August 2025 - vsnet-alert - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-alert 28101] Spectroscopic and photometric confirmation of TCP J22135399+3015357 as a WZ Sge-type dwarf nova
by Keisuke Isogai 22 Aug '25

22 Aug '25

Spectroscopic and photometric confirmation of TCP J22135399+3015357 as a WZ Sge-type dwarf nova We posted the results of our spectroscopic and photometric observations to ATel: https://www.astronomerstelegram.org/?read=17347 We confirmed that this object is a new WZ Sge-type dwarf nova with a large outburst amplitude.

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[vsnet-alert 28100] TCP J22135399+3015357: a likely new WZ Sge-type dwarf nova
by Tonny Vanmunster 21 Aug '25

21 Aug '25

Dear colleagues, TCP J22135399+3015357 was discovered by the NMW survey at the Astroverty astrofarm in Russia on 2025 Aug 19.8 at mag 13.6 CR. Archival images show that the object was already in outburst one day earlier. The quiescent counterpart is listed at 22.8 r mag, implying an outburst amplitude of ~9 mag. I have just completed the analysis of my unfiltered CCD observations of TCP J22135399+3015357, obtained on 2025 Aug 20/21 at CBA Extremadura Observatory. The data were acquired under clear skies with a 0.40-m f/5.1 telescope and a Moravian G2-4000 CCD. The light curve reveals clear double-peaked modulations consistent with early superhumps, with an amplitude of 0.11 mag. A period analysis, using ANOVA, Lomb-Scargle, Generalized-Lomb-Scargle and PDM methods (Peranso 3.1) yields a combined superhump period of 0.0612 +/- 0.0012d. The object was measured at mag CV = 14.2 on Aug 20th. Image calibration and photometry were performed with the latest release of Phoranso. These findings strongly suggest that TCP J22135399+3015357 is a new WZ Sge-type dwarf nova. Continued monitoring is strongly encouraged to study the superhump profile and evolution. I will submit my observations to AAVSO, CBA and VSNET for further analysis. With kind regards, Tonny --- Tonny Vanmunster CBA Belgium Observatory CBA Extremadura Observatory http://www.cbabelgium.com PERANSO : The Light Curve and Period Analysis Software http://www.peranso.com PHORANSO: Photometric Reduction and Analysis Software http://www.phoranso.com

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[vsnet-alert 28099] AT 2025tzw (TCP J21092606+3548416) - unclear type dwarf nova in superoutburst
by t9005780498＠gmail.com 17 Aug '25

17 Aug '25

Dear colleagues, The new dwarf nova AT 2025tzw (TCP J21092606+3548416) is now in superoutburst. Optical transient (15.6 in clear band) was detected at 2025-08-15 12:34:33.600 UT by Yuji Nakamura et al. ASAS-SN photometric survey detects AT 2025tzw at 2025-08-15.236 UT with g magnitude 15.866, and detects no transient 2025-08-14.245 UT with limit 16.594. ZTF shows quiescent state magnitude of about 21.5 and three missed historical superoutbursts in September 2023, April 2021 and June 2018, peaking at 16.2-16.4m in zg, which allows us to assume supercycle duration of about 3 years and superoutbursts amplitude of about 5.1-5.3m. The absence of normal outbursts makes the object's status ambiguous between the classical SU UMa and WZ Sge subgroups. Dr. N. P. Ikonnikova and Dr. S. Yu. Shugarov report presence of superhumps with period ~0.075 days and amplitude about 0.24m based on observations with 60cm Ritchey–Chrétien telescope at 2025-08-16. This may indicate the absence of the early superhumps phase. Color indices are U-B = -0.6 B-V = 0.12 V-R = 0.04 R-I = 0.1. R. Ottaviani and P. Ochner report spectroscopic classification of AT 2025tzw as CV star with a blue continuum with Balmer absorption except for H alpha. Classification report is available at https://www.wis-tns.org/object/2025tzw Monitoring photometric observations are encouraged. Sincerely, Alexander Tarasenkov

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[vsnet-alert 28098] TCP J21382907+4146190 (aka AT 2025sss): new WZ Sge-type dwarf nova
by tonny.vanmunster＠gmail.com 13 Aug '25

