Examinando por Autor "Benetti, Stefano"

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    High-density circumstellar interaction in the luminous type IIn SN 2010jl: The first 1100 days
    (Institute of Physics Publishing, 2014) Fransson, Claes; Ergon, Mattias; Challis, Peter J.; Chevalier, Roger A.; France, Kevin; Kirshner, Robert P.; Marion G., H.; Milisavljevic, Dan; Smith, Nathan; Bufano, Filomena; Friedman, Andrew S.; Kangas, Tuomas; Larsson, Josefin; Mattila, Seppo; Benetti, Stefano; Chornock, Ryan; Czekala, Ian; Soderberg, Alicia; Sollerman, Jesper
    Hubble Space Telescope and ground-based observations of the Type IIn supernova (SN) 2010jl are analyzed, including photometry and spectroscopy in the ultraviolet, optical, and near-IR bands, 26-1128 days after first detection. At maximum, the bolometric luminosity was ∼ 3 × 1043 erg s-1 and even at 850 days exceeds 1042 erg s-1. A near-IR excess, dominating after 400 days, probably originates in dust in the circumstellar medium (CSM). The total radiated energy is ≳ 6.5 × 1050 erg, excluding the dust component. The spectral lines can be separated into one broad component that is due to electron scattering and one narrow with expansion velocity ∼ 100 km s-1 from the CSM. The broad component is initially symmetric around zero velocity but becomes blueshifted after ∼50 days, while remaining symmetric about a shifted centroid velocity. Dust absorption in the ejecta is unlikely to explain the line shifts, and we attribute the shift instead to acceleration by the SN radiation. From the optical lines and the X-ray and dust properties, there is strong evidence for large-scale asymmetries in the CSM. The ultraviolet lines indicate CNO processing in the progenitor, while the optical shows a number of narrow coronal lines excited by the X-rays. The bolometric light curve is consistent with a radiative shock in an r-2 CSM with a mass-loss rate of M ∼ 0.1 M⊙ yr-1. The total mass lost is ≳3 M⊙. These properties are consistent with the SN expanding into a CSM characteristic of a luminous blue variable progenitor with a bipolar geometry. The apparent absence of nuclear processing is attributed to a CSM that is still opaque to electron scattering. © 2014. The American Astronomical Society. All rights reserved.
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    Multi-wavelength observations of supernova 2011ei: time-dependent classification of type iib and ib supernovae and implications for their progenitors
    (2012) Milisavljevic, Dan; Margutti, Raffaella; Soderberg, Alicia M.; Pignata, Giuliano; Chomiuk, Laura; Fesen, Robert A.; Bufano, Filomena; Sanders, Nathan E.; Parrent, Jerod T.; Parker, Stuart; Pickering, Timothy; Buckley, David A. H.; Crawford, Steven M.; Gulbis, Amanda A. S.; Hettlage, Christian; Hooper, Eric; Nordsieck, Kenneth H.; O'Donoghue, Darragh; Husser, Tim-Oliver; Potter, Stephen; Kniazev, Alexei; Kotze, Paul; Romero-Colmenero, Encarni; Vaisanen, Petri; Wolf, Marsha; Bartel, Norbert; Bietenholz, Michael F.; Fransson, Claes; Mazzali, Paolo; Brunthaler, Andreas; Chakraborti, Sayan; Levesque, Emily M.; MacFayden, Andrew; Drescher, Colin; Bock, Greg; Marples, Peter; Anderson, Joseph P.; Benetti, Stefano; Reichart, Daniel; Ivarsen, Kevin
    We present X-ray, UV/optical, and radio observations of the stripped-envelope, core-collapse supernova (SN) 2011ei, one of the least luminous SNe IIb or Ib observed to date. Our observations begin with a discovery within 1 day of explosion and span several months afterward. Early optical spectra exhibit broad, Type II-like hydrogen Balmer profiles that subside rapidly and are replaced by Type Ib-like He-rich features on the timescale of one week. High-cadence monitoring of this transition identifies an absorption feature around 6250 °A to be chiefly due to hydrogen, as opposed to C II, Ne I, or Si II. Similarities between this observed feature and several SNe Ib suggest that hydrogen absorption attributable to a high velocity (& 12, 000 km s−1) H-rich shell is not rare in Type Ib events. Radio observations imply a shock velocity of v 0.13c and a progenitor star mass-loss rate of ˙M 1.4 × 10−5 M⊙ yr−1 (assuming wind velocity vw = 103 km s−1). This is consistent with independent constraints estimated from deep X-ray observations with Swift -XRT and Chandra. We find the multi-wavelength properties of SN2011ei to be consistent with the explosion of a lower-mass (3−4 M⊙), compact (R∗ 1×1011 cm), He core star. The star retained a thin hydrogen envelope at the time of outburst, and was embedded in an inhomogeneous circumstellar wind suggestive of modest episodic mass-loss. We conclude that SN2011ei’s rapid spectral metamorphosis calls attention to time-dependent classifications that bias estimates of explosion rates for a subset of Type IIb and Ib objects. Further, that important information about a progenitor star’s evolutionary state and associated mass-loss in the days to years prior to SN outburst can be inferred from timely multi-wavelength observations.
