Ablue bandlight curve for OY Carinae, adapted from Khruzina1et al. (2003).[1] The main plot shows the full light curve, and the inset shows the minimum with an expanded horizontal scale.
Cuno Hoffmeister discovered that the star is a cataclysmic variable, in 1959.[11] In 1976, it was identified as a candidateSU Ursae Majoris (SU UMa)-type variable.[12] It was found to be a double eclipsing binary system by Nikolaus Vogt in 1979, who determined a period of 91 minutes.[13] This behavior potentially allows for precise determination of the physical parameters of the system.[6]Superhumps during an outburst of OY Car were reported in 1980, confirming its status as an SU UMa variable.[14]
The standard model for this type of system has a cool star orbiting a compactwhite dwarf. The cool star is filling itsRoche lobe and is feeding matter to an accretion disk orbiting the white dwarf. The eclipsing of the accretion disk allows its dimensions to be estimated.[15] The impact point of the material contacting the accretion disk produces a "hot spot", which is responsible for the superhump feature in thelight curve.[8]
By 1991, superoutbursts of OY Car were found to occur on an almost annual cycle, with a mean time interval of 346.5 days. However, individual cycles could range from 354 to 472 days. The mean maximum magnitude was 11.45, with the system being above magnitude 13 for an average of 12 days.[16] These superoutbursts are thought to occur during periods of rapid accretion onto the white dwarf, which in SU UMa systems can be triggered by tidal resonances in the disk.[17] During a superoutburst, the temperature of the white dwarf can increase to19,700 K before steadily declining.[18]
As material accretes onto the white dwarf it undergoes decelaration and emitsX-rays. However, the high inclination of the system means that this emission is obscured by the disk.[17][19] Most of the X-ray emission from OY Car appear to come from the polar regions.[20] This suggests the accretion is magnetically directed onto the pole of an inclined dipolar field.[21]
Greenhill et al. (2009) would invoke the presence of a third object to explain orbital period variations with an apparent periodicity of roughly 35 years. The third body could yield a minimum mass 7 times greater thanJupiter and be located 9.5astronomical units away from thecataclysmic variable system,[22] being likely either a massive planetary object or else a very low-massbrown dwarf.
It is likely that the apparent change is due tosolar cycle type magnetic activity in the secondary star. Large irregular deviations from the general trend, with time-scales of years, also occur. Further observations will be able to confirm or disprove the presence of asubstellar companion.
Diagram of the probable structure of the OY Carinae Star System.
^Khruzina, T. S.; et al. (March 2003). "Interpretation of Light Curves of the Cataclysmic Variable OY Car in a Model with Shockless Interaction between a Gaseous Stream and the Disk".Astronomy Reports.47 (3):214–231.Bibcode:2003ARep...47..214K.doi:10.1134/1.1562216.S2CID119896879.
^Duflot, M.; et al. (1995). "Vitesses radiales. Catalogue WEB: Wilson Evans Batten (Radial velocities: The Wilson-Evans-Batten catalogue)".Astronomy and Astrophysics Supplement Series.114: 269.Bibcode:1995A&AS..114..269D.
^abVogt, N.; et al. (February 1981). "The eclipsing dwarf nova OY CAR : ephemeris and physical parameters".Astronomy and Astrophysics.94:L29–L32.Bibcode:1981A&A....94L..29V.
^abMauche, C. W.; Raymond, J. C. (2000). Arthur, Jane; Brickhouse, Nancy; Franco, José (eds.).The EUV Emission-Line spectrum of OY Carinae in superoutburst: scattering in the wind. Astrophysical Plasmas: Codes, Models, and Observations, Proceedings of the conference held in Mexico City, October 25-29, 1999.Revista Mexicana de Astronomía y Astrofísica, Serie de Conferencias. Revista Mexicana de Astronomía y Astrofísica (Serie de Conferencias). Vol. 9. pp. 232–233.Bibcode:2000RMxAC...9..232M.
^abcHessman, F. V.; et al. (April 1989). "Time-resolved spectroscopy of the eclipsing dwarf nova OY Carinae".Astronomy and Astrophysics.213:167–175.Bibcode:1989A&A...213..167H.
^Vogt, N.; Schoembs, R.; Krzeminski, W.; Pedersen, H (February 1981). "The eclipsing dwarf nova OY CAR : ephemeris and physical parameters".Astronomy and Astrophysics.94:L29–L32.Bibcode:1981A&A....94L..29V.
^Vogt, N. (August 1980). "The SU UMa stars, an important sub-group of dwarf novae".Astronomy and Astrophysics.88:66–76.Bibcode:1980A&A....88...66V.
^Vogt, N. (June 1979). "Discovery of a new eclipsing dwarf nova: OY Carinae".The Messenger.17:39–40.Bibcode:1979Msngr..17...39V.
^Wlodarczyk, K. (January 1989). "The accretion disc in OY CAR during rise to outburst".Communications of the Konkoly Observatory.10 (93): 235.Bibcode:1989CoKon..93..235W.
