Spectral Fits
Simultaneity: Although it is known that the slope of the X-ray spectrum of 3C 273 changes with time, examination of the softness ratio against time (see lightcurve plots below) shows that there was no detectable spectral variability in either of the two campaigns. Therefore we do not enforce exactly identical time intervals (GTI) for spectral extraction, in favor of improving signal-to-noise.
NOTE also that in the July 1996 campaign the BeppoSAX observation is only quasi-simultaneous with ASCA and RXTE.
The Model is a power-law with Galactic absorption only (1.79e20 cm-2). Therefore there is only 1 free parameter (the power-law slope) in all cases (apart from the independent normalizations).
Energy Range: To ensure fair, direct comparison we must use identical energy ranges. Note that the ranges for ASCA/PCA and ASCA/BeppoSAX comparisons are different.
Iron K Line: The iron line is strong in the July 1996 campaign and affects the slope measurements. Therefore we REMOVE data in the iron K band in BOTH sets of observations.
Statiscal Errors quoted are for 90% confidence, 1 interesting parameter.
JULY 1996: 3-10 keV fits, excluding 4.5-6.5 keV Fe-K region
DETECTOR | Photon Index | 4-10 keV flux (1) | CHI-SQUARE/D.O.F. |
PCA | 1.648 (1.640-1.657) | 5.5 | 16.3/10 |
SIS0 | 1.675 (1.612-1.741) | 4.3 | 131.1/103 |
SIS1 | 1.588 (1.515-1.663) | 4.4 | 90.0/95 |
GIS2 | 1.657 (1.603-1.712) | 4.4 | 230.7/216 |
GIS3 | 1.667 (1.620-1.715) | 4.6 | 253.5/241 |
SIS+GIS (2) | 1.654 (1.626-1.683) | 4.4 | 707.8/658 |
SIS+GIS (MECS comp) (2,3) |
|
4.4 | 768.3/688 |
MECS (3) |
|
4.4 | 44/52 |
JUNE 1998: 3-10 keV fits, excluding 4.5-6.5 keV Fe-K region
DETECTOR | Photon Index | 4-10 keV flux (1) | CHI-SQUARE/D.O.F. |
PCA | 1.676 (1.666-1.687) | 8.7 | 5.6/9 |
SIS0 | 1.694 (1.656-1.733) |
6.3 | 129.4/133 |
SIS1 | 1.635 (1.592-1.678) | 6.6 | 126.3/124 |
GIS2 | 1.670 (1.636-1.704) | 6.6 | 291.4/315 |
GIS3 | 1.652 (1.624-1.681) | 7.2 | 341.5/347 |
SIS+GIS (2) | 1.656 (1.634-1.674) |
6.7 | 816.2/843 |
SIS+GIS (MECS comp) (2,3) |
|
6.7 | 784.3/753 |
MECS (3) |
|
6.8 | 44/52 |
(1) Flux in units of 10-11 erg cm-2 s-1.
(2) Simultaneous fit with SIS0,SIS1,GIS2, and GIS3 with the relative normalizations free. The flux is averaged over four instruments.
(3) The energy range of the data for comparison of ASCA with BeppoSax is 1.5-4 keV and 8-10 keV (i.e. excluding 4-8 keV for the iron line). The BeppoSAX results are taken from report by Grandi and Guainazzi.
Previous: The Bottom Line
Next: Observation Log & Lightcurves
Back: "Simultaneous Observations of 3C 273" Main Page
This file was last modified on Tuesday, 19-Oct-2021 16:18:05 EDT
Curator:
HEASARC Guest Observer Facility
If you have any questions concerning ASCA, visit our Feedback form.