J/A+A/640/A43 10-year Fermi LAT results for the Crab pulsar (Yeung, 2020)
Inferring the origins of the pulsed gamma-ray emission from the Crab pulsar
with ten-year Fermi LAT data.
Yeung P.K.H.
<Astron. Astrophys. 640, A43 (2020)>
=2020A&A...640A..43Y 2020A&A...640A..43Y (SIMBAD/NED BibCode)
ADC_Keywords: Pulsars ; Gamma rays
Keywords: pulsars: individual: Crab pulsar - gamma rays: stars
Abstract:
The Crab pulsar is a bright gamma-ray source, which has been detected
at photon energies up to ∼1TeV. Its phase-averaged and phase-resolved
gamma-ray spectra below 10GeV exhibit exponential cutoffs, while those
above 10GeV apparently follow simple power laws.
We re-visit the gamma-ray properties of the Crab pulsar with ten-year
Fermi Large Area Telescope (LAT) data in the range of 60MeV-500GeV.
With the phase-resolved spectra, we investigate the origins and
mechanisms responsible for the emissions.
The phaseograms were reconstructed for different energy bands and
further analysed using a wavelet decomposition. The phase-resolved
energy spectra were combined with the observations of ground-based
instruments, such as MAGIC and VERITAS, to achieve a larger energy
converage. We fitted power-law models to the overlapping energy
spectra from 10GeV to ∼1TeV. In the fit, we included a relative
cross-calibration of energy scales between air-shower-based gamma-ray
telescopes with the orbital pair-production telescope from the Fermi
mission.
We confirm the energy-dependence of the gamma-ray pulse shape and,
equivalently, the phase-dependence of the spectral shape for the Crab
pulsar. A relatively sharp cutoff at a relatively high energy of ∼8GeV
is observed for the bridge-phase emission. The E>10 GeV spectrum
observed for the second pulse peak is harder than those for other
phases.
In view of the diversity of phase-resolved spectral shapes of the Crab
pulsar, we tentatively propose a multi-origin scenario where the
polar-cap, outer-gap, and relativistic-wind regions are involved.
Description:
We select the Pass8 "Clean" class data of 60MeV-500GeV photon
energies, registered with Fermi LAT between 2008 August 4 and 2018
August 20. The binned maximum-likelihood analyses are performed with
the instrument response function "P8R2CLEANV6". The 4FGL source
catalog, the Galactic diffuse model "glliemv06" and the isotropic
diffuse model "isoP8R2CLEANV6v06" are used for background
subtraction.
Objects:
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RA (2000) DE Designation(s)
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05 34 31.94 +22 00 52.2 Crab pulsar = V* CM Tau
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig1.dat 89 44 Phaseograms in different energy bands (Fig. 1)
fig3.dat 49 19 Phase-averaged pulsar & nebular spectra (Fig. 3)
fig4.dat 149 17 Phase-resolved pulsar spectra (Fig. 4)
fig9.dat 69 4 >10GeV pulsar spectra (dedicated to joint fits
with IACT data; Fig. 9)
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See also:
J/A+AS/124/123 : Atlas of the Crab pulsar pulse profiles (Massaro+ 1997)
J/A+A/565/L12 : Crab pulsar 50-400GeV light curve (Aleksic+, 2014)
Byte-by-byte Description of file: fig1.dat
