Observation and spectral measurements of the crab nebula with Milagro

A. A. Abdo, B. T. Allen, R. Atkins, T. Aune, W. Benbow, D. Berley, E. Blaufuss, E. Bonamente, J. Bussons, C. Chen, G. E. Christopher, D. G. Coyne, T. Deyoung, B. L. Dingus, D. E. Dorfan, R. W. Ellsworth, A. Falcone, L. Fleysher, Roman Fleysher, J. Galbraith-FrewM. M. Gonzalez, J. A. Goodman, T. J. Haines, E. Hays, C. M. Hoffman, P. H. Hüntemeyer, L. A. Kelley, B. E. Kolterman, C. P. Lansdell, J. T. Linnemann, J. McCullough, J. E. McEnery, T. Morgan, A. I. Mincer, M. F. Morales, P. Nemethy, D. Noyes, J. Pretz, J. M. Ryan, F. W. Samuelson, P. M. Saz Parkinson, A. Shoup, G. Sinnis, A. J. Smith, G. W. Sullivan, V. Vasileiou, G. P. Walker, M. Wascko, D. A. Williams, S. Westerhoff, G. B. Yodh

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

The Crab Nebula was detected with the Milagro experiment at a statistical significance of 17 standard deviations over the lifetime of the experiment. The experiment was sensitive to approximately 100GeV-100TeV gamma-ray air showers by observing the particle footprint reaching the ground. The fraction of detectors recording signals from photons at the ground is a suitable proxy for the energy of the primary particle and has been used to measure the photon energy spectrum of the Crab Nebula between ∼1 and ∼100TeV. The TeV emission is believed to be caused by inverse-Compton upscattering of ambient photons by an energetic electron population. The location of a TeV steepening or cutoff in the energy spectrum reveals important details about the underlying electron population. We describe the experiment and the technique for distinguishing gamma-ray events from the much more-abundant hadronic events. We describe the calculation of the significance of the excess from the Crab and how the energy spectrum is fitted. The differential photon energy spectrum, including the statistical errors from the fit, obtained using a simple power-law hypothesis for data between 2005 September and 2008 March is (6.5 ± 0.4) × 10-14(E/10 TeV)-3.1±0.1(cm2 s TeV )-1 between ∼1TeV and 100TeV. Allowing for a possible exponential cutoff, the photon energy spectrum is fitted as (2.5+0.7 - 0.4) × 10-12(E/3 TeV)-2.5 ± 0.4exp (- E/32+39 - 18 TeV) (cm2 s TeV)-1. The results are subject to an 30% systematic uncertainty in the overall flux and an ∼0.1 systematic uncertainty in the power-law indices quoted. Uncertainty in the overall energy scale has been absorbed into these errors. Fixing the spectral index to values that have been measured below 1TeV by IACT experiments (2.4-2.6), the fit to the Milagro data suggests that Crab exhibits a spectral steepening or cutoff between about 20-40TeV.

Original languageEnglish (US)
Article number63
JournalAstrophysical Journal
Volume750
Issue number1
DOIs
StatePublished - May 1 2012
Externally publishedYes

Fingerprint

Crab nebula
crab
energy spectra
photons
crabs
cut-off
energy
gamma rays
experiment
power law
cosmic ray showers
footprints
fixing
electron
standard deviation
electrons
recording
footprint
life (durability)
energetics

Keywords

  • acceleration of particles
  • astroparticle physics
  • gamma rays: general
  • pulsars: individual (Crab Pulsar)

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Abdo, A. A., Allen, B. T., Atkins, R., Aune, T., Benbow, W., Berley, D., ... Yodh, G. B. (2012). Observation and spectral measurements of the crab nebula with Milagro. Astrophysical Journal, 750(1), [63]. https://doi.org/10.1088/0004-637X/750/1/63

Observation and spectral measurements of the crab nebula with Milagro. / Abdo, A. A.; Allen, B. T.; Atkins, R.; Aune, T.; Benbow, W.; Berley, D.; Blaufuss, E.; Bonamente, E.; Bussons, J.; Chen, C.; Christopher, G. E.; Coyne, D. G.; Deyoung, T.; Dingus, B. L.; Dorfan, D. E.; Ellsworth, R. W.; Falcone, A.; Fleysher, L.; Fleysher, Roman; Galbraith-Frew, J.; Gonzalez, M. M.; Goodman, J. A.; Haines, T. J.; Hays, E.; Hoffman, C. M.; Hüntemeyer, P. H.; Kelley, L. A.; Kolterman, B. E.; Lansdell, C. P.; Linnemann, J. T.; McCullough, J.; McEnery, J. E.; Morgan, T.; Mincer, A. I.; Morales, M. F.; Nemethy, P.; Noyes, D.; Pretz, J.; Ryan, J. M.; Samuelson, F. W.; Saz Parkinson, P. M.; Shoup, A.; Sinnis, G.; Smith, A. J.; Sullivan, G. W.; Vasileiou, V.; Walker, G. P.; Wascko, M.; Williams, D. A.; Westerhoff, S.; Yodh, G. B.

