Effective Temperature Estimations from Line Depth Ratios in the \H\ and \K-band Spectra of IGRINS

Abstract

Determining accurate effective temperatures of stars buried in the dust-obscured Galactic regions is extremely difficult from photometry. Fortunately, high-resolution infrared spectroscopy is a powerful tool for determining the temperatures of stars with no dependence on interstellar extinction. It has long been known that the depth ratios of temperature-sensitive and relatively insensitive spectral lines are excellent temperature indices. In this work, we provide the first extensive line depth ratio (LDR) method application in the infrared region that encompasses both \H\ and \K\ bands (1.48 $\mu$m - 2.48 $\mu$m). We applied the LDR method to high-resolution (R $\simeq$ 45,000) \H\ and \K-band spectra of 110 stars obtained with the Immersion Grating Infrared Spectrograph (IGRINS). Our sample contained stars with 3200 $<$ \teff\ (K) $<$ 5500, 0.20 $\le$ log g $<$ 4.6, and $-$1.5 $<$ [M/H] $<$ 0.5. Application of this method in the \K-band yielded 21 new LDR$-$\teff\ relations. We also report five new LDR$-$\teff\ relations found in the \H-band region, augmenting the relations already published by other groups. The temperatures found from our calibrations provide reliable temperatures within $\sim$70 K accuracy compared to spectral \teff\ values from the literature.

4 Tables, 8 Figures, Accepted for publication in The Astrophysical Journal

References in corpus (17)

• The Gaia mission
• A new implementation of the infrared flux method using the 2MASS catalogue
• Precise radial velocities of giant stars. III. Spectroscopic stellar parameters
• Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program II: Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd and Eu
• Abundances in the Local Region II: F, G and K Dwarfs and Subgiants
• Stellar parameters and chemical abundances of 223 evolved stars with and without planets
• Exploiting the Gaia EDR3 photometry to derive stellar temperatures
• linemake: An Atomic and Molecular Line List Generator
• The Chemical Compositions and Evolutionary Status of Red Giants in the Open Cluster NGC 752
• Effective Temperatures of Low-Mass Stars from High-Resolution H-band Spectroscopy
• Method to Estimate the Effective Temperatures of Late-Type Giants using Line-Depth Ratios in the Wavelength Range 0.97-1.32$\mu$m
• Chemical Abundances Of Open Clusters From High-Resolution Infrared Spectra. II. NGC 752
• The chemical compositions and evolutionary status of red giants in the open cluster NGC 6940
• Chemical Abundances Of Open Clusters From High-Resolution Infrared Spectra. I. NGC 6940
• The metallicity effect on line-depth ratios in APOGEE $H$-band spectra
• Line-depth ratios as indicators of effective temperature and surface gravity
• The effect of surface gravity on line-depth ratios in the wavelength range 0.97-1.32 μm

Cited by in corpus (6)

• M giants with IGRINS I. Stellar parameters and $\alpha$-abundance trends of the solar neighborhood population
• 10 Years of Archival High-Resolution NIR Spectra: The Raw and Reduced IGRINS Spectral Archive (RRISA)
• Effective temperatures of classical Cepheids from line-depth ratios in the H-band
• Fluorine abundances in CEMP stars at the lowest metallicity: Hints on the nature of the first stars
• M giants with IGRINS IV. Identification and characterization of a near-IR line of the s-element Barium
• Cepheid Metallicity in the Leavitt Law (C--MetaLL) survey: VIII. High-Resolution IGRINS Spectroscopy of 23 Classical Cepheids: Validating NIR Abundances