[vsnet-alert 25704] ASASSN-21er: new WZ Sge-type dwarf nova

tonny.vanmunster@gmail.com via vsnet-alert vsnet-alert at ooruri.kusastro.kyoto-u.ac.jp
Sun Apr 11 04:29:32 JST 2021

Dear colleagues,

I have collected unfiltered CCD observations of ASASSN-21er on 7 nights
between 2021, Apr 02nd and Apr 09th. All observations were made at CBA
Extremadura Observatory, using a 0.40-m f/5.1 telescope and SX-46 CCD
camera, mostly under clear skies. 

The object faded from mag 13.9 (CV) on Apr 02nd to mag 14.9 (CV) on Apr
09th, without a clear sign of (early or regular) superhumps in the light
curve, except for last nights (Apr 09/10) session. That session clearly
shows the presence of regular superhumps with an amplitude of 0.17 mag. A
period analysis using the ANOVA, Lomb-Scargle, Generalized-Lomb-Scargle and
PDM methods (Peranso 3.0), yields a combined superhump period of 0.0565 +/-

The superhump profile shows no signs of a double-waved pattern, and I could
not detect early superhumps in my data. Yet, the large outburst amplitude of
~9 mag, and the long time for superhumps to develop (approx. 9 days) make
this a very likely WZ Sge-type dwarf nova. Follow-up observations are
recommended to further track the evolution of the superhumps.

I will send my observations to AAVSO, CBA and VSNET for further analysis.

Best regards

Tonny Vanmunster
CBA Belgium Observatory
CBA Extremadura Observatory

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