| Name: Anirban Bhowmick |
| Affiliation: Manipal Institute of Natural Sciences |
| Conference ID: ASI2026_826 |
| Title: A medium resolution spectroscopic survey to detect northern dLHdC candidates |
| Abstract Type: Poster |
| Abstract Category: Stars, Interstellar Medium, and Astrochemistry in Milky Way |
| Author(s) and Co-Author(s) with Affiliation: Anirban Bhowmick(Manipal Centre for Natural Sciences, Manipal -576104, India), Gajendra Pandey(Indian Institute of Astrophysics, Bangalore - 560034, India), Bharat Kumar Yerra(Indian Institute of Astrophysics, Bangalore - 560034, India), Merina Dsoosa(Indian Institute of Astrophysics, Bangalore - 560034, India), Sunayna Maben(National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China), Sriram Krishna(Indian Institute of Astrophysics, Bangalore - 560034, India), Ajay Kumar Saini(Indian Institute of Astrophysics, Bangalore - 560034, India) |
| Abstract: Hydrogen-deficient carbon stars are a rare class of carbon-rich supergiants that cannot be explained by canonical single-star evolution due to their unique H-poor composition. Classified into two main observational groups- the dust-producing R Coronae Borealis variables (RCBs) and the dustless HdCs (dLHdCs), they exhibit peculiar abundance patterns: depletion of 13C relative to 12C (Hema et al. 2012) and extreme 18O enrichment relative to 16O (Clayton et al. 2007) compared to H-normal stars. Being extremely rare, the discovery rate of these two categories has historically been contrasting: large-scale photometric surveys have added many new RCBs because their dramatic, irregular dust-decline light curves are easily flagged (Tisserand et al. 2013; Shields et al. 2019). In contrast, for decades, the dLHdC population remained extremely limited with only five confirmed objects, due to their uncharacteristic light curves and weak photometric variability (Geballe et al. 2009). This status changed with the breakthrough Gaia eDR3 study of Tisserand et al. (2022), who confirmed 27 new dLHdCs through spectroscopic follow-up of Gaia-selected candidates, opening the first statistically meaningful view of the class. However, their results were limited to the southern sky, with no systematic counterpart survey having been conducted in the north. To address this, we have initiated a spectroscopic survey of northern HdC candidates using TANSPEC, a medium-resolution (R~2750) spectrograph on the 3.6m Devasthal Optical Telescope (DOT). TANSPEC, with its optical to near-IR coverage, provides a unique opportunity to simultaneously investigate the H-line diagnostics (from the optical) as well as the 12C/13C and 16O/18O (from the near-IR K spectrum). In this study, we present the first results on the promising potential northern dLHdC candidates.
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