Observations of Mkn 421 in 2004 with HESS at large zenith angles

F. Aharonian; A. G. Akhperjanian; K. M. Aye; A. R. Bazer-Bachi; M. Beilicke; W. Benbow; D. Berge; P. Berghaus; K. Bernlöhr; C. Boisson; O. Bolz; I. Braun; F. Breitling; A. M. Brown; J. Bussons Gordo; P. M. Chadwick; L. M. Chounet; R. Cornils; L. Costamante; B. Degrange; A. Djannati-Ataï; L. O.C. Drury; G. Dubus; D. Emmanoulopoulos; P. Espigat; F. Feinstein; P. Fleury; G. Fontaine; Y. Fuchs; S. Funk; Y. A. Gallant; B. Giebels; S. Gillessen; J. F. Glicenstein; P. Goret; C. Hadjichristidis; M. Hauser; G. Heinzelmann; G. Henri; G. Hermann; J. A. Hinton; W. Hofmann; M. Holleran; D. Horns; O. C. De Jager; B. Khélifi; Nu Komin; A. Konopelko; I. J. Latham; R. Le Gallou; A. Lemière; M. Lemoine; N. Leroy; T. Lohse; A. Marcowith; C. Masterson; T. J.L. McComb; M. De Naurois; S. J. Nolan; A. Noutsos; K. J. Orford; J. L. Osborne; M. Ouchrif; M. Panter; G. Pelletier; S. Pita; G. Pühlhofer; M. Punch; B. C. Raubenheimer; M. Raue; J. Raux; S. M. Rayner; I. Redondo; A. Reimer; O. Reimer; J. Ripken; L. Rob; L. Rolland; G. Rowell; V. Sahakian; L. Saugé; S. Schlenker; R. Schlickeiser; C. Schuster; U. Schwanke; M. Siewert; H. Sol; R. Steenkamp; C. Stegmann; J. P. Tavernet; R. Terrier; C. G. Théoret; M. Tluczykont; G. Vasileiadis; C. Venter; P. Vincent; H. J. Völk; S. J. Wagner

doi:10.1051/0004-6361:20053050

Observations of Mkn 421 in 2004 with HESS at large zenith angles

F. Aharonian
, A. G. Akhperjanian
, K. M. Aye
, A. R. Bazer-Bachi
, M. Beilicke
, W. Benbow
, D. Berge
, P. Berghaus
, K. Bernlöhr
, C. Boisson
, O. Bolz
, I. Braun
, F. Breitling
, A. M. Brown
, J. Bussons Gordo
, P. M. Chadwick
, L. M. Chounet
, R. Cornils
, L. Costamante
, B. Degrange

A. Djannati-Ataï, L. O.C. Drury, G. Dubus, D. Emmanoulopoulos, P. Espigat, F. Feinstein, P. Fleury, G. Fontaine, Y. Fuchs, S. Funk, Y. A. Gallant, B. Giebels, S. Gillessen, J. F. Glicenstein, P. Goret, C. Hadjichristidis, M. Hauser, G. Heinzelmann, G. Henri, G. Hermann, J. A. Hinton, W. Hofmann, M. Holleran, D. Horns, O. C. De Jager, B. Khélifi, Nu Komin, A. Konopelko, I. J. Latham, R. Le Gallou, A. Lemière, M. Lemoine, N. Leroy, T. Lohse, A. Marcowith, C. Masterson, T. J.L. McComb, M. De Naurois, S. J. Nolan, A. Noutsos, K. J. Orford, J. L. Osborne, M. Ouchrif, M. Panter, G. Pelletier, S. Pita, G. Pühlhofer, M. Punch, B. C. Raubenheimer, M. Raue, J. Raux, S. M. Rayner, I. Redondo, A. Reimer, O. Reimer, J. Ripken, L. Rob, L. Rolland, G. Rowell, V. Sahakian, L. Saugé, S. Schlenker, R. Schlickeiser, C. Schuster, U. Schwanke, M. Siewert, H. Sol, R. Steenkamp, C. Stegmann, J. P. Tavernet, R. Terrier, C. G. Théoret, M. Tluczykont, G. Vasileiadis, C. Venter, P. Vincent, H. J. Völk, S. J. Wagner

