2026ApJ..1000..125S

FQ Cir was an ordinary fast He/N classical nova, peaking at V = 10.9. The pre-eruption and post-eruption counterpart was at V = 14.0, making this the smallest known classical nova amplitude, 3.1 mag. The nova light and the counterpart coincide at 0$\mathop{.}\limits^{\unicode{x02033}}$034, and the counterpart is a rare hot/blue emission-line star with flickering, so the identification of the quiescent nova is certain. The counterpart is a weak Be main-sequence star, B1 V(n)(e). A coherent photometric period appears in all four TESS Sectors and in the AAVSO post-eruption light curve, as ellipsoidal modulation with an orbital period of 2.041738 days. The companion must have been spun up to a fast rotation, and like all Be stars, a decretion disk is exuded. With the constraints of the blackbody radius and the main sequence, the companion mass is 13.0${}_{-0.5}^{+0.2}$M_⊙, with radius 6.2 ± 0.2 R_⊙. This is the discovery of a cataclysmic variable with a high-mass companion, a new class that we call “high-mass cataclysmic variables.” The white dwarf mass is 1.25 ± 0.10 M_⊙ and must have an accretion disk that supplies fuel for the nova eruption. FQ Cir represents a new mode of accretion in interacting binaries, with Roche lobe overflow from the decretion disk feeding mass into the usual accretion disk around the white dwarf, for disk-to-disk accretion. From the mass budget of the binary, the primary star must have its initial mass be >7.7 M_⊙, forming an ONe white dwarf, so FQ Cir can never become a Type Ia supernova.