UX Ursae Majoris

UX Ursae Majoris is an Algol type binary star system in the northern circumpolar constellation of Ursa Major. It is classified as a nova-like variable star similar to DQ Herculis, although no eruptions have been reported.[11] Since its discovery in 1933, this system has been the subject of numerous studies attempting to determine its properties.[12] The combined apparent visual magnitude of UX UMa ranges from 12.57 down to 14.15.[3] The system is located at a distance of approximately 952 light years from the Sun based on parallax,[2] and is drifting further away with a radial velocity of 112 km/s.[6]

UX Ursae Majoris

A visual band light curve for UX Ursae Majoris, adapted from de Miguel et al. (2016).[1] The top plot shows the variation over several weeks, and the bottom plot shows the mean light curve over one orbital period.
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ursa Major
Right ascension 13h 36m 40.953s[2]
Declination +51° 54′ 49.42″[2]
Apparent magnitude (V) 12.57 to 14.15[3]
Characteristics
Spectral type sdOB[4] + M4+[5]
Variable type β Per, nova-like[3]
Astrometry
Radial velocity (Rv)112.0[6] km/s
Proper motion (μ) RA: −41.614 mas/yr[2]
Dec.: 17.180 mas/yr[2]
Parallax (π)3.4252 ± 0.0157 mas[2]
Distance952 ± 4 ly
(292 ± 1 pc)
Orbit[7]
Period (P)4.72 hours
Semi-major axis (a)1.51 – 1.61 R☉
Inclination (i)65 – 75°
Semi-amplitude (K1)
(primary)		113±11 km/s
Semi-amplitude (K2)
(secondary)		262±14 km/s
Details
White dwarf
Mass0.47[8] M☉
Radius9,700[8] km
Surface gravity (log g)7.7[9] cgs
Temperature20,000[9] K
Donor star
Mass0.47[8] M☉
Radius0.496 – 0.697[9] R☉
Surface gravity (log g)−4.65 – 4.73[9] cgs
Accretion disk
Radius0.488[9] R☉
Temperature88,450±21,230[4] K
Other designations
UX UMa, AAVSO 1332+52[10]
Database references
SIMBADdata

This system was found to be an eclipsing binary by the Soviet astronomer S. Belyavsky in 1933. At the time, the period of 4.73 hours was the shortest known for a binary star system.[12] M. Zverev and B. Kukarkin published elements from a light curve made from visual observations in 1937, while in 1939 V. A. Krat at Pulkovo Observatory produced a solution based on his photographic observations.[13] G. P. Kuiper in 1941 classified the star as a B3 subdwarf.[14] O. Struve in 1948 noted that the system underwent significant variations in its spectrum.[15] A. P. Linnell produced the first photoelectric light curve of the system in 1950, finding that the brightness underwent an increase just prior to the primary eclipse. He also noted that the system underwent rapid light variation.[13]

Observations of this system up to 1962 showed the period was changing: it increased up until 1953 then began decreasing. The depth of the eclipse was found to vary with wavelength, decreasing in depth with increasing wavelength possibly due to contributions by a cooler stellar component or surrounding material.[16] M. F. Walker and G. H. Herbig in 1954 suggested that the hump in the light curve is due to a hot spot. In 1974, R. E. Nather and E. L. Robinson proposed that the hot component is a white dwarf surrounded by a optically thick, orbiting disk of gas. The hot spot on the disk is formed by a stream of gas from the donor secondary star, and is the main source of the rapid flickering from the system.[14] The observed light curve can be reproduced by an orbital inclination of ~75° to the line of sight to the earth, with the white dwarf being almost completely obscured by its accretion disk.[11]

UX UMa is considered an archetypal example of nova-like variables that are always in a high accretion state, showing bright steady disks.[17] A photometric study of the system during 2015 found a cyclical signal with a mean period of 3.680 days and an amplitude of 0.44 in magnitude. This is interpreted as retrograde nodal precession of the accretion disk.[1] The infalling matter is creating a compact clump in the accretion disk. This is shielding illumination from the hot inner disk, forming a dark spot. Doppler tomography of the disk shows a spiral structure.[7] Observations during 1999 showed spectral features characteristic of an SW Sextantis variable, but at other times these features disappeared.[7]

