Table 2
Best-fit parameters of our model for the broadband spectrum of 4U 1820-30.
| Data | bb | comt (a) | hot (cold) (b) | hot (warm) | F0.5−2 keV | Cstat/d.o.f. (c) | ||
|---|---|---|---|---|---|---|---|---|
| kBT | kBT0 | kBT1 | NH | NH | kBT | [10−9] | ||
| keV | keV | keV | 1021 cm−2 | 1020 cm−2 | 10−3 keV | erg cm−2 s−1 | ||
| RGS/XMM-Newton | ||||||||
| 008411 | 0.164 ± 0.003 | 0.65 ± 0.08 | 24 ± 11 | 1.51 ± 0.03 | 0.9 ± 0.2 | 2.6 ± 0.3 | 2.2 ± 0.2 | 5642∕3700 |
| 055134 | 0.139 ± 0.004 | 0.32 ± 0.02 | 29 ± 9 | 1.56 ± 0.03 | 1.2 ± 0.3 | 2.8 ± 0.2 | 1.5 ± 0.3 | 5541∕3921 |
| LETG/Chandra | ||||||||
| 98 | 0.16 ± 0.01 | 0.40 ± 0.08 | 7 ± 5 | 0.08 ± 0.05 | < 0.45 | 2 ± 1 | 1.8 ± 0.8 | 2070∕1842 |
| 12444 | 0.22 ± 0.01 | 1.9 ± 0.7 | 20 ± 9 | 1.4 ± 0.1 | 2.0 ± 0.9 | 4.6 ± 0.4 | 1.5 ± 0.7 | 1141∕870 |
| HETG/Chandra | ||||||||
| 2001 (d) | 0.14 ± 0.04 | 0.20 ± 0.05 | 1.5 ± 0.2 | 1.1 ± 0.2 | 1.5 ± 0.9 | 4 ± 1 | 1.7 ± 0.2 | 7423∕6628 |
| 2006 (e) | 0.07 ± 0.01 | 0.16 ± 0.02 | 9 ± 5 | 2.1 ± 0.1 | 1.2 ± 0.9 | 3 ± 1 | 2.3 ± 0.3 | 6304∕4988 |
| Mean | 0.15 ± 0.01 | 0.6 ± 0.2 | 15 ± 7 | 1.53 ± 0.08 | 1.4 ± 0.6 | 3.4 ± 0.6 | 10 ± 2 | |
Notes. (a) We fix the optical depth τ to its default value of 3. (b) We fix the temperature at the lower limit 0.5 eV. In the cold phase we also consider the contribution of the dust. (c) The total C-stat/dof of the fit is 28123∕21949. (d) Combination of obsId (1021, 1022) taken in 2001. (e)Combination of obsId (6633, 6634 and 7032) taken in 2006.
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