Browsing by Author "Benetti, S."

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  • The enigmatic double-peaked stripped-envelope SN 2023aew
    (2024-09-01) Kangas, T.; Kuncarayakti, H.; Nagao, T.; Kotak, R.; Kankare, E.; Fraser, M.; Stevance, H.; Mattila, S.; Maeda, K.; Stritzinger, M.; Lundqvist, P.; Elias-Rosa, N.; Ferrari, L.; Folatelli, G.; Frohmaier, C.; Galbany, L.; Kawabata, M.; Koutsiona, E.; Müller-Bravo, T. E.; Piscarreta, L.; Pursiainen, M.; Singh, A.; Taguchi, K.; Teja, R. S.; Valerin, G.; Pastorello, A.; Benetti, S.; Cai, Y. Z.; Charalampopoulos, P.; Gutiérrez, C. P.; Kravtsov, T.; Reguitti, A.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We present optical and near-infrared photometry and spectroscopy of SN 2023aew and our findings on its remarkable properties. This event, initially resembling a Type IIb supernova (SN), rebrightens dramatically ~90 d after the first peak, at which time its spectrum transforms into that of a SN Ic. The slowly evolving spectrum specifically resembles a post-peak SN Ic with relatively low line velocities even during the second rise. The second peak, reached 119 d after the first peak, is both more luminous (Mr = -18.75±0.04 mag) and much broader than those of typical SNe Ic. Blackbody fits to SN 2023aew indicate that the photosphere shrinks almost throughout its observed evolution, and the second peak is caused by an increasing temperature. Bumps in the light curve after the second peak suggest interaction with circumstellar matter (CSM) or possibly accretion. We consider several scenarios for producing the unprecedented behavior of SN 2023aew. Two separate SNe, either unrelated or from the same binary system, require either an incredible coincidence or extreme fine-tuning. A pre-SN eruption followed by a SN requires an extremely powerful, SN-like eruption (consistent with ~1051 erg) and is also disfavored. We therefore consider only the first peak a true stellar explosion. The observed evolution is difficult to reproduce if the second peak is dominated by interaction with a distant CSM shell. A delayed internal heating mechanism is more likely, but emerging embedded interaction with a CSM disk should be accompanied by CSM lines in the spectrum, which are not observed, and is difficult to hide long enough. A magnetar central engine requires a delayed onset to explain the long time between the peaks. Delayed fallback accretion onto a black hole may present the most promising scenario, but we cannot definitively establish the power source.
  • The evolution of luminous red nova at 2017jfs in NGC4470?
    (2019-01-01) Pastorello, A.; Chen, T. W.; Cai, Y. Z.; Morales-Garoffolo, A.; Cano, Z.; Mason, E.; Barsukova, E. A.; Benetti, S.; Berton, M.; Bose, S.; Bufano, F.; Callis, E.; Cannizzaro, G.; Cartier, R.; Chen, Ping; Dong, Subo; Dyrbye, S.; Elias-Rosa, N.; Flörs, A.; Fraser, M.; Geier, S.; Goranskij, V. P.; Kann, D. A.; Kuncarayakti, H.; Onori, F.; Reguitti, A.; Reynolds, T.; Losada, I. R.; Sagués Carracedo, A.; Schweyer, T.; Smartt, S. J.; Tatarnikov, A. M.; Valeev, A. F.; Vogl, C.; Wevers, T.; De Ugarte Postigo, A.; Izzo, L.; Inserra, C.; Kankare, E.; Maguire, K.; Smith, K. W.; Stalder, B.; Tartaglia, L.; Thöne, C. C.; Valerin, G.; Young, D. R.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We present the results of our photometric and spectroscopic follow-up of the intermediate-luminosity optical transient AT 2017jfs. At peak, the object reaches an absolute magnitude of Mg = -15:46 ± 0:15 mag and a bolometric luminosity of 5:5 × 1041 erg s-1. Its light curve has the doublepeak shape typical of luminous red novae (LRNe), with a narrow first peak bright in the blue bands, while the second peak is longer-lasting and more luminous in the red and near-infrared (NIR) bands. During the first peak, the spectrum shows a blue continuum with narrow emission lines of H and Fe II. During the second peak, the spectrum becomes cooler, resembling that of a K-type star, and the emission lines are replaced by a forest of narrow lines in absorption. About 5 months later, while the optical light curves are characterized by a fast linear decline, the NIR ones show a moderate rebrightening, observed until the transient disappears in solar conjunction. At these late epochs, the spectrum becomes reminiscent of that of M-type stars, with prominent molecular absorption bands. The late-time properties suggest the formation of some dust in the expanding common envelope or an IR echo from foreground pre-existing dust. We propose that the object is a common-envelope transient, possibly the outcome of a merging event in a massive binary, similar to NGC4490-2011OT1.
