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YZ Cas

Location of YZ Cassiopeiae (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Cassiopeia
A
Right ascension	00 45 39.0777
Declination	+74° 59′ 17.063″
Apparent magnitude (V)	5.653
B
Right ascension	00 45 42,1503
Declination	+74° 58′ 43.242″
Apparent magnitude (V)	11.23
Characteristics
A
Spectral type	A2IV (A1Vm + F2V)
U−B color index	+0.07
B−V color index	+0.05
Variable type	Algol
B
Spectral type	F2V
U−B color index	+0.64
B−V color index	+0.94
Astrometry
Radial velocity (Rv)	+8.90±0.4 km/s
Proper motion (μ)	RA: −15.07 mas/yr Dec.: −22.17 mas/yr
Parallax (π)	11.24 ± 0.55 mas
Distance	103.8 pc
Absolute magnitude (MV)	+0.251
Orbit
Companion	TYC 4307-2168-1
Period (P)	86 580 yr
Orbit
Primary	Aa
Companion	Ab
Period (P)	4.467 days
Semi-major axis (a)	17.47 R☉
Eccentricity (e)	0.0
Inclination (i)	88.332°
Details
Aa
Mass	2.308 M☉
Radius	2.547 R☉
Luminosity	41.69 L☉
Surface gravity (log g)	3.988 cgs
Temperature	9,200 K
Rotational velocity (v sin i)	29.2 km/s
Ab
Mass	1.325 M☉
Radius	1.359 R☉
Luminosity	3.34 L☉
Surface gravity (log g)	4.311 cgs
Temperature	6,890 K
Metallicity	+0.10 dex
Rotational velocity (v sin i)	15.0 km/s
Age	490 - 550 Myr
Other designations
21 Cassiopeiae, HR 192, BD+74 27, HD 4161, SAO 4216, HIP 3572, GC 891, ADS 624 A, CCDM J00457+7459
Database references
SIMBAD	data

YZ Cassiopeiae (21 Cas) is a star system 103.8 parsecs (339 ly) away from Earth, in the constellation Cassiopeia. It comprises three stars: an eclipsing Algol-type binary and a visually fainter star about 3000 AU distant. It is faintly visible to the naked eye under good observing conditions.

The primary star in the YZ Cassiopeiae system is a white subgiant (main sequence) star of spectral type A1Vm and 2.31 solar masses (M_☉) with a less massive main sequence dwarf star of type F2V and 1.35 M_☉.

In 1924, Joel Stebbins announced his discovery that the star, then known as 21 Cassiopeiae, is an eclipsing binary. It was given its variable star designation, YZ Cassiopeiae, in 1925. The apparent magnitude of the eclipsing binary varies from 5.65 to 6.05 with a period of 4.4672 days. Combined, they appear to have a spectral type of A2IV.

The binary has a dimmer (magnitude 9.7 according to Norton, or 10.5 by SIMBAD) companion of 0.8 M_☉ orbiting with a period of about 86 580 years.

