We present the results from a detailed spectral and timing study of Mrk 421 based on the rich archival Swift data obtained during 2009-2012. Best fits of the 0.3-10 keV spectra were mostly obtained ...using the log-parabolic model showing the relatively low spectral curvature that is expected in the case of efficient stochastic acceleration of particles. The position of the synchrotron spectral energy density peak Ep of 173 spectra is found at energies higher than 2 keV. The photon index at 1 keV exhibited a very broad range of values a = 1.51-3.02, and very hard spectra with a < 1.7 were observed during the strong X-ray flares, hinting at a possible hadronic jet component. The spectral parameters varied on diverse timescales and showed a correlation in some periods, which is expected in the case of first- and second-order Fermi acceleration. The 0.3-10 keV flux showed strong X-ray flaring activity by a factor of 3-17 on timescales of a few days-weeks between the lowest historical state and that corresponding to a rate higher than 100 cts s−1. Moreover, 113 instances of intraday variability were revealed, exhibiting shortest flux-doubling/halving times of about 1.2 hr, as well as brightenings by 7%-24% in 180-720 s and declines by 68%-22% in 180-900 s. The X-ray and very high-energy fluxes generally showed a correlated variability, although one incidence of a more complicated variability was also detected, indicating that the multifrequency emission of Mrk 421 could not be generated in a single zone.
Abstract
The X-ray variability of the BL Lacertae source Mrk 501 was studied during 11.5 yr of monitoring with Swift. Here, we report the results of this study pertaining to the epoch of 2014 ...March–October, when our target showed the most powerful and long-lasting X-ray flaring activity. This epoch was characterized by X-ray flares varying in amplitude by factors of 2–5 on time-scales of a few weeks or shorter. We detected 35 instances of the intraday variability, sometimes occurring within the 1 ks observational runs. The X-ray flux was generally correlated with the TeV flux, while the 0.3–300 GeV and optical-UV fluxes did not show a significant correlation. Some notable incidences of more complicated variability patterns could also be recognized, indicating that the high-energy emission in Mrk 501 arose from an emission region more complex than a single zone. The best fits of the 0.3–10 keV spectra were mainly obtained using the logparabola model. Strong spectral variability was detected, affecting the slope but not the curvature of the spectrum. In strong flares, the spectral index became harder than 1.70. The spectral evolution was characterized by a harder-when-brighter behaviour, shifting the peak of the spectral energy distribution by about 20 keV that happens rarely in blazars.
We present the results of the Swift observations of the nearby BL Lac object Mrk 421 during 2013 November-2015 June. The source exhibited a strong long-term variability in the 0.3-10 keV band, with a ...maximum-to-minimum flux ratio of 13, and underwent X-ray flares by a factor of 1.8-5.2 on timescales of a few weeks or shorter. The source showed 48 instances of intraday flux variability in this period, which sometimes was observed within the 1 ks observational run. It was characterized by fractional amplitudes of 1.5(0.3)%-38.6(0.4)% and flux doubling/halving times of 2.6-20.1 hr. The X-ray flux showed a lack of correlation with the TeV flux on some occasions (strong TeV flares were not accompanied by comparable X-ray activity and vice versa), indicating that the high-energy emission in Mrk 421 was generated from an emission region more complex than a single zone. The best fits of the 0.3-10 keV spectra were mainly obtained using the log-parabola model, showing a strong spectral variability that generally followed a "harder-when-brighter" trend. The position of the synchrotron spectral energy distribution peak showed an extreme range from a few eV to ∼10 keV that happens rarely in blazars.
ABSTRACT We present the results of the Swift and NuSTAR observations of the nearby BL Lac object Mrk 421 during 2013 January-June. The source exhibited a strong long-term variability in the 0.3-10 ...keV and 3-79 keV bands with the maximum-to-minimum daily-binned flux ratios of 22 and 95, respectively, in about 3 months, mainly due to unprecedented strong X-ray outbursts by more than an order of magnitude in both bands within 2 weeks in 2013 April when the 0.3-10 keV count rate exceeded the level of 200 cts s−1 for the first time, and Mrk 421 became one of the brightest sources in the X-ray sky. The source was also very active on intra-day timescales, and it showed flux doubling and halving timescales of 1.16-7.20 hr and 1.04-3.54 hr, respectively. On some occasions, the flux varied by 4%-23% within 300-840 s. During this period, the source also exhibited some of the most extreme X-ray spectral variability ever reported for BL Lacs-the location of the synchrotron spectral energy distribution peak shifted from a few eV to ∼10 keV, and the photon index at 1 keV and curvature parameter varied on timescales from a few weeks down to intervals shorter than 1 ks. MAGIC and First G-APD Cherenkov Telescope observations also revealed a very strong very high energy (VHE) flare during April 11-17. The UV and HE γ-ray flares were much weaker compared to their X-ray counterparts, and they generally showed significantly stronger correlation with each other than with the X-ray fluxes.
