The detection of superhumps confirms Gaia20eud as an SU UMa-type dwarf nova
ATel #17932; D. Yu. Rusanova (ASPD TShNU of Kyiv), F.-J. Hambsch (VVS, GEOS, BAV), A. O. Simon (ASPD TShNU of Kyiv), P. J. Mikolajczyk (U. Wroclaw/NCBJ, PL), L. Wyrzykowski (U. Warsaw/NCBJ, PL/EASST. eu), K. Kotysz (U. Wroclaw/U. Warsaw, PL)
on 31 Jul 2026; 21:55 UT
Credential Certification: Andrew Simon (skazhenijandrew@gmail.com)
Subjects: Optical, Cataclysmic Variable, Star, Transient, Variables
Our analysis of the BHTom light curve of Gaia20eud/AT 2020wjy/ZTF18abmvqfo indicates that the object exhibits two distinct types of outbursts: normal outbursts and likely superoutbursts. The interval between these longer outbursts is approximately 300-380 days. The previous probable superoutburst occurred in August 2025. On 2026 July 25, ZTF observations detected the object at 17.8m, significantly brighter than its quiescent magnitude of about 20.2m, indicating the onset of a new outburst. Given the elapsed time since the previous probable superoutburst (about 330 days), together with the substantial increase in brightness, we considered the possibility that the object had entered a superoutburst.
To test this hypothesis, photometric observations were conducted on 2026 July 31 with a C14 f/6.8 telescope at Franz-Josef Hambsch's Remote Observatory Atacama Desert (ROAD) in Chile to search for superhumps. The data were uploaded to the object's BHTOM page immediately after the observing run. The resulting light curve (Fig. 1) clearly shows superhumps. The detection of superhumps confirms Gaia20eud as an SU UMa-type dwarf nova.
The observations covered MJD 61252.12463-61252.27545 corresponding to approximately 3.6 hours. The superhump period was measured to be 0.0825(7)d (Fig. 2). The peak-to-peak amplitude is about 0.25m (Fig. 3). Both values were derived using the Lomb-Scargle periodogram implemented in SciPy (scipy.signal.lombscargle).
Further observations are strongly encouraged. Observers are invited to upload their observations to the object's BHTOM page, where all submitted data are automatically processed: https://bhtom.space/public/targets/Gaia20eud.
BHTOM is based on the open-source TOM Toolkit by LCO and has been developed with funding from the OPTICON-RadioNet Pilot (ORP) of the European Union's Horizon 2020 research and innovation programme under grant agreement No 101004719 (2021-2025). This project has received funding from the European Union's Horizon Europe Research and Innovation programme ACME under grant agreement No 101131928 (2024-2028).
