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CQ Ursae Majoris
	; A visual band light curve for CQ Ursae Majoris, adapted from Mikulášek and Žižňovský (2001)
Observation data; Epoch J2000 Equinox J2000
Constellation	Ursa Major
Right ascension	13h 40m 21.385s
Declination	+57° 12′ 27.37″
Apparent magnitude (V)	6.28 to 6.30
Characteristics
Spectral type	A2IVpSrCr
Variable type	α2 CVn
Astrometry
Radial velocity (Rv)	−4.1±0.5 km/s
Proper motion (μ)	RA: −49.536 mas/yr ; Dec.: 25.759 mas/yr
Parallax (π)	11.0048 ± 0.0261 mas
Distance	296.4 ± 0.7 ly ; (90.9 ± 0.2 pc)
Details
Mass	2.02+0.14; −0.22 M☉
Radius	1.99±0.23 R☉
Luminosity	19.5+1.9; −1.7 L☉
Surface gravity (log g)	4.17+0.83; −0.46 cgs
Temperature	8,620±470 K
Metallicity [Fe/H]	−3.56±0.18 dex
Rotational velocity (v sin i)	35.8±3.8 km/s
Age	537+375; −338 Myr
Other designations
	CQ UMa, BD+57°1456, GC 18496, HD 119213, HIP 66700, HR 5153, SAO 28838, PPM 34137
Database references
SIMBAD	data

CQ Ursae Majoris is a variable star in the northern circumpolar constellation of Ursa Major, abbreviated CQ UMa. It is sometimes identified as HR 5153 from the Bright Star Catalogue or HD 119213 in the Henry Draper Catalogue; CQ UMa is the variable star designation. The star ranges in apparent visual magnitude from 6.28 to 6.30,^[3] which is bright enough to be dimly visible to the naked eye. It is located at a distance of 296 light years from the Sun based on parallax measurements.^[2]

This object was found to be a chemically peculiar star by W. P. Bidelman in 1964, with the spectrum showing strong lines of the element strontium.^[8] (This feature had been previously noted by W. E. Harper in 1937.)^[5] A. P. Cowley and C. R. Cowley found abnormalities in both strontium and chromium lines.^[8] In 1972, E. W. Burke, Jr. and J. T. Howard discovered the star is variable in luminosity with a period of 1.706 days.^[9] S. C. Wolff and N. D. Morrison in 1975 found a longer period of 2.451 days, double the earlier estimate.^[10]

W. K. Bonsack in 1974 noted peculiarities with the europium lines and found that the lines of ionized calcium and chromium are variable.^[11] Z. Mikulášek in 1978 showed that ionized europium lines varied in antiphase with the ionized chromium lines.^[5] In 1981, Y. V. Glagolevskij measured a large magnetic field of CQ UMa, interpreting it to be variable and reversing. Z. Mikulášek was able to fit the observations to an oblique rotator model with a concentration of europium-titanium close to the north magnetic pole, a patch of chromium-strontium near the southern pole, and a belt of enhanced iron along the magnetic equator.^[12]

CQ Ursae Majoris is classified as a Alpha² Canum Venaticorum variable with a stellar classification of A2IVpSrCr.^[4] This is a magnetic Ap star where the variability is modulated by the rotation period. It is spinning with a period of 2.449967 days and has an estimated age of approximately 537 million years. The star has double the mass and twice radius of the Sun. It is radiating 19.5 times the Sun's luminosity from its photosphere at an effective temperature of 8,620 K.^[6] The magnetic field of CQ UMa is inclined at an angle of 60°^+27°
_−26° and has a dipole field strength of roughly 2.6 kG.^[13]

