We report the discovery and analysis of 36 new eclipsing EL CVn-type binaries, consisting of a core helium-composition pre-white dwarf and an early-type main-sequence companion, more than doubling the known population of these systems. We have used supervised machine learning methods to search 0.8 million lightcurves from the Palomar Transient Factory, combined with SDSS, Pan-STARRS and 2MASS colours. The new systems range in orbital periods from 0.46 to 3.8 d and in apparent brightness from ∼14 to 16 mag in the PTF R or g filters. For twelve of the systems, we obtained radial velocity curves with the Intermediate Dispersion Spectrograph at the Isaac Newton Telescope. We modelled the lightcurves, radial velocity curves and spectral energy distributions to determine the system parameters. The radii (0.3-0.7 R ) and effective temperatures (8000-17000 K) of the pre-He-WDs are consistent with stellar evolution models, but the masses (0.12-0.28 M ) show more variance than models have predicted. This study shows that using machine learning techniques on large synoptic survey data is a powerful way to discover substantial samples of binary systems in short-lived evolutionary stages.

We present an extensive Doppler tomography study of the eclipsing novalike EC21178-5417, which exhibits the classic accretion disc signature in the form of double-peak emission lines in its spectrum. Doppler tomograms confirm the presence of a strong, two-armed spiral pattern visible in the majority of the spectral lines studied. This makes EC21178-5417 one of the very few novalikes that show spiral structure in their discs. We also report night-to-night changes in the position and relative strength of the spiral arms, revealing fluctuations on the conditions in the accretion disc.

Spiral density waves are thought to be excited in the accretion discs of accreting compact objects, including Cataclysmic Variable stars (CVs). Observational evidence has been obtained for a handful of systems in outburst over the last two decades. We present the results of a systematic study searching for spiral density waves in CVs, and report their detection in two of the sixteen observed systems. While most of the systems observed present asymmetric, non-Keplerian accretion discs during outburst, the presence of ordered structures interpreted as spiral density waves is not as ubiquitous as previously anticipated. From a comparison of systems by their system parameters it appears that inclination of the systems may play a major role, favouring the visibility and/or detection of spiral waves in systems seen at high inclination.

Context. The study of radio emission from core-collapse supernovae (SNe) probes the interaction of the ejecta with the circumstellar medium (CSM) and reveals details of the mass-loss history of the progenitor. Aims. We report observations of the type IIP supernova SN 2016X during the plateau phase, at ages between 21 and 75 days, obtained with the Karl G. Jansky Very Large Array (VLA) radio observatory. Methods. We modelled the radio spectra as self-absorbed synchrotron emission, and we characterised the shockwave and the mass-loss rate of the progenitor. We also combined our results with previously reported X-ray observations to verify the energy equipartition assumption. Results. The properties of the shockwave are comparable to other type IIP supernovae. The shockwave expands according to a self-similar law R ∝ tm with m = 0.76 ± 0.08, which is notably different from a constant expansion. The corresponding shock velocities are approximately 10700–8000 km s−1 during the time of our observations. The constant mass-loss rate of the progenitor is Ṁ = (7.8 ± 0.9) × 10−7 α−8/19 (ϵB/0.1)−1 M⊙ yr−1, for an assumed wind velocity of 10 km s−1. We observe spectral steepening in the optically thin regime at the earlier epochs, and we demonstrate that it is caused by electron cooling via the inverse Compton effect. We show that the shockwave is characterised by a moderate deviation from energy equipartition by a factor of ϵe/ϵB ≈ 28, being the second type IIP supernova to show such a feature.