An Estimate of the Spectral Intensity Expected from the Molecular Bremsstrahlung Radiation in Extensive Air Showers

A detection technique of ultra-high energy cosmic rays, complementary to the fluorescence technique, would be the use of the molecular Bremsstrahlung radiation emitted by low-energy electrons left after the passage of the showers in the atmosphere. The emission mechanism is expected from quasi-elastic collisions of electrons produced in the shower by the ionisation of the molecules in the atmosphere. In this article, a detailed calculation of the spectral intensity of photons at ground level originating from the transitions between unquantised energy states of free ionisation electrons is presented. In the absence of absorption of the emitted photons in the plasma, the obtained spectral intensity is shown to be 5 10^{-26} W m^{-2}Hz^{-1} at 10 km from the shower core for a vertical shower induced by a proton of 10^{17.5} eV.Comment: 16 pages, 6 figures, accepted in Astroparticle Physics. Compared to v1 version: 1. Inclusion of ro-vibrational processes. 2. Use of more accurate ionization potential values and energy distribution of the secondary electron

Registration of the First Thermonuclear X-ray Burst from AX J1754.2-2754

During the analysis of the INTEGRAL observatory archival data we found a powerful X-ray burst, registered by JEM-X and IBIS/ISGRI telescopes on April 16, 2005 from a weak and poorly known source AX J1754.2-2754. Analysis of the burst profiles and spectrum shows, that it was a type I burst, which result from thermonuclear explosion on the surface of nutron star. It means that we can consider AX J1754.2-2754 as an X-ray burster. Certain features of burst profile at its initial stage witness of a radiation presure driven strong expansion and a corresponding cooling of the nutron star photosphere. Assuming, that the luminosity of the source at this phase was close to the Eddington limit, we estimated the distance to the burst source d=6.6+/-0.3 kpc (for hidrogen atmosphere of the neutron star) and d=9.2+/-0.4 kpc (for helium atmosphere).Comment: 12 pages, 6 figure

Solutions of the Einstein-Dirac and Seiberg-Witten Monopole Equations

We present unique solutions of the Seiberg-Witten Monopole Equations in which the U(1) curvature is covariantly constant, the monopole Weyl spinor consists of a single constant component, and the 4-manifold is a product of two Riemann surfaces of genuses p_1 and p_2. There are p_1 -1 magnetic vortices on one surface and p_2 - 1 electric ones on the other, with p_1 + p_2 \geq 2 p_1 = p_2= 1 being excluded). When p_1 = p_2, the electromagnetic fields are self-dual and one also has a solution of the coupled euclidean Einstein-Maxwell-Dirac equations, with the monopole condensate serving as cosmological constant. The metric is decomposable and the electromagnetic fields are covariantly constant as in the Bertotti-Robinson solution. The Einstein metric can also be derived from a K\"{a}hler potential satisfying the Monge-Amp\`{e}re equations.Comment: 22 pages. Rep. no: FGI-99-

Gamma-rays from Type Ia supernova SN2014J

The whole set of INTEGRAL observations of type Ia supernova SN2014J, covering the period 19-162 days after the explosion has being analyzed. For spectral fitting the data are split into "early" and "late" periods covering days 19-35 and 50-162, respectively, optimized for $^{56}$Ni and $^{56}$Co lines. As expected for the early period much of the gamma-ray signal is confined to energies below $\sim$200 keV, while for the late period it is most strong above 400 keV. In particular, in the late period $^{56}$Co lines at 847 and 1248 keV are detected at 4.7 and 4.3 $\sigma$ respectively. The lightcurves in several representative energy bands are calculated for the entire period. The resulting spectra and lightcurves are compared with a subset of models. We confirm our previous finding that the gamma-ray data are broadly consistent with the expectations for canonical 1D models, such as delayed detonation or deflagration models for a near-Chandrasekhar mass WD. Late optical spectra (day 136 after the explosion) show rather symmetric Co and Fe lines profiles, suggesting that unless the viewing angle is special, the distribution of radioactive elements is symmetric in the ejecta.Comment: 21 pages, 16 figures, accepted by Ap

Asymmetric first-price auctions with uniform distributions: analytic solutions to the general case

While auction research, including asymmetric auctions, has grown significantly in recent years, there is still little analytical solutions of first-price auctions outside the symmetric case. Even in the uniform case, Griesmer et al. (1967) and Plum (1992) find solutions only to the case where the lower bounds of the two distributions are the same. We present the general analytical solutions to asymmetric auctions in the uniform case for two bidders, both with and without a minimum bid. We show that our solution is consistent with the previously known solutions of auctions with uniform distributions. Several interesting examples are presented including a class where the two bid functions are linear. We hope this result improves our understanding of auctions and provides a useful tool for future research in auctions

