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ASCA Calibration Database


Files and information regarding the ASCA calibrations are kept in the HEASARC Calibration Database . On this page we highlight some calibration files and articles that are most commonly required for ASCA analysis.

The ASCA GIS

  • Background files have been created from a superposition of 15 blank sky fields observed during the ASCA PV phase (May 93 - Mar 94). The files are for various magnetic rigidity values and are having *all* in their name (each for the two detectors) includes all the events, regardless of the magnetic cut-off rigidity (COR) values. Since the GIS internal background increases as COR decreases, other files are sorted by COR values (in units of GeV/c). There are directories containing sky+particle background, night earth (particle) and sky+particle background when the spread discriminator was turned off during the early mission PV phase (up to 1993, May 28; 80015000, Hydra A).

    In the article Background characteristics of the GIS by Kubo et al. a description of the GIS background is described. This article appeared in Volume 2 of the asca newsletter AscaNews.

    It was pointed out that moderately bright point sources in these GIS background files are not completely averaged out and may affect BGD subtraction results. Please refer to Warning about GIS BGD files.

  • The latest Response Matrices are available from the ASCA calibration database. The detector response is split up into RMF and ARF files. The RMF describes the elements of the response that do not dependent on the focal plane position. There are two RMF files, one for each telescope:

  • The ARF takes into account the telescope response, which depends on the source location, extent and extraction region. The ftool ascaarf should be used to generate an ARF for each spectrum accumulated. For convenience combined ARF+RMF=RSP files are given for the standard pointing positions.

    THESE FILES SHOULD ONLY BE USED FOR SIMULATIONS.

  • Other GIS calibration files are also available from here

The ASCA SIS

  • Background files for both SIS detectors are available from 3 deep field observations without any obvious sources and with a total exposure of about 120 ks. The events were cleaned using the "select mkf" command in XSELECT (with ELV_MIN > 20 and SAA = 0). Hot and flickering pixels were removed using the "sisclean" command in XSELECT (sisclean method 2, with cell size 5, log probability -5.24, background level 3). Any spurious events which remained were removed by manual cleaning based on the light curve (i.e. excluding spikes and drop- outs). The background rate is a weak function of the lower limit of magnetic cut-off rigidity and files have been generated for different rigidity ranges. These files contain both the particle and sky backgrounds. The article Initial Report on the SIS Internal Background in Volume 2 of the asca newsletter, AscaNews, describes the SIS background and a model for the particle background. This is by Keith Gendrau, who has also written several other interesting calibration reports.

  • The SIS response matrices should be generated with the FTOOL sisrmg for each spectral file extracted; this is because the response is dependent on the time of observation, the detector coordinates of the soruce, and on the observing mode. The latest calibration files that are used by sisrmg (including sisph2pi_110397.fits, which is also used by sispi) are distributed with FTOOLS in the refdata area, but they can also be found here. Some of the old SIS RMF and RSP files (i.e. response matrices which include the ARF or telescope response) are available for the standard 1-CCD mode position. They should only be used for quick-look purposes and simulations:

  • Other SIS calibration files are also available from here


This file was last modified on Monday, 23-Jul-2001 15:46:38 EDT


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This file was last modified on Monday, 23-Jul-2001 15:46:38 EDT

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