BZ Ursae Majoris

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]

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]
Distance	505 ± 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
Mass	0.65[9][10] M☉
Radius	6,880[11] km
Surface gravity (log g)	7.5[5][12] cgs
Temperature	15,000[5][12] K
Rotational velocity (v sin i)	200[5] km/s
Donor star
Mass	0.13[6] M☉
Other designations
BZ UMa, 2MASS J08534416+5748406, PG 0849+580[13]
Database references
SIMBAD	data

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]

References

1. "Download Data". aavso.org. AAVSO. Retrieved 1 October 2021.
2. Kato, Taichi; et al. (December 2009). "Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae". Publications of the Astronomical Society of Japan. 61: S395–S616. arXiv:0905.1757. Bibcode:2009PASJ...61S.395K. doi:10.1093/pasj/61.sp2.S395. Retrieved 19 June 2022.
3. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
4. Heinze, A. N.; et al. (November 2018), "A First Catalog of Variable Stars Measured by the Asteroid Terrestrial-impact Last Alert System (ATLAS)", The Astronomical Journal, 156 (5): 49, arXiv:1804.02132, Bibcode:2018AJ....156..241H, doi:10.3847/1538-3881/aae47f, S2CID 59939788, 241.
5. Godon, Patrick; et al. (September 2011), "A Far-Ultraviolet Spectroscopic Analysis of BZ Ursae Majoris", Publications of the Astronomical Society of the Pacific, 123 (907): 1071, arXiv:1107.4790, Bibcode:2011PASP..123.1071G, doi:10.1086/661763, S2CID 119265399.
6. Ringwald, F. A.; et al. (November 1994), "Orbital studies of the cataclysmic variables CZ Orionis, V1193 Orionis and BZ Ursae Majoris", Monthly Notices of the Royal Astronomical Society, 271 (2): 323–342, Bibcode:1994MNRAS.271..323R, doi:10.1093/mnras/271.2.323.
7. Vogt, N.; et al. (April 2021), "Determination of the superoutburst cycle lengths of 206 SU UMa-type dwarf novae", Monthly Notices of the Royal Astronomical Society, 502 (4): 5668–5678, arXiv:2101.02756, Bibcode:2021MNRAS.502.5668V, doi:10.1093/mnras/staa3711.
8. Szkody, Paula; Feinswog, Laurie (November 1988), "Infrared Light Curves of Three Novae and Three Dwarf Novae at Quiescence", Astrophysical Journal, 334: 422, Bibcode:1988ApJ...334..422S, doi:10.1086/166846.
9. Maccarone, Thomas J.; Arur, Kavitha (December 2019), "On the Mass of the White Dwarf in BZ UMa", Research Notes of the American Astronomical Society, 3 (12): 185, Bibcode:2019RNAAS...3..185M, doi:10.3847/2515-5172/ab60ab, S2CID 216539831, 185.
10. Yu, Zhuo-li; et al. (February 2018), "An Empirical Correlation of T max-M WD of Dwarf Novae and the Average White Dwarf Mass in Cataclysmic Variables in the Galactic Bulge", The Astrophysical Journal, 853 (2): 8, arXiv:1804.00786, Bibcode:2018ApJ...853..182Y, doi:10.3847/1538-4357/aaa47d, S2CID 119364315, 182.
11. İkis Gün, G.; et al. (December 2013), "Preliminary results of the spectral analysis of Suzaku data of SW Ursae Majoris and BZ Ursae Majoris", New Astronomy, 25: 1–6, Bibcode:2013NewA...25....1I, doi:10.1016/j.newast.2013.03.011.
12. Sion, Edward M. (June 2012), "White Dwarfs in Cataclysmic Variable Stars: Surface Temperatures and Evolution", Journal of Astronomy and Space Sciences, 29 (2): 169–173, Bibcode:2012JASS...29..169S, doi:10.5140/JASS.2012.29.2.169.
13. "BZ UMa", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2022-03-09.
14. Price, A.; et al. (November 2009), "Polarimetry and the Long-Awaited Superoutburst of BZ UMa", Publications of the Astronomical Society of the Pacific, 121 (885): 1205, arXiv:0909.4024, Bibcode:2009PASP..121.1205P, doi:10.1086/648479, S2CID 118612829.
15. Neustroev, V. V.; et al. (July 2004), Tovmassian, G.; E., Sion (eds.), "New spectroscopic observations of dwarf nova BZ Ursae Majoris with extremely unusual emission lines profiles", Compact Binaries in the Galaxy and Beyond, Proceedings of the conference held 17-22 November, 2003 in La Paz, Baja California Sur, IAU Colloquium 194, Revista Mexicana de Astronomía y Astrofísica (Serie de Conferencias), vol. 20, p. 269, Bibcode:2004RMxAC..20..269N.
16. Kukarkin, B. V.; et al. (October 1970), "57th Name-List of Variable Stars", Information Bulletin on Variable Stars, 480 (1): 1, Bibcode:1970IBVS..480....1K.
17. Green, R. F.; Ferguson, D. H.; Liebert, J.; Schmidt, M. (June 1982), "Cataclysmic variable candidates from the Palomar Green Survey", Publications of the Astronomical Society of the Pacific, 94: 560–564, Bibcode:1982PASP...94..560G, doi:10.1086/131022, S2CID 120644760.
18. Wenzel, W. (December 1982), "BZ Ursae Majoris - Missing Link Between the Dwarf Novae of U Geminorum and WZ Sagittae Type", Information Bulletin on Variable Stars, 2256 (1): 1, Bibcode:1982IBVS.2256....1W.
19. Claudi, R.; et al. (March 1990), Green, D. W. E. (ed.), "BZ Ursae Majoris", IAU Circular, 4975 (2): 2, Bibcode:1990IAUC.4975....2C.
20. Gänsicke, Boris T.; et al. (September 2003), "Anomalous Ultraviolet Line Flux Ratios in the Cataclysmic Variables 1RXS J232953.9+062814, CE 315, BZ Ursae Majoris, and EY Cygni, Observed with the Hubble Space Telescope Space Telescope Imaging Spectrograph", The Astrophysical Journal, 594 (1): 443–448, arXiv:astro-ph/0305264, Bibcode:2003ApJ...594..443G, doi:10.1086/376902, S2CID 120224177.

