Data exploration

Note

For a general introduction to HENDRICS’s workflow, please read the Introductory concepts and example analysis tutorial

In this tutorial, we will explore a NuSTAR dataset and try to get a general view of the observed source.

Load events and GTIs

First of all, let us load the event list in a more manageable file

$ HENreadevents mistery_source_1_00.evt –min-length 512

Note that the understanding of good time intervals extensions is sometimes difficult to do automatically, as different missions have different standard naming of these extensions. Most NASA missions should be correctly handled, plus XMM-Newton; however, if you notice something strange in the GTI extension reading, or if you are using non-standard user GTI extensions, please specify explicitly the extension names or regular expressions. For example, to read the user-defined GTIs and the standard GTIs for detector 01 of XMM-Newton/EPIC-pn the command might be something like:

$ HENreadevents mistery_source_xmm.fits –gtistring ‘GTI001.*,STDGTI01’

See the help of HENreadevents for more details.

Calibrate events

Then we can “calibrate” it, which means that we are measuring the energy of each photon in units of kilo-electronVolts (keV).

$ HENcalibrate mistery_source_1_00_nustar_fpma_ev.nc

The latter works only for NuSTAR, and if the official rmf files are in the CALDB. Otherwise, the --rmf option has to be used, providing a redistribution matrix file (see HENcalibrate -h for details). The min-length option says to discard GTIs shorter than 512.

Create and plot a light curve

Then, let’s calculate and plot a light curve binned at 10 s, between 3 and 5 keV, and taking a “safe” interval around GTIs of 100 s (for example, to account for increased particle background close to SAA)

$ HENlcurve -b 10 mistery_source_1_00_nustar_fpma_ev_calib.nc –safe-interval 100 100 -e 3 5

$ HENplot mistery_source_1_00_nustar_fpma_E3-5_lc.nc

lc.png

This plot shows the GTI borders in red, and the light curve before (grey) and after (blue) filtering for safe intervals around GTIs. Some intervals with decreasing flux can be seen in the grey light curve, a sign that a filtering _was_ needed.

Color-color diagram

Now, let’s produce a color-color diagram.

First of all, we need to produce two color light curves:

$ HENcolors -b 100 mistery_source_1_00_nustar_fpma_ev_calib.nc -e 2 5 5 8 $ HENcolors -b 100 mistery_source_1_00_nustar_fpma_ev_calib.nc -e 8 12 12 30

Then, we can plot these new light curves and see if there is anything interesting there.

$ HENplot –CCD mistery_source_1_00_nustar_fpma_E_8-5_over_5-2.nc mistery_source_1_00_nustar_fpma_E_30-12_over_12-8.nc

colorcolor.png