Examinando por Autor "Benetti S."
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Ítem A long life of excess: The interacting transient SN 2017hcc(EDP Sciences, 2023-01) Moran S.; Fraser M.; Kotak R.; Pastorello A.; Benetti S.; Brennan S.J.; Gutiérrez C.P.; Kankare E.; Kuncarayakti H.; Mattila S.; Reynolds T.M.; Anderson J.P.; Brown P.J.; Campana S.; Chambers K.C.; Chen T.-W.; Della Valle M.; Dennefeld M.; Elias-Rosa N.; Galbany L.; Galindo-Guil F.J.; Gromadzki M.; Hiramatsu D.; Inserra C.; Leloudas G.; Müller-Bravo T.E.; Nicholl M.; Reguitti A.; Shahbandeh M.; Smartt S.J.; Tartaglia L.; Young D.R.In this study we present the results of a five-year follow-up campaign of the long-lived type IIn supernova SN 2017hcc, found in a spiral dwarf host of near-solar metallicity. The long rise time (57 ± 2 days, ATLAS o band) and high luminosity (peaking at -20.78 ± 0.01 mag in the ATLAS o band) point towards an interaction of massive ejecta with massive and dense circumstellar material (CSM). The evolution of SN 2017hcc is slow, both spectroscopically and photometrically, reminiscent of the long-lived type IIn, SN 2010jl. An infrared (IR) excess was apparent soon after the peak, and blueshifts were noticeable in the Balmer lines starting from a few hundred days, but appeared to be fading by around +1200 d. We posit that an IR light echo from pre-existing dust dominates at early times, with some possible condensation of new dust grains occurring at epochs ≳;+800 d. © The Authors 2023.Ítem A study in scarlet: I. Photometric properties of a sample of intermediate-luminosity red transients(EDP Sciences, 2025-03) Valerin G.; Pastorello A.; Reguitti A.; Benetti S.; Cai Y.-Z.; Chen T.-W.; Eappachen D.; Elias-Rosa N.; Fraser M.; Gangopadhyay A.; Hsiao E.Y.; Howell D.A.; Inserra C.; Izzo L.; Jencson J.; Kankare E.; Kotak R.; Mazzali P.A.; Misra K.; Pignata G.; Prentice S.J.; Sand D.J.; Smartt S.J.; Stritzinger M.D.; Tartaglia L.; Valenti S.; Anderson J.P.; Andrews J.E.; Amaro R.C.; Brennan S.; Bufano F.; Callis E.; Cappellaro E.; Dastidar R.; Della Valle M.; Fiore A.; Fulton M.D.; Galbany L.; Heikkilä T.; Hiramatsu D.; Karamehmetoglu E.; Kuncarayakti H.; Leloudas G.; Lundquist M.; Mccully C.; Müller-Bravo T.E.; Nicholl M.; Ochner P.; Padilla Gonzalez E.; Paraskeva E.; Pellegrino C.; Rau A.; Reichart D.E.; Reynolds T.M.; Roy R.; Salmaso I.; Singh M.; Turatto M.; Tomasella L.; Wyatt S.Aims. We investigate the photometric characteristics of a sample of intermediate-luminosity red transients (ILRTs), a class of elusive objects with peak luminosity between that of classical novae and standard supernovae. Our goal is to provide a stepping stone in the path to reveal the physical origin of such events, thanks to the analysis of the datasets collected. Methods. We present the multi-wavelength photometric follow-up of four ILRTs, namely NGC 300 2008OT-1, AT 2019abn, AT 2019ahd, and AT 2019udc. Through the analysis and modelling of their spectral energy distribution and bolometric light curves, we inferred the physical parameters associated with these transients. Results. All four objects display a single-peaked light curve which ends in a linear decline in magnitudes at late phases. A flux excess with respect to a single blackbody emission is detected in the infrared domain for three objects in our sample, a few months after maximum. This feature, commonly found in ILRTs, is interpreted as a sign of dust formation. Mid-infrared monitoring of NGC 300 2008OT-1 761 days after maximum allowed us to infer the presence of ∼10-3-10-5 