an#abruptchangein#theidv#characteristics#of# 0954+658#
TRANSCRIPT
An abrupt change in the IDV characteristics of 0954+658 during its 2008 outburst
Nicola Marchili (MPIfR)
Collaborators: T. P. Krichbaum, K. É. Gabányi, L. Fuhrmann, A. Witzel, P. Müller, J. A. Zensus (MPIfR), L. Xiang, H.-G. Song (UAO)
Tuesday, April 12, 2011
IntraDay Variability (IDV)
Fast variability in 30-50% of flat-spectrum-radio sources:
• Time scales from hours up to a few days
• Variations from few percent up to 100% of the average flux density
• Source-intrinsic or source-extrinsic?
d < cτ Tb ∼ 1017 − 1019K
Tuesday, April 12, 2011
Source-extrinsic IDV: Annual modulation of the time scales
Tuesday, April 12, 2011
The Urumqi IDV project
The main aimTo study the changes in the variability time scales of IDV sources
The observations41 observing sessions with the Urumqi Telescope, between August 2005 and December 2009, at 5 GHz
The main targets 0716+714, 0917+624, 0954+658, 1128+592, 0235+164
The analysis methodsStructure function analysis & Wavelet analysis
14578 14579 14580 14581 14582JD-2440000
0.9
1.0
1.1
S 5GH
z [ Jy
]
0954+658 - April 2008
Tuesday, April 12, 2011
Annual modulation plot for 0954+658
0 90 180 270 360DoY
0
1
2
3
4 [
d ]
wt30d-aver
0 90 180 270 360DoY
0
1
2
3
4sf30d-aver
Tuesday, April 12, 2011
Variability time scales vs time
2005 2006 2007 2008 2009 2010
1.0
1.5
S 5GH
Z [ Jy
]
2005 2006 2007 2008 2009 2010year
0
1
2
3
4
[ d
]
wt
Tuesday, April 12, 2011
Variability time scales vs time
2005 2006 2007 2008 2009 2010
1.0
1.5
S 5GH
Z [ Jy
]
2005 2006 2007 2008 2009 2010year
0
1
2
3
4
[ d
]
wt
2005 2006 2007 2008 2009 2010
1.0
1.5
S 5GH
Z [ Jy
]
2005 2006 2007 2008 2009 2010year
0
1
2
3
4
[ d
]
wtsf
Tuesday, April 12, 2011
Structure Functionvs Wavelet
0 1 2 3 4 5wv
0
1
2
3
4
5sf
0716+714, 0917+624, 1128+592fit: slope 1.0, corr. 0.90954+568 (I)fit: slope 1.0, corr. 0.8
Tuesday, April 12, 2011
Structure Functionvs Wavelet
0 1 2 3 4 5wv
0
1
2
3
4
5sf
0716+714, 0917+624, 1128+592fit: slope 1.0, corr. 0.90954+568 (I)fit: slope 1.0, corr. 0.8
0 1 2 3 4 5wv
0
1
2
3
4
5sf
0716+714, 0917+624, 1128+592fit: slope 1.0, corr. 0.90954+568 (II)fit: slope 0.0, corr. 0.0
Tuesday, April 12, 2011
0.1 1! [ d ]
10-4
10-3
SF
08.2005-02.200803.2008-12.2009
Structure Functionbefore and after March 2008
Tuesday, April 12, 2011
0.1 1! [ d ]
10-4
10-3
SF
08.2005-02.200803.2008-12.2009
Structure Functionbefore and after March 2008
0.1 1! [ d ]
10-4
10-3
SF
08.2005-02.200803.2008-12.2009
Tuesday, April 12, 2011
Multiple time scales?
• Disagreement between SF and wavelet
• Change in the SF slope after March 2008
Source-extrinsic + Source-intrinsic variability?
Scintillation of multiple compact components?
Tuesday, April 12, 2011
Summary
• (weak) evidence for annual modulation
• remarkable change in the variability characteristics after March 2008
• appearance of multiple time scales in the light curves
Tuesday, April 12, 2011