56 Aquarii

56 Aquarii, abbreviated 56 Aqr, is a star in the constellation of Aquarius. 56 Aquarii is its Flamsteed designation. It is a sixth magnitude star, having an apparent visual magnitude of 6.36,^[2] and thus is a challenge to view with the naked eye. Based upon an annual parallax shift of 5.07 mas,^[1] it is located around 643 light years from the Earth. At that distance, the visual magnitude is diminished by an extinction of 0.12 due to interstellar dust.^[7] The star is moving closer with a heliocentric radial velocity of −28 km/s.^[5] It is a candidate runaway star showing a transverse peculiar velocity of 213.87 km/s.^[9]

56 Aquarii

Observation data Epoch J2000      Equinox J2000
Constellation	Aquarius
Right ascension	22h 30m 17.35070s[1]
Declination	−14° 35′ 08.6467″[1]
Apparent magnitude (V)	6.36[2]
Characteristics
Evolutionary stage	main sequence[3]
Spectral type	B8 II[4]
B−V color index	−0.047±0.007[2]
Astrometry
Radial velocity (Rv)	−27.6±1.2[5] km/s
Proper motion (μ)	RA: +35.275[1] mas/yr Dec.: −33.214[1] mas/yr
Parallax (π)	5.0725 ± 0.0758 mas[1]
Distance	643 ± 10 ly (197 ± 3 pc)
Absolute magnitude (MV)	−0.05[2]
Details
Mass	3.37±0.14[3] M☉
Radius	2.8[6] R☉
Luminosity	184.5+43.5 −35.2[3] L☉
Temperature	11,912+83 −82[3] K
Rotational velocity (v sin i)	23[3] km/s
Age	292[7] Myr
Other designations
CD−15° 6231, FK5 5985, GC 31428, HD 213236, HIP 111086, HR 8567, SAO 165127[8]
Database references
SIMBAD	data

Houk and Smith-Moore (1978) gave this star a stellar classification of B8 II,^[4] matching a B-type bright giant. In contrast, Cowley et al. (1969) found a class of B8 Vs,^[10] corresponding to a B-type main-sequence star with narrow ("sharp") absorption lines due to a relatively low projected rotation. Zorec and Royer (2012) modeled it as a dwarf star that is 67% of the way through its main sequence lifespan. It is a chemically peculiar mercury-manganese star, showing abnormally strong absorption lines of mercury and magnesium with weak lines of helium.^[11] The star has 3.4^[3] times the mass of the Sun and about 2.8^[6] times the Sun's radius. It is radiating 185^[3] times the Sun's luminosity from its photosphere at an effective temperature of 11,912 K.^[3]

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.
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. Zorec, J.; Royer, F. (2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691, S2CID 55586789.
4. Houk, Nancy; Smith-Moore, M. (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H.
5. Gontcharov, G. A. (2006), "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system", Astronomy Letters, 32 (11): 759–771, arXiv:1606.08053, Bibcode:2006AstL...32..759G, doi:10.1134/S1063773706110065, ISSN 1063-7737, S2CID 119231169.
6. Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics", Astronomy and Astrophysics, 367 (2): 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451, S2CID 425754.
7. Gontcharov, G. A. (November 2012), "Spatial distribution and kinematics of OB stars", Astronomy Letters, 38 (11): 694–706, arXiv:1606.09028, Bibcode:2012AstL...38..694G, doi:10.1134/S1063773712110035, S2CID 119108982.
8. "56 Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 24, 2018.
9. Mdzinarishvili, T. G.; Chargeishvili, K. B. (February 2005), "New runaway OB stars with HIPPARCOS", Astronomy and Astrophysics, 431 (2): L1–L4, Bibcode:2005A&A...431L...1M, doi:10.1051/0004-6361:200400134.
10. Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819.
11. Saffe, C.; et al. (October 2011), "Upper Main Sequence Stars with Anomalous Abundances. The HgMn stars HR 3273, HR 8118 HR 8567 and HR 8937", Revista Mexicana de Astronomía y Astrofísica, 47: 219–234, Bibcode:2011RMxAA..47..219S.