The spectrum of TMR-1C is consistent with a background star

In a previous paper we proposed that there may be a population of runaway p lanets and brown dwarfs that formed via ejection from multiple-star systems . We further suggested TMR-1C as a candidate runaway protoplanet. Hubble Sp ace Telescope NICMOS images of the Class I protostar TMR-1 (IRAS 04361 + 25 47) reveal TMR-1C as a faint near-infrared companion with 10." 0 = 1400 AU projected separation. The central protostar is itself resolved as a close b inary with 0." 31 = 42 AU separation, surrounded by circumstellar reflectio n nebulosity. A long, narrow filament seems to connect the protobinary to t he faint companion TMR-1C, suggesting a physical association, which can pla usibly be explained if TMR-1C was ejected by the protobinary. This paper pr esents near-infrared grism spectroscopy to constrain the effective temperat ure of TMR-1C, obtained with the Near-Infrared Camera (NIRC) at Keck Observ atory. To interpret the data, we construct a grid of extincted M dwarf spec tra to compare with the low-resolution (R similar to 120) NIRC spectrum. Th e assumed extinction corresponds to standard interstellar dust. With the ad ditional assumption that no near-infrared dust excess contributes to the sp ectrum, then M4.5 is the latest spectral type TMR-1C can have within the un certainties. Adopting 2 sigma error bars, this translates to T-eff > 2700 K effective temperature and A(K) = 2.5 +/- 0.75 extinction at K band (A(V) = 22 +/- 6.6 for standard dust). We compare the luminosity and effective tem perature of TMR-1C with evolutionary tracks of young giant planets and brow n dwarfs in a theoretical H-R diagram. Given a relatively low inferred lumi nosity of similar to 10(-3) L., then TMR-1C is hotter than predicted by ava ilable theoretical models. However, the models are very uncertain at such y oung ages, less than 300,000 yr, so that it is unclear whether the theoreti cal tracks by themselves provide a suitably strong test. Given the quality of the observed spectrum, only a partial answer is possible. The new data d o not lend weight to the protoplanet interpretation, and the results remain consistent with the explanation that TMR-1C may be a background star. We d iscuss additional observational tests that may be useful.