title: Envelope Dispersion and Disk Emergence around the Transitional Class I Object L43 authors: Shin Koyamatsu, Shigehisa Takakuwa, Masahiko Hayashi, Nagayoshi Ohashi, and Satoshi Mayama abstract: We present SMA data of the $^{12}$CO ($J$=2--1), $^{13}$CO ($J$=2--1), and the C$^{18}$O ($J$=2--1) lines and the 225\,GHz continuum emission toward L43, a transitional protostellar object from Class I to Class II. The 225\,GHz continuum emission shows a weak ($\sim$22\,mJy), unresolved dusty component associated with the central star. The mass of the dusty component is estimated to be $\sim$2.7$\times$10$^{-3}$\,M$_{\odot}$, which is orders of magnitude lower than that of compact dusty components around other Class 0 and I objects, but comparable to that of protoplanetary disks around Class II stars. The $^{12}$CO and $^{13}$CO emission exhibit the redshifted collimated outflow toward the northeast and the widely-opened, $U$-shaped blueshifted outflow shell to the opposite direction. The C$^{18}$O emission shows two molecular blobs located ``inside'' the $U$-shaped outflow shell, while there is no C$^{18}$O emission associated with the central star. The LTE masse of these blobs are estimated to be $\sim$10$^{-3}$\,M$_{\odot}$, much smaller than the virial masses of $\sim$1\,M$_{\odot}$, suggesting that these blobs are gravitationally unbound. We propose that the envelope material in the close vicinity ($\sim$7000\,AU) of this transitional object, L43, is being dissipated through the interaction with the associated outflow and that the protoplanetary disk just formed inside the envelope has emerged.