| Author(s) and Co-Author(s) with Affiliation: Akash P(Department of Physics, University of Calicut, Malappuram - 673635, India), Drisya Karinkuzhi(Department of Physics, University of Calicut, Malappuram - 673635, India) |
| Abstract: C-J type carbon stars form a chemically peculiar subclass of carbon stars, characterized by low ¹²C/¹³C ratios, lithium enrichment, and a lack of s-process enhancement. While their chemical properties have been studied in detail in earlier works, their photometric variability has received comparatively little attention. Since variability in evolved stars is closely linked to pulsation, mass loss, and evolutionary state, it provides an independent and powerful diagnostic of their physical and chemical nature.
In this work, we investigate the variability properties of a sample of C-J type carbon stars selected from the LAMOST DR4 catalogue using multi-epoch photometric data from ASAS-3, ASAS-SN, KWS, ZTF, and Gaia. We extract and homogenize the light curves, determine periods and amplitudes using Lomb–Scargle and related time-series analysis techniques, and classify the variability types. In color–color (e.g., JHK) and Hertzsprung–Russell diagrams, C-J and normal N-type carbon stars occupy similar regions. Therefore, in addition to their distinct chemical properties, we examine whether these subclasses also differ in their variability behavior. The derived variability properties are systematically compared with those of other carbon-star subclasses, in particular N-type stars.
The aim of this analysis is to test whether C-J type stars occupy distinct regions in period–luminosity space compared to other carbon-star subclasses and whether their pulsation behavior differs from that of classical thermally pulsing AGB carbon stars. If there is such a distinction, it would support the idea that C-J type stars may follow a different evolutionary pathway, potentially involving non-standard internal mixing or binary interaction. We will present our results and discuss how time-domain information can provide an important and complementary constraint on the evolutionary status of chemically peculiar carbon stars and offer new insight into the origin of the C-J subclass within the broader carbon-star population. |
