Ancient Chinese, Korean, and Vietnamese observers left us records of celestial sightings, the so‐called “guest stars” dated up to ∼2500 years ago. Their identification with modern observable targets could open interesting insights into the long‐term behavior of astronomical objects, as shown by the successful identification of eight galactic supernovae. Here, we evaluate the possibility to identify ancient classical novae with presently known cataclysmic variables (CVs). For this purpose, we have developed a method which reconsiders in detail positions and sizes of ancient asterisms, in order to define areas on the sky that should be used for a search of modern counterparts. These areas range from a few to several 100 square degrees, depending on the details given in ancient texts; they should replace the single coordinate values given by previous authors. Any appropriate target (CVs, X‐ray binaries etc.) within these areas can be considered as a valid candidate for identification with the corresponding ancient event. Based on the original descriptions of several 100 old events, we selected those without movement and without a tail (to exclude comets) and which was not only visible within a certain hour (to exclude meteors). This way, we present a shortlist of 24 most promising events which could refer to classical nova eruptions. Our method is checked by applying it to the known SN identifications, leading to a margin of error between 0 and 4.5 degrees, meaning that some SN remnants lay exactly inside the areas given by the historical reports while in some other cases they are laying at considerable distances.

More than 100 guest star observations have been obtained by Chinese, Korean, Japanese, and Vietnamese astronomers between ∼600 BCE and ∼1690 CE. Comparing the coordinates from the information given in old texts for eight supernova recoveries with modern supernova remnant positions, we estimate the typical positional accuracy of the order of 0.3–7° for these supernovae. These values could also be a start for the expected deviation angle between a classical nova observed as a guest star and its modern counterpart among known cataclysmic variables (CVs). However, there are considerable disagreements among modern authors regarding the interpretation of ancient Far Eastern texts, emphasizing the need to consult the original historic sources again in order to improve the positioning reliability. We also discuss the typical amplitudes of well‐observed classical novae and find that modern counterparts of nova guest stars should be V = 18 mag and thus easily observable. In this context, we also consider the “hibernation scenario” and conclude that it is impossible to decide from currently available observations whether hibernation is common. In addition to the limiting magnitude of around 2 mag for ancient guest star detections mentioned in the literature, we consider the possibility that fainter guest stars (4–5 mag) could also have been detected by ancient observers and provide arguments in favor of this possibility. For these limits, we compare the expected nova detection rate of ancient naked‐eye observers with that during modern times and conclude that they coincide in order of magnitude, which implies that, indeed, a considerable number of classical nova remnants should be hidden among the Far Eastern guest star reports. Finally, we present a statistical analysis of the probability of casual misidentifications based on frequency and Galactic distribution of CVs in the AAVSO‐Variable Star indeX catalog.

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Recently, there have been several studies on the evolution of binary systems using historical data treated as facts in the chain of arguments. In this paper we discuss six case studies of modern dwarf novae with suggested historical counterpart from the historical point of view as well as the derived consequences for the physics of close binary systems (the dwarf novae Z Cam and AT Cnc, the nebula in M22, and the possible Nova 101, Nova 483, and Nova 1437). We consider the historical Far Eastern reports and after a careful re-reading of the text we map the given information on the sky. In some cases, the positions given in modern lists of classical nova-guest star-pairs turn out to be wrong, or they have to be considered highly approximate: The historical position, in most cases, should be transformed into areas at the celestial sphere and not into point coordinates. Based on the correct information we consider the consequences concerning the evolution of close binary systems. However, the result is that none of the cases of cataclysmic variables suggested to have a historical counterpart can be (fully) supported. As the identification of the historical record of observation with the CVs known today turns out to be always uncertain, a potential historical observation alone may not be relied on to draw conclusions on the evolution of binaries. The evolution scenarios should be derived from astrophysical observation and modelling only.

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