The effective temperature , one of the most fundamental atmospheric parameters of a star , can be estimated using various methods , and here we focus on the method using line-depth ratios ( LDRs ) .
This method combines low- and high-excitation lines and makes use of relations between LDRs of these line pairs and the effective temperature .
It has an advantage , for example , of being minimally affected by interstellar reddening , which changes stellar colours .
We report 81 relations between LDRs and the effective temperature established with high-resolution , \lambda / \Delta \lambda \sim 28 , 000 , spectra of nine G- to M-type giants in Y and J bands .
Our analysis gives the first comprehensive set of LDR relations for this wavelength range .
The combination of all these relations can be used to determine the effective temperatures of stars that have 3700 < T _ { \mathrm { eff } } < 5400 \mathrm { K } and -0.5 < \mathrm { [ Fe / H ] } < +0.3 \mathrm { dex } to the precision of \pm 10 \mathrm { K } in the best cases .