References

1. ^ van Leeuwen, F. (November 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.
2. ^ Jerzy M. Kreiner, Chun-Hwey Kim, Il-Seong Nha. YZ CAS: Atlas of O-C Diagrams of Eclipsing Binary Stars
3. ^ Hog, E.; Kuzmin, A.; Bastian, U.; Fabricius, C.; Kuimov, K.; Lindegren, L.; Makarov, V. V.; Roeser, S. (1998). "The TYCHO Reference Catalogue". Astronomy and Astrophysics. 335: L65. Bibcode:1998A&A...335L..65H.
4. ^ Eggen, O. J. (1963). "Three-color photometry of the components in 228 wide double and multiple systems". Astronomical Journal. 68: 483. Bibcode:1963AJ.....68..483E. doi:10.1086/109000.
5. Grenier, S.; Baylac, M.-O.; Rolland, L.; Burnage, R.; Arenou, F.; Briot, D.; Delmas, F.; Duflot, M.; Genty, V.; Gómez, A. E.; Halbwachs, J.-L.; Marouard, M.; Oblak, E.; Sellier, A. (1999). "Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS" (PDF). Astronomy and Astrophysics Supplement. 137 (3): 451. Bibcode:1999A&AS..137..451G. doi:10.1051/aas:1999489.
6. ^ Bilir, S.; Ak, T.; Soydugan, E.; Soydugan, F.; Yaz, E.; Filiz Ak, N.; Eker, Z.; Demircan, O.; Helvaci, M. (2008). "New absolute magnitude calibrations for detached binaries". Astronomische Nachrichten. 329 (8): 835. arXiv:0806.1290. Bibcode:2008AN....329..835B. doi:10.1002/asna.200811002. S2CID 6131326.
7. 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....102025S.
8. ^ Pavlovski, K.; Southworth, J.; Kolbas, V.; Smalley, B. (2014). "Absolute dimensions of detached eclipsing binaries - III. The metallic-lined system YZ Cassiopeiae". Monthly Notices of the Royal Astronomical Society. 438 (1): 590–603. arXiv:1311.3482. Bibcode:2014MNRAS.438..590P. doi:10.1093/mnras/stt2229. S2CID 56144135.
9. Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
10. ^ Tokovinin 1997-1999. J/A+AS/124/75. Multiple star catalogue (MSC)
11. ^ Eker, Z.; Soydugan, F.; Soydugan, E.; Bilir, S.; Yaz Gökçe, E.; Steer, I.; Tüysüz, M.; Şenyüz, T.; Demircan, O. (2015). "Main-Sequence Effective Temperatures from a Revised Mass-Luminosity Relation Based on Accurate Properties". The Astronomical Journal. 149 (4): 131. arXiv:1501.06585. Bibcode:2015AJ....149..131E. doi:10.1088/0004-6256/149/4/131. S2CID 118740259.
12. ^ Maxted, P. F. L.; Serenelli, A. M.; Southworth, J. (2015). "Bayesian mass and age estimates for transiting exoplanet host stars". Astronomy & Astrophysics. 575: A36. arXiv:1412.7891. Bibcode:2015A&A...575A..36M. doi:10.1051/0004-6361/201425331. S2CID 54857801.
13. "V* YZ Cas". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 26 January 2018.
14. "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
15. Stebbins, Joel (1924). "Photo-electric photometry at the Washburn Observatory". Popular Astronomy. 32: 233–234. Bibcode:1924PA.....32..233S. Retrieved 14 January 2025.
16. Guthnick, P.; Prager, R. (March 1925). "Benennung von neu entdeckten veränderlichen Sternen". Astronomische Nachrichten. 224 (8): 129–148. Bibcode:1925AN....224..129G. doi:10.1002/asna.19252240802. Retrieved 14 January 2025.
17. Norton, Arthur P. (1973). Norton's Star Atlas. Gall & Inglis. p. 118. ISBN 0-85248-900-5.

v t e Constellation of Cassiopeia
List of stars in Cassiopeia Cassiopeia in Chinese astronomy
Stars	Bayer α (Schedar) β (Caph) γ (Navi/Tsih) δ (Ruchbah) ε (Segin) ζ (Fulu) η (Achird) θ (Marfak) ι κ λ μ ν ξ ο π ρ σ τ υ υ (Castula) φ χ ψ ω Flamsteed 1 2 4 6 9 10 12 42 47 48 (A) 49 50 54 Variable R S TZ WZ YZ (21) AO AR PZ V373 V509 V547 V669 V705 V762 V773 V863 V987 V1022 V1405 HR 5 91 144 196 244 273 297 743 932 8832 8853 8881 HD 861 7924 7977 15558 17156 (Nushagak) 240210 240237 240429 240430 Other BD+60°2522 Gliese 49 IRAS 23304+6147 LS I +61 303 PSR J0205+6449 Tycho G 4U 0142+61 WR 2 WR 3
Exoplanets HD 7924 b HD 17156 b HD 219134 b c d e (h) f g HD 240210 b HD 240237 b
Star clusters Messier 52 Messier 103 NGC 103 NGC 110 NGC 129 NGC 133 NGC 136 NGC 146 NGC 189 NGC 225 NGC 358 NGC 366 NGC 381 NGC 433 NGC 436 NGC 457 NGC 559 NGC 637 NGC 654 NGC 659 NGC 663 NGC 1027 NGC 7789 NGC 7790 Trumpler 3
Nebulae	NGC 281 7635 Other 3C 58 Cassiopeia A Heart Nebula IC 289 IC 1805 KjPn 8 LBN 114.55+00.22 Sh 2-185 Westerhout 5
Galaxies	NGC 147 185 278 Other Andromeda VII 3C 20 3C 35 Dwingeloo 1 Dwingeloo 2 MB 3 IC 10 Maffei 1 Maffei 2 QSO B0153+744
Astronomical events SN 1181 SN 1572 (B)
Category

• Triple star systems
• Eclipsing binaries
• Cassiopeia (constellation)
• A-type subgiants
• F-type main-sequence stars
• Flamsteed objects
• Objects with variable star designations
• Durchmusterung objects
• Henry Draper Catalogue objects
• Hipparcos objects
• Bright Star Catalogue objects