GCN 44194: EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph

Robert Stein (UMD/JSI/NASA GSFC), Kaustav Das (Caltech), Christoffer Fremling (Caltech), Tomas Ahumada (NOIRLab), Akash Anumarlapudi (UNC CH), Ryan Chornock (UC Berkeley),Michael C. Davis (UMN), K-Ryan Hinds (Caltech), Mansi Kasliwal (Caltech), Jillian Rastinejad (UMD), Gokul Srinivasaragavan (UMD) and Yuhan Yao (UC Berkeley) report, on behalf of the ZTF collaboration:

We observed AT2026hir/ZTF26aapviim, the optical counterpart (Anumarlapudi et al, GCN #44120) to EP260324A (Wu et al., ATEL #17728), with the Next Generation Palomar Spectrograph (NGPS; AstroNote 2024-340) on the Palomar 5.1m Hale Telescope (P200). Our observations began on 2026-03-27T03:51:37 (~3 days after the EP trigger), and data were reduced using the standard NGPS pipeline.

The spectrum was extremely blue, as also noted by Zhu et al. (Astronote #2026-87). From our spectrum, in addition to the continuum, we see an excess that would be consistent with broad He II with a velocity of ~15000 km / s. However, we have not performed host galaxy subtraction, and we caution that the SNR is insufficient to be certain whether this broad feature is real.

In any case, given the nuclear location (GCN #44120) and blue spectrum which is either featureless or has broad He, our observations would be consistent with a TDE-F or TDE-He classification for this source. However, we plan for and encourage additional multi-wavelength observations to secure the classification. The transient is bright (mg=17.3 in the latest ZTF data), so remains accessible to a wide variety of ground-based telescopes.