‘Novae, supernovae, or something else?’ – (super-)nova highlights from Hoffmann & Vogt are quite certainly comets (ad 668 and 891)

Abstract

Galactic novae and supernovae can be studied by utilizing historical observations, yielding explosion time, location on sky etc. Recent publications by Hoffmann & Vogt present CVs, supernova remnants, planetary nebulae etc. as potential counterparts based on their list of historically reported transients from the Classical Chinese text corpus. Since their candidate selection neglects the state-of-the-art (e.g. Stephenson & Green), and since it includes ‘broom stars’ and ‘fuzzy stars’, i.e. probable comets, we investigate their catalogue in more detail. We discuss here their two highlights, the suggestion of two ‘broom star’ records dated AD 667 and 668 as one historical supernova and of the ‘guest star’ of AD 891 as recurrent nova U Sco. The proposed positional search areas are not justified due to translation and dating problems, source omission, as well as misunderstandings of historical Chinese astronomy and unfounded textual interpretations. All sources together provide strong evidence for comet sightings in both AD 668 and 891 – e.g., there are no arguments for stationarity. The AD 667 record is a misdated doublet of 668. Our critique pertains more generally to their whole catalogue of ‘24 most promising events’: their speculations on counterparts lack a solid foundation and should not be used in follow-ups.

Critical comments on publications by S. Hoffmann and N. Vogt on historical novae/supernovae and their candidates

“…Stephenson and Green ( 2009) have ∼50, while Hsi (1957aHsi ( , 1957b, Ho (1962), Stephenson (1976), Clark and Stephenson (1977), and Xu et al (2000) list up to ∼100 for about the same time span-and they all include some comets and other non-novae (see e.g. AD 891, Neuhäuser et al 2021a).…”

“…In sum, the terms "hui xing" and "xing bo" are not qualified to indicate star-like objects. In P4, we can read "we neglect wording and consider only reports of long tails with a clear direction as definitely indicating comets" (section 1)-there are not many comet records, where both tail length and tail direction were mentioned, but there are much more records of "hui xing" and "xing bo" objects, which clearly indicate comets (not only 1P/Halley), see, for example, the comet of AD 891 (Neuhäuser et al 2021a).…”

“…AD 668 and 891 in Neuhäuser et al 2021a), 19 • consider the context, for example, other historical events (politics, weather, etc. ) and possibly the astro-omenological interpretation (but not done in P3), for examples, see the comets of AD 668 and 891 (Neuhäuser et al 2021a),…”

“…• Their alleged new historical SN of AD 667-8 (one of the three "highlights" in P3-P5) was a comet observed in AD 668 for 19 nights according to Ho (1962), Xu et al (2000), and Pankenier et al (2008), see Neuhäuser et al (2021a)-the AD 667 record is just a misdated copy.…”

“…• The single Japanese record of AD 891 misinterpreted as recurrent nova U Sco in AD 891 in P3-P5 (another "highlight") obviously belongs to several reports of a comet seen also in China, Arabia, and Europe (Kronk 1999;Neuhäuser et al 2021a).…”