2 Piscis Austrini

2 Piscis Austrini, also known as HD 200763 or simply 2 PsA, is a solitary orange hued star[18] located in the southern constellation Microscopium. It was once part of Piscis Austrinus, the southern fish. The object has an apparent magnitude of 5.2,[2] making it faintly visible to the naked eye under ideal conditions. Based on parallax measurements from the Gaia satellite, it is estimated to be 354 light years away from the Solar System.[1] However, it is receding with a poorly constrained heliocentric radial velocity of 3.1 km/s.[7] At its current distance, 2 PsA's brightness is diminished by 0.11 magnitudes due to interstellar dust.[19] It has an absolute magnitude of 0.19.[8]

2 Piscis Austrini
Location of 2 PsA (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Microscopium
Right ascension 21h 06m 24.67730s[1]
Declination −32° 20′ 29.8282″[1]
Apparent magnitude (V) 5.20±0.01[2]
Characteristics
Evolutionary stage horizontal branch[3]
Spectral type K2 III[4] or K3 III[5]
B−V color index +1.10[6]
Astrometry
Radial velocity (Rv)3.1±2.8[7] km/s
Proper motion (μ) RA: −5.949 mas/yr[1]
Dec.: +7.786 mas/yr[1]
Parallax (π)9.2085 ± 0.0973 mas[1]
Distance354 ± 4 ly
(109 ± 1 pc)
Absolute magnitude (MV)+0.19[8]
Details
Mass2.36[9] M☉
Radius16.4[10] R☉
Luminosity122±2[11] L☉
Surface gravity (log g)2.88±0.15[12] cgs
Temperature4,632±24[13] K
Metallicity [Fe/H]−0.01[14] dex
Rotational velocity (v sin i)<1.2[15] km/s
Age930[9] Myr
Other designations
2 PsA, 49 G. Microscopii[16], CD−32°16398, CPD−32°6288, GC 29465, HD 200763, HIP 104174, HR 8076, SAO 212716[17]
Database references
SIMBADdata

This is an evolved star with a stellar classification of either K2 III or K3 III.[4][5] Nevertheless, both indicate that the object is a red giant. 2 PsA is estimated to be 930 million years old,[9] enough time for it to cool and expand to 16.4 times the Sun's radius.[10] It is currently on the horizontal branch (HB), generating energy through helium fusion at its core.[3] The star is located in a metal rich region of the HB called the red clump. At present 2 PsA has 2.36 times the mass of the Sun and is radiating 122 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,632 K.[13] 2 PsA has a solar metallicity and spins slowly with a projected rotational velocity lower than 1.2 km/s.[15]

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. Alves, David R. (20 August 2000). "K‐Band Calibration of the Red Clump Luminosity". The Astrophysical Journal. 539 (2): 732–741. arXiv:astro-ph/0003329. Bibcode:2000ApJ...539..732A. doi:10.1086/309278. eISSN 1538-4357. ISSN 0004-637X. S2CID 16673121.
  4. Houk, N. (1982). Michigan Catalogue of Two-dimensional Spectral Types for the HD stars. Volume III: Declinations −40° to −26°. Bibcode:1982mcts.book.....H.
  5. Hofleit, Dorrit (June 1943). "Spectroscopic absolute magnitudes of 365 southern K-type stars". Harvard College Observatory Circular. 449: 1–11. Bibcode:1943HarCi.449....1H.
  6. Lake, R. (1965). "Photometric Magnitudes and Colours for Bright Southern Stars (Sixth List)". Monthly Notes of the Astronomical Society of South Africa. 24: 41. Bibcode:1965MNSSA..24...41L. ISSN 0024-8266.
  7. 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.
  8. 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.
  9. Demarque, Pierre; Woo, Jong‐Hak; Kim, Yong‐Cheol; Yi, Sukyoung K. (December 2004). "Y'2 Isochrones with an Improved Core Overshoot Treatment". The Astrophysical Journal Supplement Series. 155 (2): 667–674. Bibcode:2004ApJS..155..667D. doi:10.1086/424966. eISSN 1538-4365. ISSN 0067-0049.
  10. 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.
  11. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  12. Gomes da Silva, J.; Santos, N. C.; Adibekyan, V.; Sousa, S. G.; Campante, T. L.; Figueira, P.; Bossini, D.; Delgado-Mena, E.; Monteiro, M. J. P. F. G.; de Laverny, P.; Recio-Blanco, A.; Lovis, C. (February 2021). "Stellar chromospheric activity of 1674 FGK stars from the AMBRE-HARPS sample". Astronomy & Astrophysics. 646: A77. arXiv:2012.10199. Bibcode:2021A&A...646A..77G. doi:10.1051/0004-6361/202039765. eISSN 1432-0746. ISSN 0004-6361.
  13. Luck, R. Earle (25 August 2015). "Abundances in the Local Region. I. G and K Giants". The Astronomical Journal. 150 (3): 88. arXiv:1507.01466. Bibcode:2015AJ....150...88L. doi:10.1088/0004-6256/150/3/88. eISSN 1538-3881. ISSN 0004-6256. S2CID 118505114.
  14. McWilliam, Andrew (December 1990). "High-resolution spectroscopic survey of 671 GK giants. I - Stellar atmosphere parameters and abundances". The Astrophysical Journal Supplement Series. 74: 1075. Bibcode:1990ApJS...74.1075M. doi:10.1086/191527. eISSN 1538-4365. ISSN 0067-0049.
  15. 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". Astronomy & Astrophysics. 561: A126. arXiv:1312.3474. Bibcode:2014A&A...561A.126D. doi:10.1051/0004-6361/201220762. eISSN 1432-0746. ISSN 0004-6361.
  16. 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.
  17. "HD 200763". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-04-08.
  18. 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.
  19. 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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