HD 186756

HD 186756, also known as HR 7521 or rarely 68 G. Telescopii, is a solitary orange hued star located in the southern constellation Telescopium. It has an apparent magnitude of 6.25,[2] placing it near the limit for naked eye visibility, even under ideal conditions. Gaia DR3 parallax measurements imply a distance of 743 light years;[1] it is currently approaching with a heliocentric radial velocity of −21.2 km/s.[4] At its current distance, HD 186756's brightness is diminished by 0.34 magnitudes due to extinction from interstellar dust[13] and it has an absolute magnitude of −0.96.[5]

HD 186756
Location of HD 186756 (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Telescopium
Right ascension 19h 48m 55.08814s[1]
Declination −52° 53′ 17.1953″[1]
Apparent magnitude (V) 6.25[2]
Characteristics
Spectral type K1 III[3]
U−B color index +1.12[2]
B−V color index +1.13[2]
Astrometry
Radial velocity (Rv)−21.2±0.4[4] km/s
Proper motion (μ) RA: +14.802 mas/yr[1]
Dec.: −48.522 mas/yr[1]
Parallax (π)4.3872 ± 0.0275 mas[1]
Distance743 ± 5 ly
(228 ± 1 pc)
Absolute magnitude (MV)−0.96[5]
Details
Mass1.23[6] M☉
Radius21.01±1.07[7] R☉
Luminosity177±2[8] L☉
Surface gravity (log g)1.83[6] cgs
Temperature4,747±122[9] K
Metallicity [Fe/H]−0.13[6] dex
Rotational velocity (v sin i)<1[10] km/s
Other designations
68 G. Telescopii[11], CD−53°8294, CPD−53°9678, FK5 3581, GC 27384, HD 186756, HIP 97491, HR 7521, SAO 246277[12]
Database references
SIMBADdata

This is an evolved red giant star with a stellar classification of K1 III. It has 123% the mass of the Sun[6] but it has expanded to 21.01 times the radius of the Sun.[7] The object radiates 177 times the luminosity of the Sun[8] from its enlarged photosphere at an effective temperature of 4,747 K.[9] HD 186756 is slightly metal deficient with an iron abundance of [Fe/H] = −0.13 (74% solar) and it spins too slowly for its projected rotational velocity to be measured accurately.[10]

References
  1. 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.
  2. Oja, T. (1970). "UBV-Fotometri danska Tel (ESO)". Private Communication: 0. Bibcode:1970Priv.........0O.
  3. Houk, Nancy (1978). Michigan catalogue of two-dimensional spectral types for the HD stars: Declinations −53° to −40°. Vol. 2. Bibcode:1978mcts.book.....H.
  4. 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.
  5. Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331–346. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. eISSN 1562-6873. ISSN 1063-7737. S2CID 119257644.
  6. Anders, F.; et al. (August 2019). "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18". Astronomy & Astrophysics. 628: A94. arXiv:1904.11302. Bibcode:2019A&A...628A..94A. doi:10.1051/0004-6361/201935765. eISSN 1432-0746. ISSN 0004-6361. S2CID 131780028.
  7. Kervella, P.; Thévenin, F.; Di Folco, E.; Ségransan, D. (October 2004). "The angular sizes of dwarf stars and subgiants. Surface brightness relations calibrated by interferometry". 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. S2CID 6077801.
  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. 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.
  10. De Medeiros, J. R.; Alves, S.; Udry, S.; Andersen, J.; Nordström, B.; Mayor, M. (January 2014). "A catalog of rotational and radial velocities for evolved stars V: Southern stars *". Astronomy & Astrophysics. 561: A126. arXiv:1312.3474. Bibcode:2014A&A...561A.126D. doi:10.1051/0004-6361/201220762. eISSN 1432-0746. ISSN 0004-6361. S2CID 54046583.
  11. 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.
  12. "HD 186756". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved April 20, 2023.
  13. 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. S2CID 118879856.
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