Examinando por Autor "Pastorello A."
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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 Forbidden hugs in pandemic times: IV. Panchromatic evolution of three luminous red novae(EDP Sciences, 2023-03) Pastorello A.; Valerin G.; Fraser M.; Reguitti A.; Elias-Rosa N.; Filippenko A.V.; Rojas-Bravo C.; Tartaglia L.; Reynolds T.M.; Valenti S.; Andrews J.E.; Ashall C.; Bostroem K.A.; Brink T.G.; Burke J.; Cai Y.-Z.; Cappellaro E.; Coulter D.A.; Dastidar R.; Davis K.W.; Dimitriadis G.; Fiore A.; Foley R.J.; Fugazza D.; Galbany L.; Gangopadhyay A.; Geier S.; Gutiérrez C.P.; Haislip J.; Hiramatsu D.; Holmbo S.; Howell D.A.; Hsiao E.Y.; Hung T.; Jha S.W.; Kankare E.; Karamehmetoglu E.; Kilpatrick C.D.; Kotak R.; Kouprianov V.; Kravtsov T.; Kumar S.; Li Z.-T.; Lundquist M.J.; Lundqvist P.; Matilainen K.; Mazzali P.A.; McCully C.; Misra K.; Morales-Garoffolo A.; Moran S.; Morrell N.; Newsome M.; Padilla Gonzalez E.; Pan Y.-C.; Pellegrino C.; Phillips M.M.; Pignata G.; Piro A.L.; Reichart D.E.; Rest A.; Salmaso I.; Sand D.J.; Siebert M.R.; Smartt S.J.; Smith K.W.; Srivastav S.; Stritzinger M.D.; Taggart K.; Tinyanont S.; Yan S.-Y.; Wang L.; Wang X.-F.; Williams S.C.; Wyatt S.; Zhang T.-M.; De Boer T.; Chambers K.; Gao H.; Magnier E.We present photometric and spectroscopic data on three extragalactic luminous red novae (LRNe): AT 2018bwo, AT 2021afy, and AT 2021blu. AT 2018bwo was discovered in NGC 45 (at about 6.8 Mpc) a few weeks after the outburst onset. During the monitoring period, the transient reached a peak luminosity of 1040 erg s1. AT 2021afy, hosted by UGC 10043 (49.2 Mpc), showed a double-peaked light curve, with the two peaks reaching a similar luminosity of 2.1(±0.6) - 1041 erg s1. Finally, for AT 2021blu in UGC 5829 (∼8.6 Mpc), the pre-outburst phase was well-monitored by several photometric surveys, and the object showed a slow luminosity rise before the outburst. The light curve of AT 2021blu was sampled with an unprecedented cadence until the object disappeared behind the Sun, and it was then recovered at late phases. The light curve of LRN AT 2021blu shows a double peak, with a prominent early maximum reaching a luminosity of 6.5 - 1040 erg s1, which is half of that of AT 2021afy. The spectra of AT 2021afy and AT 2021blu display the expected evolution for LRNe: a blue continuum dominated by prominent Balmer lines in emission during the first peak, and a redder continuum consistent with that of a K-type star with narrow absorption metal lines during the second, broad maximum. The spectra of AT 2018bwo are markedly different, with a very red continuum dominated by broad molecular features in absorption. As these spectra closely resemble those of LRNe after the second peak, AT 2018bwo was probably discovered at the very late evolutionary stages. This would explain its fast evolution and the spectral properties compatible with that of an M-type star. From the analysis of deep frames of the LRN sites years before the outburst, and considerations of the light curves, the quiescent progenitor systems of the three LRNe were likely massive, with primaries ranging from about 13 M for AT 2018bwo, to 141+4 M⊙ for AT 2021blu, and over 40 M for AT 2021afy. © 2023 The Authors.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 Photometry and spectroscopy of the Type Icn supernova 2021ckj: The diverse properties of the ejecta and circumstellar matter of Type Icn supernovae(EDP Sciences, 2023-05) Nagao T.; Kuncarayakti H.; Maeda K.; Moore T.; Pastorello A.; Mattila S.; Uno K.; Smartt S.J.; Sim S.A.; Ferrari L.; Tomasella L.; Anderson J.P.; Chen T.-W.; Galbany L.; Gao H.; Gromadzki M.; Gutiérrez C.P.; Inserra C.; Kankare E.; Magnier E.A.; Müller-Bravo T.E.; Reguitti A.; Young D.R.We present photometric and spectroscopic observations of the Type Icn supernova (SN) 2021ckj. This rare type of SNe is characterized by a rapid evolution and high peak luminosity as well as narrow lines of highly ionized carbon at early phases, implying an interaction with hydrogen- and helium-poor circumstellar matter (CSM). SN 2021ckj reached a peak brightness of ~-20 mag in the optical bands, with a rise time and a time above half maximum of ~4 and ~10 days, respectively, in the g and cyan bands. These features are reminiscent of those of other Type Icn SNe (SNe 2019hgp, 2021csp, and 2019jc), with the photometric properties of SN 2021ckj being almost identical to those of SN 2021csp. Spectral modeling of SN 2021ckj reveals that its composition is dominated by oxygen, carbon, and iron group elements, and the photospheric velocity at peak is ~10000 km s-1. Modeling the spectral time series of SN 2021ckj suggests aspherical SN ejecta. From the light curve (LC) modeling applied to SNe 2021ckj, 2019hgp, and 2021csp, we find that the ejecta and CSM properties of Type Icn SNe are diverse. SNe 2021ckj and 2021csp likely have two ejecta components (an aspherical high-energy component and a spherical standard-energy component) with a roughly spherical CSM, while SN 2019hgp can be explained by a spherical ejecta-CSM interaction alone. The ejecta of SNe 2021ckj and 2021csp have larger energy per ejecta mass than the ejecta of SN 2019hgp. The density distribution of the CSM is similar in these three SNe, and is comparable to those of Type Ibn SNe. This may imply that the mass-loss mechanism is common between Type Icn (and also Type Ibn) SNe. The CSM masses of SN 2021ckj and SN 2021csp are higher than that of SN 2019hgp, although all these values are within those seen in Type Ibn SNe. The early spectrum of SN 2021ckj shows narrow emission lines from C II and C III, without a clear absorption component, in contrast with that observed in SN 2021csp. The similarity of the emission components of these lines implies that the emitting regions of SNe 2021ckj and 2021csp have similar ionization states, and thus suggests that they have similar properties as the ejecta and CSM, which is also inferred from the LC modeling. Taking the difference in the strength of the absorption features into account, this heterogeneity may be attributed to viewing angle effects in otherwise common aspherical ejecta. In particular, in this scenario SN 2021ckj is observed from the polar direction, while SN 2021csp is seen from an off-axis direction. This is also supported by the fact that the late-time spectra of SNe 2021ckj and 2021csp show similar features but with different line velocities. © 2023 EDP Sciences. All rights reserved.Ítem 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 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).