# # Program information file # PROGRAM_ID 2023A070 PROGRAM_TITLE In search of the missing stellar mergers: A systematic search for mid-infrared outbursts near the Galactic plane PROGRAM_INV1 Kishalay De PROGRAM_INV2 Morgan MacLeod PROGRAM_INV3 Jacob Jencson PROGRAM_INV4 Ryan Lau PROGRAM_INV5 Robert Simcoe PROGRAM_SCICAT stellar PROGRAM_ABSTRACT_BEG Stellar mergers and common envelope events are ubiquitous in the lives of binary stars. Altering the fundamental stellar mass function as well as providing gateways to compact binary systems detectable in gravitational waves, stellar mergers play a central role in our understanding of binary stellar astrophysics. Although expected to be common in the Galaxy [0.2-2 per year], the last Galactic merger was observed nearly 15 years ago. While the optical emission associated with these cataclysms is short-lived and difficult to detect, their mid-infrared [MIR] transient emission is unique and extremely long-lived [ ...thousands of days]. We have recently used publicly available NASA NEOWISE data to carry out the first systematic search for mid-infrared [MIR] outbursts near the Galactic plane, uncovering several hundreds of previously unknown transient events. Using a systematic selection strategy for identifying merger candidates based on previous events as well as theoretical predictions, we propose to use SpeX on IRTF for i] observing the candidates with near-infrared [NIR] imaging to search for an obscured remnant star and ii] detect molecular absorption features with spectroscopy in transients consistent with recent mergers that are expected to be bright in the NIR. This search is uniquely positioned to finally unveil the demographics of these spectacular events in our Galactic backyard, and reveal i] the rate of Galactic stellar coalescences, ii] relationship between the merger kinematics and their end-products and iii] the mass spectrum of merging binary stars. PROGRAM_ABSTRACT_END