HD 44780 is a binary star system in the northern constellation of Gemini, located about 3° north of Mu Geminorum.[1][7] The pair have a combined apparent visual magnitude of 6.35,[3] which is near the lower limit of visibility to the naked eye. Although it is above magnitude 6.5, it was not included in the Bright Star Catalogue;[1] the designation HD 44780 comes from the Henry Draper catalogue. Based upon parallax measurements, the system is located at a distance of approximately 960 light years from the Sun. It is drifting further away with a radial velocity of +17 km/s.[3]
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Gemini[1] |
| Right ascension | 06h 24m 43.74735s[2] |
| Declination | +25° 02′ 55.3981″[2] |
| Apparent magnitude (V) | 6.35[3] |
| Characteristics | |
| Spectral type | K2 III[4] (K2–K3 + K0–K1)[5] |
| B−V color index | +1.210±0.015[3] |
| Astrometry | |
| Radial velocity (Rv) | +17.2±0.3[3] km/s |
| Proper motion (μ) | RA: +2.459[2] mas/yr Dec.: −1.895[2] mas/yr |
| Parallax (π) | 3.4049 ± 0.1139 mas[2] |
| Distance | 960 ± 30 ly (294 ± 10 pc) |
| Absolute magnitude (MV) | −0.53[3] |
| Orbit[1] | |
| Period (P) | 577.5±0.5 d |
| Semi-major axis (a) | 4.16±1.28 mas[5] |
| Eccentricity (e) | 0.240±0.006 |
| Inclination (i) | 109±12[5]° |
| Periastron epoch (T) | 43,625.5±2.8 MJD |
| Argument of periastron (ω) (secondary) | 85.8±1.9° |
| Semi-amplitude (K1) (primary) | 22.06±0.15 km/s |
| Semi-amplitude (K2) (secondary) | 22.66±0.32 km/s |
| Details | |
| A | |
| Mass | 3.10±0.65[5] M☉ |
| Luminosity | 248.32[3] L☉ |
| Age | 400[5] Myr |
| B | |
| Mass | 3.02±0.64[5] M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
The variable velocity of this system was first noted during a study at Mount Wilson observatory in 1952.[1] It is a double-lined spectroscopic binary[5] system with an orbital period of 1.581 years and an eccentricity of 0.24. Both components are similar, aging giant stars, a relatively rare combination.[1] Their combined spectrum matches a stellar classification of K2 III;[4] with the secondary being a slightly earlier type than the primary. They have an age of about 400 million years, with masses 3.10 and 3.02 times that of the Sun.[5]
References
edit- ^ a b c d e f Griffin, R. F. (April 1986), "The spectroscopic orbits of HD 44780 and 65 Geminorum", Journal of the Royal Astronomical Society of Canada, 80: 91–108, Bibcode:1986JRASC..80...91G.
- ^ a b c d e 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 g 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 Heard, John Frederick (1956), "The radial velocities, spectral classes and photographic magnitudes of 1041 late-type stars", Publications of the David Dunlap Observatory, 2 (4), University of Toronto, Toronto, Canada: University of Toronto Press: 107–143, Bibcode:1956PDDO....2..107H.
- ^ a b c d e f g h Pourbaix, D.; Boffin, H. M. J. (February 2003), "Reprocessing the Hipparcos Intermediate Astrometric Data of spectroscopic binaries. II. Systems with a giant component", Astronomy and Astrophysics, 398 (3): 1163–1177, arXiv:astro-ph/0211483, Bibcode:2003A&A...398.1163P, doi:10.1051/0004-6361:20021736, S2CID 12361870.
- ^ "HD 44780". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2011-11-30.
- ^ HD 044780, VizieR, retrieved 2011-11-30.