Astronomy:HD 170521

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Short description: Distant K-type giant; Corona Australis
HD 170521
Corona Australis constellation map.svg
Red circle.svg
Location of HD 170521 (circled)
Observation data
Epoch J2000.0   Equinox (celestial coordinates)
Constellation Corona Australis
Right ascension  18h 31m 56.22382s[1]
Declination −43° 30′ 26.5714″[1]
Apparent magnitude (V) 5.69±0.01[2]
Characteristics
Spectral type K2 III[3]
B−V color index +1.34[4]
Astrometry
Radial velocity (Rv)7.2±0.4[5] km/s
Proper motion (μ) RA: −1.328[1] mas/yr
Dec.: −8.795[1] mas/yr
Parallax (π)2.1538 ± 0.1596[1] mas
Distance1,500 ± 100 ly
(460 ± 30 pc)
Absolute magnitude (MV)−1.90[6]
Details
Mass1.55[7] M☉
Radius78.6±4.1[8] R☉
Luminosity934[9] L☉
Surface gravity (log g)0.96[10] cgs
Temperature4,474±122[11] K
Metallicity [Fe/H]−0.49[7] dex
Rotational velocity (v sin i)6.5±1[12] km/s
Other designations
CD−43°12600, CPD−34°8647, GC 25272, HD 170521, HIP 90842, HR 6937, SAO 229094[13]
Database references
SIMBADdata

HD 170521, also known as HR 6937 or rarely 12 G. Coronae Australis, is a solitary star[14] located in the southern constellation Corona Australis. It is faintly visible to the naked eye as an orange-hued point of light with an apparent magnitude of 5.69.[2] The object is located relatively far at a distance of approximately 1,500 light years based on Gaia DR3 parallax measurements,[1] and it is receding with a heliocentric radial velocity of 7.2 km/s.[5] At its current distance, HD 170521's brightness is heavily diminished by 0.46 magnitudes due to extinction from interstellar dust[15] and it has an absolute magnitude of −1.90.[6]

HD 170521 has a stellar classification of K2 III,[3] indicating that it is an evolved red giant. It has 1.55 times the mass of the Sun[7] but it has expanded to 78.6 times the Sun's radius.[8] The object radiates 934 times the luminosity of the Sun[9] from its enlarged photosphere at an effective temperature of 4,474 K.[11] HD 170521 is metal deficient with an iron abundance only 32.4% that of the Sun (Fe/H) = −0.49[7] and it spins modestly with a projected rotational velocity of 6.5 km/s.[12]

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  2. ↑ 2.0 2.1 Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P. et al. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics 355: L27–L30. ISSN 0004-6361. Bibcode: 2000A&A...355L..27H. 
  3. ↑ 3.0 3.1 Houk, Nancy (1978). Michigan catalogue of two-dimensional spectral types for the HD stars: Declinations −53° to −40°. 2. Bibcode: 1978mcts.book.....H. 
  4. ↑ 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. ISSN 0024-8266. Bibcode: 1968MNSSA..27...11C. 
  5. ↑ 5.0 5.1 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. doi:10.1134/S1063773706110065. ISSN 1063-7737. Bibcode: 2006AstL...32..759G. 
  6. ↑ 6.0 6.1 Anderson, E.; Francis, Ch. (May 2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331–346. doi:10.1134/S1063773712050015. ISSN 1063-7737. Bibcode: 2012AstL...38..331A. 
  7. ↑ 7.0 7.1 7.2 7.3 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. doi:10.1051/0004-6361/201935765. ISSN 0004-6361. Bibcode: 2019A&A...628A..94A. 
  8. ↑ 8.0 8.1 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. doi:10.1051/0004-6361:20035930. ISSN 0004-6361. Bibcode: 2004A&A...426..297K. 
  9. ↑ 9.0 9.1 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. doi:10.1111/j.1365-2966.2012.21873.x. ISSN 0035-8711. Bibcode: 2012MNRAS.427..343M. 
  10. ↑ McDonald, I.; Zijlstra, A. A.; Watson, R. A. (15 June 2017). "Fundamental parameters and infrared excesses of Tycho–Gaia stars". Monthly Notices of the Royal Astronomical Society 471 (1): 770–791. doi:10.1093/mnras/stx1433. ISSN 0035-8711. Bibcode: 2017MNRAS.471..770M. 
  11. ↑ 11.0 11.1 Stassun, Keivan G. et al. (9 September 2019). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal 158 (4): 138. doi:10.3847/1538-3881/ab3467. Bibcode: 2019AJ....158..138S. 
  12. ↑ 12.0 12.1 De Medeiros, J. R.; Alves, S.; Udry, S.; Andersen, J.; Nordström, B.; Mayor, M. (January 2014). "A catalog of rotational and radial velocities for evolved stars V: Southern stars *". Astronomy & Astrophysics 561: A126. doi:10.1051/0004-6361/201220762. ISSN 0004-6361. Bibcode: 2014A&A...561A.126D. 
  13. ↑ "HD 170521". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+170521. 
  14. ↑ 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. doi:10.1111/j.1365-2966.2008.13596.x. ISSN 0035-8711. Bibcode: 2008MNRAS.389..869E. 
  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. doi:10.1093/mnras/stx2219. ISSN 0035-8711. Bibcode: 2017MNRAS.472.3805G. 
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