Table 1.
Accreting NSs analysed in this study, along with their respective net exposure times for the SPI data, and the highest 3σ upper limits in the ranges 1−2.2 MeV (for a redshifted 2.2 MeV line) and 200–800 keV (for a 511 keV line), assuming different values of FWHM.
| Source name | Net exposure | Lx(a) | Distance (b) | 3σ u.l. 2.2 MeV line | 3σ u.l. 511 keV line | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| (ks) | (erg s−1) | (kpc) | (10−4 ph cm−2 s−1) | (10−3 ph cm−2 s−1) | ||||||||
| FWHM: | 10 | 20 | 40 | 100 | FWHM: | 10 | 20 | 40 | ||||
| (keV) | (keV) | |||||||||||
| A 0535+26 | 1631 | 3.1 × 1036 | 1.8 ± 0.1 | 7.5 | 9.5 | 11 | 16 | 1.5 | 1.1 | 1.6 | ||
| GX 304−1 | 381 | 2.6 × 1036 | 1.86 ± 0.04 | 18 | 15 | 22 | 36 | 2.5 | 2.5 | 2.8 | ||
| Vela X-1 | 5345 | 2.8 × 1036 | 1.96 ± 0.06 | 2.4 | 3.0 | 3.8 | 7.2 | 0.7 | 0.7 | 0.8 | ||
| X Persei | 3050 | 6 × 1034 | 0.60 ± 0.02 | 4.4 | 5.2 | 8.2 | 9.8 | 0.4 | 0.5 | 0.8 | ||
| Sco X-1 | 4495 | 1.6 × 1038 | 2.1 ± 0.1 | 2.8 | 3.6 | 5.3 | 9.6 | 0.3 | 0.3 | 0.4 | ||
Notes. (a)X-ray luminosity, in the energy range 0.1–100 keV.
(b)Distances from Bailer-Jones et al. (2021).
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