M⊙ of dust, depending on the chemical composition and the grain size adopted. The late-time decline of the bolometric light curves of the considered ILRTs is shallower than expected for 56Ni decay, hence requiring an additional powering mechanism. James Webb Space Telescope observations of AT 2019abn prove that the object has faded below its progenitor luminosity in the mid-infrared domain, five years after its peak. Together with the disappearance of NGC 300 2008OT-1 in Spitzer images seven years after its discovery, this supports the terminal explosion scenario for ILRTs. With a simple semi-analytical model we tried to reproduce the observed bolometric light curves in the context of a few solar masses ejected at few 103 km s-1 and enshrouded in an optically thick circumstellar medium. © The Authors 2025.Ítem Hidden shock powering the peak of SN 2020faa(EDP Sciences, 2023) Salmaso I.; Cappellaro E.; Tartaglia L.; Benetti S.; Botticella M.T.; Elias-Rosa N.; Pastorello A.; Patat F.; Reguitti A.; Tomasella L; Valerin G.; Yang S.Context. The link between the fate of the most massive stars and the resulting supernova (SN) explosion is still a matter of debate, in major part because of the ambiguity among light-curve powering mechanisms. When stars explode as SNe, the light-curve luminosity is typically sustained by a central engine (radioactive decay, magnetar spin-down, or fallback accretion). However, since massive stars eject considerable amounts of material during their evolution, there may be a significant contribution coming from interactions with the previously ejected circumstellar medium (CSM). Reconstructing the progenitor configuration at the time of explosion requires a detailed analysis of the long-term photometric and spectroscopic evolution of the related transient. Aims. In this paper, we present the results of our follow-up campaign of SN 2020faa. Given the high luminosity and peculiar slow light curve, it is purported to have a massive progenitor. We present the spectro-photometric dataset and investigate different options to explain the unusual observed properties that support this assumption. Methods. We computed the bolometric luminosity of the supernova and the evolution of its temperature, radius, and expansion velocity. We also fit the observed light curve with a multi-component model to infer information on the progenitor and the explosion mechanism. Results. Reasonable parameters are inferred for SN 2020faa with a magnetar of energy, Ep = 1.5-0.2+0.5 × 1050 erg, and spin-down time, tspin = 15 ± 1 d, a shell mass, Mshell = 2.4-0.4+0.5 Mo, and kinetic energy, Ekin(shell) = 0.9-0.3+0.5 × 1051 erg, and a core with Mcore = 21.5-0.7+1.4 Mo and Ekin(core) = 3.9-0.4+0.1 × 1051 erg. In addition, we need an extra source to power the luminosity of the second peak. We find that a hidden interaction with either a CSM disc or several delayed and choked jets is a viable mechanism for supplying the required energy to achieve this effect. © The Authors 2023.Ítem Panning for gold, but finding helium: Discovery of the ultra-stripped supernova SN 2019wxt from gravitational-wave follow-up observations(EDP Sciences, 2023-07) Agudo I.; Amati L.; An T.; Bauer F.E.; Benetti S.; Bernardini M.G.; Beswick R.; Bhirombhakdi K.; De Boer T.; Branchesi M.; Brennan S.J.; Brocato E.; Caballero-García M.D.; Cappellaro E.; Castro Rodríguez N.; Castro-Tirado A.J.; Chambers K.C.; Chassande-Mottin E.; Chaty S.; Chen T.