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<strong style="background: none; margin-top: 0pt; margin-bottom: 0pt;">Tomorrow at 13:00</strong><span data-preserver-spaces="true" style="background: none; margin-top: 0pt; margin-bottom: 0pt;"> in the Extreme Object meeting, Albert Sneppen will talk about
the identification of yttrium in a kilonova photosphere. </span></p>
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<span data-preserver-spaces="true" style="background: none; margin-top: 0pt; margin-bottom: 0pt;">Hope to see you all there!</span></p>
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<font size="2"><strong style="background: none; margin-top: 0pt; margin-bottom: 0pt;">When:</strong><span data-preserver-spaces="true" style="background: none; margin-top: 0pt; margin-bottom: 0pt;"> May 25th at 13:00</span></font></p>
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<font size="2"><strong style="background: none; margin-top: 0pt; margin-bottom: 0pt;">Where: </strong><span data-preserver-spaces="true" style="background: none; margin-top: 0pt; margin-bottom: 0pt;">MEGA room (Nordita 6th floor) (zoom under previous request)</span></font></p>
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<span style="font-size: 14px;"><strong style="background: none; margin-top: 0pt; margin-bottom: 0pt;">Speaker:</strong><span data-preserver-spaces="true" style="background: none; margin-top: 0pt; margin-bottom: 0pt;"> Albert Sneppen</span></span></p>
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<strong style="font-size: 14px; background: none; margin-top: 0pt; margin-bottom: 0pt;">Title: </strong></p>
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<span data-preserver-spaces="true" style="background: none; margin-top: 0pt; margin-bottom: 0pt;"><font size="4">Identification of yttrium in a kilonova photosphere</font><span style="font-size: 14px;"> </span></span></p>
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<strong style="background: none; margin-top: 0pt; margin-bottom: 0pt; font-size: 14px;">Abstract:</strong></p>
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<em style="background: none; margin-top: 0pt; margin-bottom: 0pt; font-size: 14px;">Neutron star mergers are believed to be a major cosmological source of rapid neutron-capture elements. However, the kilonovae associated with neutron star mergers have to date
yielded only a single well-identified spectral signature: the P Cygni line of Sr II at about 1 micron in the spectra of the optical transient, AT2017gfo. Such P Cygni lines are important, because they provide significant information not just potentially on
the elemental composition of the merger ejecta, but also on the velocity, geometry, and abundance stratification of the explosion. In this talk, I will present evidence for a previously unrecognised P Cygni line in the spectra of AT2017gfo that emerged several
days after the explosion. We show that such a feature is actually predicted by the 4d^2--4d5p transitions in Y II in terms of central wavelength, velocity stratification, prominence of the feature and the timing of the first appearance. We will discuss the
implications of this identification for the synthesis of the heaviest elements in the universe.</em></p>
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