The intrinsic colors of stars in the Milky Way suffer the reddening due to interstellar extinction. Intrinsic colors of stars were given in the popularly used infrared bands. But we would derive more credible results with more bands.
The work is several infrared photometric data involving the 2MASS/JHKS, WISE, Spitzer/IRAC and AKARI /S9W filters, and spectral data based on three spectroscopic surveys – LAMOST, RAVE and APOGEE. By using the stellar parameters from spectral data, stars are classified
into groups of giants and dwarfs, as well as metal-normal and metal-poor stars. An empirical analytical relation of the intrinsic color is obtained with stellar effective temperature (Teff) for each group of stars after the zeroreddening stars are selected from the blue edge in the color versus Teff diagram.
The effect of metallicity on the infrared colors are discussed. The intrinsic color of M-type stars are derived separately due to lack of accurate measurement of their Teff.
Color-Teﬀ diagrams of dwarf stars from the LAMOST survey. Gray/black points decode all the stars that pass data quality control, blue crosses decode the selected zero-reddening stars and red line is the ﬁtting curve.