Browsing by Author "Catelan , Marcio"
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- ItemA large and homogeneous sample of SX Phe stars in the Fornax dwarf spheroidal galaxy .(2006) Poretti, E.; Dell'Arciprete, L.; Clementini, G.; Held, E. V.; Greco, C.; Gullieuszik, M.; Maio, M.; Rizzi, L.; Catelan , Marcio; Smith, H. A.; Pritzl, B.; De Lee, N.; Rest, A.We report on the detection of sixty-one SX Phe stars in the Fornax dwarf spheroidal galaxy using the Wide-Field Imager at the 2.2m ESO-MPI telescope. In spite of their extreme faintness (22.0...
- ItemA new age-metallicity relation for galactic globular clusters in the alpha-enhanced scenario : cosmological implications.(1992) Catelan , Marcio; de Freitas Pacheco, J. A.Results of an exploratory analysis of the suggestion of Straniero (1991) to obtain, through the Delta(V) method, an age-metallicity for Galactic globular clusters in the alpha-enhanced scenario are presented. A new lower limit is derived for the age of the universe (about 17 Gyr). This value is discussed in the light of other observational constraints in the Hubble parameter-density parameter plane....
- ItemA new search for R Coronae Borealis stars in the SMC(2017) Nikzat, Fatemeh; Catelan , MarcioR Coronae Borealis (RCB) stars are rare, and their evolutionary origin is not well understood. Since they are obscured due to formation of carbon dust around the star during their mass loss events, RCB stars can be classified as self-eclipsing variable stars. The purpose of this work is to present a new search for RCB stars in the Small Magellanic Cloud (SMC), by analysing VI data from the OGLE project....
- ItemA revised view of the Canis Major stellar overdensity with DECam and Gaia: new evidence of a stellar warp of blue stars(2020) Julio A Carballo-Bello; David Martínez-Delgado; Jesús M Corral-Santana; Emilio J Alfaro; Camila Navarrete; A Katherina Vivas; Catelan , Marcio
- ItemA Search for EHB Pulsators in the Globular Cluster NGC 6752(2007) Catelan , Marcio; Prieto, G. E.; Zoccali, M.; Weidner, C.; Stetson, P. B.; Moni Bidin, C.; Altmann, M.; Smith, H. A.; Pritzl, B. J.; Borissova, J.; de Medeiros, J. R.We describe the status of a project whose main goal is to detect variability along the extreme horizontal branch of the globular cluster NGC 6752. Based on Magellan 6.5-m data, preliminary light curves are presented for some candidate variables. By combining our time-series data, we also produce a deep CMD of unprecedented quality for the cluster which reveals a remarkable lack of main sequence binaries, possibly pointing to a low primordial binary fraction....
- ItemA Segmented Period-Luminosity Relation for Nearby Extragalactic Delta Scuti Stars(2022) Martínez-Vázquez, C. E.; Salinas, R.; Vivas, A. K.; Catelan , MarcioThe period-luminosity relations (PLRs) of Milky Way δ Scuti (δ Sct) stars have been described to the present day by a linear relation. However, when studying extragalactic systems such as the Magellanic Clouds and several dwarf galaxies, we notice for the first time a nonlinear behavior in the PLR of δ Sct stars. Using the largest sample of ~3700 extragalactic δ Sct stars from data available in the literature-mainly based on the Optical Gravitational Lensing Experiment and the Super MAssive Compact Halo Object project in the Large Magellanic Cloud (LMC)-we obtain that the best fit to the period-luminosity (M V ) plane is given by the following piecewise linear relation with a break at logP = -1.03 ± 0.01 (or 0.093 ± 0.002 days) for shorter periods (sp) and longer periods (lp) than the break-point:...
