AR Cassiopeiae

AR Cassiopeiae
	; A light curve for AR Cassiopeiae, plotted from TESS data
Observation data; Epoch J2000.0 Equinox J2000.0
Constellation	Cassiopeia
	AB
Right ascension	23h 30m 01.93946s
Declination	+58° 32′ 56.1120″
Apparent magnitude (V)	4.883 (4.912 / 8.814)
	CD
Right ascension	23h 29m 52.2802s
Declination	+58° 32′ 54.458″
Apparent magnitude (V)	7.09
Characteristics
AB
Spectral type	B4 V + A6 V
U−B color index	−0.62
B−V color index	−0.12
Variable type	Algol
CD
Spectral type	B9 V
U−B color index	−0.14
B−V color index	+0.01
FG
Spectral type	F7 IV + F9 V
Astrometry
Radial velocity (Rv)	−15.9±0.9 km/s
Proper motion (μ)	RA: 17.90 mas/yr ; Dec.: 4.15 mas/yr
Parallax (π)	5.25 ± 0.52 mas
Distance	620 ± 60 ly ; (190 ± 20 pc)
Aa
Absolute magnitude (MV)	−1.87±0.13
Absolute bolometric; magnitude (Mbol)	−3.56±0.13
Ab
Absolute magnitude (MV)	2.20±0.11
Absolute bolometric; magnitude (Mbol)	2.18±0.11
Orbit
Primary	Aa
Companion	Ab
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
Aa
Mass	5.90±0.20 M☉
Radius	5.05±0.06 R☉
Surface gravity (log g)	3.80±0.02 cgs
Temperature	17,200±500 K
Ab
Mass	1.86±0.06 M☉
Radius	1.60±0.03 R☉
Surface gravity (log g)	4.30±0.02 cgs
Temperature	8,150±200 K
Other designations
	ADS 16795, CCDM J23300+5833, WDS J23300+5833
	AR Cassiopeiae (AB): 1H. Cas, AR Cas, BD+57°2748, HD 221253, HIP 115990, HR 8926, SAO 35478
	HD 221237 (CD): BD+57°2747, HD 221237, SAO 35476
	FG: UCAC4 743-089692
Database references
SIMBAD	AR Cas (AB)
	CD
	D
	F
	G

AR Cassiopeiae (AR Cas) is a variable star in the constellation of Cassiopeia. It is thought to be a member of a septuple star system, one of only two known star systems with a multiplicity of 7, the other being Nu Scorpii.^[12]^[9]

Nomenclature

The multiple star system as a whole has the designations ADS 16795, CCDM J23300+5833, and WDS J23300+5833AB in the Aitken Double Star Catalogue, the Catalogue of Components of Double and Multiple Stars, and the Washington Double Star Catalog respectively.^[8]

AR Cassiopeiae has been referred to as IH Cas in some literature, looking similar to a variable star designation although not a valid one since the second letter of a variable star designation is always equal to the first or occurs later in the alphabet. 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.^[11] 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.^[11]

Properties

The primary star system, AR Cassiopeiae, is a triple. AR Cassiopeiae B is located 0.800″ away from AR Cassiopeiae A.^[9] AR Cassiopeiae A itself is an Algol-type eclipsing binary with an orbital period of about 6.07 days.^[4] 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.^[4]

Farther out are two other stars, designated components C and D. They are 76.1″, or about 1.27′, away from the central system.^[9] Their combined spectrum matches that of another B-type main-sequence star.^[6] This pair is also designated HD 221237.^[6] 67.2″ (1.12′) away from AR Cassiopeiae is another pair of stars, F and G, both F-type stars.^[9]

All these stars are known to be common proper motion companions.^[9] However, the star listed as component E in most multiple star catalogues is an unrelated background star.