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3 Piscis Austrini

Location of 3 PsA (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Microscopium
Right ascension	21 13 17.32730
Declination	−27° 37′ 09.7106″
Apparent magnitude (V)	5.39±0.01
Characteristics
Spectral type	K3 III
B−V color index	+1.42
Astrometry
Radial velocity (Rv)	−46.2±2.4 km/s
Proper motion (μ)	RA: +98.513 mas/yr Dec.: −110.906 mas/yr
Parallax (π)	8.0734 ± 0.1733 mas
Distance	404 ± 9 ly (124 ± 3 pc)
Absolute magnitude (MV)	+0.19
Details
Mass	1.58 M☉
Radius	31.3±1.6 R☉
Luminosity	184 −8 L☉
Surface gravity (log g)	1.86 cgs
Temperature	4,225±123 K
Metallicity	−0.17 dex
Rotational velocity (v sin i)	<1 km/s
Age	2.59 −1.90 Gyr
Other designations
3 PsA, 58 G. Microscopii[12], CD−28°17178, CPD−28°7411, FK5 1556, GC 29652, HD 201901, HIP 104750, HR 8110, SAO 190129
Database references
SIMBAD	data

3 Piscis Austrini, also known as HD 201901 or simply 3 PsA, is an astrometric binary (100% chance) located in the southern constellation Microscopium. It was once part of Piscis Austrinus, the southern fish. The system has a combined apparent magnitude of 5.39, making it faintly visible to the naked eye under ideal conditions. Gaia DR3 parallax measurements imply a distance of 404 light years and it is currently approaching the Solar System with a heliocentric radial velocity of −46.2 km/s. At its current distance, 3 PsA's brightness is diminished by 0.12 magnitudes due to extinction from interstellar dust and it has an absolute magnitude of +0.19.

The visible component is an evolved red giant with a stellar classification of K3 III. The interferometry-measured angular diameter of the star, after correcting for limb darkening, is 2.03±0.04 mas, which, at its estimated distance, equates to a physical radius of about 20 times the radius of the Sun. However, its actual empirical radius is 31.3 R_☉. It has 1.58 times the mass of the Sun and is radiating 184 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,225 K. 3 PsA is metal deficient with an iron abundance 68% that of the Sun ( = −0.17) and it spins too slowly for its projected rotational velocity to be measured accurately. It is estimated to be 2.59 billion years old based on Gaia DR3 models.

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. ^ Houk, N. (1982). Michigan Catalogue of Two-dimensional Spectral Types for the HD stars. Volume III: Declinations −40° to −26°. Bibcode:1982mcts.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. S2CID 131780028.
8. ^ Kervella, P.; Thévenin, F.; Di Folco, E.; Ségransan, D. (October 2004). "The angular sizes of dwarf stars and subgiants. Surface brightness relations calibrated by interferometry". 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. S2CID 6077801.
9. ^ 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.
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. ^ 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 201901". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-04-11.
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. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. eISSN 1365-2966. ISSN 0035-8711. S2CID 14878976.
15. Frankowski, A.; Jancart, S.; Jorissen, A. (19 December 2006). "Proper-motion binaries in the Hipparcos catalogue: Comparison with radial velocity data". Astronomy & Astrophysics. 464 (1): 377–392. arXiv:astro-ph/0612449. Bibcode:2007A&A...464..377F. doi:10.1051/0004-6361:20065526. eISSN 1432-0746. ISSN 0004-6361. S2CID 14010423.
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.
17. Richichi, A.; Percheron, I.; Khristoforova, M. (February 2005). "CHARM2: An updated Catalog of High Angular Resolution Measurements". Astronomy & Astrophysics. 431 (2): 773–777. Bibcode:2005A&A...431..773R. doi:10.1051/0004-6361:20042039. eISSN 1432-0746. ISSN 0004-6361. S2CID 122267643.
18. Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R_*) is given by:

    ${\displaystyle {\begin{aligned}2\cdot R_{*}&={\frac {(10^{-3}\cdot 93.6\cdot 2.03)\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 40.9\cdot R_{\bigodot }\end{aligned}}}$

v t e Constellation of Microscopium
List of stars in Microscopium Microscopium in Chinese astronomy
Stars	Bayer α β γ δ ε ζ η θ θ ι ν Flamsteed 2 PsA 3 PsA Variable R S T U AT AU AV AX BO DD HR 7817 7893 7909 7933 7971 7987 8046 8100 8104 8108 8200 8202 HD 202628 Other PSR J2124−3358 WASP-7
Exoplanets WASP-7b
Galaxies	NGC 6925 7012 7057 7060 Other ESO 286-19
Category

• K-type giants
• Astrometric binaries
• Microscopium
• Durchmusterung objects
• Flamsteed objects
• Henry Draper Catalogue objects
• Hipparcos objects
• Bright Star Catalogue objects
• Gould objects