- ItemA Speckle Interferometric Search for a Companion to the RR Lyrae Star UV Oct(2020) R. Salinas; G. Hajdu; Z. Prudil; S. Howell; Catelan , Marcio
- ItemA Study of the Newly Discovered Rapid sdO Pulsators in ω Centauri(2012) Randall, S. K.; Fontaine, G.; Calamida, A.; Brassard, P.; Chayer, P.; Alonso, M. L.; Catelan , Marcio; Bono, G.; Green, E. M.; Dhillon, V. S.; Marsh, T. R.We summarise recent observational and modelling results obtained for the newly discovered rapid sdO pulsators in ω Centauri. At present, these variables have no counterpart among the field star population, and the extent and purity of the associated instability strip is not yet well defined. First non-adiabatic computations indicate that the pulsations observed are driven by the same κ-mechanism that has been invoked to explain the oscillations in the extensively studied field sdB pulsators. The ω Cen variables appear to show only a small number of independent modes down to the currently achievable detection threshold and there is evidence for significant amplitude variations over time. It remains to be seen whether these objects can be exploited for asteroseismology in the near future; this will certainly be challenging both from an observational and a modelling point of view....
- ItemA Supernova Candidate from the Siding Spring Survey(2010) Drake, A. J.; Djorgovski, S. G.; Mahabal, A. A.; Graham, M. J.; Williams, R.; Prieto, J.; Catelan , Marcio; Christensen, E.; McNaught, R.; Garradd, G.; Beshore, E. C.; Larson, S. M.We report the discovery of the first supernova candidate from the Siding Spring Survey (SSS) by the Catalina Real-time Transient Survey (CRTS). The detection has the following details: <table border=1 width=650 align=center> <tr><th>ID</th><th>Disc. Date</th><th>RA</th><th>Dec</th><th>Disc. Mag</th></tr> <tr align=center><td><a href='http://crts.caltech.edu/ATEL/SSS/1005080151534122262.atel.html'> SSS100508:210144-143830</a></td><td> 2010-05-08 </td><td> 21:01:44.10 </td><td> -14:38:30.5 </td><td> 16.4</tr> </table> The host galaxy, 2MFGC 15924 (=PGC 187888), has redshift z=0.0275 (Jones et al....
- ItemA survey of hot subdwarf pulsators in ω Cen(2013) Randal, S. K.; Calamida, A.; Fontaine, G.; Green, E. M.; Monelli, M.; Alonso, M. L.; Catelan , Marcio; Bono, G.; Dhillon, V. S.; Marsh, T. R.We recently discovered an apparently new class of pulsating Extreme Horizontal Branch (EHB) star in ω Cen. Tightly clustered around ∼50,000 K, these H-rich sdO stars exhibit rapid, multi-periodic oscillations on a timescale of 100 s. While four such objects have been detected in ω Cen, no counterparts have yet been found among the field population. Conversely, the rapid sdB pulsators around 31,000 K that are well-studied in the Galactic field have yet to be found in a globular cluster. We discuss the implications of this and also report the discovery of a fifth EHB pulsator in ω Cen....
- ItemA Unique Low-mass-ratio Contact Eclipsing Binary System under the Period Cutoff(2023) Athanasios Papageorgiou; Panagiota-Eleftheria Christopoulou; Eleni Lalounta; C. E. Ferreira Lopes; Catelan , Marcio; Andrew J. Drake; Panayiotis Ηantzios; Ioannis Alikakos
- ItemPulsating Hot Subdwarfs in Omega Centauri(2016) Randall, S. K.; Calamida, A.; Fontaine, G.; Monelli, M.; Bono, G.; Alonso, M. L.; Van Grootel, V.; Brassard, P.; Chayer, P.; Catelan , Marcio; Littlefair, S.; Dhillon, V. S.; Marsh, T. R.We recently discovered the first globular cluster hot subdwarf pulsators in Omega Centauri (ω Cen). These stars were initially thought to belong to the class of rapidly pulsating subdwarf B stars, which are well established among the field star population and have become showcases for asteroseismology. However, our spectroscopic analysis revealed the ω Cen variables to be significantly hotter than expected, indicating that they form a new class of subdwarf O pulsators clustered around 50 000 K, not known among the field star population. Non-adiabatic pulsation modelling suggests that the driver for the pulsations occurs via the same iron opacity mechanism that is at work in the rapidly pulsating subdwarf B stars....
