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Turatto M Suzuki T Mazzali PA Benetti S Cappellaro E Danziger IJ Nomoto K Nakamura T Young TR Patat F 《The Astrophysical journal》2000,534(1):L57-L61
The extraordinary SN 1997cy associated with GRB 970514 has been observed photometrically and spectroscopically for nearly 2 yr. At the time of discovery, SN 1997cy was the brightest supernova (SN) ever observed (MV=-20.1, vhel=19,140 km s-1, H0=65 km s-1 Mpc-1). Up to the last available observations (600 days after the gamma-ray burst), the total time-integrated flux was equal to or larger than that expected from the complete thermalization of the gamma-rays produced by 2.3 M middle dot in circle of 56Co. However, starting already on day 60 the luminosity decline is slower than the 56Co decay rate, indicating that the SN ejecta was interacting with circumstellar material (CSM). The interaction appeared to weaken around day 550. The spectra of SN 1997cy are dominated at all epochs by Halpha emission, which shows at least three components of different widths, as in SN 1988Z. Several other lines with different widths are also visible, especially at early epochs. The entire light curve of SN 1997cy is reproduced by a model of the interaction of the very energetic (E=3x1052 ergs) ejecta of a massive star (25 M middle dot in circle) with the CSM, with some contribution from radioactive decays. The CSM could have been ejected with a mass-loss rate of M&d2; approximately 4x10-4 M middle dot in circle yr-1 as the progenitor star evolved from a blue to a red supergiant about 104 yr before the explosion. The lack of oxygen and magnesium lines in the spectra at nebular phases poses a problem for models requiring high-mass progenitors. The possibility that most of the core material of the progenitor has fallen onto a massive black hole so that the reverse shock dies at the inner edge of the H/He envelope is discussed. 相似文献
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S. Benetti E. Cappellaro I. J. Danziger M. Turatto F. Patat & M. Della Valle 《Monthly notices of the Royal Astronomical Society》1998,294(3):448-456
Extensive photometric and spectroscopic observations of SN 1994aj until 540 d after maximum light have been obtained. The photometry around maximum suggests that the SN belongs to the Type II Linear class, with a peak absolute magnitude of M V ∼−17.8 (assuming H 0 =75 km s−1 Mpc−1 ). The spectra of SN 1994aj were unusual, with the presence of a narrow line with a P Cygni profile on top of the broad Balmer line emission. This narrow feature is attributed to the presence of a dense superwind surrounding the SN. At 100–120 d after maximum light the SN ejecta start to interact with this circumstellar material. The SN luminosity decline rates slowed down [γ R =0.46 mag (100 d)−1 ], becoming less steep than the average late luminosity decline of normal SN II [∼1 mag (100 d)−1 ]. This dense ( ˙M / u W ∼1015 g cm−1 ) wind was confined to a short distance from the progenitor ( R out =∼5×1016 cm), and results from a very strong mass-loss episode ( ˙M =10−3 M⊙ yr−1 ), which terminated shortly before explosion (∼5–10 yr). 相似文献
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G. Pignata F. Patat S. Benetti S. Blinnikov W. Hillebrandt R. Kotak B. Leibundgut P. A. Mazzali P. Meikle Y. Qiu P. Ruiz-Lapuente S. J. Smartt E. Sorokina M. Stritzinger M. Stehle M. Turatto T. Marsh F. Martin-Luis N. McBride J. Mendez L. Morales-Rueda D. Narbutis R. Street 《Monthly notices of the Royal Astronomical Society》2004,355(1):178-190
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A. Pastorello E. Baron D. Branch L. Zampieri M. Turatto M. Ramina S. Benetti E. Cappellaro M. Salvo F. Patat A. Piemonte J. Sollerman B. Leibundgut G. Altavilla 《Monthly notices of the Royal Astronomical Society》2005,360(3):950-962
We present spectroscopic and photometric observations of the peculiar Type II supernova (SN) 1998A. The light curves and spectra closely resemble those of SN 1987A, suggesting that the SN 1998A progenitor exploded when it was a compact blue supergiant. However, the comparison with SN 1987A also highlights some important differences: SN 1998A is more luminous and the spectra show bluer continua and larger expansion velocities at all epochs. These observational properties indicate that the explosion of SN 1998A is more energetic than SN 1987A and more typical of Type II supernovae. Comparing the observational data with simulations, we deduce that the progenitor of SN 1998A was a massive star (∼25 M⊙ ) with a small pre-supernova radius (≲6 × 1012 cm) . The Ba ii lines, unusually strong in SN 1987A and some faint II-P events, are almost normal in the case of SN 1998A, indicating that the temperature plays a key role in determining their strength. 相似文献
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P. Benetti R. Acciarri F. Adamo B. Baibussinov M. Baldo-Ceolin M. Belluco F. Calaprice E. Calligarich M. Cambiaghi F. Carbonara F. Cavanna S. Centro A.G. Cocco F. Di Pompeo N. Ferrari G. Fiorillo C. Galbiati V. Gallo L. Grandi A. Ianni G. Mangano G. Meng C. Montanari O. Palamara L. Pandola F. Pietropaolo G.L. Raselli M. Rossella C. Rubbia A.M. Szelc S. Ventura C. Vignoli WARP Collaboration 《Astroparticle Physics》2008,28(6):495-507
A new method of searching for dark matter in the form of weakly interacting massive particles (WIMP) has been developed with the direct detection of the low energy nuclear recoils observed in a massive target (ultimately many tons) of ultra pure liquid argon at 87 K. A high selectivity for argon recoils is achieved by the simultaneous observation of both the VUV scintillation luminescence and of the electron signal surviving columnar recombination, extracted through the liquid–gas boundary by an electric field.
