ASASSN-25df; new SU UMa-type dwarf nova

ASASSN-25df was discovered by ASAS-SN on 2025-07-28.02 UTC at g=13.51 mag. The outburst amplitude is ~8.0 mag. ATLAS has also detected this outburst since 2025-07-25.

Josch Hambsh reported the time-resolved observations.  The observations after 2025-08-02 show strong variations with an amplitude of ~0.1 mag. Due to the short baselines because of its RA~12.5 hr, the superhump period is not well constrained; a possible period is ~0.067 d, but other aliases are equally possible.

Thus, I conclude that ASASSN-25df is a new SU UMa-type dwarf nova. A waiting time of ~7 days before the appearance of ordinary superhumps suggests that ASASSN-25df can be a WZ Sge-type dwarf nova.

Best regards,

Yusuke