1 Introduction

KT Mon (Nova Mon 1942) was discovered by A. N. Vyssotsky on a Harvard plate taken on 1943 January 2. The object was first recorded at $m_{\rm pg} = 10.3$ on 1942 December 30. Gaposchkin (1954) presented a light curve and a description of a spectrum taken by Vyssotsky on the discovery plate. According to Gaposchkin (1954), the object rather rapidly faded (2 mag in 27 d). The object was fainter than $m_{\rm pg} = 13.35$, 13.9 d prior to the first positive record on 1942 December 30. Gaposchkin (1954) described the low-resolution spectrum by Vyssotsky as "broad bright lines H$\beta$, H$\gamma$, H$\delta$, 4686 HeII and 4640 NIII". From these findings, Gaposchkin (1954) concluded that KT Mon is a nova. Duerbeck (1987) classified the object as an established moderately fast nova.

However, several authors have noted the peculiarity of KT Mon. Payne-Gaposchkin (1977) deduced the distances of past novae, and found three stars (KT Mon, CG CMa and WX Cet) are more than 15 kpc distant from the Galactic Center. The two objects in this list, CG CMa (Kato et al. 1999; Duerbeck et al. 1999) and WX Cet (Bailey 1979; O'Donoghue et al. 1991; Kato et al. 2001) are now established to be SU UMa-type dwarf novae (For a recent review of dwarf novae and SU UMa-type dwarf novae, see Osaki 1996 and Warner 1995, respectively.) Regarding KT Mon, Payne-Gaposchkin (1977) described that "KT Mon: whose spectrum observed by Vyssotsky, and whose light curve obtained by Gaposchkin (1954) place it unequivocally as a nova" and suggested that "further study might find KT Mon to be recurrent" based on this unusual distance estimate. Similar long-distance estimates have been given in Warner (1987); Shafter (1997). No quiescent counterpart has been reported down to mag 20 (Duerbeck 1987).