J/ApJ/821/37ivo://CDS.VizieR/J/ApJ/821/37doi:10.26093/cds/vizier.18210037CDSRoederer I.U.Karakas A.I.Pignatari M.Herwig F.2017-01-23T22:00:00Z2016-07-08T07:43:28ZCDS support team

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

cds-question@unistra.frchemical-abundancesline-intensitieschemically-peculiar-starsspectroscopyultraviolet-astronomyWe present a detailed analysis of the composition and nucleosynthetic origins of the heavy elements in the metal-poor ([Fe/H]=-1.62+/-0.09) star HD 94028. Previous studies revealed that this star is mildly enhanced in elements produced by the slow neutron-capture process (s process; e.g., [Pb/Fe]=+0.79+/-0.32) and rapid neutron-capture process (r process; e.g., [Eu/Fe]=+0.22+/-0.12), including unusually large molybdenum ([Mo/Fe]= +0.97+/-0.16) and ruthenium ([Ru/Fe]=+0.69+/-0.17) enhancements. However, this star is not enhanced in carbon ([C/Fe]=-0.06+/-0.19). We analyze an archival near-ultraviolet spectrum of HD 94028, collected using the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope, and other archival optical spectra collected from ground-based telescopes. We report abundances or upper limits derived from 64 species of 56 elements. We compare these observations with s-process yields from low-metallicity AGB evolution and nucleosynthesis models. No combination of s- and r-process patterns can adequately reproduce the observed abundances, including the super-solar [As/Ge] ratio (+0.99+/-0.23) and the enhanced [Mo/Fe] and [Ru/Fe] ratios. We can fit these features when including an additional contribution from the intermediate neutron-capture process (i process), which perhaps operated through the ingestion of H in He-burning convective regions in massive stars, super-AGB stars, or low-mass AGB stars. Currently, only the i process appears capable of consistently producing the super-solar [As/Ge] ratios and ratios among neighboring heavy elements found in HD 94028. Other metal-poor stars also show enhanced [As/Ge] ratios, hinting that operation of the i process may have been common in the early Galaxy.2016ApJ...821...37Rhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/821/37CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/ApJ/817/53 : Fe-group elemental abundances in HD84937 (Sneden+, 2016)J/ApJ/812/109 : HST + Keck spectroscopy of bright CEMP-s stars (Placco+, 2015)J/ApJS/216/1 : New FeI level energies from stellar spectra (Peterson+, 2015)J/AJ/147/136 : Stars of very low metal abundance. VI. (Roederer+, 2014)J/ApJS/211/20 : NiI transition probability measurements (Wood+, 2014)J/ApJS/208/27 : Sun and HD 84937 TiII log(gf) and abundances (Wood+, 2013)J/A+A/546/A90 : NLTE analysis of Sr lines (Bergemann+, 2012)J/ApJ/750/76 : r-process peaks elements in HD 160617 (Roederer+, 2012)J/AJ/141/175 : Abundances in M15 RGB/RHB stars (Sobeck+, 2011)J/A+A/530/A138 : Geneva-Copenhagen survey re-analysis (Casagrande+, 2011)J/ApJ/743/140 : Abundances (Be,{alpha}) in metal-poor stars (Boesgaard+, 2011)J/ApJS/187/149 : StarCAT: STIS UV echelle spectra of stars (Ayres, 2010)J/ApJ/724/975 : Metal-poor star heavy element abundances (Roederer+, 2010)J/A+A/503/541 : Neutral Li in stars non-LTE calculations (Lind+, 2009)J/A+A/440/321 : Chemical abundances in 43 metal-poor stars (Jonsell+, 2005)J/ApJ/617/1091 : La and Eu abundances in 85 stars (Simmerer+, 2004)J/AJ/124/1144 : Orbits of 171 single-lined spectroscopic bin. (Latham, 2002)J/ApJ/562/528 : Teff and log(g) of low-metallicity stars (Snider+, 2001)J/A+A/354/169 : Metal-poor field stars abundances (Gratton+, 2000)J/AJ/107/2240 : Proper motion stars survey. XII. (Carney+, 1994)http://www.nist.gov/pml/data/asd.cfm : NIST atomic spectra databasehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/821/37https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/821/37http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/821/37https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/821/37https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/821/37http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/821/37GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapUVdefaultJ/ApJ/821/37/table2NUV iron lines examinedrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSpSpeciesphys.atmol.ionStagecharlambda[2078.1/3091.6] Wavelength in Angstroms0.1nmem.wlfloatExPot[0/6] Excitation potential in eVeVphys.atmol.excitationfloatlog(gf)[-3/0.8] Log of degeneracy times oscillator strengthphys.atmol.oscStrengthfloatEW[23/186] Equivalent width in milli Angstroms0.1pmspect.line.eqWidthfloatlogeps[5.1/6.7] Log {epsilon} abundancephys.abundfloatJ/ApJ/821/37/table3Derived abundances in HD 94028recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSpSpeciesphys.atmol.ionStagecharN[1/96] Number of lines used in derived abundancemeta.numberintf_logepsLimit flag on logepsmeta.codecharlogeps[-1/7.6] Log {epsilon} abundancephys.abundfloatl_[X/Fe]Limit flag on [X/Fe]meta.code.error;phys.abundchar[X/Fe][-1.8/1.9]? Abundance (1)phys.abundfloatnullables_[X/Fe][0.03/0.4]? Uncertainty in [X/Fe], statistical ({sigma}-stat) (2)stat.errorfloatnullablee_[X/Fe][0.09/0.4]? Uncertainty in [X/Fe], total (3)stat.error;phys.abundfloatnullablesigI[0/0.4]? Uncertainty in [X/Fe], Error 1 (4)stat.error;phys.abundfloatnullablesigII[0/0.4]? Uncertainty in [X/Fe], Error 2 (4)stat.error;phys.abundfloatnullablelogepsSun[0.1/8.7]? Solar Reference Abundancephys.abundfloatnullableJ/ApJ/821/37/table1Abundances derived from lines examined in this studyrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSpSpeciesphys.atmol.ionStagecharlambda[1890.4/3499] Wavelength in Angstroms0.1nmem.wlfloatExPot[0/3.3] Excitation potential in eVeVphys.atmol.excitationfloatlog(gf)[-1.4/0.4] Log of degeneracy times oscillator strengthphys.atmol.oscStrengthfloate_log(gf)[0.002/0.08]? Uncertainty in log(gf)stat.errorfloatnullableRef[1/15] Line Reference (1)meta.ref;pos.frame;spect.lineintl_logepsLimit flag on logepsmeta.code.errorcharlogeps[-0.7/2.6] Log {epsilon} abundancephys.abundfloate_logeps[0.05/0.3]? Uncertainty in logepsstat.errorfloatnullable