HD 88218
Binary star in the constellation Antlia
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HD 88218 (HR 3992) is a binary star in the southern constellation Antlia. The system has a combined apparent magnitude of 6.14,[1] making it faintly visible to the naked eye. HD 88218 is relatively close at a distance of 103 light years[2] but is receding with a heliocentric radial velocity of 36.7 km/s.[5]
| Observation data Epoch J2000.0 Equinox ICRS | |
|---|---|
| Constellation | Antlia[1] |
| Right ascension | 10h 09m 31.7681s[2] |
| Declination | −35° 51′ 24.404″[2] |
| Apparent magnitude (V) | 6.14[1] |
| Characteristics | |
| Evolutionary stage | subgiant[2] |
| Spectral type | G0 V[3] |
| U−B color index | +0.16[4] |
| B−V color index | +0.6[4] |
| Astrometry | |
| Radial velocity (Rv) | 36.7±0.1[5] km/s |
| Proper motion (μ) | RA: −445.632 mas/yr[2] Dec.: +18.774 mas/yr[2] |
| Parallax (π) | 31.5137±0.0307 mas[2] |
| Distance | 103.5 ± 0.1 ly (31.73 ± 0.03 pc) |
| Absolute magnitude (MV) | +3.64[1] |
| Orbit[6] | |
| Period (P) | 268+92 −56 yr |
| Semi-major axis (a) | 51+12 −8 au |
| Eccentricity (e) | 0.611+0.055 −0.098 |
| Inclination (i) | 57.21+0.65 −0.60° |
| Details | |
| A | |
| Mass | 1.268+0.064 −0.063[6] M☉ |
| Radius | 1.66[7] R☉ |
| Luminosity | 2.88[7] L☉ |
| Surface gravity (log g) | 4.03±0.03[8] cgs |
| Temperature | 5,878±14[8] K |
| Metallicity [Fe/H] | −0.14±0.01[8] dex |
| Rotational velocity (v sin i) | 3[9] km/s |
| Age | 6.8+0.49 −0.41[10] Gyr |
| B | |
| Mass | 0.617+0.064 −0.057[6] M☉ |
| Other designations | |
| 49 G. Antliae[11], CD−35°6194, CPD−35°3974, FK5 2816, GJ 379.1, HD 88218, HIP 49769, HR 3992, SAO 201109, WDS J10095-3551AB[12] | |
| Database references | |
| SIMBAD | data |
The visible component has a stellar classification of G0 V, indicating the object's status as a solar analogue. As for the companion, it is probably a K-type star[citation needed] based on a mass of 0.62 M☉.[6] The stars have an orbital period of 270 years (albeit with great uncertainty) a semi-major axis of 50 astronomical units and an eccentricity of 0.61.[6]
Despite the class described above, the primary is starting to evolve off the main sequence at the age of 6.8 billion years, having a low surface gravity[8] and a slightly enlarged radius of 1.66 R☉,[7] with the addition of being chromospherically inactive.[3] Nevertheless, it has 107% the mass of the Sun[13] and radiates at 2.88 times the luminosity of the Sun[7] from its photosphere at an effective temperature of 5,870 K,[8] giving a yellow glow. HD 88218 A has an iron abundance 72% that of the Sun[8] and spins leisurely with a projected rotational velocity of 3 km/s.[9]