Long-term evolution of cyclotron resonant scattering features in the accreting pulsar Vela X-1: A pulse-to-pulse approach

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Table 2.

Best-fit parameters of the phase-averaged spectrum for ObsID 91002349002 using the model const×tbabs×pcfabs(gauss+gauss+gabs×gabs×fdcut) in the 3–70 keV energy band.

Parameter	Value
C_FPMA (fixed)	1
C_FPMB	$1 . 0100_{- 0.0005}^{+ 0.0013}$ $1.0100_{-0.0005}^{+0.0013}$
N_H1 [10²² cm⁻²] (fixed)	0.371
N_H2 [10²² cm⁻²]	$20 . 8_{- 0.9}^{+ 1.1}$ $20.8_{-0.9}^{+1.1}$
CF	$0 . 30_{- 0.01}^{+ 0.01}$ $0.30_{-0.01}^{+0.01}$
E_10 keV [keV]	$8 . 6_{- 0.2}^{+ 0.2}$ $8.6_{-0.2}^{+0.2}$
σ_10 keV [keV]	$3 . 1_{- 0.2}^{+ 0.2}$ $3.1_{-0.2}^{+0.2}$
Norm_10 keV	$- 0 . 014_{- 0.003}^{+ 0.002}$ $-0.014_{-0.003}^{+0.002}$
E_Kα [keV]	$6 . 341_{- 0.005}^{+ 0.005}$ $6.341_{-0.005}^{+0.005}$
σ_Kα [keV]	$0 . 051_{- 0.036}^{+ 0.014}$ $0.051_{-0.036}^{+0.014}$
Norm_Kα	$0 . 00175_{- 0.00008}^{+ 0.00005}$ $0.00175_{-0.00008}^{+0.00005}$
E_cyc, F [keV]	$24 . 55_{- 0.48}^{+ 0.48}$ $24.55_{-0.48}^{+0.48}$
σ_cyc, F [keV]	0.5 × σ_cyc, H
d_cyc, F	$0 . 46_{- 0.07}^{+ 0.14}$ $0.46_{-0.07}^{+0.14}$
E_cyc, H [keV]	$52 . 63_{- 0.32}^{+ 0.57}$ $52.63_{-0.32}^{+0.57}$
σ_cyc, H [keV]	$7 . 24_{- 0.38}^{+ 0.64}$ $7.24_{-0.38}^{+0.64}$
d_cyc, H	$14 . 98_{- 1.44}^{+ 2.52}$ $14.98_{-1.44}^{+2.52}$
E_cut [keV]	$22 . 2_{- 1.3}^{+ 0.9}$ $22.2_{-1.3}^{+0.9}$
E_fold [keV]	$10 . 8_{- 0.2}^{+ 0.4}$ $10.8_{-0.2}^{+0.4}$
Γ	$1 . 08_{- 0.02}^{+ 0.01}$ $1.08_{-0.02}^{+0.01}$
Norm_Γ	$0 . 267_{- 0.005}^{+ 0.008}$ $0.267_{-0.005}^{+0.008}$
Flux_{3 − 79 keV}	$6 . 592_{- 0.014}^{+ 0.014}$ $6.592_{-0.014}^{+0.014}$
χ²/d.o.f.	555.27/448

Notes. All reported errors are at the 68% confidence level and based on the MCMC chain values. Normalization of the power law in units of photon cm⁻² s⁻¹ keV⁻¹ at 1 keV. Unabsorbed flux (in units of 10⁻⁹ erg cm⁻² s⁻¹) calculated for the entire model, obtained using the cflux command from XSPEC. Uncertainties are given for a 68% confidence level.

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