The Optical to Infrared Extinction Law of Magellanic Clouds Based on Red Supergiants and Classical Cepheids

Precise interstellar dust extinction laws are important to infer the intrinsic properties of reddened objects and correctly interpret observations. In this work, we attempt measure optical--infrared Large Small Magellanic Clouds (LMC SMC) by using red supergiant (RSG) stars classical Cepheids as tracers. The spectroscopic RSG samples constructed based on APOGEE spectral parameters, Gaia astrometric data, multi-band photometry. We establish effective temperature--intrinsic color relations for determine excess ratio (CER) E(lambda-GRP)/E(GBP-GRP) LMC SMC. use derive base relative A_GRP/E(GBP-GRP). results 1.589+-0.014 1.412+-0.041 By combining CERs with A_GRP /E(GBP-GRP), coefficients A_lambda/A_GRP determined 16 bands. adjust parameters Rv-dependent obtain average law SMC Rv=3.40+-0.07 Rv=2.53+-0.10, which consistent Gordon et al. (2003). optical bands, adjusted Rv curves agree observations deviations less than 3%.