SPEX Reference manual (PDF) - SRON

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26 Syntax overview There is yet another option to try for spectral fitting with low count rate statistics and that is maximum likelyhood fitting. It can be shown that a good alternative to χ 2 in that limit is C = 2 n∑ s i −N i +N i ln(N i /s i ). (2.2) i=1 This is strictly valid in the limit of Poissonian statistics. If you have a background subtracted, take care that the subtracted number of background counts is properly stored in the spectral data file, so that raw number of counts can be reconstructed. Syntax The following syntax rules apply: fit - Execute a spectral fit to the data. fit print #i - Printing the intermediate results during the fitting to the screen for every n-th step, with n=#i (most useful for n = 1). Default value: 0 which implies no printing of intermediate steps. fit iter #i - Stop the fitting process after #i iterations, regardless convergence or not. This is useful to get a first impression for very cpu-intensive models. To return to the default stop criterion, type fit iter 0. fit weight model - Use the current spectral model as a basis for the statistical weight in all subsequent spectral fitting. fit weight data - Use the errors in the spectral data file as a basis for the statistical weight in all subsequent spectral fitting. This is the default at the start of <strong>SPEX</strong>. fit method classical-UsetheclassicalLevenberg-Marquardtminimisationofχ 2 asthefittingmethod. This is the default at start-up. fit method cstat - Use the C-statistics instead of χ 2 for the minimisation. Examples fit - Performs a spectral fit. At the end the list of best fit parameters is printed, and if there is a plot this will be updated. fit print 1 - If followedby the abovefit command, the intermediate fit results areprinted to the screen, and the plot of spectrum, model or residuals is updated (provided a plot is selected). fit iter 10 - Stop the after 10 iterations or earlier if convergence is reached before ten iterations are completed. fit iter 0 - Stop fitting only after full convergence (default). fit weight model - Instead of using the data for the statistical weights in the fit, use the current model. fit weight data - Use the data instead for the statistical weights in the fit. fit method cstat - Switch from χ 2 to C-statistics. fit method clas - Switch back to χ 2 statistics. 2.13 Ibal: set type of ionisation balance Overview For the plasma models, different ionisation balance calculations are possible. Currently, the default set is Arnaud & Rothenflug ([1985]) for H, He, C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca and Ni, with Arnaud & Raymond ([1992]) for Fe. Table 2.5 lists the possible options. Syntax The following syntax rules apply:
2.14 Ignore: ignoring part of the spectrum 27 Table 2.5: Ionisation balance modes Abbrevation <strong>Reference</strong> reset default (=ar92) ar85 Arnaud & Rothenflug ([1985]) ar92 Arnaud & Raymond ([1992]) for Fe, Arnaud & Rothenflug ([1985]) for the other elements bryans09 Bryans et al. ([2009]) ibal #a - Set the ionisation balance to set #a with #a in the table above. Examples ibal reset - Take the standard ionisation balance ibal ar85 - Take the Arnaud & Rothenflug ionisation balance 2.14 Ignore: ignoring part of the spectrum Overview If one wants to ignore part of a data set in fitting the input model, as well as in plotting this command should be used. The spectral range one wants to ignore can be specified as a range in data channels or a range in wavelength or energy. Note that the first number in the range must always be smaller or equal to the second number given. If multiple instruments are used, one must specify the instrument as well. If the data set contains multiple regions, one must specify the region as well. So per instrument/region one needs to specify which range to ignore. The standard unit chosen for the range of data to ignore is data channels. To undo ignore, see the use command (see section 2.30). The range to be ignored can be specified either as a channel range (no units required) or in either any of the following units: keV, eV, Rydberg, Joule, Hertz, Å, nanometer, with the following abbrevations: kev, ev, ryd, j, hz, ang, nm. Syntax The following syntax rules apply: ignore [instrument #i1] [region #i2] #r - Ignore a certain range #r given in data channels of instrument #i1 and region #i2. The instrument and region need to be specified if there are more than 1 data sets in one instrument data set or if there are more than 1 data set from different instruments. ignore [instrument #i1] [region #i2] #r unit #a - Same as the above, but now one also specifies the unites #a in which the range #r of data points to be ignored are given. The units can be either Å(ang) or (k)eV. Examples ignore 1000:1500 - Ignores data channels 1000 till 1500. ignore region 1 1000:1500 - Ignore data channels 1000 till 1500 for region 1. ignore instrument 1 region 1 1000:1500 - Ignores the data channels 1000 till 1500 of region 1 from the first instrument. ignore instrument 1 region 1 1:8 unit ang - Same as the above example, but now the range is specified in units of Å instead of in data channels.
