4 Canum Venaticorum

4 Canum Venaticorum is a binary star system in the northern constellation of Canes Venatici, located around 425 light years away.[1] It has the variable star designation AI Canum Venaticorum; 4 Canum Venaticorum is its Flamsteed designation. Its brightness varies from magnitude +5.89 to +6.15 with a period of 2.8 hours,[3] which places it around the lower limit of visibility to the naked eye. This was found to be a binary by Schmid et al. in 2014, based on periodic, non-sinusoidal changes in its radial velocity. It is a single-lined spectroscopic binary with an orbital period of 124.4 days and an eccentricity of 0.31.[2]

4 Canum Venaticorum
Observation data
Epoch J2000      Equinox J2000
Constellation Canes Venatici
Right ascension  20h 01m 47.01149s[1]
Declination +64° 49′ 33.8670″[1]
Apparent magnitude (V) +6.04[2] 5.89 to 6.15[3]
Characteristics
Spectral type F3 IV[4] or F0 III[5]
B−V color index 0.366±0.005[6]
Variable type δ Sct[7]
Astrometry
Radial velocity (Rv)−0.3±2.9[2] km/s
Proper motion (μ) RA: −79.651[1] mas/yr
Dec.: +13.203[1] mas/yr
Parallax (π)7.6829 ± 0.0960[1] mas
Distance425 ± 5 ly
(130 ± 2 pc)
Absolute magnitude (MV)+0.75[8]
Orbit[2]
Period (P)124.44±0.03 d
Eccentricity (e)0.311±0.003
Periastron epoch (T)2454605±10.3 JD
Argument of periastron (ω)
(secondary)		70.2±0.7°
Semi-amplitude (K1)
(primary)		13.24±0.05 km/s
Details[2]
4 CVn A
Mass1.0–2.0 M☉
Radius3.7–4.1 R☉
Luminosity295+3.6
−3.2 L☉
Surface gravity (log g)3.30±0.35 cgs
Temperature6,875±120 K
Metallicity [Fe/H]−0.05±0.15 dex
Rotational velocity (v sin i)109±3 km/s
Other designations
4 CVn, AI Canum Venaticorum, BD+43°2218, FK5 2993, GC 16899, HD 107904, HIP 60467, HR 4715, SAO 44155[9]
Database references
SIMBADdata

The primary component is an evolved F-type star with a stellar classification of F3 IV[4] or F0 III,[5] matching a subgiant or giant star, respectively. It is a variable of the Delta Scuti class, displaying both radial and non-radial pulsations.[7] The variable nature of this star was discovered by D. H. P. Jones and C. Margaret Haslam in 1966 at the suggestion of Olin J. Eggen,[10] and it has become one of the best studied stars in its class. The radial pulsations have shown little if any variations between 1974 and 2012. However, the non-radial pulsations vary continuously in frequency over periods spanning decades.[7] It is spinning rapidly with a rotation of at least one third of its critical velocity.[2]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. Schmid, V. S.; et al. (October 2014), "Discovery of binarity, spectroscopic frequency analysis, and mode identification of the δ Scuti star 4 CVn", Astronomy & Astrophysics, 570: 17, arXiv:1407.4257, Bibcode:2014A&A...570A..33S, doi:10.1051/0004-6361/201423669, A33.
  3. Samus, N. N.; et al. (2017), "General Catalogue of Variable Stars", Astronomy Reports, 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S.
  4. Morgan, W. W.; Abt, H. A. (February 1972), "The spectral classification of the F stars of intermediate luminosity", Astronomical Journal, 77: 35–37, Bibcode:1972AJ.....77...35M, doi:10.1086/111242
  5. Appenzeller, Immo (April 1967), "MK Spectral Types for 185 Bright Stars", Publications of the Astronomical Society of the Pacific, 79 (467): 102, Bibcode:1967PASP...79..102A, doi:10.1086/128449.
  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. Breger, M.; et al. (March 2017), "Nonradial and radial period changes of the δ Scuti star 4 CVn. II. Systematic behavior over 40 years", Astronomy & Astrophysics, 599: 8, arXiv:1612.06827, Bibcode:2017A&A...599A.116B, doi:10.1051/0004-6361/201629797, A116.
  8. Eggen, Olin J. (July 1998), "The Age Range of Hyades Stars", The Astronomical Journal, 116 (1): 284–292, Bibcode:1998AJ....116..284E, doi:10.1086/300413.
  9. "4 CVn". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-07-25.
  10. Jones, D. H. P.; Haslam, C. M. (February 1966), "A new delta Scuti variable", The Observatory, 86: 34–34, Bibcode:1966Obs....86...34J.
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