Are DY\,Persei stars cooler cousins of R Coronae Borealis stars?

TL;DR

This study compares the spectral features and isotopic ratios of DY Persei stars with R Coronae Borealis stars, suggesting a possible evolutionary connection between these classes based on their chemical signatures.

Contribution

First spectral analysis of low-resolution IR spectra of DY Persei stars, revealing potential similarities with RCB and HdC stars through isotopic ratios.

Findings

Some DY Persei stars share isotopic ratios with RCB/HdC stars.

Others show different isotopic signatures, indicating diversity within DY Persei stars.

Results support a possible evolutionary link between DY Persei and RCB/HdC stars.

Abstract

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 suspects 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 $^{12}$C/$^{13}$C and low $^{16}$O/$^{18}$O ratios are characteristic features of majority RCBs and HdCs. We have estimated $^{16}$O/$^{18}$O ratios of the programme stars from the relative strengths of the $^{12}$C$^{16}$O and $^{12}$C$^{18}$O molecular bands observed in $K$- band. Our preliminary analysis suggest that a quartet of the DY\,Per suspects along with DY\,Persei itself seems to show isotopic ratio strength consistent with the ones of RCB/HdC stars whereas two of them do not show significant $^{13}$C and $^{18}$O in their atmospheres. Our analysis provides further indications that DY\,Per type stars could be related to RCB/HdC class of stars.