ER Ursae Majoris is a variable star in the northern circumpolar constellation of Ursa Major, abbreviated ER UMa. It is a prototype system for a subclass of SU Ursae Majoris dwarf novae.[5] The system ranges in brightness from a peak apparent visual magnitude of 12.4 down to 15.2,[3] which is too faint to be visible to the naked eye. The distance to this system, based on parallax measurements, is approximately 1,163 light years.[2]
 A visual band light curve for ER Ursae Majoris. The main plot shows a normal outburst in 2004, with the estimated value for the unobserved maximum plotted in red. The inset plot shows superhump oscillations. Adapted from Zhao et al. (2006).[1] | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ursa Major |
| Right ascension | 09h 47m 11.941s[2] |
| Declination | +51° 54′ 08.95″[2] |
| Apparent magnitude (V) | 12.4 to 15.2[3] |
| Characteristics | |
| Variable type | Dwarf nova(?)[3] |
| Astrometry | |
| Proper motion (μ) | RA: 33.659 mas/yr[2] Dec.: −6.209 mas/yr[2] |
| Parallax (π) | 2.8039 ± 0.0205 mas[2] |
| Distance | 1,163 ± 9 ly (357 ± 3 pc) |
| Orbit[4] | |
| Period (P) | 0.06366±0.00003 d |
| Eccentricity (e) | 0.00 (assumed) |
| Inclination (i) | 18–50[5]° |
| Periastron epoch (T) | 2,449,740.0637±0.0008 HJD |
| Argument of periastron (ω) (secondary) | 0.00 (assumed)° |
| Semi-amplitude (K1) (primary) | 48±4 km/s |
| Details | |
| White dwarf | |
| Mass | 1.0±0.2[5] M☉ |
| Temperature | 32,000[5] K |
| Donor star | |
| Mass | 0.10[5] M☉ |
| Other designations | |
| Database references | |
| SIMBAD | data |
This system was identified as an ultraviolet excess object as part of the Palomar-Green (PG) survey by R. F. Green and associate in 1986. It was given the catalog identifier PG 0943+521, and was confirmed to be cataclysmic variable. In 1992, it was determined this is a dwarf nova that ranges in brightness from magnitude 12.3 down to 15.2. F. A. Ringwald in 1993 found a candidate orbital period of 0.1997 days based on radial velocity variation, but with some uncertainty.[7]
In 1995, T. Kato and C. Kunjaya confirmed this is a SU Ursae Majoris-type dwarf nova, and noted the unusual nature of this system, finding it has a long superoutburst lasting about 20 days and the supercycle (the time between superoutbursts) is very short at around 43 days.[8] Large amplitude superhumps were found to occur near the start of a superoutburst, with a brightness increase of around 0.35 magnitude.[9] The properties of the system suggest a high mass transfer rate and the white dwarf component is hotter than in other typical dwarf novae. During periods of quiescence, the accretion rate is 7.3×10−11 M☉·yr−1.[5]
References
Further reading
- Zemko, P.; et al. (March 2014), "Study of a long and short—term variability of ER Ursae Majoris", Contributions of the Astronomical Observatory Skalnaté Pleso, 43 (3): 319–324, Bibcode:2014CoSka..43..319Z.
- Zemko, Polina; et al. (June 2013), "Detection of Change in Supercycles in ER Ursae Majoris", Publications of the Astronomical Society of Japan, 65 (3): 8, arXiv:1212.5940, Bibcode:2013PASJ...65...54Z, doi:10.1093/pasj/65.3.54, 54.
- Ohshima, Tomohito; et al. (August 2012), "Discovery of Negative Superhumps during a Superoutburst of 2011 January in ER Ursae Majoris", Publications of the Astronomical Society of Japan, 64 (4): L3, arXiv:1207.2705, Bibcode:2012PASJ...64L...3O, doi:10.1093/pasj/64.4.L3.
- Kjurkchieva, D.; Marchev, D. (September 2010), "Large-Amplitude Modulations of the Cataclysmic Star ER UMa", Publications of the Astronomical Observatory of Belgrade, 90: 147–150, Bibcode:2010POBeo..90..147K.
- Kato, Taichi; et al. (April 2003), "Unusual Phase Reversal of Superhumps in ER Ursae Majoris", Publications of the Astronomical Society of Japan, 55 (2): L7–L10, arXiv:astro-ph/0211520, Bibcode:2003PASJ...55L...7K, doi:10.1093/pasj/55.2.L7.
- Gao, Weihong; et al. (December 1999), "Superhumps in a Peculiar SU Ursae Majoris-Type Dwarf Nova, ER Ursae Majoris", The Astrophysical Journal, 527 (1): L55–L59, arXiv:astro-ph/9910558, Bibcode:1999ApJ...527L..55G, doi:10.1086/312398, PMID 10566998, S2CID 16090638.
- Szkody, P.; et al. (1996), Evans, A.; Wood, Janet H. (eds.), "IUE and Optical Spectra of RZ LMi and ER UMa Throughout their 19 and 43 Day Cycles", Cataclysmic variables and related objects. Proceedings of the 158th colloquium of the International Astronomical Union (IAU); held at Keele; United Kingdom; June 26-30; 1995, Astrophysics and Space Science Library, vol. 208, Dordrecht: Kluwer Academic Publishers, p. 55, Bibcode:1996ASSL..208...55S, doi:10.1007/978-94-009-0325-8_15, ISBN 978-94-010-6632-7, S2CID 197532794.
- Kato, Taichi; et al. (August 1995), "Photometric Detection of the Orbital Period in ER UMa", Information Bulletin on Variable Stars, 4233: 1, Bibcode:1995IBVS.4233....1K.
- Osaki, Yoji (April 1995), "A Model for a Peculiar SU Ursae Majoris-Type Dwarf Nova ER Ursae Majoris", Publications of the Astronomical Society of Japan, 47: L11–L14, Bibcode:1995PASJ...47L..11O.
- Robertson, J. W.; et al. (May 1995), "RZ Leonis Minoris, PG 0943+521, and V1159 Orionis: Three Cataclysmic Variables with Similar and Unusual Outburst Behavior", Publications of the Astronomical Society of the Pacific, 107: 443, Bibcode:1995PASP..107..443R, doi:10.1086/133572, S2CID 119609461.