Signatures of r-process elements in kilonova spectra

Binary neutron star (NS) mergers have been expected to synthesize r-process elements and emit radioactively powered radiation, called kilonova. Although r-process nucleosynthesis was confirmed by the observations of GW170817/AT2017gfo, no trace of individual elements has been identified except for strontium. In this paper, we perform systematic calculations of line strength for bound-bound transitions and radiative transfer simulations in NS merger ejecta toward element identification in kilonova spectra. We find that Sr II triplet lines appear in the spectrum of a lanthanide-poor model, which is consistent with the absorption feature observed in GW170817/AT2017gfo. The synthetic spectrum also shows the strong Ca II triplet lines. This is natural because Ca and Sr are co-produced in the material with relatively high electron fraction and their ions have similar atomic structures with only one s-electron in the outermost shell. The line strength, however, highly depends on the abundance distribution and temperature in the ejecta. For our lanthanide-rich model, the spectra show the features of doubly ionized heavy elements, such as Ce, Tb and Th. Our results suggest that the line forming region of GW170817/AT2017gfo was lanthanide-poor. We show that the Sr II and Ca II lines can be used as a probe of physical conditions in NS merger ejecta. Absence of the Ca II line features in GW170817/AT2017gfo implies that the Ca/Sr ratio is = 0.40 and entropy per nucleon (in units of Boltzmann constant) >= 25

Maturation of Recently Released Cold Hardy Wine Grap Cultivars in Iowa: Corot noir, Frontenac Gris, La Crescent, Marquette, and Noiret

Many new wine grape cultivars have been released from breeding programs developed for cold hardiness in the Midwest. Iowa State University has been observing the growing habits of selected new cultivars throughout Iowa to expand the growing wine industry. Five of the cultivars that have shown promise include Corot noir (released by Cornell University in 2006), Frontenac Gris(released by the Univ. of Minnesota in 2003), La Crescent(released by the University of Minnesota in 2002), Marquette (released by the University of Minnesota in 2006), and Noiret (released by Cornell University in 2006). The objective of this study was to monitor the general trend of the soluble solids concentration (SSC)/ºBrix, initial pH, titratable acidity, and average berry weight after the onset of veraison until grape berry maturit

Grape Cultivar by Management System Trial Performance in 2006

To identify grape cultivars adapted to Iowa, a cultivar by management system trial was established in 2002 at the ISU Horticulture Research Station (HRS) and the ISU Armstrong Research Farm (ARF) with the help of a grant from the Leopold Center of Sustainable Agriculture. Fifteen cultivars, including 10 wine and 5 seedless table cultivars, are being evaluated under 1) a conventional management system that relies on herbicides for weed control and application of insecticides and fungicides on a regular basis; 2) an IPM/best management system that uses herbicides as needed and relies on monitoring to determine the need for insecticides and fungicides; and 3) an organic approved system that relies on a straw mulch for weed control and use of organic-approved pest control strategies. This report summarizes the results for the 2006 growing season

Lanthanide Features in Near-infrared Spectra of Kilonovae

The observations of GW170817/AT2017gfo have provided us with evidence thatbinary neutron star mergers are sites of $r$-process nucleosynthesis. However,the observed signatures in the spectra of GW170817/AT2017gfo have not beenfully decoded especially in the near-infrared (NIR) wavelengths. In this paper,we investigate the kilonova spectra over the entire wavelength range with theaim of elemental identification. We systematically calculate the strength ofbound-bound transitions by constructing a hybrid line list that is accurate forimportant strong transitions and complete for weak transitions. We find thatthe elements on the left side of the periodic table, such as Ca, Sr, Y, Zr, Ba,La, and Ce, tend to produce prominent absorption lines in the spectra. This isbecause such elements have a small number of valence electrons and low-lyingenergy levels, resulting in strong transitions. By performing self-consistentradiative transfer simulations for the entire ejecta, we find that La III andCe III appear in the NIR spectra, which can explain the absorption features at$\lambda\sim 12000$-14000 A in the spectra of GW170817/AT2017gfo. The massfractions of La and Ce are estimated to be $>2\times 10^{-6}$ and $\sim$(1-100)$\times 10^{-5}$, respectively. An actinide element Th can also be asource of absorption as the atomic structure is analogous to that of Ce.However, we show that Th III features are less prominent in the spectra becauseof the denser energy levels of actinides compared to those of lanthanides.<br

2008 NE 1020 Cold Hardy Wine Grape Cultivar Trial Performance in 2010

In conjunction with the Northeast Regional Research project NE 1020 “Multi-state Evaluation of Wine Grape Cultivars and Clones,” Iowa State University established a cold hardy wine grape cultivar trial in 2008 at the ISU Horticulture Research Station (HRS) and Tabor Home Vineyards and Winery (THV) near Baldwin, IA. The Iowa trial evaluates the performance of Corot noir, La Crescent, Marquette, Petit Amie, NY 95.0301- 01, MN-1189, MN-1200, MN-1220, MN- 1235, MN-1258, with Frontenac and St. Croix serving as controls. Similar plantings were established in SD, NE, and MO, as well as in CT, IN, KY, and MI. This report summarizes the results for the 2010 growing season

Grape Cultivar by Management System Trial Performance in 2007

To identify grape cultivars adapted to Iowa, a cultivar by management system trial was established in 2002 at the Iowa State University (ISU) Horticulture Research Station (HRS) and the ISU Armstrong Research Farm (ARF) with a grant from the Leopold Center of Sustainable Agriculture. Fifteen cultivars, including ten wine and five seedless table cultivars, are being evaluated under 1) a conventional management system that relies on herbicides for weed control and application of insecticides and fungicides on a regular basis; 2) an IPM/best management system that uses herbicides as needed and relies on monitoring to determine the need for insecticides and fungicides; and 3) an organic approved system that relies on a straw mulch for weed control and use of organic-approved pest control strategies. This report summarizes the results for the 2007 growing season

2002 Grape Cultivar Trial Performance in 2009

To identify grape cultivars adapted to Iowa, a cultivar by management system trial was established in 2002 at the Iowa State University (ISU) Horticulture Research Station (HRS) and the ISU Armstrong Research Farm (ARF) with a grant from the Leopold Center of Sustainable Agriculture. Fifteen cultivars, including ten wine and five seedless table cultivars, were being evaluated under three management systems that were discontinued in 2008. This report summarizes the cultivar performance for the 2009 growing season

2002 Grape Cultivar Trial Performance

To identify grape cultivars adapted to Iowa, a cultivar by management system trial was established in 2002 at the Iowa State University (ISU) Horticulture Research Station (HRS) and the ISU Armstrong Research Farm (ARF) with a grant from the Leopold Center of Sustainable Agriculture. Fifteen cultivars, including ten wine and five seedless table cultivars, were being evaluated under three management systems that were discontinued in 2008. This report summarizes the cultivar performance for the 2010 growing season