Browsing by Author "Bom, C. R."

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    Constraints on the Physical Properties of GW190814 through Simulations Based on DECam Follow-up Observations by the Dark Energy Survey
    (2020) Morgan, R.; Soares Santos, M.; Annis, J.; Herner, K.; Garcia, A.; Palmese, A.; Drlica Wagner, A.; Kessler, R.; Garcia Bellido, J.; Quirola Vásquez, Jonathan Alexander; Bachmann, T. G.; Sherman, N.; Allam, S.; Bechtol, K.; Bom, C. R.; Brout, D.; Butler, R. E.; Butner, M.; Cartier, R.; Chen, H.; Conselice, C.; Cook, E.; Davis, T. M.; Doctor, Z.; Farr, B.; Figueiredo, A. L.; Finley, D. A.; Foley, R. J.; Galarza, J. Y.; Gill, M. S. S.; Gruendl, R. A.; Holz, D. E.; Kuropatkin, N.; Lidman, C.; Lin, H.; Malik, U.; Mann, A. W.; Marriner, J.; Marshall, J. L.; Martinez Vazquez, C. E.; Meza, N.; Neilsen, E.; Nicolaou, C.; Olivares, E. F.; Paz Chinchon, F.; Points, S.; Rodriguez, O.; Sako, M.; Scolnic, D.; Smith, M.; Sobreira, F.; Tucker, D. L.; Vivas, A. K.
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    SOAR/Goodman Spectroscopic Assessment of Candidate Counterparts of the LIGO/Virgo Event GW190814*
    (2022) Tucker, D. L.; Wiesner, M. P.; Allam, S. S.; Soares-Santos, M.; Bom, C. R.; Butner, M.; Garcia, A.; Morgan, R.; Olivares E, F.; Palmese, A.; Santana-Silva, L.; Shrivastava, A.; Annis, J.; Garcia-Bellido, J.; Gill, M. S. S.; Herner, K.; Kilpatrick, C. D.; Makler, M.; Sherman, N.; Amara, A.; Lin, H.; Smith, M.; Swann, E.; Arcavi, I; Bachmann, T. G.; Bechtol, K.; Berlfein, F.; Briceno, C.; Brout, D.; Butler, R. E.; Cartier, R.; Casares, J.; Chen, H-Y; Conselice, C.; Contreras, C.; Cook, E.; Cooke, J.; Dage, K.; D'Andrea, C.; Davis, T. M.; de Carvalho, R.; Diehl, H. T.; Dietrich, J. P.; Doctor, Z.; Drlica-Wagner, A.; Drout, M.; Farr, B.; Finley, D. A.; Fishbach, M.; Foley, R. J.; Forster-Buron, F.; Fosalba, P.; Friedel, D.; Frieman, J.; Frohmaier, C.; Gruendl, R. A.; Hartley, W. G.; Hiramatsu, D.; Holz, D. E.; Howell, D. A.; Kawash, A.; Kessler, R.; Kuropatkin, N.; Lahav, O.; Lundgren, A.; Lundquist, M.; Malik, U.; Mann, A. W.; Marriner, J.; Marshall, J. L.; Martinez-Vazquez, C. E.; McCully, C.; Menanteau, F.; Meza, N.; Narayan, G.; Neilsen, E.; Nicolaou, C.; Nichol, R.; Paz-Chinchon, F.; Pereira, M. E. S.; Pineda, J.; Points, S.; Quirola-Vasquez, J.; Rembold, S.; Rest, A.; Rodriguez, O.; Romer, A. K.; Sako, M.; Salim, S.; Scolnic, D.; Smith, J. A.; Strader, J.; Sullivan, M.; Swanson, M. E. C.; Thomas, D.; Valenti, S.; Varga, T. N.; Walker, A. R.; Weller, J.; Wood, M. L.; Yanny, B.; Zenteno, A.; Aguena, M.; Andrade-Oliveira, F.; Bertin, E.; Brooks, D.; Burke, D. L.; Rosell, A. Carnero; Kind, M. Carrasco; Carretero, J.; Costanzi, M.; da Costa, L. N.; De Vicente, J.; Desai, S.; Everett, S.; Ferrero, I; Flaugher, B.; Gaztanaga, E.; Gerdes, D. W.; Gruen, D.; Gschwend, J.; Gutierrez, G.; Hinton, S. R.; Hollowood, D. L.; Honscheid, K.; James, D. J.; Kuehn, K.; Lima, M.; Maia, M. A. G.; Miquel, R.; Ogando, R. L. C.; Pieres, A.; Malagon, A. A. Plazas; Rodriguez-Monroy, M.; Sanchez, E.; Scarpine, V; Schubnell, M.; Serrano, S.; Sevilla-Noarbe, I; Suchyta, E.; Tarle, G.; To, C.; Zhang, Y.