-W.; Coleiro A.; Covino S.; Da'ammando F.; Da'avanzo P.; Da'elia V.; Fiore A.; Flörs A.; Fraser M.; Frey S.; Frohmaier C.; Fulton M.; Galbany L.; Gall C.; Gao H.; García-Rojas J.; Ghirlanda G.; Giarratana S.; Gillanders J.H.; Giroletti M.; Gompertz B.P.; Gromadzki M.; Heintz K.E.; Hjorth J.; Hu Y.-D.; Huber M.E.; Inkenhaag A.; Izzo L.; Jin Z.P.; Jonker P.G.; Kann D.A.; Kool E.C.; Kotak R.; Leloudas G.; Levan A.J.; Lin C.-C.; Lyman J.D.; Magnier E.A.; Maguire K.; Mandel I.; Marcote B.; Mata Sánchez D.; Mattila S.; Mattila S.; Michaåà  Owski M.J.; Moldon J.; Nicholl M.; Nicuesa Guelbenzu A.; Oates S.R.; Onori F.; Orienti M.; Paladino R.; Paragi Z.; Perez-Torres M.; Pian E.; Pignata G.; Piranomonte S.; Quirola-Vásquez J.; Ragosta F.; Rau A.; Ronchini S.; Rossi A.; Sánchez-Ramírez R.; Salafia O.S.; Schulze S.; Smartt S.J.; Smith K.W.; Sollerman J.; Srivastav S.; Starling R.L.C.; Steeghs D.; Stevance H.F.; Tanvir N.R.; Testa V.; Torres M.A.P.; Valeev A.; Vergani S.D.; Vescovi D.; Wainscost R.; Watson D.; Wiersema K.; Wyrzykowski L.; Yang J.; Yang S.; Young D.R.We present the results from multi-wavelength observations of a transient discovered during an intensive follow-up campaign of S191213g, a gravitational wave (GW) event reported by the LIGO-Virgo Collaboration as a possible binary neutron star merger in a low latency search. This search yielded SN 2019wxt, a young transient in a galaxy whose sky position (in the 80% GW contour) and distance (∼150 Mpc) were plausibly compatible with the localisation uncertainty of the GW event. Initially, the transienta's tightly constrained age, its relatively faint peak magnitude (Mi ∼ -16.7 mag), and the r-band decline rate of ∼1 mag per 5 days appeared suggestive of a compact binary merger. However, SN 2019wxt spectroscopically resembled a type Ib supernova, and analysis of the optical-near-infrared evolution rapidly led to the conclusion that while it could not be associated with S191213g, it nevertheless represented an extreme outcome of stellar evolution. By modelling the light curve, we estimated an ejecta mass of only ∼0.1 M·, with 56Ni comprising ∼20% of this. We were broadly able to reproduce its spectral evolution with a composition dominated by helium and oxygen, with trace amounts of calcium. We considered various progenitor channels that could give rise to the observed properties of SN 2019wxt and concluded that an ultra-stripped origin in a binary system is the most likely explanation. Disentangling genuine electromagnetic counterparts to GW events from transients such as SN 2019wxt soon after discovery is challenging: in a bid to characterise this level of contamination, we estimated the rate of events with a volumetric rate density comparable to that of SN 2019wxt and found that around one such event per week can occur within the typical GW localisation area of O4 alerts out to a luminosity distance of 500 Mpc, beyond which it would become fainter than the typical depth of current electromagnetic follow-up campaigns. © 2023 AuthorsÍtem SN 2017gmr: An Energetic Type II-P Supernova with Asymmetries(Institute of Physics Publishing, 2019-11-01) Andrews, Jennifer E.; Sand D.J.; Valenti S.; Smith, Nathan; Dastidar, Raya; Sahu D.K.; Misra, Kuntal; Singh, Avinash; Hiramatsu D.; Brown P.J.; Hosseinzadeh G.; Wyatt S.; Vinko J.; Anupama G.C.; Arcavi I.; Ashall, Chris; Benetti S.; Berton, Marco; Bostroem K.A.; Bulla M.; Burke J.; Chen S.; Chomiuk L.; Cikota A.; Congiu E.; Cseh B.; Davis, Scott; Elias-Rosa N.; Faran T.; Fraser, Morgan; Galbany L.; Gall C.; Gal-Yam A.; Gangopadhyay, Anjasha; Gromadzki M.; Haislip J.; Howell D.A.; Hsiao E.Y.; Inserra C.; Kankare E.; Kuncarayakti