AR Cassiopeiae

AR Cassiopeiae (AR Cas) is a multiple star system in the constellation of Cassiopeia. It is thought to be a septuple star system. It is one of only two known star systems with a multiplicity of 7, the other being Nu Scorpii, with no physical multiple stars of greater multiplicity yet found as of January 2020.[10][8][11]

AR Cassiopeiae
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cassiopeia [1]
AB
Right ascension 23h 30m 01.93946s[2]
Declination +58° 32′ 56.1120″[2]
Apparent magnitude (V) 4.883 (4.912 / 8.814)[3]
CD
Right ascension 23h 29m 52.2802s[4]
Declination +58° 32′ 54.458″[4]
Apparent magnitude (V) 7.09[5]
Characteristics
AB
Spectral type B4 V + A6 V[3]
U−B color index −0.62[6]
B−V color index −0.12[6]
Variable type Algol[7]
CD
Spectral type B9 V[5]
U−B color index −0.14[6]
B−V color index +0.01[6]
FG
Spectral type F7 IV + F9 V[8]
Astrometry
Radial velocity (Rv)-15.9 ± 0.9[9] km/s
Proper motion (μ) RA: 17.90[2] mas/yr
Dec.: 4.15[2] mas/yr
Parallax (π)5.25 ± 0.52[2] mas
Distance620 ± 60 ly
(190 ± 20 pc)
Aa
Absolute magnitude (MV)−1.87 ± 0.13[3]
Absolute bolometric
magnitude (Mbol)		−3.56 ± 0.13[3]
Ab
Absolute magnitude (MV)2.20 ± 0.11[3]
Absolute bolometric
magnitude (Mbol)		2.18 ± 0.11[3]
Orbit[3]
PrimaryAa
CompanionAb
Period (P)6.0663170 d
Eccentricity (e)0.240
Inclination (i)85.34 ± 0.50°
Periastron epoch (T)JD 2436847.9404 ± 0.0055
Argument of periastron (ω)
(secondary)		41.82 ± 0.47°
Details[3]
Aa
Mass5.90 ± 0.20 M☉
Radius5.05 ± 0.06 R☉
Surface gravity (log g)3.80 ± 0.02 cgs
Temperature17200 ± 500 K
Ab
Mass1.86 ± 0.06 M☉
Radius1.60 ± 0.03 R☉
Surface gravity (log g)4.30 ± 0.02 cgs
Temperature8150 ± 200 K
Other designations
IH Cas, AR Cas, BD+57 2748, HD 221253, HIP 115990, HR 8926, SAO 35478[7]
Database references
SIMBADAR Cas AB
AR Cas CD
AR Cas D
AR Cas F
AR Cas G

Nomenclature

AR Cassiopeiae was frequently referred to as IH Cas (or IH Cas) in some literature.[12] The origin of the designation "IH Cassiopeiae" is from the 17th century catalogue and constellation map by Johannes Hevelius, which was kept in use due to the lack of a Flamsteed designation or Bayer designation for the star.[12] It was the first star in Cassiopeia that Flamsteed's edition of Hevelius catalogued,[13] thus "1 Hev. Cas" or "1 H. Cas" (similar to Gould designations), which becomes IH Cas through corruption.[12]

Properties

The primary subsystem, AR Cassiopeiae AB, is a triple. AR Cassiopeiae B is located 0.800″ away from AR Cassiopeiae A.[8] AR Cassiopeiae A itself an Algol-type eclipsing binary[7] with an orbital period of about 6.07 days.[3] Its primary is a B-type main-sequence star, and the secondary, an A-type main-sequence star. The secondary star may be an Am star as well.[3]

Farther out are two other stars, designated AR Cassiopeiae C and D, respectively. They are 76.1″ (or about 1.27′) away from the central system.[8] Their combined spectrum matches that of another B-type main-sequence star.[5] This pair is also designated HD 221237.[5] 67.2″ (1.12′) away from AR Cassiopeiae AB is another pair of stars, F and G, both F-type stars.[8] All four of these stars are known to be common proper motion companions.[8]

References
  1. WikiSky, "HD 221253" (accessed 2010-10-27)
  2. van Leeuwen, F.; et al. (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.
  3. Holmgren, D. E.; Hadrava, P.; Harmanec, P.; Eenens, P.; Corral, L. J.; Yang, S.; Ak, H.; Bozić, H. (1999). "Search for forced oscillations in binaries. III. Improved elements and the detection of line-profile variability of the B4V + A6V: system AR Cassiopeiae". Astronomy and Astrophysics. 345: 855. Bibcode:1999A&A...345..855H.
  4. Gaia Collaboration (2016). "Gaia Data Release 1". Astronomy & Astrophysics. 595: A2. arXiv:1609.04172. Bibcode:2016A&A...595A...2G. doi:10.1051/0004-6361/201629512. S2CID 1828208.
  5. "HD 221237". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 23 August 2017.
  6. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  7. "V* AR Cas". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 23 August 2017.
  8. Tokovinin, A. A. (1997). "MSC - a catalogue of physical multiple stars". Astronomy and Astrophysics Supplement Series. 124: 75–84. Bibcode:1997A&AS..124...75T. doi:10.1051/aas:1997181.
  9. Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Washington. Bibcode:1953GCRV..C......0W.
  10. Eggleton, P. P.; Tokovinin, A. A. (September 2008). "A catalogue of multiplicity among bright stellar systems". Monthly Notices of the Royal Astronomical Society. 389 (2): 869–879. arXiv:0806.2878. Bibcode:2008MNRAS.389..869E. doi:10.1111/j.1365-2966.2008.13596.x. S2CID 14878976.
  11. Bob Argyle, ed. (2004). Observing and Measuring Visual Double Stars. Patick Moore's Practical Astronomy Series. Springer-Verlag. p. 9. ISBN 1-85233-558-0.
  12. Somerville, W. B. (1986). "1H. Cas = AR Cas". The Observatory. 106: 40–42. Bibcode:1986Obs...106...40S.
  13. Flamsteed, J., ed. (1725). "Johannis Hevelii Catalogus Stellarum Fixarum Ad Annum Christi 1660 completum". Historia Coelestis Britannica. 3: 54.CS1 maint: extra text: authors list (link)
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