[vsnet-outburst 31609] ASASSN-25fj; new SU UMa-type dwarf nova, most likely WZ Sge subtype
ASASSN-25fj; new SU UMa-type dwarf nova, most likely WZ Sge type ASASSN reported the discovery of ASASSN-25fj on 2026-01-1.19 UT. The observed maximum was approximately at 12.2 mag on 2025-12-25.0 UT according to ASASSN. https://asas-sn.osu.edu/sky-patrol/coordinate/ec92b0f6-1377-450b-b464-7fbe3f... The likely counterpart is GALEX J050001.2-571430 (NUV=21.5(2) mag) and DES J050001.26-571430.1 (g=21.278(9) mag). Thus the outburst amplitude is ~9mag. Lesedi telescope at the SAAO and Josch Hambsch have reported the time-resolved observations of ASASSN-25fj. Its light curve after 2026-01-03 shows single-peaked ordinary superhumps with a period of ~0.0556 d and an amplitude of > 0.1 mag. Hence, ASASSN-25fj is a new SU UMa-type dwarf nova. Given its large outburst amplitude and short superhump period, it most likely belongs to the WZ Sge subtype. Continuous observations are encouraged. Best regards, Yusuke -- ---------------------------------------------- South African Astronomical Observatory, Postdoc fellow Yusuke TAMPO / 反保 雄介 EMAIL: tampo@kusastro.kyoto-u.ac.jp ALT. EMAIL: yusuke@saao.ac.za ----------------------------------------------
ASASSN-26ab = ASASSN-25fj; updated superhump period Lesedi telescope at the SAAO, Josch Hambsch, and Peter Starr reported further time-resolved observations of ASASSN-26ab = ASASSN-25fj. The ordinary superhump period is updated to 0.054915(8) d. The system is currently in the stage-B ordinary superhump phase. *Note that the ASASSN team somehow assigned a new name ASASSN-26ab. Best regards, Yusuke -- ---------------------------------------------- South African Astronomical Observatory, Postdoc fellow Yusuke TAMPO / 反保 雄介 EMAIL: tampo@kusastro.kyoto-u.ac.jp ALT. EMAIL: yusuke@saao.ac.za ----------------------------------------------
Dear Yusuke, I think TESS is currently observing this object, and it should detect the outburst. There are 41 sectors in the archive (observed between 2019 and 2025), but I haven't detected any outbursts in them. Sincerely, Alexander Tarasenkov чт, 8 янв. 2026 г. в 12:25, Yusuke Tampo <tampo@kusastro.kyoto-u.ac.jp>:
ASASSN-26ab = ASASSN-25fj; updated superhump period
Lesedi telescope at the SAAO, Josch Hambsch, and Peter Starr reported further time-resolved observations of ASASSN-26ab = ASASSN-25fj. The ordinary superhump period is updated to 0.054915(8) d. The system is currently in the stage-B ordinary superhump phase. *Note that the ASASSN team somehow assigned a new name ASASSN-26ab.
Best regards, Yusuke -- ----------------------------------------------
South African Astronomical Observatory, Postdoc fellow Yusuke TAMPO / 反保 雄介 EMAIL: tampo@kusastro.kyoto-u.ac.jp ALT. EMAIL: yusuke@saao.ac.za
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participants (2)
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Yusuke Tampo -
Александр Тарасенков