Intrinsic colors of normal stars are derived in the popularly used infrared bands involving the 2MASS/JHK S , 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 T eff for each group of stars after the zero-reddening stars are selected from the blue edge in the J − λ versus T eff 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 − W 2 and K S − W 1 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.Subject headings: stars: fundamental parameters -infrared: stars Johnson system, and a new K S band which has a short cut at the long wavelength end.The space projects, Spitzer, WISE and AKARI, observed either all the sky or a large part of the sky. They adopted completely new filter bands in mid-infrared in which no intrinsic color indexes have been determined for stars.In this work we apply the basic idea of the method of Ducati et al. (2001) to the greatly improved large-scale photometric and spectroscopic data to determine the infrared intrinsic color indexes of normal stars. We first describe the data in Sec. 2, and then the method in Sec. 3. The result and discussion are presented in Sec. 4, and finally we summarise our work in Sec. 5. Data and Sample SelectionThe filter bands to deal with involve the most popularly used, that is, in the large-scale survey. Besides, these bands are different from the Johnson system. Specifically, we study the intrinsic colors of stars related to the 2MASS/JHK S in the near-infrared, the Spitzer /IRAC, WISE and AKARI /S9W bands in the mid-infrared. The 2MASS/JH bands conform to the Johnson system and form the bridge to compare with classical results. Photometric and Spectroscopic DataBoth photometric and spectroscopic data are taken from a few surveys, which expand the band coverage and enlarge the samples. for the M-type stars with the APOGEE result at the overlapping range of T eff from about 3600 K to 3800 K. Zhong et al. (2015) pointed out that there are about 4.7% dwarfs in the sample of giant M-type stars. Although we tried to remove the dwarf contamination by applying the color criteria, the sample may not be pure of giant stars. It is apparent that our derived colors of M giants are between M dwarfs and giants. In order to keep internal consistency, the derived color indexes of M-type giants are shifted to match the analytical J − λ vs. T eff relation derived from APOGEE at the overlapping range of T eff , i.e. from about 3800 K to 3600 K and for subtypes M0 and M1. It turns out that the shifts are 0.15 for J − H, 0.22 for J − K S , 0.24 for...

Interstellar extinction in ultraviolet is the most severe in comparison with optical and infrared wavebands and a precise determination plays an important role in correctly recovering the ultraviolet brightness and colors of objects. By finding the observed bluest colors at given effective temperature and metallicity range of dwarf stars, stellar intrinsic colors,B and C 0 FUV,NUV , are derived according to the stellar parameters from the LAMOST spectroscopic survey and photometric results from the GALEX and APASS surveys. With the derived intrinsic colors, the ultraviolet color excesses are calculated for about 25,000 A-and F-type dwarf stars. Analysis of the color excess ratios yields the extinction law related to the GALEX UV bands: E NUV,B /E B,V = 3.77, E FUV,B /E B,V = 3.39, E FUV,NUV /E B,V = −0.38. The results agree very well with previous works in the N U V band and in general with the extinction curve derived by Fitzpatrick (1999) for R V = 3.35.

The aim of this paper is to establish a complete sample of red supergiants (RSGs) in M31 and M33. The member stars of the two galaxies are selected from the near-infrared (NIR) point sources after removing the foreground dwarfs from their obvious branch in the J − H/H − K diagram with the archival photometric data taken by the UKIRT/WFCAM. This separation by NIR colors of dwarfs from giants is confirmed by the optical/infrared color–color diagrams (r − z/z − H and B − V/V − R) and the Gaia measurement of parallax and proper motion. The RSGs are then identified by their outstanding location in the members’ J − K/K diagram due to high luminosity and low effective temperature. The resultant sample has 5498 and 3055 RSGs in M31 and M33 respectively, which should be complete because the lower limiting K magnitude of RSGs in both cases is brighter than the complete magnitude of the UKIRT photometry. Analysis of the control fields finds that the pollution rate in the RSG sample is less than 1%. The by-product is the complete sample of oxygen-rich asymptotic giant branch stars (AGBs), carbon-rich AGBs, thermally pulsing AGBs, and extreme AGBs. In addition, the tip-RGB is determined together with its implication on the distance modulus to M31 and M33.

Ratios of carefully selected line depths are sensitive to stellar effective temperature (T eff ). Relations established between line-depth ratio (LDR) and T eff allow one to determine T eff precisely. However, LDRs can also depend on metallicity and abundance ratios, which can limit the accuracy of the LDR method unless such effects are properly taken into account. We investigate the metallicity effect using H-band spectra and stellar parameters published by the APOGEE project. We clearly detected the effects of metallicity and abundance ratios; T eff derived from a given LDR depends on the metallicity, 100-800 K dex −1 , and the dependency on the abundance ratios, 150-1000 K dex −1 , also exists when the LDR involves absorption lines of different elements. For the 11 line pairs in the H-band we investigated, the LDR-T eff relations with abundance-related terms added have scatters as small as 30-90 K within the range of 3700 < T eff < 5000 K and −0.7 < [Fe/H] < +0.4 dex. By comparing the observed spectra with synthetic ones, we found that saturation of the absorption lines at least partly explains the metallicity effect.