HD 170384

HD 170384, also known as HR 6931 or rarely 11 G. Coronae Australis, is a solitary white-hued star located in the southern constellation Corona Australis. It has an apparent magnitude of 6.02,[2] making it barely visible to the naked eye, even under ideal conditions. The object is located relatively close at a distance of 229.1 light-years based on Gaia DR3 parallax measurements[1] and it is drifting closer with a heliocentric radial velocity of −11.4 km/s.[6] At its current distance, HD 170384's brightness is diminished by interstellar extinction of 0.28 magnitudes[16] and it has an absolute magnitude of +1.86.[7]

HD 170384
Location of HD 170384 (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Corona Australis
Right ascension 18h 31m 02.94877s[1]
Declination −41° 54′ 49.8025″[1]
Apparent magnitude (V) 6.02±0.01[2]
Characteristics
Evolutionary stage main sequence star[3]
Spectral type A3 V[4]
B−V color index +0.14[5]
Astrometry
Radial velocity (Rv)−11.4±0.4[6] km/s
Proper motion (μ) RA: −3.406 mas/yr[1]
Dec.: −31.578 mas/yr[1]
Parallax (π)14.2387 ± 0.0341 mas[1]
Distance229.1 ± 0.5 ly
(70.2 ± 0.2 pc)
Absolute magnitude (MV)+1.86[7]
Details
Mass2.00[8] M☉
Radius1.91±0.10[9] R☉
Luminosity16.7+1.1
−1.0[3] L☉
Surface gravity (log g)4.19+0.08
−0.07[10] cgs
Temperature8,694[11] K
Metallicity [Fe/H]−0.01[12] dex
Rotation19.2 h[13]
Rotational velocity (v sin i)127±5[13] km/s
Age544[8] Myr
Other designations
11 G. Coronae Australis[14], CD−41°12871, CPD−41°8697, GC 25249, HD 170384, HIP 90759, HR 6931, SAO 229080[15]
Database references
SIMBADdata

This object has a stellar classification of A3 V, indicating that it is an ordinary A-type main-sequence star. It has double the Sun's mass[8] and 1.91 times the radius of the Sun.[9] It radiates 16.7 times the luminosity of the Sun[3] from its photosphere at an effective temperature of 8,694 K.[11] HD 170384 has a near solar metallicity at [Fe/H] = −0.01 (97% solar)[12] and it is estimated to be 544 million years old,[8] having completed 45% of its main sequence lifetime.[3] Like many hot stars HD 170384 spins rapidly, having a projected rotational velocity of 127 km/s and an estimated rotation period of 19.2 hours.[13]

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. Zorec, J.; Royer, F. (January 2012). "Rotational velocities of A-type stars IV: Evolution of rotational velocities". Astronomy & Astrophysics. 537: A120. arXiv:1201.2052. Bibcode:2012A&A...537A.120Z. doi:10.1051/0004-6361/201117691. eISSN 1432-0746. ISSN 0004-6361. S2CID 55586789.
  4. Houk, Nancy (1978). Michigan catalogue of two-dimensional spectral types for the HD stars: Declinations −53° to −40°. Vol. 2. Bibcode:1978mcts.book.....H.
  5. Corben, P. M. (April 1971). "Photoelectric Magnitudes and Colours for Bright Southern Stars". Monthly Notes of the Astronomical Society of South Africa. 30 (4): 37. Bibcode:1971MNSSA..30...37C. ISSN 0024-8266.
  6. 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.
  7. 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.
  8. 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. S2CID 33401607.
  9. Kervella, P.; Thévenin, F.; Di Folco, E.; Ségransan, D. (October 2004). "The angular sizes of dwarf stars and subgiants". 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.
  10. 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.
  11. Balona, L. A. (October 7, 2019). "Evidence for spots on hot stars suggests major revision of stellar physics". Monthly Notices of the Royal Astronomical Society. Oxford University Press (OUP). 490 (2): 2112–2116. arXiv:1910.01584. doi:10.1093/mnras/stz2808. ISSN 0035-8711. S2CID 203642124.
  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. S2CID 118345778.
  13. Reiners, A.; Royer, F. (February 2004). "First signatures of strong differential rotation in A-type stars". Astronomy & Astrophysics. 415 (1): 325–329. arXiv:astro-ph/0311341. Bibcode:2004A&A...415..325R. doi:10.1051/0004-6361:20034175. eISSN 1432-0746. ISSN 0004-6361. S2CID 15726297.
  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 170384". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved June 5, 2023.
  16. 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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