The variability of this system was discovered by
W. Strohmeier and its period was determined by
R. Kippenhahn, with the findings announced in 1955.[11] It was found to be a
detachedeclipsing binary system, and by 1963 a
variable primary component had been noted.[12]E. H. Geyer made intermittent
light curve studies of the system starting with its discovery up until 1975,[11] ascribing variability in the light curve to
star spot activity on the primary component. The orbital period of the pair was determined to be 0.479 d,[13] with the
orbital plane inclined at an angle of 79.84° to the line of sight from the Earth.[8]
By 1990, enough data had been collected to identify a long term variation of the period, and it was hypothesized this was caused by a third body in the system orbiting the close binary.[14] The orbital period of this component was estimated to be ~30 years in 2001,[15] then refined to 26.7 years by 2010. If the
orbital plane of this component is the same as the inner pair, its mass would be 18% of the mass of the Sun. An alternative solution to the period change suggests magnetic activity causes shifts in the
angular momentum of the system, but this is considered less likely.[8]
^
abGeyer, E. H. (1976), Eggleton, P.; et al. (eds.), "Starspot Activities as an Interpretation for the Light Curve Changes of the Close Binary Star XY UMA", Structure and Evolution of Close Binary Systems; Proceedings of the Symposium, Cambridge, England, July 28-August 1, 1975, vol. 73, no. 73, Dordrecht: D. Reidel Publishing Co., p. 313,
Bibcode:
1976IAUS...73..313G. Symposium sponsored by the International Astronomical Union.{{
citation}}: CS1 maint: postscript (
link)
^Lorenzi, L.; Scaltriti, F. (1977), "The variable light-curve of the eclipsing binary XY UMa", Acta Astronomica, 27: 273–279,
Bibcode:
1977AcA....27..273L.
^Geyer, E. H. (May 1977), "Remarks on Erratic Period Fluctuations of Detached Close Binaries and the Constancy of the Orbital Period of XY UMa", Astrophysics and Space Science, 48 (1): 137–144,
Bibcode:
1977Ap&SS..48..137G,
doi:
10.1007/BF00643045,
S2CID120596800.
^Pojmanski, G.; Geyer, E. H. (1990), "The period behaviour of the spotted binary XY UMa", Acta Astronomica, 40: 245,
Bibcode:
1990AcA....40..245P.
Sowell, James R.; et al. (October 2001), "Period Changes in Four Short-Period Spotted Binaries: UV Piscium, YY Geminorum, CG Cygni, and XY Ursae Majoris", The Astronomical Journal, 122 (4): 1965–1973,
Bibcode:
2001AJ....122.1965S,
doi:10.1086/323091,
S2CID121917917.
Yeates, C. M.; et al. (August 2000), "Times of Minimum Light for XY Ursae Majoris", Information Bulletin on Variable Stars, 4943 (1): 1,
Bibcode:
2000IBVS.4943....1Y.
Kjurkchieva, D.; et al. (February 2000), "Multicolour high-speed photometry and Hα spectroscopy of XY UMa", Astronomy and Astrophysics, 354: 909–914,
Bibcode:
2000A&A...354..909K.
Arévalo, M. J.; Lázaro, C. (August 1999), "Time-resolved Spectroscopy of RS Canum Venaticorum Short-Period Systems. II. RT Andromedae, WY Cancri, and XY Ursae Majoris", The Astronomical Journal, 118 (2): 1015–1033,
Bibcode:
1999AJ....118.1015A,
doi:10.1086/300952,
S2CID121443644.
Chochol, D.; et al. (December 1998), "The RS CVn binary XY UMa as a member of a triple system", Astronomy and Astrophysics, 340: 415–418,
Bibcode:
1998A&A...340..415C.
Pojmanski, G. (December 1998), "Orbital Solutions for Three RS CVn Systems: WY Cnc, SV Cam and XY UMa", Acta Astronomica, 48: 711–727,
Bibcode:
1998AcA....48..711P.
Erdem, A.; Gudur, N. (January 1998), "The orbital period study and photometric analysis of XY Ursae Majoris", Astronomy and Astrophysics Supplement, 127 (2): 257–267,
Bibcode:
1998A&AS..127..257E,
doi:10.1051/aas:1998348.
