Browsing by Author "Ferreira Lopes, C. E."
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- ItemCAPOS: The bulge Cluster APOgee Survey. I. Overview and initial ASPCAP results(2021) Geisler, D.; Villanova, S.; O'Connell, J. E.; Cohen, R. E.; Moni Bidin, C.; Fernández-Trincado, J. G.; Muñoz, C.; Minniti, D.; Zoccali, M.; Rojas-Arriagada, A.; Contreras Ramos, R.; Catelan, Márcio; Mauro, F.; Cortés, C.; Ferreira Lopes, C. E.; Arentsen, A.; Starkenburg, E.; Martin, N. F.; Tang, B.; Parisi, C.; Alonso-García, J.; Gran, F.; Cunha, K.; Smith, V.; Majewski, S. R.; Jönsson, H.; García-Hernández, D. A.; Horta, D.; Mészáros, S.; Monaco, L.; Monachesi, A.; Muñoz, R. R.; Brownstein, J.; Beers, T. C.; Lane, R. R.; Barbuy, B.; Sobeck, J.; Henao, L.; González-Díaz, D.; Miranda, R. E.; Reinarz, Y.; Santander, T. A.Context. Bulge globular clusters (BGCs) are exceptional tracers of the formation and chemodynamical evolution of this oldest Galactic component. However, until now, observational difficulties have prevented us from taking full advantage of these powerful Galactic archeological tools. Aims: CAPOS, the bulge Cluster APOgee Survey, addresses this key topic by observing a large number of BGCs, most of which have only been poorly studied previously. Even their most basic parameters, such as metallicity, [α/Fe], and radial velocity, are generally very uncertain. We aim to obtain accurate mean values for these parameters, as well as abundances for a number of other elements, and explore multiple populations. In this first paper, we describe the CAPOS project and present initial results for seven BGCs. Methods: CAPOS uses the APOGEE-2S spectrograph observing in the H band to penetrate obscuring dust toward the bulge. For this initial paper, we use abundances derived from ASPCAP, the APOGEE pipeline. Results: We derive mean [Fe/H] values of −0.85 ± 0.04 (Terzan 2), −1.40 ± 0.05 (Terzan 4), −1.20 ± 0.10 (HP 1), −1.40 ± 0.07 (Terzan 9), −1.07 ± 0.09 (Djorg 2), −1.06 ± 0.06 (NGC 6540), and −1.11 ± 0.04 (NGC 6642) from three to ten stars per cluster. We determine mean abundances for eleven other elements plus the mean [α/Fe] and radial velocity. CAPOS clusters significantly increase the sample of well-studied Main Bulge globular clusters (GCs) and also extend them to lower metallicity. We reinforce the finding that Main Bulge and Main Disk GCs, formed in situ, have [Si/Fe] abundances slightly higher than their accreted counterparts at the same metallicity. We investigate multiple populations and find our clusters generally follow the light-element (anti)correlation trends of previous studies of GCs of similar metallicity. We finally explore the abundances of the iron-peak elements Mn and Ni and compare their trends with field populations. Conclusions: CAPOS is proving to be an unprecedented resource for greatly improving our knowledge of the formation and evolution of BGCs and the bulge itself....
- ItemNew type II Cepheids from VVV data towards the Galactic center(2019) Braga, V. F.; Contreras Ramos, Rodrigo; Minniti, D.; Ferreira Lopes, C. E.; Catelan, Márcio; Minniti, J. H.; Nikzat, F.; Zoccali, M.Context. The Galactic center (GC) is the densest region of the Milky Way. Variability surveys towards the GC potentially provide the largest number of variable stars per square degree within the Galaxy. However, high stellar density is also a drawback due to blending. Moreover, the GC is affected by extreme reddening, therefore near infrared observations are needed. Aims: We plan to detect new variable stars towards the GC, focusing on type II Cepheids (T2Cs) which have the advantage of being brighter than RR Lyrae stars. Methods: We perform parallel Lomb-Scargle and Generalized Lomb-Scargle periodogram analysis of the Ks-band time series of the VISTA variables in the Vía Láctea survey, to detect periodicities. We employ statistical parameters to clean our sample. We take account of periods, light amplitudes, distances, and proper motions to provide a classification of the candidate variables. Results: We detected 1019 periodic variable stars, of which 164 are T2Cs, 210 are Miras and 3 are classical Cepheids. We also found the first anomalous Cepheid in this region. We compare their photometric properties with overlapping catalogs and discuss their properties on the color-magnitude and Bailey diagrams. Conclusions: We present the most extensive catalog of T2Cs in the GC region to date. Offsets in E(J - Ks) and in the reddening law cause very large (∼1-2 kpc) uncertainties on distances in this region. We provide a catalog which will be the starting point for future spectroscopic surveys in the innermost regions of the Galaxy. Full Tables 2 and 3 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/625/A151....
