J/A+A/630/A130ivo://CDS.VizieR/J/A+A/630/A130doi:10.26093/cds/vizier.36300130CDSDorsch M.Latour M.Heber U.2019-10-04T17:34:03Z2019-10-04T17:46:39ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frsubdwarf-starsspectroscopyHot subluminous stars can be spectroscopically classified as subdwarf B (sdB) and O (sdO) stars. While the latter are predominantly hydrogen deficient, the former are mostly helium deficient. The atmospheres of most sdOs are almost devoid of hydrogen, whereas a small group of hot subdwarf stars of mixed H/He composition exists, showing extreme metal abundance anomalies. Whether such intermediate helium-rich (iHe) subdwarf stars provide an evolutionary link between the dominant classes is an open question. The presence of strong Ge, Sn, and Pb lines in the UV spectrum of HZ44 suggests a strong enrichment of heavy elements in this iHe-sdO star and calls for a detailed quantitative spectral analysis focusing on trans-iron elements. Non-LTE model atmospheres and synthetic spectra calculated with TLUSTY/SYNSPEC were combined with high-quality optical, ultraviolet (UV), and far-UV (FUV) spectra of HZ44 and its hotter sibling HD127493 to determine their atmospheric parameters and metal abundance patterns. By collecting atomic data from the literature we succeeded in determining the abundances of 29 metals in HZ44, including the trans-iron elements Ga, Ge, As, Se, Zr, Sn, and Pb and providing upper limits for ten other metals. This makes it the best-described hot subdwarf in terms of chemical composition. For HD127493 the abundance of 15 metals, including Ga, Ge, and Pb and upper limits for another 16 metals were derived. Heavy elements turn out to be overabundant by one to four orders of magnitude with respect to the Sun. Zr and Pb are among the most enriched elements. The C, N, and O abundance for both stars can be explained by the nucleosynthesis of hydrogen burning in the CNO cycle along with the stars' helium enrichment. On the other hand, the heavy-element anomalies are unlikely to be caused by nucleosynthesis. Instead diffusion processes are evoked, with radiative levitation overcoming gravitational settlement of the heavy elements.2019A&A...630A.130Dhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/630/A130CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/630/A130https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/630/A130http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/630/A130https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/630/A130https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/630/A130http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/630/A130GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/A+A/630/A130/hd_ferosHD 127493 FEROS spectrumrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaWavelength0.1nmem.wldoubleFluxNormalized fluxphot.fluxdoubleJ/A+A/630/A130/hd_ghrsHD 127493 HST GHRS E140M spectrumlambdaWavelength0.1nmem.wldoublerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintFluxFlux (in erg/cm^2^/s/{AA})0.01W.m**-2.nm**-1phot.fluxdoublee_FluxFlux uncertainty (in erg/cm^2^/s/{AA})0.01W.m**-2.nm**-1stat.error;phot.fluxdoubleJ/A+A/630/A130/hd_iue_lHD 127493 IUE LWR spectrumrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaWavelength0.1nmem.wldoubleFluxFlux (in erg/cm^2^/s/{AA})0.01W.m**-2.nm**-1phot.fluxdoublee_FluxFlux uncertainty (in erg/cm^2^/s/{AA})0.01W.m**-2.nm**-1stat.error;phot.fluxdoubleJ/A+A/630/A130/hz_fuseHZ 44 FUSE MDRS spectrumrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaWavelength0.1nmem.wldoubleFluxFlux (in erg/cm^2^/s/{AA})0.01W.m**-2.nm**-1phot.fluxdoublee_FluxFlux uncertainty (in erg/cm^2^/s/{AA})0.01W.m**-2.nm**-1stat.error;phot.fluxdoubleJ/A+A/630/A130/hz_hiresHZ 44 HIRES spectrumrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaWavelength0.1nmem.wldoubleFluxFlux in arbitrary unitsphot.fluxdoubleJ/A+A/630/A130/hz_isisHZ 44 ISIS spectrumrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaWavelength0.1nmem.wldoubleFluxFlux0.01W.m**-2.nm**-1phot.fluxdoubleJ/A+A/630/A130/hz_iue_sHZ 44 IUE SWP spectrumrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaWavelength0.1nmem.wldoubleFluxFlux (in erg/cm^2^/s/{AA})0.01W.m**-2.nm**-1phot.fluxdoublee_FluxFlux uncertainty (in erg/cm^2^/s/{AA})0.01W.m**-2.nm**-1stat.error;phot.fluxdoubleJ/A+A/630/A130/hd_iue_sHD 127493 IUE SWP spectrumrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaWavelength0.1nmem.wldoubleFluxFlux (in erg/cm^2^/s/{AA})0.01W.m**-2.nm**-1phot.fluxdoublee_FluxFlux uncertainty (in erg/cm^2^/s/{AA})0.01W.m**-2.nm**-1stat.error;phot.fluxdouble