Red supergiant stars in IC 1613 and metallicity-dependent mixing length in the evolutionary model
| Autor: | Chun, Sang-Hyun, Yoon, Sung-Chul, Oh, Heeyoung, Park, Byeong-Gon, Hwang, Narae |
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| Rok vydání: | 2022 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| DOI: | 10.3847/1538-4357/ac94c0 |
| Popis: | We report a spectroscopic study on red supergiant stars (RSGs) in the irregular dwarf galaxy IC 1613 in the Local Group. We derive the effective temperatures ($T_\mathrm{eff}$) and metallicities of 14 RSGs by synthetic spectral fitting to the spectra observed with the MMIRS instrument on the MMT telescope for a wavelength range from 1.16 $\mu$m to 1.23 $\mu$m. A weak bimodal distribution of the RSG metallicity centered on the [Fe/H]=$-0.65$ is found, which is slightly lower than or comparable to that of the Small Magellanic Cloud (SMC). There is no evidence for spatial segregation between the metal rich ([Fe/H]$>-0.65$) and poor ([Fe/H]$<-0.65$) RSGs throughout the galaxy. The mean effective temperature of our RSG sample in IC 1613 is higher by about 250 K than that of the SMC. However, no correlation between $T_\mathrm{eff}$ and metallicity within our RSG sample is found. We calibrate the convective mixing length ($\alpha_{\mathrm{MLT}}$) by comparing stellar evolutionary tracks with the RSG positions on the HR diagram, finding that models with $\alpha_{\mathrm{MLT}}=2.2-2.4 H_P$ can best reproduce the effective temperatures of the RSGs in IC 1613 for both Schwarzschild and Ledoux convection criteria. This result supports our previous study that a metallicity dependent mixing length is needed to explain the RSG temperatures observed in the Local Group, but we find that this dependency becomes relatively weak for RSGs having a metallicity equal to or less than the SMC metallicity. Comment: 15 pages, 7 figures, accepted in ApJ |
| Databáze: | arXiv |
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