V Hydrae
V Hydrae (V Hya) is a carbon star in the constellation Hydra. To date perhaps uniquely in our galaxy it has plasma ejections/eruptions on a grand scale every 8.5 years caused by its near, unseen companion in an 8.5 year orbit, inferred by its ultraviolet excess and periastron passage likely through the outer parts of the star itself.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Hydra |
| Right ascension | 10h 51m 37.25661s |
| Declination | −21° 15′ 00.3245″ |
| Apparent magnitude (V) | 6.0 - 12.3 |
| Characteristics | |
| Spectral type | C6,3e-C7,5e(N6e) |
| B−V color index | +5.43 |
| Variable type | SRa |
| Astrometry | |
| Radial velocity (Rv) | −14.80 km/s |
| Proper motion (μ) | RA: −11.02 ± 1.14 mas/yr Dec.: 2.29 ± 1.16 mas/yr |
| Parallax (π) | 1.44 ± 1.41 mas |
| Distance | approx. 2,000 ly (approx. 700 pc) |
| Absolute magnitude (MV) | −3.5 to +1.8 |
| Orbit | |
| Period (P) | 8.5 yr |
| Eccentricity (e) | ≥0.6 |
| Details | |
| A | |
| Mass | 1.0 M☉ |
| Radius | 420–430 R☉ |
| Luminosity | 7,850 L☉ |
| Surface gravity (log g) | −0.5 cgs |
| Temperature | 2,650 K |
| Rotational velocity (v sin i) | 11 - 14 km/s |
| B | |
| Mass | <1 M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
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