Introduction

The following is the simplest example of the data reduction of the GSC-low data of Crab to make the spectra and light-curves. In this example, mxproduct is run at the root data-directory, which contains the directory obs/ .

 mxproduct  83.633083 22.014500 2010-01-01 2010-01-31 object=crab

This will create the GSC science products of spectra for the default region, response file for them, and light-curves in the default energy band, all for the region around the coordinates of (RA, DEC) [J2000] for the period between TSTART and TSTOP. The science product files are stored in the directory ./products/ (or, user-specified name by the option, outpath), which is created if it does not exist.

The ftool help is given by

 fhelp mxproduct

or read through this document for the complete reference.

Overview

The format of mxproduct is,

mxproduct  RA Dec  TSTART TSTOP [OPTIONS]

mxproduct requires 4 mandatory parameters; the center coordinates (RA and Dec) and the start and end time. RA and Dec should be given in degree (J2000). The format of TSTART and TSTOP is either YYYY-MM-DD or YYYY-MM-DDThh:mm:ss, where YY, MM, DD, hh, mm, ss are year, month, day, hour, minute and second, respectively. When only YYYY-MM-DD is specified, TSTART is identical to YYYY-MM-DDT00:00:00 and TSTOP is identical to YYYY-MM-DDT23:59:59.

In addition, mxproduct accepts several optional arguments, each of which is given in the format of option=PARAMETER.

1. Instrument/Mode
2. Spatial filter
3. Energy-band filter.

Here is the detail of how to specify optional parameters.

Instrument/Mode

The GSC has 2 data types: gsc_low and gsc_med. Users must choose either of them. Our recommendation is gsc_low, which is the default. In case to choose the medium data, set the option gscdl=med.

Spatial filter (Region files, recommended)

You can supply the source and the background region files for GSC and/or SSC. See the options srcregfile_gsc, bgdregfile_gsc, srcregfile_ssc, bgdregfile_ssc. mxproduct runs without region files, in which case the background region is automatically chosen before and after the scan of the source. However, it is reported that the estimated background level is underestimated when region files are not specified. Thus, we recommend specifying the source and background region files.

The region-file format is the ds9 format in plain text with the fk5 coordinate system in degrees. When saving a region file in ds9, be careful to select coordinates in degrees (sexagesimal may be selected by default in ds9). Currently, acceptable shape of the source region is a simple "circle", and the background region is "circle - circle". The background region has to be within a radius of 8.0 deg from the center coordinates, which can be changed by adding an option, radi_o. See the examples.

Example for the source region file:

 # Region file format: DS9 version 4.1
 global color=green dashlist=8 3 width=1 font="helvetica 10 normal roman" select=1 highlite=1 dash=0 fixed=0 edit=1 move=1 delete=1 include=1 source=1
 fk5
 circle(49.951,41.512,6000")     

Example for the background region file, which is a "ring" surrounding the source region:

 # Region file format: DS9 version 4.1
 global color=green dashlist=8 3 width=1 font="helvetica 10 normal roman" select=1 highlite=1 dash=0 fixed=0 edit=1 move=1 delete=1 include=1 source=1
 fk5
 circle(49.951,41.512,108000")     
 -circle(49.951,41.512,7200")     

Energy-band filter

In mxproduct, multi-band light-curves are generated and stored in multiple extensions in a single output FITS file.

The default energy bands are 2.0–5.95 and 6.0–11.95 keV for GSC, 0.7–1.997 and 2.000–6.997 keV for SSC.

If you want to change the energy bands, you can supply a plain text file that describes your desired (multiple) energy bands. See the options ebandfname_gsc,ebandfname_ssc.

Each line of the file consists of a pair (Minimum, Maximum) of the energy in keV, separated by a single space.

The following is an example for specifying three energy bands, 2–5.95, 6–11.95, and 12–20 keV.

 2.0 5.95
 6.0 11.95
 12.0 20.0  

Output files

mxproduct generates the GSC and/or SSC science products (spectra, spectral response file, and light-curves) in the directory products/ (or, user can specify the name by the command-line option, "outpath") , as well as some auxiliary files in the directory trend/, both in the current directory. The default energy bands are 2.0–5.95 and 6.0–11.95 keV for the GSC, 0.7–1.997 and 2.000–6.997 keV for the SSC. The following is a set of example product filenames for GSC_Low, where the command-line option of object=crab is given. For GSC_Med and SSC_Med, replace g_low with g_med and s_med, respectively.

Event file

crab_g_low.evt

Images

crab_g_low.img
crab_g_low_wmap_src.img
crab_g_low_wmap_bgd.img

Spectra and responses

crab_g_low_src.pi
crab_g_low_bgd.pi
crab_g_low.rsp

Light-curves

crab_g_low.lc

Scancur file (observation condition for the target)

crab_g_low_scancur.fits

Command log

mxproduct.log (created at the path you ran mxproduct)

During the processing, many intermediate files (such as, GTI files, spectrum files for individual cameras) are created in the same products (or user-specified name) directory. They are automatically left after the processing in default, unless cleanup=yes is specified. The diagram in the previous subsection summarizes the directory and file structure.

