HD 77258 is a binary star system in the southern constellation of Vela. It has the Bayer designation w Velorum, while HD 77258 is the identifier from the Henry Draper Catalogue. The system is visible to the naked eye as a faint point of light with a combined apparent visual magnitude of 4.45.[2] It is located at a distance of approximately 218 light years from the Sun based on parallax.[1] The radial velocity of the system barycenter is poorly constrained, but it appears to be drifting away at a rate of ~7 km/s.[2]
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Vela |
| Right ascension | 09h 00m 05.4104s[1] |
| Declination | −41° 15′ 12.9734″[1] |
| Apparent magnitude (V) | 4.45[2] |
| Characteristics | |
| Spectral type | G8-K1III[3] + A7[4] |
| B−V color index | 0.75±0.02[2] |
| Variable type | Constant[3] |
| Astrometry | |
| Radial velocity (Rv) | −7.4±4.1[2] km/s |
| Proper motion (μ) | RA: −42.227[1] mas/yr Dec.: 50.599[1] mas/yr |
| Parallax (π) | 14.9687 ± 0.2155 mas[1] |
| Distance | 218 ± 3 ly (66.8 ± 1.0 pc) |
| Absolute magnitude (MV) | 0.40[2] |
| Orbit[3] | |
| Period (P) | 74.13715±0.00073 d |
| Semi-major axis (a) | ≥ (2.0057±0.0004)×107 km |
| Eccentricity (e) | 0.00085±0.00019 |
| Periastron epoch (T) | 2453625.5112±0.0017 HJD |
| Argument of periastron (ω) (secondary) | 106±13° |
| Semi-amplitude (K1) (primary) | 19.6744±0.0041 km/s |
| Details | |
| A | |
| Radius | 7.97+0.66 −1.42[1] R☉ |
| Luminosity | 68.769±1.152[1] L☉ |
| Temperature | 5889+607 −232[1] K |
| Metallicity [Fe/H] | 0.72±0.15[5] dex |
| Other designations | |
| Database references | |
| SIMBAD | data |
The radial velocity variation of this system was first reported by H. K. Palmer in 1904. It is a single-lined spectroscopic binary with an orbital period of 74.14 days and an eccentricity (ovalness) of 0.00085, indicating the orbit is essentially circular.[3] The visible component has a stellar classification of G8-K1III,[3] matching a late G-type giant star. This is an evolved star that has exhausted the supply of hydrogen at its core, then cooled and expanded away from the main sequence. In 1975, S. Maladora flagged the spectrum as peculiar.[7]
The level of ultraviolet flux coming from this system suggests the companion is a hot A-type star of class A6.5 or A7.[4] The system is a source of X-ray emission.[8]
References
edit- ^ a b c d e f g h i Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ a b c d e f Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
- ^ a b c d e Hearnshaw, J. B.; et al. (2012). "A study of non-Keplerian velocities in observations of spectroscopic binary stars". Monthly Notices of the Royal Astronomical Society. 427 (1): 298–310. arXiv:1211.5527. Bibcode:2012MNRAS.427..298H. doi:10.1111/j.1365-2966.2012.21802.x.
- ^ a b Parsons, Sidney B.; Ake, Thomas B. (November 1998). "Ultraviolet and Optical Studies of Binaries with Luminous Cool Primaries and Hot Companions. V. The Entire IUE Sample". The Astrophysical Journal Supplement Series. 119 (1): 83–104. Bibcode:1998ApJS..119...83P. doi:10.1086/313152.
- ^ Gáspár, András; et al. (2016). "The Correlation between Metallicity and Debris Disk Mass". The Astrophysical Journal. 826 (2): 171. arXiv:1604.07403. Bibcode:2016ApJ...826..171G. doi:10.3847/0004-637X/826/2/171. S2CID 119241004.
- ^ "HD 77258". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-10-05.
- ^ Malaroda, S. (August 1975). "Study of the F-type stars. I. MK spectral types". Astronomical Journal. 80: 637–641. Bibcode:1975AJ.....80..637M. doi:10.1086/111786.
- ^ Pizzolato, N.; et al. (1998). Donahue, R. A.; Bookbinder, J. A. (eds.). "Evolution of X-ray Activity of 1-3 M_odot Late-Type Stars in Early Post-Main-Sequence Phases". The Tenth Cambridge Workshop on Cool Stars, Stellar Systems and the Sun. ASP Conference Series. 154: 1146. Bibcode:1998ASPC..154.1146P.