Table 4.
Main parameters of the sdO stars Feige 34, BD +37° 1977, BD +37° 442, and HD 49798.
| Parameter | Feige 34 |
BD +37° 1977 |
BD +37° 442 |
HD 49798 |
||||
|---|---|---|---|---|---|---|---|---|
| Value | Reference | Value | Reference | Value | Reference | Value | Reference | |
| log g (cm s−2) | 5.99 | 1 | ≃4.0 | 6 | 4.00 ± 0.25 | 11 | 4.35 | 14 |
| Teff (K) | 62 550 | 1 | 48 000 | 7 | 48 000 | 7 | 46 500 | 14 |
| U | 9.61 | 2 | 8.67 | 8 | 8.57 | 12 | 6.76 | 15 |
| B | 10.91 | 2 | 9.93 | 8 | 9.73 | 12 | 8.02 | 15 |
| V | 11.14 | 2 | 10.17 | 8 | 10.01 | 12 | 8.29 | 15 |
| dGaia (pc) | 226 ± 5 | 3 | 1200 |
3 | 1230 |
3 | 501 |
3 |
| LGaia (L⊙) (a) | 158 | 4 | 4900 | 6 | 9500 | 6 | 8300 | 14 |
| vW (km s−1) | – | – | 2000 | 7 | 2000 | 7 | 1200 | 9 |
| ṀW (M⊙ yr−1) | 10−10 | 5 | 10−8.2 | 7 | 10−8.5 | 7 | 10−9.2 | 9 |
| NH (×1020 cm−2) | 2.2 | 4 | 1 | 9 | 5 | 9 | 5 | 9 |
| kT1 (keV) | 0.30 | 4 | 0.13 | 9 | 0.11 | 9 | 0.11 | 9 |
| kT2 (keV) | 1.10 | 4 | 0.79 | 9 | 0.65 | 9 | 0.57 | 9 |
| kT3 (keV) | – | 4 | – | – | 4 | 9 | ||
| fX (×10−14 erg cm−2 s−1) (b) | 3.4 |
4 | 4.0 |
10 | 3.4 |
13 | 9.2 ± 0.7 | 16 |
| LX (×1030 erg s−1) (c) | 0.20 |
4 | 6.5 |
10 | 5.8 |
13 | 2.6 ± 0.2 | 16 |
| log(LX/Lbol) (d) | –6.48 ± 0.06 | 4 | –6.46 |
10 | –6.80 |
13 | –7.09 ± 0.03 | 16 |
| Element | Abundances (e) | |||||||
| XH | 0.89663 | 1 | 0.0013 | 11 | 0.0013 | 11 | 0.19 | 14 |
| XHe | 0.05774 | 1 | 0.9639 | 11 | 0.9639 | 11 | 0.78 | 14 |
| XC | ≲2.1 × 10−6 | 1 | 0.0250 | 11 | 0.0250 | 11 | 0.0001 | 14 |
| XN | 0.00016 | 1 | 0.0031 | 11 | 0.0031 | 11 | 0.025 | 14 |
| XO | 4.5 × 10−5 | 1 | 0.0053 | 11 | 0.0053 | 11 | 0.0028 | 14 |
| XMg | ≲0.00022 | 1 | – | – | – | – | – | – |
| XSi | 1.6 × 10−5 | 1 | 0.0008 | 11 | 0.0008 | 11 | 0.001 | 11 |
| XP | 5.5 × 10−6 | 1 | – | – | – | – | – | – |
| XS | 7.2 × 10−5 | 1 | – | – | – | – | – | – |
| XCr | ≲0.00023 | 1 | – | – | – | – | – | – |
| XMn | ≲0.00012 | 1 | – | – | – | – | – | – |
| XFe | 0.03946 | 1 | 0.0006 | 7 | 0.0006 | 7 | 0.0011 | 14 |
| XCo | ≲8.3 × 10−5 | 1 | – | – | – | – | – | – |
| XNi | 0.00522 | 1 | – | – | – | – | – | – |
Notes.
The errors on the source X-ray luminosity take into account the errors on both the source flux and distance.
References. 1 – Latour et al. (2018); 2 – Høg et al. (2000); 3 – Bailer-Jones et al. (2018); 4 – This work; 5 – Krtička et al. (2016); 6 – Darius et al. (1979); 7 – Jeffery & Hamann (2010); 8 – Jordi et al. (1991); 9 – Mereghetti & La Palombara (2016); 10 – La Palombara et al. (2015); 11 – Bauer & Husfeld (1995); 12 – Landolt (1973); 13 – Mereghetti et al. (2017); 14 – Hamann (2010); 15 – Landolt & Uomoto (2007); 16 – Mereghetti et al. (2016).
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