MULTIWAVELENGTH STUDY OF QUIESCENT STATES OF MRK 421 WITH UNPRECEDENTED HARD X-RAY COVERAGE PROVIDED BY NuSTAR IN 2013

M. Baloković, D. Paneque, G. Madejski, A. Furniss, J. Chiang, M. Ajello, D. M. Alexander, D. Barret, R. D. Blandford, S. E. Boggs, F. E. Christensen, W. W. Craig, K. Forster, P. Giommi, B. Grefenstette, C. Hailey, F. A. Harrison, A. Hornstrup, T. Kitaguchi, J. E. Koglin & 284 others K. K. Madsen, P. H. Mao, H. Miyasaka, K. Mori, M. Perri, M. J. Pivovaroff, S. Puccetti, V. Rana, D. Stern, G. Tagliaferri, C. M. Urry, N. J. Westergaard, W. W. Zhang, A. Zoglauer, S. Archambault, A. Archer, A. Barnacka, W. Benbow, R. Bird, J. H. Buckley, V. Bugaev, M. Cerruti, X. Chen, L. Ciupik, M. P. Connolly, W. Cui, H. J. Dickinson, J. Dumm, J. D. Eisch, Abraham David Falcone, Q. Feng, J. P. Finley, H. Fleischhack, L. Fortson, S. Griffin, S. T. Griffiths, J. Grube, G. Gyuk, M. Huetten, N. Håkansson, J. Holder, T. B. Humensky, C. A. Johnson, P. Kaaret, M. Kertzman, Y. Khassen, D. Kieda, M. Krause, F. Krennrich, M. J. Lang, G. Maier, S. McArthur, K. Meagher, P. Moriarty, T. Nelson, D. Nieto, R. A. Ong, N. Park, M. Pohl, A. Popkow, E. Pueschel, P. T. Reynolds, G. T. Richards, E. Roache, M. Santander, G. H. Sembroski, K. Shahinyan, A. W. Smith, D. Staszak, I. Telezhinsky, N. W. Todd, J. V. Tucci, J. Tyler, S. Vincent, A. Weinstein, A. Wilhelm, D. A. Williams, B. Zitzer, M. L. Ahnen, S. Ansoldi, L. A. Antonelli, P. Antoranz, A. Babic, B. Banerjee, P. Bangale, U. Barres De Almeida, J. A. Barrio, J. Becerra González, W. Bednarek, E. Bernardini, B. Biasuzzi, A. Biland, O. Blanch, S. Bonnefoy, G. Bonnoli, F. Borracci, T. Bretz, E. Carmona, A. Carosi, A. Chatterjee, R. Clavero, P. Colin, E. Colombo, J. L. Contreras, J. Cortina, S. Covino, P. Da Vela, F. Dazzi, A. De Angelis, B. De Lotto, E. De Ońa Wilhelmi, C. Delgado Mendez, F. Di Pierro, D. Dominis Prester, D. Dorner, M. Doro, S. Einecke, D. Elsaesser, A. Fernández-Barral, D. Fidalgo, M. V. Fonseca, L. Font, K. Frantzen, C. Fruck, D. Galindo, R. J.García López, M. Garczarczyk, D. Garrido Terrats, M. Gaug, P. Giammaria, D. Glawion, N. Godinović, A. González Muñoz, D. Guberman, A. Hahn, Y. Hanabata, M. Hayashida, J. Herrera, J. Hose, D. Hrupec, G. Hughes, W. Idec, K. Kodani, Y. Konno, H. Kubo, J. Kushida, A. La Barbera, D. Lelas, E. Lindfors, S. Lombardi, F. Longo, M. López, R. López-Coto, A. López-Oramas, E. Lorenz, P. Majumdar, M. Makariev, K. Mallot, G. Maneva, M. Manganaro, K. Mannheim, L. Maraschi, B. Marcote, M. Mariotti, M. Martínez, D. Mazin, U. Menzel, J. M. Miranda, R. Mirzoyan, A. Moralejo, E. Moretti, D. Nakajima, V. Neustroev, A. Niedzwiecki, M. Nievas Rosillo, K. Nilsson, K. Nishijima, K. Noda, R. Orito, A. Overkemping, S. Paiano, J. Palacio, M. Palatiello, R. Paoletti, J. M. Paredes, X. Paredes-Fortuny, M. Persic, J. Poutanen, P. G.Prada Moroni, E. Prandini, I. Puljak, W. Rhode, M. Ribó, J. Rico, J. Rodriguez Garcia, T. Saito, K. Satalecka, V. Scapin, C. Schultz, T. Schweizer, S. N. Shore, A. Sillanpää, J. Sitarek, I. Snidaric, D. Sobczynska, A. Stamerra, T. Steinbring, M. Strzys, L. Takalo, H. Takami, F. Tavecchio, P. Temnikov, T. Terzić, D. Tescaro, M. Teshima, J. Thaele, D. F. Torres, T. Toyama, A. Treves, V. Verguilov, I. Vovk, J. E. Ward, M. Will, M. H. Wu, R. Zanin, J. Perkins, F. Verrecchia, C. Leto, M. Böttcher, M. Villata, C. M. Raiteri, J. A. Acosta-Pulido, R. Bachev, A. Berdyugin, D. A. Blinov, M. I. Carnerero, W. P. Chen, P. Chinchilla, G. Damljanovic, C. Eswaraiah, T. S. Grishina, S. Ibryamov, B. Jordan, S. G. Jorstad, M. Joshi, E. N. Kopatskaya, O. M. Kurtanidze, S. O. Kurtanidze, E. G. Larionova, L. V. Larionova, V. M. Larionov, G. Latev, H. C. Lin, A. P. Marscher, A. A. Mokrushina, D. A. Morozova, M. G. Nikolashvili, E. Semkov, P. S. Smith, A. Strigachev, Yu V. Troitskaya, I. S. Troitsky, O. Vince, J. Barnes, T. Güver, J. W. Moody, A. C. Sadun, S. Sun, T. Hovatta, J. L. Richards, W. Max-Moerbeck, A. C.R. Readhead, A. Lähteenmäki, M. Tornikoski, J. Tammi, V. Ramakrishnan, R. Reinthal, E. Angelakis, L. Fuhrmann, I. Myserlis, V. Karamanavis, A. Sievers, H. Ungerechts, J. A. Zensus

