Light curves for DO Draconis. The upper plot, adapted from Andronovet al.,[1] shows the long-term variability and eruptive behaviour. The lower plot, adapted from Hillet al.,[2] shows theellipsoidal variability assuming a period of 3.96898 hours.
The variable YY Draconis was identified by W. Tsesevich in 1934 and determined to be anAlgol type binary that ranged in brightness from apparent magnitude 12.9 to under 14.5 with a period of 4.21123 days. However, subsequent scans ofphotographic plates at the same coordinates have failed to identify any such variation. Hence, a positional reporting error is suspected,[11] and no further observations of this variable were reported (as of 1983).[12]
In 1982, theX-ray emission source PG 1148+719 (3A 1148+719) was associated with a star displaying the spectrum of a U Geminorum variable byR. F. Green and associates. In their paper, they identified this star as YY Dra, based on a positional search of theGeneral Catalogue of Variable Stars.[13] The following year,W. Wenzel found the association with YY Dra appeared erroneous but discovered a nearby eruptive variable that brightened to magnitude 10.6 then dimmed to below magnitude 14.5. He estimated a lengthy cycle time of 5 to 20 years, comparable toBZ Ursae Majoris.[12] This cataclysmic variable was cataloged as DO Draconis.
An outburst of DO Dra was observed while in progress in 1985, which brought the system to about a magnitude brighter than minimum.[14][15] In 1987, a debate arose as to whether this is the same variable as YY Dra, as the coordinates are separated by only53″.[11][16] Discussion of this identity conflict has continued as recently as 2022, and, historically, both identifiers have been used to discuss the same cataclysmic variable. A full resolution of this conflict may prove impossible since many of the original photographic plates were destroyed duringWorld War II. The continued use of DO Dra for this variable has been encouraged since it is an unambiguous identifier.[17]
In 1991,M. Mateo and associates found anorbital period of 3.96 h with asemimajor axis of1.35±0.15 R☉ for this binary system. DO Dra consists of a compactwhite dwarf primary being orbited by ared dwarf stellar companion. The red dwarf has filled itsRoche lobe and is losing mass, which is being accreted by the white dwarf. Because of the close orbit, the red dwarf is rotating rapidly and is expected to bemagnetically active. However, the majority of theionized calcium emission lines originate from irradiation of the red dwarf by soft X-rays coming from the primary.[7]
This system was identified as aDQ Herculis variable byJ. Patterson and associates in 1994 – also known as an intermediate polar. This indicates the white dwarf has a sufficiently strong magnetic field to channel the flow of gas from an orbitingaccretion disk onto itsmagnetic poles. Theshock from this accretion is producing the X-ray flux.[18] A 1997 study based on observations with theHubble Space Telescope found a rotation period of529.31±0.02 s for the white dwarf. This spin rate is producing coherent pulsations that are detectable in both the visual and X-ray spectrum.[9] The magnetic poles reacheffective temperatures of 220,000 K in the accretion region, compared to 21,500 K for the remainder of the white dwarf surface.[8]
^Hill, Katherine L.; Littlefield, Colin; Garnavich, Peter; Scaringi, Simone; Szkody, Paula; Mason, Paul A.; Kennedy, Mark R.; Shaw, Aarran W.; Covington, Ava E. (June 2022), "Hitting a New Low: The Unique 28 hr Cessation of Accretion in the TESS Light Curve of YY Dra (DO Dra)",The Astronomical Journal,163 (6): 246,arXiv:2203.00221,Bibcode:2022AJ....163..246H,doi:10.3847/1538-3881/ac5a51,S2CID247187776
^Joshi, Vishal (2013), Khare, Pushpa; Ishwara-Chandra, C. H. (eds.), "Near-infrared photometric study of intermediate polar YY Draconis",31st ASI Meeting, ASI Conference Series, vol. 9, p. 80,Bibcode:2013ASInC...9...80J.
^abcdMateo, Mario; et al. (March 1991), "Near-Infrared Time-resolved Spectroscopy of the Cataclysmic Variable YY Draconis",Astrophysical Journal,370: 370,Bibcode:1991ApJ...370..370M,doi:10.1086/169823.
^abHoard, D. W.; Linnell, A. P.; Szkody, Paula; Sion, Edward M. (July 2005), "Spin-resolved Far-Ultraviolet Observations of the Magnetic White Dwarf in YY Draconis",The Astronomical Journal,130 (1):214–223,Bibcode:2005AJ....130..214H,doi:10.1086/430749,S2CID121358198.
^abHaswell, Carole A.; et al. (February 1997), "Pulsations and Accretion Geometry in YY Draconis: A Study Based on Hubble Space Telescope Observations",The Astrophysical Journal,476 (2):847–864,Bibcode:1997ApJ...476..847H,doi:10.1086/303630,S2CID121217299.
^abPatterson, J.; Eisenman, N. (August 1987), "Let's Forget DO Dra",Information Bulletin on Variable Stars,3079: 1,Bibcode:1987IBVS.3079....1P.
^abWenzel, W. (January 1983), "The X-Ray Source 3A1148+719 is another Dwarf Nova with Very Long Cycle Length",Information Bulletin on Variable Stars,2262: 1,Bibcode:1983IBVS.2262....1W.
