ALBERT

Description: Super-luminous supernovae that radiate more than 10(44) ergs per second at their peak luminosity have recently been discovered in faint galaxies at redshifts of 0.1-4. Some evolve slowly, resembling models of 'pair-instability' supernovae. Such models involve stars with original masses 140-260 times that of the Sun that now have carbon-oxygen cores of 65-130 solar masses. In these stars, the photons that prevent gravitational collapse are converted to electron-positron pairs, causing rapid contraction and thermonuclear explosions. Many solar masses of (56)Ni are synthesized; this isotope decays to (56)Fe via (56)Co, powering bright light curves. Such massive progenitors are expected to have formed from metal-poor gas in the early Universe. Recently, supernova 2007bi in a galaxy at redshift 0.127 (about 12 billion years after the Big Bang) with a metallicity one-third that of the Sun was observed to look like a fading pair-instability supernova. Here we report observations of two slow-to-fade super-luminous supernovae that show relatively fast rise times and blue colours, which are incompatible with pair-instability models. Their late-time light-curve and spectral similarities to supernova 2007bi call the nature of that event into question. Our early spectra closely resemble typical fast-declining super-luminous supernovae, which are not powered by radioactivity. Modelling our observations with 10-16 solar masses of magnetar-energized ejecta demonstrates the possibility of a common explosion mechanism. The lack of unambiguous nearby pair-instability events suggests that their local rate of occurrence is less than 6 x 10(-6) times that of the core-collapse rate.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Nicholl, M -- Smartt, S J -- Jerkstrand, A -- Inserra, C -- McCrum, M -- Kotak, R -- Fraser, M -- Wright, D -- Chen, T-W -- Smith, K -- Young, D R -- Sim, S A -- Valenti, S -- Howell, D A -- Bresolin, F -- Kudritzki, R P -- Tonry, J L -- Huber, M E -- Rest, A -- Pastorello, A -- Tomasella, L -- Cappellaro, E -- Benetti, S -- Mattila, S -- Kankare, E -- Kangas, T -- Leloudas, G -- Sollerman, J -- Taddia, F -- Berger, E -- Chornock, R -- Narayan, G -- Stubbs, C W -- Foley, R J -- Lunnan, R -- Soderberg, A -- Sanders, N -- Milisavljevic, D -- Margutti, R -- Kirshner, R P -- Elias-Rosa, N -- Morales-Garoffolo, A -- Taubenberger, S -- Botticella, M T -- Gezari, S -- Urata, Y -- Rodney, S -- Riess, A G -- Scolnic, D -- Wood-Vasey, W M -- Burgett, W S -- Chambers, K -- Flewelling, H A -- Magnier, E A -- Kaiser, N -- Metcalfe, N -- Morgan, J -- Price, P A -- Sweeney, W -- Waters, C -- England -- Nature. 2013 Oct 17;502(7471):346-9. doi: 10.1038/nature12569.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Astrophysics Research Centre, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, UK. mnicholl03@qub.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24132291" target="_blank"〉PubMed〈/a〉

Description: The explosive fate of massive Wolf-Rayet stars (WRSs) is a key open question in stellar physics. An appealing option is that hydrogen-deficient WRSs are the progenitors of some hydrogen-poor supernova explosions of types IIb, Ib and Ic (ref. 2). A blue object, having luminosity and colours consistent with those of some WRSs, has recently been identified in pre-explosion images at the location of a supernova of type Ib (ref. 3), but has not yet been conclusively determined to have been the progenitor. Similar work has so far only resulted in non-detections. Comparison of early photometric observations of type Ic supernovae with theoretical models suggests that the progenitor stars had radii of less than 10(12) centimetres, as expected for some WRSs. The signature of WRSs, their emission line spectra, cannot be probed by such studies. Here we report the detection of strong emission lines in a spectrum of type IIb supernova 2013cu (iPTF13ast) obtained approximately 15.5 hours after explosion (by 'flash spectroscopy', which captures the effects of the supernova explosion shock breakout flash on material surrounding the progenitor star). We identify Wolf-Rayet-like wind signatures, suggesting a progenitor of the WN(h) subclass (those WRSs with winds dominated by helium and nitrogen, with traces of hydrogen). The extent of this dense wind may indicate increased mass loss from the progenitor shortly before its explosion, consistent with recent theoretical predictions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gal-Yam, Avishay -- Arcavi, I -- Ofek, E O -- Ben-Ami, S -- Cenko, S B -- Kasliwal, M M -- Cao, Y -- Yaron, O -- Tal, D -- Silverman, J M -- Horesh, A -- De Cia, A -- Taddia, F -- Sollerman, J -- Perley, D -- Vreeswijk, P M -- Kulkarni, S R -- Nugent, P E -- Filippenko, A V -- Wheeler, J C -- England -- Nature. 2014 May 22;509(7501):471-4. doi: 10.1038/nature13304.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100, Israel. ; Astrophysics Science Division, NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, Maryland 20771, USA. ; Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, California 91101, USA. ; Cahill Center for Astrophysics, California Institute of Technology, Pasadena, California 91125, USA. ; Department of Astronomy, University of Texas, Austin, Texas 78712, USA. ; The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, 10691 Stockholm, Sweden. ; Physics Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA. ; Department of Astronomy, University of California, Berkeley, California 94720-3411, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24848059" target="_blank"〉PubMed〈/a〉

