Detection of VHE γ-rays from Mkn 421 with the HEGRA Cherenkov telescopes

D. Petry; S. M. Bradbury; A. Konopelko; J. Fernandez; F. Aharonian; A. G. Akhperjanian; A. S. Belgarian; J. J.G. Beteta; J. L. Contreras; J. Cortina; A. Daum; T. Deckers; E. Feigl; V. Fonseca; B. Funk; J. C. Gonzalez; V. Haustein; G. Heinzelmann; G. Hermann; M. Hess; A. Heusler; W. Hofmann; R. Kankanian; O. Kirstein; C. Köhler; H. Krawczynski; H. Kornmayer; A. Lindner; E. Lorenz; N. Magnussen; H. Meyer; R. Mirzoyan; H. Möller; A. Moralejo; N. Müller; L. Padilla; M. Panter; R. Plaga; J. Prahl; C. Prosch; G. Rauterberg; W. Rhode; V. Sahakian; M. Samorski; J. A. Sanchez; D. Schmele; W. Stamm; M. Ulrich; H. J. Völk; S. Westerhoff; B. Wiebel-Sooth; C. A. Wiedner; M. Willmer; H. Wirth

Detection of VHE γ-rays from Mkn 421 with the HEGRA Cherenkov telescopes

D. Petry, S. M. Bradbury, A. Konopelko, J. Fernandez, F. Aharonian, A. G. Akhperjanian, A. S. Belgarian, J. J.G. Beteta, J. L. Contreras, J. Cortina, A. Daum, T. Deckers, E. Feigl, V. Fonseca, B. Funk, J. C. Gonzalez, V. Haustein, G. Heinzelmann, G. Hermann, M. HessA. Heusler, W. Hofmann, R. Kankanian, O. Kirstein, C. Köhler, H. Krawczynski, H. Kornmayer, A. Lindner, E. Lorenz, N. Magnussen, H. Meyer, R. Mirzoyan, H. Möller, A. Moralejo, N. Müller, L. Padilla, M. Panter, R. Plaga, J. Prahl, C. Prosch, G. Rauterberg, W. Rhode, V. Sahakian, M. Samorski, J. A. Sanchez, D. Schmele, W. Stamm, M. Ulrich, H. J. Völk, S. Westerhoff, B. Wiebel-Sooth, C. A. Wiedner, M. Willmer, H. Wirth

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Abstract

A detection of γ-rays from Mkn 421 at energies above 1 TeV is reported, based on observations made in December 1994 - May 1995 with the first two HEGRA Cherenkov telescopes. From the image analysis, 111 excess gamma candidates are obtained from the 26 h Telescope #1 (CT1) dataset (significance 4.0 σ) and 218 from the 41 h Telescope #2 (CT2) dataset (significance 4.2 σ) at zenith angles θ < 25°. The combined significance is approx. 5.8 σ. This is the second detection of Mkn 421 at TeV energies. The average excess rate is 4.3 ± 1.0 h^-1 for CT1 and 5.4±1.3 h^-1 for CT2. Comparison with our contemporary observations of the Crab Nebula indicates that Mkn 421 has a steeper spectrum than the Crab Nebula above 1 TeV. Under the assumption that the spectrum of Mkn 421 follows a power law, we obtain a differential spectral index of 3.6±1.0 and an integral flux above 1 TeV of 8(±2)_Stat(+6-3)_Syst × 10^-12 cm^-2s^-1 from a comparison with Monte Carlo data. This flux is smaller than the Crab Nebula flux by a factor of 2.0±0.8.

Original language	English
Pages (from-to)	L13-L16
Journal	Astronomy and Astrophysics
Volume	311
Issue number	3
State	Published - Jul 20 1996

Keywords

BL Lacertae objects: individual: Mkn 421
Gamma rays: observations

Cite this

Petry, D., Bradbury, S. M., Konopelko, A., Fernandez, J., Aharonian, F., Akhperjanian, A. G., Belgarian, A. S., Beteta, J. J. G., Contreras, J. L., Cortina, J., Daum, A., Deckers, T., Feigl, E., Fonseca, V., Funk, B., Gonzalez, J. C., Haustein, V., Heinzelmann, G., Hermann, G., ... Wirth, H. (1996). Detection of VHE γ-rays from Mkn 421 with the HEGRA Cherenkov telescopes. Astronomy and Astrophysics, 311(3), L13-L16.

