Z Ursae Minoris

Z Ursae Minoris (Z UMi) is a carbon star and R Coronae Borealis variable in the constellation Ursa Minor.

Z Ursae Minoris

A visual band light curve for Z Ursae Minoris, plotted from AAVSO data[1]
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Ursa Minor
Right ascension	15h 02m 01.36335s[2]
Declination	+83° 03′ 48.6299″[2]
Apparent magnitude (V)	10.8 - 19.0[3]
Characteristics
Spectral type	C[3] (R[4])
Variable type	R CrB[3]
Astrometry
Radial velocity (Rv)	−36.07±0.98[2] km/s
Proper motion (μ)	RA: −7.346[2] mas/yr Dec.: +4.322[2] mas/yr
Parallax (π)	0.2159±0.0231 mas[2]
Distance	approx. 15,000 ly (approx. 4,600 pc)
Details
Mass	0.7±0.2[5] M☉
Luminosity	7,900+12,000 −4,800[5] L☉
Surface gravity (log g)	0.5±0.3[5] cgs
Temperature	5,250±250[5] K
Metallicity [Fe/H]	−1.85[5] dex
Other designations
Z UMi, TYC 4634-1727-1, 2MASS J15020132+8303485[6]
Database references
SIMBAD	data

Z Ursae Minoris was discovered to be a variable star in 1934.^[7] It was catalogued as a probable Mira variable, due to its red colour and variations over several hundred days.^[8] It was discovered to be a carbon star in a survey published in 1985,^[9] and subsequently found also to be hydrogen-deficient.^[7] After fading by almost six magnitudes in 1992, it was classified as an R Coronae Borealis variable.^[10] It was confirmed as an R Coronae Borealis variable, one of the coolest in the class, after its spectrum was analysed in 2006.^[5]