arXiv subjects

R. Mignani

Publications and source records attributed to R. Mignani.

42 records · Page 3Linked to original sources

arXiv2000

The BMW (Brera-Multiscale-Wavelet) Catalogue of Serendipitous X-ray Sources

In collaboration with the Observatories of Palermo and Rome and the SAX-SDC we are constructing a multi-site interactive archive system featuring specific analysis tools. In this context we developed a detection algorithm based on the Wavelet Transform (WT) and performed a systematic analysis of all ROSAT-HRI public data (~3100 observations +1000 to come). The WT is specifically suitable to detect and characterize extended sources while properly detecting point sources in very crowded fields. Moreover, the good angular resolution of HRI images allows the source extension and position to be accurately determined. This effort has produced the BMW (Brera Multiscale Wavelet) catalogue, with more than 19,000 sources detected at the 4.2 sigma level. For each source detection we have information on the X-ray flux and extension, allowing for instance to select complete samples of extended X-ray sources such as candidate clusters of galaxies or SNR's. Here we present an overview of first results from several undergoing projects which make use of the BMW catalogue.

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arXiv1999

The putative pulsar-wind nebulae of the three Musketeers PSR B1055-52, B0656+14 and Geminga revisited

We report on the analysis of archival ASCA, ROSAT and BeppoSAX data of PSR B1055-52, PSR B0656+14 and Geminga, performed in order to investigate the reality of the putative ~10-20 arcmin wide X-ray pulsar-wind nebulae recently proposed to exist around these pulsars. In all these cases, the ROSAT and/or BeppoSAX data show that the diffuse and clumpy X-ray nebulae found by ASCA can be resolved in the contribution of unidentified point sources, unlikely related to the pulsars.

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arXiv1999

Possible Effects of the Existence of the 4th Generation Neutrino

The 4th generation of fermions predicted by the phenomenology of heterotic string models can possess new strictly conserved charge, which leads, in particular, to the hypothesis of the existence of the 4th generation massive stable neutrino. The compatibility of this hypothesis with the results of underground experiment DAMA searching for weakly interactive particles of dark matter and with the EGRET measurements of galactic gamma--background at energies above 1 GeV fixes the possible mass of the 4th neutrino at the value about 50 GeV. The possibility to test the hypothesis in accelerator experiments is considered. Positron signal from the annihilation of relic massive neutrinos in the galactic halo is calculated and is shown to be accessible for planned cosmic ray experiments.

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arXiv1998

Physical Origin, Evolution and Observational Signature of Diffused Antiworld

The existence of macroscopic regions with antibaryon excess in the baryon asymmetric Universe with general baryon excess is the possible consequence of practically all models of baryosynthesis. Diffusion of matter and antimatter to the border of antimatter domains defines the minimal scale of the antimatter domains surviving to the present time. A model of diffused antiworld is considered, in which the density within the surviving antimatter domains is too low to form gravitationally bound objects. The possibility to test this model by measurements of cosmic gamma ray fluxes is discussed. The expected gamma ray flux is found to be acceptable for modern cosmic gamma ray detectors and for those planned for the near future.

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arXiv1998

Signature of relic heavy stable neutrinos in underground experiments

Considering heavy stable neutrinos of 4th generation we calculate the relic density of such neutrinos in the Universe. Taking into account the condensation of heavy neutrinos in the Galaxy and applying the results of calculations to experimental data from underground experiments on search for WIMPs in elastic neutral current scattering on nuclei we found an exclusion region of neutrino mass 60 GeV < m < 290 GeV. The bounds obtained from present underground experiments while confirming the previous bounds derived from analysis of cosmic ray spectra are more relible ones. We discuss also the first indication of elastic scattering induced by WIMP in DAMA experiment finding a very narrow window of neutrino mass 45 GeV < m < 50 GeV compatible with the possible signal rate in the detector.

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arXiv1998

Optical Observations of Isolated Neutron Stars

Only 1% of the Isolated Neutron Star (INS) population has been identified in the optical, albeit with different degrees of confidence. Optical observations of INSs are reviewed and their emission properties discussed in an evolutionary framework.

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