^McNaught, R. H.; et al. (November 1985), Green, D. W. E. (ed.), "DO Draconis",IAU Circular (4143): 2,Bibcode:1985IAUC.4143....2M.
^Hurst, G. M.; et al. (November 1985), Marsden, B. G. (ed.), "DO Draconis",IAU Circular (4130): 1,Bibcode:1985IAUC.4130....1H.
^Kholopov, P. N.; Samus, N. N. (March 1988), "Should we Really Forget DO Dra?",Information Bulletin on Variable Stars,3154: 1,Bibcode:1988IBVS.3154....1K.
^Kato, Taichi; Pavlenko, Elena P. (March 2022), "On the identity of Tsesevich's "YY Dra"",arXiv:2203.05091 [astro-ph.SR]
^Patterson, J.; et al. (June 1992), "Rapid Oscillations in Cataclysmic Variables. VIII. YY Draconis (=3A 1148+719)",Astrophysical Journal,392: 233,Bibcode:1992ApJ...392..233P,doi:10.1086/171421.
Andronov, Ivan L.; et al. (February 2019), "DO Dra: Transient Periodic Oscillations at the Suboutburst state of the Magnetic Dwarf Nova",The Astronomer's Telegram,12527: 1,Bibcode:2019ATel12527....1A.
Andronov, Ivan L.; et al. (November 2017), "DO Dra:Recovering to the Base Intermediate Luminosity State",The Astronomer's Telegram,10982: 1,Bibcode:2017ATel10982....1A.
Breus, Vitalii V.; et al. (June 2017), "Rare Low State of DO Dra, the Magnetic Dwarf Nova=Outbursting Intermediate Polar",The Astronomer's Telegram,10477 (10477): 1,Bibcode:2017ATel10477....1B.
Virnina, Natalia A. (February 2011), ""Tsessevich" Project: an Attempt to Find the System YY Dra. I",Open European Journal on Variable Stars,133: 1,arXiv:1102.1271,Bibcode:2011OEJV..133....1V.
Boyd, David (February 2005), "Detection and measurement in the V-band of the white dwarf spin period in the January 2004 outburst of DO (YY) Draconis",Journal of the British Astronomical Association,115 (1):25–28,arXiv:astro-ph/0409349,Bibcode:2005JBAA..115...25B.
Szkody, P.; et al. (December 2004), Vrielmann, Sonja; Cropper, Mark (eds.), "FUSE Result on Magnetic CVs: VV Pup, YY Dra, LS Peg and DW UMa",Magnetic Cataclysmic Variables, IAU Colloquium 190, Proceedings of the Conference held 8-13 December, 2002 in Cape Town, South Africa, ASP Conference Proceedings, vol. 315, San Francisco: Astronomical Society of the Pacific, p. 184,Bibcode:2004ASPC..315..184S.
Yazgan, E.; Balman, Ş. (January 2002), Gänsicke, B. T.; Beuermann, K.; Reinsch, K. (eds.), "Analysis of the ASCA data of the intermediate polar YY Dra",The Physics of Cataclysmic Variables and Related Objects, ASP Conference Proceedings,261, San Francisco: Astronomical Society of the Pacific: 177,Bibcode:2002ASPC..261..177Y.
Šimon, V. (August 2000), "Outburst activity of the intermediate polar DO Draconis (3A 1148+719)",Astronomy and Astrophysics,360:627–632,Bibcode:2000A&A...360..627S.
Norton, A. J.; et al. (July 1999), "YY Draconis and V709 Cassiopeiae: two intermediate polars with weak magnetic fields",Astronomy and Astrophysics,347:203–211,arXiv:astro-ph/9811310,Bibcode:1999A&A...347..203N.
Mattei, Janet A. (October 1996), "Rare Bright Outburst of 1137+72 DO Draconis (= YY Draconis)",AAVSO Alert Notice 231, vol. 231, p. 1,Bibcode:1996AAN...231....1M.
Reinsch, K.; et al. (1995), Buckley, D. A. H.; Warner, B. (eds.), "ROSAT Observations of Intermediate Polars: AE AQR and YY DRA",Cape Workshop on Magnetic cataclysmic variables, Proceedings of the Cape Workshop, held in Cape Town, 23-27 January 1995, Astronomical Society of the Pacific Conference Series, vol. 85, San Francisco: Astronomical Society of the Pacific (ASP), p. 115,Bibcode:1995ASPC...85..115R.
Szkody, P.; et al. (1994), Shafter, Allen W. (ed.), "ROSAT Observations of the Suspected DQ Her Systems YY Draconis, AH Eridani and S193",Interacting binary stars : a symposium held in conjunction with the 105th Meeting of the Astronomical Society of the Pacific, San Diego State University, 13-15 July 1993, vol. 56, San Francisco, CA: Astronomical Society of the Pacific, p. 350,Bibcode:1994ASPC...56..350S.
Patterson, Joseph; Szkody, Paula (October 1993), "Rapid Oscillations in Cataclysmic Variables. XI. X-Ray Pulses in YY Draconis",Publications of the Astronomical Society of the Pacific,105: 1116,Bibcode:1993PASP..105.1116P,doi:10.1086/133289,S2CID119767669.
