2020RNAAS...4...80T

We present new spectroscopic and photometric observations of ATLAS18qtd/SN 2018cqj, a fast-declining SN Ia with variable Hα emission in previously published nebular phase spectra. ATLAS18qtd is undetected in both spectroscopic and photometric observations which occurred at ∼540 days after maximum light and ∼230 days after the last Hα detection. With these new non-detections, we place an upper limit on the Hα luminosity of \lesssim 1.1 x 10³⁶ erg s^–1 ndicating the Hα flux decreased by a factor of \rsim 4 since the previous detection. This upper limit excludes Hα emission that plateaus or increases since the previous detection but cannot confirm that the Hα emission decay rate is equivalent to the supernova decay rate.