Max-Planck-Institut für Kernphysik
Yerevan Physics Institute
Durham University
Centre national de la recherche scientifique
Universität Hamburg
Université Paris-Sud
Université Libre de Bruxelles
Humboldt-Universität zu Berlin
Ip Paris
European Associated Laboratory for Gamma-Ray Astronomy
Dublin Institute for Advanced Studies
Landessternwarte Heidelberg
Université Paris-Diderot
North-West University
Universités Paris VI and VII
The University of Sheffield
Ruhr-University Bochum
Charles University
University of Namibia

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

Abstract

Mkn 421 was observed during a high flux state for nine nights in April and May 2004 with the fully operational High Energy Stereoscopic System (HESS) in Namibia. The observations were carried out at zenith angles of 60°-65°, which result in an average energy threshold of 1.5 TeV and a collection area reaching 2 km² at 10 TeV. Roughly 7000 photons from Mkn 421 were accumulated with an average gamma-ray rate of 8 photons/min. The overall significance of the detection exceeds 100 standard deviations. The light-curve of integrated fluxes above 2 TeV shows changes of the diurnal flux up to a factor of 4.3. For nights of high flux, intra-night variability is detected with a decay time of less than 1 h. The time averaged energy spectrum is curved and is well described by a power-law with a photon index Γ = 2.1 ± 0.1_stat ± 0.3_sys and an exponential cutoff at E_c = 3.1(+0.5 - 0.4)_stat ± 0.9_sys TeV and an average integral flux above 2 TeV of 3 Crab flux units. Significant variations of the spectral shape are detected with a spectral hardening as the flux increases. Contemporaneous multi-wavelength observations at lower energies (X-rays and gamma-rays above ≈300 GeV) indicate smaller relative variability amplitudes than seen above 2 TeV during high flux state observed in April 2004.

Original language	English
Pages (from-to)	95-99
Number of pages	5
Journal	Astronomy and Astrophysics
Volume	437
Issue number	1
DOIs	https://doi.org/10.1051/0004-6361:20053050
Publication status	Published - 1 Jul 2005
Externally published	Yes

Keywords

Galaxies: individual: Mkn 421

Access to Document

10.1051/0004-6361:20053050

Cite this

Aharonian, F., Akhperjanian, A. G., Aye, K. M., Bazer-Bachi, A. R., Beilicke, M., Benbow, W., Berge, D., Berghaus, P., Bernlöhr, K., Boisson, C., Bolz, O., Braun, I., Breitling, F., Brown, A. M., Bussons Gordo, J., Chadwick, P. M., Chounet, L. M., Cornils, R., Costamante, L., ... Wagner, S. J. (2005). Observations of Mkn 421 in 2004 with HESS at large zenith angles. Astronomy and Astrophysics, 437(1), 95-99. https://doi.org/10.1051/0004-6361:20053050

