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V392 Persei is a known dwarf nova (DN) that underwent a classical nova eruption in 2018. Here we report ground-based optical, Swift UV and X-ray, and Fermi -LAT γ-ray observations following the eruption for almost three years. V392 Per is one of the fastest evolving novae yet observed, with a t 2 decline time of 2 d. Early spectra present evidence for multiple and interacting mass ejections, with the associated shocks driving both the γ-ray and early optical luminosity. V392 Per entered Sun-constraint within days of eruption. Upon exit, the nova had evolved to the nebular phase, and we saw the tail of the supersoft X-ray phase. Subsequent optical emission captured the fading ejecta alongside a persistent narrow line emission spectrum from the accretion disc. Ongoing hard X-ray emission is characteristic of a standing accretion shock in an intermediate polar. Analysis of the optical data reveals an orbital period of 3.230 ± 0.003 d, but we see no evidence for a white dwarf (WD) spin period. The optical and X-ray data suggest a high mass WD, the pre-nova spectral energy distribution (SED) indicates an evolved donor, and the post-nova SED points to a high mass accretion rate. Following eruption, the system has remained in a nova-like high mass transfer state, rather than returning to the pre-nova DN low mass transfer configuration. We suggest that this high state is driven by irradiation of the donor by the nova eruption. In many ways, V392 Per shows similarity to the well-studied nova and DN GK Persei. [ABSTRACT FROM AUTHOR]

We report on the masses (M WD), effective temperatures (⁠|$\rm{T_\mathrm{eff}}$|⁠), and secular mean accretion rates (⁠|$\langle \dot{M} \rangle$|⁠) of 43 cataclysmic variable (CV) white dwarfs, 42 of which were obtained from the combined analysis of their Hubble Space Telescope ultraviolet data with the parallaxes provided by the Early Third Data Release of the Gaia space mission, and one from the white dwarf gravitational redshift. Our results double the number of CV white dwarfs with an accurate mass measurement, bringing the total census to 89 systems. From the study of the mass distribution, we derive |$\langle M_\mathrm{WD} \rangle = 0.81^{+0.16}_{-0.20}\, \mathrm{M_\odot }$|⁠ , in perfect agreement with previous results, and find no evidence of any evolution of the mass with orbital period. Moreover, we identify five systems with M WD < 0.5 M⊙, which are most likely representative of helium-core white dwarfs, showing that these CVs are present in the overall population. We reveal the presence of an anticorrelation between the average accretion rates and the white dwarf masses for the systems below the |$2\!-\!3\,$| h period gap. Since |$\langle \dot{M} \rangle$| reflects the rate of system angular momentum loss, this correlation suggests the presence of an additional mechanism of angular momentum loss that is more efficient at low white dwarf masses. This is the fundamental concept of the recently proposed empirical prescription of consequential angular momentum loss (eCAML) and our results provide observational support for it, although we also highlight how its current recipe needs to be refined to better reproduce the observed scatter in |$\rm{T_\mathrm{eff}}$| and |$\langle \dot{M} \rangle$|⁠ , and the presence of helium-core white dwarfs. [ABSTRACT FROM AUTHOR]

We present HST spectroscopy for 45 cataclysmic variables (CVs), observed with HST/COS and HST/STIS. For 36 CVs, the white dwarf is recognisable through its broad Ly α absorption profile and we measure the white dwarf effective temperatures (Teff) by fitting the HST data assuming log g = 8.35, which corresponds to the average mass for CV white dwarfs (≃0.8M☉). Our results nearly double the number of CV white dwarfs with an accurate temperature measurement. We find that CVs above the period gap have, on average, higher temperatures (≺Teff≻ ≃ 23 000 K) and exhibit much more scatter compared to those below the gap (≺Teff≻ ≃ 15 000 K). While this behaviour broadly agrees with theoretical predictions, some discrepancies are present: (i) all our new measurements above the gap are characterized by lower temperatures (Teff ≃ 16 000-26 000 K) than predicted by the present-day CV population m≺odels (Teff ≃ 38 000-43 000 K); (ii) our results below the gap are not clustered in the predicted narrow track and exhibit in particular a relatively large spread near the period minimum, which may point to some shortcomings in the CV evolutionary models. Finally, in the standard model of CV evolution, reaching the minimum period, CVs are expected to evolve back towards longer periods with mean accretion rates Ṁ ≲ 2 × 10-11M☉ yr-1, corresponding to Teff ≲ 11 500 K. We do not unambiguously identify any such system in our survey, suggesting that this major component of the predicted CV population still remains elusive to observations. [ABSTRACT FROM AUTHOR]

ABSTRACT Variable Na i absorption lines have been reported in a number of Type Ia supernovae (SNeIa). The presence of this circumstellar material suggests that cataclysmic variables (CVs) with a giant donor star may be the progenitors of these SNeIa. We present echelle spectra of the CV QU Carinae which strengthen the connection between CVs of the V Sge class, the accretion wind evolution scenario, variable wind features, variable Na i absorption and SNeIa. This thread not only provides insight into the spectral peculiarities of QU Car, but also links SNeIa as a class with their parent systems. [ABSTRACT FROM AUTHOR]

We present new red/near-infrared spectra of the low-accretion-rate polar J204827.9+005008.9. Compared to 2004 spectra in the literature, our 2008 data show more structured emission-line profiles. All emission lines in our spectra have two components at most orbital phases. The stronger component has a sinusoidal velocity variation and is likely due to irradiation of the inner hemisphere of the secondary star by the white dwarf. Based on the appearance of the Hα Doppler tomogram, the weaker, larger amplitude, line component likely originates in a ballistic stream from the L1 point. J2048 is thought to be accreting via a wind from the secondary star, so the detection of velocity features consistent with the velocities of Roche lobe overflow is unexpected. It appears that J2048 was experiencing an interval of enhanced mass transfer during our observations. We briefly discuss scenarios that might lead to such a situation, such as changes in the chromospheric activity level on the secondary star. [ABSTRACT FROM AUTHOR]

Analysis of 15 yr of photometric monitoring of the asynchronous magnetic cataclysmic variable BY Cam leads to revised assignments of the periodicities in the system. The surprising stability of the 197.4-min period suggests that this is the orbital period. We confirm the 7.3-d beat period between the orbital period and the white dwarf spin period, and show that the observed periods of the orbit, spin and beat are consistent to within the errors. In earlier work, the 197.4-min period has been assigned to the sideband. Because of the observed stability of the 197.4-min period in our data, the synchronization time of BY Cam is >3500 yr (much larger than that in other asynchronous polars) if the earlier period assignments are adopted. We also suggest that ∼145-d periodicity seen in our data may be due to precession of the rotational pole of the white dwarf. [ABSTRACT FROM AUTHOR]