DW Ursae Majoris is an eclipsing binary star system in the northern circumpolar constellation of Ursa Major, abbreviated DW UMa. It is a cataclysmic variable of the SX Sextanis type, consisting of a compact white dwarf that is accreting matter from an orbiting companion star.[8] The brightness of this source ranges from an apparent visual magnitude of 13.6 down to magnitude 18,[5] which is too faint to be viewed with the naked eye. The distance to this system is approximately 1,920 light years based on parallax measurements.[2]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ursa Major |
| Right ascension | 10h 33m 52.875s[2] |
| Declination | +58° 46′ 54.72″[2] |
| Apparent magnitude (V) | 13.6 to 18.0[3] |
| Characteristics | |
| Spectral type | M7±2.0[4] |
| Variable type | Algol variable[5] |
| Astrometry | |
| Proper motion (μ) | RA: 0.974 mas/yr[2] Dec.: 1.396 mas/yr[2] |
| Parallax (π) | 1.6958 ± 0.0196 mas[2] |
| Distance | 1,920 ± 20 ly (590 ± 7 pc) |
| Orbit | |
| Period (P) | 3.2785566 h[3] |
| Semi-major axis (a) | 1.14±0.06 R☉[4] |
| Inclination (i) | 82±4[4]° |
| Details | |
| White dwarf | |
| Mass | 0.77±0.07[4] M☉ |
| Radius | 0.012±0.001[4] R☉ |
| Surface gravity (log g) | 8[4] (assumed) cgs |
| Temperature | 50,000±1,000[4] K |
| Red dwarf | |
| Mass | 0.25±0.05[6] M☉ |
| Radius | 0.34±0.04[4] R☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
In 1982, R. F. Green and associates identified this star as a cataclysmic variable candidate with the Palomar–Green survey designation PG 1030+590.[9] A. W. Shafter and F. V. Hessman in 1984 found this to be a close eclipsing binary system with a period of 3.27 hours.[10] This is a nova-like binary where mass is being transferred from a late-type star to a white dwarf companion. This material is first accumulated in an accretion disk orbiting the white dwarf. Typically, the light curve for an eclipsing binary of this type should display a hump-like feature from where the stream of material interacts with the disk. However, during early observations, no such feature was observed before the eclipse.[11]
The behavior of the emission lines in the spectrum of this star were found to resemble those of other SW Sextantis variables.[12] In 2000, the system was observed with the Hubble Space Telescope and was found to be in a low state about three magnitudes fainter, unlike previous observations where it had been in a high state. Comparison of the ultraviolet spectrum in the two states suggested that the accretion disk is self-eclipsing and it can obscure the view of the white dwarf.[8] The light output of the system undergoes a 13.6 year cycle of variation, probably because of precession of the accretion disk. Both positive and negative superhumps are observed that vary over time in a complex fashion. Mass is being transferred from the donor star at a rate of about 10−8 M☉·yr−1.[6]
References
Further reading
- Smak, J. (September 2017), "DW UMa and the Irradiation Modulated Mass Transfer Model for Superhumps", Acta Astronomica, 67 (3): 273–280, arXiv:1705.03682, Bibcode:2017AcA....67..273S, doi:10.32023/0001-5237/67.3.5, S2CID 119184318.
- Sanad, M. R. (February 2014), "Ultraviolet spectral behavior of IP Peg and DW UMa in high, intermediate and low states from the HST and IUE satellites", New Astronomy, 27: 63–72, Bibcode:2014NewA...27...63S, doi:10.1016/j.newast.2013.09.003.
- Hoard, D. W.; et al. (November 2010), "Simultaneous X-ray and Ultraviolet Observations of the SW Sextantis Star DW Ursae Majoris", The Astronomical Journal, 140 (5): 1313–1320, Bibcode:2010AJ....140.1313H, doi:10.1088/0004-6256/140/5/1313, S2CID 26684088.
- Boyd, D. (August 2008), "Observing DW UMa - a very active variable star", Journal of the British Astronomical Association, 118 (4): 222, Bibcode:2008JBAA..118..222B.
- Ostrova, N. I.; et al. (April 2005), "Wavelength Dependence of the Orbital Variability of the Eclipsing Nova-Like Object DW UMa", Astrophysics and Space Science, 296 (1–4): 473–476, Bibcode:2005Ap&SS.296..473O, doi:10.1007/s10509-005-4894-0.
