WTP 21aaeuqd: NEOWISE Discovery and Keck Confirmation of a Heavily Reddened, Optically Missed Galactic Nova

Abstract Despite their long history, a complete inventory of Galactic novae has remained incomplete due to severe dust extinction. Recent ground-based near-infrared (NIR) as well as space-based mid-infrared (MIR) searches are providing a new window into discovering heavily obscured Galactic novae. Even with its slow cadence, archival photometric searches for large-amplitude, fast fading outbursts in the NEOWISE survey were previously used to identify Galactic nova candidates between 2014 and 2020. In this paper, we demonstrate the efficacy of the method with the discovery and NIR spectroscopy of WTP 21aaeuqd—a bright (peak W2 AB flux ≈10.5 mag), rapidly evolving ( t 2 ≈ 120 days) MIR Galactic outburst (at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>∣</mml:mo> <mml:mi>b</mml:mi> <mml:mo>∣</mml:mo> <mml:mo>≈</mml:mo> <mml:mn>1</mml:mn> <mml:mover accent="true"> <mml:mrow> <mml:mi>.</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>°</mml:mi> </mml:mrow> </mml:mover> <mml:mn>3</mml:mn> </mml:math> ). The reduced spectrum exhibits broad (≈800 km s −1 ) emission lines of H i and C i , confirming its classification as a missed Fe ii nova. This result confirms that archival infrared photometric searches are an effective way to identify nova candidates missed in optical searches.