@article{61d3c43c249342eca037d91063933e92,

title = "Detection of VHE γ-rays from Mkn 421 with the HEGRA Cherenkov telescopes",

abstract = "A detection of γ-rays from Mkn 421 at energies above 1 TeV is reported, based on observations made in December 1994 - May 1995 with the first two HEGRA Cherenkov telescopes. From the image analysis, 111 excess gamma candidates are obtained from the 26 h Telescope #1 (CT1) dataset (significance 4.0 σ) and 218 from the 41 h Telescope #2 (CT2) dataset (significance 4.2 σ) at zenith angles θ < 25°. The combined significance is approx. 5.8 σ. This is the second detection of Mkn 421 at TeV energies. The average excess rate is 4.3 ± 1.0 h-1 for CT1 and 5.4±1.3 h-1 for CT2. Comparison with our contemporary observations of the Crab Nebula indicates that Mkn 421 has a steeper spectrum than the Crab Nebula above 1 TeV. Under the assumption that the spectrum of Mkn 421 follows a power law, we obtain a differential spectral index of 3.6±1.0 and an integral flux above 1 TeV of 8(±2)Stat(+6-3)Syst × 10-12 cm-2s-1 from a comparison with Monte Carlo data. This flux is smaller than the Crab Nebula flux by a factor of 2.0±0.8.",

keywords = "BL Lacertae objects: individual: Mkn 421, Gamma rays: observations",

author = "D. Petry and Bradbury, {S. M.} and A. Konopelko and J. Fernandez and F. Aharonian and Akhperjanian, {A. G.} and Belgarian, {A. S.} and Beteta, {J. J.G.} and Contreras, {J. L.} and J. Cortina and A. Daum and T. Deckers and E. Feigl and V. Fonseca and B. Funk and Gonzalez, {J. C.} and V. Haustein and G. Heinzelmann and G. Hermann and M. Hess and A. Heusler and W. Hofmann and R. Kankanian and O. Kirstein and C. K{\"o}hler and H. Krawczynski and H. Kornmayer and A. Lindner and E. Lorenz and N. Magnussen and H. Meyer and R. Mirzoyan and H. M{\"o}ller and A. Moralejo and N. M{\"u}ller and L. Padilla and M. Panter and R. Plaga and J. Prahl and C. Prosch and G. Rauterberg and W. Rhode and V. Sahakian and M. Samorski and Sanchez, {J. A.} and D. Schmele and W. Stamm and M. Ulrich and V{\"o}lk, {H. J.} and S. Westerhoff and B. Wiebel-Sooth and Wiedner, {C. A.} and M. Willmer and H. Wirth",

year = "1996",

month = jul,

day = "20",

language = "English",

volume = "311",

pages = "L13--L16",

journal = "Astronomy and Astrophysics",

issn = "0004-6361",

number = "3",

}

Petry, D, Bradbury, SM, Konopelko, A, Fernandez, J, Aharonian, F, Akhperjanian, AG, Belgarian, AS, Beteta, JJG, Contreras, JL, Cortina, J, Daum, A, Deckers, T, Feigl, E, Fonseca, V, Funk, B, Gonzalez, JC, Haustein, V, Heinzelmann, G, Hermann, G, Hess, M, Heusler, A, Hofmann, W, Kankanian, R, Kirstein, O, Köhler, C, Krawczynski, H, Kornmayer, H, Lindner, A, Lorenz, E, Magnussen, N, Meyer, H, Mirzoyan, R, Möller, H, Moralejo, A, Müller, N, Padilla, L, Panter, M, Plaga, R, Prahl, J, Prosch, C, Rauterberg, G, Rhode, W, Sahakian, V, Samorski, M, Sanchez, JA, Schmele, D, Stamm, W, Ulrich, M, Völk, HJ, Westerhoff, S, Wiebel-Sooth, B, Wiedner, CA, Willmer, M & Wirth, H 1996, 'Detection of VHE γ-rays from Mkn 421 with the HEGRA Cherenkov telescopes', Astronomy and Astrophysics, vol. 311, no. 3, pp. L13-L16.

TY - JOUR

T1 - Detection of VHE γ-rays from Mkn 421 with the HEGRA Cherenkov telescopes

AU - Petry, D.

AU - Bradbury, S. M.

