Revealing two orthogonally polarized spectral components in Vela X-1 with IXPE

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Table 2.

Spectro-polarimetric parameters in different pulse-phase bins for the low- (LE) and high-energy (HE) bands.

Phase	q_LE	u_LE	PD_LE	PA_LE	χ²/d.o.f.	q_HE	u_HE	PD_HE	PA_HE	χ²/d.o.f.
	(%)	(%)	(%)	(deg)		(%)	(%)	(%)	(deg)
0.000–0.100	2.3 ± 3.7	3.5 ± 3.7	$2 . 7_{- 2.7}^{+ 3.6}$ $2.7_{-2.7}^{+3.6}$	33 ± 90	245/211	2.6 ± 2.6	−5.1 ± 2.6	5.7 ± 2.2	−28 ± 11	653/584
0.100–0.150	−0.1 ± 4.6	2.2 ± 4.6	$4 . 2_{- 4.2}^{+ 4.5}$ $4.2_{-4.2}^{+4.5}$	28 ± 90	239/211	−2.0 ± 3.3	−10.1 ± 3.3	8.1 ± 2.8	−44 ± 10	547/518
0.150–0.200	−2.7 ± 5.1	4.0 ± 5.1	$4 . 2_{- 4.2}^{+ 4.9}$ $4.2_{-4.2}^{+4.9}$	68 ± 90	225/211	1.1 ± 3.5	−20.0 ± 3.5	15.2 ± 2.9	−43 ± 5	534/518
0.200–0.300	3.8 ± 3.8	0.4 ± 3.8	4.2 ± 3.7	−18 ± 32	221/211	0.9 ± 2.4	−6.0 ± 2.4	5.7 ± 2.0	−49 ± 10	613/617
0.300–0.400	−2.1 ± 3.2	−1.0 ± 3.2	$2 . 5_{- 2.5}^{+ 3.1}$ $2.5_{-2.5}^{+3.1}$	−89 ± 90	231/211	0.1 ± 2.4	−4.5 ± 2.4	4.1 ± 2.0	−45 ± 14	786/605
0.400–0.500	−1.4 ± 4.2	5.1 ± 4.2	6.7 ± 4.1	66 ± 19	234/211	−3.0 ± 3.0	1.6 ± 3.0	$2 . 3_{- 2.3}^{+ 2.5}$ $2.3_{-2.3}^{+2.5}$	73 ± 90	612/560
0.500–0.600	2.4 ± 4.4	4.3 ± 4.4	$1 . 2_{- 1.2}^{+ 4.3}$ $1.2_{-1.2}^{+4.3}$	21 ± 90	256/211	1.0 ± 2.9	3.7 ± 2.9	2.7 ± 2.4	59 ± 31	592/566
0.600–0.650	4.5 ± 5.9	18.0 ± 5.9	17.0 ± 5.8	35 ± 10	209/211	−11.3 ± 4.0	−12.7 ± 4.0	14.5 ± 3.3	−65 ± 7	510/488
0.650–0.700	−4.9 ± 6.0	6.1 ± 6.0	9.9 ± 5.8	65 ± 18	204/211	−13.0 ± 3.8	−18.6 ± 3.8	18.3 ± 3.2	−65 ± 5	526/497
0.700–0.775	1.0 ± 5.2	−0.1 ± 5.2	$1 . 9_{- 1.9}^{+ 5.0}$ $1.9_{-1.9}^{+5.0}$	−9 ± 90	202/211	−3.6 ± 3.2	−11.4 ± 3.2	11.1 ± 2.7	−53 ± 7	558/548
0.775–0.875	2.4 ± 4.1	5.8 ± 4.1	5.3 ± 4.0	39 ± 25	188/211	−2.0 ± 2.8	−5.8 ± 2.8	6.9 ± 2.3	−57 ± 10	552/578
0.875–1.000	−0.3 ± 4.0	8.5 ± 4.0	9.0 ± 3.9	51 ± 13	258/211	2.6 ± 3.0	−0.4 ± 3.0	2.9 ± 2.5	−4 ± 29	607/557

Notes. PD and PA are obtained with XSPEC. Normalized Stokes parameters q and u are obtained using the pcube algorithm in IXPEOBSSIM. The uncertainties computed using the error command are given at the 68.3% (1σ) confidence level (Δχ² = 1 for one parameter of interest).

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