We present the results of an expanded, long-term radial velocity search (25 yrs) for evidence of binarity in a sample of seven bright proto-planetary nebulae (PPNe). The goal is to investigate the widely-held view that the bipolar or point-symmetric shapes of planetary nebulae (PNe) and PPNe are due to binary interactions. Observations from three observatories were combined from 2007−2015 to search for variations on the order of a few years and then combined with earlier observations from 1991−1995 to search for variations on the order of decades. All seven show velocity variations due to periodic pulsation in the range of 35−135 days. However, in only one PPN, IRAS 22272+5435, did we find even marginal evidence found for multi-year variations that might be due to a binary companion. This object shows marginally-significant evidence of a twoyear period of low semi-amplitude which could be due to a low-mass companion, and it also displays some evidence of a much longer period of >30 years. The absence of evidence in the other six objects for long-period radial velocity variations due to a binary companion sets significant constraints on the properties of

Context. Hundreds of candidate hybrid pulsators of intermediate type A-F were revealed by the recent space missions. Hybrid pulsators allow to study the full stellar interiors, where both low-order p-and high-order g-modes are simultaneously excited. The true hybrid stars must be identified since other processes, related to stellar multiplicity or rotation, might explain the presence of (some) low frequencies observed in their periodograms. Aims. We measured the radial velocities of 50 candidate δ Scuti -γ Doradus hybrid stars from the Kepler mission with the Hermes and Ace spectrographs over a time span of months to years. We aim to derive the fraction of binary and multiple systems and to provide an independent and homogeneous determination of the atmospheric properties and v sin i for all targets. The long(er)-term objective is to identify the (probable) physical cause of the low frequencies.Methods. We computed 1-D cross-correlation functions (CCFs) in order to find the best set of parameters in terms of the number of components, spectral type(s) and v sin i for each target. Radial velocities were measured from spectrum synthesis and by using a 2-D cross-correlation technique in the case of double-and triple-lined systems. Fundamental parameters were determined by fitting (composite) synthetic spectra to the normalised median spectra corrected for the appropriate Doppler shifts. Results. We report on the analysis of 478 high-resolution Hermes and 41 Ace spectra of A/F-type candidate hybrid pulsators from the Kepler field. We determined their radial velocities, projected rotational velocities, atmospheric properties and classified our targets based on the shape of the CCFs and the temporal behaviour of the radial velocities. We derived orbital solutions for seven new systems. Three long-period preliminary orbital solutions are confirmed by a photometric time-delay analysis. Finally, we determined a global multiplicity fraction of 27% in our sample of candidate hybrid stars.Section 2 describes the target selection, the observational strategy, the campaigns and the observations. Section 3 deals with the data processing. In Section 4, we explain the methodology and the data analysis. In Sections 5 and 7, the results of the classification and the orbital solutions of the newly discovered systems, respectively, are presented. The extraction of the physical parameters is discussed in Section 6. In Sect. 8, we study the periodograms based on the Kepler data and we present an observational H-R diagram in Sect. 9. A discussion and conclusions from this work are provided in Section 10.

We have obtained contemporaneous light, color, and radial velocity data for three proto-planetary nebulae (PPNe) over the years 2007 to 2015. The light and velocity curves of each show similar periods of pulsation, with photometric periods of 42 and 50 days for IRAS 17436+5003, 102 days for IRAS 18095+2704, and 35 days for IRAS 19475+3119. The light and velocity curves are complex with multiple periods and small, variable amplitudes. Nevertheless, at least over limited time intervals, we were able to identify dominant periods in the light, color, and velocity curves and compare the phasing of each. The color curves appear to peak with or slightly after the light curves while the radial velocity curves peak about a quarter of a cycle before the light curves. Similar results were found previously for two other PPNe, although for them the light and color appeared to be in phase. Thus, it appears that PPNe are brightest when smallest and hottest. These phase results differ from those found for classical Cepheid variables, where the light and velocity differ by half a cycle, and are hottest at about average size and expanding. However, they do appear to have similar phasing to the larger-amplitude pulsations seen in RV Tauri variables. Presently, few pulsation models exist for PPNe, and these do not fit the observations well, especially the longer periods observed. Model fits to these new light and velocity curves would allow masses to be determined for these post-AGB objects, and thereby provide important constraints to post-AGB stellar evolution models of low-and intermediate-mass stars.

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The planetary nebula (PN) NGC 3132 is a striking example of the dramatic but poorly understood mass-loss phenomena that (1–8) M ⊙ stars undergo during their death throes as they evolve into white dwarfs (WDs). From an analysis of JWST multiwavelength (0.9–18 μm) imaging of NGC 3132, we report the discovery of an extended dust cloud around the WD central star (CS) of NGC 3132, seen most prominently in the 18 μm image, with a surface-brightness-limited radial extent of ≳2″. We show that the A2V star located 1.″7 to CS’s northeast (and 0.75 kpc from Earth) is gravitationally bound to the latter, as evidenced by the detection of relative orbital angular motion of 0.°24 ± 0.°045 between these stars over ∼20 yr. Using aperture photometry of the CS extracted from the JWST images, together with published optical photometry and an archival UV spectrum, we have constructed the spectral energy distribution (SED) of the CS and its extended emission over the UV to mid-IR (0.091–18 μm) range. We find that fitting the SED of the CS and the radial intensity distributions at 7.7, 12.8, and 18 μm with thermal emission from dust requires a cloud that extends to a radius of ≳1785 au, with a dust mass of ∼1.3 × 10−2 M ⊕ and grains that are 70% silicate and 30% amorphous carbon. We propose plausible origins of the dust cloud and an evolutionary scenario in which a system of three stars—the CS, a close low-mass companion, and a more distant A2V star—forms a stable hierarchical triple system on the main sequence but becomes dynamically unstable later, resulting in the spectacular mass ejections that form the current, multipolar PN.