Supernova 1996L: evidence of a strong wind episode before the explosion

Observations of the type II SN 1996L reveal the presence of a slowly expanding (V~700$ km/s) shell at ~ 10^(16) cm from the exploding star. Narrow emission features are visible in the early spectra superposed on the normal SN spectrum. Within about two months these features develop narrow symmetric P-Cygni profiles. About 100 days after the explosion the light curve suddenly flattens, the spectral lines broaden and the Halpha flux becomes larger than what is expected from a purely radioactive model. These events are interpreted as signatures of the onset of the interaction between the fast moving ejecta and a slowly moving outer shell of matter ejected before the SN explosion. At about 300 days the narrow lines disappear and the flux drops until the SN fades away, suggesting that the interaction phase is over and that the shell has been swept away. Simple calculations show that the superwind episode started 9 yr before the SN explosion and lasted 6 yr, with an average dM/dt=10^(-3) M_solar/yr. Even at very late epochs (up to day 335) the typical forbidden lines of [OI], CaII], [FeII] remain undetected or very weak. Spectra after day 270 show relatively strong emission lines of HeI. These lines are narrower than other emission lines coming from the SN ejecta, but broader than those from the CSM. These high excitation lines are probably the result of non-thermal excitation and ionization caused by the deposition of the gamma-rays emitted in the decay of radioactive material mixed in the He layer.Comment: 8 pages, 6 figures, Latex, To appear in M.N.R.A.

Lack of observational evidence for quantum structure of space-time at Plank scales

It has been noted (Lieu & Hillmann, 2002) that the cumulative affect of Planck-scale phenomenology, or the structure of space-time at extremely small scales, can be lead to the loss of phase of radiation emitted at large distances from the observer. We elaborate on such an approach and demonstrate that such an effect would lead to an apparent blurring of distant point-sources. Evidence of the diffraction pattern from the HST observations of SN 1994D and the unresolved appearance of a Hubble Deep Field galaxy at z=5.34 lead us to put stringent limits on the effects of Planck-scale phenomenology.Comment: 12 pages, 3 figures, accepter for ApJ

The Asiago Supernova Catalogue- 10 years after

Ten years after the publication of the previous release, we present a new edition of the Asiago Supernova Catalogue updated to December 31, 1998 and containing data for 1447 supernovae and their parent galaxies\footnote{Tables 1 and 2 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html}. In addition to list the data for a large number of new SNe, we made an effort to search the literature for new information on past SNe as well. We also tried to update and homogenize the data for the parent galaxies. To allow a global view of the Catalogue, a few descriptive figures and a summary table is reported. The present Catalogue is intended as a large and modern database for statistical studies on the supernova phenomenon.Comment: 6 pages. To be published in A&A supplement. Enclosed as postscript files are the full lists in chronological (snean.ps) and R.A. (snear.ps) order (to be published only in electronic form.

Independent circuits in basal ganglia and cortex for the processing of reward and precision feedback

In order to understand human decision making it is necessary to understand how the brain uses feedback to guide goal-directed behavior. The ventral striatum (VS) appears to be a key structure in this function, responding strongly to explicit reward feedback. However, recent results have also shown striatal activity following correct task performance even in the absence of feedback. This raises the possibility that, in addition to processing external feedback, the dopamine-centered reward circuit might regulate endogenous reinforcement signals, like those triggered by satisfaction in accurate task performance. Here we use functional magnetic resonance imaging (fMRI) to test this idea. Participants completed a simple task that garnered both reward feedback and feedback about the precision of performance. Importantly, the design was such that we could manipulate information about the precision of performance within different levels of reward magnitude. Using parametric modulation and functional connectivity analysis we identified brain regions sensitive to each of these signals. Our results show a double dissociation: frontal and posterior cingulate regions responded to explicit reward but were insensitive to task precision, whereas the dorsal striatum - and putamen in particular - was insensitive to reward but responded strongly to precision feedback in reward-present trials. Both types of feedback activated the VS, and sensitivity in this structure to precision feedback was predicted by personality traits related to approach behavior and reward responsiveness. Our findings shed new light on the role of specific brain regions in integrating different sources of feedback to guide goal-directed behavior

Supernova Classes and Subclasses

The discovery of many objects with unprecedented, amazing observational characteristics caused the last decade to be the most prolific period for the supernova research. Many of these new supernovae are transitional objects between existing classes, others well enter within the defined classes, but still show unique properties. This makes the traditional classification scheme inadequate to take into account the overall SN variety and, consequently, requires the introduction of new subclasses.Comment: 10 pages, 2 figure, review for "Supernova 1987A: 20 Years After: Supernovae and Gamma-Ray Bursters" AIP, New York, eds. S. Immler, K.W. Weiler, and R. McCra