Gamma-ray flaring activity of NGC1275 in 2016–2017 measured by MAGIC
|Author:||Ansoldi, S.1,2,3,4,5,6; Antonelli, L. A.7; Arcaro, C.8,9;|
1Univ Udine, I-33100 Udine, Italy.
2INFN Trieste, I-33100 Udine, Italy.
3Univ Tokyo, Japanese MAGIC Consortium ICRR, Chiba, Japan.
4Kyoto Univ, Dept Phys, Kyoto 6068502, Japan.
5Tokai Univ, Kanagawa, Japan.
6Univ Tokushima, Tokushima, Japan.
7Natl Inst Astrophys INAF, I-00136 Rome, Italy.
8Univ Padua, Padua, Italy.
9INFN, Padua, Italy.
10Tech Univ Dortmund, D-44221 Dortmund, Germany.
11Univ Rijeka, Croatian MAGIC Consortium, Rijeka 51000, Croatia.
12Univ Split, FESB, Split 21000, Croatia.
13Univ Zagreb, FER, Zagreb 10000, Croatia.
14Univ Osijek, Osijek 31000, Croatia.
15Rudjer Boskovic Inst, Zagreb 10000, Croatia.
16HBNI, Saha Inst Nucl Phys, 1 AF Bidhannagar,Sect 1, Kolkata 700064, India.
17Max Planck Inst Phys & Astrophys, D-80805 Munich, Germany.
18URCA, CBPF, BR-22290180 Rio De Janeiro, RJ, Brazil.
19Univ Complutense, Unidad Particulas & Cosmol UPARCOS, E-28040 Madrid, Spain.
20Inst Astrofis Canarias, Tenerife 38206, Spain.
21Univ La Laguna, Dpto Astrofis, E-38206 Tenerife, Spain.
22Univ Lodz, Dept Astrophys, PL-90236 Lodz, Poland.
23Deutsch Elektronen Synchrotron DESY, D-15738 Zeuthen, Germany.
24Humboldt Univ, Inst Phys, D-12489 Berlin, Germany.
25Univ Trieste, Dipartimento Fis, I-34127 Trieste, Italy.
26Swiss Fed Inst Technol, CH-8093 Zurich, Switzerland.
27BIST, IFAE, Bellaterra 08193, Spain.
28Univ Siena, I-53100 Siena, Italy.
29INFN Pisa, I-53100 Siena, Italy.
30PIC, Bellaterra 08193, Barcelona, Spain.
31Univ Wurzburg, D-97074 Wurzburg, Germany.
32Univ Turku, Finnish MAGIC Consortium Tuorla Observ, Vaisalantie 20, FI-21500 Piikkio, Finland.
33Univ Turku, Finnish Ctr Astron ESO FINCA, Vaisalantie 20, FI-21500 Piikkio, Finland.
34Univ Oulu, Astron Div, Oulu 90014, Finland.
35Univ Autonoma Barcelona, Dept Fis, Bellaterra 08193, Spain.
36Univ Autonoma Barcelona, CERES IEEC, Bellaterra 08193, Spain.
37Univ Barcelona, ICC, IEEC UB, E-08028 Barcelona, Spain.
38Polish Acad Sci, Inst Nucl Phys, PL-31342 Krakow, Poland.
39Bulgarian Acad Sci, Inst Nucl Res & Nucl Energy, Sofia 1784, Bulgaria.
40INAF Trieste, Trieste, Italy.
41Univ Bologna, Dept Phys & Astron, Bologna, Italy.
42Univ Pisa, I-56126 Pisa, Italy.
43INFN Pisa, I-56126 Pisa, Italy.
44Heidelberg Univ, Zentrum Astron, Landessternwarte, Konigstuhl, D-69117 Heidelberg, Germany.
45Univ Turku, Dept Phys & Astron, Tuorla Observ, Turku, Finland.
|Online Access:||PDF Full Text (PDF, 0.5 MB)|
|Persistent link:|| http://urn.fi/urn:nbn:fi-fe2019093030646
|Publish Date:|| 2019-09-30
We report on the detection of flaring activity from the Fanaroff-Riley I radio galaxy NGC 1275 in very-high-energy (VHE, E > 100 GeV) gamma rays with the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes. The observations were performed between 2016 September and 2017 February, as part of a monitoring programme. The brightest outburst, with ∼1.5 times the Crab Nebula flux above 100 GeV (C.U.), was observed during the night between 2016 December 31 and 2017 January 1. The flux is fifty times higher than the mean flux previously measured in two observational campaigns between 2009 October and 2010 February and between 2010 August and 2011 February. Significant variability of the day-by-day light curve was measured. The shortest flux-doubling timescale was found to be of (611 ± 101) min. The spectra calculated for this period are harder and show a significant curvature with respect to the ones obtained in the previous campaigns. The combined spectrum of the MAGIC data during the strongest flare state and simultaneous data from the Fermi-LAT around 2017 January 1 follows a power law with an exponential cutoff at the energy (492 ± 35) GeV. We further present simultaneous optical flux density measurements in the R-band obtained with the Kungliga Vetenskaps Akademien (KVA) telescope and investigate the correlation between the optical and gamma-ray emission. Due to possible internal pair-production, the fast flux variability constrains the Doppler factor to values that are inconsistent with a large viewing angle as observed in the radio band. We investigate different scenarios for the explanation of fast gamma-ray variability, namely emission from magnetospheric gaps, relativistic blobs propagating in the jet (mini-jets), or an external cloud (or star) entering the jet. We find that the only plausible model to account for the luminosities here observed would be the production of gamma rays in a magnetospheric gap around the central black hole, only in the eventuality of an enhancement of the magnetic field threading the hole from its equipartition value with the gas pressure in the accretion flow. The observed gamma-ray flare therefore challenges all the discussed models for fast variability of VHE gamma-ray emission in active galactic nuclei.
Astronomy and astrophysics
|Type of Publication:||
A1 Journal article – refereed
|Field of Science:||
115 Astronomy and space science
The financial support of the German BMBF and MPG, the Italian INFN and INAF, the Swiss National Fund SNF, the ERDF under the Spanish 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, CSD2009-00064), and the Japanese JSPS and MEXT is gratefully acknowledged. This work was also supported by the Spanish Centro de Excelencia “Severo Ochoa” SEV-2012-0234 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 188.8.131.52.02, by the 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.
© ESO 2018.