AU - Konopelko, A.

AU - Fernandez, J.

AU - Aharonian, F.

AU - Akhperjanian, A. G.

AU - Belgarian, A. S.

AU - Beteta, J. J.G.

AU - Contreras, J. L.

AU - Cortina, J.

AU - Daum, A.

AU - Deckers, T.

AU - Feigl, E.

AU - Fonseca, V.

AU - Funk, B.

AU - Gonzalez, J. C.

AU - Haustein, V.

AU - Heinzelmann, G.

AU - Hermann, G.

AU - Hess, M.

AU - Heusler, A.

AU - Hofmann, W.

AU - Kankanian, R.

AU - Kirstein, O.

AU - Köhler, C.

AU - Krawczynski, H.

AU - Kornmayer, H.

AU - Lindner, A.

AU - Lorenz, E.

AU - Magnussen, N.

AU - Meyer, H.

AU - Mirzoyan, R.

AU - Möller, H.

AU - Moralejo, A.

AU - Müller, N.

AU - Padilla, L.

AU - Panter, M.

AU - Plaga, R.

AU - Prahl, J.

AU - Prosch, C.

AU - Rauterberg, G.

AU - Rhode, W.

AU - Sahakian, V.

AU - Samorski, M.

AU - Sanchez, J. A.

AU - Schmele, D.

AU - Stamm, W.

AU - Ulrich, M.

AU - Völk, H. J.

AU - Westerhoff, S.

AU - Wiebel-Sooth, B.

AU - Wiedner, C. A.

AU - Willmer, M.

AU - Wirth, H.

PY - 1996/7/20

Y1 - 1996/7/20

N2 - A detection of γ-rays from Mkn 421 at energies above 1 TeV is reported, based on observations made in December 1994 - May 1995 with the first two HEGRA Cherenkov telescopes. From the image analysis, 111 excess gamma candidates are obtained from the 26 h Telescope #1 (CT1) dataset (significance 4.0 σ) and 218 from the 41 h Telescope #2 (CT2) dataset (significance 4.2 σ) at zenith angles θ < 25°. The combined significance is approx. 5.8 σ. This is the second detection of Mkn 421 at TeV energies. The average excess rate is 4.3 ± 1.0 h-1 for CT1 and 5.4±1.3 h-1 for CT2. Comparison with our contemporary observations of the Crab Nebula indicates that Mkn 421 has a steeper spectrum than the Crab Nebula above 1 TeV. Under the assumption that the spectrum of Mkn 421 follows a power law, we obtain a differential spectral index of 3.6±1.0 and an integral flux above 1 TeV of 8(±2)Stat(+6-3)Syst × 10-12 cm-2s-1 from a comparison with Monte Carlo data. This flux is smaller than the Crab Nebula flux by a factor of 2.0±0.8.

AB - A detection of γ-rays from Mkn 421 at energies above 1 TeV is reported, based on observations made in December 1994 - May 1995 with the first two HEGRA Cherenkov telescopes. From the image analysis, 111 excess gamma candidates are obtained from the 26 h Telescope #1 (CT1) dataset (significance 4.0 σ) and 218 from the 41 h Telescope #2 (CT2) dataset (significance 4.2 σ) at zenith angles θ < 25°. The combined significance is approx. 5.8 σ. This is the second detection of Mkn 421 at TeV energies. The average excess rate is 4.3 ± 1.0 h-1 for CT1 and 5.4±1.3 h-1 for CT2. Comparison with our contemporary observations of the Crab Nebula indicates that Mkn 421 has a steeper spectrum than the Crab Nebula above 1 TeV. Under the assumption that the spectrum of Mkn 421 follows a power law, we obtain a differential spectral index of 3.6±1.0 and an integral flux above 1 TeV of 8(±2)Stat(+6-3)Syst × 10-12 cm-2s-1 from a comparison with Monte Carlo data. This flux is smaller than the Crab Nebula flux by a factor of 2.0±0.8.

KW - BL Lacertae objects: individual: Mkn 421

KW - Gamma rays: observations

UR - http://www.scopus.com/inward/record.url?scp=0001902504&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0001902504

SN - 0004-6361

VL - 311

SP - L13-L16

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

IS - 3

ER -

Detection of VHE γ-rays from Mkn 421 with the HEGRA Cherenkov telescopes

Abstract

Keywords

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