RW Ursae Minoris

RW Ursae Minoris (Nova Ursae Minoris 1956) is a cataclysmic variable star system that flared up as a nova in the constellation Ursa Minor in 1956. Although the nova eruption occurred in 1956, it was not noticed until nearly six years later when, in 1962, V. Satyvaldiev found it on sky-patrol plates of the Astrophysical Institute of the Tajik Academy of Sciences in Dushanbe. On 24 September 1956 it had an apparent magnitude of 6.[4] It may have been as bright as magnitude 3.5 around 19 September 1956, which would have made it easily visible to the naked eye, but the full moon on 20 September 1956 would have hampered observations around that date.[5] RW Ursae Minoris's pre-nova brightness was about magnitude 21, but early in the 21st century is was still two magnitudes brighter than that.[6]

RW Ursae Minoris
Location of RW Ursae Minoris (circled in red)
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Minor
Right ascension 16h 47m 54.8194s[1]
Declination +77° 02′ 12.061″[1]
Apparent magnitude (V) 6 Max.
>21 Min.[2]
Astrometry
Proper motion (μ) RA: −0.739±0.359[1] mas/yr
Dec.: −2.812±0.486[1] mas/yr
Parallax (π)0.4718 ± 0.1929[1] mas
Distance1510+564
−199[2] pc
Characteristics
Variable type classical nova
Other designations
AAVSO 1651+77, Nova UMi 1956, Gaia DR2 1704994848488583552[2][3]
Database references
SIMBADdata

Novae tend to be found near the galactic plane, but RW Ursae Minoris has a galactic latitude of 33 degrees, which is far from the plane of the Milky Way. Because of this, and its large outburst amplitude, astronomers were initially unsure about whether RW Ursae Minoris was a nova in the Milky Way or a supernova in another galaxy.[4][7] It was eventually identified as a nova in the galactic halo on the basis of its light curve and spectrum.[5][8]

All novae are binary stars, with a "donor" star orbiting a white dwarf. The donor star is so close to the white dwarf that material from the donor is transferred to the white dwarf. In 1995 Retter and Lipkin detected a low amplitude (0.1 - 0.2 magnitude) variation in RW Ursae Minoris's brightness with a period of 1.4 hours. They argued that this 1.4 hour period is probably the orbital period of the binary pair, which would make it the shortest period orbit for any known nova.[9]

RW Ursae Minoris is surrounded by a small nova remnant shell. In 1985, Judith Cohen reported its radius as 1 arc second based observations with the Hale Telescope.[10] In 1995 Esenoglu et al. observed it with the Copernico 1.82 m telescope and measured a diameter of ~1.5 arc second diameters).[11]

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. Schaefer, Bradley E. (2018). "The distances to Novae as seen by Gaia". Monthly Notices of the Royal Astronomical Society. 481 (3): 3033–3051. arXiv:1809.00180. Bibcode:2018MNRAS.481.3033S. doi:10.1093/mnras/sty2388. S2CID 118925493.
  3. "RW Ursae Minoris". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-08-18.
  4. Kukarkin, B.V. (December 1962). "Nova or Supernova". Information Bulletin on Variable Stars. 18 (1). Retrieved 28 December 2020.
  5. Ahnert, P. (January 1963). "Nova Ursae Minoris 1956". Information Bulletin on Variable Stars. 19: 1. Retrieved 28 December 2020.
  6. Bianchini, A.; Tappert, C.; Canterna, R.; Tamburini, F.; Osborne, H.; Cantrell, K. (2003). "RW Ursae Minoris (1956): An Evolving Postnova System". The Publications of the Astronomical Society of the Pacific. 115 (809): 811–18. Bibcode:2003PASP..115..811B. doi:10.1086/376434.
  7. Efremov, Y.N. (January 1962). "SVS 1359 - Nova with large amplitude or supernova". Astronomicheskii Tsirkulyar. 232: 2–3. Retrieved 28 December 2020.
  8. Duerbeck, H.W. (January 1985). "Novae in the galatic halo?". Mitteilungen der Astronomischen Gesellschaft. 63: 190. Retrieved 28 December 2020.
  9. Retter, A.; Lipkin, Y. (January 2001). "The detection of a 1.4-h period in RW Ursa Minoris - candidate for shortest recorded orbital period nova". Astronomy and Astrophysics. 365: 508–513. doi:10.1051/0004-6361:20000150. Retrieved 28 December 2020.
  10. Cohen, J.G. (May 1985). "Nova shells. II. Calibration of the distance scale using novae". The Astrophysical Journal. 292: 90–103. doi:10.1086/163135. Retrieved 28 December 2020.
  11. Esenoglu, H.H.; Saygac, A.T.; Bianchini, A.; Retter, A.; Ozkan, M.T.; Altan, M. (December 2000). "A study of RW Ursae Minoris shell". Astronomy and Astrophysics. 364: 191–198. Retrieved 28 December 2020.
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