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Cross Calibration

This page describes the instrumental cross calibration. This is performed separately for bursts and observations

Observations

The routine cross_calibrate.pro now searches the observations for pairs from different instruments (SAX-RXTE, RXTE-JEM-X) that overlap. (There are no overlapping JEM-X-SAX observations, as these two instruments were not active simultaneously).

We consider a minimum overlap fraction of $ f=0.1 $, where $ f=\Delta t_\mathrm{overlap}/(t_\mathrm{max}-t_\mathrm{min}) $, $ \Delta t_\mathrm{overlap} $ is the time in common to both instruments, and $ t_\mathrm{min} $, $ t_\mathrm{max} $ represents the maximal extent of the two observations.

We then calculate a linear cross-calibaration between the two instruments, following a single iteration of outlier detection. We use the Bayesian method of Kelly et al. (2007) to derive the linear correlation coefficients; this method takes into account the errors in both x and y, as well as any possible correlation of the errors. The results are as follows.

RXTE-WFC

last updated 2015 October 29

We cross-correlate the count rate separately to the flux.

The points marked in red are identified as outliers, and are excluded from the linear fit, which gives:

$ c_\mathrm{WFC} = (-0.003\pm0.006) + c_\mathrm{PCA} \times ( 0.000776\pm0.000010) $

The inverse proportionality factor is $ 1288\pm17 $, which is consistent with the value of 1300 assumed for the light curve fits to convert c/s/PCU to c/s/cm2.

The points marked in red are identified as outliers, and are excluded from the linear fit, which gives:

$ F_\mathrm{WFC} = (0.09 \pm 0.16) + F_\mathrm{PCA} \times ( 1.02 \pm 0.02 ) $

Below we list the relevant parameters for the outliers

EntrySource nameInstr.Observation IDStart time [MJD UT]Stop time [MJD UT]$ F_X $ (10-9 erg cm-2 s-1)
15884XTE J1710-281XPl40407-01-02-0051233.4597751233.60907$ 0.071\pm0.001 $
4401XTE J1710-281SW1645251233.2565051234.40480$ 0.790\pm0.102 $

RXTE-JEM-X

last updated 2015 October 29

Below is the plot showing the cross-calibration

The points marked in red are identified as outliers, and are excluded from the linear fit, which gives:

$F_\mathrm{JEM-X} = (0.06 \pm 0.05) + F_\mathrm{PCA} \times ( 0.885 \pm 0.009 )

Below we list the relevant parameters for the outliers

EntrySource nameInstr.Observation IDStart time [MJD UT]Stop time [MJD UT]$ F_X $ (10-9 erg cm-2 s-1)
19735GX 17+2XPc90022-07-01-0053102.8563053102.88130$ 1.369\pm0.003 $
209583GX 17+2IJ101810033001053102.8560753102.89916$ 23.519\pm0.748 $
19840XTE J1810-189XPj80091-01-11-0153114.9319953114.96116$ 0.099\pm0.001 $
202328XTE J1810-189IJ101850038001053114.9245553114.94543$ 1.168\pm0.614 $
209884U 1702-429XPc91023-02-01-0053609.1208853609.22713$ 1.365\pm0.002 $
388584U 1702-429IJ103500053001053609.1518553609.17284$ 3.654\pm1.754 $
21125Aql X-1XP091414-01-05-0053659.3257453659.36602$ 5.284\pm0.037 $
218373Aql X-1IJ103670029001053659.3549753659.39526$ 0.023\pm0.019 $
21125Aql X-1XP091414-01-05-0053659.3257453659.36602$ 5.284\pm0.037 $
218372Aql X-1IJ103670028001053659.3134753659.35375$ 0.038\pm0.029 $
211524U 1702-429XPj91023-02-04-0253669.8042153669.82991$ 2.033\pm0.014 $
389074U 1702-429IJ103700073001053669.8212853669.82885$ 3.974\pm1.913 $
230184U 1636-536XPc91024-01-66-1054164.4799254164.50284$ 1.440\pm0.010 $
348774U 1636-536IJ105360033001054164.4684954164.49852$ 0.145\pm1.099 $
231464U 1702-429XPa91023-02-09-0054189.8285354189.99867$ 2.407\pm0.044 $
391104U 1702-429IJ105440079001054189.9782554190.00828$ 0.787\pm0.307 $
26297Aql X-1XPc94320-02-27-0055079.4834055079.52368$ 2.278\pm0.013 $
218869Aql X-1IJ108420026001055079.4897155079.51193$ 0.241\pm0.182 $

Bursts

We use cross_calibrate.pro to carry out the same procedure for the bursts. Below is the plot for WFC, the only one with peak fluxes/fluences available

The labels are the burst ID numbers for the WFC bursts

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Page last modified on October 29, 2015, at 06:25 AM