HXD-GSO Background for V2.x and V3.0 Data


2012-02-01
New GSO background corresponding to the new "hxdpi"
(heasoft-6.9 and later).

HXD-GSO non X-ray background (NXB) files for the processing version after v2.5.16.28 are now available from the following location:

Observation date Directory METHOD * METHODV ** gptfile_date
2005-08-17 to 2011-11-03 gsonxb_ver2.5 LCFIT (bgd_d) 2.5ver0912-64 20100323
after 2011-11-03 gsonxb_ver2.6 LCFIT (bgd_d) 2.6ver1110-64 20110819
*: FITS header keyword to distinguish the background modeling methods.
**: FITS header keyword to distinguish the minor revisions of the same model.

You should choose ver2.5 or ver2.6, according to the GSO energy calibration file ae_hxd_gsogpt_20100323.fits or ae_hxd_gsogpt_20110819.fits used in the processing. The pipe-line processing uses the ae_hxd_gsogpt_20100323.fits before 2011 Nov 3 data and ae_hxd_gsogpt_20110819.fits after 2011 Nov. 3 data. You can check which gsogpt file is used for your data and background in the processing by the head keyword "GSOGPT_F".

By default, users do not have to reprocess the GSO data after 2010 March 1, but the pipeline processing data (archival data) before 2010 March 1 must be reprocessed, since the old GSO gain correction method was applied. Since the difference between the analysis results between ae_hxd_gsogpt_20100323.fits and ae_hxd_gsogpt_20110819.fits is not so large. Only for the bright sources (above 100 mCrab at the GSO band), we will recommend to reprocess the data from 2010 Mar 1 to 2011 Nov 3. When you once reprocess the data with ae_hxd_gsogpt_20110819.fits, you should use the background ver2.6. This is also the case when you use the tool "aepipeline" which automatically choose the newest calibration file ae_hxd_gsogpt_20110819.fits.

This directory is divided into subdirectories by month. For example, background files for observations carried out in 2006 August can be found in the subdirectory 2006_08. Within these monthly directories, individual background files are listed alphabetically. Note these files are named using the sequence number, e.g., aeNNNNNNNNN_hxd_gsobgd.evt.gz.
Currently, it takes around one month to create the GSO background after the actual observation date. New files for the latest sequences will be uploaded immediately when prepared.

These files should only be used with data processed with the Suzaku Software V16 (Heasoft V6.9) or later.

General Notes for GSO-BGD:

  1. The event rate of BGD event file is not 10 times as that of PIN-BGD, and thus you should not correct the exposure.
  2. You should reprocess the second FITS files of your own data before subtracting the GSO background. See the page of "seven steps for HXD analysis" or the ABC guide.
  3. Since the GSO background is created in 64 bins as listed below, you should also perform the binning of observation data by use of gso_grp64.dat.
    
    grppha> group gso_grp64.dat
    
    
  4. You should correct the dead time of the GSO-BGD spectral file, as well as the observation spectral file.
  5. The BGD event file does not include the CXB. However, the CXB is less than 0.1% of the total background rate, and thus it is negligible.
  6. The accuracy of model is expected to reach as good as <2 % of the averaged background. Observers are strongly recommended to verify the reliability of background, by comparing the model spectrum and light curve with the "earth occultated data" which can be obtained on the condition of "ELV<-5". Due to the change of intruementa set-up, the GSO BGD rate is sometimes different from the model significantly in the period of 2006/3/19 -- 2006/5/29. Please check the HXD operation log.
	binning of both observation and background spectra by "grppha": 