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Bytes Format Units Label Explanations
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1- 6 F6.4 --- Phbc Pulse phase at the bin center
8- 17 E10.3 10-9ph/cm2/s F60MeV Pulsed flux in 60-600MeV per 0.02 phase
19- 27 E9.3 10-9ph/cm2/s e_F60MeV 1-sigma uncertainty of F60MeV
29- 37 E9.3 10-9ph/cm2/s F0.6GeV Pulsed flux in 0.6-6GeV per 0.2 phase
39- 47 E9.3 10-9ph/cm2/s e_F0.6GeV 1-sigma uncertainty of F0.6GeV
49- 58 E10.3 10-9ph/cm2/s F6GeV Pulsed flux in 6-60GeV per 0.02 phase
60- 68 E9.3 10-9ph/cm2/s e_F6GeV 1-sigma uncertainty of F6GeV
70- 79 E10.3 10-9ph/cm2/s F20GeV Pulsed flux in 20-500GeV per 0.2 phase
81- 89 E9.3 10-9ph/cm2/s e_F20GeV 1-sigma uncertainty of F20GeV
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Byte-by-byte Description of file: fig3.dat
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Bytes Format Units Label Explanations
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1- 9 E9.3 GeV Ebc Photon energy at the bin center
11- 19 E9.3 10-15W/m2 FPSR ? E2dN/dE of the pulsar
21- 29 E9.3 10-15W/m2 e_FPSR ? 1-sigma uncertainty of FPSR
31- 39 E9.3 10-15W/m2 FNeb E2dN/dE of the nebula
41- 49 E9.3 10-15W/m2 e_FNeb 1-sigma uncertainty of FNeb
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Byte-by-byte Description of file: fig4.dat
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Bytes Format Units Label Explanations
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1- 9 E9.3 GeV Ebc Photon energy at the bin center
11- 19 E9.3 10-15W/m2 FLW1 ? E2dN/dE/delta at LW1 (phase 0.88-0.96)
21- 29 E9.3 10-15W/m2 e_FLW1 ? 1-sigma uncertainty of FLW1
31- 39 E9.3 10-15W/m2 FP1 ? E2dN/dE/delta at P1 (phase 0.96-0.02)
41- 49 E9.3 10-15W/m2 e_FP1 ? 1-sigma uncertainty of FP1
51- 59 E9.3 10-15W/m2 FTW1 ? E2dN/dE/delta at TW1 (phase 0.02-0.12)
61- 69 E9.3 10-15W/m2 e_FTW1 ? 1-sigma uncertainty of FTW1
71- 79 E9.3 10-15W/m2 FBD ? E2dN/dE/delta at BD (phase 0.12-0.20)
81- 89 E9.3 10-15W/m2 e_FBD ? 1-sigma uncertainty of FBD
91- 99 E9.3 10-15W/m2 FLW2 ? E2dN/dE/delta at LW2 (phase 0.20-0.36)
101-109 E9.3 10-15W/m2 e_FLW2 ? 1-sigma uncertainty of FLW2
111-119 E9.3 10-15W/m2 FP2 E2dN/dE/delta at P2 (phase 0.36-0.42)
121-129 E9.3 10-15W/m2 e_FP2 1-sigma uncertainty of FP2
131-139 E9.3 10-15W/m2 FTW2 ? E2dN/dE/delta at TW2 (phase 0.42-0.58)
141-149 E9.3 10-15W/m2 e_FTW2 ? 1-sigma uncertainty of FTW2
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Byte-by-byte Description of file: fig9.dat
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Bytes Format Units Label Explanations
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1- 9 E9.3 GeV Ebc Measured photon energy at the bin center
11- 19 E9.3 10-15W/m2 Ffp E2dN/dE in the full-phase
21- 29 E9.3 10-15W/m2 e_Ffp 1-sigma uncertainty of Ffp
31- 39 E9.3 10-15W/m2 FP1M ? E2dN/dE/delta at P1M (phase 0.983-0.026)
41- 49 E9.3 10-15W/m2 e_FP1M ? 1-sigma uncertainty of FP1M
51- 59 E9.3 10-15W/m2 FP2M E2dN/dE/delta at P2M (phase 0.377-0.422)
61- 69 E9.3 10-15W/m2 e_FP2M 1-sigma uncertainty of FP2M
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Acknowledgements:
Paul Kin Hang, kin.hang.yeung(at)desy.de
(End) Patricia Vannier [CDS] 30-Jun-2020