  The atmosphere on the dayside of a highly irradiated close-in gas giant (also
known as a hot Jupiter) absorbs a significant part of the incident stellar
radiation which again gets re-emitted in the infrared wavelengths both from the
day and the night sides of the planet. The re-emitted thermal radiation from
the night side facing the observers during the transit event of such a planet
contributes to the transmitted stellar radiation. We demonstrate that the
transit spectra at the infrared region get altered significantly when such
re-emitted thermal radiation of the planet is included. We assess the effects
of the thermal emission of the hot Jupiters on the transit spectra by
simulating observational spectroscopic data with corresponding errors from the
different channels of the upcoming James Webb Space Telescope. We find that the
effect is statistically significant with respect to the noise levels of those
simulated data. Hence, we convey the important message that the planetary
thermal re-emission must be taken into consideration in the retrieval models of
transit spectra for hot Jupiters for a more accurate interpretation of the
observed transit spectra.
