Direct determination of stellar helium abundance using near-infrared chromospheric absorption line

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Our knowledge on the helium line at 10830A, i.e., He10830, is now improved based on the current research. We gathered the public observation data relevant to the formation of He10830 to review the trend between the absorption strength and other stellar parameters. The high-resolution spectra from GIANO-B and HARPS allow us to calibrate the contamination situation of blending lines around He10830. We also establish a method for measuring the strength of He10830 in a high precision by fitting all the features around that wavelength. This method is found to be applicable for both high resolution (>20000) and low resolution (~10000) spectra.Some trends of the strength of He10830 with, e.g., Teff, logR'HK and X-ray luminosity are more clear then before. The dominant formation mechanism can be constrained based on the Teff and logg. The strength of cool giants are expected to show some sensitivity with helium abundance, while that of other stars are not. We also observed a few cool giants in the globular cluster to conform this conclusion, and now the data are being reduced. We are also preparing to publish two papers about our conclusion soon. The stellar helium abundance is still an essential parameter for both the evolution of star and milky way, and it is worth further research.