HD 191220

HD 191220

Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Octans
Right ascension	20^h 24^m 54.91771^s[1]
Declination	−83° 18′ 38.2301″[1]
Apparent magnitude (V)	6.14±0.01[2]
Characteristics
Spectral type	A2/3 mA8-F0[3]
U−B color index	+0.13[4]
B−V color index	+0.20[4]
Astrometry
Radial velocity (Rv)	0.1±1.3[5] km/s
Proper motion (μ)	RA: +23.223 mas/yr[1] Dec.: +6.228 mas/yr[1]
Parallax (π)	13.331 ± 0.0247 mas[1]
Distance	244.7 ± 0.5 ly (75.0 ± 0.1 pc)
Absolute magnitude (MV)	+1.76[6]
Details
Mass	2.06±0.40[7] M☉
Radius	2.17±0.06[8] R☉
Luminosity	15.57[9] L☉
Surface gravity (log g)	4.12±0.06[10] cgs
Temperature	7,706±126[11] K
Metallicity [Fe/H]	−0.02[12] dex
Age	979±166[1] Myr
Other designations
45 G. Octantis[13], CD−83°253, CPD−83°695, GC 28176, HD 191220, HIP 100697, HR 7698, SAO 258856[14]
Database references
SIMBAD	data

HD 191220, also known as HR 7698, is a solitary white hued star located in the southern circumpolar constellation Octans. It has an apparent magnitude of 6.14,[2] placing it near the limit for naked eye visibility. The object is located relatively close at a distance of 245 light years based on Gaia DR3 parallax measurements[1] but is slowly receding with a heliocentric radial velocity of 0.1 km/s.[5] At its current distance, HD 191220's brightness is diminished by 0.22 magnitudes due to interstellar dust.[15]

This is a chemically peculiar Am star[16] with a stellar classification of A2/3mA8-F0,[3] an A-type star with the metallic lines of a star with a class of A8-F0. It has double the mass of the Sun and 2.2 times its girth.[7] It radiates 15.57 times the luminosity of the Sun[9] from its photosphere at an effective temperature of 7,706 K.[11] HD 191220 is estimated to be nearly a billion years old[12] and has a near solar metallicity — what astronomers dub a star's abundance of chemical elements heavier than helium.[12]

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.
3. 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.
4. 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. 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. Stassun, Keivan G.; Oelkers, Ryan J.; Pepper, Joshua; et al. (20 August 2018). "The TESS Input Catalog and Candidate Target List". The Astronomical Journal. 156 (3): 102. arXiv:1706.00495. Bibcode:2018AJ....156..102S. doi:10.3847/1538-3881/aad050. eISSN 1538-3881.
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. 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. Bai, Yu; Liu, JiFeng; Bai, ZhongRui; Wang, Song; Fan, DongWei (2 August 2019). "Machine-learning Regression of Stellar Effective Temperatures in the Second Gaia Data Release". The Astronomical Journal. 158 (2): 93. arXiv:1906.09695. Bibcode:2019AJ....158...93B. doi:10.3847/1538-3881/ab3048. eISSN 1538-3881.
12. 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. 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 191220". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved November 21, 2022.
15. 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.
16. Renson, P.; Manfroid, J. (19 March 2009). "Catalogue of Ap, HgMn and Am stars". Astronomy & Astrophysics. 498 (3): 961–966. Bibcode:2009A&A...498..961R. doi:10.1051/0004-6361/200810788. eISSN 1432-0746. ISSN 0004-6361.