Wikipedia

HD 218108

HD 218108, also known as HR 8786, is a solitary, white hued star located in the southern circumpolar constellation Octans. It has an apparent magnitude of 6.11,[2] making it faintly visible to the naked eye under ideal conditions. Based on parallax measurements from Gaia DR3, the object is estimated to be 247 light years away.[1] It appears to be approaching the Solar System with a fairly constrained radial velocity of −7 km/s.[5] Paunzen et al. (2001) lists it as a λ Boötis star with a weak magnesium line.[16]

HD 218108
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Octans
Right ascension 23h 08m 23.84044s[1]
Declination −79° 28′ 50.4748″[1]
Apparent magnitude (V) 6.11±0.01[2]
Characteristics
Spectral type A6 Vn[3]
U−B color index +0.10[4]
B−V color index +0.14[4]
Astrometry
Radial velocity (Rv)−7±4.4[5] km/s
Proper motion (μ) RA: +93.016 mas/yr[1]
Dec.: −35.907 mas/yr[1]
Parallax (π)13.1893 ± 0.0236 mas[1]
Distance247.3 ± 0.4 ly
(75.8 ± 0.1 pc)
Absolute magnitude (MV)+1.78[6]
Details
Mass1.80[7] M☉
Radius2±0.1[8] R☉
Luminosity15.24[9] L☉
Surface gravity (log g)4.17±0.07[10] cgs
Temperature8,213±244[11] K
Metallicity [Fe/H]−0.01[12] dex
Rotational velocity (v sin i)194±2[13] km/s
Age249[7] Myr
Other designations
79 G. Octantis[14], CPD−80°1064, FK5 3847, GC 32194, HD 218108, HIP 114258, HR 8786, SAO 258105[15]
Database references
SIMBADdata

HD 218108 has a stellar classification of A6 Vn,[3] indicating that it is an A-type main-sequence star with broad or nebulous absorption lines due to rapid rotation. In 1966, David Stanley Evans gave it a slightly cooler class of A7 Vn.[17] However, Houk and Cowley (1975) give it a classification of A3/4 V, a main sequence star with the characteristics of an A3 and A4 star.[18] Paunzen et al. (2001) gives it a class of A3 V, indicating that it is instead an ordinary A-type main-sequence star.[16]

Nevertheless, it has 1.8 times the mass of the Sun[7] and twice its radius.[8] It radiates 15.24 times the luminosity of the Sun[9] from its photosphere at an effective temperature of 8,213 K. It is estimated to be 249 million years old[7] and is currently spinning with a high projected rotational velocity of 149 km/s.[13] A solar metallicity was calculated for HD 218108.[12]

References

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  1. ^ a b c d e 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. ^ a b Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H. ISSN 0004-6361.
  3. ^ a b Abt, Helmut A.; Morrell, Nidia I. (July 1995). "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars". The Astrophysical Journal Supplement Series. 99: 135. Bibcode:1995ApJS...99..135A. doi:10.1086/192182. ISSN 0067-0049.
  4. ^ a b Johnson, H. L.; Mitchell, R. I.; Iriarte, B.; Wisniewski, W. Z. (1966). "UBVRIJKL Photometry of the Bright Stars". Communications of the Lunar and Planetary Laboratory. 4: 99–110. Bibcode:1966CoLPL...4...99J.
  5. ^ a b 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.
  6. ^ 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.
  7. ^ a b c d David, Trevor J.; Hillenbrand, Lynne A. (12 May 2015). "The Ages of Early-type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets". The Astrophysical Journal. 804 (2): 146. arXiv:1501.03154. Bibcode:2015ApJ...804..146D. doi:10.1088/0004-637X/804/2/146. eISSN 1538-4357.
  8. ^ a b 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.
  9. ^ a b McDonald, I.; Zijlstra, A. A.; Boyer, M. L. (21 November 2012). "Fundamental parameters and infrared excesses of Hipparcos stars: Parameters and IR excesses from Hipparcos". Monthly Notices of the Royal Astronomical Society. 427 (1): 343–357. arXiv:1208.2037. Bibcode:2012MNRAS.427..343M. doi:10.1111/j.1365-2966.2012.21873.x. eISSN 1365-2966. ISSN 0035-8711.
  10. ^ Allende Prieto, C.; Lambert, D. L. (December 1999). "Fundamental parameters of nearby stars from the comparison with evolutionary calculations: masses, radii and effective temperatures". Astronomy and Astrophysics. 352: 555–562. arXiv:astro-ph/9911002. Bibcode:1999A&A...352..555A. ISSN 0004-6361.
  11. ^ Paunzen, E.; Schnell, A.; Maitzen, H. M. (October 2006). "An empirical temperature calibration for the Δa photometric system II: The A-type and mid F-type stars". Astronomy & Astrophysics. 458 (1): 293–296. arXiv:astro-ph/0607567. Bibcode:2006A&A...458..293P. doi:10.1051/0004-6361:20064889. eISSN 1432-0746. ISSN 0004-6361.
  12. ^ a b Gontcharov, G. A. (December 2012). "Dependence of kinematics on the age of stars in the solar neighborhood". Astronomy Letters. 38 (12): 771–782. arXiv:1606.08814. Bibcode:2012AstL...38..771G. doi:10.1134/S1063773712120031. eISSN 1562-6873. ISSN 1063-7737.
  13. ^ a b Díaz, C. G.; González, J. F.; Levato, H.; Grosso, M. (July 2011). "Accurate stellar rotational velocities using the Fourier transform of the cross correlation maximum". Astronomy & Astrophysics. 531: A143. arXiv:1012.4858. Bibcode:2011A&A...531A.143D. doi:10.1051/0004-6361/201016386. eISSN 1432-0746. ISSN 0004-6361.
  14. ^ 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.
  15. ^ "HD 218108". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 22, 2022.
  16. ^ a b Paunzen, E.; Duffee, B.; Heiter, U.; Kuschnig, R.; Weiss, W. W. (July 2001). "A spectroscopic survey for λ Bootis stars". Astronomy & Astrophysics. 373 (2): 625–632. Bibcode:2001A&A...373..625P. doi:10.1051/0004-6361:20010630. eISSN 1432-0746. ISSN 0004-6361.
  17. ^ Evans, D. S. (1966). "Fundamental data for Southern stars (6th list)". Royal Greenwich Observatory Bulletins. 110: 185. Bibcode:1966RGOB..110..185E.
  18. ^ Houk, N.; Cowley, A. P. (1975). University of Michigan Catalogue of two-dimensional spectral types for the HD stars. Volume I. Declinations −90° to −53°. Bibcode:1975mcts.book.....H.
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