SZ Crateris

SZ Crateris is a binary star system in the southern constellation Crater. Both components belong to the main sequence: the primary star has a spectral classification of K5V while the secondary is a red dwarf of spectral class M0V. The radius of the primary is about 66% the radius of the Sun, while the secondary member is only about 42% of the solar radius. In 1994, the two stars were separated by 5.1 arc seconds, which is equivalent to 112.41 astronomical units.^[8]

Apparentmagnitude(V)8.61^[3]

Apparentmagnitude(V)11.0^[3]

SpectraltypeK7V/M2.5Ve^[5]

U−B color index+1.20^[6]

Quick facts Observation data Epoch J2000 Equinox J2000, Apparent magnitude (V) ...

SZ Crateris

A visual band light curve for SZ Crateris, adapted from Cutispoto et al. (2001)[1]
Observation data Epoch J2000      Equinox J2000
Constellation	Crater
A
Right ascension	11h 21m 26.6594s[2]
Declination	−20° 27′ 13.790″[2]
Apparent magnitude (V)	8.61[3]
B
Right ascension	11h 21m 26.5883s[4]
Declination	−20° 27′ 09.394″[4]
Apparent magnitude (V)	11.0[3]
Characteristics
Spectral type	K7V/M2.5Ve[5]
U−B color index	+1.20[6]
B−V color index	+1.36[6]
Variable type	BY Dra[7]
Astrometry
A
Radial velocity (Rv)	−0.11[2] km/s
Proper motion (μ)	RA: +181.231[2] mas/yr Dec.: −92.306[2] mas/yr
Parallax (π)	76.4165±0.0821 mas[2]
Distance	42.68 ± 0.05 ly (13.09 ± 0.01 pc)
Absolute magnitude (MV)	+7.75[8]
B
Radial velocity (Rv)	−2.86[4] km/s
Proper motion (μ)	RA: +220.306[4] mas/yr Dec.: −129.404[4] mas/yr
Parallax (π)	76.3549±0.0955 mas[4]
Distance	42.72 ± 0.05 ly (13.10 ± 0.02 pc)
Absolute magnitude (MV)	+10.0[8]
Orbit[9]
Period (P)	714.6 yr
Semi-major axis (a)	5.896″
Eccentricity (e)	0.63
Details
A
Radius	0.63[2] R☉
Luminosity	0.109[2] L☉
Surface gravity (log g)	4.5[10] cgs
Temperature	4,162[2] K
Metallicity [Fe/H]	0.04[10] dex
Rotational velocity (v sin i)	4.5[10] km/s
B
Radius	0.593[11][a] R☉
Luminosity	0.0575[11][b] L☉
Temperature	3,670[11] K
Age	194±20[12] Myr
Other designations
SZ Crt, BD−19 3242, GJ 425, HD 98712, SAO 179801, HIP 55454
A: LTT 4204[13]
B: LTT 4205[14]
Database references
SIMBAD	data
	A
	B

Close

SZ Crateris was discovered to be variable in 1985 and is classified as a marginal BY Draconis variable, with an optical variability cycle of 11.58 days.^[15] The star causing the variability is unspecified^[16] and the total brightness change is less than 0.1 magnitudes,^[7] but the faintness of the secondary makes it likely that the primary star is the one varying in brightness.^[15] Compared to the Sun, SZ Crateris has a slightly higher proportion of elements other than hydrogen and helium.^[10] Based upon gyrochronology, the estimated age of this star is under 200 million years.^[12]

The SZ Crateris system is a member of the Ursa Major moving group of stars that have similar motions through space.^[10] The space velocity components of this system are U = +13.86±0.37, V = −3.51±1.97 and W = +1.65±1.53 km/s.^[17] It is on an orbit through the Milky Way that has an orbital eccentricity of 0.092, which will bring it as close as 26.06 kly (7.99 kpc) to the galactic core, and as distant as 31.31 kly (9.60 kpc). The inclination of the orbit carries the system as much as 0.352 kly (0.108 kpc) from the plane of the galactic disk.^[18]