Spitzer Observations of the New Luminous Red Nova M85OT2006-1

Abstract

M85OT2006-1 is the latest and most brilliant addition to the small group of known Luminous Red Novae (LRNe). An identifying characteristic of the previously detected events (M31 RV, V4322 Sgr & V838 Mon) was a spectral red-ward evolution connected with an emerging infrared component following the optical decay. Here we report on the discovery of a similar feature in Keck/NIRC and Spitzer photometry of M85OT2006-1 six months post-eruption. We find that its 2.1-22 micrometer spectral energy distribution is best described by a black body with effective temperature T_eff=950+-150 K and bolometric luminosity L=2.9+-0.5x10^5 L_sun. Assuming spherical geometry, the black body effective radius, R=2.0+-0.5x10^4 R_sun, and corresponding expansion velocity, v=870+-260 km/s, are remarkably similar to the properties of M31 RV 70 days after its eruption. Furthermore, we propose a search strategy for LRNe in the local Universe making use of the longevity of their infrared excess emission and discuss the expected number of events in the Spitzer Infrared Nearby Galaxies Survey.

manuscript after minor revisions, accepted for ApJ