GJ 1252b: A Hot Terrestrial Super-Earth with No Atmosphere

The increasing numbers of rocky, terrestrial exoplanets known to orbit nearby stars (especially M dwarfs) has drawn increased attention the possibility studying these planets' surface properties, and atmospheric compositions & escape histories. Here we report detection secondary eclipse exoplanet GJ1252b using Spitzer Space Telescope's IRAC2 4.5 micron channel. We measure an depth 149(+25/-32) ppm, corresponding a day-side brightness temperature 1410(+91/-125) K consistent with prediction for no atmosphere. Comparing our measurement models indicates that pressure <10 bar, substantially less than Venus. Assuming energy-limited escape, even 100 bar atmosphere would be lost in <1 Myr, far shorter estimated age 3.9+/-0.4 Gyr. expected mass loss could overcome by mantle outgassing, but only if mantle's carbon content were >7% - over two orders magnitude greater found Earth. therefore conclude significant Model spectra granitoid or feldspathic composition, atmosphere, are disfavored at >2 sigma. occurs just +1.4(+2.8/-1.0) min after orbital phase 0.5, indicating e cos omega=+0.0025(+0.0049/-0.0018), circular orbit. Tidal heating is likely negligible GJ1252b's global energy budget. Finally, also analyze additional, unpublished TESS transit photometry which improves precision ephemeris factor ten, provides more precise planetary radius 1.180+/-0.078 R_E, rules out any timing variations amplitudes min.