    On 2019 August 14 at 21:10:39 UTC, the LIGO/Virgo Collaboration (LVC) detected a possible neutron star-black hole merger (NSBH), the first ever identified. An extensive search for an optical counterpart of this event, designated GW190814, was undertaken using the Dark Energy Camera on the 4 m Victor M. Blanco Telescope at the Cerro Tololo Inter-American Observatory. Target of Opportunity interrupts were issued on eight separate nights to observe 11 candidates using the 4.1 m Southern Astrophysical Research (SOAR) telescope's Goodman High Throughput Spectrograph in order to assess whether any of these transients was likely to be an optical counterpart of the possible NSBH merger. Here, we describe the process of observing with SOAR, the analysis of our spectra, our spectroscopic typing methodology, and our resultant conclusion that none of the candidates corresponded to the gravitational wave merger event but were all instead other transients. Finally, we describe the lessons learned from this effort. Application of these lessons will be critical for a successful community spectroscopic follow-up program for LVC observing run 4 (O4) and beyond.
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    Stellar atmospheric parameters and chemical abundances of ∼5 million stars from S-PLUS multiband photometry
    (EDP SCIENCES S A, 2025) Ferreira Lopes, C. E.; Gutierrez-Soto, L. A.; S. Ferreira Alberice, V.; Monsalves, N.; Hazarika, D.; Catelan, Márcio; Placco, V. M.; Limberg, G.; Almeida-Fernandes, F.; Perottoni, H. D.; Smith Castelli, A. V.; Akras, S.; Alonso-Garcia, J.; Cordeiro, V.; Jaque Arancibia, M.; Daflon, S.; Dias, B.; Goncalves, D. R.; Machado-Pereira, E.; Lopes, A. R.; Bom, C. R.; Thom de Souza, R. C.; de Isidio, N. G.; Alvarez-Candal, A.; De Rossi, M. E.; Bonatto, C. J.; Cubillos Palma, B.; Borges Fernandes, M.; Humire, P. K.; Oliveira Schwarz, G. B.; Schoenell, W.; Kanaan, A.; Mendes de Oliveira, C.
    Context. The APOGEE, GALAH, and LAMOST spectroscopic surveys have substantially contributed to our understanding of the Milky Way by providing a wide range of stellar parameters and chemical abundances. Complementing these efforts, photometric surveys that include narrowband and medium-band filters, such as Southern Photometric Local Universe Survey (S-PLUS), provide a unique opportunity to estimate the atmospheric parameters and elemental abundances for a much larger number of sources, compared to spectroscopic surveys., Aims. Our aim is to establish methodologies for extracting stellar atmospheric parameters and selected chemical abundances from S-PLUS photometric data, which cover approximately 3000 square degrees, by applying seven narrowband and five broadband filters., Methods. We used all 66 S-PLUS colors to estimate parameters based on three different training samples from the LAMOST, APOGEE, and GALAH surveys, applying cost-sensitive neural network (NN) and random forest (RF) algorithms. We kept the stellar abundances that lacked corresponding absorption features in the S-PLUS filters to test for spurious correlations in our method. Furthermore, we evaluated the effectiveness of the NN and RF algorithms by using estimated T-eff and log g values as the input features to determine other stellar parameters and abundances. The NN approach consistently outperforms the RF technique on all parameters tested. Moreover, incorporating T-eff and log g leads to an improvement in the estimation accuracy by approximately 3%. We kept only parameters with a goodness-of-fit higher than 50%., Results. Our methodology allowed us to obtain reliable estimates for fundamental stellar parameters (T-eff, log g, and [Fe/H]) and elemental abundance ratios such as [alpha/Fe], [Al/Fe], [C/Fe], [Li/Fe], and [Mg/Fe] for approximately five million stars across the Milky Way, with a goodness-of-fit above 60%. We also obtained additional abundance ratios, including [Cu/Fe], [O/Fe], and [Si/Fe]. However, these ratios should be used cautiously due to their low accuracy or lack of a clear relationship with the S-PLUS filters. Validation of our estimations and methods was performed using star clusters, Transiting Exoplanet Survey Satellite (TESS) data and Javalambre Photometric Local Universe Survey (J-PLUS) photometry, further demonstrating the robustness and accuracy of our approach., Conclusions. By leveraging S-PLUS photometric data and advanced machine learning techniques, we have established a robust framework for extracting fundamental stellar parameters and chemical abundances from medium-band and narrowband photometric observations. This approach offers a cost-effective alternative to high-resolution spectroscopy. The estimated parameters hold significant potential for future studies, particularly when classifying objects within our Milky Way or gaining insights into its various stellar populations.