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dc.contributor.authorConnolly, M.P.
dc.contributor.authorLang, Mark
dc.identifier.citationBalokovic, M,Paneque, D,Madejski, G,Furniss, A,Chiang, J,Ajell, M,Alexander, DM,Barret, D,Blandford, RD,Boggs, SE,Christensen, FE,Craig, WW,Forster, K,Giommi, P,Grefenstette, B,Hailey, C,Harrison, FA,Hornstrup, A,Kitaguchi, T,Koglin, JE,Madsen, KK,Mao, PH,Miyasaka, H,Mori, K,Perri, M,Pivovaroff, MJ,Puccetti, S,Rana, V,Stern, D,Tagliaferri, G,Urry, CM,Estergaard, NJW,Zhang, WW,Zoglauer, A,Archambault, S,Archer, A,Barnacka, A,Benbow, W,Bird, R,Buckley, JH,Bugaev, V,Cerruti, M,Chen, X,Ciupik, L,Connolly, MP,Cui, W,Dickinson, HJ,Dumm, J,Eisch, JD,Falcone, A,Feng, Q,Finley, JP,Fleischhack, H,Fortson, L,Griffin, S,Griffiths, ST,Grube, J,Gyuk, G,Huetten, M,Hakansson, N,Holder, J,Humensky, TB,Johnson, CA,Kaaret, P,Kertzman, M,Khassen, Y,Kieda, D,Krause, M,Krennrich, F,Lang, MJ,Maier, G,McArthur, (2016) 'MULTIWAVELENGTH STUDY OF QUIESCENT STATES OF Mrk 421 WITH UNPRECEDENTED HARD X-RAY COVERAGE PROVIDED BY NuSTAR IN 2013'. Astrophysical Journal, 819 .en_IE
dc.description.abstractWe present coordinated multiwavelength observations of the bright, nearby BL Lacertae object Mrk 421 taken in 2013 January-March, involving GASP-WEBT, Swift, NuSTAR, Fermi-LAT, MAGIC, VERITAS, and other collaborations and instruments, providing data from radio to very high energy. (VHE).-ray bands. NuSTAR yielded previously unattainable sensitivity in the 3-79. keV range, revealing that the spectrum softens when the source is dimmer until the X-ray spectral shape saturates into a steep Gamma approximate to 3 power law, with no evidence for an exponential cutoff or additional hard components up to similar to 80. keV. For the first time, we observed both the synchrotron and the inverse-Compton peaks of the spectral energy distribution (SED) simultaneously shifted to frequencies below the typical quiescent state by an order of magnitude. The fractional variability as a function of photon energy shows a double-bump structure that relates to the two bumps of the broadband SED. In each bump, the variability increases with energy, which, in the framework of the synchrotron self-Compton model, implies that the electrons with higher energies are more variable. The measured multi band variability, the significant X-ray-to-VHE correlation down to some of the lowest fluxes ever observed in both bands, the lack of correlation between optical/UV and X-ray flux, the low degree of polarization and its significant (random) variations, the short estimated electron cooling time, and the significantly longer variability timescale observed in the NuSTAR light curves point toward in situ electron acceleration and suggest that there are multiple compact regions contributing to the broadband emission of Mrk 421 during low-activity states.en_IE
dc.publisherIOP Publishingen_IE
dc.relation.ispartofAstrophysical Journalen
dc.subjectBL Lacertae objects: individual (Markarian 421)en_IE
dc.subjectradiation mechanisms: nonthermalen_IE
dc.subjectX-rays: galaxiesen_IE
dc.subjectGamma rays: generalen_IE
dc.subjectRadiation mechanismsen_IE
dc.subjectGamma raysen_IE
dc.subjectActive galactic nucleien_IE
dc.subjectLarge area telescopeen_IE
dc.subjectBL lacertae objectsen_IE
dc.subjectParticle accelerationen_IE
dc.subjectLAC objectsen_IE
dc.subjectCorrelated variabilityen_IE
dc.subjectTEV blazarsen_IE
dc.subjectElectron accelerationen_IE
dc.subjectMagnetic reconnectionen_IE
dc.subjectBackground radiationen_IE
dc.titleMultiwavelength study of quiescent states of MRK 421 with unprecedented hard x-ray coverage provided by NuSTAR in 2013en_IE
dc.local.contactMark Lang, School Of Physics, Room 147, Arts/Science Building, Nui Galway. 3241 Email:

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