000002218 001__ 2218
000002218 005__ 20160706143420.0
000002218 0247_ $$2DOI$$a10.1051/0004-6361/201118727
000002218 037__ $$aASTROimport-375
000002218 100__ $$aGorlova, N.
000002218 245__ $$aTime-resolved spectroscopy of BD+46°442: Gas streams and jet creation in a newly discovered evolved binary with a disk
000002218 260__ $$c2012
000002218 520__ $$aContext. Previous studies have shown that many post-asymptotic giant branch (AGB) stars with dusty disks are associated with single-lined binary stars. The inferred orbital separations are too small to accommodate a fully grown AGB star, hence these systems represent a new evolutionary channel that bypasses a full AGB evolution.  Aims: We wish to verify the binarity hypothesis for a larger sample establish the nature of the companions, and probe the disk structure and eventually the disk formation mechanisms in binary stars. To achieve these aims, we started a high-resolution spectral monitoring of ~40 field giants whose binarity had been suspected based on either a light curve, an infrared excess, or a peculiar chemical composition.  Methods: Starting from the spring of 2009, we monitored the programme stars with the fibre echelle spectrometer HERMES. We measure their radial velocities (RVs) with a precision of ~0.2 km s-1, perform detailed photospheric abundance analyses, and analyse the time-resolved high-resolution spectra to search for line-profile variability.  Results: Here we report on the discovery of periodic RV variations in BD+46°442, a high Galactic latitude F giant with a disk. We infer that the variations are caused by the motion around a faint companion, and deduce the orbital parameters Porb = 140.77 ± 0.02d,e = 0.083 ± 0.002, and asini = 0.31 AU. We find that it is a moderately metal-poor star ([M/H] = -0.7) without a strong depletion pattern in its photospheric abundances. Interestingly, many lines indeed show periodic changes with the orbital phase: Ha switches between a double-peak emission line and a P Cyg-like profile, while strong metal lines appear to be split at the maximum redshift. Similar effects are likely visible in the spectra of other post-AGB binaries, but their regularity is not always apparent owing to sporadic observations. We propose that these features result from an ongoing mass transfer from the evolved giant to the companion. In particular, the blue-shifted absorption in Ha, which occurs only at superior conjunction, may result from a jet originating in the accretion disk around the companion and that is seen in absorption towards the luminous primary. Based on observations made with the Mercator Telescope, operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.Appendix A is available in electronic form at http://www.aanda.org
000002218 700__ $$aVan Winckel, H.
000002218 700__ $$aGielen, C.
000002218 700__ $$aRaskin, G.
000002218 700__ $$aPrins, S.
000002218 700__ $$aPessemier, W.
000002218 700__ $$aWaelkens, C.
000002218 700__ $$aFrémat, Y.
000002218 700__ $$aHensberge, H.
000002218 700__ $$aDumortier, L.
000002218 700__ $$aJorissen, A.
000002218 700__ $$aVan Eck, S.
000002218 773__ $$cA27$$pAstronomy and Astrophysics$$v542$$y2012
000002218 85642 $$ahttp://esoads.eso.org/abs/2012A%26A...542A..27G
000002218 905__ $$apublished in
000002218 980__ $$aREFERD