TX Ursae Majoris is aneclipsing binarystar system in the northerncircumpolar constellation ofUrsa Major. With a combinedapparent visual magnitude of 6.97,[3] the system is too faint to be readily viewed with thenaked eye. The pair orbit each other with a period of 3.063 days in a circular orbit,[7] with theirorbital plane aligned close to the line of sight from the Earth. During the primary eclipse, the net brightness decreases by 1.74 magnitudes, while the secondary eclipse results in a drop of just 0.07 magnitude.[5] TX UMa is located at a distance of approximately 780 light years from theSun based onparallax measurements,[2] but is drifting closer with a meanradial velocity of −13 km/s.[6]
In 1931,H. Rügemer and H. Schneller independently discovered this is an eclipsing binary system of theAlgol type.[11] Rügemer later found that the eclipse period was not constant,[12] a behavior that was subsequently explained asapsidal precession.[13]B. Cester and associates in 1977 confirmed this is asemidetached binary system consisting of amain sequence primary star and anevolvedgiant companion.[14] A study of the system byJ. M. Kreiner andJ. Tremko in 1980 disproved that changes in the eclipse period are due to apsidal motion.[12]
Thelight curve of this system shows little impact from proximity effects between the two stars, making it only weakly interacting. The primary eclipse is very deep with less than 5% of the brighter star's light appearing at central eclipse,[15] allowing thespectrum of the fainter secondary to be directly examined.[16] In addition to a steady decrease in the systemorbital period, multiple irregular changes in the period were observed between 1903 and 1996.[17] The slowing orbit may be due in part from magnetic breaking of the mass-donor secondary, causing a transfer ofangular momentum to the system. An accretion disk may be a contributing factor.[18] Spectral evidence supports anaccretion disk in orbit around the primary that is sustained by mass transfer.[19] A faint emission from the system is evidence of a circumbinary ionized shell.[20]
The cooler secondary component is the moreevolved member of the pair with astellar classification of G0III-I,[4] having previously exhausted the supply of hydrogen at its core and evolved off the main sequence. This star has filled itsRoche lobe and is contributing mass to the primary.[8] It now has 1.2 times the Sun's mass but has expanded to 4.2 times the solar radius.[8] The secondary is rotating synchronously with its orbit.[8] The primary component of this system is aB-type main-sequence star with astellar classification of B8V.[4] It is rotating 1.5[8] times as fast as the orbital rate due to the impact of mass accretion from the secondary.[4] The primary has 4.8 times the mass and 2.8 times the radius of the Sun.[8]
^abcdKomžík, R.; et al. (June 2008), "Asynchronous rotation of the mass gaining component in the Algol-type binary TX UMa",Contributions of the Astronomical Observatory Skalnaté Pleso,38 (3):538–544,Bibcode:2008CoSka..38..538K.
^Komzik, R.; et al. (December 1992), "Spectroscopic and Photometric Detection of Interacting Processes and Their Evolution in the Eclipsing Binary Tx-Ursae",Astrophysics and Space Science,198 (1):149–159,Bibcode:1992Ap&SS.198..149K,doi:10.1007/BF00644309,S2CID123353083.
^abKreiner, J. M.; Tremko, J. (1980), "Analysis of the Change of Period and the Photometry of the Minima of the Eclipsing Binary System TX Ursae Maioris",Bulletin of the Astronomical Institute of Czechoslovakia,31: 343,Bibcode:1980BAICz..31..343K.
^Plavec, M. (1960), "Influence of precession and nutation on the period of eclipsing variables",Bulletin of the Astronomical Institute of Czechoslovakia,11: 197,Bibcode:1960BAICz..11..197P.
^Cester, B.; et al. (November 1977), "Revised photometric elements of 12 semi-detached systems",Astronomy and Astrophysics,61:469–475,Bibcode:1977A&A....61..469C.
^Hill, Graham; Hutchings, J. B. (January 1973), "The Synthesis of Close-Binary Light Curves IV. An Application to TX Ursae Majoris and MR Cygni",Astrophysics and Space Science,20 (1):123–148,Bibcode:1973Ap&SS..20..123H,doi:10.1007/BF00645591,S2CID119821890.
^Qian, Shengbang (November 2001), "Possible Mass and Angular Momentum Loss in Algol-Type Binaries. V. RT Persei and TX Ursae Majoris",The Astronomical Journal,122 (5):2686–2691,Bibcode:2001AJ....122.2686Q,doi:10.1086/323455,S2CID121698690.
^Iliev, L. (December 2010), Prša, Andrej; Zejda, Miloslav (eds.), "Spectral Evidence of Circumstellar Material in the Eclipsing Binary TX UMa",Binaries - Key to Comprehension of the Universe. Proceedings of a conference held June 8-12, 2009 in Brno, Czech Republic, vol. 435, San Francisco: Astronomical Society of the Pacific, p. 345,Bibcode:2010ASPC..435..345I.
^Taranova, O. G.; Shenavrin, V. I. (November 1997), "Search for dust shells in W Ser binaries and similar object: RX Cassiopeiae and TX Ursae Majoris",Astronomy Letters,23 (6):698–703,Bibcode:1997AstL...23..698T.
Screech, James (June 2020), "Algol type eclipsing binary TX UMa. Can all sources have the correct period?",British Astronomical Association Variable Star Section Circular,184 (184):36–37,Bibcode:2020BAAVC.184...36S.
Maxted, P. F. L.; et al. (September 1995), "Studies of early-type variable stars. XIII. Spectroscopic orbit and absolute parameters of TX Ursae Majoris",Astronomy and Astrophysics,301: 135,Bibcode:1995A&A...301..135M.
Hric, L.; Komzik, R. (March 1992), "The Eclipsing Binary TX UMa - a Period Change again",Information Bulletin on Variable Stars,3698 (1): 1,Bibcode:1992IBVS.3698....1H.
Oh, Kyu-Dong (June 1986), "Photometric Orbit of TX UMa",Journal of Astronomy and Space Science,3 (1):41–51,Bibcode:1986JASS....3...41O.
Pearce, J. A. (November 1932), "The Spectroscopic Elements of the Eclipsing Variable TX Ursae Majoris",Journal of the Royal Astronomical Society of Canada,26: 382,Bibcode:1932JRASC..26..382P.
