NAME
gtobssim - Generate photon events from astrophysical sources
and process those photons according to the specified
instrument response functions.
USAGE
gtobssim infile srclist scfile evroot simtime startdate use_ac
ra dec radius irfs seed
DESCRIPTION
Gtobssim is a FERMI Science Tool that allows the user to simulate
point and diffuse source FERMI observations using a specific spectral shape
for a selected region of the sky in FERMI survey or pointed
modes. Its intended use includes observation and proposal planning, as
well as assessing actual FERMI observations.
Gtobssim allows you to simulate point and diffuse sources, with
different spectral shapes, for example: (1) non-variable-point sources with
a power-law spectrum or broken power-law spectrum; (2) extended sources
where the incident photons are distributed as a 2D Gaussian projected
on the sky; (3) sources where the user-specified energy distribution is
entered as a 2 column ASCII file; (4) sources for which the energy
distribution is determined by a symbolic expression; (5) isotropic
sources,for which the photons are generated uniformly on the sky
following a power-law spectrum; (6) sources for which the incident photons
are generated from a 3D FITS image comprising an energy axis for the 3rd
dimension and, e.g., RA and Dec as the sky coordinates; sources where the
photons are generated using a 2D FITS image as a template and a single
power-law spectrum is used for the entire map; (7) periodic sources, that
is point sources with sinusoidal light curve; (8) transient sources including
gamma-ray burst.
It is worth to mentioning that not all sources available in gtobssim
are available in gtlike. You may want to use gtlike to perform a
likelihood analysis on your simulated date set in order to obtain the
significance of a detection (see gtlike help for further
explanation). The source models that are included in gtlike are a
subset of the ones available in gtobssim. You should keep this fact in
mind in pursuing your analysis.
In order to simulate a source gtobssim requires that you provide the
spacecraft pointing and live-time history file (a FITS file).
You may use an existing one, create one using
gtorbsim (see gtorbsim help for further explanation) or define a
pointing strategy and let gtobssim compute one.
Another requirement is a source model file. This file is an xml file
with information about the source, such as: integral flux, photon
spectral index, type of spectra, energy range, position of the source
(RA, DEC), etc. This file could be made using templates or using model
editor (see model editor help for further explanation), which is a
GUI-driven tool included in the Fermi Science Tools. This tool is invoked
at the command line, and its use is fairly intuitive. model editor was
first designed to generate source model files for gtlike, but it was
later updated to accommodate models that are supported in both gtlike and
gtobssim. Note that even though the source models for gtlike are in
xml format, the files are not exactly the same as the source xml files
for gtobssim. For the models supported in both gtobssim and in gtlike
you have the option to save them in either format, which helps in the
preparation of your analysis. model editor has a command line help
feature. Type in the command line:
> modeleditor
A gui appears. Then go to "HELP" in the main menu.
The source model file may contain more sources than you want to
simulate for a given task. You will need to provide an ASCII file
with the list of sources you are interested in simulating for that
specific task as an input to gtobssim.
Besides the files mentioned above, you also need to specify
the total simulation "exposure" time, the simulation start date, and
the appropriate response function. You will also enter a
random seed number for the task.
PARAMETERS
infile [file]
File of flux-style source definitions. This is the file that
defines the source content of the simulation to be performed,
including names, sky locations, spectral and flux parameters.
srclist [file]
ASCII file containing list of source names to be simulated.
scfile [file]
Spacecraft data file containing information such as the
spacecraft pointing as a function of time. This file could be
generated by gtorbsim for simulated observations (see gtorbsim
help for further explanation) or more commonly it can be
obtained from the FSSC.
(sctable = SC_DATA) [string]
Spacecraft data extension. This is a hidden parameter. The default value
is: SC_DATA.
evroot [string]
Prefix (text string), which will be applied to all output files.
(evtable = EVENTS) [string]
Event extension name. This is a hidden parameter. The default
value is: EVENTS
simtime [double]
This is the total elapsed time over which simulated data are
generated (in seconds). The total time that gtobssim allows you
to simulate is limited by another parameter: maxtime which is a
hidden parameter with default value of: 3.155e8 seconds. This
corresponds to ~10 years of data, which is the expected lifetime
of FERMI.
(ltfrac = 0.9) [double]
Livetime fraction. Fraction of each 30 seconds interval during
which photon events can be accumulated. This does not include
the effect of SAA passages. This is a hidden parameter. The
default value is 0.9.
(tstart = 0) [double]
Simulation start time in seconds since the start date. This is a hidden
parameter. The default value is 0.
(nevents = no) [bool]
Use simulation time as number of events. This parameter allows
one to specify the number of events to be simulated, rather than
the simulation time. If "yes" is specified the integer portion
of the simulation time is taken to be the number of events. This
is a hidden parameter. The default value is "no".
(maxtime = 3.155e8) [double]
Maximum simulation time (seconds). The maximum simulated time can be
changed by this parameter. This is a hidden parameter. The default value
is: 3.155e8 sec, approximately 10 years.
startdate = 2001-01-01 00:00:00 [string]
Simulation start date. This is the start date for the
simulation. The spacecraft data file should include the range of
time of your simulation. See gtorbsim help to know how to create
the spacecraft data file.