13 Aug '25

Dear colleagues, I have just completed the analysis of my unfiltered CCD observations of TCP J21382907+4146190 (aka AT 2025sss), obtained on 2025 Aug 12/13 at CBA Extremadura Observatory. The data were collected under clear skies using a 0.40-m f/5.1 telescope and a Moravian G2-4000 CCD. I have been observing this object nightly since Aug 02nd with only one night missed. TCP J21382907+4146190 was discovered by Yuji Nakamura (Japan) on Aug 01.55 UT. It has a g=22.6 mag counterpart, implying an outburst amplitude of ~8.5 mag. Until last night, no clear modulations were visible in the light curves. The Aug 12/13 light curve now shows clear ordinary superhumps with an amplitude of 0.16 mag. Given their late onset (11 days after detection) and the large outburst amplitude, we conclude that TCP J21382907+4146190 is a new WZ Sge-type dwarf nova. A period analysis, using ANOVA, Lomb-Scargle, Generalized-Lomb-Scargle and PDM methods (Peranso 3.1) yields a combined superhump period of 0.0640 +/- 0.0012d. The object was measured at mag CV = 14.9 on Aug 12th. Image calibration and photometry were performed with the latest release of Phoranso. Further observations are strongly encouraged to refine the superhump period. I will submit my observations to AAVSO, CBA and VSNET for further analysis. With kind regards, Tonny --- Tonny Vanmunster CBA Belgium Observatory CBA Extremadura Observatory http://www.cbabelgium.co <http://www.cbabelgium.com/> m PERANSO : The Light Curve and Period Analysis Software http://www.peranso.co <http://www.peranso.com/> m PHORANSO: Photometric Reduction and Analysis Software http://www.phoranso.com <http://www.phoranso.com/>

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[vsnet-alert 28089] ASASSN-25dc; a new candidate of a WZ Sge-type dwarf nova with the double superoutburst
by Yusuke Tampo 13 Aug '25

13 Aug '25

ASASSN-25dc; a new candidate of a WZ Sge-type dwarf nova with the double superoutburst ASASSN-25dc was discovered by ASAS-SN on 2025-07-13.09 UTC at g=13.07. This outburst is also observed by ATLAS, o~15.2 mag on 2025-07-07.8 UTC and o~13.5 mag on 2025-07-10.9 UTC. The likely counterpart is Gaia DR3 6129070308813533568 with G~21.0 mag, hence the outburst amplitude is ~7.0 mag. This system underwent a short dip on 16-17th July, around 14.5 mag, and is now recovering from the dip. Lesedi telescope at Sutherland, Josch Hambsh, and Berto Monard have reported the time-resolved observations of ASASSN-25dc. PDM analysis using the overall data yields a single-peaked modulation with a period of 0.05991(4) d and an amplitude of 0.03 mag. Combining the 1-mag dip feature on the light curve and short superhump period, ASASSN-25dc can be a similar system to double-superoutburst WZ Sge-type dwarf novae, especially the period-bouncer candidates ASASSN-15jd and ASASSN-16hg (see Kimura et al. 2016,2018). https://arxiv.org/abs/1604.06344 https://arxiv.org/abs/1803.03179 The ongoing second outburst should show the evolution of ordinary superhumps. The hint of ordinary superhumps is seen in the observations on 17th July. Further 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-alert 28096] AG Carinae Decline
by Peter Williams 12 Aug '25

12 Aug '25

The SDOR / LBV star AG Car has faded in recent weeks as indicated by the following selected visual observations. CARAG 20250202.481 66 WPX CARAG 20250215.479 67 WPX CARAG 20250221.437 66 WPX CARAG 20250402.436 69 WPX CARAG 20250411.455 67 WPX CARAG 20250418.428 69 WPX CARAG 20250423.396 70 WPX CRAAG 20250502.466 70 WPX CARAG 20250530.381 71 WPX CARAG 20250620.437 71 WPX CARAG 20250624.354 71 WPX CARAG 20250712.405 72 WPX CARAG 20250719.393 72 WPX CARAG 20250806.382 72 WPX Tks & regards Peter Williams Heathcote NSW 10x50mm binoculars

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[vsnet-alert 28095] ASASSN-25df; new SU UMa-type dwarf nova
by Yusuke Tampo 08 Aug '25

08 Aug '25

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. https://vsx.aavso.org/index.php?view=detail.top&oid=10867883 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 -- ---------------------------------------------- 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-alert 28092] TCP J16271026-1030020: a new WZ Sge-type dwarf nova candidate possibly with large-amplitude early superhump
by Yusuke Tampo 05 Aug '25

05 Aug '25

TCP J16271026-1030020: a new WZ Sge-type dwarf nova candidate possibly with large-amplitude early superhump TCP J16271026-1030020 was discovered by T. Kojima on 2025-07-25.52 UTC at 13.8 mag (unfiltered). ATLAS force photometry and ASASSN also detect this outburst since 2025-07-22.3 UTC, peaking around g~12.6 mag. The Pan-STARRS1 counterpart is g=22.1(2) mag, giving the outburst amplitude of ~9.5 mag. http://www.cbat.eps.harvard.edu/unconf/followups/J16271026-1030020.html https://vsx.aavso.org/index.php?view=detail.top&oid=10867693 I have obtained the low-resolution spectrum with the Lesedi telescope at the SAAO Sutherland. This spectrum shows prominent Balmer, He II 4686, and other He I emission lines with no absorption features. Itoh-san also reported the time-resolved observations for ~45 min. The light curve shows a modulation of ~0.2 mag. These overall features suggest that TCP J16271026-1030020 is a new large-amplitude dwarf nova, most likely a WZ Sge-type, showing relatively large early superhump amplitude. Further time-resolved observations (with multiple bands, if possible) and time-resolved spectroscopy 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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