Examinando por Autor "Howell, D. A."
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Ítem Investigating the properties of stripped-envelope supernovae; what are the implications for their progenitors?(Monthly Notices of the Royal Astronomical Society, 2019-02-15) Prentice, S. J.; Ashall, C.; James, P. A.; Short, L.; Mazzali, P. A.; Bersier, D.; Crowther, P. A.; Barbarino, C.; Chen, T.-W.; Copperwheat, C. M.; Darnley, M. J.; Denneau, L.; Elias-Rosa, N.; Fraser, M.; Galbany, L.; Gal-Yam, A.; Harmanen, J.; Howell, D. A.; Hosseinzadeh, G.; Inserra, C.; Kankare, E.; Karamehmetoglu, E.; Lamb, G. P.; Limongi, M.; Maguire, K.; McCully, C.; Olivares E., F.; Piascik, A. S.; Pignata, G.; Reichart, D. E.; Rest, A.; Reynolds, T.; Rodríguez, O.; Saario, J. L. O.; Schulze, S.; Smartt, S. J.; Smith, K. W.; Sollerman, J.; Stalder, B.; Sullivan, M.; Taddia, F.; Valenti, S.; Vergani, S. D.; Williams, S. C.; Young, D. R.We present observations and analysis of 18 stripped-envelope supernovae observed during 2013–2018. This sample consists of five H/He-rich SNe, six H-poor/He-rich SNe, three narrow lined SNe Ic, and four broad lined SNe Ic. The peak luminosity and characteristic time-scales of the bolometric light curves are calculated, and the light curves modelled to derive 56Ni and ejecta masses (MNi and Mej). Additionally, the temperature evolution and spectral line velocity curves of each SN are examined. Analysis of the [O I] line in the nebular phase of eight SNe suggests their progenitors had initial masses <20 M . The bolometric light curve properties are examined in combination with those of other SE events from the literature. The resulting data set gives the Mej distribution for 80 SE–SNe, the largest such sample in the literature to date, and shows that SNe Ib have the lowest median Mej, followed by narrow-lined SNe Ic, H/He-rich SNe, broad-lined SNe Ic, and finally gamma-ray burst SNe. SNe Ic-6/7 show the largest spread of Mej ranging from ∼1.2–11 M , considerably greater than any other subtype. For all SE–SNe = 2.8 ± 1.5 M which further strengthens the evidence that SE–SNe arise from low-mass progenitors which are typically <5 M at the time of explosion, again suggesting MZAMS <25 M . The low and lack of clear bimodality in the distribution implies <30 M progenitors and that envelope stripping via binary interaction is the dominant evolutionary pathway of these SNe.Ítem On Type IIn/Ia-CSM supernovae as exemplified by SN 2012ca(OXFORD UNIV PRESS, 2016-07) Inserra, C.; Fraser, M.; Smartt, S. J.; Benetti, S.; Chen, T.-W.; Childress, M.; Gal-Yam, A.; Howell, D. A.; Kangas, T.; Pignata, G.; Polshaw, J.; Sullivan, M.; Smith, K. W.; Valenti, S.; Young, D. R.; Parker, S.; Seccull, T.; McCrum, M.We present the complete set of ultra-violet, optical and near-infrared photometry and spectroscopy for SN 2012ca, covering the period from 6 d prior to maximum light, until 531 d after maximum. The spectroscopic time series for SN 2012ca is essentially unchanged over 1.5 yr, and appear to be dominated at all epochs by signatures of interaction with a dense circumstellar medium (CSM) rather than the underlying supernova (SN). SN 2012ca is a member of the set of type of the ambiguous IIn/Ia-CSM SNe, the nature of which have been debated extensively in the literature. The two leading scenarios are either a Type Ia SN exploding within a dense CSM from a non-degenerate, evolved companion, or a core-collapse SN from a massive star. While some members of the population have been unequivocally associated with Type Ia SNe, in other cases the association is less certain. While it is possible that SN 2012ca does arise from a thermonuclear SN, this would require a relatively high (between 20 and 70 per cent) efficiency in converting kinetic energy to optical luminosity, and a massive (∼2.3–2.6 M⊙) circumstellar medium. On the basis of energetics, and the results of simple modelling, we suggest that SN 2012ca is more likely associated with a core-collapse SN. This would imply that the observed set of similar SNe to SN 2012ca is in fact originated by two populations, and while these are drawn from physically distinct channels, they can have observationally similar properties.