Discovery of a likely new Galactic recurrent nova with ZTF, ASAS-SN, and NEOWISE.

ATel #17801; Danielle Frostig (CfA), Viraj Karambelkar (Columbia University), Kishalay De (Columbia), Tanishk Mohan (IIT Bombay), Robert Stein (JSI), Nathan Lourie (MIT), Sam Rose (Caltech), Rob Simcoe (MIT), Mansi Kasliwal (Caltech)
on 14 May 2026; 17:52 UT
Credential Certification: Danielle Frostig (danielle.frostig@cfa.harvard.edu)

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We report the discovery of a new recurrent nova AT2026lck in the Milky Way, based on data from the Zwicky Transient facility (ZTF, Bellm et al. 2018), the All-sky Automated Survey for Supernovae (ASAS-SN, Kochanek et al. 2017), the NEOWISE mission (Meisner et al. 2014), and spectroscopic observations from the NASA Infrared Telescope Facility. This source AT2026lck/ZTF26aatyimr was discovered and reported to the Transient Name Server by the DCAP Team using ZTF data. We identified this source independently in a dedicated search for large amplitude Galactic outbursts in ZTF data. This source was first detected by ZTF on UT 2026-04-23 in the r-band at r=19.64+/-0.15 mag, and over the next 20 days brightened to r=13.77+/-0.02 mag. The underlying source in PanSTARRS has r~20.6 mag, indicating an amplitude of ~7 magnitudes in the r-band. We further obtained J-band photometric observations of this source with the Wide-field Infrared Transient Explorer (WINTER, Lourie et al. 2020, Frostig et al. 2024) and detected the source with J=11.3+/-0.1 mag (AB) on 2026-05-07, yielding r-J~2.7 mag and suggesting an extinguished nature. The source is located at: RA = 18:43:58.56 Dec = +01:52:48.46 We obtained a near-infrared spectrum of AT2026lck with the SpeX spectrograph on the NASA Infrared Telescope Facility (IRTF) on UT 2026-05-12. Our spectrum is dominated by strong emission lines, including of H (Paschen, Brackett, and Pfund series), He I, He II, O I, C, with the He lines exhibiting P-cygni profiles. This spectrum closely resembles the early-time NIR spectrum of the Fe II classical nova V1310 Sco (Rudy et al. 2025). The spectral lines in the AT2026lck spectrum exhibit multi-component profiles with narrow (~600 km/s) components superposed on broad (~2000 km/s) components. This source underwent an eruption in 2017 that was detected by the ASAS-SN survey from 2017-02-10 to 2017-04-08, (named ASAS-SN17cf, http://asas-sn.ifa.hawaii.edu/skypatrol/objects/661428703026 ), with a V-band brightness of V~15.5 mag at its first detection, i.e., an amplitude of ~5 magnitudes relative to quiescence. The source was fading in ASAS-SN data, and the earliest non-detection was 100 days before the first detection, suggesting that the amplitude was even larger. We examined data from the NEOWISE survey and find a bright mid-infrared detection in the W1 and W2 filters around UT 2017-04-02 with W1=12.3+/-0.1 mag (AB) and W2=12.2+/-0.1 mag (AB). These values are consistent with the mid-IR brightness of fading classical nova eruptions e.g., Zuckerman et al. 2023. The bright IR flare and the long-duration (>50 days), large amplitude optical outburst suggest that this eruption was also a classical nova, rather than a dwarf nova. We examined even older NEOWISE images and found a faint, but clear detection in a stacked W2-band image taken around UT 2010-03-31. Performing image subtraction relative to another NEOWISE epoch (De et al. 2023), we clearly detect a source at the position of AT2026lck with W2 ~ 17 mag (AB). This indicates that the system was also undergoing an outburst in 2010. No other bright detections are seen in any other NEOWISE images. A visualization of the NEOWISE stacks, where the 2010 and 2017 detections are clearly visible, can be seen at the Backyard Works website here. Given these three roughly equally spaced eruptions of this system, we suggest that AT2026lck is a new recurrent nova in the Milky Way, with a recurrence period of approximately 9 years. This would be the eleventh known recurrent nova in the Milky Way, and the first to be discovered by modern time-domain surveys. Follow-up observations are encouraged.