摘要：We present a new ground-based visual transmission spectrum of the hot Jupiter WASP-43b, obtained as part of the ACCESS Survey.The spectrum was derived from four transits observed between 2015 and 2018, with combined wavelength coverage between 5300 and 9000 Å and an average photometric precision of 708 ppm in 230 Å bins.We perform an atmospheric retrieval of our transmission spectrum combined with literature Hubble Space Telescope/WFC3 observations to search for the presence of clouds/hazes as well as Na, K, Hα, and H2O planetary absorption and stellar spot contamination over a combined spectral range of 5318–16420 Å.We do not detect a statistically significant presence of Na i or K i alkali lines, or Hα in the atmosphere of WASP-43b.We find that the observed transmission spectrum can be best explained by a combination of heterogeneities on the photosphere of the host star and a clear planetary atmosphere with H2O.This model yields a log evidence of 8.26 ± 0.42 higher than a flat (featureless) spectrum.In particular, the observations marginally favor the presence of large, low-contrast spots over the four ACCESS transit epochs with an average covering fraction ${f}_{\mathrm{het}}={0.27}_{-0.16}^{+0.42}$ and temperature contrast ΔT = 132 K ± 132 K.Within the planet's atmosphere, we recover a log H2O volume mixing ratio of $-{2.78}_{-1.47}^{+1.38}$, which is consistent with previous H2O abundance determinations for this planet.