        group 0 24 25 25 26 2 27 27 1 28 28 1 29 30 2 31 31 1
        group 32 33 2 34 35 2 36 36 1 37 38 2 39 40 2 41 42 2
        group 43 44 2 45 46 2 47 49 3 50 51 2 52 54 3 55 56 2
        group 57 59 3 60 62 3 63 65 3 66 68 3 69 71 3 72 75 4
        group 76 79 4 80 83 4 84 87 4 88 91 4 92 95 4 96 100 5
        group 101 105 5 106 110 5 111 116 6 117 121 5
        group 122 127 6 128 134 7 135 140 6 141 147 7
        group 148 154 7 155 162 8 163 170 8 171 178 8
        group 179 187 9 188 196 9 197 206 10 207 216 10
        group 217 227 11 228 238 11 239 249 11 250 262 13
        group 263 274 12 275 288 14 289 302 14 303 317 15
        group 318 332 15 333 349 17 350 366 17 367 384 18
        group 385 403 19 404 422 19 423 443 21 444 465 22
        group 466 487 22 488 511 24

2008-05-21
Minor revision of GSO background.

A minor problem is found in the header keyword (MJDREF) of GSO background. The HXD team has corrected it to the appropriate keywords (MJDREFI and MJDREFF), and also updated the METHODV keyword to "2.0ver0804". Old files are moved into the "old20080521" directory.


2008-01-08

The status of current HXD-GSO background model for v2 products is described as a suzakumemo (2008-01).


HXD-GSO non X-ray background (NXB) files for v2.x data are now available from the following location:

Observation date Directory METHOD * METHODV **
After 2005-08-17 gsonxb_ver2.0 LCFIT (bgd_d) 2.0ver0804
*: FITS header keyword to distinguish the background modeling methods.
**: FITS header keyword to distinguish the minor revisions of the same model.

This directory is divided into subdirectories by month. For example, background files for observations carried out in 2006 August can be found in the subdirectory 2006_08. Within these monthly directories, individual background files are listed alphabetically. Note these files are named using the sequence number, e.g., aeNNNNNNNNN_hxd_gsobgd.evt.gz.
Currently, it takes around one month to create the GSO background after the actual observation date. New files for the latest sequences will be uploaded immediately when prepared.

These files should only be used with version 2.x processed data, and vice versa.

General Notes for GSO-BGD:

  1. The event rate of BGD event file is not 10 times as that of PIN-BGD, and thus you should not correct the exposure.
  2. You should reprocess the second FITS files of your own data before subtracting the GSO background. See the page of "seven steps for HXD analysis" or the ABC guide.
  3. Since the GSO background is created in 32 bins as listed below, you should also perform the binning of observation data by use of gso_grp.dat.
    
    grppha> group gso_grp.dat
    
    
  4. You should correct the dead time of the GSO-BGD spectral file, as well as the observation spectral file.
  5. The BGD event file does not include the CXB. However, the CXB is less than 0.1% of the total background rate, and thus it is negligible.
  6. The accuracy of model is expected to reach as good as <2 % of the averaged background. Observers are strongly recommended to verify the reliability of background, by comparing the model spectrum and light curve with the "earth occultated data" which can be obtained on the condition of "ELV<-5". Due to the change of intruementa set-up, the GSO BGD rate is sometimes different from the model significantly in the period of 2006/3/19 -- 2006/5/29. Please check the HXD operation log.
  7. Correct gain calibration is important to estimate the background accurately, but it has been found that the GSO gain correction by the current "hxdpi" show small discontinuity around 2006-03-03 -- 2006-05-09; energy scale of reprocessed data becomes different by several % from that of response and background. HXD team is now developing the new version "hxdpi" so as to resolve this problem.
	binning of both observation and background spectra by "grppha": 

	group 0 24 25 25 26 2 27 28 2 29 31 3 32 35 4 36 38 3 
	group 39 42 4 43 46 4 47 51 5 52 56 5 57 62 6 
	group 63 68 6 69 75 7 76 83 8 84 91 8 92 100 9 
	group 101 110 10 111 121 11 122 134 13 135 147 13 148 162 15 
	group 163 178 16 179 196 18 197 216 20 217 238 22 239 262 24 
	group 263 288 26 289 317 29 318 349 32 350 384 35 385 422 38 
	group 423 465 43 466 511 46

ISAS/JAXA Department of High Energy Astrophysics
Last Modified: Wednesday, 18-Apr-2012 14:21:25 JST