H.; Kouprianov V.; Kumar, Brajesh; Li, Xue; Lin, Han; Maguire K.; Mazzali P.; McCully C.; Milne P.; Mo, Jun; Morrell N.; Nicholl M.; Ochner P.; Olivares F.; Pastorello A.; Patat F.; Phillips M.; Pignata G.; Prentice S.; Reguitti A.; Reichart D.E.; Rodríguez Ó.; Rui, Liming; Sanwal, Pankaj; Sárneczky K.; Shahbandeh M.; Singh, Mridweeka; Smartt S.; Strader J.; Stritzinger M.D.; Szakáts R.; Tartaglia L.; Wang, Huijuan; Wang, Lingzhi; Wang, Xiaofeng; Wheeler J.C.; Xiang, Danfeng; Yaron O.; Young D.R.; Zhang, JunboWe present high-cadence UV, optical, and near-infrared data on the luminous Type II-P supernova SN 2017gmr from hours after discovery through the first 180 days. SN 2017gmr does not show signs of narrow, high-ionization emission lines in the early optical spectra, yet the optical light-curve evolution suggests that an extra energy source from circumstellar medium (CSM) interaction must be present for at least 2 days after explosion. Modeling of the early light curve indicates a ∼500 R o progenitor radius, consistent with a rather compact red supergiant, and late-time luminosities indicate that up to 0.130 ± 0.026 M o of 56Ni are present, if the light curve is solely powered by radioactive decay, although the 56Ni mass may be lower if CSM interaction contributes to the post-plateau luminosity. Prominent multipeaked emission lines of Hα and [O i] emerge after day 154, as a result of either an asymmetric explosion or asymmetries in the CSM. The lack of narrow lines within the first 2 days of explosion in the likely presence of CSM interaction may be an example of close, dense, asymmetric CSM that is quickly enveloped by the spherical supernova ejecta.Ítem SN 2017ivv: Two years of evolution of a transitional Type II supernova(Oxford University Press, 2020-11) Gutiérrez C.P.; Pastorello A.; Jerkstrand A.; Galbany L.; Sullivan M.; Anderson J.P.; Taubenberger S.; Kuncarayakti H.; González-Gaitán S.; Wiseman P.; Inserra C.; Fraser M.; Maguire K.; Smartt S.; Müller-Bravo T.E.; Arcavi I.; Benetti S.; Bersier D.; Bose S.; Bostroem K.A.; Burke J.; Chen P.; Chen T.-W.; Della Valle M.; Dong S.; Gal-Yam A.; Gromadzki M.; Hiramatsu D.; Holoien T.W.-S.; Hosseinzadeh G.; Howell D.A.; Kankare E.; Kochanek C.S.; McCully C.; Nicholl M.; Pignata G.; Prieto J.L.; Shappee B.; Taggart K.; Tomasella L.; Valenti S.; Young D.R.We present the photometric and spectroscopic evolution of the Type II supernova (SN II) SN 2017ivv (also known as ASASSN- 17qp). Located in an extremely faint galaxy (Mr =-10.3 mag), SN 2017ivv shows an unprecedented evolution during the 2 yr of observations. At early times, the light curve shows a fast rise (~6-8 d) to a peak of Mmaxg = -17.84 mag, followed by a very rapid decline of 7.94 ± 0.48 mag per 100 d in the V band. The extensive photometric coverage at late phases shows that the radioactive tail has two slopes, one steeper than that expected from the decay of 56Co (between 100 and 350 d), and another slower (after 450 d), probably produced by an additional energy source. From the bolometric light curve, we estimated that the amount of ejected 56Ni is ~0.059 ± 0.003M⊙. The nebular spectra of SN 2017ivv show a remarkable transformation that allows the evolution to be split into three phases: (1) Ha strong phase ([removed]500 d).We find that the nebular analysis favours a binary progenitor and an asymmetric explosion. Finally, comparing the nebular spectra of SN 2017ivv to models suggests a progenitor with a zero-age main-sequence mass of 15-17M⊙. © 2020 The Author(s).