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Abstract

We 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) γ-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 Γ ≈ 3 power law, with no evidence for an exponential cutoff or additional hard components up 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.

Original languageEnglish (US)
Article number156
JournalAstrophysical Journal
Volume819
Issue number2
DOIs
StatePublished - Mar 10 2016

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energy
spectral energy distribution
x rays
synchrotrons
Global Air Sampling Program
electron
broadband
BL Lacertae objects
electron acceleration
light curve
rays
electrons
cut-off
cooling
power law
sensitivity
polarization
photons
radio
timescale

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Baloković, M., Paneque, D., Madejski, G., Furniss, A., Chiang, J., Ajello, M., ... Zensus, J. A. (2016). MULTIWAVELENGTH STUDY OF QUIESCENT STATES OF MRK 421 WITH UNPRECEDENTED HARD X-RAY COVERAGE PROVIDED BY NuSTAR IN 2013. Astrophysical Journal, 819(2), [156]. https://doi.org/10.3847/0004-637X/819/2/156
Baloković, M. ; Paneque, D. ; Madejski, G. ; Furniss, A. ; Chiang, J. ; Ajello, M. ; Alexander, D. M. ; Barret, D. ; Blandford, R. D. ; Boggs, S. E. ; Christensen, F. E. ; Craig, W. W. ; Forster, K. ; Giommi, P. ; Grefenstette, B. ; Hailey, C. ; Harrison, F. A. ; Hornstrup, A. ; Kitaguchi, T. ; Koglin, J. E. ; Madsen, K. K. ; Mao, P. H. ; Miyasaka, H. ; Mori, K. ; Perri, M. ; Pivovaroff, M. J. ; Puccetti, S. ; Rana, V. ; Stern, D. ; Tagliaferri, G. ; Urry, C. M. ; Westergaard, N. J. ; Zhang, W. W. ; Zoglauer, A. ; Archambault, S. ; Archer, A. ; Barnacka, A. ; Benbow, W. ; Bird, R. ; Buckley, J. H. ; Bugaev, V. ; Cerruti, M. ; Chen, X. ; Ciupik, L. ; Connolly, M. P. ; Cui, W. ; Dickinson, H. J. ; Dumm, J. ; Eisch, J. D. ; Falcone, Abraham David ; Feng, Q. ; Finley, J. P. ; Fleischhack, H. ; Fortson, L. ; Griffin, S. ; Griffiths, S. T. ; Grube, J. ; Gyuk, G. ; Huetten, M. ; Håkansson, N. ; Holder, J. ; Humensky, T. B. ; Johnson, C. A. ; Kaaret, P. ; Kertzman, M. ; Khassen, Y. ; Kieda, D. ; Krause, M. ; Krennrich, F. ; Lang, M. J. ; Maier, G. ; McArthur, S. ; Meagher, K. ; Moriarty, P. ; Nelson, T. ; Nieto, D. ; Ong, R. A. ; Park, N. ; Pohl, M. ; Popkow, A. ; Pueschel, E. ; Reynolds, P. T. ; Richards, G. T. ; Roache, E. ; Santander, M. ; Sembroski, G. H. ; Shahinyan, K. ; Smith, A. W. ; Staszak, D. ; Telezhinsky, I. ; Todd, N. W. ; Tucci, J. V. ; Tyler, J. ; Vincent, S. ; Weinstein, A. ; Wilhelm, A. ; Williams, D. A. ; Zitzer, B. ; Ahnen, M. L. ; Ansoldi, S. ; Antonelli, L. A. ; Antoranz, P. ; Babic, A. ; Banerjee, B. ; Bangale, P. ; De Almeida, U. Barres ; Barrio, J. A. ; González, J. Becerra ; Bednarek, W. ; Bernardini, E. ; Biasuzzi, B. ; Biland, A. ; Blanch, O. ; Bonnefoy, S. ; Bonnoli, G. ; Borracci, F. ; Bretz, T. ; Carmona, E. ; Carosi, A. ; Chatterjee, A. ; Clavero, R. ; Colin, P. ; Colombo, E. ; Contreras, J. L. ; Cortina, J. ; Covino, S. ; Da Vela, P. ; Dazzi, F. ; De Angelis, A. ; De Lotto, B. ; De Ońa Wilhelmi, E. ; Mendez, C. Delgado ; Di Pierro, F. ; Prester, D. Dominis ; Dorner, D. ; Doro, M. ; Einecke, S. ; Elsaesser, D. ; Fernández-Barral, A. ; Fidalgo, D. ; Fonseca, M. V. ; Font, L. ; Frantzen, K. ; Fruck, C. ; Galindo, D. ; López, R. J.García ; Garczarczyk, M. ; Terrats, D. Garrido ; Gaug, M. ; Giammaria, P. ; Glawion, D. ; Godinović, N. ; González Muñoz, A. ; Guberman, D. ; Hahn, A. ; Hanabata, Y. ; Hayashida, M. ; Herrera, J. ; Hose, J. ; Hrupec, D. ; Hughes, G. ; Idec, W. ; Kodani, K. ; Konno, Y. ; Kubo, H. ; Kushida, J. ; La Barbera, A. ; Lelas, D. ; Lindfors, E. ; Lombardi, S. ; Longo, F. ; López, M. ; López-Coto, R. ; López-Oramas, A. ; Lorenz, E. ; Majumdar, P. ; Makariev, M. ; Mallot, K. ; Maneva, G. ; Manganaro, M. ; Mannheim, K. ; Maraschi, L. ; Marcote, B. ; Mariotti, M. ; Martínez, M. ; Mazin, D. ; Menzel, U. ; Miranda, J. M. ; Mirzoyan, R. ; Moralejo, A. ; Moretti, E. ; Nakajima, D. ; Neustroev, V. ; Niedzwiecki, A. ; Rosillo, M. Nievas ; Nilsson, K. ; Nishijima, K. ; Noda, K. ; Orito, R. ; Overkemping, A. ; Paiano, S. ; Palacio, J. ; Palatiello, M. ; Paoletti, R. ; Paredes, J. M. ; Paredes-Fortuny, X. ; Persic, M. ; Poutanen, J. ; Moroni, P. G.Prada ; Prandini, E. ; Puljak, I. ; Rhode, W. ; Ribó, M. ; Rico, J. ; Garcia, J. Rodriguez ; Saito, T. ; Satalecka, K. ; Scapin, V. ; Schultz, C. ; Schweizer, T. ; Shore, S. N. ; Sillanpää, A. ; Sitarek, J. ; Snidaric, I. ; Sobczynska, D. ; Stamerra, A. ; Steinbring, T. ; Strzys, M. ; Takalo, L. ; Takami, H. ; Tavecchio, F. ; Temnikov, P. ; Terzić, T. ; Tescaro, D. ; Teshima, M. ; Thaele, J. ; Torres, D. F. ; Toyama, T. ; Treves, A. ; Verguilov, V. ; Vovk, I. ; Ward, J. E. ; Will, M. ; Wu, M. H. ; Zanin, R. ; Perkins, J. ; Verrecchia, F. ; Leto, C. ; Böttcher, M. ; Villata, M. ; Raiteri, C. M. ; Acosta-Pulido, J. A. ; Bachev, R. ; Berdyugin, A. ; Blinov, D. A. ; Carnerero, M. I. ; Chen, W. P. ; Chinchilla, P. ; Damljanovic, G. ; Eswaraiah, C. ; Grishina, T. S. ; Ibryamov, S. ; Jordan, B. ; Jorstad, S. G. ; Joshi, M. ; Kopatskaya, E. N. ; Kurtanidze, O. M. ; Kurtanidze, S. O. ; Larionova, E. G. ; Larionova, L. V. ; Larionov, V. M. ; Latev, G. ; Lin, H. C. ; Marscher, A. P. ; Mokrushina, A. A. ; Morozova, D. A. ; Nikolashvili, M. G. ; Semkov, E. ; Smith, P. S. ; Strigachev, A. ; Troitskaya, Yu V. ; Troitsky, I. S. ; Vince, O. ; Barnes, J. ; Güver, T. ; Moody, J. W. ; Sadun, A. C. ; Sun, S. ; Hovatta, T. ; Richards, J. L. ; Max-Moerbeck, W. ; Readhead, A. C.R. ; Lähteenmäki, A. ; Tornikoski, M. ; Tammi, J. ; Ramakrishnan, V. ; Reinthal, R. ; Angelakis, E. ; Fuhrmann, L. ; Myserlis, I. ; Karamanavis, V. ; Sievers, A. ; Ungerechts, H. ; Zensus, J. A. / MULTIWAVELENGTH STUDY OF QUIESCENT STATES OF MRK 421 WITH UNPRECEDENTED HARD X-RAY COVERAGE PROVIDED BY NuSTAR IN 2013. In: Astrophysical Journal. 2016 ; Vol. 819, No. 2.
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title = "MULTIWAVELENGTH STUDY OF QUIESCENT STATES OF MRK 421 WITH UNPRECEDENTED HARD X-RAY COVERAGE PROVIDED BY NuSTAR IN 2013",
abstract = "We 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) γ-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 Γ ≈ 3 power law, with no evidence for an exponential cutoff or additional hard components up 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.",
author = "M. Baloković and D. Paneque and G. Madejski and A. Furniss and J. Chiang and M. Ajello and Alexander, {D. M.} and D. Barret and Blandford, {R. D.} and Boggs, {S. E.} and Christensen, {F. E.} and Craig, {W. W.} and K. Forster and P. Giommi and B. Grefenstette and C. Hailey and Harrison, {F. A.} and A. Hornstrup and T. Kitaguchi and Koglin, {J. E.} and Madsen, {K. K.} and Mao, {P. H.} and H. Miyasaka and K. Mori and M. Perri and Pivovaroff, {M. J.} and S. Puccetti and V. Rana and D. Stern and G. Tagliaferri and Urry, {C. M.} and Westergaard, {N. J.} and Zhang, {W. W.} and A. Zoglauer and S. Archambault and A. Archer and A. Barnacka and W. Benbow and R. Bird and Buckley, {J. H.} and V. Bugaev and M. Cerruti and X. Chen and L. Ciupik and Connolly, {M. P.} and W. Cui and Dickinson, {H. J.} and J. Dumm and Eisch, {J. D.} and Falcone, {Abraham David} and Q. Feng and Finley, {J. P.} and H. Fleischhack and L. Fortson and S. Griffin and Griffiths, {S. T.} and J. Grube and G. Gyuk and M. Huetten and N. H{\aa}kansson and J. Holder and Humensky, {T. B.} and Johnson, {C. A.} and P. Kaaret and M. Kertzman and Y. Khassen and D. Kieda and M. Krause and F. Krennrich and Lang, {M. J.} and G. Maier and S. McArthur and K. Meagher and P. Moriarty and T. Nelson and D. Nieto and Ong, {R. A.} and N. Park and M. Pohl and A. Popkow and E. Pueschel and Reynolds, {P. T.} and Richards, {G. T.} and E. Roache and M. Santander and Sembroski, {G. H.} and K. Shahinyan and Smith, {A. W.} and D. Staszak and I. Telezhinsky and Todd, {N. W.