- ItemRecovering Algol-type eclipsing binaries in the CRTS(2020) Carmo, A.; Ferreira Lopes, C. E.; Papageorgiou, A.; Jablonski, F. J.; Rodrigues, C. V.; Drake, A. J.; Cross, N. J. G.; Catelan , MarcioEclipsing binary systems are relevant to astronomy since they provide primary means of determining fundamental stellar astrophysical quantities such as mass, radius, and temperature of the components. Algol-type eclipsing binaries (EAs) have spherical or slightly ellipsoidal components and are generally systems that produce light curves with narrow eclipses and few points within the eclipse. The most current photometric surveys usually have observation cadences larger than these eclipses duration, which hinders the detection of EAs. The variability of these objects can even be detected, but the period is rarely found because an optimized constraint is required. Thereby, we used a new methodology to find new EAs in the Catalina Real-Time Transient Survey. As a result, we determined periodicity for 56\% of EA$_\mathrm{up}$ (EAs marked as having unknown period), which corresponds to 87 new EAs reported. Also, we use color criteria to select a subsample that contains 8 low-mass binary systems with spectral types K and M. To obtain the individual physical parameters of these components, each light curve was modeled with the Wilson & Devinney light curve synthesis code combined with a Monte Carlo Markov chain process. The results were examined in the scenario of radius inflation of low-mass stars in binary systems....
- ItemRecovering variable stars in large surveys: EAup Algol-type class in the Catalina Survey(OUP, 2020) Carmo, A.; Ferreira Lopes, C. E.; Papageorgiou, A.; Jablonski, F. J.; Rodrigues, C. V.; Drake, A. J.; Cros, N. J. G.; Catelan, MárcioThe discovery and characterization of Algol eclipsing binaries (EAs) provide an opportunity to contribute for a better picture of the structure and evolution of low-mass stars. However, the cadence of most current photometric surveys hinders the detection of EAs since the separation between observations is usually larger than the eclipse(s) duration and hence few measurements are found at the eclipses. Even when those objects are detected as variable, their periods can be missed if an appropriate oversampling factor is not used in the search tools. In this paper, we apply this approach to find the periods of stars catalogued in the Catalina Real-Time Transient Survey (CRTS) as EAs having unknown period (EA up ). As a result, the periods of ∼56percent of them were determined. Eight objects were identified as low-mass binary systems and modelled with the Wilson & Devinney synthesis code combined with a Markov chain Monte Carlo optimization procedure. The computed masses and radii are in agreement with theoretical models and show no evidence of inflated radii. This paper is the first of a series aiming to identify suspected binary systems in large surveys.
- ItemRotation period distribution of CoRoT and Kepler Sun-like stars(2015) Leao, I. C.; Pasquini, L.; Ferreira Lopes, C. E.; Neves, V.; Valcarce Bravo, Aldo Alfonso Raúl; De Oliveira, L. L. A.; Freire da Silva, D.; De Freitas, D. B.; Canto Martins, B. L.; Janot Pacheco, E.; Baglin, A.; De Medeiros, J. R.
- ItemStellar cycles from photometric data : CoRoT stars(2015) Ferreira Lopes, C. E.; Leao, I. C.; De Freitas, D. B.; Canto Martins, B. L.; Catelan, Márcio; De Medeiros, J. R.
- ItemStellar parameters for stars of the CoRoT exoplanet field(2015) Cortés, C.; Maciel, S. C.; Vieira, S.; Ferreira Lopes, C. E.; Leão, I. C.; De Oliveira, G. P.; Correia, C.; Canto Martins, B. L.; Catelan, Márcio; De Medeiros, J. R.
