16968642
Results of LUNASKA lunar Cherenkov observations at the ATCA
The lunar Cherenkov technique is a method to use radio-telescopes to detect ultra-high energy cosmic rays (CR) and neutrinos ($\nu$). By observing the short-duration ($\sim$few nanosecond) pulses of coherent Cherenkov radiation emitted from particle cascades via the Askaryan Effect in the Moon's outer layers (nominally the regolith), the primary particles initiating the cascades may be identified. Our collaboration (LUNASKA) aims to develop the technique to be used with the next generation of giant radio-arrays. Here, we present the results of our two preliminary UHE particle searches using this technique with three antennas at the Australia Telescope Compact Array (ATCA) during February and May 2008.
118954604
LUNASKA simultaneous neutrino searches with multiple telescopes
ICRC 2011 : 32nd International Cosmic Ray Conference 11-18 August, Beijing, China, 11 augustus 2011
119071284
Status report and future prospects on LUNASKA lunar observations with ATCA
Abstract LUNASKA (Lunar UHE Neutrino Astrophysics with the Square Kilometre Array) is a theoretical and experimental project developing the lunar Cherenkov technique for the next generation of giant radio-telescope arrays. Here we report on a series of observations with ATCA (the Australia Telescope Compact Array). Our current observations use three of the six 22 m ATCA antennas with a 600 MHz bandwidth at 1.2–1.8 GHz, analogue dedispersion filters to correct for the typical night-time ionospheric dispersion, and state-of-the-art 2 GHz FPGA-based digital pulse detection hardware. We have observed so as to maximise the UHE neutrino sensitivity in the region surrounding the galactic centre and to Centaurus A, to which current limits on the highest-energy neutrinos are relatively weak.
117844015
The endpoint formalism for the calculation of electromagnetic radiation and its applications in astroparticle physics
We present the "endpoint" formalism for the calculation of electromagnetic radiation and illustrate its applications in astroparticle physics. We use the formalism to explain why the coherent radiation from the Askaryan effect is not in general Cherenkov radiation, as the emission directly results from the time-variation of the net charge in the particle shower. Secondly, we illustrate how the formalism has been applied in the air shower radio emission code REAS3 to unify the microscopic and macroscopic views of radio emission from extensive air showers. Indeed, the formalism is completely universal and particularly well-suited for implementation in Monte Carlo codes in the time- and frequency-domains. It easily reproduces well-known "classical mechanisms" such as synchrotron radiation, Vavilov-Cherenkov radiation and transition radiation in the adequate limits, but has the advantage that it continues to work in realistic, complex situations, where the "classical mechanisms" tend to no longer apply and adhering to them can result in misleading interpretations.
31685649
SEARCHES FOR POINT-LIKE AND EXTENDED NEUTRINO SOURCES CLOSE TO THE GALACTIC CENTER USING THE ANTARES NEUTRINO TELESCOPE
A search for cosmic neutrino sources using six years of data collected by the ANTARES neutrino telescope has been performed. Clusters of muon neutrinos over the expected atmospheric background have been looked for. No clear signal has been found. The most signal-like accumulation of events is located at equatorial coordinates RA=$-$46.8$^{\circ}$ and Dec=$-$64.9$^{\circ}$ and corresponds to a 2.2$\sigma$ background fluctuation. In addition, upper limits on the flux normalization of an E$^{-2}$ muon neutrino energy spectrum have been set for 50 pre-selected astrophysical objects. Finally, motivated by an accumulation of 7 events relatively close to the Galactic Centre in the recently reported neutrino sample of the IceCube telescope, a search for point sources in a broad region around this accumulation has been carried out. No indication of a neutrino signal has been found in the ANTARES data and upper limits on the flux normalization of an E$^{-2}$ energy spectrum of neutrinos from point sources in that region have been set. The 90% confidence level upper limits on the muon neutrino flux normalization vary between 3.5 and 5.1$\times$10$^{-8}$ GeV$\,$cm$^{-2}$s$^{-1}$, depending on the exact location of the source.
122673987
Coherent Cherenkov radio emission from EeV showers in dense media through thinned simulations
Abstract We explore the feasibility of applying “thinning techniques” to the simulation of EeV electromagnetic showers in ice, salt, and the regolith of the Moon. By comparing the results of thinned showers to full simulations, we show that thinning techniques keep a good level of accuracy in the relevant shower and radio observables, and allow a considerable reduction in computing time. We apply thinning techniques to the simulation of EeV electromagnetic showers including the Landau–Pomeranchuk–Migdal effect. Our study is of the utmost importance for the determination of the sensitivity to extremely energetic neutrinos of experiments looking for radiopulses in dense media.
16680596
Ultraviolet, Optical and X-ray Observations of the Type 1a Supernova 2005am with Swift
We present ultraviolet and optical light curves in six broadband filters and grism spectra obtained by Swift's Ultraviolet/Optical Telescope for the Type Ia supernova SN 2005am. The data were collected beginning about 4 days before the B-band maximum, with excellent coverage of the rapid decline phase and later observations extending out to 69 days after the peak. The optical and near-UV light curve match well those of SN 1992A. The other UV observations constitute the first set of light curves shorter than 2500 A and allow us to compare the light curve evolution in three UV bands. One interesting feature is that the decay in the intermediate UVM2 band is shallower than in the filters on either side and may result from the bump in the interstellar extinction curve. The UV behavior of this and other low-redshift supernovae can be used to constrain theories of progenitor evolution or to interpret optical light curves of high-redshift supernovae. Using Swift's X-Ray Telescope, we also report the upper limit to SN 2005am's X-ray luminosity to be 6 × 1039 ergs s-1 in the 0.3-10 keV. This result is derived from 58 ks of exposure time spread out over 7 weeks beginning 4 days before the B-band maximum.
