Table 3.
Orbital parameters of the Vela X-1/HD 77581 system as derived by a selection of authors over the years.
| Reference | Time | Phase zero | Orbital period | Semimajor axis | Eccentricity | Longitude of |
|---|---|---|---|---|---|---|
| basis | [MJD] | Porb [d] | aX sin i [lt-s] | e | periastron ω | |
| Forman et al. (1973) | Tecl | 41446.04 ± 0.07 | 8.95 ± 0.02 | – | 0.14 ± 0.05 | – |
| Hutchings (1974) (H74) | Tphot | 41593.40 ± 0.56 | 8.966 ± 0.001 | – | – | – |
| Rappaport et al. (1976) | Tecl | 42611.501 ± 0.12 | (H74) | 111.4 ± 3.3 | 0.126 ± 0.041 | 146 ± 23 |
| Ögelman et al. (1977) (Ö77) | Tecl | 42446.03 ± 0.06 | 8.9643 ± 0.0005 | 113.0 ± 4.0 | – | 162 ± 25 |
| van Paradijs et al. (1977a) | – | – | 8.9681 ± 0.0016 | – | 0.136 ± 0.046 | – |
| Watson & Griffiths (1977) | Tecl | 42620.30 ± 0.05 | 8.9640 ± 0.0005 | – | – | – |
| Rappaport et al. (1980) | Tperi | 42822.90 ± 0.13 | 8.9649 ± 0.0002 | 113.0 ± 0.8 | 0.092 ± 0.005 | 154 ± 5 |
| Nagase et al. (1983) | Tecl | 41446.02 ± 0.05 | 8.9640 ± 0.0006 | – | – | – |
| Nagase et al. (1984a) | Tperi | 45329.05 ± 0.06 | 8.9642 ± 0.0006 | 114.10 ± 0.50 | 0.080 ± 0.006 | 157.3 ± 2.1 |
| van der Klis & Bonnet-Bidaud (1984) | Tπ/2 | 42727.750 ± 0.024 | (Ö77) | (Ö77) | 0.116 ± 0.022 | 166 ± 7 |
| – ditto – | Tπ/2 | 42966.628 ± 0.019 | (Ö77) | 113.4 ± 1.7 | 0.085 ± 0.022 | 121 ± 16 |
| – ditto – | Tπ/2 | 44170.937 ± 0.021 | (Ö77) | 113.20 ± 1.4 | 0.102 ± 0.024 | 177 ± 15 |
| Boynton et al. (1986) | Tπ/2 | 43821.3604 ± 0.0056 | 8.96443 ± 0.00022 | 112.70 ± 0.47 | 0.0881 ± 0.0036 | 152.8 ± 2.2 |
| Deeter et al. (1987b) | Tπ/2 | 43955.8261 ± 0.0048 | 8.964353 ± 0.000063 | 112.66 ± 0.41 | 0.0896 ± 0.0031 | 152.8 ± 1.8 |
| Deeter et al. (1987a) | Tπ/2 | 44278.5466 ± 0.0037 | 8.964416 ± 0.000049 | 112.98 ± 0.35 | 0.0885 ± 0.0025 | 150.6 ± 1.8 |
| Bildsten et al. (1997) (B97) | Tπ/2 | 48895.2186 ± 0.0012 | 8.964368 ± 0.00004 | 113.89 ± 0.13 | 0.0898 ± 0.0012 | 152.59 ± 0.92 |
| Kreykenbohm et al. (2008) | Tπ/2 | 52974.001 ± 0.012 | 8.964357 ± 0.000029 | (B97) | (B97) | (B97) |
| – ditto – | Tecl | 52974.227 ± 0.007 | Same as above | |||
| Falanga et al. (2015) | Tπ/2 | 42611.349 ± 0.013 | 8.964427 ± 0.000012 | (B97) | (B97) | (B97) |
| – ditto – | Tecl | 42611.1693 ± 0.013 | 8.9644061 ± 0.0000064 |
Notes. We also indicate where subsequent publications directly reused previous results. Different definitions of the time of phase zero have been used over time: Mid-eclipse time (Tecl) or time of mean longitude equal to π/2 (Tπ/2 ≡ T90) are the most common, but some authors also use periastron time (Tperi or τ) or specific zero times (Hutchings 1974).
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