Astronomy:HD 86320

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Short description: Binary star in the constellation Chamaeleon
HD 86320
Observation data
Epoch J2000.0   Equinox (celestial coordinates)
Constellation Chamaeleon[1]
Right ascension  09h 51m 00.81459s[2]
Declination −80° 03′ 39.7714″[2]
Apparent magnitude (V) 6.49[3] (6.69 + 8.62)[4]
Characteristics
Spectral type B8 IV[5]
U−B color index −0.23[6]
B−V color index +0.06[6]
Astrometry
Radial velocity (Rv)12.1±2.1[7] km/s
Proper motion (μ) RA: −7.109[2] mas/yr
Dec.: +8.963[2] mas/yr
Parallax (π)3.9544 ± 0.1015[2] mas
Distance820 ± 20 ly
(253 ± 6 pc)
Absolute magnitude (MV)−0.54[1]
Orbit[8]
Period (P)63.52±5.680 yr
Semi-major axis (a)0.1583±0.0057″
Eccentricity (e)0.50 (fixed)
Inclination (i)34.5±7.0°
Longitude of the node (Ω)142.3±15.8°
Periastron epoch (T)2,457,108.1±451.1 JD
Argument of periastron (ω)
(secondary)		135.2±20.9°
Details
A
Mass3.069+1.059−1.104[9] M☉
Radius4.95±0.25[10] R☉
Luminosity332.2+16.8−15.5[2] L☉
Surface gravity (log g)3.49[11] cgs
Temperature10,257±1[9] K
Metallicity [Fe/H]0.00[11] dex
Rotational velocity (v sin i)>250[12] km/s
Age346[13] Myr
B
Mass1.6[8] M☉
Other designations
CPD−79°457, FK5 2791, GC 13624, HD 86320, HIP 48320, SAO 256666, WDS J09510-8004AB[14]
Database references
SIMBADdata

HD 86320 (HIP 48320; 18 G. Chamaeleontis) is a binary star located in the southern circumpolar constellation Chamaeleon. With a combined apparent magnitude of 6.49,[3] the system is a challenge to view with the naked eye, even under ideal conditions. When resolved, the apparent magnitudes of the components are 6.69 and 8.62 respectively.[4] The system is located relatively far at a distance of 820 light years based on Gaia DR3 parallax measurements,[2] and it is drifting away from the Solar System with a heliocentric radial velocity of roughly 12.1 km/s.[7] It has an absolute magnitude of −0.54.[1]

The binary natue of this system was first observed in a 1991 Hipparcos multiple star survey.[4] A preliminary orbit was calculated for the system in 2016. In this solution, the stars take 63.52 years to circle each other in an eccentric orbit at a separation of 0.1583".[8] As of 2021, the 8th magnitude companion is located roughly 0.1" away at a position angle of 344°.[4]

The system has a combined spectral classification of B8 IV,[5] indicating that it is a slightly evolved B-type subgiant that is beginning to cease hydrogen fusion at its core. The primary has 3.07 times the mass of the Sun[9] and 4.95 times the radius of the Sun.[10] It radiates 332.2 times the luminosity of the Sun[2] from its photosphere at an effective temperature of 10,257 K,[9] giving it a bluish-white hue when viewed in the night sky. HD 86320 A has a solar metallicity,[11] and it is estimated to be 346 million years old.[13] It spins rapidly with a projected rotational velocity that is greater than 250 km/s.[12] The companion has 1.6 times the mass of the Sun based on the orbital solution.[8]

References

  1. ↑ 1.0 1.1 1.2 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A  XHIP record for this object at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  3. ↑ 3.0 3.1 Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P. et al. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics 355: L27–L30. ISSN 0004-6361. Bibcode: 2000A&A...355L..27H. 
  4. ↑ 4.0 4.1 4.2 4.3 Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (December 2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal 122 (6): 3466–3471. doi:10.1086/323920. ISSN 0004-6256. Bibcode: 2001AJ....122.3466M. 
  5. ↑ 5.0 5.1 Houk, N.; Cowley, A. P. (1975). University of Michigan Catalogue of two-dimensional spectral types for the HD stars: Declinations −90° to −53°. 1. Bibcode: 1975mcts.book.....H. 
  6. ↑ 6.0 6.1 Moreno, H.; Carrasco, G. (July 1986). "UBVRI photometry of FK4 and FK4 supplement stars.". Astronomy and Astrophysics Supplement Series 65: 33–39. ISSN 0365-0138. Bibcode: 1986A&AS...65...33M. 
  7. ↑ 7.0 7.1 Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35,495 Hipparcos stars in a common system". Astronomy Letters 32 (11): 759–771. doi:10.1134/S1063773706110065. ISSN 1063-7737. Bibcode: 2006AstL...32..759G. 
  8. ↑ 8.0 8.1 8.2 8.3 Tokovinin, Andrei (2016). "New Orbits Based on Speckle Interferometry at SOAR". The Astronomical Journal 152 (5): 138. doi:10.3847/0004-6256/152/5/138. Bibcode: 2016AJ....152..138T. 
  9. ↑ 9.0 9.1 9.2 9.3 Quintana, Alexis L; Wright, Nicholas J; García, Juan Martínez (March 17, 2025). "A census of OB stars within 1 kpc and the star formation and core collapse supernova rates of the Milky Way". Monthly Notices of the Royal Astronomical Society 538 (3): 1367–1383. doi:10.1093/mnras/staf083. ISSN 0035-8711. Bibcode: 2025MNRAS.538.1367Q. 
  10. ↑ 10.0 10.1 Kervella, P.; Thévenin, F.; Di Folco, E.; Ségransan, D. (April 8, 2004). "The angular sizes of dwarf stars and subgiants: Surface brightness relations calibrated by interferometry". Astronomy & Astrophysics 426 (1): 297–307. doi:10.1051/0004-6361:20035930. ISSN 0004-6361. Bibcode: 2004A&A...426..297K. 
  11. ↑ 11.0 11.1 11.2 Anders, F. et al. (February 2022). "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia EDR3 stars brighter than G = 18.5". Astronomy & Astrophysics 658: A91. doi:10.1051/0004-6361/202142369. ISSN 0004-6361. Bibcode: 2022A&A...658A..91A. 
  12. ↑ 12.0 12.1 Andersen, J.; Nordstrom, B. (1983). "Radial velocities of bright southern stars. I - 139 B-type HR and FK stars". Astronomy and Astrophysics Supplement Series 52: 471–482. Bibcode: 1983A&AS...52..471A. 
  13. ↑ 13.0 13.1 Gontcharov, G. A. (2012). "Dependence of kinematics on the age of stars in the solar neighborhood". Astronomy Letters 38 (12): 771. doi:10.1134/S1063773712120031. Bibcode: 2012AstL...38..771G. 
  14. ↑ "HD 86320". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+86320. 
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