A unified theory of cataclysmic variable evolution from feedback-dominated numerical simulations

The envelopes accreted by white dwarf stars from their hydrogen-rich companions¹ experience thermonuclear-powered runaways^2,3 observed as classical nova eruptions^4,5 peaking at 10⁵-10⁶ solar luminosities^6-9. Virtually all nova progenitors—`nova-like variables'—exhibit high mass transfer rates to their white dwarfs before and after an eruption<sup>10</sup>. Surprisingly, 10-1,000 times lower mass transfer rate<sup>11</sup> binaries, exhibiting accretion-powered `dwarf nova' outbursts¹², exist at identical orbital periods. Nova shells surrounding dwarf novae^13-16 demonstrate that at least some novae metamorphize into dwarf novae^17,18, though the mechanisms and timescales governing mass transfer rate variations are poorly understood. Here, we report simulations of the multi-Gyr evolution of novae modelling every eruption's thermonuclear runaway, mass and angular momentum losses, feedback due to irradiation and variable mass transfer rate, and orbital size and period changes. These feedback-dominated simulations reproduce the observed range of mass transfer rates at a given orbital period, with large and cyclic kyr-Myr timescale changes. They also demonstrate Myr-long deep hibernation (complete stoppage of mass transfer), but only in short-period binaries; that initially different binaries converge to become nearly identical systems; low-mass-transfer-rate dwarf novae occasionally generate novae; and that the masses of white dwarfs decrease monotonically, but only slightly while their red dwarf companions are consumed.