P, Arneodo, F, Bergamasco, L, Bertaina, M, Castagnoli, C, Castellina, A, Chiavassa, A, Cini Castagnoli, G, D'Ettorre Piazzoli, B, Di Sciascio, G, Fulgione, W, Galeotti, P, Ghia, PL, Iacovacci, M, Mannocchi, G, Morello, C, Navarra, G, Saavedra, O, Trinchero, GC, Vallania, P, Vernetto, S & Vigorito, C 1999, 'Study of Markarian 421 in the γ-ray energy range 30-100 Tev', Nuclear Physics B - Proceedings Supplements, vol. 70, no. 1-3, pp. 506-508. https://doi.org/10.1016/S0920-5632(98)00484-8

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title = "Study of Markarian 421 in the γ-ray energy range 30-100 Tev",

abstract = "The active galactic nucleus Markarian 421 (Mrk 421) is studied through the EAS-TOP extensive air shower array in the γ-ray energy ranges 20-50 TeV and 80-120 TeV. No evidence of d.c. emission is found in both datasets: the 90% flux limits are Φ(>25 TeV) < 1.3 · 10-13 cm-2 s-1 and Φ(>90 TeV) < 2.5 · 10-4 cm-2 s-1. A straight power law extrapolation up to E0 ≈ 1015 eV of the spectrum obtained from the observations by the EGRET and Whipple experiments - above 100 MeV and 0.5 TeV respectively - is excluded with a confidence level >99.99%, as expected from the absorption of VHE γ-rays by the 2.7K cosmic microwave background radiation. An indication (at ≈ 90% c.l.) of a steepening of the spectrum, with respect to such extrapolation, at γ-ray energies lower than expected from the 2.7K cutoff is derived. This could be due either to a break in the source spectrum or to the absorption of VHE γ-rays by intergalactic infrared photons of wavelength ≈ 100 μm.",

author = "Ghia, {P. L.} and M. Aglietta and B. Allessandro and P. Antonioli and F. Arneodo and L. Bergamasco and M. Bertaina and C. Castagnoli and A. Castellina and A. Chiavassa and {Cini Castagnoli}, G. and {D'Ettorre Piazzoli}, B. and {Di Sciascio}, G. and W. Fulgione and P. Galeotti and Ghia, {P. L.} and M. Iacovacci and G. Mannocchi and C. Morello and G. Navarra and O. Saavedra and Trinchero, {G. C.} and P. Vallania and S. Vernetto and C. Vigorito",

year = "1999",

month = jan,

doi = "10.1016/S0920-5632(98)00484-8",

language = "English (US)",

volume = "70",

pages = "506--508",

journal = "Nuclear Physics B - Proceedings Supplements",

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T1 - Study of Markarian 421 in the γ-ray energy range 30-100 Tev

AU - Ghia, P. L.

AU - Aglietta, M.

AU - Allessandro, B.

AU - Antonioli, P.

AU - Arneodo, F.

AU - Bergamasco, L.

AU - Bertaina, M.

AU - Castagnoli, C.

AU - Castellina, A.

AU - Chiavassa, A.

AU - Cini Castagnoli, G.

AU - D'Ettorre Piazzoli, B.

AU - Di Sciascio, G.

AU - Fulgione, W.

AU - Galeotti, P.

AU - Ghia, P. L.

AU - Iacovacci, M.

AU - Mannocchi, G.

AU - Morello, C.

AU - Navarra, G.

AU - Saavedra, O.

AU - Trinchero, G. C.

AU - Vallania, P.

AU - Vernetto, S.

AU - Vigorito, C.

PY - 1999/1

Y1 - 1999/1

N2 - The active galactic nucleus Markarian 421 (Mrk 421) is studied through the EAS-TOP extensive air shower array in the γ-ray energy ranges 20-50 TeV and 80-120 TeV. No evidence of d.c. emission is found in both datasets: the 90% flux limits are Φ(>25 TeV) < 1.3 · 10-13 cm-2 s-1 and Φ(>90 TeV) < 2.5 · 10-4 cm-2 s-1. A straight power law extrapolation up to E0 ≈ 1015 eV of the spectrum obtained from the observations by the EGRET and Whipple experiments - above 100 MeV and 0.5 TeV respectively - is excluded with a confidence level >99.99%, as expected from the absorption of VHE γ-rays by the 2.7K cosmic microwave background radiation. An indication (at ≈ 90% c.l.) of a steepening of the spectrum, with respect to such extrapolation, at γ-ray energies lower than expected from the 2.7K cutoff is derived. This could be due either to a break in the source spectrum or to the absorption of VHE γ-rays by intergalactic infrared photons of wavelength ≈ 100 μm.

AB - The active galactic nucleus Markarian 421 (Mrk 421) is studied through the EAS-TOP extensive air shower array in the γ-ray energy ranges 20-50 TeV and 80-120 TeV. No evidence of d.c. emission is found in both datasets: the 90% flux limits are Φ(>25 TeV) < 1.3 · 10-13 cm-2 s-1 and Φ(>90 TeV) < 2.5 · 10-4 cm-2 s-1. A straight power law extrapolation up to E0 ≈ 1015 eV of the spectrum obtained from the observations by the EGRET and Whipple experiments - above 100 MeV and 0.5 TeV respectively - is excluded with a confidence level >99.99%, as expected from the absorption of VHE γ-rays by the 2.7K cosmic microwave background radiation. An indication (at ≈ 90% c.l.) of a steepening of the spectrum, with respect to such extrapolation, at γ-ray energies lower than expected from the 2.7K cutoff is derived. This could be due either to a break in the source spectrum or to the absorption of VHE γ-rays by intergalactic infrared photons of wavelength ≈ 100 μm.

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JO - Nuclear Physics B - Proceedings Supplements

JF - Nuclear Physics B - Proceedings Supplements

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ER -

Study of Markarian 421 in the γ-ray energy range 30-100 Tev

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