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.
  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. 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.
  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.
  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.
  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.
  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.
  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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