XMM-Newton multi-year campaign on NGC 55 ULX-1 - Resolving the wind and its variability with RGS

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Table 1.

Best-fit plasma parameters in each EPIC+RGS spectral fit.

Parameter	Combined	0655050101	0824570101	0864810101	0883960101
L_BOL (10³⁹ erg/s)	1.68 ± 0.03	1.71 ± 0.03	1.26 ± 0.05	1.69 ± 0.05	2.08 ± 0.05
$L_{BOL}^{corr}$ $L_{\mathrm{BOL}}^{\mathrm{corr}}$ (10³⁹ erg/s)	2.58	2.92	1.70	2.75	2.33
Hardness	0.097 ± 0.002	0.092 ± 0.004	0.102 ± 0.004	0.103 ± 0.004	0.089 ± 0.004
RMS (%)	–	12.3 ± 0.3	3.73 ± 0.01	15.34 ± 0.04	7.79 ± 0.01

$v_{LOS}^{xabs}$ $v_{\mathrm{LOS}}^{\mathrm{xabs}}$ (c)	−0.156 ± 0.001	−0.176 ± 0.001	−0.141 ± 0.002	−0.107 ± 0.001	−0.046 ± 0.001
$v_{σ}^{xabs}$ $v_{\sigma}^{\mathrm{xabs}}$ (km/s)	100 ± 30	50 ± 50	250 ± 250	100 ± 50	480 ± 480
log ξ^xabs (erg/s cm)	4.06 ± 0.09	3.94 ± 0.15	3.81 ± 0.15	3.97 ± 0.17	1.26 ± 0.17
$N_{H}^{xabs}$ $N_{\mathrm{H}}^{\mathrm{xabs}}$ (10²⁴/cm²)	0.65 ± 0.21	0.62 ± 0.25	0.33 ± 0.12	0.55 ± 0.31	0.06 ± 0.03
ΔC	53	27	26	21	22
CL (σ)	> 5	3.6	3.5	2.9	3.0

$v_{LOS}^{pion}$ $v_{\mathrm{LOS}}^{\mathrm{pion}}$ (c)	−0.082 ± 0.001	−0.006 ± 0.001	−0.079 ± 0.001	0.009 ± 0.001	−0.140 ± 0.001
$v_{σ}^{pion}$ $v_{\sigma}^{\mathrm{pion}}$ (km/s)	400 ± 400	100 ± 100	100 ± 100	700 ± 560	500 ± 500
log ξ^pion (erg/s cm)	2.5 ± 0.1	0.94 ± 0.1	1.1 ± 0.1	0.25 ± 0.05	0.05 ± 0.05
$L_{X}^{pion}$ $L_{\mathrm{X}}^{\mathrm{pion}}$ (10³⁸ erg/s)	0.60 ± 0.09	0.83 ± 0.17	0.42 ± 0.12	1.21 ± 0.28	0.81 ± 0.17
ΔC	42	36	17	24	27
CL (σ)	> 5	4.8	< 2.5	3.3	3.6

$v_{LOS}^{cie}$ $v_{\mathrm{LOS}}^{\mathrm{cie}}$ (c)	−0.004 ± 0.017	−0.006 ± 0.001	−0.030 ± 0.004	0.028 ± 0.006	−0.136 ± 0.001
$v_{σ}^{cie}$ $v_{\sigma}^{\mathrm{cie}}$ (km/s)	7000 ± 3000	350 ± 350	1000 ± 1000	4074 ± 2600	342 ± 342
$k T_{e}^{cie}$ $kT_{\mathrm{e}}^{\mathrm{cie}}$ (keV)	1.4 ± 0.1	0.18 ± 0.02	2.05 ± 0.23	0.11 ± 0.02	0.07 ± 0.01
$L_{X}^{cie}$ $L_{\mathrm{X}}^{\mathrm{cie}}$ (10³⁸ erg/s)	1.53 ± 0.32	0.90 ± 0.28	0.92 ± 0.20	2.53 ± 1.12	1.86 ± 0.99
ΔC	41	26	22	21	22
CL (σ)	> 5	3.5	3.0	2.9	3.0

Notes. Bolometric luminosities are computed within 10⁻⁴ − 10² keV. The root mean square (RMS, in %) was computed using the 0.3−10 keV EPIC-pn light curves (time bin size of 1 ks, taken from B22). $L_{BOL}^{corr}$ $L_{\mathrm{BOL}}^{\mathrm{corr}}$ indicates the luminosity corrected for photoionised xabs absorption. The spectral hardness (estimated from continuum-only fits) yields the ratio of the hard to soft X-ray luminosities (L_{2 − 10 keV}/L_{0.3 − 2 keV}). The X-ray luminosities of the plasma emitting components refer to the 0.3−10 keV band. The value of ΔC shows the fit improvement; the confidence level (CL) expressed in σ units is computed through MC simulations (see Sect. 4.3) and has an uncertainty of about 0.1σ.

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