89 Herculis

89 Herculis is a binary star system located about 4,700 light years away from the Sun in the northern constellation of Hercules. It is visible to the naked eye as a faint, fifth magnitude star. The system is moving closer to the Earth with a heliocentric radial velocity of −28.5 km/s.[5]

89 Herculis
Location of 89 Her (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Hercules
Right ascension 17h 55m 25.18845s[1]
Declination 26° 02′ 59.9701″[1]
Apparent magnitude (V) (5.34 - 5.54[2])
Characteristics
Evolutionary stage post-AGB
Spectral type F2Ibe[3]
U−B color index −0.34[4]
B−V color index +0.34[4]
Variable type SRd[2]
Astrometry
Radial velocity (Rv)−28.5[5] km/s
Proper motion (μ) RA: 3.894[1] mas/yr
Dec.: 5.193[1] mas/yr
Parallax (π)0.6893 ± 0.0718[1] mas
Distanceapprox. 4,700 ly
(approx. 1,500 pc)
Absolute magnitude (MV)−6.5[6]
Details
89 Her A
Mass1.0[7] M☉
Radius71.0[7] R☉
Luminosity8,350[7] L☉
Surface gravity (log g)0.55[3] cgs
Temperature6,550[3] K
Metallicity−0.5[3]
Rotational velocity (v sin i)23[8] km/s
Other designations
89 Her, V441 Herculis, BD+26°3120, FK5 1468, GC 24382, HD 163506, HIP 87747, HR 6685, SAO 85545[9]
Database references
SIMBADdata
Exoplanet Archivedata

This is a spectroscopic binary with the pair surrounded by a dusty disc. The system shows variable brightness and spectral line profiles.[10] The companion has a very low mass and luminosity and orbits the primary in 288 days.[3]

The primary component has a stellar classification of F2Ibe,[3] and is among a rare class of post-asymptotic giant branch stars – low mass stars in the last stages of their lives, highly inflated to appear as supergiants.[3] It is classified as a semiregular variable star, subtype SRd, and ranges from magnitude 5.3 down to 5.5 over a period of around 68 days.[2] The star has expanded to 71[7] times the Sun's radius and is radiating 8,350[7] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 6,550 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. Gaia DR2 record for this source at VizieR.
  2. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  3. Hillen, M.; Verhoelst, T.; Van Winckel, H.; Chesneau, O.; Hummel, C. A.; Monnier, J. D.; Farrington, C.; Tycner, C.; Mourard, D.; Ten Brummelaar, T.; Banerjee, D. P. K.; Zavala, R. T. (2013). "An interferometric study of the post-AGB binary 89 Herculis. I. Spatially resolving the continuum circumstellar environment at optical and near-IR wavelengths with the VLTI, NPOI, IOTA, PTI, and the CHARA Array". Astronomy & Astrophysics. 559: A111. arXiv:1308.6715. Bibcode:2013A&A...559A.111H. doi:10.1051/0004-6361/201321616. S2CID 119182156.
  4. Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
  5. Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Washington. Bibcode:1953GCRV..C......0W.
  6. Kipper, Tõnu (2011). "On the Optical Spectrum of 89 Her". Baltic Astronomy. 20: 65. Bibcode:2011BaltA..20...65K. doi:10.1515/astro-2017-0269.
  7. Hillen, M.; Menu, J.; Van Winckel, H.; Min, M.; Gielen, C.; Wevers, T.; Mulders, G. D.; Regibo, S.; Verhoelst, T. (2014). "An interferometric study of the post-AGB binary 89 Herculis. II. Radiative transfer models of the circumbinary disk". Astronomy & Astrophysics. 568: A12. arXiv:1405.1960. Bibcode:2014A&A...568A..12H. doi:10.1051/0004-6361/201423749. S2CID 6700179.
  8. Hoffleit, Dorrit; Jaschek, Carlos (1991). "The Bright star catalogue". New Haven. Bibcode:1991bsc..book.....H.
  9. "89 Her". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-06-15.
  10. Burki, G.; Mayor, M.; Rufener, F. (1980). "Study of the Variable F-Type Supergiants HD161796 and HD163506 in Radial Velocity and Photometry". Astronomy and Astrophysics Supplement. 42: 383. Bibcode:1980A&AS...42..383B.
  • Kaler's, James B. "89 Herculis". Stars. University of Illinois. Retrieved 2019-06-16.
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