LONG-TERM MONITORING OF THE TeV EMISSION FROM Mrk 421 WITH THE ARGO-YBJ EXPERIMENT

Journal Article · Mon Jun 20 00:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/734/2/110· OSTI ID:21576596

Bartoli, B; Catalanotti, S ^[1]; Bernardini, P; Bleve, C ^[2]; Bi, X J; Cao, Z; Chen, S Z; Chen, Y ^[3]; Bolognino, I ^[4]; Branchini, P; Budano, A; Celio, P ^[5]; Melcarne, A K. Calabrese ^[6]; Camarri, P ^[7]; Cappa, A ^[8]; Cardarelli, R ^[9]; Cattaneo, C ^[10]; Chen, T L ^[11]; Creti, P ^[12]

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1. Dipartimento di Fisica dell'Universita di Napoli 'Federico II', Complesso Universitario di Monte Sant'Angelo, via Cinthia, 80126 Napoli (Italy)
2. Dipartimento di Fisica dell'Universita del Salento, via per Arnesano, 73100 Lecce (Italy)
3. Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, P.O. Box 918, 100049 Beijing (China)
4. Dipartimento di Fisica Nucleare e Teorica dell'Universita di Pavia, via Bassi 6, 27100 Pavia (Italy)
5. Istituto Nazionale di Fisica Nucleare, Sezione di Roma Tre, via della Vasca Navale 84, 00146 Roma (Italy)
6. Istituto Nazionale di Fisica Nucleare-CNAF, Viale Berti-Pichat 6/2, 40127 Bologna (Italy)
7. Dipartimento di Fisica dell'Universita di Roma 'Tor Vergata', via della Ricerca Scientifica 1, 00133 Roma (Italy)
8. Istituto di Fisica dello Spazio Interplanetario dell'Istituto Nazionale di Astrofisica, corso Fiume 4, 10133 Torino (Italy)
9. Istituto Nazionale di Fisica Nucleare, Sezione di Roma Tor Vergata, via della Ricerca Scientifica 1, 00133 Roma (Italy)
10. Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, via Bassi 6, 27100 Pavia (Italy)
11. Tibet University, 850000 Lhasa, Xizang (China)
12. Istituto Nazionale di Fisica Nucleare, Sezione di Lecce, via per Arnesano, 73100 Lecce (Italy)

ARGO-YBJ is an air shower detector array with a fully covered layer of resistive plate chambers. It is operated with a high duty cycle and a large field of view. It continuously monitors the northern sky at energies above 0.3 TeV. In this paper, we report a long-term monitoring of Mrk 421 over the period from 2007 November to 2010 February. This source was observed by the satellite-borne experiments Rossi X-ray Timing Explorer and Swift in the X-ray band. Mrk 421 was especially active in the first half of 2008. Many flares are observed in both X-ray and {gamma}-ray bands simultaneously. The {gamma}-ray flux observed by ARGO-YBJ has a clear correlation with the X-ray flux. No lag between the X-ray and {gamma}-ray photons longer than 1 day is found. The evolution of the spectral energy distribution is investigated by measuring spectral indices at four different flux levels. Hardening of the spectra is observed in both X-ray and {gamma}-ray bands. The {gamma}-ray flux increases quadratically with the simultaneously measured X-ray flux. All these observational results strongly favor the synchrotron self-Compton process as the underlying radiative mechanism.

• OSTI ID: 21576596
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 734; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BL LACERTAE OBJECTS
COSMIC RADIO SOURCES
ELECTROMAGNETIC RADIATION
EMISSION
ENERGY SPECTRA
GAMMA RADIATION
IONIZING RADIATIONS
MONITORING
RADIATION FLUX
RADIATIONS
SPECTRA
X RADIATION