Fermi Large Area Telescope observations of the fast-dimming Crab Nebula in 60–600 MeV

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Volume 638 (June 2020)

A&A, 638 (2020) A147

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Table 4.

60 MeV–10 GeV spectral properties of the Crab Nebula measured in different flux states.

Component	State ^(b)	PL Γ	PLEC Γ	PLEC E_c	TS_PLEC − TS_PL^(c)	Integrated flux ^(d)
				(GeV)		(10⁻⁹ cm⁻² s⁻¹)
IC ^(a)	Average	1.415 ± 0.023	…	…	…	107 ± 5

	High	2.830 ± 0.015	2.497 ± 0.041	0.77 ± 0.10	114.1	8432 ± 92
Synchrotron	Average	3.278 ± 0.011	3.250, ± 0.026	6.6 ± 5.7	1.7	2534 ± 15
	Low	…	…	…	…	370 ± 130

Syn+IC	Low	1.653 ± 0.048	…	…	…	221 ± 22

Notes.

^(a)

The parameters of the IC component are determined from the complete ten-year data set, and are assumed to remain constant.

^(b)

The high and low states are defined based on the 60 MeV–600 MeV light curve of the Crab Nebula (Fig. 2).

^(c)

Γ is the photon index. E_c is the energy of the exponential cutoff. TS_PLEC − TS_PL is the difference in test-statistic (TS) between PLEC and PL.

^(d)

For the high state and the average, the integral fluxes of the synchrotron component are based on PLEC and PL models respectively. For the low state, it is the sum over the binned spectrum subtracting the IC component.

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