J/ApJS/275/23ivo://CDS.VizieR/J/ApJS/275/23CDSKapanadze B.Gurchumelia A.Aller M.2025-11-03T14:52:33Z2025-11-03T14:51:22ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frbl-lacertae-objectsx-ray-sourcesultraviolet-photometryvisible-astronomygamma-ray-astronomyradio-sourcesWe present the spectral and timing results obtained during the intense observations of Mrk 421 by the Swift-based ultraviolet to X-ray instruments during 2018 April-2023 December. The source showed various strengths of X-ray flaring activity, exceeding a level of 3.5x10^-9^erg/cm^2^/s during the strongest 0.3-10keV flares. Our study identifies a number of intraday brightness variability, including 61 instances that occurred within 1ks exposures that are consistent with the shock-in-jet scenario and accompanied by significant, fast spectral changes. The source exhibited extreme spectral properties with dominance of the log-parabolic distributions of photons with energy and the frequent occurrence of hard photon indices in the 0.3-10keV and 0.3-300GeV bands, with the peak of synchrotron spectral energy distribution Ep detected at the energies beyond 29keV for the first time. The source showed very fast transitions of log-parabolic-to-power-law spectra, most plausibly caused by turbulence-driven relativistic magnetic reconnection. Our spectral results also demonstrate the importance of the first-order Fermi mechanism within the magnetic field of different confinement efficiencies, stochastic acceleration, transitions in the turbulence spectrum, and hadronic cascades. The X-ray, UV, and {gamma}-ray fluxes showed a lognormal variability, which hints at the imprint of accretion disk instabilities on the blazar jet, as well as the possible presence of hadronic cascades. The UV and {gamma}-ray variabilities demonstrated weak correlations with the X-ray flaring activity, which is not consistent with simple synchrotron self-Compton models and requires more complex particle acceleration and emission scenarios.2024ApJS..275...23Khttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJS/275/23CatalogResearchIsServedByTAP VizieR generic servicerelated-toB/swift : Swift Master Catalog (HEASARC, 2004-)J/ApJ/700/597 : FERMI LAT detected blazars (Abdo+, 2009)J/ApJ/716/30 : SED of Fermi bright blazars (Abdo+, 2010)J/ApJS/209/14 : The Swift/BAT hard X-ray transient monitor (Krimm+, 2013)J/other/Nat/515.376 : Power of relativistic jets in blazars (Ghisellini+, 2014)J/A+A/578/A22 : Mrk421 in March 2010 (Aleksic+, 2015)J/A+A/593/A91 : Mrk 421 multi-wavelength var., 2007-2009 (Ahnen+, 2016)J/ApJ/831/102 : Swift & NuSTAR obs. of Mrk421 (Kapanadze+, 2016)J/ApJ/848/103 : ~1.5yr Swift observations of Mrk 421 (Kapanadze+, 2017)J/ApJ/854/66 : Swift obs. of Mrk 421. I. 2005-2008 (Kapanadze+, 2018)J/ApJ/858/68 : Swift obs. of Mrk 421. II. (Kapanadze+, 2018)J/ApJS/238/13 : Sp. and timing results of 1ES 1959+650 (Kapanadze+, 2018)J/ApJS/247/33 : Fermi LAT fourth source catalog (4FGL) (Abdollahi+, 2020)J/ApJS/247/27 : Swift obs. of Mrk 421. III. 2.5yrs (Kapanadze+, 2020)J/A+A/655/A89 : Mrk421 multi-instrument obs. in 2017 (Acciari+, 2021)J/A+A/668/A75 : Long-term MWL var. of 1ES 0033+595 (Kapanadze+, 2022)J/ApJS/260/12 : Jet kinematics of blazars at 43GHz (Weaver+, 2022)J/ApJS/268/20 : XRT/UVOT obs. of Mrk501 (Kapanadze+, 2023)http://www.bu.edu/blazars/BEAM-ME.html : VLBA-BU Blazar Monitoring Programhttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJS/275/23https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJS/275/23http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJS/275/23https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJS/275/23https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJS/275/23http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJS/275/23GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tap6.6219879114527e-19 1.2058628298368645e-18Gamma-rayX-rayUVOpticalRadiodefaultJ/ApJS/275/23/table1Summary of XRT observations of Mrk 421 in 2018recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObsID[10474007/97201004] Swift observation identifiermeta.id;obs.param;obsintStartObservation start data/time UTCstime.start;obsnullableEndObservation end data/time UTCstime.end;obsnullableMJD[58219/60319.1] Modified Julian Datedtime.epochdoubleExp[139/3884] Exposure timedtime.duration;obs.exposureintCRate[5.38/108] Mean 0.3-10keV count ratect/sphot.count;em.X-rayfloate_CRate[0.07/0.5] Uncertainty in CRatect/sstat.error;phot.count;em.X-rayfloatchi2[0.08/199.5] Reduced {chi}^2^ valuestat.fit.chi2floatDoF[1/46] Degrees of Freedomstat.fit.dofintBinTime bin used for light curve construction; Or stands for Orbitstime.intervalcharVarExistence of brightness variability code (1)meta.code;src.varcharJ/ApJS/275/23/table2Results from UVOT observations in the bands UVW1-UVM2recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObsID[10474007/97201004] Swift observation identifiermeta.id;obs.param;obsintUVW1mag[11.2/13.1]? Swift/UVOT UVW1 band apparent magnitudemagphot.mag;em.UV.200-300nmfloatnullablee_UVW1mag[0.03/0.04]? Uncertainty in UVW1magmagstat.error;phot.mag;em.UV.200-300nmfloatnullableUVW1Flux[5.6/30.2]? Swift/UVOT UVW1 band flux densitymJyphot.flux;em.UV.200-300nmfloatnullablee_UVW1Flux[0.17/1.2]? Uncertainty in UVW1FluxmJystat.error;phot.flux;em.UV.200-300nmfloatnullablelogUVW1nfn[-10.21/-9.47]? Log Swift/UVOT UVW1 band {nu}F_{nu}_; erg/s/cm^2^log(mW.m**-2)phot.flux;em.UV.200-300nmfloatnullablee_logUVW1nfn[0.01/0.021]? Uncertainty in logUVW1nfnlog(mW.m**-2)stat.error;phot.flux;em.UV.200-300nmfloatnullableUVM2mag[11.19/13.04]? Swift/UVOT UVM2 band apparent magnitudemagphot.mag;em.UV.200-300nmfloatnullablee_UVM2mag[0.04]? Uncertainty in UVM2magmagstat.error;phot.mag;em.UV.200-300nmfloatnullableUVM2Flux[4.6/25.54]? Swift/UVOT UVM2 band flux densitymJyphot.flux;em.UV.200-300nmfloatnullablee_UVM2Flux[0.09/0.4]? Uncertainty in UVM2FluxmJystat.error;phot.flux;em.UV.200-300nmfloatnullablelogUVM2nfn[-10.21/-9.46]? Log Swift/UVOT UVM2 band {nu}F_{nu}_; erg/s/cm^2^log(mW.m**-2)phot.flux;em.UV.200-300nmfloatnullablee_logUVM2nfn[0.005/0.015]? Uncertainty in logUVM2nfnlog(mW.m**-2)stat.error;phot.flux;em.UV.200-300nmfloatnullableUVW2mag[11.14/13.03]? Swift/UVOT UVW2 band apparent magnitudemagphot.mag;em.UV.100-200nmfloatnullablee_UVW2mag[0.03/0.04]? Uncertainty in UVW2magmagstat.error;phot.mag;em.UV.100-200nmfloatnullableUVW2Flux[4.4/25.8]? Swift/UVOT UVW2 band flux densitymJyphot.flux;em.UV.100-200nmfloatnullablee_UVW2Flux[0.1/0.7]? Uncertainty in UVW2FluxmJystat.error;phot.flux;em.UV.100-200nmfloatnullablelogUVW2nfn[-10.2/-9.4]? Log Swift/UVOT UVW2 band {nu}F_{nu}_; erg/s/cm^2^log(mW.m**-2)phot.flux;em.UV.100-200nmfloatnullablee_logUVW2nfn[0.007/0.016]? Uncertainty in logUVW2nfnlog(mW.m**-2)stat.error;phot.flux;em.UV.100-200nmfloatnullableJ/ApJS/275/23/table6The 0.3-10keV IDVs in Mrk 421 during 2018 April -- 2023 DecemberFvarFractional variability amplitude%phot.mag;arith.ratiofloate_FvarFvar uncertainty%stat.errorfloatalpGamPhoton index value {alpha} {Gamma} (2)spect.indexcharbCurvature parameter (2)stat.fit.paramcharEpSynchorotron SED peak energy (2)keVem.energycharSpSynchrotron SED peak height (2)1e-10mW.m**-2phot.fluxcharNotesAdditional note code (s) (3)meta.notecharrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObsIDSwift observation identifier (1)meta.id;obs.param;obscharDatesObservation start dates (YYYY-MM-DD)/Modified Julian Datetime.start;obscharDeltat[0.07/23.98] Total observation length; includes interval between orbitshtime.intervalfloatchi2Model reduced {chi}^2^stat.fit.chi2floatdofDegrees of freedomstat.fit.dofintBin? Time bin for variability searchstime.intervalintnullablef_Bin[Or] "Or"meta.codecharJ/ApJS/275/23/table12Fastest variability of spectral parameters within the 1-ks time intervalrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObsID-1? Swift observation identifier for photon index parametermeta.id;obs.param;obsintnullablealpha[0.05/0.17]? Change in the photon index at 1 keV for ObsID-1spect.indexfloatnullablee_alpha[0.02/0.04]? Uncertainty in the photon index changestat.error;spect.indexfloatnullableType-1? Direction for ObsID-1 (1)meta.codecharDeltat-1[0.13/0.99]? Fraction of the 1-ks time interval for ObsID-1kstime.interval;arith.ratiofloatnullableGIndicates the 0.3-10 keV photon index Gammameta.notecharObsID-2? Swift observation identifier for curvature parametermeta.id;obs.param;obsintnullableb[0.1/0.31]? Curvature parameter for ObsID-2stat.fit.paramfloatnullablee_b[0.03/0.08]? Uncertainty in bstat.errorfloatnullableType-2Direction for ObsID-2 (1)meta.codecharDeltat-2[0.13/0.99]? Fraction of the 1-ks time interval for ObsID-2kstime.interval;arith.ratiofloatnullableObsID-3[11325001/96557016] Swift observation identifier for peak energymeta.id;obs.param;obsintl_EpLimit flag on Epmeta.code.errorcharEp[0.1/20.53] Peak energykeVem.energyfloate_Ep[0.09/0.9]? Uncertainty in EpkeVstat.error;em.energyfloatnullableType-3Direction for ObsID-3 (1)meta.codecharDeltat-3[0.13/0.98] Fraction of the 1-ks time interval for ObsID-3kstime.interval;arith.ratiofloatJ/ApJS/275/23/table13Results of the XRT spectral analysis with a simple power-law modele_F2-10[0.13/6] Uncertainty in F2-101e-11mW.m**-2stat.error;phot.flux;em.X-ray.mediumfloatF0.3-10[14.26/371] Unabsorbed 0.3-10keV flux; 10^-11^erg/s/cm^2^1e-11mW.m**-2phot.flux;em.X-rayfloatrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObsIDSwift observation identifiermeta.id;obs.param;obscharExp[87/580]? Observation segment used for analysissinstr.setup;obsintnullablealpha[0.3/6.2] Photon index at 0.3-10keVspect.indexfloate_alpha[0.01/0.1] Uncertainty in alphastat.error;spect.indexfloatNorm[0.3/6.2] Normalization; 10xKstat.fit.paramfloate_Norm[0.01/0.1] Uncertainty in Normstat.errorfloatchi2[0.86/1.2] Reduced {chi}^2^ valuestat.fit.chi2floatDoF[32/250] Degrees of Freedomstat.fit.dofintF0.3-2[11.38/167] Unabsorbed 0.3-2keV flux; 10^-11^erg/s/cm^2^1e-11mW.m**-2phot.flux;em.X-ray.softfloate_F0.3-2[0.24/2.71] Uncertainty in F0.3-21e-11mW.m**-2stat.error;phot.flux;em.X-ray.softfloatF2-10[2.87/204] Unabsorbed 2-10keV flux; 10^-11^erg/s/cm^2^1e-11mW.m**-2phot.flux;em.X-ray.mediumfloate_F0.3-10[0.2/6.02] Uncertainty in F0.3-101e-11mW.m**-2stat.error;phot.flux;em.X-rayfloatJ/ApJS/275/23/table14Fast transitions from logarithmic to powerlaw spectra or/and converselyrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTimeObservation time code (1)meta.codecharExp[1/8]? Observation segment used for analysismeta.id;time.expointnullableObsID[11445007/206476000] Swift observation identifiermeta.id;obs.param;obslongTransTransition progress (2)phys.atmol.transProb;phys.atmol.transitionchar