112 Herculis

112 Herculis is a binary star system in the northern constellation of Hercules. It is dimly visible to the naked eye with a combined apparent visual magnitude of 5.43.^[2] The secondary component is about two magnitudes fainter than the primary star.^[4] The distance to this system is approximately 415 light years based on parallax measurements.^[1] It is drifting closer to the Sun with a radial velocity of −20 km/s.^[5]

112 Herculis

Location of 112 Herculis (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Hercules
Right ascension	18h 52m 16.428s[1]
Declination	+21° 25′ 30.51″[1]
Apparent magnitude (V)	5.43[2]
Characteristics
Spectral type	B9p Hg[3] (B6.5V + A2V)[4]
B−V color index	−0.068±0.008[2]
Astrometry
Radial velocity (Rv)	−19.8±0.9[5] km/s
Proper motion (μ)	RA: −7.526 mas/yr[1] Dec.: −10.231 mas/yr[1]
Parallax (π)	7.8558 ± 0.0728 mas[1]
Distance	415 ± 4 ly (127 ± 1 pc)
Absolute magnitude (MV)	−0.04[2]
Orbit[6]
Period (P)	6.36246±0.00002 d
Eccentricity (e)	0.11±0.03
Periastron epoch (T)	2,452,540.11±0.03 JD
Argument of periastron (ω) (secondary)	198±2°
Semi-amplitude (K1) (primary)	17.0±0.6 km/s
Semi-amplitude (K2) (secondary)	35±2 km/s
Details
Primary
Mass	~5.0[4] M☉
Radius	2.888[7] R☉
Luminosity	203+4 −3[7] L☉
Surface gravity (log g)	4.1[8] cgs
Temperature	12,853±89[7] K
Rotation	12.419 d[7]
Rotational velocity (v sin i)	20[9] km/s
Secondary
Mass	~2.5[4] M☉
Surface gravity (log g)	4.2[8] cgs
Other designations
112 Her, BD+21°3582, GC 25895, HD 174933, HIP 92614, HR 7113, SAO 86521, WDS J18523+2126[10]
Database references
SIMBAD	data

The binary character of this system was discovered by W. F. Meyer in 1926. By measuring the variation in velocity of the primary component, he determined an orbital period of 6.3624 days.^[11] K. Osawa in 1959 found a stellar classification of A4 III for the pair.^[12] W. P. Bidelman observed that the primary has unusually strong lines of ionized phosphorus, and it was assigned to the class of peculiar manganese stars by W. L. W. Sargent and L. Searle in 1962, with a resulting spectral type of B9.^[13] No evidence was found for a strong magnetic field by P. S. Conti in 1970.^[14]

A light curve for 112 Herculis, plotted from TESS data^[15]

In 1969, A. Cowley and associates found a stellar class of B9p Hg for this system, indicating a peculiar star with an abundance anomaly of mercury.^[3] C. E. Seligman in 1970 determined a mass ratio of 2.06±0.17 for the pair, which supported individual stellar classes of B7V and A3V for main sequence components. The sharpness of the spectral lines suggested that at least the primary is rotating synchronously with its orbital period.^[16] A more detailed analysis by Seligman and L. H. Allen later in 1970 refined the classifications to B6.5V and A2V. The elemental abundances for both stars appeared similar, although the secondary abundances were more uncertain.^[4]

In 1975, the primary was classified as a mercury-manganese star by C. R. Cowley and G. C. L. Aikman.^[17] T. A. Ryabchikova and associates in 1996 refined the mass ratio to 1.98±0.03. The primary showed significant deficiencies of helium and mercury, but a large overabundance of iron. The secondary component displayed abundances similar to an Am star.^[8] This is a double-lined spectroscopic binary system with an orbital period of 6.36246 days and an eccentricity (ovalness) of 0.11.^[6] As of 2021, measurements by the TESS space telescope show a rotation period of 12.4 days for the primary, suggesting that it is not rotating synchronously with its orbit.^[7] Some variability in flux was recorded by TESS, but this is due to orbital motion – the stars themselves do not appear to be variable.^[18]

