Markarian 421 - simultaneous multiwavelength observations of an outburst PDF Print
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Spectral energy distribution with the SSC model for the 2006 (teal blue) and 2008 (red) data. The data from XMM-Newton OM, XMM-Newton EPN, MAGIC, Whipple and VERITAS are shown with triangles, filled circles, squares, diamonds, and crosses, respectively, with data taken during the MAGIC, Whipple and VERITAS observation times shown in green, blue and red.


Simultaneous multiwavelength observations of Markarian 421 during outburst

 

 

Reference:  V. A. Acciari et al. (The VERITAS Collaboration), Astrophysical Journal 703: 169, 2009

Full text version

ArXiv version: ArXiV:0907.3923

Contact person: Daniel Gall

 

Markarian 421 was the first blazar, as well as the first extragalactic source, to be detected at TeV energies and has since remained one of the most active VHE blazars.  Two intense simultaneous multi-wavelength campaigns were triggered on Markarian 421 in 2006 and 2008, using XMM-Newton to cover the X-ray and UV band as well as VERITAS, MAGIC and the Whipple10m to cover the VHE gamma-ray band.  These campaigns were carefully coordinated to capture strictly simultaneous observations at the various wavelengths and examine the spectral variability and potential correlations in variability across the bands.  Simultaneous observations are critical due to Markarian 421's history of rapid variability.  This is the first dedicated attempt to capture strictly simultaneous broad band observations  of Markarian 421 with the newest generation of TeV observatories working with XMM-Newton.

 

 

 

 

 

 

Figures from paper (click to get full size image): 

 

 
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Figure 2 (shown above): Spectral energy distribution with the SSC model for the 2006 (teal blue) and 2008 (red) data. The data from XMM-Newton OM, XMM-Newton EPN, MAGIC, Whipple and VERITAS are shown with triangles, filled circles, squares, diamonds, and crosses, respectively, with data taken during the MAGIC, Whipple and VERITAS observation times shown in green, blue and red.
 
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Figure 3: Plot of light curves from (a) 2006 observations and (b) 2008 observations. XMM-Newton OM data (200-300nm) is shown with triangles in units of cts s−1. XMM-Newton EPN data (0.5 - 10.0 keV) is shown with filled circles in units of cts s−1. Error bars for the EPN data are smaller than the data points. The data from MAGIC, Whipple and VERITAS are shown with squares, diamonds, and crosses, respectively in units of photons cm−1 s−2 (above 250 GeV). Note that the EPN and OM scales differ on the 2006 and 2008 panels.
 
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Figure 4: Plot of simultaneous XMM-Newton EPN (0.5 - 10 keV) and VHE data to search for correlation between the two bands. MAGIC data points are designated by squares, Whipple points by diamonds, and VERITAS points by crosses. All XMM-Newton data used for this plot was analyzed with XMMSAS version 8.0.0 to maintain consistency. The dotted line is the X-ray/VHE correlation best fit from B la˙zejowski et al. (2005) converted to the appropriate units. The dot- dashed line has the same slope but is scaled to the average of our Whipple 10m results.
 
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Figure 5: Hardness ratio vs intensity plots to study spectral hysteresis during the increase in activity centered around 17 ks into the 2006 XMM-Newton observation. Three bands are used for this analysis. The upper panel uses (3-10 keV)/(1-3 keV) for the hardness ratio, the middle panel uses (1-3 keV)/(0.5-1 keV), and the bottom panel uses (3-10 keV)/(0.5-1 keV). The arrows indicate the progression of time. Clockwise hysteresis is present in all three panels, indicating a lag in the lower energy bands.

 

Last Updated on Thursday, 27 January 2011 07:58
 

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