Astronomy and Astrophysics Seminars

Spectroscopic Diagnosis of Cool Giants & TANSPEC Data Reduction Pipeline

by Dr. Supriyo Ghosh (DAA, TIFR)

Tuesday, June 15, 2021 from to (Asia/Kolkata)
at Zoom link: ( (Meeting ID: 961 6595 5879 Passcode: DAASem15Ju) )
Meeting ID: 961 6595 5879 Passcode: DAASem15Ju
The cool giants indicate post-main-sequence evolutionary phases of low- to intermediate-mass (0.8-8 M_sun) stars having Teff below 5000 K. They are generally classified by K or M spectral type. Since the red giants are intrinsically bright and numerous while covering a wide range of ages, they can be used to characterise the stellar populations in the Galactic and extragalactic environments. To characterise the stellar populations, the precise estimation of stellar parameters of these cool giants is very important. However, such estimation remains a challenge because of their molecular near photospheric environment. In this study, we mainly focus on the low-resolution spectra. Thus, such a study would also help us to understand the usefulness of low-resolution spectrographs, such as TIRSPEC and TANSPEC, for evaluating giant star properties.
In the first part of my presentation, I shall be talking about how the spectral signature of cool giants can be used to provide quantitative diagnostic tools for deriving stellar parameters, for instance, Teff and [Fe/H]. We obtained H-band spectra of 177 cool giants having a metallicity coverage from -2.35 dex to 0.5 dex. We measured equivalent widths of several well-defined spectral features, studied the behavior of spectral features with stellar parameters, and established empirical relationships in the Bayesian framework. In addition, I shall also present preliminary results about the characterisation of Kepler red giants and the study of the clumpy winds of Wolf-Rayet stars based on TANSPEC observations. The second part of my talk will focus on the data reduction pipeline for TANSPEC. I shall discuss the workflow of the pipeline in reducing cross-disperse spectroscopic mode observations.