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In this letter, the results of our low-resolution spectroscopic survey foridentifying the hydrogen-deficient (H-deficient) stars in the red giant sampleof the globular cluster Omega Cen are reported. Spectral analyses were carriedout on the basis of the strengths of (0,0) MgH band and the Mg b triplet. Inour sample, four giants were identified with weak/absent MgH bands in theirobserved spectra not as expected for their well determined stellar parameters.The Mg abundances for the program stars were determined from subordinate linesof the MgH band to the blue of the Mg b triplet, using the spectral synthesistechnique. The derived Mg abundances for the program stars were as expected forthe red giants of Omega Cen (Norris & Da Costa 1995), except for the fouridentified candidates. Determined Mg abundances of these four candidates aremuch lower than that expected for the red giants of Omega Cen, and areunacceptable based on the strengths of Mg b triplet in their observed spectra.Hence, the plausible reason for the weak/absent MgH bands in the observedspectra of these stars is a relatively lower abundance of hydrogen in theiratmospheres. These giants may belong to the group of helium enriched red giantsof Omega Cen.

Discovery of relatively hydrogen-poor giants in the Galactic globular cluster Omega Centauri