Ítem SN 2018is: A low-luminosity Type IIP supernova with narrow hydrogen emission lines at early phases(EDP Sciences, 0025-02) Dastidar R.; Misra K.; Valenti S.; Sand D.J.; Reguitti A.; Pignata G. h; Benetti S.; Bose S.; Gangopadhyay A.; Singh M.; Tomasella LWe present a comprehensive photometric and spectroscopic study of the Type IIP supernova (SN) 2018is. The V band luminosity and the expansion velocity at 50 days post-explosion are −15.1 ± 0.2 mag (corrected for AV = 1.34 mag) and 1400 km s−1, classifying it as a low-luminosity SN II. The recombination phase in the V band is shorter, lasting around 110 days, and exhibits a steeper decline (1.0 mag per 100 days) compared to most other low-luminosity SNe II. Additionally, the optical and near-infrared spectra display hydrogen emission lines that are strikingly narrow, even for this class. The Fe ii and Sc ii line velocities are at the lower end of the typical range for low-luminosity SNe II. Semi-analytical modelling of the bolometric light curve suggests an ejecta mass of ∼8 M, corresponding to a pre-supernova mass of ∼9.5 M, and an explosion energy of ∼0.40 × 1051 erg. Hydrodynamical modelling further indicates that the progenitor had a zero-age main sequence mass of 9 M, coupled with a low explosion energy of 0.19 × 1051 erg. The nebular spectrum reveals weak [O i] λλ6300,6364 lines, consistent with a moderate-mass progenitor, while features typical of Fe core-collapse events, such as He i, [C i], and Fe i, are indiscernible. However, the redder colours and low ratio of Ni to Fe abundance do not support an electron-capture scenario either. As a low-luminosity SN II with an atypically steep decline during the photospheric phase and remarkably narrow emission lines, SN 2018is contributes to the diversity observed within this population. © The Authors 2025.Ítem SNhunt151: An explosive event inside a dense cocoon(Oxford University Press, 2018-04) Elias-Rosa N.; Benetti S.; Cappellaro E.; Pastorello A.; Terreran G.; Morales-Garoffolo A.; Howerton S.C.; Valenti S.; Kankare E.; Drake A.J.; Djorgovski S.G.; Tomasella L.; Tartaglia L.; Kangas T.; Ochner P.; Filippenko A.V.; Ciabattari F.; Geier S.l; Howell D.A.; Isern J.; Leonini S.; Pignata G.; Turatto M.SNhunt151 was initially classified as a supernova (SN) impostor (nonterminal outburst of a massive star). It exhibited a slow increase in luminosity, lasting about 450 d, followed by a major brightening that reaches MV ≈ -18 mag. No source is detected to MV ≳ -13 mag in archival images at the position of SNhunt151 before the slow rise. Low-to-mid-resolution optical spectra obtained during the pronounced brightening show very little evolution, being dominated at all times by multicomponent Balmer emission lines, a signature of interaction between the material ejected in the new outburst and the pre-existing circumstellar medium. We also analysed mid-infrared images from the Spitzer Space Telescope, detecting a source at the transient position in 2014 and 2015. Overall, SNhunt151 is spectroscopically a Type IIn SN, somewhat similar to SN 2009ip. However, there are also some differences, such as a slow pre-discovery rise, a relatively broad light-curve peak showing a longer rise time (~50 d), and a slower decline, along with a negligible change in the temperature around the peak (T ≤ 104 K). We suggest that SNhunt151 is the result of an outburst, or an SN explosion, within a dense circumstellar nebula, similar to those embedding some luminous blue variables like η Carinae and originating from past mass-loss events. © 2017 The Author(s).