First physics results from this method are reported, based on a small 2.3 l test chamber filled with natural argon and an accumulated fiducial exposure of about 100 kg day, supporting the future validity of this method with isotopically purified 40Ar and for a much larger unit presently under construction with correspondingly increased sensitivities. 相似文献
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Near-seabed (<50 m) sediments were studied throughout the Irish sector of the Rockall Trough (ca. 123,000 km2) based on a combined analysis of shallow seismic (3.5 kHz) and multibeam swath data acquired by the Irish National Seabed Survey and reprocessed here at higher resolution. The detailed identification of seven acoustic facies served to classify the Rockall Trough into six main sedimentary provinces, incorporating the well-known Feni Drift, Donegal-Barra Fan and Rockall Bank mass flow. In the northern part of the study area, extensive mass transport deposits from both flanks of the trough are the dominant depositional features. Debris flow deposits formed by ice streaming of the British-Irish ice sheet characterise most of the Donegal-Barra Fan, whereas turbidite deposition occurs towards the toe of the fan. On the western margin of the trough, the post-glacial Rockall Bank mass flow deposit displays a rough topography with no acoustic penetration. Several failure scarps are visible on the flank of the bank where the mass flow originated, and pass downslope into large sediment lobes and smaller debris flow deposits. Smaller-scale mass transport deposits were also discovered close to some canyons indenting the eastern slope. High seismic penetration characterises the Feni contourite drift deposit, and precise mapping of its geographical extent shows that it is considerably wider than previously reported. The sediment waves that drape this drift are interpreted as predominantly relict features, and their varied geometry suggests a complex oceanographic regime. In the deeper part of the trough, the data reveal novel evidence of the widespread occurrence (about 12,000 km2) of distinct seismic and backscatter signatures indicating the possible presence of fluid escape structures within fine-grained sediments of mixed contouritic, hemipelagic and turbiditic origin. Sediment overloading and increased pore pressure resulting from extensive mass wasting to the north of the area is a likely cause of dewatering-rooted fluid migration towards the seabed, but further investigations are required to confirm the nature and origin of such fluids in the Rockall Trough. 相似文献
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F. Sacchetti S. Benetti A. Georgiopoulou P.M. Shannon B.M. O'Reilly P. Dunlop R. Quinn C. Ó Cofaigh 《Marine Geology》2012
The continental margin offshore of western Ireland offers an opportunity to study the effects of glacial forcing on the morphology and sediment architecture of a mid-latitude margin. High resolution multibeam bathymetry and backscatter data, combined with shallow seismic and TOBI deep-towed side-scan sonar profiles, provide the basis for this study and allow a detailed geomorphological interpretation of the northwest Irish continental margin. Several features, including submarine mass failures, canyon systems and escarpments, are identified in the Rockall Trough for the first time. A new physiographic classification of the Irish margin is proposed and linked to the impact of glaciations along the margin. Correlation of the position and dimensions of moraines on the continental shelf with the level of canyon evolution suggests that the sediment and meltwater delivered by the British–Irish Ice Sheet played a fundamental role in shaping the margin including the upslope development of some of the canyon systems. The glacial influence is also suggested by the variable extent and backscatter signal of sedimentary lobes associated with the canyons. These lobes provide an indirect measurement of the amount of glaciogenic sediment delivered by the ice sheet into the Rockall Trough during the last glacial maximum. None of the sedimentary lobes demonstrates notable relief, indicating that the amount of glaciogenic sediment delivered by the British–Irish Ice Sheet into the Rockall Trough was limited. Their southward disappearance suggests a more restricted BIIS, which did not reach the shelf edge south of 54°23′ N. The various slope styles observed on the Irish margin represent snapshots of the progressive stages of slope development for a glacially-influenced passive margin and may provide a predictive model for the evolution of other such margins. 相似文献