^Bateson, F. M.; et al. (1991). "The superoutbursts cycle of OY Carinae".Royal Astronomical Society of New Zealand - Publications of Variable Star Section.17:83–84.Bibcode:1991PVSS...17...83B.
^Cheng, F. H.; et al. (October 2000). "Temporal Variations of the White Dwarf and Disk in OY Carinae Following the 1992 Superoutburst".The Astrophysical Journal.542 (2):1064–1070.Bibcode:2000ApJ...542.1064C.doi:10.1086/317012.
Nicholson, M. (June 2009). "Eclipses of OY Carinae in outburst".The Journal of the American Association of Variable Star Observers.37 (1): 40.Bibcode:2009JAVSO..37...40N.
Smak, J. (March 2008). "The hot spot in OY Car during its superoutburst".Acta Astronomica.58:65–67.Bibcode:2008AcA....58...65S.
Khruzina, T. S.; et al. (March 2003). "Interpretation of Light Curves of the Cataclysmic Variable OY Car in a Model with Shockless Interaction between a Gaseous Stream and the Disk".Astronomy Reports.47 (3):214–231.Bibcode:2003ARep...47..214K.doi:10.1134/1.1562216.
Wheatley, P. J.; West, R. G. (January 2002). Gänsicke, B. T.; Beuermann, K.; Reinsch, K. (eds.).Further analysis of the X-ray eclipse of OY Car measured with XMM-Newton. The Physics of Cataclysmic Variables and Related Objects. ASP Conference Proceedings. Vol. 261. San Francisco: Astronomical Society of the Pacific. p. 433.Bibcode:2002ASPC..261..433W.ISBN1-58381-101-X.
Mauche, Christopher W.; Raymond, John C. (October 2000). "Extreme Ultraviolet Explorer Observations of OY Carinae in Superoutburst".The Astrophysical Journal.541 (2):924–936.Bibcode:2000ApJ...541..924M.doi:10.1086/309489.
Mauche, C. W.; Raymond, J. C. (May 2000). Arthur, Jane; Brickhouse, Nancy; Franco, José (eds.).The EUV Emission-Line Spectrum of OY Carinae in Superoutburst: Scattering in the Wind. Astrophysical Plasmas: Codes, Models, and Observations, Proceedings of the conference held in Mexico City, October 25-29, 1999. Revista Mexicana de Astronomía y Astrofísica (Serie de Conferencias). Vol. 9. pp. 232–233.Bibcode:2000RMxAC...9..232M.
Djurašević, Gojko (September 1996). "A model of light-curve synthesizing for dwarf novae and the analysis of the OY CAR observations by application of the inverse-problem method".Astrophysics and Space Science.240 (2):317–329.Bibcode:1996Ap&SS.240..317D.doi:10.1007/BF00639595.
Harlaftis, E. T.; Marsh, T. R. (April 1996). "OY Carinae in outburst: Balmer emission from the red star and the gas stream".Astronomy and Astrophysics.308:97–106.arXiv:astro-ph/9510025.Bibcode:1996A&A...308...97H.
Bruch, A.; et al. (February 1996). "Multicolor photometry and eclipse mapping of OY Carinae in a superoutburst".Astronomy and Astrophysics.306: 151.Bibcode:1996A&A...306..151B.
Horne, Keith; et al. (May 1994). "HST eclipse mapping of dwarf nova OY Carinae in quiescence: an 'Fe II curtain' with Mach 6 velocity dispersion veils the white dwarf".Astrophysical Journal.426: 294.Bibcode:1994ApJ...426..294H.doi:10.1086/174064.
Cheng, F. H.; et al. (January 1994). Holt, Steve; Day, Charles S. (eds.).The cooling of the white dwarf in OY CAR after 1992 superoutburst. The Evolution of X-ray Binaries, Proceedings of a conference held in College Park, MD, 1993. AIP Conference Proceedings. Vol. 308. New York: American Institute of Physics Press. p. 197.Bibcode:1994AIPC..308..197C.doi:10.1063/1.46008.
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Wood, Janet H. (March 1990). "Can the quiescent accretion discs in the dwarf novae OY CAR and Z Chabe in a steady state ?".Monthly Notices of the Royal Astronomical Society.243:219–230.Bibcode:1990MNRAS.243..219W.
Wood, Janet H.; et al. (June 1989). "Eclipse Studies of the Dwarf Nova OY Carinae in Quiescence".Astrophysical Journal.341: 974.Bibcode:1989ApJ...341..974W.doi:10.1086/167557.
Schoembs, R.; et al. (July 1987). "Simultaneous multicolour photometry of OY Carinae during quiescence".Astronomy and Astrophysics.181:50–56.Bibcode:1987A&A...181...50S.
Naylor, T.; et al. (February 1987). "The May 1985 super outburst of OY-Carinae - Part One - Structure of the outer disk from optical and infrared observations".Astrophysics and Space Science.130 (1–2):365–369.Bibcode:1987Ap&SS.130..365N.doi:10.1007/BF00655018.
Ritter, H. (May 1980). "The physical parameters of the dwarf nova OY Car".Astronomy and Astrophysics.85:362–364.Bibcode:1980A&A....85..362R.