@article{39307dab4880483b924ff32bf1f3cf13,

title = "Observations of Mkn 421 in 2004 with HESS at large zenith angles",

abstract = "Mkn 421 was observed during a high flux state for nine nights in April and May 2004 with the fully operational High Energy Stereoscopic System (HESS) in Namibia. The observations were carried out at zenith angles of 60°-65°, which result in an average energy threshold of 1.5 TeV and a collection area reaching 2 km2 at 10 TeV. Roughly 7000 photons from Mkn 421 were accumulated with an average gamma-ray rate of 8 photons/min. The overall significance of the detection exceeds 100 standard deviations. The light-curve of integrated fluxes above 2 TeV shows changes of the diurnal flux up to a factor of 4.3. For nights of high flux, intra-night variability is detected with a decay time of less than 1 h. The time averaged energy spectrum is curved and is well described by a power-law with a photon index Γ = 2.1 ± 0.1stat ± 0.3sys and an exponential cutoff at Ec = 3.1(+0.5 - 0.4)stat ± 0.9sys TeV and an average integral flux above 2 TeV of 3 Crab flux units. Significant variations of the spectral shape are detected with a spectral hardening as the flux increases. Contemporaneous multi-wavelength observations at lower energies (X-rays and gamma-rays above ≈300 GeV) indicate smaller relative variability amplitudes than seen above 2 TeV during high flux state observed in April 2004.",

keywords = "Galaxies: individual: Mkn 421",

author = "F. Aharonian and Akhperjanian, \{A. G.\} and Aye, \{K. M.\} and Bazer-Bachi, \{A. R.\} and M. Beilicke and W. Benbow and D. Berge and P. Berghaus and K. Bernl{\"o}hr and C. Boisson and O. Bolz and I. Braun and F. Breitling and Brown, \{A. M.\} and \{Bussons Gordo\}, J. and Chadwick, \{P. M.\} and Chounet, \{L. M.\} and R. Cornils and L. Costamante and B. Degrange and A. Djannati-Ata{\"i} and Drury, \{L. O.C.\} and G. Dubus and D. Emmanoulopoulos and P. Espigat and F. Feinstein and P. Fleury and G. Fontaine and Y. Fuchs and S. Funk and Gallant, \{Y. A.\} and B. Giebels and S. Gillessen and Glicenstein, \{J. F.\} and P. Goret and C. Hadjichristidis and M. Hauser and G. Heinzelmann and G. Henri and G. Hermann and Hinton, \{J. A.\} and W. Hofmann and M. Holleran and D. Horns and \{De Jager\}, \{O. C.\} and B. Kh{\'e}lifi and Nu Komin and A. Konopelko and Latham, \{I. J.\} and \{Le Gallou\}, R. and A. Lemi{\`e}re and M. Lemoine and N. Leroy and T. Lohse and A. Marcowith and C. Masterson and McComb, \{T. J.L.\} and \{De Naurois\}, M. and Nolan, \{S. J.\} and A. Noutsos and Orford, \{K. J.\} and Osborne, \{J. L.\} and M. Ouchrif and M. Panter and G. Pelletier and S. Pita and G. P{\"u}hlhofer and M. Punch and Raubenheimer, \{B. C.\} and M. Raue and J. Raux and Rayner, \{S. M.\} and I. Redondo and A. Reimer and O. Reimer and J. Ripken and L. Rob and L. Rolland and G. Rowell and V. Sahakian and L. Saug{\'e} and S. Schlenker and R. Schlickeiser and C. Schuster and U. Schwanke and M. Siewert and H. Sol and R. Steenkamp and C. Stegmann and Tavernet, \{J. P.\} and R. Terrier and Th{\'e}oret, \{C. G.\} and M. Tluczykont and G. Vasileiadis and C. Venter and P. Vincent and V{\"o}lk, \{H. J.\} and Wagner, \{S. J.\}",

