Cataclysmic variables as possible counterparts of ancient Far Eastern guest stars

Abstract

ABSTRACT Continuing our efforts to select possible classical nova candidates among Far Eastern guest stars and to identify them with modern cataclysmic variables (CVs), we present a search for counterparts in 24 promising areas of the sky corresponding to ancient observations between 204 bce and 1690 ce. These areas were derived by us in a previous paper. Based on the physical entities of the CVs in our areas and reasonable magnitude limits compatible with the distribution of known eruption amplitudes of telescopic classical novae, we present a catalogue of a total of 80 CVs and related targets that could possibly have caused the historical sightings. This list could potentially be reduced by additionally discussing further information such as brightness or duration. In some cases, we present a detailed discussion of the interpretation of ancient sources comparing them with properties of the brightest CVs in the field. In order to estimate whether this list is representative, we discuss the distribution of CV types in our catalogue of counterparts for the historical events. Compared to the entire sky, the surface densities of most CV subtypes in our search fields reveal similar values, except for polars and intermediate polars, i.e. strongly magnetic CVs, for which a significant excess in our search fields was detected. Finally, we give an outlook towards future research in this topic, and provide in the online supplementary information a complete atlas of the celestial maps of all 24 guest star events, displaying the search areas and locations of CVs within them.