- Knigge, Christian; et al. (November 2004), "Time-resolved Ultraviolet Spectroscopy of the SW Sex Star DW UMa: Confirmation of a Hidden White Dwarf and the Ultraviolet Counterpart to Phase 0.5 Absorption Events", The Astrophysical Journal, 615 (2): L129–L132, arXiv:astro-ph/0410292, Bibcode:2004ApJ...615L.129K, doi:10.1086/426118, S2CID 118988616.
- Stanishev, V.; et al. (March 2004), "Accretion disc evolution in DW Ursae Majoris: A photometric study", Astronomy and Astrophysics, 416 (3): 1057–1067, arXiv:astro-ph/0403370, Bibcode:2004A&A...416.1057S, doi:10.1051/0004-6361:20034145, S2CID 8811798.
- Hoard, D. W.; et al. (November 2003), "Observations of the SW Sextantis Star DW Ursae Majoris with the Far Ultraviolet Spectroscopic Explorer", The Astronomical Journal, 126 (5): 2473–2486, arXiv:astro-ph/0307424, Bibcode:2003AJ....126.2473H, doi:10.1086/378605, S2CID 119099638.
- Bíró, I. B. (January 2002), Gänsicke, B. T.; et al. (eds.), "Photometric followup of DW UMa", The Physics of Cataclysmic Variables and Related Objects, ASP Conference Proceedings, 261, San Francisco: Astronomical Society of the Pacific: 469, Bibcode:2002ASPC..261..469B, ISBN 1-58381-101-X.
- Bíró, I. B. (December 2000), "Eclipse mapping of the cataclysmic variable DW Ursae Majoris", Astronomy and Astrophysics, 364: 573–586, Bibcode:2000A&A...364..573B.
- Bíró, I. B. (1998), Dusek, J. (ed.), "CCD Photometry of the Eclipsing Nova-like Variable DW Ursae Majoris", Proceedings of the 20th Stellar Conference of the Czech and Slovak Astronomical Institutes. 5th - 7th November 1997. Brno, Czech Republic, Brno, p. 30, Bibcode:1998vsr..conf...30B, ISBN 80-85882-08-6.
- Dhillon, V. S.; et al. (February 1994), "Observations of the eclipsing nova-like variable DW Ursae Majoris in a low state", Monthly Notices of the Royal Astronomical Society, 266 (4): 859–871, Bibcode:1994MNRAS.266..859D, doi:10.1093/mnras/266.4.859.
- Honeycutt, R. K.; et al. (September 1993), "The Long-Term Light Curve of the Cataclysmic Variable DW Ursae Majoris", Publications of the Astronomical Society of the Pacific, 105: 922, Bibcode:1993PASP..105..922H, doi:10.1086/133256, S2CID 43401200.
- Kazennova, E. A.; Shugarov, S. Yu. (1992), Vogt, Nikolaus (ed.), "The Photometry and Analysis of the Light Curves of the Cataclysmic Variables AY PSC and DW UMa", Vina del Mar Workshop on Cataclysmic Variable Stars, ASP Conference Series, vol. 29, San Francisco: Astronomical Society of the Pacific, p. 390, Bibcode:1992ASPC...29..390K.
- Green, R. F.; et al. (August 1991), "Cataclysmic variable candidates from the Palomar Green Survey", Astronomical Journal, 102: 683, Bibcode:1991AJ....102..683T, doi:10.1086/115902.
- Szkody, Paula; Piche, Francois (September 1990), "The Phase 0.5 Absorption in V1315 Aquilae, SW Sextantis, and DW Ursae Majoris", Astrophysical Journal, 361: 235, Bibcode:1990ApJ...361..235S, doi:10.1086/169188.
- Hessman, F. V. (February 1990), Green, D. W. E. (ed.), "DW Ursae Majoris", IAU Circular, 4971: 1, Bibcode:1990IAUC.4971....1H.
- Andronov, I. L.; et al. (October 1989), "Detection of the 224-min Orbital Period of the Cataclysmic Variable PG 0818+513", Information Bulletin on Variable Stars, 3388: 1, Bibcode:1989IBVS.3388....1A.
- Shafter, A. W.; et al. (April 1988), "Photometric and Spectroscopic Observations of the Eclipsing Nova-like Variable PG 1030+590 (DW Ursae Majoris)", Astrophysical Journal, 327: 248, Bibcode:1988ApJ...327..248S, doi:10.1086/166186.