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Top > Suzaku > Analysis > XIS > NTE

XIS Night Earth Background Database and Tools (temporal version)

2006-11-09 by the XIS team

A minor bug was found at one of the script supplied with the 2006-05-30 version. When there is a very small COR-sorted file, the script fails to sum files with mathpha, due to a format difference of the exposure time. The XIS team supplied a revised version of the script and the entire tar file. If you are using 2006-05-30 version, just download and replace with it.

2006-09-04 by the XIS team

The night earth (NTE) data are useful to estimate the non-X-ray background (NXB) of the XIS and perform background subtraction in your analysis, although you have to prepare the CXB component by yourselves. Once all the data are processed with V1.2 processing, the XIS team will create NTE database. Before that, we release NTE data generated based on the V0.7 products1, which covers from 2005 September to 2006 May.

The database consists of simple event files and you can apply any kinds of data selection for them. Associated merged EHK file2, we prepared, will be useful to pickup background data with your criteria. However, we know the XIS background level depends primarily on the cut-off-rigidity (COR) in orbit (Koyama et al. 2006, submitted to PASJ). For the convenience of users, we have also prepared software tools to make COR weighted background spectra.

These database and tools are the initial version, and may have problems or points to be revised. Feedback is always welcome. If you have a problem, please contact Suzaku Help Desk.

[1] Contents of the directory

  1. NTE event file from September 2005 to May 2006 created from V0.7 products
    • (XIS0) ae_xi0_ntebgd_20060530.evt
    • (XIS1) ae_xi1_ntebgd_20060530.evt
    • (XIS2) ae_xi2_ntebgd_20060530.evt
    • (XIS3) ae_xi3_ntebgd_20060530.evt
    *) Extraction criteria is given below.
  2. EHK file for the NTE event files
    • ae_xis_ntebgd_20060530.ehk
  3. Software tool to make COR sorted spectra from a event file
  4. Software tool to make COR weighted background spectra
    *) (4) needs output spectra created with (3).
  5. README files
    • README.txt : (English)

[2] Criteria to extract NTE event file

We made the NTE event file by the following process.
  1. pickup V0.7 products of which XIS mode was "n000" or "n001".
  2. perform cleansis
    (parameters: cellsize=5 logprob=-5.3 bthresh=3 phamin=0 phamax=4095)
  3. extract NTE data
    DYE_ELV>100 && ELV<-5
    (Region outside of the cal mask)
  4. exclude "Important XIS event"
    1.772928000000000E+08 1.785969000000000E+08
    1.785978600000000E+08 1.791246000000000E+08
    1.791638400000000E+08 1.817291400000000E+08
    1.817360400000000E+08 1.828230000000000E+08
    1.828299000000000E+08 1.832436000000000E+08
    1.832454000000000E+08 1.832496000000000E+08
    1.832595000000000E+08 1.859848800000000E+08
    1.860294600000000E+08 1.863683400000000E+08
    1.863750600000000E+08 1.871670000000000E+08
    1.871688600000000E+08 1.897550400000000E+08
    1.897617600000000E+08 1.908675000000000E+08
    1.910595000000000E+08 1.921990200000000E+08
    1.922253000000000E+08 1.931622000000000E+08
    1.931628000000000E+08 1.934994600000000E+08
    1.935061200000000E+08 1.952820600000000E+08
    1.952877000000000E+08 1.957039800000000E+08
    1.957072200000000E+08 1.969780800000000E+08
    1.969893600000000E+08 3.0E+08
  5. exclude time when count rate was unexpectedly higher or lower.
    1.772928000000000E+08 1.8342E+08
    1.8362E+08 1.881E+08
    1.882E+08 3e8
    1.76E+08 179769582.923671 179770142.923671 179844782.923671 179845182.923671 180448782.923671 180449822.923671 180455022.923671 180455422.923671 180535822.923671 180536222.923671 180541262.923671 180541662.923671 180869422.923671 180869822.923671 187214165 187214565 187300405 187300805 188050325 188050725 188067605 188068005 188240085 188240645 188246005 188246565 189062485 189062885 193577103 193577663 193657743 193658143 3.0E+08
[3] How to make COR weighted background spectra as mentioned above

The non-X-ray background level of XIS primarily depends on the COR. The NTE background data of the same COR value as the source observation would provide a good estimation of the background level. For this purpose, COR sorted background spectra is useful. We have prepared a software tool to make such sorted spectra with COR values at one time.

Considering the case when we make a spectrum of a source observation of many orbital cycles, we need to sum up the COR sorted "background" spectra with appropriate weights to get the background spectrum to be subtracted. We have also prepared a software tool to make COR weighted background spectra appropriate for a given source observation.

Here is a rough instruction how to use these two tools.

