140 research outputs found
GALPROP: modeling cosmic ray propagation and associated interstellar emissions
Research in many areas of modern physics and astrophysics such as, e.g.,
indirect searches for dark matter (DM), particle acceleration in SNR shocks,
and the spectrum and origin of extragalactic gamma-ray background, rely heavily
on studies of cosmic rays (CRs) and associated diffuse emissions. New or
improved instrumentation to explore these open issues is ready or under
development. A fleet of ground-based, balloon-borne, and spacecraft instruments
measures many CR species, gamma rays, radio, and synchrotron emission.
Exploiting the data collected by the scientific missions to the fullest
requires reliable and detailed calculations using a numerical model. GALPROP is
the current state-of-the-art numerical CR propagation code that has become a
standard analysis tool in CR and diffuse gamma-ray research. It uses
astrophysical information, nuclear and particle data as input to
self-consistently predict CRs, gamma rays, synchrotron emission and other
observables. This paper reviews recent GALPROP developments and results.Comment: Invited talk at 8th Workshop on Science with the New Generation of
High Energy Gamma-ray Experiments: Gamma-ray Astrophysics in the
Multimessenger Context (SciNeGHE2010, Trieste, Sept. 8-10, 2010); Il Nuovo
Cimento C, v. 034, published onlin
Identifying Dark Matter Burners in the Galactic center
If the supermassive black hole (SMBH) at the center of our Galaxy grew
adiabatically, then a dense "spike" of dark matter is expected to have formed
around it. Assuming that dark matter is composed primarily of weakly
interacting massive particles (WIMPs), a star orbiting close enough to the SMBH
can capture WIMPs at an extremely high rate. The stellar luminosity due to
annihilation of captured WIMPs in the stellar core may be comparable to or even
exceed the luminosity of the star due to thermonuclear burning. The model thus
predicts the existence of unusual stars, i.e. "WIMP burners", in the vicinity
of an adiabatically grown SMBH. We find that the most efficient WIMP burners
are stars with degenerate electron cores, e.g. white dwarfs (WD) or degenerate
cores with envelopes. If found, such stars would provide evidence for the
existence of particle dark matter and could possibly be used to establish its
density profile. In our previous paper we computed the luminosity from WIMP
burning for a range of dark matter spike density profiles, degenerate core
masses, and distances from the SMBH. Here we compare our results with the
observed stars closest to the Galactic center and find that they could be
consistent with WIMP burners in the form of degenerate cores with envelopes. We
also cross-check the WIMP burner hypothesis with the EGRET observed flux of
gamma-rays from the Galactic center, which imposes a constraint on the dark
matter spike density profile and annihilation cross-section. We find that the
EGRET data is consistent with the WIMP burner hypothesis. New high precision
measurements by GLAST will confirm or set stringent limits on a dark matter
spike at the Galactic center, which will in turn support or set stringent
limits on the existence of WIMP burners at the Galactic center.Comment: 2 pages, 2 figures; to appear in the Proc. of the First Int. GLAST
Symp. (Stanford, Feb. 5-8, 2007), eds. S.Ritz, P.F.Michelson, and C.Meegan,
AIP Conf. Pro
Direct measurements of cosmic rays and their possible interpretations
The last two decades have brought spectacular advances in astrophysics of
cosmic rays (CRs) and space- and ground-based astronomy. Launches of missions
that employ forefront detector technologies enabled measurements with large
effective areas, wide fields of view, and precision that we recently could not
even dream of. Meanwhile, interpretation of the individual slices of
information about the internal working of the Milky Way provided by such
experiments poses challenges to the traditional astrophysical models. New
mysteries arise in the composition and spectra of CR species at low and high
energies, in the energy range where we thought the main features were already
understood fairly well. This accumulation of unsolved puzzles highlights the
peculiarity of the current epoch and means that major breakthroughs are still
ahead. In my talk, I review the current state of direct measurements of CRs and
discuss their possible interpretations. Unfortunately, many important ideas and
publications are not discussed here due to the space limitations.Comment: 24 pages, invited review talk, Proceedings of the 38th International
Cosmic Ray Conference (ICRC2023), 26 July - 3 August, 2023, Nagoya, Japan.
The DOI link provides an access to the slides (Supplementary files
Designing Algorithms for Optimization of Parameters of Functioning of Intelligent System for Radionuclide Myocardial Diagnostics
The influence of the number of complex components of Fast Fourier transformation in analyzing the polar maps of radionuclide examination of myocardium at rest and stress on the functional efficiency of the system of diagnostics of pathologies of myocardium was explored, and there were defined their optimum values in the information sense, which allows increasing the efficiency of the algorithms of forming the diagnostic decision rules by reducing the capacity of the dictionary of features of recognition.The information-extreme sequential cluster algorithms of the selection of the dictionary of features, which contains both quantitative and category features were developed and the results of their work were compared. The modificatios of the algorithms of the selection of the dictionary were suggested, which allows increasing both the search speed of the optimal in the information sense dictionary and reducing its capacity by 40 %. We managed to get the faultless by the training matrix decision rules, the accuracy of which is in the exam mode asymptotically approaches the limit.It was experimentally confirmed that the implementation of the proposed algorithm of the diagnosing system training has allowed to reduce the minimum representative volume of the training matrix from 300 to 81 vectors-implementations of the classes of recognition of the functional myocardium state
A New Determination Of The Diffuse Galactic and Extragalactic Gamma-Ray Emission
The GALPROP model for cosmic-ray propagation is able to make explicit
predictions for the distribution of galactic diffuse gamma-rays. We compare
different propagation models with gamma-ray spectra measured by EGRET for
various regions of the sky. This allows sensitive tests of alternative
explanations for the apparent excess emission observed at GeV gamma-rays. We
find that a population of hard-spectrum gamma-ray sources cannot be solely
responsible for the excess since it also appears at high latitudes; on the
other hand a hard cosmic-ray electron spectrum cannot explain the gamma-ray
excess in the inner Galaxy. By normalizing the cosmic ray spectra within
reasonable bounds under preservation of their shape we are able to obtain our
best prediction of the Galactic component of diffuse gamma rays, and show that
away from the Galactic plane it gives an accurate prediction of the observed
gamma-ray intensities. On this basis we reevaluate the extragalactic gamma-ray
background. We find that for some energies previous work underestimated the
Galactic contribution and hence overestimated the background. The new EGRB
spectrum shows a positive curvature similar to that expected for models of the
extragalactic gamma-ray emission based on contributions from unresolved
blazars.Comment: 6 pages, 3 figures, 1 tabl
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