24 Comae Berenices

24 Comae Berenices is a triple star system in the northern constellation of Coma Berenices. It is visible to the naked eye, with the brightest component being an orange-hued star with an apparent visual magnitude of 5.03.[2] The system is located at a distance of approximately 269 light years from the Sun based on parallax, and is drifting further away with radial velocities of 3–5 km/s.[2]

24 Comae Berenices

Map showing location of 24 Comae Berenices
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Coma Berenices
A
Right ascension	12^h 35^m 07.76130^s[1]
Declination	+18° 22′ 37.4133″[1]
Apparent magnitude (V)	5.03[2]
B
Right ascension	12^h 35^m 06.34558^s[1]
Declination	+18° 22′ 37.5320″[1]
Apparent magnitude (V)	6.57[2]
Characteristics
A
Spectral type	K0II-III[3]
B−V color index	1.152±0.018[2]
B
Evolutionary stage	A9V[3]
B−V color index	0.265±0.015[2]
Astrometry
A
Radial velocity (Rv)	+3.03±0.10[2] km/s
Proper motion (μ)	RA: −3.719[1] mas/yr Dec.: +23.106[1] mas/yr
Parallax (π)	8.5745 ± 0.1996[1] mas
Distance	380 ± 9 ly (117 ± 3 pc)
Absolute magnitude (MV)	0.30[4]
B
Radial velocity (Rv)	+4.90±0.50[2] km/s
Proper motion (μ)	RA: −2.320[1] mas/yr Dec.: +21.236[1] mas/yr
Parallax (π)	8.8346 ± 0.0695[1] mas
Distance	369 ± 3 ly (113.2 ± 0.9 pc)
Orbit[5]
Primary	Ba
Companion	Bb
Period (P)	7.3361±0.0005 d
Semi-major axis (a)	≥ 0.04479 ± 0.00080 AU
Eccentricity (e)	0.26±0.01
Periastron epoch (T)	2,444,593.29±0.04 JD
Argument of periastron (ω) (secondary)	300±3°
Semi-amplitude (K1) (primary)	68.7±1.0 km/s
Semi-amplitude (K2) (secondary)	80.6±1.2 km/s
Details
A
Mass	4.40[6] M☉
Radius	19.95+0.69 −2.58[1] R☉
Luminosity	173.3±4.6[1] L☉
Surface gravity (log g)	2.50[4] cgs
Temperature	4,688+337 −79[1] K
Metallicity [Fe/H]	−0.09[7] dex
B
Mass	1.78/1.52[6] M☉
Radius	2.91+0.17 −0.13[1] R☉
Luminosity	23.9±0.2[1] L☉
Temperature	7,476+176 −204[1] K
Rotational velocity (v sin i)	< 20[8] km/s
Other designations
24 Com, BD+19°2584, FK5 473, WDS 02338-2814
A: NSV 5748, GC 17147, HD 109511, HIP 61418, HR 4792, SAO 100160[9]
B: GC 17146, HD 109510, HIP 61415, HR 4791, SAO 100159[10]
Database references
SIMBAD	A
	B

This system can be resolved in a telescope as a pair of stars with an angular separation of 20.2″ along a position angle of 272°, as of 2018.[11] They share a common motion through space and thus appear to be physically associated,[5] with a wide projected separation of 1,400 AU or greater.[12] If they are bound in an orbit, the estimated period is approximately 28,000 years.[6]

The brighter member of this system is an aging giant or bright giant star with a stellar classification of K0II-III.[3] It has exhausted the supply of hydrogen at its core and expanded to 20[1] times the girth of the Sun. This is a suspected variable that has been recorded ranging in brightness from magnitude 4.98 down to 5.06.[13] The star is radiating 173[1] times the luminosity of the Sun from its swollen photosphere at an effective temperature of 4,688 K.[1]

The fainter component at magnitude 6.57[2] is a double-lined spectroscopic binary with an orbital period of 7.33 days and an eccentricity of 0.26.[5] The primary member of this pair is an A-type main-sequence star with a stellar classification of A9V.[3] It is a metallic-lined Am star[14] with 2.9 times the radius of the Sun. The star is radiating 24 times the Sun's luminosity from its photosphere at an effective temperature of 7,476 K.[1] It has a relatively low projected rotational velocity of under 20 km/s, and it is suspected the rotations of this binary system may be synchronized.[8] The system is a source for X-ray emission, which is most likely coming from the secondary.[15]

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.
   • Component A
   • Component B
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.
3. Yoss, K. M.; Griffin, R. F. (September 1997), "Radial Velocities and DDO, BV Photometry of Henry Draper G5-M Stars Near the North Galactic Pole", Journal of Astrophysics and Astronomy, 18: 161, Bibcode:1997JApA...18..161Y, doi:10.1007/BF02714877.
4. McWilliam, Andrew (1990), "High-Resolution Spectroscopic Survey of 671 GK Giants. I. Stellar Atmosphere Parameters and Abundances", The Astrophysical Journal Supplement Series, 74: 1075, Bibcode:1990ApJS...74.1075M, doi:10.1086/191527.
5. Mayor, M.; Mazeh, T. (January 1987), "The frequency of triple and multiple stellar systems", Astronomy and Astrophysics, 171: 157−177, Bibcode:1987A&A...171..157M.
6. Tokovinin, A. (September 2008), "Comparative statistics and origin of triple and quadruple stars", Monthly Notices of the Royal Astronomical Society, 389 (2): 925–938, arXiv:0806.3263, Bibcode:2008MNRAS.389..925T, doi:10.1111/j.1365-2966.2008.13613.x.
7. Malagnini, M. L.; Morossi, C.; Buzzoni, A.; Chavez, M. (2000), "Observations and Atmospheric Parameters of Super-Metal-rich Candidates", The Publications of the Astronomical Society of the Pacific, 112 (777): 1455, Bibcode:2000PASP..112.1455M, doi:10.1086/317714.
8. Stickland, D. J. (1973), "On the atmospheric abundances of seven Am SB2 systems", Monthly Notices of the Royal Astronomical Society, 161: 193, Bibcode:1973MNRAS.161..193S, doi:10.1093/mnras/161.2.193.
9. "24 Com A". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-10-30.
10. "24 Com B". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-10-30.
11. Mason, B. D.; et al. (2014), The Washington Visual Double Star Catalog, Bibcode:2001AJ....122.3466M, doi:10.1086/323920, retrieved 2015-07-22.
12. Abt, Helmut A. (August 1988), "Maximum Separations among Cataloged Binaries", Astrophysical Journal, 331: 922, Bibcode:1988ApJ...331..922A, doi:10.1086/166609.
13. Samus', N. N; Kazarovets, E. V; Durlevich, O. V; Kireeva, N. N; Pastukhova, E. N (2017), "General catalogue of variable stars: Version GCVS 5.1", Astronomy Reports, 61 (1): 80, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085.
14. Chen, P. S.; et al. (2017), "A New Photometric Study of Ap and Am Stars in the Infrared", The Astronomical Journal, 153 (5): 218, Bibcode:2017AJ....153..218C, doi:10.3847/1538-3881/aa679a.
15. Schröder, C.; Schmitt, J. H. M. M. (November 2007), "X-ray emission from A-type stars", Astronomy and Astrophysics, 475 (2): 677–684, Bibcode:2007A&A...475..677S, doi:10.1051/0004-6361:20077429.