- 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....
- ItemReddening-Free Indices in the VISTA Filter System(2014) Catelan , Marcio; Leyton, P. P.; Saito, R. K.; Borissova, J.; Popescu, B.Reddening-free indices represent a powerful, and yet little used, approach to problems where reddening/extinction constitute a serious issue, without having to deal with the extinction of any individual star. Here we report on our progress in obtaining reddening-free indices, in the VISTA filter system....
- ItemRGB Properties of the LMC/SMC Clusters in the Infrared(2009) Kurtev, Radostin; Ivanov, Valentin; Borissova, Jura; Catelan , Marcio; Geisler, Douglas
- ItemRR Lyrae stars in M31 globular clusters: B514(2008) Contreras, R.; Federici, L.; Clementini, G.; Cacciari, C.; Merighi, R.; Kinemuchi, K.; Catelan , Marcio; Fusi Pecci, F.; Marconi, M.; Pritzl, B.; Smith, H.We present preliminary results of a variable star search in the metal-poor globular cluster B514 of the Andromeda galaxy (M31), based on Hubble Space Telescope Wide Field Planetary Camera 2 and Advanced Camera for Surveys observations. A large number of RR Lyrae stars have been identified for the first time in a globular cluster of M31. The average period of the RR Lyrae variables (< Pab > = 0.58 days and < Pc > = 0.35 days, for fundamental-mode and first-overtone pulsators, respectively) and the position in the period-amplitude diagram both suggest that B514 is likely an Oosterhoff I cluster, contrary to the general behaviour of the metal-poor globular clusters in the Milky Way, which show instead Oosterhoff type II pulsation properties....
- ItemRR Lyrae stars in omega Centauri: Near-IR properties and period-luminosity relations(2016) Navarrete, C.; Catelan , Marcio; Contreras Ramos, R.; Gran, F.; Alonso-Garcia, J.Omega Centauri contains a rich harvest of variable stars. Here we report on a deep, wide-field, near-infrared (IR) variability survey for this cluster, carried out using ESO's 4.1m VISTA telescope. Our time-series data includes more than 180 RR Lyrae light curves in both J and Ks, allowing us to derive an unprecedented homogeneous and complete near-IR catalog of RR Lyrae in the field of omega Cen. Near-IR period-luminosity relations are derived and used to determine an updated (pulsational) distance modulus for the cluster....
- ItemSemi-Empirical Determination of the Mass Distribution of Horizontal Branch Stars in M3(2009) Valcarce, A.; Catelan , MarcioWe determine, by means of a semi-empirical study, the masses of horizontal branch stars in the globular cluster M3 (NGC 5272). We used the most recent and reliable observational datasets (broadband BVI photometry) available for the cluster, both for variable and nonvariable stars, to infer the most likely masses of individual horizontal branch stars by comparison against theoretical evolutionary tracks, suitably transformed to the observational planes. We found a mass distribution that is adequately described by a Gaussian, with < M > = 0.64 M⊙ and σ = 0.020 M⊙....
- ItemSemi-supervised classification and clustering analysis for variable stars(2022) R Pantoja; Catelan , Marcio; K Pichara; P Protopapas
- ItemStudies of RR Lyrae Variables in Binary Systems. I. Evidence of a Trimodal Companion Mass Distribution(2021) Gergely Hajdu; Grzegorz Pietrzyński; Johanna Jurcsik; Catelan , Marcio; Paulina Karczmarek; Bogumił Pilecki; Igor Soszyński; Andrzej Udalski; Ian B. Thompson