TCP J18030904+1218140: rapid decline from the outburst and rebrightenings expected The latest observations from the SAAO Lesedi telescope, Moriyama-san, Itoh-san, and Funada-san, show the rapid decline from the outburst on 1 September. The current magnitude is around 18.5. Since AM CVn stars often show rebrightening outbursts following the main outburst, continuous snapshots are still encouraged to catch the rebrightening events. Best regards, Yusuke 2026年8月31日(月) 9:27 Yusuke Tampo <tampo@kusastro.kyoto-u.ac.jp>:
TCP J18030904+1218140 is now confirmed to be a new AM CVn star: appearance of an ordinary superhump and its period
As expected from the previous alert, the latest time-resolved observations of this object after 28 August by the Lesedi telescope, Pavol A. Dubovsky, Josch Hambsch, and Sjoerd Dufoer show ordinary superhumps with a single-peaked profile. Its tentative period is determined to be 0.02913(2) d (~41.9 min) via PDM, although some aliases are still possible. This periodicity confirms that TCP J18030904+1218140 is a new AM CVn star in outburst. Hence, the reported double-peaked modulation on 20 August is likely the early superhumps (or some kind of orbital modulation), and its reported period (0.0288 d = 41.5 min) seems correct.
The target is currently g~16.2 mag during the Lesedi observations last night. Continuous time-resolved observations are still strongly encouraged to study the superhump period evolution.
Best regards, Yusuke
2026年8月28日(金) 11:14 Yusuke Tampo <tampo@kusastro.kyoto-u.ac.jp>:
TCP J18030904+1218140: brightening from the dip, probably the second superoutburst
The Lesedi telescope observations on 26 August show that the system is now brightening after the dip. The latest observation in ZTF is g=15.9 on 28 August. https://alerce.online/object/ZTF18absdcuk
Ordinary superhumps are expected to appear at this phase. Time-resolved observations are strongly encouraged.
Best regards, Yusuke
2026年8月24日(月) 13:27 Yusuke Tampo <tampo@kusastro.kyoto-u.ac.jp>:
TCP J18030904+1218140: entering the dip
Sano-san, Itoh-san, Pavol A. Dubovsky, and the SAAO Lesedi telescope have reported the time-resolved observations, as well as snapshot observations by Funada-san and Moriyama-san. The latest observations on 2028-08-23 by Itoh-san and the Lesedi telescope show that this system is currently entering the dip around 17.5 mag.
Given its large outburst amplitude, it is expected that the system will be back in outburst soon, most likely with ordinary superhumps, regardless of whether it is an AM CVn star or a normal hydrogen-rich CV. Continuous monitoring is highly encouraged to catch the next brightening.
Best regards, Yusuke
2026年8月21日(金) 11:36 Yusuke Tampo <tampo@kusastro.kyoto-u.ac.jp>:
TCP J18030904+1218140= ZTF18absdcuk: large-amplitude CV outburst, possibly AM CVn-type?
TCP J18030904+1218140 was discovered by Yuji Nakamura on 2026-08-19.5199 UT at 14.9 mag. Its previous outburst and log decline in 2018 were detected as ZTF18absdcuk. The VSX lists the r=21.1 mag star as the quiescent counterpart; thus the outburst amplitude is ~6 mag. https://alerce.online/object/ZTF18absdcuk https://vsx.aavso.org/index.php?view=detail.top&oid=10875986
Sano-san has reported the time-resolved observations for ~1.5 hours on 2026-08-20 UT. The light curve shows possible modulations with a period of 0.0288 d (41.5 min) with a double-peaked profile (early superhumps?).
The optical spectrum obtained by the SAAO Lesedi telescope on 2026-08-19 UT shows a blue continuum with no prominent emission or absorption lines.
Time-resolved photometry is strongly encouraged to confirm the periodicity and determine whether this is an AM CVn star or not.
Best regards, Yusuke
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Yusuke TAMPO / 反保 雄介 Postdoc fellow South African Astronomical Observatory / University of Cape Town EMAIL: tampo@kusastro.kyoto-u.ac.jp ALT. EMAIL: yusuke@saao.ac.za
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Yusuke TAMPO / 反保 雄介 Postdoc fellow South African Astronomical Observatory / University of Cape Town EMAIL: tampo@kusastro.kyoto-u.ac.jp ALT. EMAIL: yusuke@saao.ac.za
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Yusuke TAMPO / 反保 雄介 Postdoc fellow South African Astronomical Observatory / University of Cape Town EMAIL: tampo@kusastro.kyoto-u.ac.jp ALT. EMAIL: yusuke@saao.ac.za
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Yusuke TAMPO / 反保 雄介 Postdoc fellow South African Astronomical Observatory / University of Cape Town EMAIL: tampo@kusastro.kyoto-u.ac.jp ALT. EMAIL: yusuke@saao.ac.za
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-- ---------------------------------------------- Yusuke TAMPO / 反保 雄介 Postdoc fellow South African Astronomical Observatory / University of Cape Town EMAIL: tampo@kusastro.kyoto-u.ac.jp ALT. EMAIL: yusuke@saao.ac.za ----------------------------------------------