WZ Cassiopeiae

WZ Cassiopeiae in optical light
Observation data Epoch J2000      Equinox J2000
Constellation	Cassiopeia
Right ascension	00h 01m 15.85680s[1]
Declination	+60° 21′ 19.0259″[1]
Apparent magnitude (V)	7.04[2] (6.3 – 8.8)[3]
Characteristics
Spectral type	C-N7 III: C2 2 Li 10[4]
U−B color index	+4.29[5]
B−V color index	+2.835±0.040[2]
Variable type	SRb[3]
Astrometry
Radial velocity (Rv)	−34.0±2[6] km/s
Proper motion (μ)	RA: +10.7693[1] mas/yr Dec.: −5.672[1] mas/yr
Parallax (π)	2.1227 ± 0.0297 mas[1]
Distance	1,540 ± 20 ly (471 ± 7 pc)
Details
Radius	~600[7] R☉
Luminosity	12,400[8] L☉
Temperature	3,095[8] K
Other designations
WZ Cas, BD+59°2810, HD 224855, HIP 99, SAO 21002[9]
Database references
SIMBAD	data

WZ Cassiopeiae (WZ Cas) is a deep red hued star in the northern constellation of Cassiopeia. It is a variable star with a magnitude that ranges from 6.3 down to 8.8,^[3] placing it near the limit of naked eye visibility at peak magnitude. The estimated distance to this star, as determined from its annual parallax shift of 2.1 mas,^[1] is about 1,540 light years. It is moving closer to the Earth with a heliocentric radial velocity of −34 km/s.^[6]

This is an aging carbon star on the asymptotic giant branch.^[7] Keenan (1993) assigned it a classification of C-N7 III: C₂ 2 Li 10, which indicates it is of the N star subtype in the revised Morgan–Keenan system, with a C₂ strength index of 2 (a measure of the excess of carbon over oxygen) and an anomalously strong line of lithium at 6707 Å.^[4] It is losing mass at the rate of 6.5×10⁻⁹ M_☉ yr⁻¹, which is on the low side for a star of this type. This is a semiregular variable of subtype SRb^[3] with periods of 186 and 366 days due to radial pulsations.^[7] It has expanded to around 600 times the Sun's radius and is radiating 12,400 times the Sun's luminosity^[8] from its photosphere at a relatively cool^[10] effective temperature of 3,095 K.^[8]

A magnitude 8.4 B-type visual companion, designated HD 224869, is located at an angular separation of 58″. The difference in the radial velocities for the two stars – 20 km/s – is too large for them to be dynamically associated.^[11]

References