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    The Highly Energetic Expansion of SN2010bh Associated with GRB100316D
    (2012) Bufano, Filomena; Pian, Elena; Sollerman, Jesper; Benetti, Stefano; Pignata, Giuliano; Valenti, Stefano; Covino, Stefano; D’Avanzo, Paolo; Malesani, Daniele; Enrico, Cappellaro; Della Valle, Massimo; Fynbo, Johan; Hjorth, Jens; Mazzali, Paolo A.; Reichart, Daniel E.; Starling, Rhaana L. C.; Turatto, Massimo; Vergani, Susanna D.; Wiersema, Klass; Amati, Lorenzo; Bersier, David; Campana, Sergio; Cano, Zach; Castro-Tirado, Alberto J.; Chincarini, Guido; D’Elia, Valerio; de Ugarte, Antonio; Postigo, Deng, Jinsong; Ferrero, Patrizia; Alexei V., Filippenko; Goldoni, Paolo; Gorosabel, Javier; Greiner, Jochen; Hammer, Francois; Jakobsson, Pall; Kaper, Lex; Kawabata, Koji S.; Klose, Sylvio; Levan, Andrew J.; Maeda, Keiichi; Masetti, Nicola; Milvang-Jensen, Bo; Mirabel, Felix I.; Moller, Palle; Nomoto, Ken’ichi; Palazzi, Eliana; Piranomonte, Silvia; Salvaterra, Ruben; Stratta, Giulia; Tagliaferri, Gianpiero; Tanaka, Masaomi; Tanvir, Nial R.; Wijers, Ralph A.M.J.
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    The Type IIn Supernova SN 2010bt: The Explosion of a Star in Outburst
    (Institute of Physics Publishing, 2018-06) Elias-Rosa, Nancy; Van Dyk, Schuyler D.; Benetti, Stefano; Cappellaro, Enrico; Smith, Nathan; Kotak, Rubina; Turatto, Massimo; Filippenko, Alexei V.; Pignata, Giuliano; Fox, Ori D.; Galbany, Lluis; González-Gaitán, Santiago; Miluzio, Matteo; Monard L.A.G.; Ergon, Mattias
    It is well known that massive stars (M > 8 M ) evolve up to the collapse of the stellar core, resulting in most cases in a supernova (SN) explosion. Their heterogeneity is related mainly to different configurations of the progenitor star at the moment of the explosion and to their immediate environments. We present photometry and spectroscopy of SN 2010bt, which was classified as a Type IIn SN from a spectrum obtained soon after discovery and was observed extensively for about 2 months. After the seasonal interruption owing to its proximity to the Sun, the SN was below the detection threshold, indicative of a rapid luminosity decline. We can identify the likely progenitor with a very luminous star (log L/L ≈ 7) through comparison of Hubble Space Telescope images of the host galaxy prior to explosion with those of the SN obtained after maximum light. Such a luminosity is not expected for a quiescent star, but rather for a massive star in an active phase. This progenitor candidate was later confirmed via images taken in 2015 (∼5 yr post-discovery), in which no bright point source was detected at the SN position. Given these results and the SN behavior, we conclude that SN 2010bt was likely a Type IIn SN and that its progenitor was a massive star that experienced an outburst shortly before the final explosion, leading to a dense H-rich circumstellar environment around the SN progenitor. © 2018. The American Astronomical Society. All rights reserved.