| Abstract: In a hydrogen-dominated visible universe, a rare class of stars known as hydrogen-deficient carbon stars (HdCs) stand out as supergiants with chemically peculiar atmospheres that are hydrogen-poor and carbon-rich. Unlike normal stars, the optical spectra of HdCs display either extremely weak or absent hydrogen Balmer lines for their corresponding effective temperatures. The mechanism behind their formation and evolution remains an unsolved mystery in stellar astrophysics. Surface elemental abundance provides essential information about stars, offering insights into their formation, evolution, and even their origin. Elemental abundances of HdC stars have not been studied adopting state-of-the-art model atmospheres combined with radiative transfer techniques. The growing number of HdC stars further adds statistical significance to studies focussed on measuring elemental abundances. Hence, photospheric abundance analyses were carried out for four known HdC stars: HD 182040, HD 173409, HD 175893, and HD 137613. We have used high-resolution optical spectra obtained with the Hanle Echelle Spectrograph (HESP) mounted on the 2-m Himalayan Chandra Telescope (HCT) at Hanle, and the fiber-fed, cross-dispersed echelle spectrograph mounted on the 2.34-m Vainu Bappu Telescope (VBT) at Kavalur. Here we present our preliminary results from this analysis involving identification of about 2,800 spectral lines and the derived abundances of key elements such as C, N, and O, as well as light s-process (Sr, Y, Zr) and heavy s-process (Ba, La, Nd, Ce) elements. |