(offset = 0)
Constant offset to be added to MC_SRC_ID values. This is an
integer offset that is applied to the MC_SRC_ID column for
identifying events from specific sources in the input
model. This is a hidden parameter. The default value is 0.
use_ac = no [bool]
Acceptance cone. This parameter allows you to use or nor
acceptance cone. If the value is "yes", gtobssim prompts the
user for information specifying the central coordinates of the
cone (RA,DEC) as well as its radius.
ra [double]
Right ascension of cone center (degrees). If use_acceptance_cone
was set to "yes" you should give the coordinates. This is RA of
the center of the cone in degrees.
dec [double]
Declination of cone center (degrees).
radius [double]
This is the radius in degrees of the acceptance cone if the acceptance
cone was set to "yes".
(emin = 30) [double]
Minimum event energy (in MeV) to include in the simulation. This is a
hidden parameter. The default value is 30 MeV.
(emax = 2e5) [double]
Maximum event energy (in MeV). This is a hidden parameter. The default
value is 200000 MeV.
(edisp = yes)
Energy dispersion. If this flag is set to "yes" the energy
dispersion will be applied to the incoming photons. If this
flag is set to no, a diagonal response is applied and the ENERGY
column equals the input or simulation value. This is a hidden
parameter. The default value is "yes".
irfs[string]
Instrument response functions.
(maxrows = 20000) [int]
Maximum number of rows that each file generated by gtobssim will
contain. This is a hidden parameter. The default value is
200000.
seed [int]
Random number seed for the simulation.
(chatter)
This parameter fixes the output verbosity: no screen output (0),
nominal screen output (2), maximum verbosity (4). This is a
hidden parameter. The default value is 2.
(clobber = yes)
Overwrite existing output files. This is a hidden parameter. The default
value is: "yes".
(debug = no)
Activate debugging mode. This is a hidden parameter. The default value
is "no". When debug is "no", all exceptions that are not caught and
handled by individual tool-specific code are caught by a top-level
exception handler that displays information about the exception and
then exits. When debug is "yes", such exceptions are not caught by the
top level code. Instead the tool produces a segmentation violation,
which is more useful for debugging. When debugging mode is enabled,
the tool produces more verbose output describing any errors or
exceptions that are encountered.
(gui = no)
Graphical user Interface (GUI) mode activated. This is a hidden
parameter. The default value is "no".
(mode = ql)
Mode of automatic parameters. This is a hidden parameter. The default
values is "ql".
EXAMPLES
The way that the parameters are passed following the FTOOLs model:
They could be passed as answers to a prompt or listed in a command
line.
To prompt for gtobssim type in the command line:
>gtobssim
This will prompt for the parameter values. Note: Hidden parameters are
not prompted for. If you want to change one of the "hidden" parameter
you should specify its value in the command line or click advanced in
the GUI. For example if you like to change the minimum energy value
for the events in the simulation you should type in the command line:
>gtobssim emin=100
In this case the minimum energy of the event will be set to 100 MeV
instead of 30 MeV (the default value). The rest of the values will be
prompted to you.
Examples of possible sources that could be simulated by gtobssim are
listed below (Note: No all sources that gtobssim could generate are
described in the examples):
1) A Power Law source:
An easy example that you may wish to try is to simulate a point source
with a power-law spectra. An example of how to generate a source model
file to simulate 3C279 (Ra=193.98, Dec=-5.82) with a power law spectra
with a photon spectral index of 1.96 and an integrated flux of 3.48e-4
m^-2s^-1 is given below:
It is strongly recommended to produce this source model files directly
using model editor (see model editor help).
In this case 3C279 (Ra=193.98, Dec=-5.82) is simulated with a photon
spectral index of 1.96 and an integrated flux between 20 MeV and
200000 MeV of 3.48e-4 m^-2s^-1. The parameter escale specifies the
units of energy used elsewhere in the source specification. It can
have values of MeV or GeV, (with GeV as default). In the example MeV
was chosen.
For this source model file the ASCII source data file should read:
_3C279
(Note: It is not possible to write directly 3C279 as source name in
the xml source file)
An example of inputs parameters is given below:
> gtobssim
File of flux-style source definitions [none] src_sim.xml
File containing list of source names [sources_name.txt] source.dat
Pointing history file [none] spacecraft_data_file.fits
Prefix for output files [test] 3C279
Simulation time (seconds) [86400] 2592000
Simulation start date [2001-01-01 00:00:00] 2008-12-31
Apply acceptance cone? [no] yes
RA of cone center (degrees) (-360:360) [0] : 193.98
Dec of cone center (degrees) (-90:90) [0] : -5.82
Acceptance cone radius (degrees) (0:180) [20] 40
Response functions [] P6_V3_DIFFUSE
Random number seed [29304] :
added source "_3C279"
Generating events for a simulation time of 2.592e+06 seconds....
Done.
In this case the simulation started on 2008-12-31 and lasted for 1
month (2592000 seconds). The Pointing history file used was
spacecraft_data_file.fits. The Response Function used was P6_V3_DIFFUSE.
