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October 2025

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[vsnet-campaign-dn 17550] TCP J20522886+1637203: a likely new WZ Sge-type dwarf nova
by tonny.vanmunster＠gmail.com 19 Oct '25

19 Oct '25

Dear colleagues, TCP J20522886+1637203 was discovered by XOSS (Xingming Observatory Sky Survey) on 2025 Oct 08.6 at mag 12.73 CV. The quiescent counterpart is a 22.1 r mag object, implying an outburst amplitude of ~9 mag. I have been observing this object on a very regular basis since Oct 08th with no periodic modulations visible in the light curves - until last night (Oct 17/18). I have just completed the analysis of my unfiltered CCD observations of TCP J20522886+1637203, obtained on 2025 Oct 17/18 at CBA Extremadura Observatory. The data were acquired under clear skies with a 0.40-m f/5.1 telescope and a Moravian G2-4000 CCD. The light curve now shows clear ordinary superhumps with an amplitude of 0.20 mag. Given their late onset (9 dyas after detection) and the large outburst amplitude, we conclude that TCP J20522886+1637203 is a new WZ Sge-type dwarf nova. A period analysis, using ANOVA, Lomb-Scargle, Generalized-Lomb-Scargle and PDM methods (Peranso 3.1) yields a combined superhump period of 0.0567 +/- 0.0004d. The object was measured at mag CV = 15.0 on Oct 18th. Image calibration and photometry were performed with the latest release of Phoranso, which enabled simultaneous photometry of several additional variable stars within the same frames. Continued monitoring is strongly encouraged to study the superhump profile and evolution. I will submit my observations to AAVSO, CBA and VSNET for further analysis. With kind regards, Tonny --- Tonny Vanmunster CBA Belgium Observatory CBA Extremadura Observatory http://www.cbabelgium.co <http://www.cbabelgium.com/> m PERANSO : The Light Curve and Period Analysis Software http://www.peranso.co <http://www.peranso.com/> m PHORANSO: Photometric Reduction and Analysis Software http://www.phoranso.com <http://www.phoranso.com/>

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