We present detailed results of Swift observations of the nearby TeV-detected blazar Mrk 421, based on the rich archival data obtained during 2005 March-2008 June. The best fits of the 0.3-10 keV ...spectra were mainly obtained using the log-parabolic model, yielding low spectral curvatures expected in the case of the efficient stochastic acceleration of particles. During strong X-ray flares, the position of the synchrotron spectral energy distribution peak was beyond 8 keV for 41 spectra, while it sometimes was situated at the UV frequencies in quiescent states. The photon index at 1 keV exhibited a broad range, and the values were observed during the strong flares, hinting at the possible presence of a jet hadronic component. The spectral parameters were correlated in some periods, expected in the framework of the first- and second-order Fermi accelerations of X-ray emitting particles, as well as in the case of turbulence spectrum. The 0.3-10 keV flux and spectral parameters sometimes showed very fast variability down to the fluctuations by 6-20% in 180-960 s, possibly related to the small-scale turbulent areas containing strongest magnetic fields. X-ray and very high-energy fluxes often showed correlated variability, although several occurrences of more complicated variability patterns are also revealed, indicating that the multifrequency emission of Mrk 421 could not be generated in a single zone.
We present the detailed timing and spectral results obtained during the Swift observations of the TeV-detected blazar 1ES 1959+650 in 2016 August-2017 November. The source continued its trend of ...gradually enhancing X-ray flaring activity in the 0.3-10 keV energy range, starting in 2015 August, and a new highest historical brightness state was recorded twice. A long-term high state was superimposed by both weak and strong flares, and we detected 32 instances of intraday X-ray flux variability, including several occasions of extremely fast fluctuations with fractional amplitudes of 5.4%-7.5% within 1 ks exposures. The 0.3-10 keV spectra generally showed a best fit with the log-parabolic model, yielding a very wide range of the curvature parameter b and the photon index at 1 keV. The position of the synchrotron SED peak Ep showed an extreme variability on various timescales between energies less than 0.1 keV and 7.7 0.7 keV, with 25% of the spectra peaking at hard X-rays. In 2017 May-November, the source mostly showed lower spectral curvature and an anticorrelation b-Ep, expected in the case of efficient stochastic acceleration of X-ray-emitting electrons. The 0.3-100 GeV and optical-UV fluxes also attained their highest historical values in this period, although the latter showed an anticorrelation with the 0.3-10 keV emission, which is explained by the stochastic acceleration of electrons with a narrow initial energy distribution, having an average energy significantly higher than the equilibrium energy.
We present the results based on the monitoring of the high energy peaked BL Lacertae object 1ES 2344+514 with the satellite
Swift
during 2005–2015. Our timing study shows that the source was highly ...variable on longer (weeks-to-months) time-scales with the 0.3–10 keV flux ranging by a factor of 13.3. The flux variability exhibited an erratic character, changing its amplitude and minimum flux level from flare to flare. In some epochs, an X-ray flare was accompanied by enhanced optical-UV activity, although the uncorrelated 0.3–10 keV and lower-frequency variabilities were also often seen. Our target was significantly passive on intra-day timescales compared to other HBLs. The logparabolic distribution of the X-ray emitting electrons and the underlying physical processes seem to be less important for this object in some epochs, since only seven out of the relatively rich spectra showed a curvature, while the majority of the 0.3–10 keV spectra fitted with a simple powerlaw well. The photon index varied on diverse timescales, and the source showed mainly a “harder-when-brighter” spectral evolution. In the hardness ratio–flux plane, 1ES 2344+514 showed both clockwise and counterclockwise loops, indicating a complex spectral evolution with the flux.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Cardiovascular diseases (CVD) continue to be the leading cause of death and disability worldwide, representing 30% of all death. In Georgia 36% of all death caused by ischemic heart disease and 23% ...caused by stroke. There is a limited data on association between socioeconomic status (SES) and CVD risk in Georgia. Our study aims at assessing association between SES and CVD risk factors in a cohort of adult Georgians. A cross-sectional study was conducted in the region of Western Georgia between June 2007 - June 2008. 1196 individuals aged 40-70 years were enrolled in the study. To assess SES we collected information about education, income, ownership of a private transport, and employment. CVD risk was assessed by the WHO/ISH risk classification scale. In addition, anthropometric measurements were conducted in each study participant. Low education level (adjusted odds ratio (aOR) 2.85; 95% confidence interval (CI), 1.57-5.17), obesity (aOR 2.13, 95% CI 1.16 -3.92) and abdominal obesity (aOR 2.21, 95% CI 1.26 -3.87) were statically significantly associated with more than 10% 10 year risk of a fatal or non-fatal cardiovascular event. Lower education level (not finished high school -aOR 2.21 95% CI 1.44 - 3.38, undergraduate - aOR 1.52, 95% CI 1.12 - 2,05), income 120 USD or more (aOR 0.73, 95% CI 0.54 -1.00), overweight (aOR 1.68, 95% CI 1.07 - 2.63), obesity (aOR 1.58, 95% CI 1.04 - 2.41), and abdominal obesity (aOR 1.43, 95% CI 1.01 - 2.03) were found to be statistically significant predictors of CVD in our study population. We found that education level, income, body mass index and waist to hip ratio are CVD risk factors. Public health authorities, as well as clinicians should consider this finding in primary and secondary prevention and organize multidisciplinary teams to address those risk factors.
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