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ii_light

For every PIF found in the Science Window, ii_light extracts simultaneously a lightcurve for each source and one light curve for background in all specified energy bands. Dead pixel, data gaps, off-axis correction, energy low threshold and illumination factors are taken into account.

The method used is a fit of hyperplane through the cloud of points formed by the number of counts versus PIF fraction for every source. In the case of one source this is just a linear regression. The intercept gives the background, while the slope gives the flux of the source in one fully illuminated pixel. Normalization is a number of counts in a perfect detector if source is on axis (half of all detector pixels illuminated).

There are two methods to extract the flux for one source:
1. the source flux is extracted considering the source alone.
2. the source flux is extracted taking into account that other sources are in the FOV.
For a faint source in the PCFOV it is important to take into account all bright (typically larger than 0.1 Crab) sources in the entire FOV, whereas to analyse a faint source in the FCFOV it is necessary to consider only bright sources in the PCFOV.

The sources that need to be considered simultaneously for the lightcurve extraction are the ``essential sources'' (the DOL to the list is stored in source_selectDol parameter). The list however should include the lower possible number of sources (defined through the maxessential parameter). This is due to the fact that extracting simultaneously the flux of many (N) sources takes a longer (of order ) computation time than extracting a source alone.

Care has been taken so that the output structure is compatible with HEASARC tools.
There are no limits on the size of time bin (up to 0.1s), and number of energy bands.

ii_light is not the official lightcurve extraction tool and should be used mainly to check relative variability of bright sources within a given Science Window, rather than for a long term absolute flux estimate. An extended comparison between the official lightcurve extraction tool (ii_lc_extract) and ii_light can be found in Grinberg et al. 2011 [15]

Table 28: ii_light parameters.
   
Name Type Description
inSwg string DOL of the input Observation Group.

default: `` ''

     
outSwg string DOL of the output Observation Group

default: `` ''

     
outLC string Dol of the light curves file

default: `` ''

     
context string DOL of the context where we can find low threshold

default: `` ''

     
GTIname string Name of the GTI to be applied

default: `` ''

     
select string Event selection condition

default: `` ''

     
pifDOL string Dol of the PIF (or of the index of PIF)

default: `` ''

     
deadDOL string Dol of the ISGR-DEAD-SCP"

default: `` ''

     
corrDol string DOL of the isgri off-axis corrections

default: `` ''

     
backDol string DOL of the background maps

default: `` ''

     
delta_t real Time bin in seconds.

possible values: 0.1 - 10000

default: 100

     
num_e integer Number of energy channels

possible values: 1 - 10

default: 2

     
e_min string List of low energy boundaries

default: ``15 40''

     
e_max string List of high energy boundaries

default: ``40 300''

     
onlydet boolean Do only detector light curve?

default: NO

     
idxSwitch string DOL of the index of pixels switches list.

default: `` ''

     
idxNoise string DOL of the index of noisy pixels

default: `` ''

     
evttype integer Type of data 0=ISGRI; comprised between 0 and 5

default: 0

     
source_selectDol string DOL containing column NAME of essential sources

default: `` ''

     
maxessential integer Max number of essential sources (between 1 and 300)

default: 3

     
cleanobt boolean Discard equal time photons

default: NO

     
chatter integer Verbosity of output. (0: min verbosity; 5: max verbosity)

default: 2

     


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