Are DY Persei Stars Cooler Cousins of R Coronae Borealis Stars?

Abstract

Are DY Persei Stars Cooler Cousins of R Coronae Borealis Stars? Anirban Bhowmick 1 , Gajendra Pandey 1 , Vishal Joshi 2 , and N. M. Ashok 2 1 Indian Institute of Astrophysics, Koramangala, Bengaluru 560 034, India; anirban@iiap.res.in , pandey@iiap.res.in 2 Physical Research Laboratory, Ahmedabad 380009, India; vjoshi@prl.res.in , ashok@prl.res.in Received 2017 December 5; revised 2018 January 24; accepted 2018 January 24; published 2018 February 21 Abstract In this paper we present, for the fi rst time, the study of low resolution H - and K -band spectra of 7 DY Per type and suspect stars, as well as DY Persei itself. We also observed H - and K -band spectra of 3 R Coronae Borealis ( RCB ) stars, 1 hydrogen-de fi cient carbon ( HdC ) star, and 14 cool carbon stars, including normal giants as comparisons. High 12 C / 13 Candlow 16 O / 18 O ratios are characteristic featur es of majority RCBs and HdCs. We have estimated 16 O / 18 O ratios of the program stars from the relative strengths of the 12 C 16 Oand 12 C 18 Omolecular bands observed in K -band. Our preliminary analysis suggests that a quartet of the DY Per suspects, along with DY Persei itself, seem to show isotopic rat io strength consistent with that of RCB / HdC stars, whereas two of them do not show signi fi cant 13 Cand 18 O in their atmospheres. Our analysi s provides further indications that DY Per type stars could be related to the RCB / HdC class of stars.