- ItemStellar variability in the VVV survey(2013) Catelan, Márcio; Minniti, D.; Lucas, P. W.; Dékány, I.; Saito, R. K.; Angeloni, Rodolfo; Alonso-García, J.; Hempel, M.; Helminiak, Krzysztof Grzegorz; Jordán, A.; Contreras Ramos, Rodrigo Andrés; Navarrete, C.; Beamin Muhlenbrock, Juan Carlos; Rojas, A. F.; Gran, F.; Ferreira Lopes, C. E.; Contreras Peña, Carlos Eduardo; Kerins, E.; Huckvale, L.; Rejkuba, M.; Cohen, R.; Mauro, F.; Borissova, J.; Amigo, P.; Eyheramendy Duerr, Susana; Pichara Baksai, Karim Elías; Espinoza, N.; Navarro, C.; Hajdu, G.; Calderón Espinoza, Diego Nicolás; Muro, G. A.; Andrews, H.; Motta, V.; Kurtev, R.; Emerson, J. P.; Moni Bidin, C.; Chené, A. -N.The Vista Variables in the Via Lactea (VVV) ESO Public Survey is an ongoing time-series, near-infrared (IR) survey of the Galactic bulge and an adjacent portion of the inner disk, covering 562 square degrees of the sky, using ESOs VISTA telescope. The survey has provided superb multi-color photometry in 5 broadband filters ($Z$, $Y$, $J$, $H$, and $K_s$), leading to the best map of the inner Milky Way ever obtained, particularly in the near-IR. The main variability part of the survey, which is focused on $K_s$-band observations, is currently underway, with bulge fields having been observed between 31 and 70 times, and disk fields between 17 and 36 times. When the survey is complete, bulge (disk) fields will have been observed up to a total of 100 (60) times, providing unprecedented depth and time coverage. Here we provide a first overview of stellar variability in the VVV data, including examples of the light curves that have been collected thus far, scientific applications, and our efforts towards the automated classification of VVV light curves....
- ItemStellar variability in the VVV survey: overview and first results(2013) Catelan, Márcio; Minniti, D.; Lucas, P. W.; Dékány, I.; Saito, R. K.; Angeloni, Rodolfo; Alonso-García, J.; Hempel, M.; Hełminiak, K.; Jordán, A.; Contreras Ramos, Rodrigo Andrés; Navarrete, C.; Beamin Muhlenbrock, Juan Carlos; Rojas, A. F.; Gran, F.; Ferreira Lopes, C. E.; Contreras Peña, Carlos Eduardo; Kerins, E.; Huckvale, L.; Rejkuba, M.; Cohen, R.; Mauro, F.; Borissova, J.; Amigo, P.; Eyheramendy Duerr, Susana; Pichara Baksai, Karim Elías; Espinoza, N.; Navarro, C.; Hajdu, G.; Calderón Espinoza, Diego Nicolás; Muro, G. A.; Andrews, H.; Motta, V.; Kurtev, R.; Emerson, J. P.; Moni Bidin, C.; Chené, A. -N.The Vista Variables in the Vía Láctea (VVV) ESO Public Survey is an ongoing time-series, near-infrared (IR) survey of the Galactic bulge and an adjacent portion of the inner disk, covering 562 square degrees of the sky, using ESOs VISTA telescope. The survey has provided superb multi-color photometry in 5 broadband filters (Z, Y, J, H, and K<SUB>s</SUB> ), leading to the best map of the inner Milky Way ever obtained, particularly in the near-IR. The main part of the survey, which is focused on the variability in the K<SUB>s</SUB> -band, is currently underway, with bulge fields observed between 34 and 73 times, and disk fields between 34 and 36 times. When the survey is complete, bulge (disk) fields will have been observed up to a total of 100 (60) times, providing unprecedented depth and time coverage in the near-IR. Here we provide a first overview of stellar variability in the VVV data....
- ItemThe rotational behavior of Kepler Stars with Planets(2015) Chinchón, F. Paz; Leão, I. C.; Bravo, J. P.; Freitas, D. B. de; Ferreira Lopes, C. E.; Alves, S.; Catelan, Márcio; Canto Martins, B. L.; De Medeiros, J. R.