References

1. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 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. 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.
4. Seligman, Courtney E.; Aller, L. H. (December 1970), "A Model Atmosphere Analysis of the Binary 112 Herculis", Astrophysics and Space Science, 9 (3): 461–481, Bibcode:1970Ap&SS...9..461S, doi:10.1007/BF00649584, S2CID 122876855.
5. Wilson, Ralph Elmer (1953), "General catalogue of stellar radial velocities", Washington, Carnegie Institution of Washington: 0, Bibcode:1953GCRV..C......0W.
6. Catanzaro, G.; Leto, P. (March 2004), "Orbital solutions for SB2 systems with a HgMn component", Astronomy and Astrophysics, 416 (2): 661–668, Bibcode:2004A&A...416..661C, doi:10.1051/0004-6361:20034445, S2CID 62892090.
7. Kochukhov, O.; et al. (October 2021), "TESS survey of rotational and pulsational variability of mercury-manganese stars", Monthly Notices of the Royal Astronomical Society, 506 (4): 5328–5344, arXiv:2107.09096, Bibcode:2021MNRAS.506.5328K, doi:10.1093/mnras/stab2107.
8. Ryabchikova, T. A.; et al. (December 1996), "Elemental abundance analyses with DAO spectrograms - XIV. The double-lined spectroscopic binary 112 Herculis", Monthly Notices of the Royal Astronomical Society, 283 (4): 1115–1132, Bibcode:1996MNRAS.283.1115R, doi:10.1093/mnras/283.4.1115.
9. Abt, Helmut A.; et al. (July 2002), "Rotational Velocities of B Stars", The Astrophysical Journal, 573 (1): 359–365, Bibcode:2002ApJ...573..359A, doi:10.1086/340590.
10. "112 Her". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2022-10-24.
11. Meyer, William Ferdinand (1926), "The orbit of the spectroscopic binary 112 Herculis", Lick Observatory Bulletin, 381, Berkeley: University of California Press: 165–167, Bibcode:1926LicOB..12..165M, doi:10.5479/ADS/bib/1926LicOB.12.165M.
12. Osawa, Kiyoteru (July 1959), "Spectral Classification of 533 B8-A2 Stars and the Mean Absolute Magnitude of A0 V Stars", Astrophysical Journal, 130: 159, Bibcode:1959ApJ...130..159O, doi:10.1086/146706.
13. Sargent, Wallace L. W.; Searle, Leonard (September 1962), "Studies of the Peculiar A Stars. I. The Oxygen-Abundance Anomaly", Astrophysical Journal, 136: 408, Bibcode:1962ApJ...136..408S, doi:10.1086/147393.
14. Conti, Peter S. (June 1970), "Zeeman Measures of Four Double-Lined Peculiar A Stars", Astrophysical Journal, 160: 1077, Bibcode:1970ApJ...160.1077C, doi:10.1086/150495.
15. MAST: Barbara A. Mikulski Archive for Space Telescopes, Space Telescope Science Institute, retrieved 27 October 2022.
16. Seligman, Courtney E. (February 1970), "A Mass Ratio for 112 Herculis", Publications of the Astronomical Society of the Pacific, 82 (484): 128, Bibcode:1970PASP...82..128S, doi:10.1086/128894, S2CID 121129664.
17. Cowley, C. R.; Aikman, G. C. L. (August 1975), "A study of the lambda 3984 feature in the mercury-manganese stars", Publications of the Astronomical Society of the Pacific, 87: 513–521, Bibcode:1975PASP...87..513C, doi:10.1086/129801, S2CID 121306556.
18. Monier, Richard (October 2022), "The Behavior of HgMn Stars in the Far UV—Paper 16: HD 174933", Research Notes of the AAS, 6 (10): 218, Bibcode:2022RNAAS...6..218M, doi:10.3847/2515-5172/ac9afe, S2CID 253018177.