year = "2005",

month = jul,

day = "1",

doi = "10.1051/0004-6361:20053050",

language = "English",

volume = "437",

pages = "95--99",

journal = "Astronomy and Astrophysics",

issn = "0004-6361",

number = "1",

}

Aharonian, F, Akhperjanian, AG, Aye, KM, Bazer-Bachi, AR, Beilicke, M, Benbow, W, Berge, D, Berghaus, P, Bernlöhr, K, Boisson, C, Bolz, O, Braun, I, Breitling, F, Brown, AM, Bussons Gordo, J, Chadwick, PM, Chounet, LM, Cornils, R, Costamante, L, Degrange, B, Djannati-Ataï, A, Drury, LOC, Dubus, G, Emmanoulopoulos, D, Espigat, P, Feinstein, F, Fleury, P, Fontaine, G, Fuchs, Y, Funk, S, Gallant, YA, Giebels, B, Gillessen, S, Glicenstein, JF, Goret, P, Hadjichristidis, C, Hauser, M, Heinzelmann, G, Henri, G, Hermann, G, Hinton, JA, Hofmann, W, Holleran, M, Horns, D, De Jager, OC, Khélifi, B, Komin, N, Konopelko, A, Latham, IJ, Le Gallou, R, Lemière, A, Lemoine, M, Leroy, N, Lohse, T, Marcowith, A, Masterson, C, McComb, TJL, De Naurois, M, Nolan, SJ, Noutsos, A, Orford, KJ, Osborne, JL, Ouchrif, M, Panter, M, Pelletier, G, Pita, S, Pühlhofer, G, Punch, M, Raubenheimer, BC, Raue, M, Raux, J, Rayner, SM, Redondo, I, Reimer, A, Reimer, O, Ripken, J, Rob, L, Rolland, L, Rowell, G, Sahakian, V, Saugé, L, Schlenker, S, Schlickeiser, R, Schuster, C, Schwanke, U, Siewert, M, Sol, H, Steenkamp, R, Stegmann, C, Tavernet, JP, Terrier, R, Théoret, CG, Tluczykont, M, Vasileiadis, G, Venter, C, Vincent, P, Völk, HJ & Wagner, SJ 2005, 'Observations of Mkn 421 in 2004 with HESS at large zenith angles', Astronomy and Astrophysics, vol. 437, no. 1, pp. 95-99. https://doi.org/10.1051/0004-6361:20053050

TY - JOUR

T1 - Observations of Mkn 421 in 2004 with HESS at large zenith angles

AU - Aharonian, F.

AU - Akhperjanian, A. G.

AU - Aye, K. M.

AU - Bazer-Bachi, A. R.

AU - Beilicke, M.

AU - Benbow, W.

AU - Berge, D.

AU - Berghaus, P.

AU - Bernlöhr, K.

AU - Boisson, C.

AU - Bolz, O.

AU - Braun, I.

AU - Breitling, F.

AU - Brown, A. M.

AU - Bussons Gordo, J.

AU - Chadwick, P. M.

AU - Chounet, L. M.

AU - Cornils, R.

AU - Costamante, L.

AU - Degrange, B.

AU - Djannati-Ataï, A.

AU - Drury, L. O.C.

AU - Dubus, G.

AU - Emmanoulopoulos, D.

AU - Espigat, P.

AU - Feinstein, F.

AU - Fleury, P.

AU - Fontaine, G.

AU - Fuchs, Y.

AU - Funk, S.

AU - Gallant, Y. A.

AU - Giebels, B.

AU - Gillessen, S.

AU - Glicenstein, J. F.

AU - Goret, P.

AU - Hadjichristidis, C.

AU - Hauser, M.

AU - Heinzelmann, G.

AU - Henri, G.

AU - Hermann, G.

AU - Hinton, J. A.

AU - Hofmann, W.

AU - Holleran, M.

AU - Horns, D.

AU - De Jager, O. C.

AU - Khélifi, B.

AU - Komin, Nu

AU - Konopelko, A.

AU - Latham, I. J.

AU - Le Gallou, R.

AU - Lemière, A.

AU - Lemoine, M.

AU - Leroy, N.

AU - Lohse, T.

AU - Marcowith, A.

AU - Masterson, C.

AU - McComb, T. J.L.

AU - De Naurois, M.

AU - Nolan, S. J.

AU - Noutsos, A.

AU - Orford, K. J.

AU - Osborne, J. L.

AU - Ouchrif, M.

AU - Panter, M.

AU - Pelletier, G.

AU - Pita, S.

AU - Pühlhofer, G.

AU - Punch, M.

