HD 44780

HD 44780
Observation data; Epoch J2000.0 Equinox J2000.0
Constellation	Gemini
Right ascension	06h 24m 43.74735s
Declination	+25° 02′ 55.3981″
Apparent magnitude (V)	6.35
Characteristics
Spectral type	K2 III (K2–K3 + K0–K1)
B−V color index	+1.210±0.015
Astrometry
Radial velocity (Rv)	+17.2±0.3 km/s
Proper motion (μ)	RA: +2.459 mas/yr ; Dec.: −1.895 mas/yr
Parallax (π)	3.4049 ± 0.1139 mas
Distance	960 ± 30 ly ; (294 ± 10 pc)
Absolute magnitude (MV)	−0.53
Orbit
Period (P)	577.5±0.5 d
Semi-major axis (a)	4.16±1.28 mas
Eccentricity (e)	0.240±0.006
Inclination (i)	109±12°
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 M☉
Luminosity	248.32 L☉
Age	400 Myr
B
Mass	3.02±0.64 M☉
Other designations
	BD+25°1255, FK5 2488, GC 8261, HD 44780, HIP 30501, SAO 78331
Database references
SIMBAD	data

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]

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

^ ^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.