BZ Ursae Majoris

BZ Ursae Majoris

A visual band light curve for BZ Ursae Majoris. The main plot (from AAVSO data[1]) shows several outbursts, and the inset plot (adapted from Kato et al.[2]) shows a single superoutburst in detail.
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ursa Major
Right ascension 08h 53m 44.174s[3]
Declination +57° 48′ 40.59″[3]
Apparent magnitude (V) 15.7 to 16.5[4]
10.2 to 15.9[5]
Characteristics
Spectral type M5.5:Ve[6]
Variable type SU UMa[7]
Astrometry
Proper motion (μ) RA: 26.318 mas/yr[3]
Dec.: −15.915 mas/yr[3]
Parallax (π)6.4561 ± 0.0441 mas[3]
Distance505 ± 3 ly
(155 ± 1 pc)
Orbit[6]
Period (P)97.8±0.1 h
Inclination (i)~60[8]°
Periastron epoch (T)2,448,319.897±0.003 HJD
Details
White dwarf
Mass0.65[9][10] M☉
Radius6,880[11] km
Surface gravity (log g)7.5[5][12] cgs
Temperature15,000[5][12] K
Rotational velocity (v sin i)200[5] km/s
Donor star
Mass0.13[6] M☉
Other designations
BZ UMa, 2MASS J08534416+5748406, PG 0849+580[13]
Database references
SIMBADdata

BZ Ursae Majoris is a dwarf nova star system in the northern circumpolar constellation of Ursa Major. It consists of a white dwarf primary in a close orbit with a red dwarf. The latter star is donating mass, which is accumulating in an accretion disk orbiting the white dwarf.[14] The system is located at a distance of approximately 505 light years from the Sun based on parallax measurements.[3]

This system was discovered to vary in brightness by B. E. Markaryan in 1968,[15] and it was given the variable star designation BZ UMa.[16] After four years of observation by the AAVSO, it was proposed to be a cataclysmic variable by M. Mayall.[14] In 1982, R. F. Green and associates identified it as a cataclysmic variable candidate of the U Gem-type, based on its spectrum.[17] The same year, W. Wenzel showed that this star had very long intervals between outbursts, placing it intermediate between the U Gem and WZ Sge classes.[18] P. Szkody and L. Feinswog examined the infrared light curve of the system, estimating an orbital inclination of 60° with no evidence of heating from the white dwarf.[8]

R. Claudi and associates in 1990 found a periodic modulation of hydrogen emission lines, indicating an orbital period of 1.62 h. They suggested it be classified as a SU UMa star.[19] Spectroscopic examination of the system using the Hubble Space Telescope during 2001 showed an anomalous abundance ratio of nitrogen to carbon that indicates CNO-processing.[20] This may be the result of an earlier evolutionary stage of the donor star that was stripped of its outer layers. A superoutburst was observed in 2007 that displayed superhumps. A lack of circular polarization indicates the white dwarf is not strongly magnetic, and thus this system is most likely not an intermediate polar.[14]

  1. ^ Cite error: The named reference aavso was invoked but never defined (see the help page).
  2. ^ Cite error: The named reference Kato_et_al_2009 was invoked but never defined (see the help page).
  3. ^ a b c d e Cite error: The named reference GaiaEDR3 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Heinze_et_al_2018 was invoked but never defined (see the help page).
  5. ^ a b c d Cite error: The named reference Godon_et_al_2011 was invoked but never defined (see the help page).
  6. ^ a b c Cite error: The named reference Ringwald_et_al_1994 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference Vogt_et_al_2021 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference Szkody_Feinswog_1988 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Maccarone_Arur_2019 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Yu_et_al_2018 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference İkis_Gün_et_al_2013 was invoked but never defined (see the help page).
  12. ^ a b Cite error: The named reference Sion2012 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  14. ^ a b c Cite error: The named reference Price_et_al_2009 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Neustroev_et_al_2004 was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference Kukarkin_et_al_1970 was invoked but never defined (see the help page).
  17. ^ Cite error: The named reference Green_et_al_1982 was invoked but never defined (see the help page).
  18. ^ Cite error: The named reference Wenzel1982 was invoked but never defined (see the help page).
  19. ^ Cite error: The named reference Claudi_et_al_1990 was invoked but never defined (see the help page).
  20. ^ Cite error: The named reference Gänsicke_et_al_2003 was invoked but never defined (see the help page).