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 {\AA}, is composed of 25 spectrophotometric bins with widths ranging from 200 to 400 {\AA} 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 $\mu$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~$\mu$m, and a carbon dioxide feature at 4.4~$\mu$m. We perform Bayesian spectral retrieval analyses on the 0.3--5.1 $\mu$m transmission spectrum and find that it can be well explained by a two-limb approximation of {\bf\color{red}$134^{+45}_{-33}\times$} solar metallicity, with a strongly hazy morning limb of {\bf\color{red}$1134^{+232}_{-194}$~K} and a haze-free evening limb of {\bf\color{red}$1516^{+33}_{-44}$~K}. This makes HAT-P-32Ab a promising target for James Webb Space Telescope to look for asymmetric signatures directly in the light curves.