We present results from the first two quarters of a survey to search for pulsations in compact stellar objects with the Kepler spacecraft. The survey

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We present time-resolved optical spectroscopy of V458 Vulpeculae (Nova Vul 2007 No. 1) spread over a period of 15 months starting 301 d after its discovery. Our data reveal radial-velocity variations in the He iiλ5412 and He iiλ4686 emission lines. A period analysis of the radial-velocity curves resulted in a period of 98.096 47 ± 0.000 25 min (0.068 122 55 ± 0.000 000 17 d) which we identify with the orbital period of the binary system. V458 Vul is therefore the planetary nebula central binary star with the shortest period known. We explore the possibility of the system being composed of a relatively massive white dwarf (M1 ≳ 1.0 M⊙) accreting matter from a post-asymptotic giant branch star which produced the planetary nebula observed. In this scenario, the central binary system therefore underwent two common-envelope episodes. A combination of previous photoionization modelling of the nebular spectra, post-asymptotic giant branch evolutionary tracks and the orbital period favour a mass of M2 ∼ 0.6 M⊙ for the donor star. Therefore, the total mass of the system may exceed the Chandrasekhar mass, which makes V458 Vul a Type Ia supernova progenitor candidate.

While analysing the images of the IPHAS (INT/WFC Photometric Hα Survey of the northern Galactic plane) survey, we noticed that the central star of the candidate planetary nebula IPHASXJ211420.0+434136 (also named Ou5) was clearly variable. This is generally considered as an indication of binarity. To confirm it, we performed a photometric monitoring of the central star, and obtained images and spectra of the nebula. The nebular spectrum confirms that IPHASXJ211420.0+434136 is a planetary nebula of moderately high excitation. It has a remarkable morphology with two nested pairs of bipolar lobes and other unusual features. The light curve of the central star reveals that it is an eclipsing binary system with an orbital period of 8.74 h. It also displays a strong irradiation effect with an amplitude of 1.5 mag. The presence of multiple bipolar outflows adds constraints to the formation of these nebulae, suggesting the occurrence of discrete ejection events during, or immediately before, the common-envelope phase. IPHASXJ211420.0+434136 also adds evidence to the hypothesis that a significant fraction of planetary nebulae with close binary central stars have a peculiar nebular chemistry and a relatively low nebular mass. This may point to low-mass, low-metallicity progenitors, with additional effects related to the binary evolution. We also suggest that these objects may be relevant to understand the abundance discrepancy problem in planetary nebulae.