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
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ursa Minor
Right ascension  15h 02m 01.3660s[1]
Declination +83° 03′ 48.6306″[1]
Apparent magnitude (V) 10.8 - 19.0[2]
Characteristics
Spectral type C[2] (R[3])
Variable type R CrB[2]
Astrometry
Proper motion (μ) RA: −7.660±0.150[1] mas/yr
Dec.: 4.279±0.086[1] mas/yr
Parallax (π)0.1397 ± 0.0379[1] mas
Distanceapprox. 23,000 ly
(approx. 7,000 pc)
Details
Mass0.7±0.2[4] M☉
Luminosity7,900+12,000
−4,800[4] L☉
Surface gravity (log g)0.5±0.3[4] cgs
Temperature5,250±250[4] K
Metallicity [Fe/H]−1.85[4] dex
Other designations
Z UMi, Gaia DR2 1722500654150398208, TYC 4634-1727-1, 2MASS J15020132+8303485[5]
Database references
SIMBADdata

Z Ursae Minoris was discovered to be a variable star in 1934.[6] It was catalogued as a probable Mira variable, due to its red colour and variations over several hundred days.[7] It was discovered to be a carbon star in a survey published in 1985,[8] and subsequently found also to be hydrogen-deficient.[6] After fading by almost six magnitudes in 1992, it was classified as an R Coronae Borealis variable.[9] It was confirmed as an R Coronae Borealis variable, one of the coolest in the class, after its spectrum was analysed in 2006.[4]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. "Z UMi". The International Variable Star Index. Retrieved 2019-10-09.
  3. 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.
  4. 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.
  5. "Z Ursae Minoris". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-10-09.
  6. 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.
  7. 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.
  8. 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.
  9. 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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