YZ Cassiopeiae
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cassiopeia |
| A | |
| Right ascension | 00h 45m 39.0777s |
| Declination | +74° 59′ 17.063″ |
| Apparent magnitude (V) | 5.653 |
| B | |
| Right ascension | 00h 45m 42,1503s |
| 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 [Fe/H] | +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.