In: Astrophysical Journal, Vol. 750, No. 1, 63, 01.05.2012.

Research output: Contribution to journalArticle

Abdo, AA, Allen, BT, Atkins, R, Aune, T, Benbow, W, Berley, D, Blaufuss, E, Bonamente, E, Bussons, J, Chen, C, Christopher, GE, Coyne, DG, Deyoung, T, Dingus, BL, Dorfan, DE, Ellsworth, RW, Falcone, A, Fleysher, L, Fleysher, R, Galbraith-Frew, J, Gonzalez, MM, Goodman, JA, Haines, TJ, Hays, E, Hoffman, CM, Hüntemeyer, PH, Kelley, LA, Kolterman, BE, Lansdell, CP, Linnemann, JT, McCullough, J, McEnery, JE, Morgan, T, Mincer, AI, Morales, MF, Nemethy, P, Noyes, D, Pretz, J, Ryan, JM, Samuelson, FW, Saz Parkinson, PM, Shoup, A, Sinnis, G, Smith, AJ, Sullivan, GW, Vasileiou, V, Walker, GP, Wascko, M, Williams, DA, Westerhoff, S & Yodh, GB 2012, 'Observation and spectral measurements of the crab nebula with Milagro', Astrophysical Journal, vol. 750, no. 1, 63. https://doi.org/10.1088/0004-637X/750/1/63
Abdo AA, Allen BT, Atkins R, Aune T, Benbow W, Berley D et al. Observation and spectral measurements of the crab nebula with Milagro. Astrophysical Journal. 2012 May 1;750(1). 63. https://doi.org/10.1088/0004-637X/750/1/63
Abdo, A. A. ; Allen, B. T. ; Atkins, R. ; Aune, T. ; Benbow, W. ; Berley, D. ; Blaufuss, E. ; Bonamente, E. ; Bussons, J. ; Chen, C. ; Christopher, G. E. ; Coyne, D. G. ; Deyoung, T. ; Dingus, B. L. ; Dorfan, D. E. ; Ellsworth, R. W. ; Falcone, A. ; Fleysher, L. ; Fleysher, Roman ; Galbraith-Frew, J. ; Gonzalez, M. M. ; Goodman, J. A. ; Haines, T. J. ; Hays, E. ; Hoffman, C. M. ; Hüntemeyer, P. H. ; Kelley, L. A. ; Kolterman, B. E. ; Lansdell, C. P. ; Linnemann, J. T. ; McCullough, J. ; McEnery, J. E. ; Morgan, T. ; Mincer, A. I. ; Morales, M. F. ; Nemethy, P. ; Noyes, D. ; Pretz, J. ; Ryan, J. M. ; Samuelson, F. W. ; Saz Parkinson, P. M. ; Shoup, A. ; Sinnis, G. ; Smith, A. J. ; Sullivan, G. W. ; Vasileiou, V. ; Walker, G. P. ; Wascko, M. ; Williams, D. A. ; Westerhoff, S. ; Yodh, G. B. / Observation and spectral measurements of the crab nebula with Milagro. In: Astrophysical Journal. 2012 ; Vol. 750, No. 1.
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abstract = "The Crab Nebula was detected with the Milagro experiment at a statistical significance of 17 standard deviations over the lifetime of the experiment. The experiment was sensitive to approximately 100GeV-100TeV gamma-ray air showers by observing the particle footprint reaching the ground. The fraction of detectors recording signals from photons at the ground is a suitable proxy for the energy of the primary particle and has been used to measure the photon energy spectrum of the Crab Nebula between ∼1 and ∼100TeV. The TeV emission is believed to be caused by inverse-Compton upscattering of ambient photons by an energetic electron population. The location of a TeV steepening or cutoff in the energy spectrum reveals important details about the underlying electron population. We describe the experiment and the technique for distinguishing gamma-ray events from the much more-abundant hadronic events. We describe the calculation of the significance of the excess from the Crab and how the energy spectrum is fitted. The differential photon energy spectrum, including the statistical errors from the fit, obtained using a simple power-law hypothesis for data between 2005 September and 2008 March is (6.5 ± 0.4) × 10-14(E/10 TeV)-3.1±0.1(cm2 s TeV )-1 between ∼1TeV and 100TeV. Allowing for a possible exponential cutoff, the photon energy spectrum is fitted as (2.5+0.7 - 0.4) × 10-12(E/3 TeV)-2.5 ± 0.4exp (- E/32+39 - 18 TeV) (cm2 s TeV)-1. The results are subject to an 30{\%} systematic uncertainty in the overall flux and an ∼0.1 systematic uncertainty in the power-law indices quoted. Uncertainty in the overall energy scale has been absorbed into these errors. Fixing the spectral index to values that have been measured below 1TeV by IACT experiments (2.4-2.6), the fit to the Milagro data suggests that Crab exhibits a spectral steepening or cutoff between about 20-40TeV.",
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T1 - Observation and spectral measurements of the crab nebula with Milagro

AU - Abdo, A. A.

AU - Allen, B. T.

AU - Atkins, R.

AU - Aune, T.

AU - Benbow, W.

AU - Berley, D.