AU - Raubenheimer, B. C.

AU - Raue, M.

AU - Raux, J.

AU - Rayner, S. M.

AU - Redondo, I.

AU - Reimer, A.

AU - Reimer, O.

AU - Ripken, J.

AU - Rob, L.

AU - Rolland, L.

AU - Rowell, G.

AU - Sahakian, V.

AU - Saugé, L.

AU - Schlenker, S.

AU - Schlickeiser, R.

AU - Schuster, C.

AU - Schwanke, U.

AU - Siewert, M.

AU - Sol, H.

AU - Steenkamp, R.

AU - Stegmann, C.

AU - Tavernet, J. P.

AU - Terrier, R.

AU - Théoret, C. G.

AU - Tluczykont, M.

AU - Vasileiadis, G.

AU - Venter, C.

AU - Vincent, P.

AU - Völk, H. J.

AU - Wagner, S. J.

PY - 2005/7/1

Y1 - 2005/7/1

N2 - Mkn 421 was observed during a high flux state for nine nights in April and May 2004 with the fully operational High Energy Stereoscopic System (HESS) in Namibia. The observations were carried out at zenith angles of 60°-65°, which result in an average energy threshold of 1.5 TeV and a collection area reaching 2 km2 at 10 TeV. Roughly 7000 photons from Mkn 421 were accumulated with an average gamma-ray rate of 8 photons/min. The overall significance of the detection exceeds 100 standard deviations. The light-curve of integrated fluxes above 2 TeV shows changes of the diurnal flux up to a factor of 4.3. For nights of high flux, intra-night variability is detected with a decay time of less than 1 h. The time averaged energy spectrum is curved and is well described by a power-law with a photon index Γ = 2.1 ± 0.1stat ± 0.3sys and an exponential cutoff at Ec = 3.1(+0.5 - 0.4)stat ± 0.9sys TeV and an average integral flux above 2 TeV of 3 Crab flux units. Significant variations of the spectral shape are detected with a spectral hardening as the flux increases. Contemporaneous multi-wavelength observations at lower energies (X-rays and gamma-rays above ≈300 GeV) indicate smaller relative variability amplitudes than seen above 2 TeV during high flux state observed in April 2004.

AB - Mkn 421 was observed during a high flux state for nine nights in April and May 2004 with the fully operational High Energy Stereoscopic System (HESS) in Namibia. The observations were carried out at zenith angles of 60°-65°, which result in an average energy threshold of 1.5 TeV and a collection area reaching 2 km2 at 10 TeV. Roughly 7000 photons from Mkn 421 were accumulated with an average gamma-ray rate of 8 photons/min. The overall significance of the detection exceeds 100 standard deviations. The light-curve of integrated fluxes above 2 TeV shows changes of the diurnal flux up to a factor of 4.3. For nights of high flux, intra-night variability is detected with a decay time of less than 1 h. The time averaged energy spectrum is curved and is well described by a power-law with a photon index Γ = 2.1 ± 0.1stat ± 0.3sys and an exponential cutoff at Ec = 3.1(+0.5 - 0.4)stat ± 0.9sys TeV and an average integral flux above 2 TeV of 3 Crab flux units. Significant variations of the spectral shape are detected with a spectral hardening as the flux increases. Contemporaneous multi-wavelength observations at lower energies (X-rays and gamma-rays above ≈300 GeV) indicate smaller relative variability amplitudes than seen above 2 TeV during high flux state observed in April 2004.

KW - Galaxies: individual: Mkn 421

UR - https://www.scopus.com/pages/publications/21244501407

U2 - 10.1051/0004-6361:20053050

DO - 10.1051/0004-6361:20053050

M3 - Article

AN - SCOPUS:21244501407

SN - 0004-6361

VL - 437

SP - 95

EP - 99

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

IS - 1

ER -

Observations of Mkn 421 in 2004 with HESS at large zenith angles

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Keywords

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