  • Luminous red novae : Stellar mergers or giant eruptions?
    (2019-09-24) Pastorello, A.; Mason, E.; Taubenberger, S.; Fraser, M.; Cortini, G.; Tomasella, L.; Botticella, M. T.; Elias-Rosa, N.; Kotak, R.; Smartt, S. J.; Benetti, S.; Cappellaro, E.; Turatto, M.; Tartaglia, L.; Djorgovski, S. G.; Drake, A. J.; Berton, M.; Briganti, F.; Brimacombe, J.; Bufano, F.; Cai, Y-Z; Chen, S.; Christensen, E. J.; Ciabattari, F.; Congiu, E.; Dimai, A.; Inserra, C.; Kankare, E.; Magill, L.; Maguire, K.; Martinelli, F.; Morales-Garoffolo, A.; Ochner, P.; Pignata, G.; Reguitti, A.; Sollerman, J.; Spiro, S.; Terreran, G.; Wright, D. E.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We present extensive datasets for a class of intermediate-luminosity optical transients known as luminous red novae. They show double-peaked light curves, with an initial rapid luminosity rise to a blue peak (at -13 to -15 mag), which is followed by a longer-duration red peak that sometimes is attenuated, resembling a plateau. The progenitors of three of them (NGC 4490-2011OT1, M 101-2015OT1, and SNhunt248), likely relatively massive blue to yellow stars, were also observed in a pre-eruptive stage when their luminosity was slowly increasing. Early spectra obtained during the first peak show a blue continuum with superposed prominent narrow Balmer lines, with P Cygni profiles. Lines of Fe II are also clearly observed, mostly in emission. During the second peak, the spectral continuum becomes much redder, H alpha is barely detected, and a forest of narrow metal lines is observed in absorption. Very late-time spectra (similar to 6 months after blue peak) show an extremely red spectral continuum, peaking in the infrared (IR) domain. H alpha is detected in pure emission at such late phases, along with broad absorption bands due to molecular overtones (such as TiO, VO). We discuss a few alternative scenarios for luminous red novae. Although major instabilities of single massive stars cannot be definitely ruled out, we favour a common envelope ejection in a close binary system, with possibly a final coalescence of the two stars. The similarity between luminous red novae and the outburst observed a few months before the explosion of the Type IIn SN 2011ht is also discussed.
