Revision of Stellar Intrinsic Colors in the Infrared by the Spectroscopic Surveys

TL;DR

This paper recalculates the intrinsic infrared colors of normal stars using spectroscopic survey data, providing empirical relations based on stellar temperature and class, with implications for interstellar extinction studies.

Contribution

It presents new empirical relations for stellar intrinsic colors in infrared bands, considering different stellar classifications and metallicities, based on large spectroscopic surveys.

Findings

Metallicity has minimal impact on infrared colors.

Derived intrinsic colors agree with previous near-infrared studies.

Separate intrinsic colors are provided for M-type stars.

Abstract

Intrinsic colors of normal stars are derived in the popularly used infrared bands involving the 2MASS/JHKs, WISE, Spitzer/IRAC and AKARI/S9W filters. Based on three spectroscopic surveys -- LAMOST, RAVE and APOGEE, 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 zero-reddening stars are selected from the blue edge in the $J-\lambda$ versus (Teff) diagram. It is found that metallicity has little effect on the infrared colors. In the near-infrared bands, our results agree with previous work. In addition, the color indexes H-W2 and Ks-W1 that are taken as constant to calculate interstellar extinction are discussed. The intrinsic color of M-type stars are derived separately due to lack of accurate measurement of their effective temperature.