Description: Type Ia supernovae are destructive explosions of carbon-oxygen white dwarfs. Although they are used empirically to measure cosmological distances, the nature of their progenitors remains mysterious. One of the leading progenitor models, called the single degenerate channel, hypothesizes that a white dwarf accretes matter from a companion star and the resulting increase in its central pressure and temperature ignites thermonuclear explosion. Here we report observations with the Swift Space Telescope of strong but declining ultraviolet emission from a type Ia supernova within four days of its explosion. This emission is consistent with theoretical expectations of collision between material ejected by the supernova and a companion star, and therefore provides evidence that some type Ia supernovae arise from the single degenerate channel.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cao, Yi -- Kulkarni, S R -- Howell, D Andrew -- Gal-Yam, Avishay -- Kasliwal, Mansi M -- Valenti, Stefano -- Johansson, J -- Amanullah, R -- Goobar, A -- Sollerman, J -- Taddia, F -- Horesh, Assaf -- Sagiv, Ilan -- Cenko, S Bradley -- Nugent, Peter E -- Arcavi, Iair -- Surace, Jason -- Wozniak, P R -- Moody, Daniela I -- Rebbapragada, Umaa D -- Bue, Brian D -- Gehrels, Neil -- England -- Nature. 2015 May 21;521(7552):328-31. doi: 10.1038/nature14440.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Astronomy Department, California Institute of Technology, Pasadena, California 91125, USA. ; 1] Astronomy Department, California Institute of Technology, Pasadena, California 91125, USA [2] Caltech Optical Observatories, California Institute of Technology, Pasadena, California 91125, USA. ; 1] Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Suite 102, Goleta, California 93117, USA [2] Department of Physics, University of California, Santa Barbara, California 93106, USA. ; Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100, Israel. ; Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, California 91101, USA. ; The Oskar Klein Centre, Department of Physics, Stockholm University, SE-106 91 Stockholm, Sweden. ; The Oskar Klein Centre, Department of Astronomy, Stockholm University, SE-106 91 Stockholm, Sweden. ; Astrophysics Science Division, NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, Maryland 20771, USA. ; 1] Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA [2] Astronomy Department, University of California, Berkeley, 501 Campbell Hall, Berkeley, California 94720, USA. ; 1] Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Suite 102, Goleta, California 93117, USA [2] Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106, USA. ; Spitzer Science Center, California Institute of Technology, Pasadena, California 91125, USA. ; Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA. ; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25993962" target="_blank"〉PubMed〈/a〉

Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cao, Yi -- Kulkarni, S R -- Howell, D Andrew -- Gal-Yam, Avishay -- Kasliwal, Mansi M -- Valenti, Stefano -- Johansson, J -- Amanullah, R -- Goobar, A -- Sollerman, J -- Taddia, F -- Horesh, Assaf -- Sagiv, Ilan -- Cenko, S Bradley -- Nugent, Peter E -- Arcavi, Iair -- Surace, Jason -- Wozniak, P R -- Moody, Daniela I -- Rebbapragada, Umaa D -- Bue, Brian D -- Gehrels, Neil -- England -- Nature. 2015 Aug 27;524(7566):502. doi: 10.1038/nature14605. Epub 2015 Jun 24.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26106860" target="_blank"〉PubMed〈/a〉