118376389
The Carina Project. IV. Radial Velocity Distribution
We present new and accurate radial velocity (RV) measurements of luminous stars of all ages (old horizontal branch, intermediate-age red clump, and young blue plume, as well as red giants of a range of ages: 20.6 ≤ V ≤ 22) in the Carina dwarf spheroidal galaxy, based on low-resolution spectra collected with the FORS2 multiobject slit spectrograph at the VLT. This data set was complemented by RV measurements based on medium- and high-resolution archive spectra of brighter (V 20.6) Carina targets collected with the GIRAFFE multiobject fiber spectrograph at the VLT. The combined sample includes more than 21,340 individual spectra of ≈2000 stars covering the entire body of the galaxy. The mean (RV = 220.4 ± 0.1 km s-1) and the dispersion (σ = 11.7 ± 0.1 km s-1) of the RV distribution of candidate Carina stars (~1210 objects, 180 ≤ RV ≤ 260 km s-1, 4σ) agree quite well with similar measurements available in the literature. To further improve the statistics, the accurate RV measurements recently provided by Walker et al. were also added to the current data set. We ended up with a sample of ~1370 RV measurements of candidate Carina stars that is ≈75% larger than any previous Carina RV sample. We found that the hypothesis that the Carina RV distribution is Gaussian can be discarded at 99% confidence level. The mean RV across the body of the galaxy varies from ~220 km s-1 at a distance of 7' (~200 pc) from the center to ~223 km s-1 at 13' (~400 pc, 6σ level) and flattens out to a constant value of ~221 km s-1 at larger distances (600 pc, 4σ level). Moreover, and even more importantly, we found that in the Carina regions where the mean RV is smaller, the dispersion is also smaller, and the RV distribution is more centrally peaked (i.e., the kurtosis attains larger values). The difference in mean RV is more than 4 km s-1 (9σ level) when moving from east to west and more than 3 km s-1 (~7σ level) when moving from north to south. The RV gradient appears to be in the direction of the Carina proper motion. However, this parameter is affected by large uncertainties to reach a firm conclusion. There is evidence of a secondary maximum in RV across the Carina center (|D| ≤ 200 pc). The occurrence of a secondary feature across the Carina center is also supported by the flat-topped radial distribution based on the photometric catalog. These findings are reminiscent of a substructure with transition properties that are already detected in dwarf ellipticals, and they call for confirmation by independent investigations.
53048052
TANAMI Blazars in the IceCube PeV Neutrino Fields
ABSTRACT The IceCube Collaboration has announced the discovery of a neutrino ﬂux in excess of the atmospheric background. Due to thesteeply falling atmospheric background spectrum, events at PeV energies are most likely of extraterrestrial origin. We present themultiwavelength properties of the six radio brightest blazars positionally coincident with these events using contemporaneous data ofthe TANAMI blazar sample, including high-resolution images and spectral energy distributions. Assuming the X-ray to -ray emissionoriginates in the photoproduction of pions by accelerated protons, the integrated predicted neutrino luminosity of these sources is largeenough to explain the two detected PeV events. Key words. neutrinos – galaxies: active – quasars: general 1. Introduction The detection of neutrinos at PeV energies in excess of the at-mospheric background reported by the IceCube Collaboration(Aartsen et al. 2013; IceCube Collaboration 2013) has prompteda quest to identify their extraterrestrial sources. The two eventswith PeV energies (event 20, dubbed ‘Ernie’ and event 14,‘Bert’, hereafter E20 and E14), detected between May 2010 andMay 2012
7763998
Swift UVOT detection of GRB 050318
We present observations of GRB 050318 by the Ultraviolet/Optical Telescope (UVOT) on board the Swift observatory. The data are the first detections of a gamma-ray burst (GRB) afterglow decay by the UVOT instrument, launched specifically to open a new window on these transient sources. We showcase UVOT's ability to provide multicolor photometry and the advantages of combining UVOT data with simultaneous and contemporaneous observations from the high-energy detectors on the Swift spacecraft. Multiple filters covering 1800-6000 A reveal a red source with a spectral slope steeper than the simultaneous X-ray continuum. Spectral fits indicate that the UVOT colors are consistent with dust extinction by systems at z = 1.2037 and 1.4436, redshifts where absorption systems have been preidentified. However, the data can be most easily reproduced with models containing a foreground system of neutral gas redshifted by z = 2.8 ± 0.3. For both of the above scenarios, spectral and decay slopes are, for the most part, consistent with fireball expansion into a uniform medium, provided a cooling break occurs between the energy ranges of the UVOT and Swift's X-ray instrumentation.
118186858
Experimental status of weak radiative decays
A summary of data for the weak radiative decays of hyperons (baryon{r arrow}baryon+photon) is presented. Branching ratios and asymmetry parameters are given. Comparison with theoretical models is given. (AIP)