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Deep observations of the globular cluster M15 with the MAGIC telescopes



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Barrio Uña, Juan Abel and Contreras González, José Luis and Domínguez Díaz, Alberto and Carreto Fidalgo, David Friedrich and Fonseca González, Mª Victoria and Hoang, Kim Dinh and López Moya, Marcos and Miranda Pantoja, José Miguel and Nievas Rosillo, Mireia and Peñil del Campo, Pablo and Saha, Lab and otros, ... (2019) Deep observations of the globular cluster M15 with the MAGIC telescopes. Monthly notices of the Royal Astronomical Society, 484 (2). pp. 2876-2885. ISSN 0035-8711


Official URL: http://dx.doi.org/10.1093/mnras/stz179


A population of globular clusters (GCs) has been recently established by the Fermi-LAT telescope as a new class of GeV gamma-ray sources. Leptons accelerated to TeV energies, in the inner magnetospheres of MSPs or in their wind regions, should produce gamma-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 gamma-ray emission. A strong upper limit on the TeV gamma-ray flux < 3.2 x 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, eta(e), from the MSPs magnetospheres and their surrounding. We conclude that eta(e) 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, eta(e) 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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© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. Artículo firmado por 155 autores. We would like to thank the Referee for useful comments and the Instituto de Astrofísica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The financial support of the German BMBF and MPG, the Italian INFN and INAF, the Swiss National Fund SNF, the ERDF under the Spanish Ministry of Economy and Competitiveness (MINECO) (FPA2015-69818-P, FPA2012-36668, FPA2015-68378-P, FPA2015-69210-C6-2-R, FPA2015-69210-C6-4-R, FPA2015-69210-C6-6-R, AYA2015-71042-P, AYA2016-76012-C3-1-P, ESP2015-71662-C2-2-P, FPA2017-90566-REDC), the Indian Department of Atomic Energy and the Japanese Japan Society of for the Promotion of Science (JSPS) and Ministry of Education, Culture, Sports, Science and Technology (MEXT) is gratefully acknowledged. This work was also supported by the Spanish Centro de Excelencia 'Severo Ochoa' SEV-2016-0588 and SEV-2015-0548, and Unidad de Excelencia 'María de Maeztu' MDM-2014-0369, by the Croatian Science Foundation (HrZZ) Project IP-2016-06-9782 and the University of Rijeka Project, by the German Research Fundation (DFG) Collaborative Research Centers SFB823/C4 and SFB876/C3, the Polish National Research Centre grant UMO-2016/22/M/ST9/00382 and by the Brazilian MCTIC, CNPq and FAPERJ. This work is also supported by the grant through the Polish National Research Centre No. 2014/15/B/ST9/04043.

Uncontrolled Keywords:Gamma-ray emission; Pulsar polar caps; Millisecond pulsars; Pair-creation; Omega-centauri; Major upgrade; Low-altitude; 47 tucanae; Mass-loss; Population
Subjects:Sciences > Physics > Electricity
Sciences > Physics > Electronics
ID Code:56016
Deposited On:28 Aug 2019 09:15
Last Modified:28 Aug 2019 11:09

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