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Gamma Ray Bursts As Probes Of Dust In The Evolving Universe, Adria Updike
Gamma Ray Bursts As Probes Of Dust In The Evolving Universe, Adria Updike
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Dust is ubiquitous in the universe. Understanding where it comes from and where we observe it can have major implications to all astronomical observations. In this study, we investigate how gamma ray bursts (GRBs) can be used as probes of dust in the evolving universe. Making the simplification that silicate dust comes from core collapse supernovae and that graphite dust is produced in the winds of low- to intermediate-mass stars, we present numerical simulations of the resulting dust evolution in GRB hosts and show how the SEDs evolve. Dust extinction laws are re-derived from scattering theory of small particles and …
A Spectroscopic Analysis Of Hd 134439 And Hd 134440, Yu Chen
A Spectroscopic Analysis Of Hd 134439 And Hd 134440, Yu Chen
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We analyze elemental abundances of the common proper motion pair HD 134439 and HD 134440 to understand their formation history. This pair of metal-poor ([Fe/H]$\sim -1.50$) halo dwarfs are known, from previous studies, to exhibit abnormally low [$\alpha$/Fe] ratios compared to typical Galactic halo stars. Some have attributed this to planetesimal accretion; others believe these stars formed in the dusty part of a dwarf spheroidal galaxy and were later captured by our Galaxy. To investigate this anomaly, we measure carbon, nitrogen, and oxygen abundances for HD 134439 and HD 134440 from near-UV molecular features using high-resolution spectra obtained with Keck …