56 Persei

56 Persei is at least a triple star^[10] and possibly a quadruple star^[3] system in the northern constellation of Perseus. It is visible to the naked eye as a dim point of light with a combined apparent visual magnitude of 5.77.^[2] The system is located 139 light-years (42.5 pc) distant from the Sun based on parallax,^[1] but is drifting closer with a radial velocity of −32 km/s.^[2]

56 Persei

Observation data Epoch J2000      Equinox J2000
Constellation	Perseus
Right ascension	04h 24m 37.46102s[1]
Declination	+33° 57′ 35.2908″[1]
Apparent magnitude (V)	5.77[2] (5.80 + 15.00[3] + 9.16[4] + 11.30[5])
Characteristics
Spectral type	F4V + DA3.1[3] + F4[6] + ?
B−V color index	0.400±0.019[2]
Astrometry
Radial velocity (Rv)	−31.8±2.9[2] km/s
Proper motion (μ)	RA: +43.818[1] mas/yr Dec.: −90.502[1] mas/yr
Parallax (π)	23.5093 ± 0.0909 mas[1]
Distance	138.7 ± 0.5 ly (42.5 ± 0.2 pc)
Absolute magnitude (MV)	2.73[2]
Details
56 Per Aa
Mass	1.53[7] M☉
Radius	1.97+0.05 −0.11[1] R☉
Luminosity	7.166±0.034[8] L☉
Surface gravity (log g)	4.32±0.14[8] cgs
Temperature	6,629±225[8] K
Metallicity [Fe/H]	−0.11±0.08[9] dex
Age	1.811[8] Gyr
56 Per Ab
Mass	0.90±0.12[10] M☉
Surface gravity (log g)	8.46±0.2[10] cgs
Temperature	16,420±420[10] K
Other designations
56 Per, BD+33° 854, HD 27786, HIP 20591, HR 1379, SAO 57216[11]
Database references
SIMBAD	data

The main component is a binary system^[12] with an orbital period of 47.3 years and a semimajor axis of 17.60 AU. The primary, designated component Aa, is an F-type main-sequence star with a stellar classification of F4V, a star that is currently fusing its core hydrogen.^[7] It is 1.8^[8] billion years old with 1.5^[7] times the mass of the Sun and twice^[1] the Sun's radius. It is radiating 7^[8] times the luminosity of the Sun from its photosphere at an effective temperature of 6,629 K.^[8]

The companion, component Ab, is a hydrogen–rich white dwarf star with a class of DA3.1,^[3] having begun its main sequence life with more mass than the current primary and thus evolved into a compact star more rapidly. It now has 90% of the Sun's mass – much higher than the 0.6 M_☉ for an average white dwarf – and an effective temperature of 16,420 K;^[10] contributing an ultraviolet excess to the system.^[3]

Component B shares a common linear motion through space with the primary, and thus may form a third member of the system. This star has 0.84 times the mass of the Sun and a projected separation of 178.2 AU from the primary.^[7] The Washington Double Star Catalogue has it classified as a double star, with a magnitude 11.30 companion at an angular separation of 0.60″ along a position angle of 292°, as of 2002.^[5]

References

1. 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.
2. 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.
3. Holberg, J. B.; et al. (2013), "Where are all the Sirius-like binary systems?", Monthly Notices of the Royal Astronomical Society, 435 (3): 2077, arXiv:1307.8047, Bibcode:2013MNRAS.435.2077H, doi:10.1093/mnras/stt1433.
4. Fabricius, C.; et al. (2002), "The Tycho double star catalogue", Astronomy and Astrophysics, 384: 180–189, Bibcode:2002A&A...384..180F, doi:10.1051/0004-6361:20011822.
5. Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466, Bibcode:2001AJ....122.3466M, doi:10.1086/323920
6. Cannon, Annie J.; Mayall, Margaret Walton (1949), "The Henry Draper extension. II", Annals of Harvard College Observatory, 112: 1–295, Bibcode:1949AnHar.112....1C.
7. Tokovinin, A.; Kiyaeva, O. (2015), "Eccentricity distribution of wide binaries", Monthly Notices of the Royal Astronomical Society, 456 (2): 2070, arXiv:1512.00278, Bibcode:2016MNRAS.456.2070T, doi:10.1093/mnras/stv2825.
8. David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal, 804 (2): 146, arXiv:1501.03154, Bibcode:2015ApJ...804..146D, doi:10.1088/0004-637X/804/2/146, S2CID 33401607.
9. Gáspár, András; Rieke, George H.; Ballering, Nicholas (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.
10. Landsman, Wayne; et al. (March 1996), "The White-Dwarf Companions of 56 Persei and HR 3643", Publications of the Astronomical Society of the Pacific, 108: 250, arXiv:astro-ph/9512117, Bibcode:1996PASP..108..250L, doi:10.1086/133718, S2CID 14398914.
11. "54 Per". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-07-21.
12. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.