References
  1. de Miguel, E.; et al. (April 2016), "Accretion-disc precession in UX Ursae Majoris", Monthly Notices of the Royal Astronomical Society, 457 (2): 1447–1455, arXiv:1512.08687, Bibcode:2016MNRAS.457.1447D, doi:10.1093/mnras/stv3014.
  2. 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.
  3. Samus', N. N; et al. (2017), "General catalogue of variable stars", Astronomy Reports, GCVS 5.1, 61 (1): 80, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
  4. Lei, Zhenxin; et al. (April 2019), "Searching for hot subdwarf stars from the LAMOST Spectra. II. Pure spectroscopic identification method for hot subdwarfs", Publications of the Astronomical Society of Japan, 71 (2): 41, arXiv:1907.00132, Bibcode:2019PASJ...71...41L, doi:10.1093/pasj/psz006.
  5. Putte, D. V.; et al. (2003), "A spectroscopic search for faint secondaries in cataclysmic variables", Monthly Notices of the Royal Astronomical Society, 342 (1): 151–162, arXiv:astro-ph/0302507, Bibcode:2003MNRAS.342..151V, doi:10.1046/j.1365-8711.2003.06524.x, S2CID 119383913.
  6. Duflot, M.; et al. (1995), "Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue", Astronomy and Astrophysics Supplement Series, 114: 269, Bibcode:1995A&AS..114..269D.
  7. Neustroev, V. V.; et al. (2011), "Dark spot, spiral waves and the SW Sextantis behaviour: It is all about UX Ursae Majoris", Monthly Notices of the Royal Astronomical Society, 410 (2): 963–977, arXiv:1006.3106, Bibcode:2011MNRAS.410..963N, doi:10.1111/j.1365-2966.2010.17495.x, S2CID 118555373.
  8. Noebauer, Ulrich M.; et al. (August 2010), "The Geometry and Ionization Structure of the Wind in the Eclipsing Nova-like Variables RW Tri and UX UMa", The Astrophysical Journal, 719 (2): 1932–1945, arXiv:1007.0209, Bibcode:2010ApJ...719.1932N, doi:10.1088/0004-637X/719/2/1932, S2CID 119208187.
  9. Linnell, Albert P.; et al. (2008), "Modeling UX Ursae Majoris: An Abundance of Challenges", The Astrophysical Journal, 688 (1): 568–582, arXiv:0807.3920, Bibcode:2008ApJ...688..568L, doi:10.1086/592104, S2CID 1648147.
  10. "UX UMa", SIMBAD, Centre de données astronomiques de Strasbourg, retrieved 2022-02-27.
  11. Petterson, J. A. (October 1980), "Accretion disks in cataclysmic variables. I. The eclipse-related phase shifts in DQ Herculis and UX Ursae Majoris", Astrophysical Journal, 241: 247–256, Bibcode:1980ApJ...241..247P, doi:10.1086/158337.
  12. Smak, J. (January 1994), "Eclipses in Cataclysmic Variables with Stationary Accretion Disks. II. UX UMa", Acta Astronomica, 44: 59–74, Bibcode:1994AcA....44...59S.
  13. Linnell, Albert P. (1950), "A Study of UX Ursae Majoris", Harvard College Observatory Circular, 455: 1–13, Bibcode:1950HarCi.455....1L.
  14. Nather, R. E.; Robinson, E. L. (June 1974), "Coherent oscillations in UX Ursae Majoris", Astrophysical Journal, 190: 637–651, Bibcode:1974ApJ...190..637N, doi:10.1086/152921.
  15. Struve, Otto (July 1948), "The Spectrum of the Eclipsing Binary UX Ursae Majoris", Astrophysical Journal, 108: 153, Bibcode:1948ApJ...108..153S, doi:10.1086/145052.
  16. Krzeminski, W.; Walker, Merle F. (July 1963), "Photoelectric Observations of UX Ursae Majoris, 1955-1962", Astrophysical Journal, 138: 146, Bibcode:1963ApJ...138..146K, doi:10.1086/147624.
  17. Ramsay, Gavin; Schreiber, Matthias R.; Gänsicke, Boris T.; Wheatley, Peter J. (2017), "Distances of cataclysmic variables and related objects derived from Gaia Data Release 1", Astronomy & Astrophysics, 604: A107, arXiv:1704.00496, Bibcode:2017A&A...604A.107R, doi:10.1051/0004-6361/201730679, S2CID 56464882.

Further reading
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