AstroNote 2026-85

We report the classification of the optical transient ZTF26aalndlm / AT2026hdo as a tidal disruption event (TDE). This source was selected by the tdescore ML classifier (Stein+2024, doi: 10.3847/2041-8213/ad3337) as a candidate TDE, primarily due to its persistent blue color and the lack of AGN-like host signatures.

ZTF26aalndlm / AT2026hdo was first detected by ZTF on 2026-03-12 as an alert with a detection of g = 20.68 mag and g-r = -0.668 mag. It was reported as a transient to TNS on 2026-03-25. The transient is still rising with g-r = -0.312 mag. We obtained a spectrum on 2026-03-25 with Kast on the 3 m Shane telescope at Lick Observatory (PI: Chornock), which revealed a blue continuum and broad features consistent with He II and possible Halpha, in line with the TDE-He or TDE-H+He classes. The redshift was secured from host galaxy stellar absorption lines (z=0.1085). With this spectrum, coupled with the persistent blue light curve, we classify ZTF26aalndlm / AT2026hdo as a TDE.

ZTF26aahjwyr / AT2026dta was first detected by ZTF on 2026-02-14 as an alert with a detection of r = 20.484 mag. Forced photometry reveals earlier detections in both g- and r-bands. The source was first reported to TNS by GOTO on 2026-02-20 (GOTO26bht; O’Neill et al., TNSTR 2026-718). The transient is slowly evolving with a current g-r = -0.204 mag. We obtained optical spectra of ZTF26aahjwyr / AT2026dta on 2026-03-12 and 2026-03-25 with Kast, and on 2026-03-16 with LDT (PI: Stein). All spectra show a consistently blue continuum with broad features consistent with H-alpha and He II 4686 at a redshift of z~0.2. No narrow emission lines are detected, but in a co-addition of all spectra, weak stellar absorption lines such as Ca II H+K from the host galaxy star light are present at a redshift of z=0.223. The combination of the persistent blue colors and broad features lead us to classify ZTF26aahjwyr / AT2026dta as a TDE-H+He.

Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Award #2407588 and a partnership including Caltech, USA; Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; University of Wisconsin at Milwaukee, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan; Operations are conducted by Caltech's Optical Observatory (COO), Caltech/IPAC, and the University of Washington at Seattle, USA.