AU - Blaufuss, E.

AU - Bonamente, E.

AU - Bussons, J.

AU - Chen, C.

AU - Christopher, G. E.

AU - Coyne, D. G.

AU - Deyoung, T.

AU - Dingus, B. L.

AU - Dorfan, D. E.

AU - Ellsworth, R. W.

AU - Falcone, A.

AU - Fleysher, L.

AU - Fleysher, Roman

AU - Galbraith-Frew, J.

AU - Gonzalez, M. M.

AU - Goodman, J. A.

AU - Haines, T. J.

AU - Hays, E.

AU - Hoffman, C. M.

AU - Hüntemeyer, P. H.

AU - Kelley, L. A.

AU - Kolterman, B. E.

AU - Lansdell, C. P.

AU - Linnemann, J. T.

AU - McCullough, J.

AU - McEnery, J. E.

AU - Morgan, T.

AU - Mincer, A. I.

AU - Morales, M. F.

AU - Nemethy, P.

AU - Noyes, D.

AU - Pretz, J.

AU - Ryan, J. M.

AU - Samuelson, F. W.

AU - Saz Parkinson, P. M.

AU - Shoup, A.

AU - Sinnis, G.

AU - Smith, A. J.

AU - Sullivan, G. W.

AU - Vasileiou, V.

AU - Walker, G. P.

AU - Wascko, M.

AU - Williams, D. A.

AU - Westerhoff, S.

AU - Yodh, G. B.

PY - 2012/5/1

Y1 - 2012/5/1

N2 - The Crab Nebula was detected with the Milagro experiment at a statistical significance of 17 standard deviations over the lifetime of the experiment. The experiment was sensitive to approximately 100GeV-100TeV gamma-ray air showers by observing the particle footprint reaching the ground. The fraction of detectors recording signals from photons at the ground is a suitable proxy for the energy of the primary particle and has been used to measure the photon energy spectrum of the Crab Nebula between ∼1 and ∼100TeV. The TeV emission is believed to be caused by inverse-Compton upscattering of ambient photons by an energetic electron population. The location of a TeV steepening or cutoff in the energy spectrum reveals important details about the underlying electron population. We describe the experiment and the technique for distinguishing gamma-ray events from the much more-abundant hadronic events. We describe the calculation of the significance of the excess from the Crab and how the energy spectrum is fitted. The differential photon energy spectrum, including the statistical errors from the fit, obtained using a simple power-law hypothesis for data between 2005 September and 2008 March is (6.5 ± 0.4) × 10-14(E/10 TeV)-3.1±0.1(cm2 s TeV )-1 between ∼1TeV and 100TeV. Allowing for a possible exponential cutoff, the photon energy spectrum is fitted as (2.5+0.7 - 0.4) × 10-12(E/3 TeV)-2.5 ± 0.4exp (- E/32+39 - 18 TeV) (cm2 s TeV)-1. The results are subject to an 30% systematic uncertainty in the overall flux and an ∼0.1 systematic uncertainty in the power-law indices quoted. Uncertainty in the overall energy scale has been absorbed into these errors. Fixing the spectral index to values that have been measured below 1TeV by IACT experiments (2.4-2.6), the fit to the Milagro data suggests that Crab exhibits a spectral steepening or cutoff between about 20-40TeV.

AB - The Crab Nebula was detected with the Milagro experiment at a statistical significance of 17 standard deviations over the lifetime of the experiment. The experiment was sensitive to approximately 100GeV-100TeV gamma-ray air showers by observing the particle footprint reaching the ground. The fraction of detectors recording signals from photons at the ground is a suitable proxy for the energy of the primary particle and has been used to measure the photon energy spectrum of the Crab Nebula between ∼1 and ∼100TeV. The TeV emission is believed to be caused by inverse-Compton upscattering of ambient photons by an energetic electron population. The location of a TeV steepening or cutoff in the energy spectrum reveals important details about the underlying electron population. We describe the experiment and the technique for distinguishing gamma-ray events from the much more-abundant hadronic events. We describe the calculation of the significance of the excess from the Crab and how the energy spectrum is fitted. The differential photon energy spectrum, including the statistical errors from the fit, obtained using a simple power-law hypothesis for data between 2005 September and 2008 March is (6.5 ± 0.4) × 10-14(E/10 TeV)-3.1±0.1(cm2 s TeV )-1 between ∼1TeV and 100TeV. Allowing for a possible exponential cutoff, the photon energy spectrum is fitted as (2.5+0.7 - 0.4) × 10-12(E/3 TeV)-2.5 ± 0.4exp (- E/32+39 - 18 TeV) (cm2 s TeV)-1. The results are subject to an 30% systematic uncertainty in the overall flux and an ∼0.1 systematic uncertainty in the power-law indices quoted. Uncertainty in the overall energy scale has been absorbed into these errors. Fixing the spectral index to values that have been measured below 1TeV by IACT experiments (2.4-2.6), the fit to the Milagro data suggests that Crab exhibits a spectral steepening or cutoff between about 20-40TeV.

KW - acceleration of particles

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KW - pulsars: individual (Crab Pulsar)

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