HD 201772

HD 201772, also known as HR 8104, is a yellowish-white hued star located in the southern constellation Microscopium. It has an apparent magnitude of 5.26,[2] making it one of the brighter members of this generally faint constellation. The object is located relatively close at a distance of 111 light-years based on Gaia DR3 parallax measurements[1] but is approaching closer with a heliocentric radial velocity of −41 km/s.[5] At its current distance, HD 201772's brightness is diminished by 0.11 magnitudes due to interstellar dust.[14]

HD 201772
HD 201772 is the star circled in red
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Microscopium
Right ascension 21h 13m 03.06827s[1]
Declination −39° 25′ 29.7097″[1]
Apparent magnitude (V) 5.26[2]
Characteristics
Spectral type F5 IV-V[3] or F6 V Fe−0.9 CH−0.5[4]
B−V color index +0.44[2]
Astrometry
Radial velocity (Rv)−41±1[5] km/s
Proper motion (μ) RA: +185.855 mas/yr[1]
Dec.: −113.449 mas/yr[1]
Parallax (π)29.2823 ± 0.0827 mas[1]
Distance111.4 ± 0.3 ly
(34.15 ± 0.10 pc)
Absolute magnitude (MV)+2.66[6]
Details
Mass1.5[1] M☉
Radius2.18±0.09[7] R☉
Luminosity7.83±0.04[1] L☉
Surface gravity (log g)3.91±0.09[8] cgs
Temperature6,519±80[9] K
Metallicity [Fe/H]−0.18±0.03[10] dex
Rotational velocity (v sin i)10[11] km/s
Age2.23±0.04 Gyr
Other designations
56 G. Microscopii[12], CD−39°14152, CPD−39°8898, GC 29640, HD 201772, HIP 104738, HR 8104, SAO 212793, LTT 8413[13]
Database references
SIMBADdata

The star has been given multiple stellar classifications over the years. It was given the luminosity class of a subgiant and main sequence star (IV/V; IV-V)[15][3] and a dwarf (V).[16][17] Most sources generally agree that it is a F5 star. Richard O. Gray and colleagues give HD 201772 a class of F6 V Fe−0.9 CH−0.5, which indicates that it is a F-type main-sequence star with an underabundance of iron and CH molecules in its spectrum.[4]

It has 1.47 times the mass of the Sun[18] and an enlarged radius of 2.2 R☉.[7] It radiates 7.8 times the luminosity of the Sun from its photosphere at an effective temperature of 6,519 K.[9] At an age of 2.5 billion years, HD 201722 is currently 1.33 magnitudes above the ZAMS, consistent with a star that is evolving off the main sequence.[11] The star has an iron abundance 66% that of the Sun,[10] making it metal deficient. It spins modestly with a projected rotational velocity of 10 km/s.[11]

HD 201772 is suspected to be a spectroscopic binary consisting of the subgiant described above and an ordinary F6 V star with a mass of 1.31 M☉.[19] However, the stars have no separation or an orbital period.[20] This is because the companion might be a result of spectrum contamination, so HD 201772 is more likely to be a solitary star.[21]