References

^ Mikulášek, Z.; Žižňovský, J. (October 2001), "Further Improvement of the Period and New R Light Curve of CQ UMa" (PDF), Information Bulletin on Variable Stars, 5188 (1): 1, Bibcode:2001IBVS.5188....1M, retrieved 1 October 2022.
^ ^a ^b ^c ^d ^e Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
^ ^a ^b ^c Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
^ ^a ^b Abt, Helmut A.; Morrell, Nidia I. (1995), "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars", Astrophysical Journal Supplement, 99: 135, Bibcode:1995ApJS...99..135A, doi:10.1086/192182.
^ ^a ^b ^c Mikulasek, Z. (1979), "Line Identification List and Radial Velocity of the AP Star CQ UMa", Bulletin of the Astronomical Institute of Czechoslovakia, 30: 234, Bibcode:1979BAICz..30..234M.
^ ^a ^b Sikora, J.; et al. (February 2019), "A Volume-Limited Survey of mCP Stars Within 100pc I: Fundamental Parameters and Chemical Abundances", Monthly Notices of the Royal Astronomical Society, 483 (2): 2300–2324, arXiv:1811.05633, Bibcode:2019MNRAS.483.2300S, doi:10.1093/mnras/sty3105, S2CID 119089236.
^ "CQ UMa". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2022-09-30.
^ ^a ^b Cowley, Anne Pyne; Cowley, Charles R. (June 1965), "Slit Spectra of Some Peculiar and Metallic-Line A Stars", Publications of the Astronomical Society of the Pacific, 77 (456): 184, Bibcode:1965PASP...77..184C, doi:10.1086/128190, S2CID 34476280.
^ Burke, E. W. Jr.; Howard, J. T. (December 1972), "A newly discovered variable: the Ap star HR 5153", Astrophysical Journal, 178: 491, Bibcode:1972ApJ...178..491B, doi:10.1086/151808.
^ Wolff, S. C.; Morrison, N. D. (April 1975), "Photometry of six peculiar A-type stars", Publications of the Astronomical Society of the Pacific, 87: 231–236, Bibcode:1975PASP...87..231W, doi:10.1086/129748, S2CID 121308383.
^ Bonsack, Walter K. (August 1974), "Spectrum Variations in the Ap-Type Stars. I. A Survey of Stars Between 7^h and 19^h Right Ascension", Publications of the Astronomical Society of the Pacific, 86 (512): 408, Bibcode:1974PASP...86..408B, doi:10.1086/129624, S2CID 120741453.
^ Pyper, D. M.; Adelman, S. J. (March 1985), "Spectrophotometry of peculiar B and A stars. XVII. 63 Andromedae, HD 34452, epsilon Ursae Majoris, CQ Ursae Majoris, CU Virginis, CS Virginis and beta Coronae Borealis", Astronomy and Astrophysics Supplement Series, 59: 369–397, Bibcode:1985A&AS...59..369P.
^ Sikora, J.; et al. (March 2019), "A volume-limited survey of mCP stars within 100 pc II: rotational and magnetic properties", Monthly Notices of the Royal Astronomical Society, 483 (3): 3127–3145, arXiv:1811.05635, Bibcode:2019MNRAS.483.3127S, doi:10.1093/mnras/sty2895.

Mikulasek, Zdenek; et al. (June 2021), "CQ UMa – a slowly accelerating cool magnetic CP star", OBA Stars: Variability and Magnetic Fields. On-line conference, held 26–30 April 2021, p. 17, Bibcode:2021osvm.confE..17M, doi:10.5281/zenodo.5040838, 17.
Ziznovsky, Jozef; Mikulasek, Zdenek (October 1995), "Improvement of the Period of CQ UMa", Information Bulletin on Variable Stars, 4259: 1, Bibcode:1995IBVS.4259....1Z.
Mikulášek, Z. (1994), Zverko, J.; Ziznovsky, J. (eds.), "A two-component model of light variations for CQ UMa", Chemically peculiar and magnetic stars, Proceedings of the International Conference held in Tatranska Lomnica, Slovak Republic, September 6–10, 1993, Astronomical Institute, Slovak Academy of Sciences, p. 165, Bibcode:1994cpms.conf..165M.
Jetsu, L.; et al. (November 1992), "Long-term stability of the light curves of CQ Ursae Majoris", Astronomy and Astrophysics, 265: 547–554, Bibcode:1992A&A...265..547J.
Kokko, M.; Jetsu, L. (April 1992), "Long-term UBV photometry of CQ UMa", Annual Meeting of the Finnish Astronomical Society: 12–14, Bibcode:1992amfa.meet...12K.
Mikulasek, Z. (1988), Glagolevsky, Yu. V. (ed.), "A simple model of CQ UMa", Magnetic Stars, Proceedings of an International Meeting on the Problem: "Physics and Evolution of Stars", held in Nizny Arkhyz, October 12–17, 1987, Leningrad: Nauka, p. 67, Bibcode:1988mast.conf...67M.
Mikulasek, Zdenek (April 1987), "An Improvement of the Rotational Period of CQ UMa", Information Bulletin on Variable Stars, 3010: 1, Bibcode:1987IBVS.3010....1M.
Pavlovski, K. (July 1979), "The light variations of the Ap star CQ UMa", Astronomy and Astrophysics, 76: 362–364, Bibcode:1979A&A....76..362P.
Mikulasek, Z.; et al. (1978), "Photoelectric Photometry at the Hvar Observatory. III. The AP Star CQ UMa", Bulletin of the Astronomical Institute of Czechoslovakia, 29: 44, Bibcode:1978BAICz..29...44M.
Mikulasek, Z.; Grygar, J. (1978), "Preliminary Analysis of the Ap - star CQ UMa", Hvar Observatory Bulletin, 2 (1): 1, Bibcode:1978HvaOB...2....1M.
Mikulasek, Z. (1976), "Rotational velocity and the light variations period of HR 5153", Astronomische Nachrichten, 297 (5): 245–247, Bibcode:1976AN....297..245M, doi:10.1002/asna.19762970506.
Mikulasek, Z. (May 1975), "Improved Period of the Ap Variable HR 5153", Information Bulletin on Variable Stars, 1003: 1, Bibcode:1975IBVS.1003....1M.