Hst Pancet Program: A Complete Near-Uv To Infrared Transmission Spectrum For The Hot Jupiter Wasp-79b

We present a new optical transmission spectrum of the hot Jupiter WASP-79b. We observed three transits with the STIS instrument mounted on the Hubble Space Telescope (HST), spanning 0.3-1.0 mu m. Combining these transits with previous observations, we construct a complete 0.3-5.0 mu m transmission spectrum of WASP-79b. Both HST and ground-based observations show decreasing transit depths toward blue wavelengths, contrary to expectations from Rayleigh scattering or hazes. We infer atmospheric and stellar properties from the full near-UV to infrared transmission spectrum of WASP-79b using three independent retrieval codes, all of which yield consistent results. Our retrievals confirm previous detections of H2O (at 4.0 sigma confidence) while providing moderate evidence of H- bound-free opacity (3.3 sigma) and strong evidence of stellar contamination from unocculted faculae (4.7 sigma). The retrieved H2O abundance (similar to 1%) suggests a superstellar atmospheric metallicity, though stellar or substellar abundances remain consistent with present observations (O/H = 0.3-34x stellar). All three retrieval codes obtain a precise H- abundance constraint: log( XH- 更多