{"id":14431,"date":"2018-03-14T22:41:12","date_gmt":"2018-03-14T21:41:12","guid":{"rendered":"http:\/\/karmaka.de\/?p=14431"},"modified":"2018-03-14T22:42:18","modified_gmt":"2018-03-14T21:42:18","slug":"14431","status":"publish","type":"post","link":"https:\/\/karmaka.de\/?p=14431","title":{"rendered":"Extremely 54Cr- and 50Ti-rich presolar oxide grains in a primitive meteorite: Formation in rare types of supernovae and implications for the astrophysical context of solar system birth<span class=\"badge-status\" style=\"background:#787878\">OPEN ACCESS<\/span>&nbsp;"},"content":{"rendered":"<p>Larry R. Nittler, Conel M. O&#8217;D. Alexander, Nan Liu, Jianhua Wang<\/p>\n<p>Accepted for publication in The Astrophysical Journal Letters<\/p>\n<p><a href=\"https:\/\/arxiv.org\/ftp\/arxiv\/papers\/1803\/1803.04286.pdf\" target=\"_blank\"><strong>PDF (OPEN ACCESS)<\/strong><\/a><\/p>\n<p>&#8220;We report the identification of 19 presolar oxide grains from the orgu CI meteorite with substantial enrichments in 54Cr, with 54Cr\/52Cr ratios ranging from 1.2 to 56 times the solar value. The most enriched grains also exhibit enrichments at mass 50, most likely due in part to 50Ti, but close-to-normal or depleted 53Cr\/52Cr ratios. There is a strong inverse relationship between 54Cr enrichment and grain size; the most extreme grains are all <80 nm in diameter. Comparison of the isotopic data with predictions of nucleosynthesis calculations indicate that these grains most likely originated in either rare, high-density Type Ia supernovae (SNIa), or in electron-capture supernovae (ECSN) which may occur as the end stage of evolution for stars of mass 8-10 Mo. This is the first evidence for preserved presolar grains from either type of supernova. An ECSN origin is attractive since these likely occur much more frequently than high-density SNIa, and their evolutionary timescales (~20 Myr) are comparable to those of molecular clouds. Self-pollution of the Sun's parent cloud from an ECSN may explain the heterogeneous distribution of n-rich isotopic anomalies in planetary materials, including a recently reported dichotomy in Mo isotopes in the solar system. The stellar origins of three grains with solar 54Cr\/52Cr, but anomalies in 50Cr or 53Cr, as well as of a grain enriched in 57Fe, are unclear. \"\n\n<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Larry R. Nittler, Conel M. O&#8217;D. Alexander, Nan Liu, Jianhua Wang Accepted for publication in The Astrophysical Journal Letters PDF (OPEN ACCESS) &#8220;We report the identification of 19 presolar oxide grains from the orgu CI&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9,10,76],"tags":[4415,3273,1809,110,4414,1853],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/14431"}],"collection":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=14431"}],"version-history":[{"count":3,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/14431\/revisions"}],"predecessor-version":[{"id":14434,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/14431\/revisions\/14434"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=14431"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=14431"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=14431"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}