} and Tucci, {J. V.} and J. Tyler and S. Vincent and A. Weinstein and A. Wilhelm and Williams, {D. A.} and B. Zitzer and Ahnen, {M. L.} and S. Ansoldi and Antonelli, {L. A.} and P. Antoranz and A. Babic and B. Banerjee and P. Bangale and {De Almeida}, {U. Barres} and Barrio, {J. A.} and Gonz{\'a}lez, {J. Becerra} and W. Bednarek and E. Bernardini and B. Biasuzzi and A. Biland and O. Blanch and S. Bonnefoy and G. Bonnoli and F. Borracci and T. Bretz and E. Carmona and A. Carosi and A. Chatterjee and R. Clavero and P. Colin and E. Colombo and Contreras, {J. L.} and J. Cortina and S. Covino and {Da Vela}, P. and F. Dazzi and {De Angelis}, A. and {De Lotto}, B. and {De Ońa Wilhelmi}, E. and Mendez, {C. Delgado} and {Di Pierro}, F. and Prester, {D. Dominis} and D. Dorner and M. Doro and S. Einecke and D. Elsaesser and A. Fern{\'a}ndez-Barral and D. Fidalgo and Fonseca, {M. V.} and L. Font and K. Frantzen and C. Fruck and D. Galindo and L{\'o}pez, {R. J.Garc{\'i}a} and M. Garczarczyk and Terrats, {D. Garrido} and M. Gaug and P. Giammaria and D. Glawion and N. Godinović and {Gonz{\'a}lez Mu{\~n}oz}, A. and D. Guberman and A. Hahn and Y. Hanabata and M. Hayashida and J. Herrera and J. Hose and D. Hrupec and G. Hughes and W. Idec and K. Kodani and Y. Konno and H. Kubo and J. Kushida and {La Barbera}, A. and D. Lelas and E. Lindfors and S. Lombardi and F. Longo and M. L{\'o}pez and R. L{\'o}pez-Coto and A. L{\'o}pez-Oramas and E. Lorenz and P. Majumdar and M. Makariev and K. Mallot and G. Maneva and M. Manganaro and K. Mannheim and L. Maraschi and B. Marcote and M. Mariotti and M. Mart{\'i}nez and D. Mazin and U. Menzel and Miranda, {J. M.} and R. Mirzoyan and A. Moralejo and E. Moretti and D. Nakajima and V. Neustroev and A. Niedzwiecki and Rosillo, {M. Nievas} and K. Nilsson and K. Nishijima and K. Noda and R. Orito and A. Overkemping and S. Paiano and J. Palacio and M. Palatiello and R. Paoletti and Paredes, {J. M.} and X. Paredes-Fortuny and M. Persic and J. Poutanen and Moroni, {P. G.Prada} and E. Prandini and I. Puljak and W. Rhode and M. Rib{\'o} and J. Rico and Garcia, {J. Rodriguez} and T. Saito and K. Satalecka and V. Scapin and C. Schultz and T. Schweizer and Shore, {S. N.} and A. Sillanp{\"a}{\"a} and J. Sitarek and I. Snidaric and D. Sobczynska and A. Stamerra and T. Steinbring and M. Strzys and L. Takalo and H. Takami and F. Tavecchio and P. Temnikov and T. Terzić and D. Tescaro and M. Teshima and J. Thaele and Torres, {D. F.} and T. Toyama and A. Treves and V. Verguilov and I. Vovk and Ward, {J. E.} and M. Will and Wu, {M. H.} and R. Zanin and J. Perkins and F. Verrecchia and C. Leto and M. B{\"o}ttcher and M. Villata and Raiteri, {C. M.} and Acosta-Pulido, {J. A.} and R. Bachev and A. Berdyugin and Blinov, {D. A.} and Carnerero, {M. I.} and Chen, {W. P.} and P. Chinchilla and G. Damljanovic and C. Eswaraiah and Grishina, {T. S.} and S. Ibryamov and B. Jordan and Jorstad, {S. G.} and M. Joshi and Kopatskaya, {E. N.} and Kurtanidze, {O. M.} and Kurtanidze, {S. O.} and Larionova, {E. G.} and Larionova, {L. V.} and Larionov, {V. M.} and G. Latev and Lin, {H. C.} and Marscher, {A. P.} and Mokrushina, {A. A.} and Morozova, {D. A.} and Nikolashvili, {M. G.} and E. Semkov and Smith, {P. S.} and A. Strigachev and Troitskaya, {Yu V.} and Troitsky, {I. S.} and O. Vince and J. Barnes and T. G{\"u}ver and Moody, {J. W.} and Sadun, {A. C.} and S. Sun and T. Hovatta and Richards, {J. L.} and W. Max-Moerbeck and Readhead, {A. C.R.} and A. L{\"a}hteenm{\"a}ki and M. Tornikoski and J. Tammi and V. Ramakrishnan and R. Reinthal and E. Angelakis and L. Fuhrmann and I. Myserlis and V. Karamanavis and A. Sievers and H. Ungerechts and Zensus, {J. A.}",
year = "2016",
month = "3",
day = "10",
doi = "10.3847/0004-637X/819/2/156",
language = "English (US)",
volume = "819",
journal = "Astrophysical Journal",
issn = "0004-637X",
publisher = "IOP Publishing Ltd.",
number = "2",

