WISeREP - An Interactive Supernova Data Repository

We have entered an era of massive data sets in astronomy. In particular, the number of supernova (SN) discoveries and classifications has substantially increased over the years from few tens to thousands per year. It is no longer the case that observations of a few prototypical events encapsulate most spectroscopic information about SNe, motivating the development of modern tools to collect, archive, organize and distribute spectra in general, and SN spectra in particular. For this reason we have developed the Weizmann Interactive Supernova data REPository - WISeREP - an SQL-based database (DB) with an interactive web-based graphical interface. The system serves as an archive of high quality SN spectra, including both historical (legacy) data as well as data that is accumulated by ongoing modern programs. The archive provides information about objects, their spectra, and related meta-data. Utilizing interactive plots, we provide a graphical interface to visualize data, perform line identification of the major relevant species, determine object redshifts, classify SNe and measure expansion velocities. Guest users may view and download spectra or other data that have been placed in the public domain. Registered users may also view and download data that are proprietary to specific programs with which they are associated. The DB currently holds >8000 spectra, of which >5000 are public; the latter include published spectra from the Palomar Transient Factory, all of the SUSPECT archive, the Caltech-Core-Collapse Program, the CfA SN spectra archive and published spectra from the UC Berkeley SNDB repository. It offers an efficient and convenient way to archive data and share it with colleagues, and we expect that data stored in this way will be easy to access, increasing its visibility, usefulness and scientific impact.Comment: To be published in PASP. WISeREP: http://www.weizmann.ac.il/astrophysics/wiserep

The Luminosity Function of 81 Abell Clusters from the CRoNaRio catalogues

We present the composite luminosity function (hereafter LF) of galaxies for 81 Abell clusters studied in our survey of the Northern Hemisphere, using DPOSS data processed by the CRoNaRio collaboration. The derived LF is very accurate due to the use of homogeneous data both for the clusters and the control fields and to the local estimate of the background, which takes into account the presence of large-scale structures and of foreground clusters and groups. The global composite LF is quite flat down to $M^*+5$ has a slope $\alpha\sim-1.0\pm0.2$ with minor variations from blue to red filters, and $M^*\sim-21.8,-22.0,-22.3$ mag ($H_0=50$ km s$^{-1}$ Mpc$^{-1}$) in the $g, r$ and $i$ filters, respectively (errors are detailed in the text). We find a significant difference between rich and poor clusters thus arguing in favour of a dependence of the LF on the properties of the environment.Comment: 8 pages, 5 figures. Contribution to the IAP 2000 Conference "Constructing the Universe with Clusters of Galaxies", Paris, July 200

Photometric validation of a model independent procedure to extract galaxy clusters

By means of CCD photometry in three bands (Gunn g, r, i) we investigate the existence of 12 candidate clusters extracted via a model independent peak finding algorithm (\cite{memsait}) from DPOSS data. The derived color-magnitude diagrams allow us to confirm the physical nature of 9 of the cluster candidates, and to estimate their photometric redshifts. Of the other candidates, one is a fortuitous detection of a true cluster at z~0.4, one is a false detection and the last is undecidable on the basis of the available data. The accuracy of the photometric redshifts is tested on an additional sample of 8 clusters with known spectroscopic redshifts. Photometric redshifts turn out to be accurate within z~0.01 (interquartile range).Comment: A&A in pres

Realistic calculations of nuclear disappearance lifetimes induced by neutron-antineutron oscillations

Realistic calculations of nuclear disappearance lifetimes induced by neutron-antineutron oscillations are reported for oxygen and iron, using antineutron nuclear potentials derived from a recent comprehensive analysis of antiproton atomic X-ray and radiochemical data. A lower limit of 3.3 x 10E8 s on the neutron-antineutron oscillation time is derived from the Super-Kamiokande I new lower limit of 1.77 x 10E32 yr on the neutron lifetime in oxygen. Antineutron scattering lengths in carbon and nickel, needed in trap experiments using ultracold neutrons, are calculated from updated antinucleon optical potentials at threshold, with results shown to be largely model independent.Comment: version matching PRD publication, typos and references correcte

Longtime behavior of nonlocal Cahn-Hilliard equations

Here we consider the nonlocal Cahn-Hilliard equation with constant mobility in a bounded domain. We prove that the associated dynamical system has an exponential attractor, provided that the potential is regular. In order to do that a crucial step is showing the eventual boundedness of the order parameter uniformly with respect to the initial datum. This is obtained through an Alikakos-Moser type argument. We establish a similar result for the viscous nonlocal Cahn-Hilliard equation with singular (e.g., logarithmic) potential. In this case the validity of the so-called separation property is crucial. We also discuss the convergence of a solution to a single stationary state. The separation property in the nonviscous case is known to hold when the mobility degenerates at the pure phases in a proper way and the potential is of logarithmic type. Thus, the existence of an exponential attractor can be proven in this case as well

A Very Large Array Search for 5 GHz Radio Transients and Variables at Low Galactic Latitudes

