First Results from<i>NuSTAR</i>Observations of Mkn 421

Baloković, Mislav; Ajello, M.; Blandford, R. D.; Boggs, Steven E.; Borracci, F.; Chiang, J.; Christensen, Finn Erland; Craig, William W.; Furniss, A.; Ghisellini, G.; Giebels, B.; Giommi, P.; Grefenstette, Brian W.; Hailey, Charles J.; Harrison, Fiona A.; Hayashida, M.; Humensky, Brian; Inoue, Yoshiyuki; Koglin, Jason E.; Krawczynski, H.; Madejski, G. M.; Madsen, K. K.; Meier, David L.; Nelson, Thomas; Ogle, Patrick; Paneque, D.; Perri, M.; Puccetti, S.; Reynolds, Christopher S.; Sbarrato, T.; Stern, Daniel; Tagliaferri, G.; Urry, C. Megan; Wehrle, A. E.; Zhang, W. W.

doi:10.1051/epjconf/20136104013

Cited by 8 publications

(18 citation statements)

References 10 publications

(19 reference statements)

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“…This agrees with the previous results obtained by many authors (e.g. Abdo et al 2014;Baloković et al 2013;Bartoli et al 2011;Blazejowski et al 2005;Fossati et al 2008;Gaur et al 2012;Lico et al 2014;Richards et al 2013;Smith et al 2008;Ushio et al 2010), who found that there are clear correlations among different energy regimes, and the lower frequencies variations lag behind the higher frequencies variability.…”

Section: Correlation Analysissupporting

confidence: 93%

“…Gaur et al 2012;Baloković et al 2013;Abdo et al 2014;Fossati et al 2008;Smith et al 2008;Ushio et al 2010;Bartoli et al 2011;Blazejowski et al 2005;Richards et al 2013). The correlation between the radio, Xray and γ-ray band can be best interpreted by the leptonic models (Giommi et al 1999;Tagliaferri et al 2003).…”

Section: Discussionmentioning

confidence: 99%

“…The correlation analysis of X-ray and γ-ray variability suggests that there is a significant correlation between them (Baloković et al 2013;Acciari et al 2014Acciari et al , 2011Abdo et al 2014;Fossati et al 2008;Horan et al 2009;Smith et al 2008;Ushio et al 2010;Bartoli et al 2011;Blazejowski et al 2005). Gaur et al (2012) investigated the correlation between the optical and X-ray bands, and found that the optical variability lags behind the X-ray variability for 9.5±2 days.…”

Section: Introductionmentioning

confidence: 99%

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Multiband Variability Analysis of Mrk 421

Li¹,

Jiang²,

Guo³

et al. 2016

PASP

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We have assembled the historical variability data of Mrk 421 at radio 15 GHz, X-ray and γ-ray bands, spanning about 6.3, 10.3 and 7.5 yr, respectively. We analyzed the variability by using three methods. The results indicated that there is a period of 287.6 ± 4.4 days for 15 GHz, 309.5 ± 5.8 days for X-ray and 283.4 ± 4.7 days for γ-ray, respectively. This period can be reasonably explained by the nonballistic helical motion of the emitting material. The correlation analysis suggested that the variabilities of radio 15 GHz, X-ray and γ-ray are remarkable correlated, and the emission of radio 15 GHz lags behind that of X-ray, and the X-ray flux lags behind the γ-ray. This suggests that the γ-ray derives from inverse Compton (IC) scattering of the synchrotron photons, supporting the synchrotron self-Compton (SSC) model. Moreover, the time delay between different wavebands could be explained by the shock-in-jet models, in which a moving emission region produces the radio to γ-ray activity, implying that the emission region of γ-ray is closer to the center than ones of X-ray and radio emission.

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Section: Correlation Analysissupporting

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Multiband Variability Analysis of Mrk 421

Li¹,

Jiang²,

Guo³

et al. 2016

PASP

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“…The Fermi-LAT light curve reveals elevated flux with respect to the median, as do the optical and UV data when compared to historical values. Modest soft X-ray flux is apparent from Swift-XRT data in comparison with the long-baseline median (Baloković et al 2013a;Stroh & Falcone 2013) and the intense flaring episodes covered in the literature (e.g., Acciari et al 2009;Tramacere et al 2009;Aleksić et al 2012). Count rates of 10  s −1 in the 0.3-10keV band are up to a factor of 2  Table 8.…”

Section: Multiwavelength Variabilitymentioning

confidence: 82%

“…We first model the NuSTAR spectra for each observation separately, before examining the clear intra-observation spectral variability in Section 3.3 (see Figures 2 and 3, and Baloković et al 2013a). All observation-averaged spectra are shown in Figure 4.…”

Section: Observation-averaged Spectroscopymentioning

confidence: 99%

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

Baloković¹,

Paneque²,

Madejski³

et al. 2016

ApJ

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111

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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 3 G » 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.

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Underlying particle spectrum of Mkn 421 during the huge X-ray flare in April 2013

Sinha

Shukla

Misra

et al. 2015

A&A

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Context. In April 2013, the nearby TeV blazar, Mkn 421, showed one of the largest flares in X-rays in the past decade. Aims. We study all multiwavelength data available during MJD 56 392 to 56 403, with special emphasis on X-ray data to understand the underlying particle energy distribution. Methods. We studied the correlations between the UV and gamma-ray bands with the X-ray band using the z-transformed discrete correlation function. We modelled the underlying particle energy spectrum with a single population of electrons emitting synchrotron radiation, and statistically fitted the simultaneous time-resolved data from Swift-XRT and NuSTAR. Results. The flux varied rapidly in the X-ray band, with a minimum doubling timescale of 1.69 ± 0.13 h. There were no corresponding flares in UV and gamma-ray bands. The variability in UV and gamma rays was relatively modest with ∼8% and ∼16%, respectively, and no significant correlation was found with the X-ray light curve. The observed X-ray spectrum shows a clear curvature that can be fit by a log parabolic spectral form. This is best explained as originating from a log parabolic electron spectrum. However, a broken power law or a power law with an exponentially falling electron distribution cannot be ruled out either. Moreover, the excellent broadband spectrum from 0.3-79 keV allows us to make predictions of the UV flux. We find that this prediction is compatible with the observed flux during the low state in X-rays. However, during the X-ray flares, depending on the adopted model, the predicted flux is a factor of 2-50 lower than the observed one. This suggests that the X-ray flares are probably caused by a separate population that does not contribute significantly to the radiation at lower energies. Alternatively, the underlying particle spectrum can be much more complex than those explored in this work.

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First Results fromNuSTARObservations of Mkn 421

Cited by 8 publications

References 10 publications

Multiband Variability Analysis of Mrk 421

Multiband Variability Analysis of Mrk 421

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

Underlying particle spectrum of Mkn 421 during the huge X-ray flare in April 2013

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