30 Herculis

30 Herculis is a binary star[11] system in the northern constellation of Hercules. It has the Bayer designation g Herculis, while 30 Herculis is the Flamsteed designation. This system is visible to the naked eye as a faint, red-hued point of light with a baseline apparent visual magnitude of 4.83.[2] Based upon a measured parallax of 9.2 mas, it is located around 354 light years away from the Sun. The system is moving further from the Earth with a heliocentric radial velocity of 1.5 km/s.[2]

30 Herculis
Observation data
Epoch J2000      Equinox J2000
Constellation Hercules
Right ascension 16h 28m 38.54859s[1]
Declination +41° 52′ 54.0406″[1]
Apparent magnitude (V) 4.83[2]
Characteristics
Evolutionary stage AGB[3]
Spectral type M6- III[4]
B−V color index 1.289±0.024[2]
Variable type SRb[5]
Astrometry
Radial velocity (Rv)1.49±0.38[2] km/s
Proper motion (μ) RA: +30.16[1] mas/yr
Dec.: −5.14[1] mas/yr
Parallax (π)9.21 ± 0.18[1] mas
Distance354 ± 7 ly
(109 ± 2 pc)
Absolute magnitude (MV)−0.41[6]
Orbit[3]
Period (P)843.7±21.1 d
Eccentricity (e)0.37±0.11
Periastron epoch (T)2,451,918.2±43.9 HJD
Argument of periastron (ω)
(secondary)		246±21°
Semi-amplitude (K1)
(primary)		2.3±0.3 km/s
Details
30 Her A
Mass1.65±0.30[7] M☉
Radius69.71+27.39
−13.20[8] R☉
Luminosity1,408±71[8] L☉
Surface gravity (log g)0.20[9] cgs
Temperature4,235+469
−647[8] K
Metallicity [Fe/H]−0.01[9] dex
Other designations
g Her, 30 Her, BD+42° 2714, FK5 3303, HD 148783, HIP 80704, HR 6146, SAO 46108[10]
Database references
SIMBADdata

This is a single-lined spectroscopic binary with an orbital period of 2.310 years and an eccentricity of 0.37.[3] The visible component is an aging red giant on the asymptotic giant branch[3] with a stellar classification of M6- III.[4] According to Samus et al. (2017), it is a semiregular variable of subtype SRb, which ranges between visual magnitudes 4.3 and 6.3 over 89.2 days.[5][12] It displays cyclical periods of 62.3, 89.5, and 888.9 days.[3] The star is surrounded by a circumstellar dust shell that seems primarily composed of oxides of iron, magnesium, and aluminium, rather than silicates.[13]

References
  1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
  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. Hinkle, Kenneth H.; et al. (February 2002), "Velocity Observations of Multiple-Mode Asymptotic Giant Branch Variable Stars", The Astronomical Journal, 123 (2): 1002–1012, Bibcode:2002AJ....123.1002H, doi:10.1086/338314
  4. Keenan, P.; McNeil, R. (October 1989), "The Perkins catalog of revised MK types for the cooler stars", Astrophysical Journal Supplement Series, 71: 245–266, Bibcode:1989ApJS...71..245K, doi:10.1086/191373.
  5. Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  6. Schiavon, Ricardo P. (July 2007), "Population Synthesis in the Blue. IV. Accurate Model Predictions for Lick Indices and UBV Colors in Single Stellar Populations", The Astrophysical Journal Supplement Series, 171 (1): 146–205, arXiv:astro-ph/0611464, Bibcode:2007ApJS..171..146S, doi:10.1086/511753, S2CID 13946698.
  7. Halabi, Ghina M.; Eid, Mounib El (August 2015), "Exploring masses and CNO surface abundances of red giant stars", Monthly Notices of the Royal Astronomical Society, 451 (3): 2957–2967, arXiv:1507.01517, Bibcode:2015MNRAS.451.2957H, doi:10.1093/mnras/stv1141, S2CID 118707332.
  8. 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.
  9. Ramírez, Solange V.; et al. (2000), "Stellar Iron Abundances at the Galactic Center", The Astrophysical Journal, 537 (1): 205–220, arXiv:astro-ph/0002062, Bibcode:2000ApJ...537..205R, doi:10.1086/309022, S2CID 14713550.
  10. "g Her". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-06-13.
  11. 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.
  12. Otero, Sebastian Alberto (June 28, 2011), "g Herculis", AAVSO Website, American Association of Variable Star Observers, retrieved 20 July 2014
  13. Posch, Th.; et al. (October 2002), "On the origin of the 19.5 μ m feature. Identifying circumstellar Mg-Fe-oxides", Astronomy and Astrophysics, 393: L7–L10, Bibcode:2002A&A...393L...7P, doi:10.1051/0004-6361:20021127.
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