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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]
Spectral type C [3] (R [4])
Variable type R CrB [3]
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]
Distanceapprox. 15,000  ly
(approx. 4,600  pc)
Mass0.7±0.2 [5]  M
[5]  L
Surface gravity (log g)0.5±0.3 [5]  cgs
Temperature5,250±250 [5]  K
Metallicity [Fe/H]−1.85 [5]  dex
Other designations
Z UMi, TYC 4634-1727-1, 2MASS J15020132+8303485 [6]
Database references

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

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]


  1. ^ "Download Data". AAVSO. Retrieved 1 October 2021.
  2. ^ a b c d e f Vallenari, A.; et al. (Gaia Collaboration) (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. arXiv: 2208.00211. doi: 10.1051/0004-6361/202243940. Gaia DR3 record for this source at VizieR.
  3. ^ a b c "Z UMi". The International Variable Star Index. Retrieved 2019-10-09.
  4. ^ Alksnis, A.; Balklavs, A.; Dzervitis, U.; Eglitis, I.; Paupers, O.; Pundure, I. (2001). "General Catalog of Galactic Carbon Stars by C. B. Stephenson. Third Edition". Baltic Astronomy. 10 (1–2): 1–318. Bibcode: 2001BaltA..10....1A. doi: 10.1515/astro-2001-1-202.
  5. ^ a b c d e f Kipper, Tõnu; Klochkova, Valentina G. (2006). "A Cool R Coronae Borealis Star Z UMi". Baltic Astronomy. 15: 531–37. arXiv: 0706.3271. Bibcode: 2006BaltA..15..531K.
  6. ^ "Z Ursae Minoris". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-10-09.
  7. ^ a b Goswami, A.; Rao, N. K.; Lambert, D. L.; Gonzalez, G. (1997). "On the Hydrogen Deficient Nature of Z UMi". Publications of the Astronomical Society of the Pacific. 109: 796. Bibcode: 1997PASP..109..796G. doi: 10.1086/133946.
  8. ^ 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: B/gcvs. Bibcode: 2009yCat....102025S.
  9. ^ Stephenson, C. B. (1985). "New carbon stars found in a hemispheric survey". The Astronomical Journal. 90: 784. Bibcode: 1985AJ.....90..784S. doi: 10.1086/113787.
  10. ^ Benson, Priscilla J.; Clayton, Geoffrey C.; Garnavich, Peter; Szkody, Paula (1994). "Z Ursa Minoris -- a new R Coronae Borealis variable". The Astronomical Journal. 108 (1): 247–50. Bibcode: 1994AJ....108..247B. doi: 10.1086/117063.