33 Piscium

33 Piscium is a binary star system in the zodiac constellation of Pisces. It is visible to the naked eye with an apparent visual magnitude of 4.61.[2] The distance to this system, as determined from an annual parallax shift of 25.32±0.53 mas,[1] is about 129 light years. It is moving closer to the Sun with a heliocentric radial velocity of −6.6 km/s.[4]

33 Piscium
Observation data
Epoch J2000      Equinox J2000
Constellation Pisces
Right ascension  00h 05m 20.14193s[1]
Declination −05° 42′ 27.4279″[1]
Apparent magnitude (V) 4.61[2]
Characteristics
Spectral type K0 IIIb[3]
Apparent magnitude (U) 6.52[2]
Apparent magnitude (B) 5.65[2]
Apparent magnitude (R) 3.83[2]
Apparent magnitude (I) 3.29[2]
Apparent magnitude (J) 2.89[2]
Apparent magnitude (H) 2.31[2]
Apparent magnitude (K) 2.21[2]
B−V color index 1.029±0.037
Variable type RS CVn[3]
Astrometry
Radial velocity (Rv)−6.56±0.23[4] km/s
Proper motion (μ) RA: −6.54[1] mas/yr
Dec.: 87.85[1] mas/yr
Parallax (π)25.32 ± 0.53[1] mas
Distance129 ± 3 ly
(39.5 ± 0.8 pc)
Absolute magnitude (MV)1.63[5]
Orbit[6]
Period (P)72.93 d
Eccentricity (e)0.272±0.017
Periastron epoch (T)2,422,530.330±0.809 JD
Argument of periastron (ω)
(secondary)		337.71±4.60°
Semi-amplitude (K1)
(primary)		16.43±0.31 km/s
Details[7]
Mass0.83±0.22 M☉
Radius7[8] R☉
Luminosity24[8] L☉
Surface gravity (log g)2.620±0.11 cgs
Temperature4,736±92 K
Metallicity [Fe/H]−0.12±0.05 dex
Rotational velocity (v sin i)0.0[8] km/s
Age4.8+3.3
−1.2 Myr
Other designations
33 Psc, BC Psc, BD−06° 6357, FK5 1002, GC 59, HD 28, HIP 443, HR 3, SAO 128572, PPM  181831, GSC 04669-00996, 2MASS J00052013-0542275[9]
Database references
SIMBADdata

This system was found to have a variable radial velocity by Leah Allen and Adelaide Hobe of Lick Observatory in 1911.[10] It was identified as a single-lined spectroscopic binary, and the orbital elements were published by Canadian astronomer W. E. Harper in 1926.[3] The pair have an orbital period of 72.93 days and an eccentricity of 0.27.[6] This is a RS Canum Venaticorum variable,[3] indicating a close binary system with active star spots, and has the variable star designation BC Psc.[11]

The primary, component A, is a first-ascent red giant with a stellar classification of K0 IIIb, having chemical abundances that match a first dredge-up mixing model. Pourbaix & Boffin (2003) estimated the mass of the primary as 1.7±0.4 M☉ and the secondary as 0.76±0.11 M☉.[3] However, Feuillet et al. (2016) derived a much lower mass estimate of 0.83±0.22 M☉ for the primary.[7] At the age of roughly five[7] billion years, the star has expanded to 7 times the radius of the Sun.[8] It is radiating 24[8] times the Sun's luminosity from its photosphere at an effective temperature of about 4,736 K.[7]

References
  1. van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357.
  2. Ducati, J. R. (2002), "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system", VizieR On-line Data Catalog, 2237, Bibcode:2002yCat.2237....0D.
  3. Barisevičius, G.; et al. (2011), "Chemical Composition of the RS CVn-type Star 33 Piscium", Baltic Astronomy, 20: 53–63, arXiv:1105.5650, Bibcode:2011BaltA..20...53B, doi:10.1515/astro-2017-0268.
  4. de Bruijne, J. H. J.; Eilers, A.-C. (October 2012), "Radial velocities for the HIPPARCOS-Gaia Hundred-Thousand-Proper-Motion project", Astronomy & Astrophysics, 546: 14, arXiv:1208.3048, Bibcode:2012A&A...546A..61D, doi:10.1051/0004-6361/201219219, A61.
  5. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015.
  6. Harper, W. E. (October 1926), "Two K-type spectroscopic binaries", Publications of the Dominion Observatory Ottawa, 3: 341–348, Bibcode:1926PDAO....3..341H.
  7. Feuillet, Diane K.; et al. (2016), "Determining Ages of APOGEE Giants with Known Distances", The Astrophysical Journal, 817 (1): 15, arXiv:1511.04088, Bibcode:2016ApJ...817...40F, doi:10.3847/0004-637X/817/1/40, 40.
  8. Massarotti, Alessandro; et al. (January 2008), "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209.
  9. "33 Psc". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-03-12.
  10. Campbell, William Wallace; et al. (1911), "Sixty-eight stars whose radial velocities vary", Lick Observatory Bulletin, 199: 140–154, Bibcode:1911LicOB...6..140C, doi:10.5479/ADS/bib/1911LicOB.6.140C.
  11. Kazarovets, E. V.; Samus, N. N. (October 1990), "The 70th Name-List of Variable Stars", Information Bulletin on Variable Stars, 3530: 1, Bibcode:1990IBVS.3530....1K.
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