Polarization of the Crab pulsar and nebula as observed by the Integral/IBIS telescope

15 pages, 2 figuresInternational audienceNeutron stars generate powerful winds of relativistic particles that form bright synchrotron nebulae around them. Polarimetry provides a unique insight into the geometry and magnetic configuration of the wind, but high-energy measurements have failed until recently. The Integral-IBIS telescope has been used in its Compton mode to search for linearly polarized emission for energies above 200 keV from the Crab nebula. The asymmetries in the instrument response are small and we obtain evidences for a strongly polarized signal at an angle parallel to the pulsar rotation axis. This result confirms the detection recently reported by Dean et al. (2008), and extends the polarization measure for all the pulsar's phases. The hard X-ray/soft $\gamma$-ray observations therefore probe the inner jets or equatorial flow of the wind. The achieved sensitivity opens a new window for polarimetric studies at energies above 200 keV

In-flight calibration of the INTEGRAL/IBIS mask

Since the release of the INTEGRAL Offline Scientific Analysis (OSA) software version 9.0, the ghost busters module has been introduced in the INTEGRAL/IBIS imaging procedure, leading to an improvement of the sensitivity around bright sources up to a factor of 7. This module excludes in the deconvolution process the IBIS/ISGRI detector pixels corresponding to the projection of a bright source through mask elements affected by some defects. These defects are most likely associated with screws and glue fixing the IBIS mask to its support. Following these major improvements introduced in OSA 9, a second order correction is still required to further remove the residual noise, now at a level of 0.2-1% of the brightest source in the field of view. In order to improve our knowledge of the IBIS mask transparency, a calibration campaign has been carried out during 2010-2012. We present here the analysis of these data, together with archival observations of the Crab and Cyg X-1, that allowed us to build a composite image of the mask defects and to investigate the origin of the residual noise in the IBIS/ISGRI images. Thanks to this study, we were able to point out a simple modification of the ISGRI analysis software that allows to significantly improve the quality of the images in which bright sources are detected at the edge of the field of view. Moreover, a refinement of the area excluded by the ghost busters module is considered, and preliminary results show improvements to be further tested. Finally, this study indicates further directions to be investigated for improving the ISGRI sensitivity, such as taking into account the thickness of the screws in the mask model or studying the possible discrepancy between the modeled and actual mask element bridges.Comment: accepted for publication in the proceedings of "An INTEGRAL view of the high-energy sky (the first 10 years)" 9th INTEGRAL Workshop, October 15-19, 2012, Paris, France, in Proceedings of Science (INTEGRAL 2012), Eds. A. Goldwurm, F. Lebrun and C. Winkler, (http://pos.sissa.it/cgi-bin/reader/conf.cgi?confid=176), id 154; 6 pages, 4 figures, see the PoS website for the full resolution versio

Do Irrelevant Sounds Impair the Maintenance of All Characteristics of Speech in Memory?

Several studies have shown that maintaining in memory some attributes of speech, such as the content or pitch of an interlocutor's message, is markedly reduced in the presence of background sounds made of spectrotemporal variations. However, experimental paradigms showing this interference have only focused on one attribute of speech at a time, and thus differ from real-life situations in which several attributes have to be memorized and maintained simultaneously. It is possible that the interference is even greater in such a case and can occur for a broader range of background sounds. We developed a paradigm in which participants had to maintain the content, pitch and speaker size of auditorily presented speech information and used various auditory distractors to generate interference. We found that only distractors with spectrotemporal variations impaired the detection, which shows that similar interference mechanisms occur whether there are one or more speech attributes to maintain in memory. A high percentage of false alarms was observed with these distractors, suggesting that spectrotemporal variations not only weaken but also modify the information maintained in memory. Lastly, we found that participants were unaware of the interference. These results are similar to those observed in the visual modalit

Hard X-ray Bursts Recorded by the IBIS Telescope of the INTEGRAL Observatory in 2003-2009

To find X-ray bursts from sources within the field of view of the IBIS/INTEGRAL telescope, we have analysed all the archival data of the telescope available at the time of writing the paper (the observations from January 2003 to April 2009). We have detected 834 hard (15-25 keV) X-ray bursts, 239 of which were simultaneously recorded by the JEM-X/INTEGRAL telescope in the standard X-ray energy range. More than 70% of all bursts (587 events) have been recorded from the well-known X-ray burster GX 354-0. We have found upper limits on the distances to their sources by assuming that the Eddington luminosity limit was reached at the brightness maximum of the brightest bursts.Comment: 18 pages, 2 figures, 2 table