Spitzer Space TelescopeObservations of Var Her 04: Possible Detection of Dust Formation in a Superoutbursting Tremendous Outburst Amplitude Dwarf Nova

We present four MIPS (24 \micron) and two IRAC (3.6, 4.5, 5.8, and 8.0\micron) Spitzer observations of the newly discovered Tremendous OutburstAmplitude Dwarf nova (TOAD) Var Her 04 during decline from super-outburst. Thefour MIPS observations span 271 days and the two IRAC observations span 211days. Along the line-of-sight to Var Her 04, there is a foreground M-starwithin 1\arcsec of the variable; as a result, all of the Spitzer photometrypresented in this paper is a blend of the foreground M-star and Var Her 04. Weestimate the quiescent level of the TOAD to be $\Delta V=4-5$ magnitudes belowthat of the M-star. Based upon the spectral energy distribution and the 2MASScolors, we find the M-star to be an M3.5V dwarf at a distance of 80-130 pc.Based upon its outburst amplitude and quiescent apparent magnitude, we estimatethe distance to Var Her 04 to be 200-400 pc, suggesting that the line-of-sightforeground star is physically unrelated to the cataclysmic variable. All of theSpitzer photometry is consistent with the photospheric emission of theline-of-sight M3.5V star, except for one 24 \micron observation obtained afterthe variable re-brightened. This 24 \micron flux density is 75 $\mu$Jy($4\sigma$) above the preceding and following MIPS observations. We tentativelysuggest that the mid-infrared brightening of 75 $\mu$Jy may be associated witha dust formation event in the super-outburst ejecta. Assuming a dusttemperature of 100-400 K, we have estimated the amount of dust required. Wefind $10^{-13}-10^{-11}$ M$_\odot$ of dust is needed, consistent with amountsof mass ejection in TOADs expected during super-outburst, and possibly makingTOADs important contributors to the recycling of the interstellar medium.Comment: Accepted for publication in The Astronomical Journa