Spectroscopy and photometry of AT 2026rdg, a highly reddened FeII-type nova
ATel #17867; U. Munari (INAF Padova), P. Valisa, S. Dallaporta, and A. Maitan (ANS Collaboration)
on 2 Jul 2026; 22:34 UT
Credential Certification: U. Munari (ulisse.munari@oapd.inaf.it)
Referred to by ATel #: 17868
M. Ning and H. Lin, on behalf of the DCAP collaboration, reported to the TNS the discovery of the transient AT 2026rdg (= ZTF26abemjfk = DCAP 238) at g = 14.45 and r = 12.53 (AB mag) on 2026-07-01.305 UT. The discovery was confirmed by K. Sokolosky at an unfiltered magnitude of 11.77 on NWM images taken on 2026-07-01.836 UT. Subsequently, K. Yoshimoto reported to the TNS that photometric observations of AT 2026rdg on 2026-07-02.653 UT yielded B = 13.33, V = 11.26, and I = 9.66 mag.
The source closest to the reported position lies 2.7 arcsec away and has reported magnitudes of BP=21.38 and RP=17.44 in Gaia DR3, J=14.05 in 2MASS, and r=20.39 mag in Pan-STARRS1 (PS1).
On 2026-07-02.865 UT, we obtained a low-resolution spectrum of AT 2026rdg using the Varese 0.84m telescope equipped with the Mark III Multi-Mode Spectrograph, covering the 3850-9050 Ang range at a dispersion of 1.44 Ang/pix. The spectrum displays broad Balmer lines in emission (FWHM ~1100 km/s) flanked by P-Cygni absorptions blue-shifted by 680 km/s. OI 7772 and Fe II lines are also present in emission, showing a profile similar to that of the Balmer lines. OI 8446 is not (yet) seen in emission. Furthermore, the spectrum displays very strong diffuse interstellar bands (DIBs) and interstellar NaI and KI lines, indicating that the steep red slope is caused by a large reddening, with E(B-V) possibly as high as 2 mag. Overall the spectrum resembles that of a FeII-class nova around maximum brightness.
On 2026-07-02.90 UT, we also obtained BVRI photometry of AT 2026rdg using ANS Collaboration telescopes ID 0310 and ID 2202. The photometry was transformed to the Landolt system via color equations solved on APASS DR8 field stars, yielding B = 13.60, V = 11.24, R = 9.73, and I = 8.25. The B-V = 2.36 color confirms the high reddening inferred from the interstellar features present in the spectrum.
