rates of short GRBs and compact mergers are highly uncertain, possibly very low (see HN13).

A radioactively powered optical (or near infrared) transient is expected (so-called kilo-nova) from compact mergers $M_{\rm V} = -15$ mag at peak (Metzger & Berger 2012; Piran, Nakar, Rosswog 2013; Grossman et al. 2014). This corresponds to $m_{\rm V} = -10$ mag at 0.1 kpc, $-5$ mag at 1 kpc, $-2$ mag at 4 kpc (or $m_{\rm V} =-0.2$ mag for 9 kpc), all values for negligible absorption (otherwise fainter). Hence, it may have been observable by naked eye, but only for a short duration between a few hours and a few days (Metzger & Berger 2012; Piran, Nakar, Rosswog 2013; Grossman et al. 2014), i.e. much shorter than a typical SN or nova. An extra-galactic kilo-nova may once have been observed after the short Gamma-ray burst GRB 130603 B (Tanvir et al. 2013).

This motivated us to search for reports in old chronicles about an unusual transient celestial event. Given that European and eastern Asian (Chinese, Korean, and Japanese) chronicles on astronomical events, even for the 8th century, were fully studied before (see e.g. Stephenson & Green 2002 and references therein), we concentrated on 