HD 5788 and HD 5789
HD 5789 and HD 5788 is a pair of stars comprising a binary star system in the northern constellation of Andromeda. Located approximately 151 parsecs (490 ly) away, the primary is a hot, massive blue star with an apparent magnitude of 6.06 while the secondary is slightly smaller and cooler, with an apparent magnitude of 6.76. Both stars are main-sequence stars, meaning that they are currently fusing hydrogen into helium in their cores. As of 2016, the pair had an angular separation of 7.90″ along a position angle of 195°. While both have a similar proper motion and parallax, there's still no proof that the pair is gravitationally bound.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Andromeda |
| HD 5789 | |
| Right ascension | 01h 00m 03.55767s |
| Declination | +44° 42′ 47.6898″ |
| Apparent magnitude (V) | 6.06 |
| HD 5788 | |
| Right ascension | 01h 00m 03.38277s |
| Declination | +44° 42′ 40.0515″ |
| Apparent magnitude (V) | 6.763 |
| Characteristics | |
| HD 5789 | |
| Spectral type | B9.5Vnn (λ Boo) |
| B−V color index | −0.031 |
| HD 5788 | |
| Spectral type | A2 Vn |
| B−V color index | −0.010 |
| Astrometry | |
| Radial velocity (Rv) | +4.4±3.3 km/s |
| Proper motion (μ) | RA: +13.85 mas/yr Dec.: −23.83 mas/yr |
| Parallax (π) | 6.6432 ± 0.0809 mas |
| Distance | 491 ± 6 ly (151 ± 2 pc) |
| Proper motion (μ) | RA: +11.582 mas/yr Dec.: −24.369 mas/yr |
| Parallax (π) | 6.5625 ± 0.0688 mas |
| Distance | 497 ± 5 ly (152 ± 2 pc) |
| Details | |
| HD 5789 | |
| Mass | 2.74±0.12 M☉ |
| Luminosity | 85.6+19.2 −15.6 L☉ |
| Temperature | 9,977 K |
| Rotational velocity (v sin i) | 249 km/s |
| HD 5788 | |
| Mass | 2.67±0.12 M☉ |
| Luminosity | 73.3+18.4 −14.7 L☉ |
| Temperature | 9,840 K |
| Rotational velocity (v sin i) | 270 km/s |
| Other designations | |
| HD 5789: HR 283, SAO 36833 | |
| HD 5788: HR 282, SAO 36832 | |
| Database references | |
| HD 5789 | |
| SIMBAD | data |
| HD 5788 | |
| SIMBAD | data |
The primary component is HD 5789, a B-type main-sequence star with a stellar classification of B9.5Vnn (λ Boo), where the 'n' indicates "nebulous" lines due to rapid rotation. Abt and Morrell (1995) listed it as a Lambda Boötis star, although this is disputed. It has 2.7 times the mass of the Sun and is spinning rapidly with a projected rotational velocity of 249 km/s. The star is radiating 86 times the Sun's luminosity from its photosphere at an effective temperature of 9,977 K.
The fainter secondary component is an A-type main-sequence star with a class of A2 Vn. It shows a projected rotational velocity of 270 km/s and has 2.7 times the Sun's mass. The star shines with 73 times the Sun's luminosity at an effective temperature of 9,840 K.