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

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 $\leq$ 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.Comment: 4 Tables, 8 Figures, Accepted for publication in The Astrophysical Journa

Kızıllaşmış trumpler 5 açık yıldız kümesinden seçilmiş yıldızların kızılöte bölgede kimyasal bolluk analizi

Bu tezde kızıllaşmış bir açık yıldız kümesi olan Trumpler 5'ten seçilen yıldızların sadece yüksek çözünürlüklü kızılöte tayfları kullanılarak atmosfer modeli bulma ve kimyasal bolluk analizi çalışmaları yapılmıştır. Trumpler 5 kümesinin genel özellikleri verildikten sonra model atmosfer parametrelerine ilişkin hiç bir literatür bilgisinin bulunmadığı küme üyesi yıldızların atmosferik parametrelerini belirleyebilmek için bir yöntem geliştirilmiştir. Bu yöntem, sadece kızılöte tayftan elde edilen bilgileri kullanarak model atmosfer parametrelerinin belirlenmesi prensibine dayandırılmış ve küme üyesi yıldızlara uygulanmıştır. Seçilen yıldızların dikine hızları ölçülmüş, uzaklıkları ve üye olma olasılıkları incelenmiştir. Son olarak kimyasal bolluk analizleri yapılıp karbon izotop oranları belirlenmiştir. Bu bilgiler ışığında seçilen yıldızlar ve küme üzerine elde edilen bilgiler değerlendirilmiştir. Trumpler 5 kümesi için sadece kızılöte tayf verileri kullanılarak elde edilen ayrıntılı bolluk bilgileri Gökada kimyasal evrimi açısından irdelenmiştir.In this thesis, atmospheric model and chemical abundance analysis were performed by using only high resolution infrared spectra of the stars selected from Trumpler 5, the dust-obscured open cluster. After outlining the general properties of Trumpler 5, a method has been developed for selected cluster members to find the model atmospheric parameters without any information from the literature. This method is based on determining the model atmospheric parameters of stars using only the information obtained from infrared spectra and applied to cluster member stars. Radial velocities of the selected stars were measured and their distances and probability of membership were examined. Finally, chemical abundance analyses were performed and carbon isotope ratios were determined. In the light of this information, the selected stars and the information obtained about the cluster were evaluated. The detailed abundance information obtained for Trumpler 5 from only infrared spectral data has been examined in terms of Galactic chemical evolution

Metal-poor Stars Observed with the Automated Planet Finder Telescope. III. CEMP-no Stars are the Descendant of Population III Stars

In this study, we report a probabilistic insight into the stellar mass and supernovae (SNe) explosion energy of the possible progenitors of five CEMP-no stars. This was done by a direct comparison between the abundance ratios [X/Fe] of the light-elements and the predicted nucleosynthetic yields of SN of high-mass metal-free stars. This comparison suggests possible progenitors with stellar mass range of 11 - 22\,M$_{\odot}$ and explosion energies of $0.3 - 1.8 \times 10^{51}$\,erg. The coupling of the chemical abundances with kinematics derived from $Gaia$ DR2 suggests that our sample do not enter the outer-halo region. In addition, we suggest that these CEMP-no stars are not $Gaia$-Sausage nor $Gaia$-Sequoia remnant stars, but another accretion event might be responsible for the contribution of these stars to the Galactic Halo of the Milky-Way