  1. Make COR sorted NTE spectra from the NTE database event files.
    > ls
    ae_xi0_ntebgd_20060530.evt   ae_xi3_ntebgd_20060530.evt
    ae_xi1_ntebgd_20060530.evt   ae_xis_ntebgd_20060530.ehk
    ae_xi2_ntebgd_20060530.evt   box.reg
    > -i ae_xi0_ntebgd_20060530.evt -d . 
      -e ae_xis_ntebgd_20060530.ehk -ed . -s 0 -o nte -r box.reg
  2. Make COR sorted spectra of the source observation, using the same tool
    *) Note that this process is needed only for picking up the COR distribution during source observation.
    Here is an example for the OBSID=100019010 observation.
    The directory structure and files relating XIS is as follows;
                ae100019010xi{0,1,2,3}_0_{3x3, 5x5}n000a_cl.evt.gz
    Link them to the current directory.
    > ls
    ae100019010xi{0,1,2,3}_0_{3x3, 5x5}n000a_cl.evt.gz
    Add 3x3 and 5x5 evt files into ae100019010xi{0,1,2,3}_cl.evt
    with XSELECT.
    > -i ae100019010xi0_cl.evt
      -d . -e ae100019010.ehk.gz -ed . -s 0 -o src -r box.reg
    About arguments
    -i ae_x0.evt :  event file name
    -d .         :  directory under which the event file exists 
    -e           :  ehk file name 
    -ed .        :  directory under which the ehk file exists
    -s 0         :  XIS id (0,1,2,3) 
    -o src       :  prefix for the output products name (object name etc ).
    -r box.reg   :  region file name (DET coordinate)
    About output files
    src_x0_cor_??_**.pi  :  spectra of ??
  3. Make COR weighted NTE bacground spectra appropriate for the source observation
    > ls
    ae100019010.ehk.gz		      box.reg
    ae100019010xi0_0_5x5n000a_cl.evt.gz   nte_org/
    ae100019010xi1_0_5x5n001b_cl.evt.gz   src_x0_cor_00_04.pi
    ae100019010xi2_0_5x5n000a_cl.evt.gz   src_x0_cor_04_05.pi
    ae100019010xi3_0_5x5n000a_cl.evt.gz   src_x0_cor_05_06.pi
    ae100019010xi0_0_3x3n000a_cl.evt.gz   src_x0_cor_06_07.pi
    ae100019010xi1_0_3x3n001b_cl.evt.gz   src_x0_cor_07_08.pi   
    ae100019010xi2_0_3x3n000a_cl.evt.gz   src_x0_cor_08_09.pi   
    ae100019010xi3_0_3x3n000a_cl.evt.gz   src_x0_cor_09_10.pi   
    ae100019010xi0_cl.evt                 src_x0_cor_10_11.pi
    ae100019010xi1_cl.evt                 src_x0_cor_11_12.pi
    ae100019010xi2_cl.evt                 src_x0_cor_12_13.pi
    ae100019010xi3_cl.evt                 src_x0_cor_13_99.pi
    > ls nte_org/
    ae_xi0_ntebgd_20060530.evt   nte_x0_cor_00_04.pi  nte_x0_cor_09_10.pi
    ae_xi1_ntebgd_20060530.evt   nte_x0_cor_04_05.pi  nte_x0_cor_10_11.pi
    ae_xi2_ntebgd_20060530.evt   nte_x0_cor_05_06.pi  nte_x0_cor_11_12.pi
    ae_xi3_ntebgd_20060530.evt   nte_x0_cor_06_07.pi  nte_x0_cor_12_13.pi
    ae_xis_ntebgd_20060530.ehk   nte_x0_cor_07_08.pi  nte_x0_cor_13_99.pi
    box.reg                      nte_x0_cor_08_09.pi
    > -s 0 -t src -td . -b nte -bd nte_org/
    About arguments
    -s 0   : XIS id (0,1,2,3)
    -t src : The prefix word which you input as the argument of "-o" in 2)
             (The script pick up the target spectra by this word.) 
    -td .  : Directory under which the target spectra exist.
    -b nte : The prefix word which you input as the argument of "-o" in 1)
             (The script pick up the NTE spectra by this word.) 
    -bd nte_org/ : Directory under which the NTE spectra exist.
    About output files
    corweighted_nte_x0.pi  : COR weighted NTE spectrum (unit: counts)
    corweighted_nte_x0.log : log file
    tmp/                   : temporary directory


1: V0.7 processing is an internal processing applied to the Suzaku data obtained during the SWG phase. See Suzaku Memo 2006-21 for the details.

2: EHK means `extended HK'. It is a collection of elevation, cut-off rigidity, etc. as a function of time. In the official Suzaku processing, MKF files contain all the information written in EHK files, and are used instead.

ISAS/JAXA Department of High Energy Astrophysics

Last Modified: Wednesday, 22-Aug-2007 15:10:15 JST