ASASSN-25bz: new SU UMa-type dwarf nova
ASASSN-25bz (=AT 2025lkr) was discovered at 14.8 mag on 20 May by ASAS-SN.
The suggested outburst amplitude is ~8 mag according to the VSX. ASAS-SN
reported to the TNS that this could be a classical nova based on its low
Galactic latitude b~-2.0 deg.
https://www.aavso.org/vsx/index.php?view=detail.top&oid=10848672
I obtained the time-resolved observations of ASASSN-25bz with the
SAAO/Lesedi telescope on 26 and 27 May. Its light curve shows a prominent
ordinary superhump with an amplitude of 0.15 mag and a period of ~0.0561(1)
d (1-d aliases are possible). The optical spectrum obtained on 23 May with
the SAAO/Lesedi telescope is dominated by Balmer absorption lines.
Thus, I conclude that ASASSN-25bz is a new SU UMa-type dwarf nova. The
system is around 15.6 mag.
Best regards,
Yusuke
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South African Astronomical Observatory, Postdoc fellow
Yusuke TAMPO / 反保 雄介
EMAIL: tampo(a)kusastro.kyoto-u.ac.jp
ALT. EMAIL: yusuke(a)saao.ac.za
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TCP J18513997+3522412: large-amplitude modulation, possibly eclipsing WZ
Sge-type dwarf nova?
TCP J18513997+3522412 was discovered by Y. Nakamura on 22nd May at 13.7 mag
(unfiltered). The counterpart star in Pan-STARRS1 is r~20.5 mag, and thus
the outburst amplitude is 6.8 mag.
http://www.cbat.eps.harvard.edu/unconf/followups/J18513997+3522412.htmlhttps://www.aavso.org/vsx/index.php?view=detail.top&oid=10848644
Sano-san reported the time-resolved observations of this object. Although
the baseline was just one hour, the light curve shows a large-amplitude
modulation of ~0.35 mag. This is likely either an ordinary superhump in a
SU UMa-type dwarf nova or even a large-amplitude early superhump + eclipse
in an eclipsing WZ Sge-type dwarf nova.
Further time-resolved observations with longer baselines are encouraged.
Best regards,
Yusuke
--
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South African Astronomical Observatory, Postdoc fellow
反保 雄介 Yusuke TAMPO
MAIL: tampo(a)kusastro.kyoto-u.ac.jp
MAIL: yusuke(a)saao.ac.za
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TCP J02472889+6758170 = Gaia DR3 517539710877791488
The NMW team discovered this transient at 13.0 mag (unfiltered), which is
associated with the known variable star Gaia DR3 517539710877791488 with
~18.0 mag. They suggest that this could be an AM CVn star in outburst. Its
blue color in the Pan-STARRS1 image also supports this suggestion, and TCP
J02472889+6758170 is at least a CV in new outburst.
http://www.cbat.eps.harvard.edu/unconf/followups/J02472889+6758170.htmlhttps://www.aavso.org/vsx/index.php?view=detail.top&oid=2841325
Time-resoved observations are encouraged.
Best regards,
Yusuke
--
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South African Astronomical Observatory, Postdoc fellow
反保 雄介 Yusuke TAMPO
MAIL: tampo(a)kusastro.kyoto-u.ac.jp
MAIL: yusuke(a)saao.ac.za
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ASASSN-25bu: new SU UMa-type dwarf nova
ASASSN-25b was discovered by ASAS-SN on 2025-05-12.06. The outburst
amplitude is ~8.3 mag according to the VSX. This object is currently ~17.5
mag.
https://www.aavso.org/vsx/index.php?view=detail.top&oid=10848624
Josch Hambsch and the SAAO team have reported the time-seeries observations
of ASASSN-25bu. Lesedi/Mookodi observations on 22 May showed probable
superhumps with a period of ~0.0574 d and an amplitude of ~0.15 mag.
Thus ASASSN-25bu is a new SU UMa-type dwarf nova. Considering its short
superhump period, large outburst amplitude, and no previous outbursts,
ASASSN-25bu might be a WZ Sge-type.
Best regards,
Yusuke
--
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South African Astronomical Observatory, Postdoc fellow
反保 雄介 Yusuke TAMPO
MAIL: tampo(a)kusastro.kyoto-u.ac.jp
MAIL: yusuke(a)saao.ac.za
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ZTF18acynctq = TCP J20402089+4915562 = ASASSN-25bt: new SU UMa star
candidate
XOSS team via TOCP/TNS and ASAS-SN reported the 2025 outburst of this
system, which is already known as ZTF18acynctq in its 2018 outburst.
https://alerce.online/object/ZTF18acynctqhttp://www.cbat.eps.harvard.edu/unconf/followups/J20402089+4915562.htmlhttps://www.aavso.org/vsx/index.php?view=detail.top&oid=10848612
Its 2018 outburst lasted for ~15 days and showed a possible
rebrightening in the ATLAS data. Thus the outburst cycle is ~2300 d.
This system is currently ~16.0 mag, and time-resolved observations may
detect superhumps.
Best regards,
Yusuke
--
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South African Astronomical Observatory, Postdoc fellow
反保 雄介 Yusuke TAMPO
MAIL: tampo(a)kusastro.kyoto-u.ac.jp
MAIL: yusuke(a)saao.ac.za
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