Detection of a possible Galactic Nova or TOAD Dwarf-Nova Outburst
ATel #17058; I. J. Lima (LNA/Brazil), A. S. Oliveira (Univap/Brazil), C. V. Rodrigues (INPE/Brazil), G. J. M. Luna (UNAHUR/CONICET/Argentina), E. E. O. Ishida (CNRS/France), N. Palivanas (Univap/Brazil), A. C. Mattiuci (INPE/Brazil)
on 28 Feb 2025; 17:42 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Isabel de Jesus Lima (isabellima01@gmail.com)
Subjects: Optical, Cataclysmic Variable, Nova
We report an outburst of the source ZTF25aacfjde, flagged as an anomaly in the ZTF data stream by a dedicated Fink Telegram bot. The ZTF light curve and other information can be accessed at https://fink-portal.org/ZTF25aacfjde. The outburst is also present in ASAS-SN data and reported in CBAT (http://www.cbat.eps.harvard.edu/unconf/followups/J07222683+6220548.html). ZTF25aacfjde (GALEX J072227.0+622057) is a UV source selected as a white dwarf (WD) candidate based on Gaia DR2 and EDR3 (Gentile Fusillo et al., 2019, MNRAS, 482,4570; Gentile Fusillo et al., 2021, MNRAS, 508, 3877). The probability of the source being a WD is larger than 99%. These authors estimated the WD effective temperature as 14.500 (+- 500) K. The Gaia photogeometric distance to the source is 501 (+22;-43) pc (Bailer-Jones et al, 2021, AJ, 161, 147B). Its quiescent g magnitudes in ASAS-SN and ZTF measurements have an upper limit of 18-20 mag. A brightening by up to 7 magnitudes was observed by the ZTF and ASAS-SN on 21 January 2025. The system is currently fading, with its magnitude now at g = 17. TESS observed the field in five sectors prior to the outburst, but no significant signal was detected in periodicity searches applied to aperture photometry data. We suggest two possible explanations for the flux enhancement, in a cataclysmic variables scenario: a nova eruption or a dwarf-nova outburst. Some dwarf novae classified as TOADs (Tremendous Outburst Amplitude Dwarf novae) exhibit outbursts of 6-10 mag lasting days (Howell et al., 1995, ApJ, 439, 337). Spectroscopic follow-up is required to confirm the nature of the event. This telegram derives from a dedicated Telegram bot, publicly available at https://t.me/ZTF_anomaly_bot , as part of a series of public bots provided by Fink. The full list can be found at https://fink-broker.readthedocs.io/en/latest/broker/filters/.
