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

P. L. Ghia, M. Aglietta, B. Allessandro, P. Antonioli, Francesco 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

Research output: Contribution to journalArticle

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 languageEnglish (US)
Pages (from-to)506-508
Number of pages3
JournalNuclear Physics B - Proceedings Supplements
Volume70
Issue number1-3
DOIs
StatePublished - Jan 1 1999

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rays
cosmic microwave background radiation
energy
cosmic ray showers
active galactic nuclei
extrapolation
indication
cut-off
photons
wavelengths

ASJC Scopus subject areas

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

Cite this

Ghia, P. L., Aglietta, M., Allessandro, B., Antonioli, P., Arneodo, F., Bergamasco, L., ... 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

Study of Markarian 421 in the γ-ray energy range 30-100 Tev. / Ghia, P. L.; Aglietta, M.; Allessandro, B.; Antonioli, P.; Arneodo, Francesco; 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.; Navarra, G.; Saavedra, O.; Trinchero, G. C.; Vallania, P.; Vernetto, S.; Vigorito, C.

In: Nuclear Physics B - Proceedings Supplements, Vol. 70, No. 1-3, 01.01.1999, p. 506-508.

Research output: Contribution to journalArticle

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
Ghia, P. L. ; Aglietta, M. ; Allessandro, B. ; Antonioli, P. ; Arneodo, Francesco ; 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. ; Navarra, G. ; Saavedra, O. ; Trinchero, G. C. ; Vallania, P. ; Vernetto, S. ; Vigorito, C. / Study of Markarian 421 in the γ-ray energy range 30-100 Tev. In: Nuclear Physics B - Proceedings Supplements. 1999 ; Vol. 70, No. 1-3. pp. 506-508.
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AU - Ghia, P. L.

AU - Aglietta, M.

AU - Allessandro, B.

AU - Antonioli, P.

AU - Arneodo, Francesco

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 - 1999/1/1

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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.

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