Command Line Scripts for Generating Backgrounds

These command line scripts allow one to generate background event files.

make_background_file

The make_background_file generates a simulated observation of background in a standard event file format which can then be used as the background for and observation or processed by standard tools such as CIAO, HEATOOLS, XSPEC, etc.

usage: make_background_file [-h] [--overwrite] [--dither_shape DITHER_SHAPE]
                            [--dither_size DITHER_SIZE]
                            [--input_sources INPUT_SOURCES] [--subpixel_res]
                            [--absorb_model ABSORB_MODEL] [--nh NH]
                            [--random_seed RANDOM_SEED]
                            [--ptsrc_bkgnd | --no_ptsrc_bkgnd]
                            [--instr_bkgnd | --no_instr_bkgnd]
                            [--foreground | --no_foreground]
                            out_file exp_time instrument sky_center

Run the instrument simulator and produce a simulated background event file.

positional arguments:
  out_file              The name of the event file to be written.
  exp_time              The exposure time to use, in seconds.
  instrument            The name of the instrument to use, or alternatively
                        the name of a JSON file which contains an instrument
                        specification.
  sky_center            The center RA, Dec coordinates of the observation, in
                        degrees, comma-separated

optional arguments:
  -h, --help            show this help message and exit
  --overwrite           Overwrite an existing file with the same name.
  --input_sources INPUT_SOURCES
                        Use a previously written table of point sources as
                        input instead of generating them.
  --subpixel_res        Don't uniformly distribute event positions within
                        pixels.
  --no_dither           Turn dithering off entirely.
  --dither_params DITHER_PARAMS
                        The parameters controlling the size and period of
                        dither. Four floats joined by commas, in the form of
                        x_amp,y_amp,x_period,y_period. The first two numbers
                        are in arcseconds and the second are in seconds.
                        Default: 8.0,8.0,1000.0,707.0
  --absorb_model ABSORB_MODEL
                        The absorption model to use for foreground galactic
                        absorption. Default: 'wabs'
  --nh NH               The galactic hydrogen column in units of 10**22
                        atoms/cm**2. Default: 0.05
  --random_seed RANDOM_SEED
                        A constant integer random seed to produce a consistent
                        set of random numbers.
  --ptsrc_bkgnd         Turn the point-source background on.
  --no_ptsrc_bkgnd      Turn the point-source background off.
  --instr_bkgnd         Turn the instrumental background on.
  --no_instr_bkgnd      Turn the instrumental background off.
  --foreground          Turn the galactic foreground on.
  --no_foreground       Turn the galactic foreground off.

Examples

Changing Instrument Specification

This example uses the pre-built HDXI instrument specification, assuming a 50 ks observation with the pointing (RA, Dec) = (30, 45) degrees.

[~]$ make_background_file bkg_evt.fits 50.0,ks hdxi 30.,45. --overwrite

The same, but use the HDXI specification with mirror diameter of \(d\) = 3 m and focal length of \(f\) = 20 m:

[~]$ make_background_file bkg_evt.fits 50.0,ks hdxi_3x20 30.,45. --overwrite

See The instrument Argument for details on the options for the instrument argument.

This example uses a JSON file created by the user, which contains a custom instrument specification. See Creating New Instrument Specifications for details on how to do this.

[~]$ make_background_file bkg_evt.fits 50.0,ks my_inst.json 30.,45. --overwrite

Changing Dither

Change the dither amplitudes to 32 arcseconds and the periods to 707 and 1200 seconds:

[~]$ make_background_file bkg_evt.fits 50.0,ks hdxi 30.,45. --dither_params=32.,32.,707.,1200. --overwrite

Turn dither off entirely:

[~]$ make_background_file bkg_evt.fits 50.0,ks hdxi 30.,45. --no_dither --overwrite

Customizing the Background

Turn off the instrumental background:

[~]$ make_background_file bkg_evt.fits 50.0,ks hdxi 30.,45. --no_instr_bkgnd --overwrite

Turn off the Galactic foreground:

[~]$ make_background_file bkg_evt.fits 50.0,ks hdxi 30.,45. --no_foreground --overwrite

Turn off the point-source background:

[~]$ make_background_file bkg_evt.fits 50.0,ks hdxi 30.,45. --no_ptsrc_bkgnd --overwrite

Any combination of these may be used to turn multiple components off or all of them.

Use a pre-made ASCII table of point-source properties to generate the point-source background:

[~]$ make_background_file bkg_evt.fits 50.0,ks hdxi 30.,45. --input_sources=my_ptsrc.dat --overwrite

Change the foreground galactic absorption for the point-source background, and set the absorption model to “tbabs”:

[~]$ make_background_file bkg_evt.fits 50.0,ks hdxi 30.,45. --absorb_model="tbabs" --nh=0.02 --overwrite