SW Ursae Majoris is a cataclysmic binary star system in the northern circumpolar constellation of Ursa Major, abbreviated SW UMa. During quiescence it has an apparent visual magnitude of 16.5–17, which is too faint to be visible to the naked eye.[8] Based on parallax measurements, it is located at a distance of approximately 526 light years from the Sun.[2]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ursa Major |
| Right ascension | 08h 36m 42.749s[2] |
| Declination | +53° 28′ 37.98″[2] |
| Apparent magnitude (V) | 9.7 to 16.5[3] |
| Characteristics | |
| Variable type | U Gem[3] |
| Astrometry | |
| Proper motion (μ) | RA: −28.713 mas/yr[2] Dec.: 5.928 mas/yr[2] |
| Parallax (π) | 6.2002 ± 0.0602 mas[2] |
| Distance | 526 ± 5 ly (161 ± 2 pc) |
| Absolute magnitude (MV) | +4.9 (at maximum)[4] |
| Details | |
| White dwarf | |
| Mass | 0.61+0.06 −0.04[5] M☉ |
| Radius | 0.0129+0.0009 −0.0010[5] R☉ |
| Surface gravity (log g) | 8.01+0.11 −0.09[5] cgs |
| Temperature | 13,854+189 −131[5] K |
| donor | |
| Mass | 0.1[6] M☉ |
| Luminosity | 0.001[6] L☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
The variable nature of this object was noted by L. Tseraskaya in 1909 when it increased in brightness to 10th magnitude.[9][10] It was determined to be a U Geminorum star, indicating this is a binary star system.[11] A short orbital period of 81.8 minutes was determined by A. W. Shafter and associates in 1986.[12] The same year, E. L. Robinson and associates detected superhumps with a period of 84.0 minutes.[1] Large amplitude quasi-periodic oscillations were observed by T. Kato and associates in 1992, which is a property of SU UMa-type dwarf novae.[13]
When the system is in a quiet period, it displays a periodicity of 15.9 minutes and has a marginal emission of soft X-rays. This is likely the rotation period of the white dwarf, and the system resembles an intermediate polar with a strongly-magnetized white dwarf as the accreting component.[8] It undergoes outbursts that vary in brightness and duration.[14] During quiescence, it is estimated that about 70% of the bolometric luminosity of the system is produced by the white dwarf, with almost all the rest produced by the accretion disk.[15]
References
Further reading
- Perez-Garcia, I.; et al. (October 2021), "Observations with the BOOTES Network of the current outburst in the dwarf-nova SW UMa", The Astronomer's Telegram, 14960: 1, Bibcode:2021ATel14960....1P.
- 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.
- Waagen, E. O.; et al. (September 2006), Green, D. W. E. (ed.), "SW Ursae Majoris", IAU Circular, vol. 8748, p. 2, Bibcode:2006IAUC.8748....2W.
- Povich, M. S.; et al. (December 2004), "Far Ultraviolet Spectroscopic Explorer Observations of the Dwarf Nova SW Ursae Majoris during Quiescence", The Astrophysical Journal, 617 (1): 500–507, arXiv:astro-ph/0409588, Bibcode:2004ApJ...617..500P, doi:10.1086/425213, S2CID 31384959.
- Burleigh, M. R.; et al. (August 2001), "A ROSAT WFC observation of SW UMa: the EUV behaviour of dwarf novae in superoutburst explained", Monthly Notices of the Royal Astronomical Society, 325 (4): 1458–1462, arXiv:astro-ph/0104010, Bibcode:2001MNRAS.325.1458B, doi:10.1046/j.1365-8711.2001.04551.x, S2CID 12041296.
- Pavlenko, E. P.; et al. (October 2000), "CCD Photometry of the Cataclysmic Variable SW Ursae Majoris at a Late Stage of the 2000 Superoutburst", Astrophysics (English translation of Astrofizika), vol. 43, no. 4, pp. 419–429, Bibcode:2000Ap.....43..419P, doi:10.1023/A:1010914924206, S2CID 117641368.
- Mattei, J. A.; et al. (February 2000), Green, D. W. E. (ed.), "SW Ursae Majoris", IAU Circular, vol. 7365, p. 2, Bibcode:2000IAUC.7365....2M.
- Gänsicke, B. T.; Koester, D. (June 1999), "SW Ursae Majoris, CU Velorum and AH Mensae: three more accreting white dwarfs unveiled?", Astronomy and Astrophysics, 346: 151–157, Bibcode:1999A&A...346..151G.
- Nogami, Daisaku; et al. (April 1998), "CCD Photometry of SW Ursae Majoris during the 1996 Superoutburst", Publications of the Astronomical Society of Japan, 50 (2): 297–302, Bibcode:1998PASJ...50..297N, doi:10.1093/pasj/50.2.297.
- Mobberley, M. P.; et al. (April 1997), "C. R. d'Esterre and the mysteries of UV and UW Per", Journal of the British Astronomical Association, 107 (2): 65–71, Bibcode:1997JBAA..107...65M.
- Semeniuk, I.; et al. (January 1997), "CCD Photometry of SW Ursae Majoris during the 1996 Superoutburst", Acta Astronomica, 47: 201–209, arXiv:astro-ph/9704215, Bibcode:1997AcA....47..201S.
- Rosen, S. R.; et al. (August 1994), "ROSAT constraints on the intermediate polar candidates V426 Oph, SW UMa and 1H 0709-360." (PDF), Monthly Notices of the Royal Astronomical Society, 269 (4): 913–920, Bibcode:1994MNRAS.269..913R, doi:10.1093/mnras/269.4.913.
- Szkody, Paula; et al. (May 1988), "EXOSAT and IUE Observations of SW UMa during Superoutburst", Astrophysical Journal, 328: 243, Bibcode:1988ApJ...328..243S, doi:10.1086/166286.