- ItemThe VVV survey: Long-period variable stars. I. Photometric catalog of ten VVV/OGLE tiles(2022) Nikzat, F.; Ferreira Lopes, C. E.; Catelan, Marcio; Contreras Ramos, R.; Zoccali, M.; Rojas-Arriagada, A.; Braga, V. F.; Minniti, D.; Borissova, J.; Becker, I.Context. Long-period variable stars (LPVs) are pulsating red giants, primarily in the asymptotic giant branch phase, and they include both Miras and semi-regular variables (SRVs). Their period-age and period-luminosity relations enable us to trace different stellar populations, as they are intrinsically very bright and cover a wide range in distances and ages. Aims: The purpose of this study is to establish a census of LPV stars in a region close to the Galactic center, using the six-year database of the Vista Variables in the Vía Láctea (VVV) ESO Public Survey, as well as to describe the methodology that was employed to search for and characterize LPVs using VVV data. Near-IR surveys such as VVV provide a unique opportunity to probe the high-extinction innermost regions of the Milky Way. The detection and analysis of the intrinsically bright Miras in this region could provide us with an excellent probe of the properties of the Milky Way far behind its bulge. Methods: We used point-spread function photometry for all available Ks-band images in ten VVV tiles, covering 16.4 deg2 in total, overlapping fields observed in the course of the Optical Gravitational Lensing Experiment (OGLE)-III survey. We designed a method to select LPV candidates, and we used the known variables from OGLE-III and other known variables from the literature to test our approach. The reduced χ2 statistic, along with the flux-independent index K(fi), were used in our analysis. The Lomb-Scargle period search method, Fourier analysis, template fitting, and visual inspection were then performed to refine our sample and characterize the properties of the stars included in our catalog. Results: A final sample of 130 Mira candidates, of which 129 are new discoveries, was thus obtained, with periods in the range between about 80 and 1400 days. Moreover, a sample of 1013 LPV candidates is also presented, whose periods are however not sufficiently constrained by the available data. A fraction of the latter may eventually turn out to be SRVs. Ages are measured for these stars based on a reassessment of the period-age relations available in the literature. The Miras in our catalog include 18 stars satisfying the requirements to serve as reliable distance indicators and which are not saturated in the VVV Ks-band images. Their distances are accordingly derived and discussed. A number of objects that are seemingly placed far behind the Milky Way's bulge was detected. Fulll Tables A.1 and B.2 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/660/A35...
- ItemThe WFCAM multiwavelength Variable Star Catalog (Corrigendum)(2015) Ferreira Lopes, C. E.; Dékány, I.; Catelan, Marcio; Cross, N. J. G.; Angeloni, R.; Leão, I. C.; De Medeiros, J. R.
- ItemVVV survey near-infrared colour catalogue of known variable stars(2021) Herpich, F. R.; Ferreira Lopes, C. E.; Saito, R. K.; Minniti, D.; Ederoclite, A.; Ferreira, T. S.; Catelan, MarcioContext. The Vista Variables in the Via Lactea (VVV) near-infrared variability survey explores some of the most complex regions of the Milky Way bulge and disk in terms of high extinction and high crowding. Aims: We add a new wavelength dimension to the optical information available at the American Association of Variable Star Observers International Variable Star Index (VSX-AAVSO) catalogue to test the VVV survey near-infrared photometry to better characterise these objects. Methods: We cross-matched the VVV and the VSX-AAVSO catalogues along with Gaia Data Release 2 photometry and parallax. Results: We present a catalogue that includes accurate individual coordinates, near-infrared magnitudes (ZYJHKs), extinctions AKs, and distances based on Gaia parallaxes. We also show the near-infrared CMDs and spatial distributions for the different VSX types of variable stars, including important distance indicators, such as RR Lyrae, Cepheids, and Miras. By analysing the photometric flags in our catalogue, we found that about 20% of the stars with measured and verified variability are flagged as non-stellar sources, even when they are outside of the saturation and/or noise regimes. Additionally, we pair-matched our sample with the VIVA catalogue and found that more than half of our sources are missing from the VVV variability list, mostly due to observations with low signal-to-noise ratio or photometric problems with a low percentage due to failures in the selection process. Conclusions: Our results suggest that the current knowledge of the variability in the Galaxy is biased to nearby stars with low extinction. The present catalogue also provides the groundwork for characterising the results of future large variability surveys such as the Vera C. Rubin Observatory Legacy Survey of Space and Time in the highly crowded and reddened regions of the Galactic plane, as well as follow-up campaigns for characterising specific types of variables. The analysis of the incorrectly flagged stars can be used to improve the photometric classification of the VVV data, allowing us to expand the amount of data considered useful for science purposes. In addition, we provide a list of stars that are missed by the VIVA procedures for which the observations are good and which were missed due to some failure in the VIVA selection process. Data used in this work is fully and only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/647/A169 Based on observations taken within the ESO Public Survey, Programme IDs 179.B-2002....