A1 Refereed original research article in a scientific journal
Deep observations of the globular cluster M15 with the MAGIC telescopes
Authors: Acciari V. A., Ansoldi S., Antonelli L. A., Arbet Engels A., Baack D., Babić, A., Banerjee B., Barres de Almeida U., Barrio J. A., Becerra González J., Bednarek W., Bernardini E., Berti A., Besenrieder J., Bhattacharyya W., Bigongiari C., Biland A., Blanch O. Bonnoli G., Busetto G., Carosi R., Ceribella G., Cikota S., Colak S. M., Colin P., Colombo E., Contreras J. L., Cortina J., Covino S., D'Elia V., da Vela P., Dazzi F., de Angelis A., de Lotto B., Delfino M., Delgado J., di Pierro F., Do Souto Espiñera E., Domínguez A., Dominis Prester D., Dorner D., Doro M., Einecke S., Elsaesser D., Fallah Ramazani V., Fattorini A., Fernández-Barral A., Ferrara G., Fidalgo D., Foffano L., Fonseca M. V., Font L., Fruck C., Galindo D., Gallozzi S., García López R. J., Garczarczyk M., Gasparyan S., Gaug M., Giammaria P., Godinović, N., Green D., Guberman D., Hadasch D., Hahn A., Herrera J., Hoang J., Hrupec D., Inoue S., Ishio K., Iwamura Y., Kubo H., Kushida J., Kuveždić, D., Lamastra A., Lelas D., Leone F., Lindfors E., Lombardi S., Longo F., López M., López-Oramas A., Machado de Oliveira Fraga B., Maggio C., Majumdar P., Makariev M., Mallamaci M., Maneva G., Manganaro M., Mannheim K., Maraschi L., Mariotti M., Martínez M., Masuda S., Mazin D., Minev M., Miranda J. M., Mirzoyan R., Molina E., Moralejo A., Moreno V., Moretti E., Munar-Adrover P., Neustroev V., Niedzwiecki A., Nievas Rosillo M., Nigro C., Nilsson K., Ninci D., Nishijima K., Noda K., Nogués L., Nöthe M., Paiano S., Palacio J., Paneque D., Paoletti R., Paredes J. M., Pedaletti G., Peñil P., Peresano M., Persic M., Prada Moroni P. G., Prandini E., Puljak I., Garcia J. R., Rhode W., Ribó M., Rico J., Righi C., Rugliancich A., Saha L., Sahakyan N., Saito T., Satalecka K., Schweizer T., Sitarek J., Šnidarić, I., Sobczynska D., Somero A., Stamerra A., Strzys M., Surić, T., Tavecchio F., Temnikov P., Terzić, T., Teshima M., Torres-Albà N., Tsujimoto S., van Scherpenberg J., Vanzo G., Vazquez Acosta M., Vovk I., Will M., Zarić D.
Publisher: Oxford University Press
Publication year: 2019
Journal: Monthly Notices of the Royal Astronomical Society
Journal acronym: ApJ
Volume: 484
Issue: 2
First page : 2876
Last page: 2885
Number of pages: 10
ISSN: 0035-8711
eISSN: 1365-2966
DOI: https://doi.org/10.1093/mnras/stz179
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/45055673
A population of globular clusters (GCs) has been recently established by
the Fermi-LAT telescope as a new class of GeV γ-ray sources. Leptons
accelerated to TeV energies, in the inner magnetospheres of MSPs or in
their wind regions, should produce γ-rays through the inverse Compton
scattering in the dense radiation field from the huge population of
stars. We have conducted deep observations of the GC M15 with the MAGIC
telescopes and used 165 h in order to search for γ-ray emission. A
strong upper limit on the TeV γ-ray flux < 3.2× 10^{-13} cm^{-2
s^{-1}} above 300 GeV (< 0.26{{ per cent}} of the Crab nebula flux)
has been obtained. We interpret this limit as a constraint on the
efficiency of the acceleration of leptons in the magnetospheres of the
MSPs. We constrain the injection rate of relativistic leptons, ηe, from the MSPs magnetospheres and their surrounding. We conclude that ηe
must be lower than expected from the modelling of high-energy processes
in MSP inner magnetospheres. For leptons accelerated with the power-law
spectrum in the MSP wind regions, ηe is constrained to be
much lower than derived for the wind regions around classical pulsars.
These constraints are valid for the expected range of magnetic field
strengths within the GC and for the range of likely energies of leptons
injected from the inner magnetospheres, provided that the leptons are
not removed from the GC very efficiently due to advection process. We
discuss consequences of these constraints for the models of radiation
processes around millisecond pulsars.
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