Broad-band photometric colors and effective temperature calibrations for late-type giants. II. Z<0.02

Abstract

(Abridged) We investigate the effects of metallicity on the broad-band photometric colors of late-type giants, and make a comparison of synthetic colors with observed photometric properties of late-type giants over a wide range of effective temperatures (T_eff=3500-4800 K) and gravities (log g=0.0-2.5), at [M/H]=-1.0 and -2.0. The influence of metallicity on the synthetic photometric colors is generally small at effective temperatures above \~3800 K, but the effects grow larger at lower T_eff, due to the changing efficiency of molecule formation which reduces molecular opacities at lower [M/H]. To make a detailed comparison of the synthetic and observed photometric colors of late type giants in the T_eff--color and color--color planes, we derive a set of new T_eff--log g--color relations based on synthetic photometric colors, at [M/H]=-0.5, -1.0, -1.5, and -2.0. While differences between the new T_eff--color relations and those available from the literature are typically well within ~100 K, effective temperatures predicted by the scales based on synthetic colors tend to be slightly higher than those resulting from the T_eff--color relations based on observations, with the offsets up to ~100 K. This is clearly seen both at [M/H]=-1.0 and -2.0, especially in the T_eff--(B-V) and T_eff--(V-K) planes. The consistency between T_eff--log g--color scales based on synthetic colors calculated with different stellar atmosphere codes is very good, with typical differences being well within ΔT_eff~70 K at [M/H]=-1.0 and ΔT_eff~40 K at [M/H]=-2.0.

20 pages, 11 figures, A&A accepted

Cited by in corpus (18)

• GALEV evolutionary synthesis models - I. Code, input physics and web-interface
• The GALAH Survey: Observational Overview and Gaia DR1 companion
• Lithium Depletion of Nearby Young Stellar Associations
• A very cool brown dwarf in UKIDSS DR1
• Globular Cluster Abundances from High-Resolution Integrated Light Spectra, I: 47 Tuc
• Fifteen new T dwarfs discovered in the UKIDSS Large Area Survey
• A Luminous Red Supergiant and Dusty Long-period Variable Progenitor for SN 2023ixf
• The Mass-Loss Return from Evolved Stars to the Large Magellanic Cloud IV: Construction and Validation of a Grid of Models for Oxygen-Rich AGB Stars, Red Supergiants, and Extreme AGB Stars
• Near-IR Spectra of Red Supergiants and Giants. I- Models with Solar and with Mixing-Induced Surface Abundance Ratios
• Ellipsoidal Variability and Long Secondary Periods in MACHO Red Giant Stars
• A high resolution spectral atlas of brown dwarfs
• Predicted properties of RR Lyrae stars in the SDSS photometric system
• An Exceptional Dimming Event for a Massive, Cool Supergiant in M51
• OGLE-SMC-LPV-00861 (LIN 9): the first proven Z And outburst in a Magellanic symbiotic star
• Time-series Doppler images and surface differential rotation of the effectively-single rapidly-rotating K-giant KU Pegasi
• Light and colour variations of Mira variables in the Small Magellanic Cloud
• Hubble Space Telescope Imaging of Luminous Extragalactic Infrared Transients and Variables from the SPIRITS Survey
• AT 2019qyl in NGC 300: Internal Collisions in the Early Outflow from a Very Fast Nova in a Symbiotic Binary