Pojmanski, G.; Udalski, A. (October 1997), "An Orbital Solution for RS CVn Binary Star XY UMa", Acta Astronomica, 47: 451–466,
Bibcode:
1997AcA....47..451P.
Collier Cameron, A.; Hilditch, R. W. (May 1997), "Eclipse mapping of starspots on XY UMa in 1992 and 1995", Monthly Notices of the Royal Astronomical Society, 287 (3): 567–574,
Bibcode:
1997MNRAS.287..567C,
doi:10.1093/mnras/287.3.567.
Jeffries, R. D.; et al. (December 1995), "V-Band Photometry of XY UMa in 1993 and 1995", Information Bulletin on Variable Stars, 4277 (1): 1,
Bibcode:
1995IBVS.4277....1J.
Hilditch, R. W.; Bell, S. A. (April 1994), "High Precision Photometry of the RS-Canum Binary System XY-Ursae and a Dark-Zone Photometric Model", Monthly Notices of the Royal Astronomical Society, 267 (4): 1081,
Bibcode:
1994MNRAS.267.1081H,
doi:10.1093/mnras/267.4.1081.
Rainger, P. P.; et al. (January 1991), "Spectroscopic observations of the RS CVn-type binary systems SV Cam and XY UMa", Monthly Notices of the Royal Astronomical Society, 248: 168,
Bibcode:
1991MNRAS.248..168R,
doi:10.1093/mnras/248.1.168.
Geyer, E. H. (1991), "On the long term variability of the chromospheric active close binary XY Ursae Majoris", Astronomische Gesellschaft Abstract Series, 6: 79,
Bibcode:
1991AGAb....6...79G.
Zeilik, M.; et al. (October 1990), "1990 BVR Photometry of XY UMa", Information Bulletin on Variable Stars, 3535 (1): 1,
Bibcode:
1990IBVS.3535....1Z.
Bedford, D. K.; et al. (April 1990), "Coronal X-ray emission from the short-period eclipsing binary XY UMa", Monthly Notices of the Royal Astronomical Society, 243: 557–564,
Bibcode:
1990MNRAS.243..557B.
Arevalo, M. J.; Lazaro, C. (March 1990), "Infrared Photometry of the RS CVn Short-Period Systems XY UMa and WY CNC", Astronomical Journal, 99: 983,
Bibcode:
1990AJ.....99..983A,
doi:
10.1086/115389.
Banks, T.; Budding, E. (March 1989), "Light Curves for XY UMa", Information Bulletin on Variable Stars, 3304 (1): 1,
Bibcode:
1989IBVS.3304....1B.
Heckert, P.; et al. (October 1988), "1987 Photometry of XY Ursae Majoris", Information Bulletin on Variable Stars, 3253 (1): 1,
Bibcode:
1988IBVS.3253....1H.
Zeilik, M.; et al. (June 1988), "1988 BVRI Photometry of XY UMa", Information Bulletin on Variable Stars, 3200 (1): 1,
Bibcode:
1988IBVS.3200....1Z.
Bedford, D. K.; et al. (October 1986), "The X-Ray Light Curve of XY Ursae Maioris", Information Bulletin on Variable Stars, 2946 (1): 1,
Bibcode:
1986IBVS.2946....1B.
Bedford, D. K.; Geyer, E. H. (1986), "Simultaneous Optical- and EXOSAT-Observations of the Spot Active Eclipsing Binary XY UMa", Mitteilungen der Astronomischen Gesellschaft, 67: 305,
Bibcode:
1986MitAG..67..305B.
Zeilik, M.; et al. (April 1983), "The short-period eclipsing system XY UMa : 1982 UBV light curves and a flare-like event", Astronomical Journal, 88: 532–534,
Bibcode:
1983AJ.....88..532Z,
doi:
10.1086/113339.
Zeilik, M.; et al. (September 1982), "An Intense Optical Flare from XY UMa", Information Bulletin on Variable Stars, 2200 (1): 1,
Bibcode:
1982IBVS.2200....1Z.
Zeilik, M.; et al. (June 1982), "1982 UBVR Photometric Observations of XY UMa", Information Bulletin on Variable Stars, 2169: 1,
Bibcode:
1982IBVS.2169....1Z.