[vsnet-alert 23650] ASASSN-19xw is a new SU UMa (or WZ Sge)-type dwarf nova

Thu Oct 24 08:00:24 JST 2019

Dear colleagues,

I have concluded the analysis of my 2019, Oct 17/18, 18/19 and 20/21 unfiltered CCD photometry sessions of ASASSN-19xw. Observations were made at CBA Belgium and CBA Extremadura Observatories, using a 0.40-m telescope, under clear skies. 

Until 2019, Oct 13th, the object declined smoothly in the manner of a classical nova with no significant modulations (see Lloyd and Vanmunster, 2019, ATel #13180). My new time-series data of the afore mentioned three nights now show that the slow decline has ceased and from about 2019, Oct 16th the star has been at a mean magnitude of g ~ 16.8. The lightcurve furthermore shows the presence of superhumps with an amplitude of 0.28 mag. A period analysis using the ANOVA, Lomb-Scargle and PDM methods (Peranso),  yields a combined superhump period of 0.057 +/- 0.002d.  

The outburst amplitude of the system is at least 8 magnitudes (ATel #13180) and a recent spectrum shows that ASASSN-19xw is not a nova but a dwarf nova in outburst ( <https://wis-tns.weizmann.ac.il/object/2019rki/classification-cert> Kawash,   <https://wis-tns.weizmann.ac.il/object/2019rki/classification-cert> https://wis-tns.weizmann.ac.il/object/2019rki/classification-cert). Hence, the object can now be confirmed as a new large-amplitude SU UMa (or WZ Sge)-type system.

Observations will be sent to AAVSO, CBA and VSNET for further analysis. 

Follow-up observations are highly recommended to check for possible rebrightenings. 

Best regards
Tonny

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Tonny Vanmunster
CBA Belgium Observatory
CBA Extremadura Observatory
www.cbabelgium.com <http://www.cbabelgium.com> 
www.peranso.com <http://www.peranso.com> 