- The Region of Interest.
HESS J1857+026 is in the same region than the SNR W44 which is the brightest source of the region.
Fig 1. Counts map of the region above 6 GeV.
The shape of W44 was fitted by an Elliptical Ring (ref. 1) and it spectra by a broken power law.
We fitted again the spectra of W44 by a Log-Parabola and made morphological studies of W44.
The main point is that the results are consistent with previous work.
Fig. 2. Comparison between the result of ref. 1 (red contours) and our results (white ring) . There is no error taken into account in this templates.
Model |
RA(°) |
DEC(°) |
Semi Major Axis (°) |
Semi Minor Axis (°) |
Pos.Ang.(°) |
283,990 |
1,355 |
0,300 |
0,190 |
327,000 |
|
This study |
284.015(+/-0.004) |
1.392(+/-0.005) |
0.335(+0.117 -0.086) |
0.207 (+0.023 -0.021) |
329.8 +/- 25.3 |
Table 1. Values of both model with only statistical errors in the case of our study.
Fig. 3 SED of W44 given by pointlike.
2. HESS 1857+026 Morphology above 10GeV
We made an analysis of the morphology of HESS 1857+026 above 10GeV. Three hypotheses were tested : point source, gaussian and disk.
No significant extension was found has can be seen in the following table. The delta show that we do not detect any extension of the source.
Hypothesis |
Point |
Gaussian |
Disk |
||
|---|---|---|---|---|---|
TS |
33.38 |
41.35 |
42.21 |
||
Loglike |
-48201.50 |
-48197.55 |
|
-48197.98 |
|
Table 2. TS and Loglike found above 10GeV for a point source, a gaussian and a Disk.
Fig. 4. Excess TSMap of a 10° * 10° roi around HESS 1856+026.
Fig. 5 Zoom of the previous TS map with a factor of 5. The green square represent an 2° * 2° roi and the green contours are those of HESS source.
Bibliography :
(1) Abdo et al., Science, 327, 1103-1106, 2010