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.^[3] The annual parallax shift seen from Earth's orbit is 8.5 mas, which provides a distance estimate of about 384 light years. It is moving away from the Sun with a radial velocity of around +9 km/s.^[6]

28 Cancri

A light curve for CX Cancri, plotted from TESS data[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Cancer
Right ascension	08h 28m 36.78530s[2]
Declination	+24° 08′ 41.7179″[2]
Apparent magnitude (V)	6.05[3]
Characteristics
Spectral type	F0 Vn[4]
U−B color index	+0.13[3]
B−V color index	+0.22[3]
Variable type	δ Sct[5]
Astrometry
Radial velocity (Rv)	+9.0±4.3[6] km/s
Proper motion (μ)	RA: −30.946[2] mas/yr Dec.: −39.719[2] mas/yr
Parallax (π)	8.4885 ± 0.1539 mas[2]
Distance	384 ± 7 ly (118 ± 2 pc)
Absolute magnitude (MV)	0.41[7]
Details
Mass	2.36±0.11[8] M☉
Radius	3.7[2] R☉
Luminosity	44[2] L☉
Surface gravity (log g)	3.61[2] cgs
Temperature	7,516+52 −103[8] K
Metallicity [Fe/H]	+0.16[9] dex
Rotational velocity (v sin i)	133[8] km/s
Age	737[2] Myr
Other designations
28 Cnc, CX Cnc, BD+24°1931, HD 71496, HIP 41574, HR 3329, SAO 80204[10]
Database references
SIMBAD	data

Based upon proper motion variation, this is an astrometric binary system with high likelihood (99.8%).^[11] The visible component has a stellar classification of F0 Vn,^[4] indicating it is a F-type main-sequence star with "nebulous" lines due to rapid rotation.

In 1973, John R Percy announced that 28 Cancri might be a variable star.^[12] Stephen John Horan et al. confirmed that the star's brightness varies, in 1974.^[13] In 1979, it was given its variable star designation.^[14] It is a Delta Scuti variable star with a period of 0.0960 days and an amplitude of 0.020 in magnitude.^[15] With 2.4 times the mass of the Sun it is spinning with a high projected rotational velocity of 133 km/s. 28 Cancri is radiating roughly 44 times the Sun's luminosity from its photosphere at an effective temperature of around 7,516 K.

References

1. "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
2. 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.
3. 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.
4. 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.
5. 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, S2CID 118560311.
6. 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.
7. 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.
8. Zorec, J.; Royer, F. (2012), "Rotational velocities of A-type stars. IV. Evolution of rotational velocities", Astronomy & Astrophysics, 537: A120, arXiv:1201.2052, Bibcode:2012A&A...537A.120Z, doi:10.1051/0004-6361/201117691, S2CID 55586789, A120.
9. Netopil, Martin (4 May 2017). "Metallicity calibrations for dwarf stars and giants in the Geneva photometric system". Monthly Notices of the Royal Astronomical Society. 469 (3): 3042–3055. arXiv:1705.00883. Bibcode:2017MNRAS.469.3042N. doi:10.1093/mnras/stx1077. eISSN 1365-2966. ISSN 0035-8711.
10. "28 Cnc". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-02-09.
11. 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, S2CID 14010423.
12. Percy, John R. (June 1973). "A Search for Delta Scuti Stars". Journal of the Royal Astronomical Society of Canada. 67: 139–141. Bibcode:1973JRASC..67..139P. Retrieved 31 December 2024.
13. Horan, S. J.; Michael, J. L.; Seeds, M. A. (June 1974). "Possible Beats in Two delta Scuti Stars" (PDF). Information Bulletin on Variable Stars. 896: 1. Bibcode:1974IBVS..896....1H. Retrieved 31 December 2024.
14. Kholopov, P. N.; Kukarkina, N. P.; Perova, N. B. (April 1979). "64th Name-List of Variable Stars" (PDF). Information Bulletin on Variable Stars. 1581: 1–8. Bibcode:1979IBVS.1581....1K. Retrieved 31 December 2024.
15. Rodríguez, E.; et al. (June 2000), "A revised catalogue of δ Sct stars", Astronomy and Astrophysics Supplement, 144 (3): 469–474, Bibcode:2000A&AS..144..469R, doi:10.1051/aas:2000221, hdl:10261/226673.