Examinando por Autor "Botticella, M. T."

Mostrando 1 - 3 de 3
  • Miniatura
    Ítem
    Extending the variability selection of active galactic nuclei in the W-CDF-S and SERVS/SWIRE region
    (EDP Sciences, 2020-02) Poulain, M.; Paolillo, M.; De Cicco, D.; Brandt, W.N; Bauer, , F. E.; Falocco, S.; Vagnetti, F.; Grado, A.; Ragosta, F.; Botticella, M. T.; Cappellaro, E.; Pignata, G.; Vaccar, M.; Schipani, P.; Covone, G.; Longo, G.; Napolitano, N. R.
    Context. Variability has proven to be a powerful tool to detect active galactic nuclei (AGN) in multi-epoch surveys. The new-generation facilities expected to become operational in the next few years will mark a new era in time-domain astronomy and their wide-field multi-epoch campaigns will favor extensive variability studies. Aims. We present our analysis of AGN variability in the second half of the VST survey of the Wide Chandra Deep Field South, performed in the r band and covering a 2 sq. deg area. The analysis complements a previous work, in which the first half of the area was investigated. We provide a reliable catalog of variable AGN candidates, which will be critical targets in future variability studies. Methods. We selected a sample of optically variable sources and made use of infrared data from the Spitzer mission to validate their nature by means of color-based diagnostics. Results. We obtain a sample of 782 AGN candidates among which 12 are classified as supernovae, 54 as stars, and 232 as AGN. We estimate a contamination 20% and a completeness ∼38% with respect to mid-infrared selected samples. © ESO 2020.
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    Ítem
    Intermediate-luminosity red transients: Spectrophotometric properties and connection to electron-capture supernova explosions
    (EDP Sciences, 2021-10-01) Cai, Y.-Z.; Pastorello, A.; Fraser, M.; Botticella, M. T.; Elias-Rosa, N.; Wang, L.-Z.; Kotak, R.; Benetti, S.; Cappellaro, E.; Turatto, M.; Reguitti, A.; Mattila, S.; Smartt, S. J.; Ashall, C.; Benitez, S.; Chen, T.-W.; Harutyunyan, A.; Kankare, E.; Lundqvist, P.; Mazzali, P. A.; Morales-Garoffolo, A.; Ochner, P.; Pignata, G.; Prentice, S. J.; Reynolds, T. M.; Shu, X.-W.; Stritzinger, M. D.; Tartaglia, L.; Terreran, G.; Tomasella, L.; Valenti, S.; Valerin, G.; Wang, G.-J.; Wang, X.-F.; Borsato, L.; Callis, E.; Cannizzaro, G.; Chen, S.; Congiu, E.; Ergon, M.; Galbany, L.; Gal-Yam, A.; Gao, X.; Gromadzki, M.; Holmbo, S.; Huang, F.; Inserra, C.; Itagaki, K.; Kostrzewa-Rutkowska, Z.; Maguire, K.; Margheim, S.; Moran, S.; Onori, F.; Sagués Carracedo, A.; Smith, K. W.; Sollerman, J.; Somero, A.; Wang, B.; Young, D. R.
    We present the spectroscopic and photometric study of five intermediate-luminosity red transients (ILRTs), namely AT 2010dn, AT 2012jc, AT 2013la, AT 2013lb, and AT 2018aes. They share common observational properties and belong to a family of objects similar to the prototypical ILRT SN 2008S. These events have a rise time that is less than 15 days and absolute peak magnitudes of between-11.5 and-14.5 mag. Their pseudo-bolometric light curves peak in the range 0.5-9.0 × 1040 erg s-1 and their total radiated energies are on the order of (0.3-3) × 1047 erg. After maximum brightness, the light curves show a monotonic decline or a plateau, resembling those of faint supernovae IIL or IIP, respectively. At late phases, the light curves flatten, roughly following the slope of the 56Co decay. If the late-time power source is indeed radioactive decay, these transients produce 56Ni masses on the order of 10-4 to 10-3 M⊙. The spectral energy distribution of our ILRT sample, extending from the optical to the mid-infrared (MIR) domain, reveals a clear IR excess soon after explosion and non-negligible MIR emission at very late phases. The spectra show prominent H lines in emission with a typical velocity of a few hundred km s-1, along with Ca II features. In particular, the [Ca II] λ7291,7324 doublet is visible at all times, which is a characteristic feature for this family of transients. The identified progenitor of SN 2008S, which is luminous in archival Spitzer MIR images, suggests an intermediate-mass precursor star embedded in a dusty cocoon. We propose the explosion of a super-asymptotic giant branch star forming an electron-capture supernova as a plausible explanation for these events.
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    LSQ13fn: A type II-Plateau supernova with a possibly low metallicity progenitor that breaks the standardised candle relation
    (EDP SCIENCES, 2016-04) Polshaw, J.; Kotak, R.; Dessart, L.; Fraser, M.; Gal-Yam, A.; Inserra, C.; Sim, S. A.; Smartt, S. J.; Sollerman, J.; Baltay, C.; Rabinowitz, D.; Benetti, S.; Botticella, M. T.; Campbell, H.; Chen, T.-W.; Galbany, L.; McKinnon, R.; Nicholl, M.; Smith, K. W.; Sullivan, M.; Takáts, K.; Valenti, S.; Young, D. R.
    We present optical imaging and spectroscopy of supernova (SN) LSQ13fn, a type II supernova with several hitherto-unseen properties. Although it initially showed strong symmetric spectral emission features attributable to He ii, N iii, and C iii, reminiscent of some interacting SNe, it transitioned into an object that would fall more naturally under a type II-Plateau (IIP) classification. However, its spectral evolution revealed several unusual properties: metal lines appeared later than expected, were weak, and some species were conspicuous by their absence. Furthermore, the line velocities were found to be lower than expected given the plateau brightness, breaking the SN IIP standardised candle method for distance estimates. We found that, in combination with a short phase of early-time ejecta-circumstellar material interaction, metal-poor ejecta, and a large progenitor radius could reasonably account for the observed behaviour. Comparisons with synthetic model spectra of SNe IIP of a given progenitor mass would imply a progenitor star metallicity as low as 0.1 Z⊙. LSQ13fn highlights the diversity of SNe II and the many competing physical effects that come into play towards the final stages of massive star evolution immediately preceding core-collapse.