HD 187086

HD 187086, also known as HR 7537, is a probable astrometric binary[15] (87% chance[16]) located in the southern constellation Telescopium. It has an average apparent magnitude of 5.9, making it faintly visible to the naked eye. The star is located relatively far at a distance of 1,020 light years based on Gaia DR3 parallax measurements[2] but is rapidly drifting closer with a heliocentric radial velocity of −64 km/s.[7] At its current distance, HD 187086's brightness is diminished by 0.27 magnitudes due to interstellar dust.[17] It has an absolute magnitude of −0.8.[8]

HD 187086

A light curve for HD 187086, plotted from Hipparcos data[1]
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Telescopium
Right ascension 19h 50m 14.05959s[2]
Declination −47° 33′ 26.6014″[2]
Apparent magnitude (V) 5.95 - 6.07[3]
Characteristics
Evolutionary stage AGB[4]
Spectral type M1 III[5]
B−V color index +1.67[6]
Variable type suspected[3]
Astrometry
Radial velocity (Rv)−64±1[7] km/s
Proper motion (μ) RA: +9.424 mas/yr[2]
Dec.: −10.867 mas/yr[2]
Parallax (π)3.1998 ± 0.0655 mas[2]
Distance1,020 ± 20 ly
(313 ± 6 pc)
Absolute magnitude (MV)−0.80[8]
Details
Mass1.76±0.09[9] M☉
Radius111±6[10] R☉
Luminosity1,031±56[11] L☉
Surface gravity (log g)1.5±1[2] cgs
Temperature3,821±122[12] K
Metallicity [Fe/H]+0.24[2] dex
Other designations
69 G. Telescopii[13], NSV 12432, CD−47°13103, CPD−47°9366, GC 27427, HD 187086, HIP 95798, HR 7537, SAO 229887[14]
Database references
SIMBADdata

The primary has a stellar classification of M1 III,[5] indicating that it is a red giant. It is currently on the asymptotic giant branch, fusing hydrogen and helium shells around an inert carbon core. It has 1.76 times the mass of the Sun[9] but it has expanded to 111 times the solar radius.[10] It radiates 1,031 times the luminosity of the Sun[11] from its enlarged photosphere at an effective temperature of 3,821 K,[12] giving it a red hue. HD 187086 is particularly metal enriched ([Fe/H] = +0.24).[2]

HD 187086 fluctuates between 5.95 and 6.07[3] and its variability was first noticed by P.M. Corben in 1971 after being listed as an ordinary M-type giant a year prior.[6][18] In 2002, Chris Koen and Laurent Eyer reported that the Hipparcos data shows periodic fluctuations with an amplitude of 0.023 magnitudes, and a period of 7.6805 days.[19] As of 2004 however, it is not confirmed to be variable.[20]

References
  1. EAS (1997). "The HIPPARCOS and TYCHO catalogues". Astrometric and Photometric Star Catalogues Derived from the ESA Hipparcos Space Astrometry Mission. ESA SP Series. Noordwijk, Netherlands: ESA Publications Division. 1200. Bibcode:1997ESASP1200.....E. ISBN 9290923997. Retrieved 15 October 2022.
  2. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. Samus’, N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (January 2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80–88. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085. eISSN 1562-6881. ISSN 1063-7729. S2CID 125853869.
  4. Eggen, Olin J. (July 1992). "Asymptotic giant branch stars near the sun". The Astronomical Journal. 104: 275. Bibcode:1992AJ....104..275E. doi:10.1086/116239. ISSN 0004-6256.
  5. Houk, Nancy (1978). Michigan catalogue of two-dimensional spectral types for the HD stars: Declinations −53° to −40°. Vol. 2. Bibcode:1978mcts.book.....H.
  6. Corben, P. M. (April 1971). "Photoelectric Magnitudes and Colours for Bright Southern Stars". Monthly Notes of the Astronomical Society of South Africa. 30 (4): 37. Bibcode:1971MNSSA..30...37C. ISSN 0024-8266.
  7. Gontcharov, G. A. (November 2006). "Pulkovo Compilation of Radial Velocities for 35,495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. eISSN 1562-6873. ISSN 1063-7737. S2CID 119231169.
  8. Corbally, C. J.; Garrison, R. F. (1984). "Which Map of Absolute Magnitudes: Keenan or Schmidt-Kaler?". The Mk Process and Stellar Classification: 277. Bibcode:1984mpsc.conf..277C.
  9. Kervella, Pierre; Arenou, Frédéric; Thévenin, Frédéric (2022). "Stellar and substellar companions from Gaia EDR3". Astronomy & Astrophysics. 657: A7. arXiv:2109.10912. Bibcode:2022A&A...657A...7K. doi:10.1051/0004-6361/202142146. eISSN 1432-0746. ISSN 0004-6361.
  10. Kervella, P.; Thévenin, F.; Di Folco, E.; Ségransan, D. (October 2004). "The angular sizes of dwarf stars and subgiants". Astronomy & Astrophysics. 426 (1): 297–307. arXiv:astro-ph/0404180. Bibcode:2004A&A...426..297K. doi:10.1051/0004-6361:20035930. eISSN 1432-0746. ISSN 0004-6361.
  11. 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.
  12. Stassun, Keivan G.; et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467. eISSN 1538-3881. hdl:1721.1/124721. S2CID 166227927.
  13. Gould, Benjamin Apthorp (1878). "Uranometria Argentina : brillantez y posicion de las estrellas fijas, hasta la septima magnitud, comprendidas dentro de cien grados del polo austral : con atlas". Resultados del Observatorio Nacional Argentino. 1. Bibcode:1879RNAO....1.....G.
  14. "HD 187086". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved February 1, 2023.
  15. Eggleton, P. P.; Tokovinin, A. A. (11 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. eISSN 1365-2966. ISSN 0035-8711. S2CID 14878976.
  16. Frankowski, A.; Jancart, S.; Jorissen, A. (19 December 2006). "Proper-motion binaries in the Hipparcos catalogue". Astronomy & Astrophysics. 464 (1): 377–392. arXiv:astro-ph/0612449. Bibcode:2007A&A...464..377F. doi:10.1051/0004-6361:20065526. eISSN 1432-0746. ISSN 0004-6361.
  17. Gontcharov, George A.; Mosenkov, Aleksandr V. (28 September 2017). "Verifying reddening and extinction for Gaia DR1 TGAS main sequence stars". Monthly Notices of the Royal Astronomical Society. 472 (4): 3805–3820. arXiv:1709.01160. Bibcode:2017MNRAS.472.3805G. doi:10.1093/mnras/stx2219. eISSN 1365-2966. ISSN 0035-8711.
  18. Eggen, O. J.; Stokes, N. R. (July 1970). "Narrow-Band and Broad-Band Photometry of Red Stars. III. Southern Giants". The Astrophysical Journal. 161: 199. Bibcode:1970ApJ...161..199E. doi:10.1086/150525. eISSN 1538-4357. ISSN 0004-637X.
  19. Koen, Chris; Eyer, Laurent (March 2002). "New periodic variables from the Hipparcos epoch photometry". Monthly Notices of the Royal Astronomical Society. 331 (1): 45–59. arXiv:astro-ph/0112194. Bibcode:2002MNRAS.331...45K. doi:10.1046/j.1365-8711.2002.05150.x. S2CID 10505995. Retrieved 4 February 2023.
  20. Samus, N. N.; Durlevich, O. V. (November 2004). "VizieR Online Data Catalog: Combined General Catalogue of Variable Stars (Samus+ 2004)". VizieR Online Data Catalog: II/250. Bibcode:2004yCat.2250....0S.
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