To date, several planets around young host stars were discovered, and the detail properties have been investigated. Young planets are considered to be forming or just-formed, and therefore, constraining/determining the properties is important to understand the initial stage of the planet formation and evolution. However, the number of young low-mass planets is still small. It is essential to probe the atmospheric properties as well as basic ones of such planets/companions, and to increase the number of well-studied samples.
In this presentation, we focus a planetary-mass companion around a young host star (2MASS J04372171+2651014) recently reported in Gaidos et al. (2022). The host star is a M-type dwarf belonging to Taurus star-formation region (1-5 Myr), and thus, the companion is considered to be one of the youngest and lowest-mass objects found to date. In February of 2023, we have taken the new imaging data of the 2M0437 system in the Lp band by using Subaru/IRCS. Unfortunately, the companion could not be detected at the predicted companion’s position (the detection limit of ~16 mag). The emission spectra models indicate that the flux in the Lp band would be varied mainly by cloud properties of the planet atmosphere. We will constrain and discuss the atmospheric properties of the companion, by combining our IRCS results with the VLT/ERIS data taken as Science Verification in 2022.