Crab in JEMX

Problems based on the analysis of the Crab

JEM-X

1.Get your data

Using the INTEGRAL Archive Browse find the Science WIndows (ScW) of revolution 102 in which Crab pulsar wind nebulae is observed almost on-axis (off-axis angle is less than 10 arcmin).

Using the list of data given above create an observation group named crab_jmx
Do not forget to specify the ID of JEMX instruments (JMX1 or JMX2).

2.Image analysis

Create the JEM_X image of Crab with and without vignetting correction. Compare the quality of the obtained images. Determine the position of Crab and compare it with the catalog position.

Create the JEM_X mosaic image .

3. Spectral analysis

Determine the spectrum of Crab for each science window and sum the spectra from individual science windows into a single summary spectrum. Determine the flux
in 5-20 keV energy band in cts/sec with the help of xspec command

ignore **-5. 20.-**
show rate

as well as in erg/(cm^2 s) with the help of xspec command

flux 5. 20.

4. Spectral extraction from ScW and mosaic images

Using the mosaic_spec script extract the Crab spectrum from mosaic images and from several individual Science Windows. Compare the resulting spectra with the ones obtained with the standard spectral extraction procedure.

To extract spectra from mosaic one needs first to produce images in quite narrow energy bands (to get enough energy bins in the resulting spectrum) To produce images in 8 energy bins (convert the channel numbers into energy yourself, looking in JEMX RMFs) run the analysis with the following command line:

jemx_science_analysis startLevel="COR" endLevel="IMA" nChanBins=8 \
chanLow="46 59 77 102 130 153 175 199" \
chanHigh="58 76 101 129 152 174 198 223" \
IMA_skyImagesOut="RECONSTRUCTED,VARIANCE,EXPOSURE"

It is important that VARIANCE extension in each energy band is produced, since it is used in the calculation of (wieghted average) values of mosaic pixels.

Next, produce the mosaic image:

jemx_science_analysis startLevel="IMA2" endLevel="IMA2" nChanBins=8 \
chanLow="46 59 77 102 130 153 175 199" \
chanHigh="58 76 101 129 152 174 198 223" \
IMA2_viewVar=Y

Again, you have to explicitely specify that you want to keep the VARIANCE extension in the output of mosaic step
(IMA2_viewVar=Y), since the variance value at the source locaiton is the error of the flux determination in a given energy band.

Produce the spectrum of Crab from the sky images in each ScW, using the mosaic_spec

mosaic_spec "" "" DOL_idx="jmx2_sky_ima.fits"\ DOL_spec="spectrum_scw.fits(JMX2-PHA1-SPE.tpl)" EXTNAME="JMX2-SKY.-IMA" ximg=0 yimg=0\ ra=83.63 dec=22.01 posmode=0 widthmode=1 Intensity="RECONSTRUCTED"

(try to "automatize" the procedure with the help of "foreach" command). Extract the total spectrum from the mosaic image:

mosaic_spec "" "" DOL_idx="J_MOSAIC.fits"\ DOL_spec="spectrum_mosa.fits(JMX2-PHA1-SPE.tpl)" EXTNAME="JMX2-MOSA-IMA" ximg=0 yimg=0\ ra=83.63 dec=22.01 posmode=0 widthmode=1 Intensity="RECONSTRUCTED"

To analyze the spectra, you need to rebin the repsonce matrix with the help of ftool rbnrmf (see ISGRI cookbook for help with rebinning the rmf). When you have your rebinned mosaic_rmf.fits you can add the arf from the forth extension of the standard responce file, $REP_BASE_PROD/ic/jmx#/rsp/jmx#_rmf_grp_NNNN.fits.gz

5. Timing analysis

Produce 10-second resolution X-ray lightcurve of Crab in each science window and then combine the obtained lightcurves in a single summary lightcurve. Compare the Crab flux found from the spectral analysis with the flux which you find from the lightcurve.

6. Combined JEMX - ISGRI analysis

With the help of xspec combine the spectra from JEM-X and ISGRI to obtain
the spectrum of Crab in the energy 3-200 keV energy range (load the two spectra simultaneously with the help of data 1:1 and data 2:2 commands). Study the problem of cross-calibration of the two instruments.