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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]
Distanceapprox. 15,000 ly
(approx. 4,600 pc)
Details
Mass0.7±0.2[5] M☉
Luminosity7,900+12,000
−4,800[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
SIMBADdata

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]


References


  1. "Download Data". aavso.org. AAVSO. Retrieved 1 October 2021.
  2. 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. "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. 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. 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.


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