Iota Cassiopeiae

Iota Cassiopeiae (ι Cas, ι Cassiopeiae) is a star system in the constellation Cassiopeia. The system has a combined apparent magnitude of 4.53,[11] making it visible to the naked eye. Based on its parallax, it is located about 133 light-years (41 parsecs) from Earth.[7]

ι Cassiopeiae

The Bayer-designated stars in Cassiopeia. Iota Cassiopeiae is circled.
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Cassiopeia
ι Cas A
Right ascension	02^h 29^m 03.960^s[1]
Declination	+67° 24′ 08.70″[1]
Apparent magnitude (V)	4.61[1](4.65 / 8.48)[2]
ι Cas B
Right ascension	02^h 29^m 03.567^s[1]
Declination	+67° 24′ 07.01″[1]
Apparent magnitude (V)	6.87[1]
ι Cas C
Right ascension	02^h 29^m 05.086^s[1]
Declination	+67° 24′ 05.53″[1]
Apparent magnitude (V)	9.05[3](9.14 / 11.84)[3]
Characteristics
U−B color index	+0.03[4]
B−V color index	+0.12[4]
ι Cas A
Spectral type	A3p / G6[2]
Variable type	α^2 CVn[5]
ι Cas B
Spectral type	F5[2]
ι Cas C
Spectral type	K4 / M2[3]
U−B color index	+0.18[4]
B−V color index	+0.72[4]
Astrometry
Radial velocity (Rv)	1.2 ± 2[6] km/s
Proper motion (μ)	RA: -26.61[7] mas/yr Dec.: 38.21[7] mas/yr
Parallax (π)	24.55 ± 0.81[7] mas
Distance	133 ± 4 ly (41 ± 1 pc)
Absolute magnitude (MV)	1.62 ± 0.07 (Aa) 5.60 ± 0.17 (Ab)[8]
Orbit[8]
Primary	ι Cas Aa
Companion	ι Cas Ab
Period (P)	50.2 ± 1.0 yr
Semi-major axis (a)	0.429 ± 0.007″
Eccentricity (e)	0.642 ± 0.009
Inclination (i)	149.0+1.7 −1.6°
Longitude of the node (Ω)	180.0+2.7 −2.8°
Periastron epoch (T)	B 1993.24 ± 0.08
Argument of periastron (ω) (secondary)	331.3+2.6 −2.7°
Orbit[9]
Primary	ι Cas A
Companion	ι Cas B
Period (P)	620 yr
Semi-major axis (a)	2.88″
Eccentricity (e)	0.75
Inclination (i)	115°
Longitude of the node (Ω)	0.8°
Periastron epoch (T)	B 1640
Argument of periastron (ω) (secondary)	283°
Details
ι Cas Aa
Mass	1.99 ± 0.28[2] M☉
Radius	2.3 ± 0.4[10] R☉
Luminosity	24[10] L☉
Temperature	8360 ± 275[10] K
Rotation	1.74033 d[10]
Rotational velocity (v sin i)	48[10] km/s
Age	100[8] Myr
ι Cas Ab
Mass	0.69 ± 0.12[2] M☉
ι Cas B
Mass	1.4[9] M☉
Temperature	6540[3] K
ι Cas Ca
Temperature	4520 ± 20[3] K
ι Cas Cb
Temperature	3590 ± 45[3] K
Other designations
BD+66° 213, HD 15089, HIP 11569, HR 707, SAO 12298
ι Cas A: TYC 4058-1504-1
ι Cas B: TYC 4058-1504-2
ι Cas C: TYC 4058-1505-1
Database references
SIMBAD	ι Cas
	ι Cas AB
	ι Cas A
	ι Cas B
	ι Cas C

Components

Iota Cassiopeiae is known to be a quintuple star system. The brightest star system, ι Cassiopeiae A, contains a white-colored A-type main-sequence star with a mean apparent magnitude of +4.61.[1] The primary component is a tighter binary star system itself. The two stars themselves were resolved by adaptive optics, revealing two stars. These are designated Aa and Ab (although confusingly they may also be labeled as A and Aa, respectively). The primary is classified as an Alpha² Canum Venaticorum-type variable star and the brightness of the system varies from magnitude +4.45 to +4.53 with a period of 1.74 days,[5] because of its magnetic field.[10] The fainter companion is a G-type star with a mass of only 0.69 M_☉.[2] The orbital period of the system is about 50 years.[8]

A second component, ι Cassiopeiae B, is a yellow-white F-type main sequence dwarf with an apparent magnitude of +6.87.[1] The semimajor axis of its orbit is 2.88 arcseconds, and it has an orbital period of 620 years around ι Cassiopeiae A.[9]

The third astrometric component, ι Cassiopeiae C, is another binary like ι Cassiopeiae A. It comprises two stars, a K-type star and a M-type star.[3] It orbits at an angular distance of 7 arcseconds from the A-B primary.[12]

References

1. Høg, E.; et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H.
2. Drummond, Jack; Milster, Scott; Ryan, Patrick; Roberts, Jr., Lewis C. (2003). "ι Cassiopeiae: Orbit, Masses, and Photometry from Adaptive Optics Imaging in the I and H Bands". The Astrophysical Journal. 585 (2): 1007. Bibcode:2003ApJ...585.1007D. doi:10.1086/346224.
3. Christou, Julian C.; Drummond, Jack D. (2006). "Measurements of Binary Stars, Including Two New Discoveries, with the Lick Observatory Adaptive Optics System". The Astronomical Journal. 131 (6): 3100. Bibcode:2006AJ....131.3100C. doi:10.1086/503255.
4. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
5. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....1.2025S.
6. Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Washington. Bibcode:1953GCRV..C......0W.
7. 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.
8. De Rosa, R. J.; Patience, J.; Vigan, A.; Wilson, P. A.; Schneider, A.; McConnell, N. J.; Wiktorowicz, S. J.; Marois, C.; Song, I.; MacIntosh, B.; Graham, J. R.; Bessell, M. S.; Doyon, R.; Lai, O. (2012). "The Volume-limited A-Star (VAST) survey - II. Orbital motion monitoring of A-type star multiples". Monthly Notices of the Royal Astronomical Society. 422 (4): 2765. arXiv:1112.3666. Bibcode:2012MNRAS.422.2765D. doi:10.1111/j.1365-2966.2011.20397.x. S2CID 102487103.
9. Heintz, W. D. (1996). "A Study of Multiple-Star Systems". The Astronomical Journal. 111: 408. Bibcode:1996AJ....111..408H. doi:10.1086/117792.
10. Aurière, M.; Wade, G. A.; Silvester, J.; Lignières, F.; Bagnulo, S.; Bale, K.; Dintrans, B.; Donati, J. F.; Folsom, C. P.; Gruberbauer, M.; Hui Bon Hoa, A.; Jeffers, S.; Johnson, N.; Landstreet, J. D.; Lèbre, A.; Lueftinger, T.; Marsden, S.; Mouillet, D.; Naseri, S.; Paletou, F.; Petit, P.; Power, J.; Rincon, F.; Strasser, S.; Toqué, N. (2007). "Weak magnetic fields in Ap/Bp stars". Astronomy and Astrophysics. 475 (3): 1053. arXiv:0710.1554. Bibcode:2007A&A...475.1053A. doi:10.1051/0004-6361:20078189. S2CID 54850596.
11. "* iot Cas". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 15 May 2017.
12. 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. (HR 707)