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. Corben, P. M.; Stoy, R. H. (1968). "Photoelectric Magnitudes and Colours for Bright Southern Stars". Monthly Notes of the Astronomical Society of South Africa. 27: 11. Bibcode:1968MNSSA..27...11C. ISSN 0024-8266.
  3. Gray, Richard O. (September 1989). "The extension of the MK spectral classification system to the intermediate population II F type stars". The Astronomical Journal. 98: 1049. Bibcode:1989AJ.....98.1049G. doi:10.1086/115195. ISSN 0004-6256.
  4. Gray, R. O.; Corbally, C. J.; Garrison, R. F.; McFadden, M. T.; Bubar, E. J.; McGahee, C. E.; O'Donoghue, A. A.; Knox, E. R. (2 June 2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc--The Southern Sample". The Astronomical Journal. 132 (1): 161–170. arXiv:astro-ph/0603770. Bibcode:2006AJ....132..161G. doi:10.1086/504637. eISSN 1538-3881. ISSN 0004-6256.
  5. 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. Masana, E.; Jordi, C.; Ribas, I. (10 April 2006). "Effective temperature scale and bolometric corrections from 2MASS photometry". Astronomy & Astrophysics. 450 (2): 735–746. arXiv:astro-ph/0601049. Bibcode:2006A&A...450..735M. doi:10.1051/0004-6361:20054021. eISSN 1432-0746. ISSN 0004-6361.
  8. 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. Casagrande, L.; Schönrich, R.; Asplund, M.; Cassisi, S.; Ramírez, I.; Meléndez, J.; Bensby, T.; Feltzing, S. (26 May 2011). "New constraints on the chemical evolution of the solar neighbourhood and Galactic disc(s): Improved astrophysical parameters for the Geneva-Copenhagen Survey⋆". Astronomy & Astrophysics. 530: A138. arXiv:1103.4651. Bibcode:2011A&A...530A.138C. doi:10.1051/0004-6361/201016276. eISSN 1432-0746. ISSN 0004-6361.
  10. Netopil, Martin (4 May 2017). "Metallicity calibrations for dwarf stars and giants in the Geneva photometric system". Monthly Notices of the Royal Astronomical Society. 469 (3): 3042–3055. arXiv:1705.00883. Bibcode:2017MNRAS.469.3042N. doi:10.1093/mnras/stx1077. eISSN 1365-2966. ISSN 0035-8711.
  11. Nordström, B.; Mayor, M.; Andersen, J.; Holmberg, J.; Pont, F.; Jørgensen, B. R.; Olsen, E. H.; Udry, S.; Mowlavi, N. (16 April 2004). "The Geneva-Copenhagen survey of the Solar neighbourhood". Astronomy & Astrophysics. 418 (3): 989–1019. arXiv:astro-ph/0405198. Bibcode:2004A&A...418..989N. doi:10.1051/0004-6361:20035959. eISSN 1432-0746. ISSN 0004-6361.
  12. 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.
  13. "HD 201772". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved November 24, 2022.
  14. 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.
  15. Adams, Walter S.; Joy, Alfred H.; Humason, Milton L.; Brayton, Ada Margaret (April 1935). "The Spectroscopic Absolute Magnitudes and Parallaxes of 4179 Stars". The Astrophysical Journal. 81: 187. Bibcode:1935ApJ....81..187A. doi:10.1086/143628. eISSN 1538-4357. ISSN 0004-637X.
  16. Malaroda, S. (August 1975). "Study of the F-type 1 MK spectral types". The Astronomical Journal. 80: 637. Bibcode:1975AJ.....80..637M. doi:10.1086/111786. ISSN 0004-6256.
  17. Houk, N. (1982). Michigan Catalogue of Two-dimensional Spectral Types for the HD stars. Volume III: Declinations −40° to −26°. Bibcode:1982mcts.book.....H.
  18. Feltzing, S.; Holmberg, J.; Hurley, J. R. (October 2001). "The solar neighbourhood age-metallicity relation - Does it exist?". Astronomy & Astrophysics. 377 (3): 911–924. arXiv:astro-ph/0108191. Bibcode:2001A&A...377..911F. doi:10.1051/0004-6361:20011119. eISSN 1432-0746. ISSN 0004-6361.
  19. Tokovinin, Andrei (14 March 2014). "From Binaries to Multiples. II. Hierarchical Multiplicity of F and G Dwarfs". The Astronomical Journal. 147 (4): 87. arXiv:1401.6827. Bibcode:2014AJ....147...87T. doi:10.1088/0004-6256/147/4/87. eISSN 1538-3881. ISSN 0004-6256.
  20. Tokovinin, Andrei (14 March 2014). "From Binaries to Multiples. I. Data on F and G Dwarfs within 67 pc of the Sun". The Astronomical Journal. 147 (4): 86. arXiv:1401.6825. Bibcode:2014AJ....147...86T. doi:10.1088/0004-6256/147/4/86. eISSN 1538-3881. ISSN 0004-6256.
  21. 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.
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