TY - JOUR A1 - Neunteufel, Patrick A1 - Preece, H. A1 - Kruckow, Matthias U. A1 - Geier, Stephan A1 - Hamers, Adrian S. A1 - Justham, S. A1 - Podsiadlowski, Philipp T1 - Properties and applications of a predicted population of runaway He-sdO/B stars ejected from single degenerate He-donor SNe JF - Astronomy and astrophysics : an international weekly journal N2 - Context. Thermonuclear supernovae (SNe), a subset of which are the highly important SNe of Type Ia and Iax, are relatively poorly understood phenomena. One of the more promising scenarios leading up to the creation of a thermonuclear SN involves accretion of helium-rich material from a binary companion. Following the SN, the binary companion is then ejected from the location of the progenitor binary at velocities possibly large enough to unbind it from the gravitational potential of the Galaxy. Ejected companion stars should form a detectable population, if their production mechanism is not exceedingly rare. Aims. This study builds on previous works, producing the most extensive prediction of the properties of such a hypothetical population to date, taking both Chandrasekhar and non-Chandrasekhar mass events into account. These results are then used to define criteria for membership of this population and characterise putative subpopulations. Methods. This study contains 6 x 10(6) individual ejection trajectories out of the Galactic plane calculated with the stellar kinematics framework SHyRT, which are analysed with regard to their bulk observational properties. These are then put into context with the only previously identified population member US 708 and applied to a number of other possible candidate objects. Results. We find that two additional previously observed objects possess properties to warrant a designation as candidate objects. Characterisation of these object with respect to the predicted population finds all of them to be extreme in at least one astrometric observable. Higher mass ( >0 :7 M-circle dot) objects should be over-represented in the observationally accessible volume, with the ratio of bound to unbound objects being an accessible observable for the determination of the dominant terminal accretor mass. We find that current observations of runaway candidates within 10 kpc support a Galactic SN rate of the order of similar to 3 x 10(-7) yr(-1) to similar to 2 x 10(-6) yr(-1), three orders of magnitude below the inferred Galactic SN Ia rate and two orders of magnitude below the formation rate of predicted He-donor progenitors. Conclusions. The number of currently observed population members suggests that the He-donor scenario, as suspected before, is not a dominant contributor to the number of observed SNe Ia. However, even at the low event rate suggested, we find that the majority of possibly detectable population members is still undetected. The extreme nature of current population members suggests that a still larger number of objects has simply evaded detection up to this point, hinting at a higher contribution than is currently supported by observation. KW - binaries: close KW - stars: kinematics and dynamics KW - stars: distances KW - supernovae: general KW - subdwarfs KW - white dwarfs Y1 - 2022 U6 - https://doi.org/10.1051/0004-6361/202142864 SN - 0004-6361 SN - 1432-0746 VL - 663 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Hillwig, Todd C. A1 - Reindl, Nicole A1 - Rotter, Hannah M. A1 - Rengstorf, Adam W. A1 - Heber, Ulrich A1 - Irrgang, Andreas T1 - Two evolved close binary stars: GALEX J015054.4+310745 and the central star of the planetary nebula Hen 2-84 JF - Monthly notices of the Royal Astronomical Society N2 - As part of a survey to find close binary systems among central stars of planetary nebula, we present two newly discovered binary systems. GALEX J015054.4+310745 is identified as the central star of the possible planetary nebula Fr 2-22. We find it to be a single-lined spectroscopic binary with an orbital period of 0.2554435(10) d. We support the previous identification of GALEX J015054.4+310745 as an sdB star and provide physical parameters for the star from spectral modelling. We identify its undetected companion as a likely He white dwarf. Based on this information, we find it unlikely that Fr 2-22 is a true planetary nebula. In addition, the central star of the true planetary nebula Hen 2-84 is found to be a photometric variable, likely due to the irradiation of a cool companion. The system has an orbital period of 0.485645(30) d. We discuss limits on binary parameters based on the available light-curve data. Hen 2-84 is a strongly shaped bipolar planetary nebula, which we now add to the growing list of axially or point-symmetric planetary nebulae with a close binary central star. KW - binaries: close KW - stars: individual: GALEX J015054.4+310745 KW - subdwarfs KW - planetary nebulae: individual: Hen 2-84 Y1 - 2022 U6 - https://doi.org/10.1093/mnras/stac226 SN - 0035-8711 SN - 1365-2966 VL - 511 IS - 2 SP - 2033 EP - 2039 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Schaffenroth, Veronika A1 - Pelisoli, Ingrid A1 - Barlow, Brad N. A1 - Geier, Stephan A1 - Kupfer, Thomas T1 - Hot subdwarfs in close binaries observed from space I. BT - orbital, atmospheric, and absolute parameters and the nature of their companions JF - Astronomy and astrophysics : an international weekly journal N2 - Context: About a third of the hot subdwarfs of spectral type B (sdBs), which are mostly core-helium-burning objects on the extreme horizontal branch, are found in close binaries with cool, low-mass stellar, substellar, or white dwarf companions. They can show light variations due to di fferent phenomena. Aims: Many hot subdwarfs now have space-based light curves with a high signal-to-noise ratio available. We used light curves from the Transiting Exoplanet Survey Satellite and the K2 space mission to look for more sdB binaries. Their light curves can be used to study the hot subdwarf primaries and their companions, and obtained orbital, atmospheric, and absolute parameters for those systems, when combined with other analysis methods. Methods: By classifying the light variations and combining these with the fit of the spectral energy distribution, the distance derived by the parallaxes obtained by Gaia, and the atmospheric parameters, mainly from the literature, we could derive the nature of the primaries and secondaries in 122 (75%) of the known sdB binaries and 82 newly found reflection e ffect systems. We derived absolute masses, radii, and luminosities for a total of 39 hot subdwarfs with cool, low-mass companions, as well 29 known and newly found sdBs with white dwarf companions. Results: The mass distribution of hot subdwarfs with cool, low-mass stellar and substellar companions, di ffers from those with white dwarf companions, implying they come from di fferent populations. By comparing the period and minimum companion mass distributions, we find that the reflection e ffect systems all have M dwarf or brown dwarf companions, and that there seem to be several di fferent populations of hot subdwarfs with white dwarf binaries - one with white dwarf minimum masses around 0.4 M-circle dot, one with longer periods and minimum companion masses up to 0.6 M-circle dot, and at the shortest period, another with white dwarf minimum masses around 0.8 M-circle dot. We also derive the first orbital period distribution for hot subdwarfs with cool, low-mass stellar or substellar systems selected from light variations instead of radial velocity variations. It shows a narrower period distribution, from 1.5 h to 35 h, compared to the distribution of hot subdwarfs with white dwarfs, which ranges from 1 h to 30 days. These period distributions can be used to constrain the previous common-envelope phase. KW - binaries: close KW - subdwarfs KW - white dwarfs KW - stars: late-type KW - stars: KW - horizontal-branch KW - stars: fundamental parameters Y1 - 2022 U6 - https://doi.org/10.1051/0004-6361/202244214 SN - 0004-6361 SN - 1432-0746 VL - 666 PB - EDP Sciences CY - Les Ulis ER -