MAGIC, a system of two Cherenkov telescopes located at the Roque de los Muchachos Observatory (2200 a.s.l.) in the Canary Island of La Palma, has lately been engaged in an unconventional task: the ...search for a signature of particle showers induced by earth-skimming cosmic tau neutrinos arising from the ocean, in the PeV to EeV energy range. When pointing at the sea, the MAGIC telescopes can collect data in a range of about 5 deg in zenith and 80 deg in azimuth: the analysis of the shower images from ~30 hours of data, together with the simulations of upward-going tau neutrino showers, shows that the air showers induced by tau neutrinos can be discriminated from the hadronic background coming from a similar direction. We have calculated the point source acceptance and the expected event rates, assuming an incoming
v
flux consistent with IceCube measurements, and for a sample of generic neutrino fluxes from photohadronic interactions in AGNs and GRBs. A 90% C.L. upper limit on the tau-neutrino point source flux of 2.0 × 10
–4
GeV cm
–2
s
–1
has been obtained. The presented results can also be important for future Cherenkov experiments such as the Cherenkov Telescope Array. This next generation ground-based observatory can have a much better possibility to detect
v
, given its larger FOV and much larger effective area.
Astronomy in the Time Domain Bernardini, Elisa
Science (American Association for the Advancement of Science),
02/2011, Volume:
331, Issue:
6018
Journal Article
Peer reviewed
Coordination between various instruments provides a real-time aspect to observing transient astrophysical events.
To catch the most extreme and unusual phenomena in the universe, many instruments are ...becoming increasingly coordinated, complementing each other across the energy spectrum from radio emission up to gamma-rays. As reported in this issue, the coordinated efforts of teams from the AGILE (Astro rivelatore Gamma a Immagini Leggero) (
1
) and the Fermi gamma-ray space telescopes (
2
) provide an example of the very successful multiwavelength campaign that was triggered on the spot. Within a month observers around the world responded with 16 follow-up reports. Astronomy now stands at the edge of a new frontier, enabled by modern information technology and by political and technical synergies across institutional boundaries.
A high-energy neutrino event detected by IceCube on 22 September 2017 was coincident in direction and time with a gamma-ray flare from the blazar TXS 0506+056. Prompted by this association, we ...investigated 9.5 years of IceCube neutrino observations to search for excess emission at the position of the blazar. We found an excess of high-energy neutrino events, with respect to atmospheric backgrounds, at that position between September 2014 and March 2015. Allowing for time-variable flux, this constitutes 3.5σ evidence for neutrino emission from the direction of TXS 0506+056, independent of and prior to the 2017 flaring episode. This suggests that blazars are identifiable sources of the high-energy astrophysical neutrino flux.
Current neutrino detectors are approaching a sensitivity that allows one to detect Active Galactic Nuclei (AGN) in their high state. However, the expected signals might be too weak to result in a ...significant detection. One possibility to increase the detection chance is to focus the searches during states of high electromagnetic activity, especially in the very high energy (VHE) gamma-ray regime. In this context a good knowledge of the phenomenology of gamma-ray flux variability of the known VHE AGN is crucial. Here, we present our effort in archiving and combining VHE gamma-ray lightcurves and first results including a lightcurve of Mrk 421 spanning 15 years and the estimation of an average observed high state rate.
Matrix metalloproteinase-12 (MMP-12) selective inhibitors could play a role in the treatment of lung inflammatory and cardiovascular diseases. In the present study, the previously reported ...4-methoxybiphenylsulfonyl hydroxamate and carboxylate based inhibitors (1b and 2b) were modified to enhance their selectivity for MMP-12. In the newly synthesized thioaryl derivatives, the nature of the zinc binding group (ZBG) and the sulfur oxidation state were changed. Biological assays carried out in vitro on human MMPs with the resulting compounds led to identification of a sulfide, 4a, bearing an N-1-hydroxypiperidine-2,6-dione (HPD) group as new ZBG. Compound 4a is a promising hit compound since it displayed a nanomolar affinity for MMP-12 with a marked selectivity over MMP-9, MMP-1, and MMP-14. Solution complexation studies with Zn2+ were performed to characterize the chelating abilities of the new compounds and confirmed the bidentate binding mode of HPD derivatives. X-ray crystallography studies using MMP-12 and MMP-9 catalytic domains were carried out to rationalize the biological results.
AMANDA: Selected physics results Bernardini, Elisa
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2006, Volume:
567, Issue:
2
Journal Article
Peer reviewed
Open access
Since the commissioning of the first 10 strings of the AMANDA neutrino telescope, more than nine years of data has been collected. The proof of principle of high-energy neutrino detection in ice is ...established. No positive signal of an extra-terrestrial high-energy neutrino flux have been found so far. However, the most stringent upper limits to the flux of cosmic neutrinos—respectively, diffuse, point like or associated with gamma-ray bursts—have been presented. A sample of 3329 up-going muon tracks, representing the largest statistics ever of high-energy neutrino induced events, has been collected between 2000 and 2003. A coincidence of neutrino with an anomalous high-energy gamma-ray flare has been observed from the direction of the Blazar 1ES1959+650—although the observation were not conclusive. Selected results of data taken with the AMANDA detector are here reported.
The analysis of data from a neutrino telescope is affected by several sources of systematic uncertainty—both theoretical and experimental—and their effect depend on the details of each analysis. Two ...examples of comparison between AMANDA data and corresponding Monte Carlo simulation and an example of analysis of data from down-going muons are shown, as possible approaches to estimate and reduce such uncertainty in the data analysis.
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