}

Baloković, M, Paneque, D, Madejski, G, Furniss, A, Chiang, J, Ajello, 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, Westergaard, NJ, 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, AD, Feng, Q, Finley, JP, Fleischhack, H, Fortson, L, Griffin, S, Griffiths, ST, Grube, J, Gyuk, G, Huetten, M, Håkansson, N, Holder, J, Humensky, TB, Johnson, CA, Kaaret, P, Kertzman, M, Khassen, Y, Kieda, D, Krause, M, Krennrich, F, Lang, MJ, Maier, G, McArthur, S, Meagher, K, Moriarty, P, Nelson, T, Nieto, D, Ong, RA, Park, N, Pohl, M, Popkow, A, Pueschel, E, Reynolds, PT, Richards, GT, Roache, E, Santander, M, Sembroski, GH, Shahinyan, K, Smith, AW, Staszak, D, Telezhinsky, I, Todd, NW, Tucci, JV, Tyler, J, Vincent, S, Weinstein, A, Wilhelm, A, Williams, DA, Zitzer, B, Ahnen, ML, Ansoldi, S, Antonelli, LA, Antoranz, P, Babic, A, Banerjee, B, Bangale, P, De Almeida, UB, Barrio, JA, González, JB, Bednarek, W, Bernardini, E, Biasuzzi, B, Biland, A, Blanch, O, Bonnefoy, S, Bonnoli, G, Borracci, F, Bretz, T, Carmona, E, Carosi, A, Chatterjee, A, Clavero, R, Colin, P, Colombo, E, Contreras, JL, Cortina, J, Covino, S, Da Vela, P, Dazzi, F, De Angelis, A, De Lotto, B, De Ońa Wilhelmi, E, Mendez, CD, Di Pierro, F, Prester, DD, Dorner, D, Doro, M, Einecke, S, Elsaesser, D, Fernández-Barral, A, Fidalgo, D, Fonseca, MV, Font, L, Frantzen, K, Fruck, C, Galindo, D, López, RJG, Garczarczyk, M, Terrats, DG, Gaug, M, Giammaria, P, Glawion, D, Godinović, N, González Muñoz, A, Guberman, D, Hahn, A, Hanabata, Y, Hayashida, M, Herrera, J, Hose, J, Hrupec, D, Hughes, G, Idec, W, Kodani, K, Konno, Y, Kubo, H, Kushida, J, La Barbera, A, Lelas, D, Lindfors, E, Lombardi, S, Longo, F, López, M, López-Coto, R, López-Oramas, A, Lorenz, E, Majumdar, P, Makariev, M, Mallot, K, Maneva, G, Manganaro, M, Mannheim, K, Maraschi, L, Marcote, B, Mariotti, M, Martínez, M, Mazin, D, Menzel, U, Miranda, JM, Mirzoyan, R, Moralejo, A, Moretti, E, Nakajima, D, Neustroev, V, Niedzwiecki, A, Rosillo, MN, Nilsson, K, Nishijima, K, Noda, K, Orito, R, Overkemping, A, Paiano, S, Palacio, J, Palatiello, M, Paoletti, R, Paredes, JM, Paredes-Fortuny, X, Persic, M, Poutanen, J, Moroni, PGP, Prandini, E, Puljak, I, Rhode, W, Ribó, M, Rico, J, Garcia, JR, Saito, T, Satalecka, K, Scapin, V, Schultz, C, Schweizer, T, Shore, SN, Sillanpää, A, Sitarek, J, Snidaric, I, Sobczynska, D, Stamerra, A, Steinbring, T, Strzys, M, Takalo, L, Takami, H, Tavecchio, F, Temnikov, P, Terzić, T, Tescaro, D, Teshima, M, Thaele, J, Torres, DF, Toyama, T, Treves, A, Verguilov, V, Vovk, I, Ward, JE, Will, M, Wu, MH, Zanin, R, Perkins, J, Verrecchia, F, Leto, C, Böttcher, M, Villata, M, Raiteri, CM, Acosta-Pulido, JA, Bachev, R, Berdyugin, A, Blinov, DA, Carnerero, MI, Chen, WP, Chinchilla, P, Damljanovic, G, Eswaraiah, C, Grishina, TS, Ibryamov, S, Jordan, B, Jorstad, SG, Joshi, M, Kopatskaya, EN, Kurtanidze, OM, Kurtanidze, SO, Larionova, EG, Larionova, LV, Larionov, VM, Latev, G, Lin, HC, Marscher, AP, Mokrushina, AA, Morozova, DA, Nikolashvili, MG, Semkov, E, Smith, PS, Strigachev, A, Troitskaya, YV, Troitsky, IS, Vince, O, Barnes, J, Güver, T, Moody, JW, Sadun, AC, Sun, S, Hovatta, T, Richards, JL, Max-Moerbeck, W, Readhead, ACR, Lähteenmäki, A, Tornikoski, M, Tammi, J, Ramakrishnan, V, Reinthal, R, Angelakis, E, Fuhrmann, L, Myserlis, I, Karamanavis, V, Sievers, A, Ungerechts, H & Zensus, JA 2016, 'MULTIWAVELENGTH STUDY OF QUIESCENT STATES OF MRK 421 WITH UNPRECEDENTED HARD X-RAY COVERAGE PROVIDED BY NuSTAR IN 2013', Astrophysical Journal, vol. 819, no. 2, 156. https://doi.org/10.3847/0004-637X/819/2/156