  • SN 2017ens: The Metamorphosis of a Luminous Broadlined Type Ic Supernova into an SN IIn
    (2018-11-10) Chen, T. W.; Inserra, C.; Fraser, M.; Moriya, T. J.; Schady, P.; Schweyer, T.; Filippenko, A. V.; Perley, D. A.; Ruiter, A. J.; Seitenzahl, I.; Sollerman, J.; Taddia, F.; Anderson, J. P.; Foley, R. J.; Jerkstrand, A.; Ngeow, C. C.; Pan, Y. C.; Pastorello, A.; Points, S.; Smartt, S. J.; Smith, K. W.; Taubenberger, S.; Wiseman, P.; Young, D. R.; Benetti, S.; Berton, M.; Bufano, F.; Clark, P.; Valle, M. Della; Galbany, L.; Gal-Yam, A.; Gromadzki, M.; Gutiérrez, C. P.; Heinze, A.; Kankare, E.; Kilpatrick, C. D.; Kuncarayakti, H.; Leloudas, G.; Lin, Z. Y.; Maguire, K.; Mazzali, P.; McBrien, O.; Prentice, S. J.; Rau, A.; Rest, A.; Siebert, M. R.; Stalder, B.; Tonry, J. L.; Yu, P. C.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We present observations of supernova (SN) 2017ens, discovered by the ATLAS survey and identified as a hot blue object through the GREAT program. The redshift z = 0.1086 implies a peak brightness of M g = -21.1 mag, placing the object within the regime of superluminous supernovae. We observe a dramatic spectral evolution, from initially being blue and featureless, to later developing features similar to those of the broadlined Type Ic SN 1998bw, and finally showing ∼2000 km s-1 wide Hα and Hβ emission. Relatively narrow Balmer emission (reminiscent of a SN IIn) is present at all times. We also detect coronal lines, indicative of a dense circumstellar medium. We constrain the progenitor wind velocity to ∼50-60 km s-1 based on P-Cygni profiles, which is far slower than those present in Wolf-Rayet stars. This may suggest that the progenitor passed through a luminous blue variable phase, or that the wind is instead from a binary companion red supergiant star. At late times we see the ∼2000 km s-1 wide Hα emission persisting at high luminosity (∼3 × 1040 erg s-1) for at least 100 day, perhaps indicative of additional mass loss at high velocities that could have been ejected by a pulsational pair instability.
  • SN 2017gci: A nearby Type i Superluminous Supernova with a bumpy tail
    (2021-04-01) Fiore, A.; Chen, T. W.; Jerkstrand, A.; Benetti, S.; Ciolfi, R.; Inserra, C.; Cappellaro, E.; Pastorello, A.; Leloudas, G.; Schulze, S.; Berton, M.; Burke, J.; McCully, C.; Fong, W.; Galbany, L.; Gromadzki, M.; Gutiérrez, C. P.; Hiramatsu, D.; Hosseinzadeh, G.; Howell, D. A.; Kankare, E.; Lunnan, R.; Müller-Bravo, T. E.; O' Neill, D.; Nicholl, M.; Rau, A.; Sollerman, J.; Terreran, G.; Valenti, S.; Young, D. R.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We present and discuss the optical spectrophotometric observations of the nearby (z = 0.087) Type I superluminous supernova (SLSN I) SN 2017gci, whose peak K-corrected absolute magnitude reaches M-g = -21.5 mag. Its photometric and spectroscopic evolution includes features of both slow- and of fast-evolving SLSN I, thus favoring a continuum distribution between the two SLSN-I subclasses. In particular, similarly to other SLSNe I, the multiband light curves (LCs) of SN 2017gci show two re-brightenings at about 103 and 142 d after the maximum light. Interestingly, this broadly agrees with a broad emission feature emerging around 6520 angstrom after similar to 51 d from the maximum light, which is followed by a sharp knee in the LC. If we interpret this feature as H alpha, this could support the fact that the bumps are the signature of late interactions of the ejecta with a (hydrogen-rich) circumstellar material. Then we fitted magnetar- and CSM-interaction-powered synthetic LCs on to the bolometric one of SN 2017gci. In the magnetar case, the fit suggests a polar magnetic field B-p similar or equal to 6 x 10(14) G, an initial period of the magnetar P-initial similar or equal to 2.8 ms, an ejecta mass M-ejecta similar or equal to 9M(circle dot) and an ejecta opacity kappa similar or equal to 0.08 cm(2) g(-1). A CSM-interaction scenario would imply a CSM mass similar or equal to 5 M-circle dot and an ejecta mass similar or equal to 12M(circle dot). Finally, the nebular spectrum of phase + 187 d was modeled, deriving a mass of similar or equal to 10 M-circle dot for the ejecta. Our models suggest that either a magnetar or CSM interaction might be the power sources for SN 2017gci and that its progenitor was a massive (40 M-circle dot) star.
  • SN 2017gmr: An Energetic Type II-P Supernova with Asymmetries
    (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; 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, Junbo
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We 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.