Discovery of energy-dependent phase variations in the polarization angle of Cen X-3

Open Access

Table 4.

Best-fit parameters for the phase-averaged joint spectra of IXPE, NICER, and NuSTAR.

Model Component	Parameter	Value
TBabs	N_H (10²² cm⁻²)	$1 . 256_{- 0.015}^{+ 0.005}$ $Mathematical equation: $ 1.256^{+0.005}_{-0.015} $$

Pcfabs	N_H (10²² cm⁻²)	$2 . 88_{- 0.08}^{+ 0.06}$ $Mathematical equation: $ 2.88^{+0.06}_{-0.08} $$
	Covering fraction	$0 . 570_{- 0.004}^{+ 0.006}$ $Mathematical equation: $ 0.570^{+0.006}_{-0.004} $$

Highecut	E_cut (keV)	$12 . 71_{- 0.02}^{+ 0.03}$ $Mathematical equation: $ 12.71^{+0.03}_{-0.02} $$
	E_fold (keV)	8.21 ± 0.02

Powerlaw	Γ	$1 . 221_{- 0.003}^{+ 0.004}$ $Mathematical equation: $ 1.221^{+0.004}_{-0.003} $$
	Normalization	$0 . 681_{- 0.003}^{+ 0.005}$ $Mathematical equation: $ 0.681^{+0.005}_{-0.003} $$

Gabs	E_line (keV)	2.21 ± 0.01
	Sigma (keV)	0.06 ± 0.01
	Depth (10⁻³)	$63_{- 3}^{+ 1}$ $Mathematical equation: $ 63^{+1}_{-3} $$

Gabs	E_line (keV)	= E_cut
	Sigma (keV)	$2 . 07_{- 0.04}^{+ 0.03}$ $Mathematical equation: $ 2.07^{+0.03}_{-0.04} $$
	Depth	$0 . 68_{- 0.01}^{+ 0.02}$ $Mathematical equation: $ 0.68^{+0.02}_{-0.01} $$

Gauss	E_line (keV)	$1 . 044_{- 0.007}^{+ 0.006}$ $Mathematical equation: $ 1.044^{+0.006}_{-0.007} $$
	Sigma (keV)	$0 . 056_{- 0.009}^{+ 0.006}$ $Mathematical equation: $ 0.056^{+0.006}_{-0.009} $$
	Normalization (10⁻³)	$14_{- 1}^{+ 2}$ $Mathematical equation: $ 14^{+2}_{-1} $$

Gauss	E_line (keV)	6.493 ± 0.005
	Sigma (keV)	$0 . 292_{- 0.005}^{+ 0.006}$ $Mathematical equation: $ 0.292^{+0.006}_{-0.005} $$
	Normalization (10⁻³)	8.7 ± 0.1

Gabs	E_line (keV)	$30 . 3_{- 0.1}^{+ 0.2}$ $Mathematical equation: $ 30.3^{+0.2}_{-0.1} $$
	Sigma (keV)	6.0 ± 0.1
	Depth	$6 . 1_{- 0.2}^{+ 0.3}$ $Mathematical equation: $ 6.1^{+0.3}_{-0.2} $$

Constant	NICER	1.00^fixed
	NuSTAR (FPMA)	$1 . 047_{- 0.002}^{+ 0.001}$ $Mathematical equation: $ 1.047^{+0.001}_{-0.002} $$
	NuSTAR (FPMB)	$1 . 054_{- 0.001}^{+ 0.002}$ $Mathematical equation: $ 1.054^{+0.002}_{-0.001} $$
	IXPE (DU1)	$1 . 043_{- 0.004}^{+ 0.003}$ $Mathematical equation: $ 1.043^{+0.003}_{-0.004} $$
	IXPE (DU2)	$1 . 063_{- 0.004}^{+ 0.002}$ $Mathematical equation: $ 1.063^{+0.002}_{-0.004} $$
	IXPE (DU3)	$1 . 029_{- 0.003}^{+ 0.002}$ $Mathematical equation: $ 1.029^{+0.002}_{-0.003} $$

Gain	NICER Gain slope	$1 . 0177_{- 0.0009}^{+ 0.0004}$ $Mathematical equation: $ 1.0177^{+0.0004}_{-0.0009} $$
	NICER Gain offset (keV)	$- 0 . 035_{- 0.002}^{+ 0.003}$ $Mathematical equation: $ -0.035^{+0.003}_{-0.002} $$
	IXPE (DU1) Gain slope	$1 . 010_{- 0.002}^{+ 0.001}$ $Mathematical equation: $ 1.010^{+0.001}_{-0.002} $$
	IXPE (DU1) Gain offset (keV)	$- 0 . 043_{- 0.003}^{+ 0.007}$ $Mathematical equation: $ -0.043^{+0.007}_{-0.003} $$
	IXPE (DU2) Gain slope	$1 . 006_{- 0.002}^{+ 0.001}$ $Mathematical equation: $ 1.006^{+0.001}_{-0.002} $$
	IXPE (DU2) Gain offset (keV)	$- 0 . 022_{- 0.004}^{+ 0.007}$ $Mathematical equation: $ -0.022^{+0.007}_{-0.004} $$
	IXPE (DU3) Gain slope	1.008 ± 0.001
	IXPE (DU3) Gain offset (keV)	−0.016 ± 0.004

	χ²/d.o.f.	3235.8/3119

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