RV variable, hot post-AGB stars from the MUCHFUSS project - Classification, atmospheric parameters, formation scenarios

摘要: In the course of MUCHFUSS project we have recently discovered four radial velocity (RV) variable, hot (Teff $\approx$ 80,000 - 110,000 K) post-asymptotic giant branch (AGB) stars. Among them, found first known RV variable O(He) star, only second PG 1159 close binary candidate, as well two naked (i.e., without planetary nebula (PN)) H-rich post-AGB stars spectral type O(H) that show significant variations. We present a non-LTE analysis these along with one further O(H)-type star whose variations were to be not significant. also report discovery an far-infrared excess in case star. None our sample displays nebular emission lines, which can explained terms very late thermal pulse evolution The "missing" PNe around seem strange, since find several central much longer times. Besides non-ejection PN, occurrence pulse, or re-accretion PN previous offer possible explanations for those harbouring (anymore). J0757 speculate it might been previously part compact He transferring system. this scenario, mass transfer must stopped after certain time, leaving behind low companion could responsible extreme shift 107.0 $\pm$ 22.0 km/s measured within 31 min.