33 Piscium

33 Piscium
	; The narrow triangle in which this comparative star, in apparent magnitude (brightness viewed from Earth), figures. Click to show context
Observation data; Epoch J2000 Equinox J2000
Constellation	Pisces
Right ascension	00h 05m 20.14193s
Declination	−05° 42′ 27.4279″
Apparent magnitude (V)	4.61
Characteristics
Spectral type	K0 IIIb
Apparent magnitude (U)	6.52
Apparent magnitude (B)	5.65
Apparent magnitude (R)	3.83
Apparent magnitude (I)	3.29
Apparent magnitude (J)	2.89
Apparent magnitude (H)	2.31
Apparent magnitude (K)	2.21
B−V color index	1.029±0.037
Variable type	RS CVn
Astrometry
Radial velocity (Rv)	−6.56±0.23 km/s
Proper motion (μ)	RA: −6.54 mas/yr ; Dec.: 87.85 mas/yr
Parallax (π)	25.32 ± 0.53 mas
Distance	129 ± 3 ly ; (39.5 ± 0.8 pc)
Absolute magnitude (MV)	1.63
Orbit
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
Mass	0.83±0.22 M☉
Radius	7 R☉
Luminosity	24 L☉
Surface gravity (log g)	2.620±0.11 cgs
Temperature	4,736±92 K
Metallicity [Fe/H]	−0.12±0.05 dex
Rotational velocity (v sin i)	0.0 km/s
Age	4.8+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, GCRV 36, GSC 04669-00996, 2MASS J00052013-0542275
Database references
SIMBAD	data

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]

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

^ ^a ^b ^c ^d ^e ^f 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, S2CID 18759600.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ 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.
^ ^a ^b ^c ^d ^e 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, S2CID 118081703.
^ ^a ^b 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, S2CID 59451347, A61.
^ 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, S2CID 119257644.
^ ^a ^b Harper, W. E. (October 1926), "Two K-type spectroscopic binaries", Publications of the Dominion Observatory Ottawa, 3: 341–348, Bibcode:1926PDAO....3..341H.
^ ^a ^b ^c ^d 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, S2CID 118675933, 40.
^ ^a ^b ^c ^d ^e 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, S2CID 121883397.
^ "33 Psc". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-03-12.
^ 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.
^ 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.