| 1. |
- Clocchiatti, Alejandro, et al.
(author)
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Late-time HST photometry of SN1994I : Hints of positron annihilation energy deposition
- 2008
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In: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 120:865, s. 290-300
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Journal article (peer-reviewed)abstract
- We present multicolor Hubble Space Telescope ( HST) WFPC2 broadband observations of the Type Ic SN 1994I obtained similar to 280 d after maximum light. We measure the brightness of the SN and, relying on the detailed spectroscopic database of SN 1994I, we transform the ground-based photometry obtained at early times to the HST photometric system, deriving light curves for the WFPC2 F439W, F555W, F675W, and F814W passbands that extend from 7 days before to 280 days after maximum. We use the multicolor photometry to build a quasi-bolometric light curve of SN 1994I, and compare it with similarly constructed light curves of other supernovae. In doing so, we propose and test a scaling in energy and time that allows for a more meaningful comparison of the exponential tails of different events. Through comparison with models, we find that the late-time light curve of SN 1994I is consistent with that of spherically symmetric ejecta in homologous expansion, for which the ability to trap the gamma-rays produced by the radioactive decay of Co-56 diminishes roughly as the inverse of time squared. We also find that by the time of the HST photometry, the light curve was significantly energized by the annihilation of positrons.
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| 2. |
- Guido, Maria Angela, et al.
(author)
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Climate and vegetation dynamics of the Northern Apennines (Italy) during the Late Pleistocene and Holocene
- 2020
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In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 231, s. 1-17
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Journal article (peer-reviewed)abstract
- This study reconstructs the regional vegetation and climate dynamics between the upper Late Pleistoceneand Holocene around Pian del Lago, a coastal mountain marshland located at 831 m asl in westernLiguria (NW-Italy), based on the pollen analysis of a 13 m-long sediment core. The record provided aunique opportunity to study a poorly documented period in northern Italy and across many parts ofsouthwestern Europe. We propose an event stratigraphy based upon the identification of seven interstadials(NAI-7 to NAI-1) spanning the upper Late Pleistocene. The correlation with other terrestrialrecords in Italy, and with Mediterranean marine sequences and the Greenland ice cores, permitted acoherent reconstruction of main environmental changes from >~43,000 cal. BP. Significantly, the pollenrecord indicates the persistence of a mesophilous mountain vegetation cover, mainly composed ofQuercus (deciduous and evergreen), Abies, Fagus and Alnus over the whole time period recorded. At theLast Glacial Maximum (LGM) and during the Late Würm Lateglacial, despite the presence of steppicvegetation composed of Artemisia, woodlands dominated by Pinus, with Abies, Picea, Fagus, Alnus andBetula are present. This forest composition provides an important insight into the history of Picea insouthern Europe and Late Pleistocene refugia for mesophilous species. During the Early Holocene, Pinusis first replaced by Abies and then by deciduous Quercus and mixed temperate species as the dominantforest component. Both arboreal and herbaceous anthropogenic pollen indicators only make theirappearance during the Late Holocene, attesting to the increasing importance of human activities.
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