HD 196917

HD 196917 (HR 7909; 17 G. Microscopii; NSV 25227) is a solitary star[16] located in the southern constellation Microscopium. It is faintly visible to the naked eye as a red-hued point of light with an apparent magnitude of 5.74.[2] Gaia DR3 parallax measurements imply a distance of 426 light-years and[1] it is rapidly approaching the Solar System with a heliocentric radial velocity of −97.3 km/s. [9] At its current distance, HD 196917's brightness is diminished by 0.13 magnitudes due to interstellar extinction[17] and it has an absolute magnitude of +0.04.[10]

HD 196917
Location of HD 196917 on the map (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Microscopium
Right ascension 20h 41m 23.65766s[1]
Declination −31° 35′ 53.8334″[1]
Apparent magnitude (V) 5.74[2] (5.75 - 5.76)[3]
Characteristics
Evolutionary stage AGB[4]
Spectral type M1 III[5] or M0 III[6]
B−V color index +1.53[7]
Variable type suspected[8]
Astrometry
Radial velocity (Rv)−97.3±2.3[9] km/s
Proper motion (μ) RA: +109.914 mas/yr[1]
Dec.: −60.256 mas/yr[1]
Parallax (π)7.6563 ± 0.0891 mas[1]
Distance426 ± 5 ly
(131 ± 2 pc)
Absolute magnitude (MV)+0.04[10]
Details
Mass1.27[11] M☉
Radius44.2±2.2[12] R☉
Luminosity620+45
−20[1] L☉
Surface gravity (log g)1.40[11] cgs
Temperature3,908±122[13] K
Metallicity [Fe/H]−0.28[11] dex
Other designations
17 G. Microscopii[14], NSV 25227, CD−32°16130, CPD−32°6177, FK5 3652, GC 28808, HD 196917, HIP 102092, HR 7909, SAO 212345, TIC 441396067[15]
Database references
SIMBADdata

HD 196917 has a stellar classification of either M1 III[5] or M0 III,[6] indicating that it is an evolved M-type giant. It is currently on the asymptotic giant branch,[4] fusing hydrogen and helium shells around an inert carbon core. It has 1.27 times the mass of the Sun[11] but it has expanded to 44.2 times the radius of the Sun.[12] It radiates 620 times the luminosity of the Sun[1] from its enlarged photosphere at an effective temperature of 3,908 K.[13] HD 196917 is metal deficient with an iron abundance of [Fe/H] = −0.28 or 52.5% of the Sun's.[11]

The variability of the star was first detected in 1997 by the Hipparcos mission.[18] It found variations between 5.82 and 5.86 in the Hipparcos passband. Koen & Lyer (2002) observed visual variations from the star and found that HD 196917 varies by 0.009 magnitudes within 21.01 hours.[19] As of 2004, its variability has not been confirmed. [20]

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. 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. S2CID 17128864.
  3. "VSX : Detail for NSV 25227". www.aavso.org.
  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. S2CID 121672252.
  5. Houk, N. (1982). Michigan Catalogue of Two-dimensional Spectral Types for the HD stars. Declinations −40° to −26°. Vol. 3. Bibcode:1982mcts.book.....H.
  6. Evans, D. S.; Menzies, A.; Stoy, R. H. (October 1, 1957). "Fundamental Data for Southern Stars (First List)". Monthly Notices of the Royal Astronomical Society. Oxford University Press (OUP). 117 (5): 534–561. Bibcode:1957MNRAS.117..534E. doi:10.1093/mnras/117.5.534. ISSN 0035-8711. S2CID 120032200.
  7. 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.
  8. 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.
  9. 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.
  10. 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.
  11. 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.
  12. Kervella, P.; Thévenin, F.; Di Folco, E.; Ségransan, D. (April 8, 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.
  13. 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.
  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 196917". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 12, 2023.
  16. 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.
  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. S2CID 118879856.
  18. Perryman, M. A. C.; Lindegren, L.; Kovalevsky, J.; Hoeg, E.; Bastian, U.; Bernacca, P. L.; Crézé, M.; Donati, F.; Grenon, M.; Grewing, M.; van Leeuwen, F. (July 1997). "The HIPPARCOS Catalogue". Astronomy and Astrophysics. 323: L49–L52. Bibcode:1997A&A...323L..49P. ISSN 0004-6361.
  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. eISSN 1365-2966. ISSN 0035-8711. S2CID 10505995.
  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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