Page 1: SPEX Reference Manual Jelle Kaastra
Page 4 and 5: 4 CONTENTS 2.29 System . . . . . .
Page 6 and 7: 6 CONTENTS 6.6 Rgsvprof . . . . . .
Page 8 and 9: 8 Introduction 1.2.2 Sky sectors Fi
Page 10 and 11: 10 Introduction
Page 12 and 13: 12 Syntax overview Table 2.2: Abund
Page 14 and 15: 14 Syntax overview tcl: the continu
Page 16 and 17: 16 Syntax overview Examples calc -
Page 18 and 19: 18 Syntax overview data delete inst
Page 20 and 21: 20 Syntax overview dem mult #i - Do
Page 22 and 23: 22 Syntax overview distance show -
Page 24 and 25: 24 Syntax overview Examples elim 0.
Page 28 and 29: 28 Syntax overview ignore 1:8 unit
Page 30 and 31: 30 Syntax overview written to this
Page 32 and 33: 32 Syntax overview eV, keV, Å, as
Page 34 and 35: 34 Syntax overview (Z = 7), ... Ni
Page 36 and 37: 36 Syntax overview plot view x1 #r
Page 38 and 39: 38 Syntax overview plot model lw #i
Page 40 and 41: 40 Syntax overview 2.25 Shiftplot:
Page 42 and 43: 42 Syntax overview 2.27 Step: Grid
Page 44 and 45: 44 Syntax overview system exe #a -
Page 46 and 47: 46 Syntax overview Update: several
Page 48 and 49: 48 Syntax overview Also the totals
Page 50 and 51: 50 Spectral Models Table 3.1: Avail
Page 52 and 53: 52 Spectral Models nr name chemical
Page 54 and 55: 54 Spectral Models (cf. Rybicky & L
Page 56 and 57: 56 Spectral Models 3.6.5 Abundances
Page 58 and 59: 58 Spectral Models 3.8 dabs: dust a
Page 60 and 61: 60 Spectral Models 3.11 Dem: Differ
Page 62 and 63: 62 Spectral Models • ... • last
Page 64 and 65: 64 Spectral Models f9 - Transmissio
Page 66 and 67: 66 Spectral Models 3.22 Neij: Non-E
Page 68 and 69: 68 Spectral Models Warning: By defa
Page 70 and 71: 70 Spectral Models seeing equal con
Page 72 and 73: 72 Spectral Models • type=4: b 1
Page 74 and 75: 74 Spectral Models v - Velocity bro
Page 76 and 77:
76 Spectral Models For more informa
Page 78 and 79:
78 More about spectral models Slab
Page 80 and 81:
80 More about spectral models depth
Page 82 and 83:
82 More about spectral models grid
Page 84 and 85:
84 More about spectral models The e
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86 More about plotting Table 5.1: A
Page 88 and 89:
88 More about plotting 5.5 Plot tex
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90 More about plotting Table 5.4: S
Page 92 and 93:
92 More about plotting Table 5.5: x
Page 94 and 95:
94 More about plotting the plot wil
Page 96 and 97:
96 More about plotting
Page 98 and 99:
98 Auxilary programs Property Spect
Page 100 and 101:
100 Auxilary programs Property Resp
Page 102 and 103:
102 Auxilary programs 15. Optional:
Page 104 and 105:
104 Auxilary programs 6.3 RGS fluxc
Page 106 and 107:
106 Auxilary programs This redistri
Page 108 and 109:
108 Auxilary programs 6.6.1 Theory
Page 110 and 111:
110 Response matrices models. Since
Page 112 and 113:
112 Response matrices Table 7.1: We
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114 Response matrices Table 7.2: Sc
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116 Response matrices since the lar
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118 Response matrices Figure 7.1: D
Page 120 and 121:
120 Response matrices Figure 7.3: R
Page 122 and 123:
122 Response matrices 7.4 Model bin
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124 Response matrices In this secti
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126 Response matrices The resulting
Page 128 and 129:
128 Response matrices where w 1 and
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130 Response matrices spectrumextra
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132 Response matrices may be helpfu
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134 Response matrices 1. The OGIP r
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136 Response matrices Table 7.9: Se
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138 Response matrices could be the
Page 140 and 141:
140 Response matrices Table 7.13: R
Page 142 and 143:
142 Response matrices Figure 7.8: B
Page 144 and 145:
144 Response matrices Figure 7.9: B
Page 146 and 147:
146 Installation and testing
Page 148 and 149:
148 Acknowledgements
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150 BIBLIOGRAPHY [1989] Kaastra, J.
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