MULTIWAVELENGTH STUDY OF QUIESCENT STATES OF MRK 421 WITH UNPRECEDENTED HARD X-RAY COVERAGE PROVIDED BY NuSTAR IN 2013. / Baloković, M.; Paneque, D.; Madejski, G.; Furniss, A.; Chiang, J.; Ajello, M.; Alexander, D. M.; Barret, D.; Blandford, R. D.; Boggs, S. E.; Christensen, F. E.; Craig, W. W.; Forster, K.; Giommi, P.; Grefenstette, B.; Hailey, C.; Harrison, F. A.; Hornstrup, A.; Kitaguchi, T.; Koglin, J. E.; Madsen, K. K.; Mao, P. H.; Miyasaka, H.; Mori, K.; Perri, M.; Pivovaroff, M. J.; Puccetti, S.; Rana, V.; Stern, D.; Tagliaferri, G.; Urry, C. M.; Westergaard, N. J.; Zhang, W. W.; Zoglauer, A.; Archambault, S.; Archer, A.; Barnacka, A.; Benbow, W.; Bird, R.; Buckley, J. H.; Bugaev, V.; Cerruti, M.; Chen, X.; Ciupik, L.; Connolly, M. P.; Cui, W.; Dickinson, H. J.; Dumm, J.; Eisch, J. D.; Falcone, Abraham David; Feng, Q.; Finley, J. P.; Fleischhack, H.; Fortson, L.; Griffin, S.; Griffiths, S. T.; Grube, J.; Gyuk, G.; Huetten, M.; Håkansson, N.; Holder, J.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kertzman, M.; Khassen, Y.; Kieda, D.; Krause, M.; Krennrich, F.; Lang, M. J.; Maier, G.; McArthur, S.; Meagher, K.; Moriarty, P.; Nelson, T.; Nieto, D.; Ong, R. A.; Park, N.; Pohl, M.; Popkow, A.; Pueschel, E.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Todd, N. W.; Tucci, J. V.; Tyler, J.; Vincent, S.; Weinstein, A.; Wilhelm, A.; Williams, D. A.; Zitzer, B.; Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Banerjee, B.; Bangale, P.; De Almeida, U. Barres; Barrio, J. A.; González, J. Becerra; Bednarek, W.; Bernardini, E.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Chatterjee, A.; Clavero, R.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Lotto, B.; De Ońa Wilhelmi, E.; Mendez, C. Delgado; Di Pierro, F.; Prester, D. Dominis; Dorner, D.; Doro, M.; Einecke, S.; Elsaesser, D.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; Galindo, D.; López, R. J.García; Garczarczyk, M.; Terrats, D. Garrido; Gaug, M.; Giammaria, P.; Glawion, D.; Godinović, N.; González Muñoz, A.; Guberman, D.; Hahn, A.; Hanabata, Y.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Hughes, G.; Idec, W.; Kodani, K.; Konno, Y.; Kubo, H.; Kushida, J.; La Barbera, A.; Lelas, D.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Majumdar, P.; Makariev, M.; Mallot, K.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Moretti, E.; Nakajima, D.; Neustroev, V.; Niedzwiecki, A.; Rosillo, M. Nievas; Nilsson, K.; Nishijima, K.; Noda, K.; Orito, R.; Overkemping, A.; Paiano, S.; Palacio, J.; Palatiello, M.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Persic, M.; Poutanen, J.; Moroni, P. G.Prada; Prandini, E.; Puljak, I.; Rhode, W.; Ribó, M.; Rico, J.; Garcia, J. Rodriguez; Saito, T.; Satalecka, K.; Scapin, V.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Stamerra, A.; Steinbring, T.; Strzys, M.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Thaele, J.; Torres, D. F.; Toyama, T.; Treves, A.; Verguilov, V.; Vovk, I.; Ward, J. E.; Will, M.; Wu, M. H.; Zanin, R.; Perkins, J.; Verrecchia, F.; Leto, C.; Böttcher, M.; Villata, M.; Raiteri, C. M.; Acosta-Pulido, J. A.; Bachev, R.; Berdyugin, A.; Blinov, D. A.; Carnerero, M. I.; Chen, W. P.; Chinchilla, P.; Damljanovic, G.; Eswaraiah, C.; Grishina, T. S.; Ibryamov, S.; Jordan, B.; Jorstad, S. G.; Joshi, M.; Kopatskaya, E. N.; Kurtanidze, O. M.; Kurtanidze, S. O.; Larionova, E. G.; Larionova, L. V.; Larionov, V. M.; Latev, G.; Lin, H. C.; Marscher, A. P.; Mokrushina, A. A.; Morozova, D. A.; Nikolashvili, M. G.; Semkov, E.; Smith, P. S.; Strigachev, A.; Troitskaya, Yu V.; Troitsky, I. S.; Vince, O.; Barnes, J.; Güver, T.; Moody, J. W.; Sadun, A. C.; Sun, S.; Hovatta, T.; Richards, J. L.; Max-Moerbeck, W.; Readhead, A. C.R.; Lähteenmäki, A.; Tornikoski, M.; Tammi, J.; Ramakrishnan, V.; Reinthal, R.; Angelakis, E.; Fuhrmann, L.; Myserlis, I.; Karamanavis, V.; Sievers, A.; Ungerechts, H.; Zensus, J. A.

