SIMBAD references

In this paper we present, for the first 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-deficient carbon (HdC) star, and 14 cool carbon stars, including normal giants as comparisons. High ¹²C/¹³C and low ¹⁶O/¹⁸O ratios are characteristic features of majority RCBs and HdCs. We have estimated ¹⁶O/¹⁸O ratios of the program stars from the relative strengths of the ¹²C¹⁶O and ¹²C¹⁸O molecular 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 ratio strength consistent with that of RCB/HdC stars, whereas two of them do not show significant ¹³C and ¹⁸O in their atmospheres. Our analysis provides further indications that DY Per type stars could be related to the RCB/HdC class of stars.