Ítem Supernova 2013fc in a circumnuclear ring of a luminous infrared galaxy: The big brother of SN 1998S(OXFORD UNIV PRESS, 2016-02) Kangas, T.; Mattila, S.; Kankare, E.; Lundqvist, P.; Väisänen, P.; Childress, M.; Pignata, G.; McCully, C.; Valenti, S.; Vinkó, J.; Pastorello, A.; Elias-Rosa, N.; Fraser, M.; Gal-Yam, A.; Kotak, R.; Kotilainen, J. K.; Smartt, S. J.; Galbany, L.; Harmanen, J.; Howell, D. A.; Inserra, C.; Marion, G. H.; Quimby, R. M.; Silverman, J. M.; Szalai, T.; Wheeler, J. C.; Ashall, C.; Benetti, S.; Romero-Cañizales, C.; Smith, K. W.; Sullivan, M.; Takáts, K.; Young, D. R.We present photometric and spectroscopic observations of SN 2013fc, a bright type II supernova (SN) in a circumnuclear star-forming ring in the luminous infrared galaxy ESO 154-G010, observed as part of the Public ESO Spectroscopic Survey of Transient Objects. SN 2013fc is both photometrically and spectroscopically similar to the well-studied type IIn SN 1998S and to the bright type II-L SN 1979C. It exhibits an initial linear decline, followed by a short plateau phase and a tail phase with a decline too fast for Co-56 decay with full. gamma-ray trapping. Initially, the spectrum was blue and featureless. Later on, a strong broad (similar to 8000 km s(-1)) H alpha emission profile became prominent. We apply a STARLIGHT stellar population model fit to the SN location (observed when the SN had faded) to estimate a high extinction of A(V) = 2.9 +/- 0.2 mag and an age of 10(+ 3) (- 2) Myr for the underlying cluster. We compare the SN to SNe 1998S and 1979C and discuss its possible progenitor star considering the similarities to these events. With a peak brightness of B = - 20.46 +/- 0.21 mag, SN 2013fc is 0.9 mag brighter than SN 1998S and of comparable brightness to SN 1979C. We suggest that SN 2013fc was consistent with a massive red supergiant (RSG) progenitor. Recent mass loss probably due to a strong RSG wind created the circumstellar matter illuminated through its interaction with the SN ejecta. We also observe a near- infrared excess, possibly due to newly condensed dust.Ítem The double-peaked Type Ic supernova 2019cad: another SN 2005bf-like object(Oxford University Press, 2021-04) Gutierrez, C. P; Bersten, M. C.; Orellana, M; Pastorello, A.; Ertini, K.; Folatelli, G.; Pignata, G.; Anderson, J.P.; Smartt, S.; Sullivan, M.; Pursiainen, M.; Inserra, C.; Elias-Rosa, N.; Fraser, M.; Kankare, E.; Moran, S.; Reguitti, A.; Reynolds, T.M; Stritzinger, M.; Burke, J.; Frohmaier, C.; Galbany, L.; Hiramatsu, D.; Howell, D. A.; Kuncarayakti, H.; Mattila, S.; Muller-Bravo, T.; Pellegrino, C.; Smith, M.We present the photometric and spectroscopic evolution of supernova (SN) 2019cad during the first ∼100 d from explosion. Based on the light-curve morphology, we find that SN 2019cad resembles the double-peaked Type Ib/c SN 2005bf and the Type Ic PTF11mnb. Unlike those two objects, SN 2019cad also shows the initial peak in the redder bands. Inspection of the g-band light curve indicates the initial peak is reached in ∼8 d, while the r-band peak occurred ∼15 d post-explosion. A second and more prominent peak is reached in all bands at ∼45 d past explosion, followed by a fast decline from ∼60 d. During the first 30 d, the spectra of SN 2019cad show the typical features of a Type Ic SN, however, after 40 d, a blue continuum with prominent lines of Si II λ6355 and CII λ6580 is observed again. Comparing the bolometric light curve to hydrodynamical models, we find that SN 2019cad is consistent with a pre-SN mass of 11 M, and an explosion energy of 3.5 × 1051 erg. The light-curve morphology can be reproduced either by a double-peaked 56Ni distribution with an external component of 0.041 M, and an internal component of 0.3 M or a double-peaked 56Ni distribution plus magnetar model (P ∼ 11 ms and B ∼ 26 × 1014 G). If SN 2019cad were to suffer from significant host reddening (which cannot be ruled out), the 56Ni model would require extreme values, while the magnetar model would still be feasible