In: Astrophysical Journal, Vol. 819, No. 2, 156, 10.03.2016.

Research output: Contribution to journalArticle

TY - JOUR

T1 - MULTIWAVELENGTH STUDY OF QUIESCENT STATES OF MRK 421 WITH UNPRECEDENTED HARD X-RAY COVERAGE PROVIDED BY NuSTAR IN 2013

AU - Baloković, M.

AU - Paneque, D.

AU - Madejski, G.

AU - Furniss, A.

AU - Chiang, J.

AU - Ajello, M.

AU - Alexander, D. M.

AU - Barret, D.

AU - Blandford, R. D.

AU - Boggs, S. E.

AU - Christensen, F. E.

AU - Craig, W. W.

AU - Forster, K.

AU - Giommi, P.

AU - Grefenstette, B.

AU - Hailey, C.

AU - Harrison, F. A.

AU - Hornstrup, A.

AU - Kitaguchi, T.

AU - Koglin, J. E.

AU - Madsen, K. K.

AU - Mao, P. H.

AU - Miyasaka, H.

AU - Mori, K.

AU - Perri, M.

AU - Pivovaroff, M. J.

AU - Puccetti, S.

AU - Rana, V.

AU - Stern, D.

AU - Tagliaferri, G.

AU - Urry, C. M.

AU - Westergaard, N. J.

AU - Zhang, W. W.

AU - Zoglauer, A.

AU - Archambault, S.

AU - Archer, A.

AU - Barnacka, A.

AU - Benbow, W.

AU - Bird, R.

AU - Buckley, J. H.

AU - Bugaev, V.

AU - Cerruti, M.

AU - Chen, X.

AU - Ciupik, L.

AU - Connolly, M. P.

AU - Cui, W.

AU - Dickinson, H. J.

AU - Dumm, J.

AU - Eisch, J. D.

AU - Falcone, Abraham David

AU - Feng, Q.

AU - Finley, J. P.

AU - Fleischhack, H.

AU - Fortson, L.

AU - Griffin, S.

AU - Griffiths, S. T.

AU - Grube, J.

AU - Gyuk, G.

AU - Huetten, M.

AU - Håkansson, N.

AU - Holder, J.

AU - Humensky, T. B.

AU - Johnson, C. A.

AU - Kaaret, P.

AU - Kertzman, M.

AU - Khassen, Y.

AU - Kieda, D.

AU - Krause, M.

AU - Krennrich, F.

AU - Lang, M. J.

AU - Maier, G.

AU - McArthur, S.

AU - Meagher, K.

AU - Moriarty, P.

AU - Nelson, T.

AU - Nieto, D.

AU - Ong, R. A.

AU - Park, N.

AU - Pohl, M.

AU - Popkow, A.

AU - Pueschel, E.

AU - Reynolds, P. T.

AU - Richards, G. T.

AU - Roache, E.

AU - Santander, M.

AU - Sembroski, G. H.

AU - Shahinyan, K.

AU - Smith, A. W.

AU - Staszak, D.

AU - Telezhinsky, I.

AU - Todd, N. W.

AU - Tucci, J. V.

AU - Tyler, J.

AU - Vincent, S.

AU - Weinstein, A.

AU - Wilhelm, A.

AU - Williams, D. A.

AU - Zitzer, B.

AU - Ahnen, M. L.

AU - Ansoldi, S.

AU - Antonelli, L. A.

AU - Antoranz, P.

AU - Babic, A.

AU - Banerjee, B.

AU - Bangale, P.

AU - De Almeida, U. Barres

AU - Barrio, J. A.

AU - González, J. Becerra

AU - Bednarek, W.

AU - Bernardini, E.

AU - Biasuzzi, B.

AU - Biland, A.

AU - Blanch, O.

AU - Bonnefoy, S.

AU - Bonnoli, G.

AU - Borracci, F.

AU - Bretz, T.

AU - Carmona, E.

AU - Carosi, A.

AU - Chatterjee, A.

AU - Clavero, R.

AU - Colin, P.

AU - Colombo, E.

AU - Contreras, J. L.

AU - Cortina, J.

AU - Covino, S.

AU - Da Vela, P.

AU - Dazzi, F.

AU - De Angelis, A.

AU - De Lotto, B.

AU - De Ońa Wilhelmi, E.

AU - Mendez, C. Delgado

AU - Di Pierro, F.

AU - Prester, D. Dominis

AU - Dorner, D.

AU - Doro, M.

AU - Einecke, S.

AU - Elsaesser, D.

AU - Fernández-Barral, A.

AU - Fidalgo, D.

AU - Fonseca, M. V.

AU - Font, L.

AU - Frantzen, K.

AU - Fruck, C.

