A Two-limb Explanation for the Optical-to-infrared Transmission Spectrum of the Hot Jupiter HAT-P-32Ab

We present a new optical transmission spectrum of the hot Jupiter HAT-P-32Ab acquired with the Carnegie Observatories Spectrograph and Multiobject Imaging Camera (COSMIC) on the Palomar 200 inch Hale Telescope (P200). The P200/COSMIC transmission spectrum, covering a wavelength range of 3990–9390 Å, is composed of 25 spectrophotometric bins with widths ranging from 200 to 400 Å and consistent with previous transit measurements obtained in the common wavelength range. We derive a combined optical transmission spectrum based on measurements from five independent instruments, which, along with the 1.1–1.7 μ m spectrum acquired by the Hubble Space Telescope and two Spitzer measurements, exhibits an enhanced scattering slope blueward of a relatively flat optical continuum, a water absorption feature at 1.4 μ m, and a carbon dioxide feature at 4.4 μ m. We perform Bayesian spectral retrieval analyses on the 0.3–5.1 μ m transmission spectrum and find that it can be well explained by a two-limb approximation of 134 − 33 + 45 × solar metallicity, with a strongly hazy morning limb of 1134 − 194 + 232 K and a haze-free evening limb of 1516 − 44 + 33 K. This makes HAT-P-32Ab a promising target for James Webb Space Telescope to look for asymmetric signatures directly in the light curves.