SPEX User's Manual - SRON

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108 Response matrices practical problems. For example, the fitsio-package allows a maximum of 1000 extensions. The documentation of fitsio says that this number can be increased, but that the access time to later extensions in the file may become very long. In principle we want to allow for data sets with an unlimited number of response components. For example, when a cluster spectrum is analysed in 4 quadrants and 10 radial annuli, one might want to extract the spectrum in 40 detector regions and model the spectrum in 40 sky sectors, resulting in principle in at least 1600 response components (this may be more if the response for each sky sector and detector region has more components). Therefore I propose to use only three additional and mandatory extensions. The first extension is a binary table with 4 columns and contains for each component the number of data channels, model energy bins, sky sector number and detector region number (see table 5.8). The second extension is a binary table with 5 columns and contains for each model energy bin for each component the lower model energy bin boundary (keV), the upper model energy bin boundary (keV), the starting data channel, end data channel and total number of data channels for the response group (see table 5.9). The third extension is a binary table with 2 columns and contains for each data channel, for each model energy bin for each component the value of the response at the bin center and its derivative with respect to energy (see table 5.10). SI units are mandatory (i.e. m 2 for the response, m 2 keV −1 for the response derivative). Table 5.8: First extension to the response file keyword EXTNAME (=RESP INDEX) NAXIS1 = 16 NAXIS2 = NSECTOR = NREGION = NCOMP = TFIELDS = 4 TTYPE1 = ’NCHAN’ TTYPE2 = ’NEG’ TTYPE3 = ’SECTOR’ TTYPE4 = ’REGION’ description Contains the basic indices for the components in the form of a binary table There are 16 bytes in one row This number corresponds to the total number of components (the number of rows in the table) This 4-byte integer is the number of sky sectors used. This 4-byte integer is the number of detector regions used. This 4-byte integer is the totalnumber of response components used (should be equal to NAXIS2). The table has 4 columns; all columns are written as 4-byte integers (TFORM=’1J’) First column contains the number of data channels for each component. Not necessarily the same for all components, but it must agree with the number of data channels as present in the corresponding spectrum file. Second column contains the number of model energy grid bins for each component. Not necessarily the same for all components. Third column contains the sky sector number as defined by the user for this component. In case of simple spectra, this number should be 1. Fourth column contains the detector region number as defined by the user for this component. In case of simple spectra, this number should be 1.
5.7 Proposed file formats 109 Table 5.9: Second extension to the response file keyword EXTNAME (=RESP COMP) NAXIS1 = 20 NAXIS2 = TFIELDS = 5 TTYPE1 = ’EG1’ TTYPE2 = ’EG2’ TTYPE3 = ’IC1’ TTYPE4 = ’IC2’ TTYPE5 = ’NC’ description Binary table with for each row relevant index information for a single energy of a component; stored sequentially, starting at the lowest component and within each component at the lowest energy. There are 20 bytes in one row This number must be the sum of the number of model energy bins added for all components (the number of rows in the table). The table has 5 columns The lower energy (keV) as a 4-byte real of the relevant model energy bin The upper energy (keV) as a 4-byte real of the relevant model energy bin The lowest data channel number (as a 4-byte integer) for which the response at this model energy bin will be given. The response for all data channels below IC1 is zero. Note that IC1 should be at least 1 (i.e. start counting at channel 1!). The highest data channel number (as a 4-byte integer) for which the response at this model energy bin will be given. The response for all data channels above IC2 is zero. The total number of non-zero response elements for this model energy bin (as a 4-byte integer). NC is redundant, and should equal IC2-IC1+1, but it is convenient to have directly available in order to allocate memory for the response group. Any other information that is not needed for the spectral analysis may be put into additional file extensions, but will be ignored by the spectral analysis program. Finally I note that the proposed response format is used as the standard format by version 2.0 of the <strong>SPEX</strong> spectral analysis package. 5.7.2 Proposed spectral file format There exists also a standard OGIP FITS-type format for spectra. As for the OGIP response file format, this format has a few redundant parameters and not absolutely necessary options. There is some information that is absolutely necessary to have. In the first place the net source count rate S i (counts/s) and its statistical uncertainty ∆S i (counts/s) are needed. These quantities are used e.g. in a classical χ 2 -minimization procedure during spectral fitting. In some cases the count rate may be rather low; for example, in a thermal plasma model at high energies the source flux is low, resulting in only a few counts per data channel. In such cases it is often desirable to use different statistics for the spectral fitting, for example maximum likelihood fitting. Such methods are often based upon the number of counts; in particular the difference between Poissonian and Gaussian statistics might be taken into account. In order to allow for these situations, also the exposure time t i per
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SPEX User’s Manual Jelle Kaastra
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4 CONTENTS 2.29 System . . . . . .