AU - Galindo, D.

AU - López, R. J.García

AU - Garczarczyk, M.

AU - Terrats, D. Garrido

AU - Gaug, M.

AU - Giammaria, P.

AU - Glawion, D.

AU - Godinović, N.

AU - González Muñoz, A.

AU - Guberman, D.

AU - Hahn, A.

AU - Hanabata, Y.

AU - Hayashida, M.

AU - Herrera, J.

AU - Hose, J.

AU - Hrupec, D.

AU - Hughes, G.

AU - Idec, W.

AU - Kodani, K.

AU - Konno, Y.

AU - Kubo, H.

AU - Kushida, J.

AU - La Barbera, A.

AU - Lelas, D.

AU - Lindfors, E.

AU - Lombardi, S.

AU - Longo, F.

AU - López, M.

AU - López-Coto, R.

AU - López-Oramas, A.

AU - Lorenz, E.

AU - Majumdar, P.

AU - Makariev, M.

AU - Mallot, K.

AU - Maneva, G.

AU - Manganaro, M.

AU - Mannheim, K.

AU - Maraschi, L.

AU - Marcote, B.

AU - Mariotti, M.

AU - Martínez, M.

AU - Mazin, D.

AU - Menzel, U.

AU - Miranda, J. M.

AU - Mirzoyan, R.

AU - Moralejo, A.

AU - Moretti, E.

AU - Nakajima, D.

AU - Neustroev, V.

AU - Niedzwiecki, A.

AU - Rosillo, M. Nievas

AU - Nilsson, K.

AU - Nishijima, K.

AU - Noda, K.

AU - Orito, R.

AU - Overkemping, A.

AU - Paiano, S.

AU - Palacio, J.

AU - Palatiello, M.

AU - Paoletti, R.

AU - Paredes, J. M.

AU - Paredes-Fortuny, X.

AU - Persic, M.

AU - Poutanen, J.

AU - Moroni, P. G.Prada

AU - Prandini, E.

AU - Puljak, I.

AU - Rhode, W.

AU - Ribó, M.

AU - Rico, J.

AU - Garcia, J. Rodriguez

AU - Saito, T.

AU - Satalecka, K.

AU - Scapin, V.

AU - Schultz, C.

AU - Schweizer, T.

AU - Shore, S. N.

AU - Sillanpää, A.

AU - Sitarek, J.

AU - Snidaric, I.

AU - Sobczynska, D.

AU - Stamerra, A.

AU - Steinbring, T.

AU - Strzys, M.

AU - Takalo, L.

AU - Takami, H.

AU - Tavecchio, F.

AU - Temnikov, P.

AU - Terzić, T.

AU - Tescaro, D.

AU - Teshima, M.

AU - Thaele, J.

AU - Torres, D. F.

AU - Toyama, T.

AU - Treves, A.

AU - Verguilov, V.

AU - Vovk, I.

AU - Ward, J. E.

AU - Will, M.

AU - Wu, M. H.

AU - Zanin, R.

AU - Perkins, J.

AU - Verrecchia, F.

AU - Leto, C.

AU - Böttcher, M.

AU - Villata, M.

AU - Raiteri, C. M.

AU - Acosta-Pulido, J. A.

AU - Bachev, R.

AU - Berdyugin, A.

AU - Blinov, D. A.

AU - Carnerero, M. I.

AU - Chen, W. P.

AU - Chinchilla, P.

AU - Damljanovic, G.

AU - Eswaraiah, C.

AU - Grishina, T. S.

AU - Ibryamov, S.

AU - Jordan, B.

AU - Jorstad, S. G.

AU - Joshi, M.

AU - Kopatskaya, E. N.

AU - Kurtanidze, O. M.

AU - Kurtanidze, S. O.

AU - Larionova, E. G.

AU - Larionova, L. V.

AU - Larionov, V. M.

AU - Latev, G.

AU - Lin, H. C.

AU - Marscher, A. P.

AU - Mokrushina, A. A.

AU - Morozova, D. A.

AU - Nikolashvili, M. G.

AU - Semkov, E.

AU - Smith, P. S.

AU - Strigachev, A.

AU - Troitskaya, Yu V.

AU - Troitsky, I. S.

AU - Vince, O.

AU - Barnes, J.

AU - Güver, T.

AU - Moody, J. W.

AU - Sadun, A. C.

AU - Sun, S.

AU - Hovatta, T.

AU - Richards, J. L.

AU - Max-Moerbeck, W.

AU - Readhead, A. C.R.

AU - Lähteenmäki, A.

AU - Tornikoski, M.

AU - Tammi, J.

AU - Ramakrishnan, V.

AU - Reinthal, R.

AU - Angelakis, E.

AU - Fuhrmann, L.

AU - Myserlis, I.

AU - Karamanavis, V.

AU - Sievers, A.

AU - Ungerechts, H.

AU - Zensus, J. A.

PY - 2016/3/10

Y1 - 2016/3/10

N2 - We 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) γ-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 Γ ≈ 3 power law, with no evidence for an exponential cutoff or additional hard components up 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.

AB - We 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) γ-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 Γ ≈ 3 power law, with no evidence for an exponential cutoff or additional hard components up 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.

UR - http://www.scopus.com/inward/record.url?scp=84961655196&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84961655196&partnerID=8YFLogxK

U2 - 10.3847/0004-637X/819/2/156

DO - 10.3847/0004-637X/819/2/156

M3 - Article

VL - 819

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 2

M1 - 156

ER -