Browsing by Author "Zorotovic, M."

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    Erratum: "The Globular Cluster NGC 5286. II. Variable Stars" (2010, AJ, 139, 357)
    (2010) Zorotovic, M.; Catelan, Márcio; Smith, H. A.; Pritzl, B. J.; Aguirre, P.; Angulo, R. E.; Aravena, M.; Assef, R. J.; Contreras, C.; Cortés, C.; De Martini, G.; Escobar, M. E.; González, D.; Jofré, P.; Lacerna, I.; Navarro, C.; Palma, O.; Prieto, G. E.; Recabarren, E.; Triviño, J.; Vidal, E.
    The Fourier decomposition program used in our paper contained a small error that affected the calculation of the temperatures as well as the V - I colors inferred for the RRab stars. The temperatures that appear in Table 6 in the published article are slightly overestimated, and the V - I colors underestimated. A corrected version of Table 6 is presented below....
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    THE GLOBULAR CLUSTER NGC 5286. I. A NEW CCD BV COLOR-MAGNITUDE DIAGRAM
    (2009) Zorotovic, M.; Catelan, M.; Zoccali, M.; Pritzl, B. J.; Smith, H. A.; Stephens, A. W.; Contreras, R.; Escobar, M. E.
    We present BV photometry of the Galactic globular cluster NGC 5286, based on 128 V frames and 133 B frames, and covering the entire face of the cluster. Our photometry reaches almost two magnitudes below the turn-off level, and is accordingly suitable for age analysis. Field stars were removed statistically from the cluster's color-magnitude diagram (CMD), and a differential reddening correction applied, thus allowing a precise ridgeline to be calculated. Using the latter, a metallicity of [Fe/H] = - 1.70 +/- 0.05 in the Zinn & West scale, and [Fe/H] = - 1.47 +/- 0.02 in the Carretta & Gratton scale, was derived on the basis of several parameters measured from the red giant branch, in good agreement with the value provided in the Harris catalog. Comparing the NGC 5286 CMD with the latest photometry for M3 by P. B. Stetson, and using VandenBerg isochrones for a suitable chemical composition, we find evidence that NGC 5286 is around 1.7 +/- 0.9 Gyr older than M3. This goes in the right sense to help account for the blue horizontal branch of NGC 5286, for which we provide a measurement of several morphological indicators. If NGC 5286 is a bona fide member of the Canis Major dwarf spheroidal galaxy, as previously suggested, our results imply that the latter's oldest components may be at least as old as the oldest Milky Way globular clusters.
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    The globular cluster NGC 5286: color-magnitude diagram and variable stars
    (2010) Zorotovic, M.; Catelan, Marcio; Zoccali, M.; Smith, H. A.; Pritzl, B. J.
    We present BV photometry and the results of a search for stellar variability in the globular cluster NGC 5286, which has tentatively been associated with the Canis Major dwarf spheroidal galaxy. Our results indicate an Oosterhoff type II for the cluster, which is unusual for an object of extragalactic origin....
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    The Oosterhoff Dichotomy in the Milky Way and Other Local Group Galaxies
    (2010) Smith, Horace A.; Catelan, Marcio; Clementini, G.; Kuehn, C.; Pritzl, B.; Beers, T.; De Lee, N.; Kinemuchi, K.; Greco, C.; Ripepi, V.; Marconi, M.; Musella, I.; Moretti, M. I.; Dall'Ora, M.; Contreras, R.; Zorotovic, M.
    In 1939, P. Th. Oosterhoff investigated the properties of RR Lyrae stars in five of the globular clusters of the Milky Way. He discovered that these clusters divided into two groups, now known as Oosterhoff groups I and II, on the basis of the properties of their RR Lyrae stars. Subsequent studies of RR Lyrae variables in additional globular clusters found that most Milky Way globular clusters that contain significant numbers of RR Lyrae stars fall into one or another of the two Oosterhoff groups. Moreover, globular clusters of Oosterhoff group I tend to be more metal-rich than those of Oosterhoff group II. However, the dwarf galaxies surrounding the Milky Way, and their globular clusters, do not exhibit the Oosterhoff dichotomy. Moreover, the bulge globular clusters NGC 6388 and NGC 6441 cannot be easily assigned to one of the traditional Oosterhoff groups. We will discuss the implications of the Oosterhoff dichotomy and the Oosterhoff gap for stellar evolution and for the formation and evolution of the Galactic halo. This work has been supported in part by the National Science Foundation....
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    The White Dwarf Binary Pathways Survey -III. Contamination from hierarchical triples containing a white dwarf
    (2020) Lagos, F.; Schreiber, M. R.; Parsons, S. G.; Zurlo, A.; Mesa, D.; Gansicke, B. T.; Brahm, R.; Caceres, C.; Canovas, H.; Hernandez, M-S; Jordan, A.; Koester, D.; Schmidtobreick, L.; Tappert, C.; Zorotovic, M.
    The White Dwarf Binary Pathways Survey aims at increasing the number of known detached A, F, G, and K main-sequence stars in close orbits with white dwarf companions (WD+AFGK binaries) to refine our understanding about compact binary evolution and the nature of Supernova Ia progenitors. These close WD+AFGK binary stars are expected to form through common envelope evolution, in which tidal forces tend to circularize the orbit. However, some of the identified WD+AFGK binary candidates show eccentric orbits, indicating that these systems are either formed through a different mechanism or perhaps they are not close WD+AFGK binaries. We observed one of these eccentric WD+AFGK binaries with SPHERE and find that the system TYC 7218-934-1 is in fact a triple system where the WD is a distant companion. The inner binary likely consists of the G-type star plus an unseen low-mass companion in an eccentric orbit. Based on this finding, we estimate the fraction of triple systems that could contaminate the WD+AFGK sample. We find that less than 15 per cent of our targets with orbital periods shorter than 100 d might be hierarchical triples.
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    WD 1856 b: a close giant planet around a white dwarf that could have survived a common envelope phase
    (2021) Lagos, F.; Schreiber, M. R.; Zorotovic, M.; Gansicke, B. T.; Ronco, M. P.; Hamers, Adrian S.
    The discovery of a giant planet candidate orbiting the white dwarf WD 1856+534 with an orbital period of 1.4 d poses the questions of how the planet reached its current position. We here reconstruct the evolutionary history of the system assuming common envelope evolution as the main mechanism that brought the planet to its current position. We find that common envelope evolution can explain the present configuration if it was initiated when the host star was on the asymptotic giant branch, the separation of the planet at the onset of mass transfer was in the range 1.69-2.35 au, and if in addition to the orbital energy of the surviving planet either recombination energy stored in the envelope or another source of additional energy contributed to expelling the envelope. We also discuss the evolution of the planet prior to and following common envelope evolution. Finally, we find that if the system formed through common envelope evolution, its total age is in agreement with its membership to the Galactic thin disc. We therefore conclude that common envelope evolution is at least as likely as alternative formation scenarios previously suggested such as planet-planet scattering or Kozai-Lidov oscillations.