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SUMMARY:Investigation of the beginnings of star formation and the synthesi
 s of chemical elements in the early Universe
DTSTART;VALUE=DATE-TIME:20190320T103500Z
DTEND;VALUE=DATE-TIME:20190320T105000Z
DTSTAMP;VALUE=DATE-TIME:20260811T111729Z
UID:indico-contribution-1346@indico.tlabs.ac.za
DESCRIPTION:Speakers: Blaine Lomberg (University of the Western Cape)\nMet
 al-poor stars provide a unique testing ground to investigate the beginning
 s of star formation and the synthesis of chemical elements in the early Un
 iverse. In particular\, the abundance patterns seen in these metal-poor st
 ars provide constraints on the nature of first generation of super-massive
  stars in the universe.  These stars are also characterized by unusual abu
 ndance patterns of carbon\, nitrogen and oxygen\, which could probably ass
 ign them as a Population II stars that formed from material chemically enr
 iched by a first-generation supernova. A parametrical search for best fits
  suggest a scenario involving low-energy supernova explosions with a relat
 ively narrow range of masses (10 − 25 solar masses) and little mixing. A
 lthough this supernova scenario might elucidate the formation of the light
  elements up to aluminium\, the experimental upper limits currently observ
 ed for the abundances of heavier elements such as Cr\, Mn\, Co\, Ni and Zn
  do not allow stronger constraints of the original supernova properties. \
 n\nMore puzzling\, however\, is the large abundance of Sr (Z=38) with [Sr/
 Fe] +1. Strontium is the only element heavier than the iron group currentl
 y observed in HE1327-2326. Supposedly\, there are two nuclear-reaction sce
 narios that could produce Sr:\n\n• The slow-neutron capture\, the s-proc
 ess\, occurring in asymptotic giant branch (AGB) stars\; how-ever\, this p
 rocess is inefficient in low metallicity.\n• The main rapid-neutron capt
 ure\, the r-process\, could also produce strontium in a type-II super-nova
 \; although the production of Sr is not included in some of the supernova 
 models.\n\nA measurement of the Ba abundance is fundamental to distinguish
  between the s-process\, with an expected relative abundance of [Sr/Ba] 
 −1\, and the r-process\, with a different ratio of [Sr/Ba] = −0.5 to 
 −0.4. Here we present the first astronomical data for EC20291-3603\, a m
 etal-poor star observed with the SALT telescope.\n\nhttps://indico.tlabs.a
 c.za/event/82/contributions/1346/
LOCATION:J Block Auditorium
URL:https://indico.tlabs.ac.za/event/82/contributions/1346/
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