HD 154556

HD 154556, also known as HR 6357, is a solitary orange-hued star located in the southern circumpolar constellation Apus. It has an apparent magnitude of 6.21,[2] placing it near the limit for naked eye visibility. The star is located relatively close at a distance of 228 light years based on Gaia DR3 parallax measurements,[1] but it is drifter closer with a heliocentric radial velocity of −24 km/s.[5] At its current distance, HD 154556's brightness is diminished by 0.26 magnitudes due to interstellar dust.[14] It has an absolute magnitude of +2.10.[6]

HD 154556
location of HD 154556 in red
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Apus
Right ascension 17h 12m 19.93421s[1]
Declination −70° 43′ 15.8963″[1]
Apparent magnitude (V) 6.21±0.01[2]
Characteristics
Evolutionary stage subgiant
Spectral type K1 IV CN3[3]
U−B color index +1.04[4]
B−V color index +1.06[4]
Astrometry
Radial velocity (Rv)−24±0.4[5] km/s
Proper motion (μ) RA: +49.060 mas/yr[1]
Dec.: −78.104 mas/yr[1]
Parallax (π)14.3386 ± 0.0224 mas[1]
Distance227.5 ± 0.4 ly
(69.7 ± 0.1 pc)
Absolute magnitude (MV)+2.10[6]
Details
Mass1.25[7] M☉
Radius6.35±0.32[8] R☉
Luminosity19.7±0.1[1] L☉
Surface gravity (log g)2.90±0.25[9] cgs
Temperature4,677[10] K
Metallicity [Fe/H]+0.04±0.09[9] dex
Rotational velocity (v sin i)<1[11] km/s
Age3.52+0.36
−0.37[1] Gyr
Other designations
55 G. Apodis[12], CD−70°1498, CPD−70°2361, GC 23140, HD 154556, HIP 84158, HR 6357, SAO 257472[13]
Database references
SIMBADdata

HD 154556 has a stellar classification of K1 IV CN3,[3] indicating that it is an evolved K-type subgiant with a moderate abundance of cyano radicals in its spectrum, making it a CN star. It has 1.25 times the mass of the Sun[7] and is calculated to be 3.52 billion years old,[1] having expanded to 6.35 times the radius of the Sun.[8] It now radiates 19.7 times the luminosity of the Sun[1] from its enlarged photosphere at an effective temperature of 4,677 K.[10] It has a near solar metallicity[9] and spins slowly with a projected rotational velocity lower than 1 km/s.[11]

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. 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.
  8. 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.
  9. Randich, S.; Gratton, R.; Pallavicini, R.; Pasquini, L.; Carretta, E. (August 1999). "Lithium in population I subgiants". Astronomy and Astrophysics. 348: 487–500. Bibcode:1999A&A...348..487R. ISSN 0004-6361.
  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. 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. arXiv:1312.3474. Bibcode:2014A&A...561A.126D. doi:10.1051/0004-6361/201220762. eISSN 1432-0746. ISSN 0004-6361. S2CID 54046583.
  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 154556". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 20 September 2015.
  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.
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