Browsing by Author "Placco, Vinicius M."

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    The Origin of the 300 km s(-1) Stream near Segue 1
    (2018) Fu, Sal Wanying; Simon, Joshua D.; Shetrone, Matthew; Bovy, Jo; Beers, Timothy C.; Fernandez-Trincado, J. G.; Placco, Vinicius M.; Zamora, Olga; Allende Prieto, Carlos; Garcia-Hernandez, D. A.; Harding, Paul; Ivans, Inese; Lane, Richard; Nitschelm, Christian; Roman-Lopes, Alexandre; Sobeck, Jennifer
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    The Photometric Metallicity and Carbon Distributions of the Milky Way's Halo and Solar Neighborhood from S-PLUS Observations of SDSS Stripe 82
    (2021) Whitten, Devin D.; Placco, Vinicius M.; Beers, Timothy C.; An, Deokkeun; Lee, Young Sun; Almeida-Fernandes, Felipe; Herpich, Fabio R.; Daflon, Simone; Barbosa, Carlos E.; Perottoni, Helio D.; Rossi, Silvia; Tissera, Patricia B.; Yoon, Jinmi; Youakim, Kris; Schoenell, William; Ribeiro, Tiago; Kanaan, Antonio
    We report photometric estimates of effective temperature, T (eff), metallicity, [Fe/H], carbonicity, [C/Fe], and absolute carbon abundances, A(C), for over 700,000 stars from the Southern Photometric Local Universe Survey (S-PLUS) Data Release 2, covering a substantial fraction of the equatorial Sloan Digital Sky Survey Stripe 82. We present an analysis for two stellar populations: (1) halo main-sequence turnoff stars and (2) K-dwarf stars of mass 0.58 < M/M (circle dot) < 0.75 in the Solar Neighborhood. Application of the Stellar Photometric Index Network Explorer (SPHINX) to the mixed-bandwidth (narrow- plus wide-band) filter photometry from S-PLUS produces robust estimates of the metallicities and carbon abundances in stellar atmospheres over a wide range of temperatures, 4250 < T (eff)(K) < 7000. The use of multiple narrow-band S-PLUS filters enables SPHINX to achieve substantially lower levels of "catastrophic failures" (i.e., large offsets in metallicity estimates relative to spectroscopic determinations) than previous efforts using a single metallicity-sensitive narrow-band filter. We constrain the exponential slope of the Milky Way's K-dwarf halo metallicity distribution function (MDF), lambda (10,[Fe/H]) = 0.85 +/- 0.21, over the metallicity range -2.5 < [Fe/H] < -1.0; the MDF of our local-volume K-dwarf sample is well-represented by a gamma distribution with parameters alpha = 2.8 and beta = 4.2. S-PLUS photometry obtains absolute carbon abundances with a precision of similar to 0.35 dex for stars with T (eff) < 6500 K. We identify 364 candidate carbon-enhanced metal-poor stars, obtain assignments of these stars into the Yoon-Beers morphological groups in the A(C)-[Fe/H] space, and we derive the CEMP frequencies.
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    The R-process alliance: spectroscopic follow-up of low-metallicity star candidates from the best & brightest survey
    (2019) Placco, Vinicius M.; Santucci, Rafael M.; Beers, Timothy C.; Chaname, Julio; Sepulveda, Maria Paz; Coronado, Johanna; Rossi, Silvia; Sun Lee, Young; Starkenburg, Else; Youakim, Kris