28 Cancri

28 Cancri is a star system in the zodiac constellation of Cancer. It is a variable star with the designation CX Cancri, and is close to the lower limit of visibility with the naked eye, having a mean apparent visual magnitude of 6.05.[2] The annual parallax shift seen from Earth's orbit is 7.32 mas, which provides a distance estimate of about 450 light years. It is moving away from the Sun with a radial velocity of around +9 km/s.[5]

28 Cancri
Observation data
Epoch J2000      Equinox J2000
Constellation Cancer
Right ascension  08h 28m 36.78559s[1]
Declination +24° 08′ 41.7194″[1]
Apparent magnitude (V) 6.05[2]
Characteristics
Spectral type F0 Vn[3]
U−B color index +0.13[2]
B−V color index +0.22[2]
Variable type δ Sct[4]
Astrometry
Radial velocity (Rv)+9.0±4.3[5] km/s
Proper motion (μ) RA: −29.07[1] mas/yr
Dec.: −52.84[1] mas/yr
Parallax (π)7.32 ± 0.92[1] mas
Distanceapprox. 450 ly
(approx. 140 pc)
Absolute magnitude (MV)0.41[6]
Details
Mass2.36±0.11[7] M☉
Luminosity65.3+21.2
−16.0[7] L☉
Temperature7,516+52
−103[7] K
Rotational velocity (v sin i)133[7] km/s
Other designations
28 Cnc, CX Cnc, BD+24° 1931, HD 71496, HIP 41574, HR 3329, SAO 80204[8]
Database references
SIMBADdata

Based upon proper motion variation, this is an astrometric binary system with high likelihood (99.8%).[9] The visible component has a stellar classification of F0 Vn,[3] indicating it is a F-type main-sequence star with "nebulous" lines due to rapid rotation. It is a Delta Scuti variable star with a period of 0.0960 days and an amplitude of 0.020 in magnitude.[10] With 2.4[7] times the mass of the Sun it is spinning with a high projected rotational velocity of 133 km/s.[7] 28 Cancri is radiating roughly 65[7] times the Sun's luminosity from its photosphere at an effective temperature of around 7,516 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. Oja, T. (August 1991), "UBV photometry of stars whose positions are accurately known. VI", Astronomy and Astrophysics Supplement Series, 89 (2): 415–419, Bibcode:1991A&AS...89..415O.
  3. Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819.
  4. Dubath, P.; et al. (2011), "Random forest automated supervised classification of Hipparcos periodic variable stars", Monthly Notices of the Royal Astronomical Society, 414 (3): 2602–2617, arXiv:1101.2406, Bibcode:2011MNRAS.414.2602D, doi:10.1111/j.1365-2966.2011.18575.x.
  5. 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.
  6. 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.
  7. Zorec, J.; Royer, F. (2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691, A120.
  8. "28 Cnc". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-02-09.
  9. Frankowski, A.; et al. (March 2007), "Proper-motion binaries in the Hipparcos catalogue. Comparison with radial velocity data", Astronomy and Astrophysics, 464 (1): 377–392, arXiv:astro-ph/0612449, Bibcode:2007A&A...464..377F, doi:10.1051/0004-6361:20065526.
  10. Rodríguez, E.; et al. (June 2000), "A revised catalogue of δ Sct stars", Astronomy and Astrophysics Supplement, 144: 469–474, Bibcode:2000A&AS..144..469R, doi:10.1051/aas:2000221.
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