We present the results of a 5 GHz survey with the Very Large Array (VLA) and the expanded VLA, designed to search for short-lived (≾1 day) transients and to characterize the variability of radio sources at milli-Jansky levels. A total sky area of 2.66 deg^2, spread over 141 fields at low Galactic latitudes (b≅6-8 deg), was observed 16 times with a cadence that was chosen to sample timescales of days, months, and years. Most of the data were reduced, analyzed, and searched for transients in near real-time. Interesting candidates were followed up using visible light telescopes (typical delays of 1-2 hr) and the X-ray Telescope on board the Swift satellite. The final processing of the data revealed a single possible transient with a peak flux density of f_ν≅2.4 mJy. This implies a transient's sky surface density of κ(f_ν > 1.8 mJy) = 0.039^(+0.13 +0.18)_(–0.032,–0.038) deg^(–2) (1σ, 2σ confidence errors). This areal density is roughly consistent with the sky surface density of transients from the Bower et al. survey extrapolated to 1.8 mJy. Our observed transient areal density is consistent with a neutron star's origin for these events. Furthermore, we use the data to measure the source variability on timescales of days to years, and we present the variability structure function of 5 GHz sources. The mean structure function shows a fast increase on ≈1 day timescale, followed by a slower increase on timescales of up to 10 days. On timescales between 10 and 60 days, the structure function is roughly constant. We find that ≳30% of the unresolved sources brighter than 1.8 mJy are variables at the >4σ confidence level, presumably mainly due to refractive scintillation

Morphology of low-redshift compact galaxy clusters I. Shapes and radial profiles

The morphology of clusters of galaxies may be described with a set of parameters which contain information about the formation and evolutionary history of these systems. In this paper we present a preliminary study of the morphological parameters of a sample of 28 compact Abell clusters extracted from DPOSS data. The morphology of galaxy clusters is parameterized by their apparent ellipticity, position angle of the major axis, centre coordinates, core radius and beta-model power law index. Our procedure provides estimates of these parameters by simultaneously fitting them all, overcoming some of the difficulties induced by sparse data and low number statistics typical of this kind of analysis. The cluster parameters were fitted in a 3 x 3 h^-2 sqMpc region, measuring the background in a 2 <R< 2.5 h^-1Mpc annulus. We also explore the correlations between shape and profile parameters and other cluster properties. One third of this compact cluster sample has core radii smaller than 50 h^-1 kpc, i.e. near the limit that our data allow us to resolve, possibly consistent with cusped models. The remaining clusters span a broad range of core radii up to 750 h^-1 kpc. More than 80 per cent of this sample has ellipticity higher than 0.2. The alignment between the cluster and the major axis of the dominant galaxy is confirmed, while no correlation is observed with other bright cluster members. No significant correlation is found between cluster richness and ellipticity. Instead, cluster richness is found to correlate, albeit with large scatter, with the cluster core radius.[abridged]Comment: 23 pages, 17 figures, accepted for publication in MNRAS. Full paper including full resolution figures 2 and 9 at http://www.eso.org/~vstrazzu/P/ME1030fv.pd

On the Surface Structure of Strange Superheavy Nuclei

Bound, strange, neutral superheavy nuclei, stable against strong decay, may exist. A model effective field theory calculation of the surface energy and density of such systems is carried out assuming vector meson couplings to conserved currents and scalar couplings fit to data where it exists. The non-linear relativistic mean field equations are solved assuming local baryon sources. The approach is calibrated through a successful calculation of the known nuclear surface tension.Comment: 12 pages, 9 figure

Preliminary Results from the Caltech Core-Collapse Project (CCCP)

We present preliminary results from the Caltech Core-Collapse Project (CCCP), a large observational program focused on the study of core-collapse SNe. Uniform, high-quality NIR and optical photometry and multi-epoch optical spectroscopy have been obtained using the 200'' Hale and robotic 60'' telescopes at Palomar, for a sample of 50 nearby core-collapse SNe. The combination of both well-sampled optical light curves and multi-epoch spectroscopy will enable spectroscopically and photometrically based subtype definitions to be disentangled from each other. Multi-epoch spectroscopy is crucial to identify transition events that evolve among subtypes with time. The CCCP SN sample includes every core-collapse SN discovered between July 2004 and September 2005 that was visible from Palomar, found shortly (< 30 days) after explosion (based on available pre-explosion photometry), and closer than ~120 Mpc. This complete sample allows, for the first time, a study of core-collapse SNe as a population, rather than as individual events. Here, we present the full CCCP SN sample and show exemplary data collected. We analyze available data for the first ~1/3 of the sample and determine the subtypes of 13 SNe II based on both light curve shapes and spectroscopy. We discuss the relative SN II subtype fractions in the context of associating SN subtypes with specific progenitor stars.Comment: To appear in the proceedings of the meeting "The Multicoloured Landscape of Compact Objects and their Explosive Origins", Cefalu, Italy, June 2006, to be published by AIP, Eds. L. Burderi et a