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6 CONTENTS 5.8.3 ASCA SIS0 . . . .
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8 Introduction 1.2.2 Sky sectors Fi
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10 Introduction
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12 Syntax overview Table 2.2: Abund
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14 Syntax overview tcl: the continu
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16 Syntax overview Examples calc -
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18 Syntax overview by averaging the
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20 Syntax overview dem gene #i1 #i2
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22 Syntax overview distance om #r -
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24 Syntax overview Examples elim 0.
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26 Syntax overview This is strictly
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28 Syntax overview Currently these
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30 Syntax overview Syntax The follo
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32 Syntax overview status, range an
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34 Syntax overview par write mypar
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36 Syntax overview plot box col #i
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38 Syntax overview plot type data -
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40 Syntax overview 2.26 Simulate: S
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42 Syntax overview step axis 2 par
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44 Syntax overview Examples use 100
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46 Syntax overview width. On top of
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48 Syntax overview
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50 Spectral Models acronym pow delt
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52 Spectral Models Finally, we have
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54 Spectral Models where Q is the l
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56 Spectral Models 3. set=3: for R
Page 58 and 59: 58 Spectral Models 3.14 Hot: collis
Page 60 and 61: 60 Spectral Models can be transform
Page 62 and 63: 62 Spectral Models The emission mea
Page 64 and 65: 64 Spectral Models 3.23 Refl: Refle
Page 66 and 67: 66 Spectral Models • type=3: b 1
Page 68 and 69: 68 Spectral Models 4.8, 4.9, 5.0 wi
Page 70 and 71: 70 More about plotting Table 4.1: A
Page 72 and 73: 72 More about plotting 4.4 Plot lin
Page 74 and 75: 74 More about plotting Table 4.2: A
Page 76 and 77: 76 More about plotting 4.6 Plot cap
Page 78 and 79: 78 More about plotting 4.8 Plot axi
Page 80 and 81: 80 More about plotting bin cou cs k
Page 82 and 83: 82 More about plotting
Page 84 and 85: 84 Response matrices models. Since
Page 86 and 87: 86 Response matrices Table 5.1: Wei
Page 88 and 89: 88 Response matrices Table 5.2: Sca
Page 90 and 91: 90 Response matrices since the larg
Page 92 and 93: 92 Response matrices Figure 5.1: Di
Page 94 and 95: 94 Response matrices for the Cauchy
Page 96 and 97: 96 Response matrices bin j of this
Page 98 and 99: 98 Response matrices The approximat
Page 100 and 101: 100 Response matrices particular bi
Page 102 and 103: 102 Response matrices reduced by ab
Page 104 and 105: 104 Response matrices where as befo
Page 106 and 107: 106 Response matrices 5. Determine
Page 110 and 111: 110 Response matrices Table 5.10: T
Page 112 and 113: 112 Response matrices Table 5.11: F
Page 114 and 115: 114 Response matrices Figure 5.7: B
Page 116 and 117: 116 Response matrices Table 5.15: R
Page 118 and 119: 118 Response matrices
Page 120 and 121: 120 Installation and testing
Page 122 and 123: 122 Acknowledgements
Page 124 and 125: 124 BIBLIOGRAPHY [2003] Peterson, J
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