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Abstract The recurrent nova T Pyxidis (T Pyx) has erupted six times since 1890, with its last outburst in 2011, and the relatively short recurrence time between classical nova explosions indicates that T Pyx must have a massive white dwarf (WD) accreting at a high rate. It is believed that, since its outburst in 1890, the mass transfer rate in T Pyx was very large due to a feedback loop where the secondary is heated by the hot WD. The feedback loop has been slowly shutting off, reducing the mass transfer rate, and thereby explaining the magnitude decline of T Pyx from ∼13.8 (before 1890) to 15.7 just before the 2011 eruption. We present an analysis of the latest Hubble Space Telescope far-ultraviolet and optical spectra, obtained 12 yr after the 2011 outburst, showing that the mass transfer rate has been steadily declining and is now below its preoutburst level by about 40%: $\dot{M}\sim 1-3\times {10}^{-7}{M}_{\odot }$yr⁻¹for a WD mass of ∼1.0–1.4M_⊙, an inclination of 50°–60°, reddening ofE(B−V) = 0.30 ± 0.05, and a Gaia Data Release 3 distance of ${2860}_{-471}^{+816}$pc. This steady decrease in the mass transfer rate in the ∼decade after the 2011 outburst is in sharp contrast with the more constant preoutburst ultraviolet continuum flux level from archival International Ultraviolet Explorer spectra. The flux (i.e., $\dot{M}$) decline rate is 29 times faster now in the last ∼decade than observed since 1890 to ∼2010. The feedback loop shut off seems to be accelerating, at least in the decade following its 2011 outburst. In all eventualities, our analysis confirms that T Pyx is going through an unusually peculiar short-lived phase. 

ABSTRACT V745 Sco is a Galactic symbiotic recurrent nova with nova eruptions in 1937, 1989, and 2014. We study the behaviour of V745 Sco at radio wavelengths (0.6–37 GHz), covering both its 1989 and 2014 eruptions and informed by optical, X-ray, and $$\gamma$$-ray data. The radio light curves are synchrotron-dominated. Surprisingly, compared to expectations for synchrotron emission from explosive transients such as radio supernovae, the light curves spanning 0.6–37 GHz all peak around the same time ($$\sim$$18–26 d after eruption) and with similar flux densities (5–9 mJy). We model the synchrotron light curves as interaction of the nova ejecta with the red giant wind, but find that simple spherically symmetric models with wind-like circumstellar material (CSM) cannot explain the radio light curve. Instead, we conclude that the shock suddenly breaks out of a dense CSM absorbing screen around 20 d after eruption, and then expands into a relatively low-density wind ($$\dot{M}_{out} \approx 10^{-9}\!-\!10^{-8}$$ M$$_{\odot }$$ yr$$^{-1}$$ for $$v_w = 10$$ km s$$^{-1}$$) out to $$\sim$$1 yr post-eruption. The dense, close-in CSM may be an equatorial density enhancement or a more spherical red giant wind with $$\dot{M}_{in} \approx [5\!-\!10] \times 10^{-7}$$ M$$_{\odot }$$ yr$$^{-1}$$, truncated beyond several $$\times 10^{14}$$ cm. The outer lower-density CSM would not be visible in typical radio observations of Type Ia supernovae: V745 Sco cannot be ruled out as a Type Ia progenitor based on CSM constraints alone. Complementary constraints from the free–free radio optical depth and the synchrotron luminosity imply the shock is efficient at accelerating relativistic electrons and amplifying magnetic fields, with $$\epsilon _e$$ and $$\epsilon _B \approx 0.01\!-\!0.1$$.