Zobrazeno 1 - 10
of 154
pro vyhledávání: '"Ian U. Roederer"'
Autor:
Ian U. Roederer, Timothy C. Beers, Kohei Hattori, Vinicius M. Placco, Terese T. Hansen, Rana Ezzeddine, Anna Frebel, Erika M. Holmbeck, Charli M. Sakari
Publikováno v:
The Astrophysical Journal, Vol 971, Iss 2, p 158 (2024)
We present stellar parameters and chemical abundances of 47 elements detected in the bright ( V = 11.63) very metal-poor ([Fe/H] = −2.20 ± 0.12) star 2MASS J22132050−5137385. We observed this star using the Magellan Inamori Kyocera Echelle spect
Externí odkaz:
https://doaj.org/article/2d11aa88c5fc4f40bc5f093fadd3089c
Autor:
Jonathan Cabrera Garcia, Charli M. Sakari, Ian U. Roederer, Donavon W. Evans, Pedro Silva, Mario Mateo, Ying-Yi Song, Anthony Kremin, John I. Bailey III, Matthew G. Walker
Publikováno v:
The Astrophysical Journal, Vol 967, Iss 2, p 101 (2024)
M15 is a globular cluster with a known spread in neutron-capture elements. This paper presents abundances of neutron-capture elements for 62 stars in M15. Spectra were obtained with the Michigan/Magellan Fiber System spectrograph, covering a waveleng
Externí odkaz:
https://doaj.org/article/e6fab1130f404c2dbf9ec27be01f68a5
Autor:
Vinicius M. Placco, Felipe Almeida-Fernandes, Erika M. Holmbeck, Ian U. Roederer, Mohammad K. Mardini, Christian R. Hayes, Kim Venn, Kristin Chiboucas, Emily Deibert, Roberto Gamen, Jeong-Eun Heo, Miji Jeong, Venu Kalari, Eder Martioli, Siyi Xu, Ruben Diaz, Manuel Gomez-Jimenez, David Henderson, Pablo Prado, Carlos Quiroz, Roque Ruiz-Carmona, Chris Simpson, Cristian Urrutia, Alan W. McConnachie, John Pazder, Gregory Burley, Michael Ireland, Fletcher Waller, Trystyn A. M. Berg, J. Gordon Robertson, Zachary Hartman, David O. Jones, Kathleen Labrie, Gabriel Perez, Susan Ridgway, Joanna Thomas-Osip
Publikováno v:
The Astrophysical Journal, Vol 959, Iss 1, p 60 (2023)
We report on a chemo-dynamical analysis of SPLUS J142445.34−254247.1 (SPLUS J1424−2542), an extremely metal-poor halo star enhanced in elements formed by the rapid neutron-capture process ( r -process). This star was first selected as a metal-poo
Externí odkaz:
https://doaj.org/article/a253f5ad355e48d783e9c8f4b24f320a
Autor:
Matthew G. Walker, Nelson Caldwell, Mario Mateo, Edward W. Olszewski, Andrew B. Pace, John I. Bailey III, Sergey E. Koposov, Ian U. Roederer
Publikováno v:
The Astrophysical Journal Supplement Series, Vol 268, Iss 1, p 19 (2023)
We present spectroscopic data for 16,369 stellar targets within and/or toward 38 dwarf spheroidal galaxies and faint star clusters within the Milky Way halo environment. All spectra come from observations with the multiobject, fiber-fed echelle spect
Externí odkaz:
https://doaj.org/article/ecca77af27fd4bb49ee878a43e2efbc1
Autor:
Ian U. Roederer, Andrew B. Pace, Vinicius M. Placco, Nelson Caldwell, Sergey E. Koposov, Mario Mateo, Edward W. Olszewski, Matthew G. Walker
Publikováno v:
The Astrophysical Journal, Vol 954, Iss 1, p 55 (2023)
We present the stellar parameters and chemical abundances of 30 elements for five stars located at large radii (3.5–10.7 times the half-light radius) in the Sextans dwarf spheroidal galaxy. We selected these stars using proper motions, radial veloc
Externí odkaz:
https://doaj.org/article/15c0d5e66c7c413cb6490f362b797be0
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
Publikováno v:
The Astrophysical Journal, Vol 951, Iss 1, p 30 (2023)
With the most trans-iron elements detected of any star outside the solar system, HD 222925 represents the most complete chemical inventory among metal-poor stars enhanced with elements made by the rapid neutron capture (“ r ”) process. As such, H
Externí odkaz:
https://doaj.org/article/f0963bcfdb924bbd90a0e30658c27d61
Autor:
Shivani P. Shah, Rana Ezzeddine, Alexander P. Ji, Terese T. Hansen, Ian U. Roederer, Márcio Catelan, Zoe Hackshaw, Erika M. Holmbeck, Timothy C. Beers, Rebecca Surman
Publikováno v:
The Astrophysical Journal, Vol 948, Iss 2, p 122 (2023)
The ages of the oldest stars shed light on the birth, chemical enrichment, and chemical evolution of the universe. Nucleocosmochronometry provides an avenue to determining the ages of these stars independent from stellar-evolution models. The uranium
Externí odkaz:
https://doaj.org/article/0e708594300249cc9be7ce7ac82f3c27
Autor:
Derek Shank, Timothy C. Beers, Vinicius M. Placco, Dmitrii Gudin, Thomas Catapano, Erika M. Holmbeck, Rana Ezzeddine, Ian U. Roederer, Charli M. Sakari, Anna Frebel, Terese T. Hansen
Publikováno v:
The Astrophysical Journal, Vol 943, Iss 1, p 23 (2023)
Orbital characteristics based on Gaia Early Data Release 3 astrometric parameters are analyzed for ∼1700 r -process-enhanced (RPE; [Eu/Fe] > +0.3) metal-poor stars ([Fe/H] ≤ −0.8) compiled from the R -Process Alliance, the GALactic Archaeology
Externí odkaz:
https://doaj.org/article/a16e1c009f1042219ca5bb6775e1a303
Autor:
Alexander P. Ji, Joshua D. Simon, Ian U. Roederer, Ekaterina Magg, Anna Frebel, Christian I. Johnson, Ralf S. Klessen, Mattis Magg, Gabriele Cescutti, Mario Mateo, Maria Bergemann, John I. Bailey III
Publikováno v:
The Astronomical Journal, Vol 165, Iss 3, p 100 (2023)
The ultrafaint dwarf galaxy Reticulum II was enriched by a single rare and prolific r -process event. The r -process content of Reticulum II thus provides a unique opportunity to study metal mixing in a relic first galaxy. Using multi-object high-res
Externí odkaz:
https://doaj.org/article/57b2a0a0aa9c4a76803aa68050dd8709