Zobrazeno 1 - 10
of 187
pro vyhledávání: '"John J. Cowan"'
Autor:
Christopher Sneden, Ann Merchant Boesgaard, John J. Cowan, Ian U. Roederer, Elizabeth A. Den Hartog, James E. Lawler
Publikováno v:
The Astrophysical Journal, Vol 953, Iss 1, p 31 (2023)
We have derived new detailed abundances of Mg, Ca, and the Fe-group elements Sc through Zn ( Z = 21−30) for 37 main-sequence turnoff very metal-poor stars ([Fe/H] ≲−2.1). We analyzed Keck HIRES optical and near-UV high signal-to-noise spectra o
Externí odkaz:
https://doaj.org/article/abff1979f627483fbb8351eda22cb517
Autor:
Ian U. Roederer, John J. Cowan, Marco Pignatari, Timothy C. Beers, Elizabeth A. Den Hartog, Rana Ezzeddine, Anna Frebel, Terese T. Hansen, Erika M. Holmbeck, Matthew R. Mumpower, Vinicius M. Placco, Charli M. Sakari, Rebecca Surman, Nicole Vassh
We present new observational benchmarks of rapid neutron-capture process (r-process) nucleosynthesis for elements at and between the first (A ~ 80) and second (A ~ 130) peaks. Our analysis is based on archival ultraviolet and optical spectroscopy of
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::d569ad7dd4a05bbad140851fb27f74d1
http://arxiv.org/abs/2210.15105
http://arxiv.org/abs/2210.15105
Autor:
Christopher Sneden, Ian B. Thompson, John J. Cowan, Stephen A. Shectman, Xiaowei Ou, Ian U. Roederer, James E. Lawler
We present vanadium (V) abundances for 255 metal-poor stars, derived from high-resolution optical spectra from the Magellan Inamori Kyocera Echelle spectrograph on the Magellan Telescopes at Las Campanas Observatory, the Robert G. Tull Coud\'{e} Spec
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::da1e07049b328a368e77f7228c1a2946
http://arxiv.org/abs/2008.05500
http://arxiv.org/abs/2008.05500
Autor:
Ian U. Roederer, Christopher Sneden, John J. Cowan, Ann Merchant Boesgaard, Elizabeth A. Den Hartog, James E. Lawler, Jennifer Sobeck
We have obtained new detailed abundances of the Fe-group elements Sc through Zn (Z=21-30) in three very metal-poor ([Fe/H] $\approx -3$) stars: BD 03 740, BD -13 3442 and CD -33 1173. High-resolution ultraviolet HST/STIS spectra in the wavelength ran
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::9ba4488099e9ff13f2a18c12e899963c
Publikováno v:
Canadian Journal of Physics. 95:783-789
The synthesis of iron (Fe-) group elements was different in the early Galaxy than it is today. Measurements of the relative Fe-group elemental abundances in old metal-poor stars yield information on the Galactic chemical evolution and some informatio
The development of tunable dye lasers and a simple atomic and ionic beam source for all elements were critical in establishing a reliable absolute scale for atomic transition probabilities in the optical to near UV regions. The laboratory astrophysic
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::8b2f57ca6cd75e3fd6ee24231d0497ee
https://europepmc.org/articles/PMC6893917/
https://europepmc.org/articles/PMC6893917/
Autor:
Charli M. Sakari, Kim A. Venn, Fred Watson, Joss Bland-Hawthorn, Georges Kordopatis, Vinicius M. Placco, Brad K. Gibson, Elizabeth M. Farrell, Terese T. Hansen, Cristina Chiappini, Eva K. Grebel, Warren A. Reid, Timothy C. Beers, Anna Frebel, Kenneth C. Freeman, Gal Matijevic, Amina Helmi, Andrea Kunder, Matthias Steinmetz, Julio F. Navarro, Christopher Sneden, George Wallerstein, Rosemary F. G. Wyse, George M. Seabroke, John J. Cowan, Rana Ezzeddine, Ian U. Roederer
Publikováno v:
The Astrophysical Journal, 874(2):148. IOP PUBLISHING LTD
A new moderately r-process-enhanced metal-poor star, RAVE J093730.5-062655, has been identified in the Milky Way halo as part of an ongoing survey by the R-Process Alliance. The temperature and surface gravity indicate that J0937-0626 is likely a hor
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::627f4e98f26a4b73e68478e5e1f8693d
https://research.rug.nl/en/publications/a8401373-7219-43b0-bbd0-8812ab20bff1
https://research.rug.nl/en/publications/a8401373-7219-43b0-bbd0-8812ab20bff1
We report new branching fractions for 121 UV lines from the low-lying odd-parity levels of Fe II belonging to the z6Do, z6Fo, z6Po, z4Fo, z4Do and z4Po terms of the 3d6(5D)4p configuration. These lines range in wavelength from 2250 - 3280 {\AA} and o
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::a287611804f654a6e84f36ae65b44695
Autor:
Cristina Chiappini, John J. Cowan, Charli M. Sakari, Andrea Kunder, Matthias Steinmetz, Rosemary F. G. Wyse, Timothy C. Beers, Erika M. Holmbeck, Elizabeth M. Farrell, Warren A. Reid, Rana Ezzeddine, Brad K. Gibson, Julio F. Navarro, Joss Bland-Hawthorn, Amina Helmi, George M. Seabroke, Anna Frebel, Christopher Sneden, George Wallerstein, Ian U. Roederer, Terese T. Hansen, Kenneth C. Freeman, Gal Matijevic, Kim A. Venn, Georges Kordopatis, Vinicius M. Placco, Eva K. Grebel, Christopher Evan Davis, Fred Watson
Publikováno v:
The Astrophysical Journal, 868(2):110. IOP PUBLISHING LTD
This paper presents the detailed abundances and r-process classifications of 126 newly identified metal-poor stars as part of an ongoing collaboration, the R-Process Alliance. The stars were identified as metal-poor candidates from the RAdial Velocit
Publikováno v:
The Astrophysical journal
New branching fraction measurements based primarily on data from a cross dispersed echelle spectrometer are reported for 84 lines of Co II. The branching fractions for 82 lines are converted to absolute atomic transition probabilities using radiative
Externí odkaz:
https://explore.openaire.eu/search/publication?articleId=doi_dedup___::d0259ea093cabfaa2bd0c770926e915b
http://arxiv.org/abs/1806.00581
http://arxiv.org/abs/1806.00581