December 2025 - vsnet-campaign-dn - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-campaign-dn 17562] TCP J16425922+2621020: a large amplitude CV candidate, likely a WZ Sge-type dwarf nova
by Yusuke Tampo 27 Dec '25

27 Dec '25

TCP J16425922+2621020: a large amplitude CV candidate, likely a WZ Sge-type dwarf nova Tadashi Kojima reported the discovery of TCP J16425922+2621020 on 2025 12 26.8538 UTC at 13.0 mag (unfiltered). http://www.cbat.eps.harvard.edu/unconf/followups/J16425922+2621020.html The likely counterpart is 3"-away Gaia DR3 1301247792154799488, G=20.044(8) mag at 674 (-144/+248) pc. Thus, the absolute magnitudes in quiescence and outburst are ~10.9(7) and ~3.9(7) mag, respectively. This is also recorded in the Gaia white dwarf candidate catalogs (e.g., Gentile et al. 2021). http://vizier.cds.unistra.fr/viz-bin/VizieR?-source=&-out.add=_r&-out.add=_… Given its large outburst amplitude of ~7 mag, no previous outbursts, and possible white dwarf-dominated spectral energy distribution in quiescence, TCP J16425922+2621020 is most likely a WZ Sge-type dwarf nova in outburst. Although time-resolved observations are almost impossible for now due to its RA=16hr, this might be a nice target for future observations. Best regards, Yusuke -- ---------------------------------------------- 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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[vsnet-campaign-dn 17561] ASASSN-22nd (=AT2025ahnc= ZTF25acibbkf =ASASSN-25fb); a new fast-decaying outburst
by Yusuke Tampo 19 Dec '25

19 Dec '25

ASASSN-22nd (=AT2025ahnc= ZTF25acibbkf =ASASSN-25fb); a new fast-decaying outburst GOTO, ZTF, and ASASSN have detected a new outburst from a known CV candidate ASASSN-22nd. https://vsx.aavso.org/index.php?view=detail.top&oid=2345330 https://www.wis-tns.org/object/2025ahnc https://lasair-ztf.lsst.ac.uk/objects/ZTF25acibbkf/ https://asas-sn.osu.edu/sky-patrol/coordinate/19517db9-fb36-4d9c-a94d-2ca87… This outburst shows a fast decay, approximately 1 mag/d. Considering its large amplitude(>7mag), relatively short outburst cycle (~3 years), and fast decay of the outburst, this outburst could be a precursor outburst of a dwarf nova superoutburst, or even from an AM CVn star. Although the system is currently faint (~18.5 mag in ATLAS), if the system returns to a bright state, time-resolved photometries will be encouraged. Best regards, Yusuke -- ---------------------------------------------- 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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[vsnet-campaign-dn 17557] ASASSN-25eq: new WZ Sge-type dwarf nova, likely a period bouncer
by Yusuke Tampo 17 Dec '25

17 Dec '25

ASASSN-25eq: new WZ Sge-type dwarf nova, likely a period bouncer ASASSN discovered ASASSN-25eq on 2025-11-13.18 UT at 15.07 mag. Then it brightened to g=14.0 mag on 2025-11-15. The VSX lists g=21.9 mag as the counterpart, hence the outburst amplitude is ~8 mag. https://vsx.aavso.org/index.php?view=detail.top&oid=10868208 https://asas-sn.osu.edu/sky-patrol/coordinate/579ca10e-176d-4c3b-958f-03a39… Josch Hambsh and Berto Monard have reported the time-resolved observations of ASASSN-25eq. The light curve shows a 1-mag dip around 2025-11-25 UT. After this dip, clear superhumps are present, with a period of ~0.0645 d. There is no clear modulation before the dip. Thus, ASASSN-25eq is a new WZ Sge-type dwarf nova, with a double-superoutburst feature often observed in a period bouncer system. See e.g. https://ui.adsabs.harvard.edu/abs/2018PASJ...70...47K/abstract Given the absence of clear early superhumps, ASASSN-25eq is presumably a face-on system. A spectrum taken with the Mookodi/Lesedi telescope on 16 Nov. is dominated by Balmer absorption lines, which supports this interpretation. Time-resolved observations are encouraged. Best regards, Yusuke -- ---------------------------------------------- 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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[vsnet-campaign-dn 17559] TCP J07454958-2442056: most likely a WZ Sge-type dwarf nova
by Yusuke Tampo 15 Dec '25

15 Dec '25

TCP J07454958-2442056: most likely a WZ Sge-type dwarf nova TCP J07454958-2442056 was discovered by Yuji Nakamura on 13th Oct 2025 at 14.0 mag (unfiltered). According to VSX, the outburst amplitude is ~8.2 mag. https://vsx.aavso.org/index.php?view=detail.top&oid=10868099 Josch Hambsch and Sjoerd Dufoer have reported the time-resolved observations of this source. The light curve shows possible superhumps with a period of ~0.055 d, although I cannot conclude due to its faintness and 1-d aliases. Given its large outburst amplitude, almost 40-d outburst duration, and short superhump period, TCP J07454958-2442056 is most likely a new WZ Sge-type dwarf nova. Note that the system has already faded below the detection level of ATLAS. https://fallingstar-data.com/forcedphot/queue/3502597/ Best regards, Yusuke -- ---------------------------------------------- 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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[vsnet-campaign-dn 17558] ASASSN-25en: new SU UMa-type dwarf nova
by Yusuke Tampo 02 Dec '25

02 Dec '25

ASASSN-25en: new SU UMa-type dwarf nova ASASSN discovered ASASSN-25en on 2025-11-03 UT at 14.94 mag. The outburst amplitude in the VSX is ~7.5 mag. https://vsx.aavso.org/index.php?view=detail.top&oid=10868163 Josch Hambsch and Itoh-san have reported the time-resolved observations. The light curve after 2025-11-11 UT shows a single-peaked superhump with a period of either 0.06003(3) or 0.06390(3) d. Thus, ASASSN-25en is a new SU UMa-type dwarf nova. The rapid decline from the outburst was observed around 2025-11-21 UT. Best regards, Yusuke -- ---------------------------------------------- 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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