89 Herculis

{{Short description|Star in the constellation Hercules}}

{{Starbox begin}}

{{Starbox image

| image=

{{Location mark

|image=Hercules constellation map.svg

|float=center

|alt=

|label=

|position=right

|width=280

|mark=Red circle.svg

|mark_width=10

|mark_link=89 Herculis

|x=387|y=640

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|caption=Location of 89 Her (circled)

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{{Starbox observe

|epoch=J2000

|ra={{RA|17|55|25.18845}}{{Cite Gaia DR2|4582795323914832000}}

| dec={{DEC|+26|02|59.9701}}

|appmag_v={{nowrap|(5.34 - 5.54)}}

|constell=Hercules

}}

{{Starbox character

|type=post-AGB

|class=F2Ibe{{cite journal|bibcode=2013A&A...559A.111H|arxiv=1308.6715|title=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|journal=Astronomy & Astrophysics|volume=559|pages=A111|last1=Hillen|first1=M.|last2=Verhoelst|first2=T.|last3=Van Winckel|first3=H.|last4=Chesneau|first4=O.|last5=Hummel|first5=C. A.|last6=Monnier|first6=J. D.|last7=Farrington|first7=C.|last8=Tycner|first8=C.|last9=Mourard|first9=D.|last10=Ten Brummelaar|first10=T.|last11=Banerjee|first11=D. P. K.|last12=Zavala|first12=R. T.|year=2013|doi=10.1051/0004-6361/201321616|s2cid=119182156}}

|b-v=+0.34{{cite journal|bibcode=2002yCat.2237....0D|title=VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system|journal=CDS/ADC Collection of Electronic Catalogues|volume=2237|last1=Ducati|first1=J. R.|year=2002}}

|u-b=−0.34

|variable=SRd{{cite journal|bibcode=2009yCat....102025S|title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)|journal=VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S|volume=1|display-authors=etal|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}

}}

{{Starbox astrometry

|radial_v=−28.5{{cite journal|bibcode=1953GCRV..C......0W|title=General catalogue of stellar radial velocities|journal=Washington|last1=Wilson|first1=Ralph Elmer|year=1953}}

|prop_mo_ra=3.894

|prop_mo_dec=5.193

|parallax=0.6893

|p_error=0.0718

|parallax_footnote=

|absmag_v=−6.5{{cite journal|bibcode=2011BaltA..20...65K|title=On the Optical Spectrum of 89 Her|journal=Baltic Astronomy|volume=20|pages=65|last1=Kipper|first1=Tõnu|year=2011|doi=10.1515/astro-2017-0269|doi-access=free}}

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{{Starbox orbit

|reference={{cite journal |bibcode=1993A&A...269..242W |title=A model for the 89 Herculis system |last1=Waters |first1=L. B. F. M. |last2=Waelkens |first2=C. |last3=Mayor |first3=M. |last4=Trams |first4=N. R. |journal=Astronomy and Astrophysics |date=1993 |volume=269 |page=242 }}

|period_unitless=288.36 days

|eccentricity=0.189

|k1=3.09

}}

{{Starbox detail

|component1=89 Her A

|mass=1.0

|radius=71.0{{cite journal|bibcode=2014A&A...568A..12H|arxiv=1405.1960|title=An interferometric study of the post-AGB binary 89 Herculis. II. Radiative transfer models of the circumbinary disk|journal=Astronomy & Astrophysics|volume=568|pages=A12|last1=Hillen|first1=M.|last2=Menu|first2=J.|last3=Van Winckel|first3=H.|last4=Min|first4=M.|last5=Gielen|first5=C.|last6=Wevers|first6=T.|last7=Mulders|first7=G. D.|last8=Regibo|first8=S.|last9=Verhoelst|first9=T.|year=2014|doi=10.1051/0004-6361/201423749|s2cid=6700179}}

|luminosity=8,350

|temperature=6,550

|metal=−0.5

|gravity=0.55

|rotational_velocity=23{{cite journal|bibcode=1991bsc..book.....H|title=The Bright star catalogue|journal=New Haven|last1=Hoffleit|first1=Dorrit|last2=Jaschek|first2=Carlos|year=1991}}

|age=

}}

{{Starbox catalog

|names={{odlist | F=89 Her | V=V441 Herculis | BD=+26°3120 | FK5=1468 | HD=163506 | HIP=87747 | HR=6685 | SAO=85545 | GC=24382 | AAVSO=1751+26 }}{{cite simbad | title=89 Her | access-date=2019-06-15 }}

}}

{{Starbox reference

|Simbad=HD+163506

}}

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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.

This is a spectroscopic binary with the pair surrounded by a dusty disc, and an hourglass-shaped nebula formed from outflowing gas.{{cite journal | arxiv=2301.06965 | doi=10.1051/0004-6361/202244415 | title=The nebula around the binary post-AGB star 89 Herculis | year=2023 | last1=Gallardo Cava | first1=I. | last2=Alcolea | first2=J. | last3=Bujarrabal | first3=V. | last4=Gómez-Garrido | first4=M. | last5=Castro-Carrizo | first5=A. | journal=Astronomy & Astrophysics | volume=671 | pages=A80 | bibcode=2023A&A...671A..80G | s2cid=255942182 }} The mass of the nebula is about {{solar mass|0.018|link=yes}}, of which a majority is in the outflow. The system shows variable brightness and spectral line profiles.{{cite journal|bibcode=1980A&AS...42..383B|title=Study of the Variable F-Type Supergiants HD161796 and HD163506 in Radial Velocity and Photometry|journal=Astronomy and Astrophysics Supplement|volume=42|pages=383|last1=Burki|first1=G.|last2=Mayor|first2=M.|last3=Rufener|first3=F.|year=1980}} The companion has a very low mass and luminosity and orbits the primary in 288 days.

File:V441HerLightCurve.png light curve for V441 Herculis, adapted from Fernie and Seager (1995)]]

The primary component has a stellar classification of F2Ibe, 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. 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. The star has expanded to 71 times the Sun's radius and is radiating 8,350 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 6,550 K.

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