Spectroscopic phase curves of transiting hot Jupiters are spectral
measurements at multiple orbital phases, giving a set of disc-averaged spectra
that probe multiple hemispheres. By fitting model phase curves to observations,
we can constrain the atmospheric properties of hot Jupiters such as molecular
abundance, aerosol distribution and thermal structure, which offer insights
into their dynamics, chemistry, and formation. In this work, we propose a novel
2D temperature scheme consisting of a dayside and a nightside to retrieve
information from near-infrared phase curves, and apply the scheme to phase
curves of WASP-43b observed by HST/WFC3 and Spitzer/IRAC. In our scheme,
temperature is constant on isobars on the nightside and varies with
cosn(longitude/Ο΅) on isobars on the dayside, where n and
Ο΅ are free parameters. We fit all orbital phases simultaneously using
the radiative transfer package NEMESISPY coupled to a Bayesian inference code.
We first validate the performance of our retrieval scheme with synthetic phase
curves generated from a GCM, and find our 2D scheme can accurately retrieve the
latitudinally-averaged thermal structure and constrain the abundance of H2βO
and CH4β. We then apply our 2D scheme to the observed phase curves of
WASP-43b and find: (1) the dayside temperature-pressure profiles do not vary
strongly with longitude and are non-inverted; (2) the retrieved nightside
temperatures are extremely low, suggesting significant nightside cloud
coverage; (3) the H2βO volume mixing ratio is constrained to
5.6Γ10β5--4.0Γ10β4, and we retrieve an upper bound for
CH4β at βΌ10β6.Comment: 23 pages, 20 figures, 3 tables, accepted for publication in MNRA