The following figures show examples of WMAP image of Crab for source and background regions without (default settings) and with the region files. Without region files, the default source and background data are selected by elongation angles from the target in a scan direction and in a direction perpendicular to the scan direction. The generated images are neither exposure-corrected nor background-subtracted.

The generated light-curves are not yet corrected for the effective area. The absolute count rate, especially in the low energy band, is underestimated by ~10%. The light-curves may show some jumps, which might be artificial, not real by the target. The light-curves for Crab are shown below, about 10% less compared to the result by MAXI on-demand process especially below 4 keV.　

Options

object=NAME

Prefix of the filenames of science products. Avoid any of the characters of [-+*/()] and a space for NAME (especially, watch out for the hyphen “-”), which would cause Memory Error while calculating spectrum files, using mathpha in FTOOLS. Default is target.

gscdl=(low or med)

Specify med to use the GSC med-data (Default: low).

skip_gsc=(0(Default) or 1)

If 0 (default), processes all the available GSC data of the relevant mode as specified in gscdl. Otherwise, skips all of them.

skip_ssc=(0 or 1(Default))

If 0, processes all the available SSC data. Otherwise (default), skips all of them.

datapath=PATH

Directory for the locally mounted data files, that is, the path where obs/ exists. Default is ".".

mountdata=(0(Default) or 1)

(Internal use) Uses the locally-mounted whole archive if 1.

outpath=PATH

Directory where output files will be put. Default is "products/".

srcregfile_gsc=FILENAME

Filename of the region file for the source with the GSC in the ds9/fk5 format. Only a simple circle shape is accepted.

bgdregfile_gsc=FILENAME

Same as srcregfile_gsc, but for the GSC background region. Only a simple circle - circle shape is accepted.

srcregfile_ssc=FILENAME

Same as srcregfile_gsc, but for the SSC source region.

bgdregfile_ssc=FILENAME

Same as srcregfile_ssc but for the SSC background region.

ebandfname_gsc=FILENAME

Filename of the energy band for GSC light curves. See the previous subsection Overview for detail of the format.

ebandfname-ssc=FILENAME

Same as the option ebandfname_gsc but for the SSC.

cleanup=(yes or no(Default))

mxproduct generates a number of intermediate files, including GTI files, event files, spectrum files in the directory ./products/ (or user-specified name) during processing. In default, all these files are deleted when mxproduct completes the task or is halted/interrupted (except for the case the process is killed by the KILL signal). They are not deleted if this option is specified to be 1.

Examples

1. The simplest form for the source1 at (RA, DEC)=(350°, −10°).

    mxproduct object=src1 350 -10 2010-01-01 2010-01-31
   

2. Processing the data for the radius of 10 degrees of Crab Nebura, where the MAXI data directory obs/ is mounted in /My/Data/Maxi/.
   

    mxproduct object=crab mountdata=1 datapath=/My/Data/Maxi radi_o=10 83.633083 22.014500 2010-01-01 2010-01-31
   

3. Specifying region files for source and background.

    mxproduct object=crab srcregfile_gsc=src.reg bgdregfile_gsc=bgd.reg 83.633083 22.014500 2010-01-01 2010-01-31
   

4. Specifying energy bands for GSC light-curves in a text file, gsc_eband.list, a directory name for output files, test1/, and start/stop time with hh:mm:ss.

    mxproduct object=crab ebandfname_gsc=gsc_eband.list outpath=test1 83.633083 22.014500 2010-01-01T08:00:00 2010-01-31T20:00:00
   

5. Example of the SSC data processing.

    mxproduct object=crab skip_gsc=1 skip_ssc=0 83.633083 22.014500 2010-01-01 2010-01-31
   

The GSC has 2 data types: gsc_low and gsc_med. Users must choose either of them, and cannot mix them in the data reduction (gsc_low is the default in mxproduct). GSC consists of 12 counters, with the counter ID = 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, b. The recommended energy ranges are 2-20 keV and 2-30 keV for gsc_low and gsc_med, respectively. The SSC has only 1 data type: ssc_med. SSC has 2 cameras, SSC-h and SSC-z. We recommend to use the 0.7-7 keV energy band for SSC.
Width of the spectral bin is 50 eV for GSC, and 3.65 eV for SSC.

2.2.1. Spectral analysis

The spectra and response files generated by mxproduct are in the standard FITS format. You can use your favorite software to analyze them. The following is the standard entry-level procedure with the XANADU/HEAsoft spectral-analysis package XSPEC to view the background-subtracted spectrum.

 xspec

 cpd /xw
 data 1:1 "crab_g_low_src.pi"
 back 1   "crab_g_low_bgd.pi"
 resp 1   "crab_g_low.rsp"
 setplot energy
 ignore bad
  
 iplot ldata
  
 log x on 1
 log y on 1
 label t Crab
 lwidth 5
 rescale x 1 10
 plot