How the spin-phase variability of cyclotron lines shapes the pulsed fraction spectra: Insights from 4U 1538–52

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Table 3.

Best-fit results for the phase-averaged spectra.

Parameter (unit)	304	306-2
N_H (10²² cm⁻²)	(1)	(1)
E_cut (keV)	$14 . 11_{- 0.14}^{+ 0.19}$ $14.11_{-0.14}^{+0.19}$	$15 . 4_{- 0.2}^{+ 1.4}$ $15.4_{-0.2}^{+1.4}$
E_fold (keV)	10.64 ± 0.10	$10 . 27_{- 0.75}^{+ 0.14}$ $10.27_{-0.75}^{+0.14}$
Γ	0.902 ± 0.018	$0 . 885_{- 0.052}^{+ 0.018}$ $0.885_{-0.052}^{+0.018}$
E_width	(5)	(5)
N_newhcut	0.0230 ± 0.0010	$0 . 0168_{- 0.0017}^{+ 0.0007}$ $0.0168_{-0.0017}^{+0.0007}$
kT (keV)	(1)	(1)
N_bbody	(8.8 ± 0.5)×10⁻⁴	$(6 . 5_{- 0.4}^{+ 0.8}) \times 10^{- 4}$ $(6.5_{-0.4}^{+0.8}) \times 10^{-4}$

E_cyc (keV)	$20 . 84_{- 0.09}^{+ 0.07}$ $20.84_{-0.09}^{+0.07}$	$20 . 51_{- 0.33}^{+ 0.10}$ $20.51_{-0.33}^{+0.10}$
σ_cyc (keV)	$3 . 42_{- 0.12}^{+ 0.17}$ $3.42_{-0.12}^{+0.17}$	$3 . 86_{- 0.14}^{+ 0.50}$ $3.86_{-0.14}^{+0.50}$
D_cyc	0.580 ± 0.012	$0 . 68_{- 0.02}^{+ 0.13}$ $0.68_{-0.02}^{+0.13}$

E_Fe (keV)	(6.4)	(6.4)
σ_Gauss (keV)	$0 . 35_{- 0.03}^{+ 0.04}$ $0.35_{-0.03}^{+0.04}$	$0 . 20_{- 0.04}^{+ 0.07}$ $0.20_{-0.04}^{+0.07}$
N_Gauss	(4.6 ± 0.4)×10⁻⁴	$(3 . 0_{- 0.3}^{+ 0.4}) \times 10^{- 4}$ $(3.0_{-0.3}^{+0.4}) \times 10^{-4}$

C_FPMB	0.979 ± 0.002	1.011 ± 0.004
Flux ^(a)	8.8	6.7

W-stat/d.o.f.	1.172/312	1.036/297

Notes.

^(a)

Absorbed flux range: 4−50 keV in units of 10⁻¹⁰ erg cm⁻² s⁻¹.

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