Further reading

• Sion, E. M.; Godon, P. (2012), "White dwarfs in cataclysmic variable stars: accretion physics and evolution", Memorie della Societa Astronomica Italiana, 83: 539, Bibcode:2012MmSAI..83..539S.
• Jiang, L. L.; et al. (January 2010), "The Photometry of Cataclysmic Variable V1159 Ori and BZ UMa", Acta Astronomica Sinica, 51 (1): 42–53, Bibcode:2010AcASn..51...42J.
• Price, A.; et al. (May 2004), "Flickering and Periodic Activity in the 2004 Outburst of BZ UMa", Information Bulletin on Variable Stars, 5526 (1): 1, Bibcode:2004IBVS.5526....1P.
• Kato, T. (September 1999), "CCD Photometry of the 1999 March Outburst of BZ UMa: Detection of Quasi-Periodic Oscillations", Information Bulletin on Variable Stars, 4768 (1): 1, Bibcode:1999IBVS.4768....1K.
• Jurcevic, J. S.; et al. (May 1994), "Spectroscopy and Photometry of the Dwarf Nova BZ UMa and the CV Line-Width/K, Mass-Ratio Relation", Publications of the Astronomical Society of the Pacific, 106: 481, Bibcode:1994PASP..106..481J, doi:10.1086/133403, S2CID 120863048.
• Ringwald, F. A.; Thorstensen, J. R. (September 1990), "Quasi-Periodic Variation in the Radial Velocity Curve of the Dwarf Nova BZ UMa", Bulletin of the American Astronomical Society, 22: 1291, Bibcode:1990BAAS...22.1291R.