The number of events generated was: 15, and two files were created
3C279_events_0000.fits (the fits file with the events) and
3C279_srcIds.txt (an ASCII file with the summary information). The
minimum and maximum energy values for the simulation are the default
values in this case. If you enter emin=30 in the command line as
input, then the resulted events will have an energy larger that 30
MeV. But the expected integrated flux between 20 MeV and 200000MeV
will be the one that is in the source model file: 3.48e-4 m^-2s^-1.
That last example could be also run in the command line as follows:
>gtobssim infile= src_sim.xml srclist= sources.dat
scfile=spacecraft_data_file.fits evroot=mysource simtime=2592000
startdate=2008-12-31 use_ac=yes ra=193.98 dec=-5.82 radius=40 irfs=
P6_V3_DIFFUSE seed=29304
2) Background source:
To produce a realistic model you should also include the simulation of
the Galactic and Extragalactic background.
2a) RECOMMENDED Background Model by the Diffuse group:
The recommended diffuse model is simulated using the following
xml file:
See the example given in the following web page:
http://fermi.gsfc.nasa.gov/ssc/data/analysis/scitools/obssim_tutorial.html.
The model file gll_iem_v02.fit is a MapCube source, suitable for use with
Likelihood and ObsSim XML source models. The MapCube is all-sky in Galactic
coordinates with 0.5 deg pixels. It has 30 planes of energy, logarithmically
spaced from 50 MeV to 100 GeV.
The model is a 'Ring' or 'Hybrid' model developed by Jean-Marc Casandjian
and Isabelle Grenier using the same gas ring maps that GALPROP uses,
and the inverse Compton intensity calculated by GALPROP. Most or all of the
rings have been generated by Guðlaugur Jóhannesson (Gulli), with the CO
rings based on a specially-filtered composite data set prepared by Tom Dame.
GALPROP is developed by Gulli, Igor Moskalenko, Troy Porter, and Andy Strong.
gll_iem_v02.fit is defined only up to 100 GeV.
2b)Other Galactic Background Models:
To simulate the diffuse Galactic background you may use MapSource as
spectral class. In Mapsource the photons are generated using a 2D FITS
image as a template. A single power-law spectrum is used for the
entire map. A sample xml source file is given below:
In the example above the total photon flux from the map is (#/m^2/s) =
26.56; the Photon spectral index is 2.1; the minimum photon energy is 30
MeV; and the maximum photon energy is 2x10^5 MeV. The fits file
EGRET_diffuse_gal.fits is the EGRET interstellar emission model (basically that
of Hunter et al. ApJ 481 pag 205 1997), which is available in the Science
Tools distribution in "$(FERMI_DIR)/refdata/fermi/galdiffuse" directory.
Again, you can generate the same source model using directly the model
editor tool (see model editor help).
An example of input parameters to simulate the all-sky diffuse
background is given below for 1-day simulation starting 2008-12-31 and
with P6_V3_DIFFUSE as response function:
> gtobssim
File of flux-style source definitions [src_sim.xml] :
File containing list of source names [sources.dat] :
Pointing history file [spacecraft_data_file.fits] :
Prefix for output files [galactic_back] :
Simulation time (seconds) [86400] :
Simulation start date [2008-12-31] :
Apply acceptance cone? [no] :
Response functions [P6_V3_DIFFUSE] :
Random number seed [29304] :
added source "Galactic_Diffuse"
Generating events for a simulation time of 86400 seconds...
Done.
Two files were created: galactic_back_events_0000.fits (the fits file
with the events) and galactic_back_srcIds.txt (an ASCII file with the
summary information). This example generated 29827 events.
Another way to simulate the diffuse background is to use the MapCube
source, which is a generalization of MapSource source. MapCube allows
separate maps to be specified for arbitrary energies. This allows for
spectral variations across a diffuse source. MapCube was used to
generate the interstellar gamma rays from the Milky Way using a cube
generated from gamma-ray intensities calculated by the GALPROP
software (http://galprop.stanford.edu/na_home.html). The example below
is for the GP_gamma.fits model of the interstellar emission of the
Milky Way.
The MapCube source has only 2 parameters in its specification: Total
photon flux from the map, integrated over the energy range of the cube
(#/m^2/s) and the Fits file of cube. Note that MapCube requires that
the input FITS files contain a binary table extension called
'ENERGIES' that defines the energy of each of the spatial planes in
the cube. The units of the map are differential intensity (e.g.,
photons cm^-2 s^-1 MeV^1 sr^-1), although the integral value is
renormalized by whatever total photon flux is specified in the
specification of the source. Note that GP_gamma.fits does not contain
extragalactic diffuse emission. See next section for an example of how
to simulate the extragalactic background. This file is available in
the Science Tools distribution in "$(FERMI_DIR)/refdata/fermi/galdiffuse" directory.
The input example below is for the GP_gamma.fits model of the
interstellar emission of the Milky Way;
> gtobssim
File of flux-style source definitions [src_sim.xml] : src_sim2.xml
File containing list of source names [sources.dat] :
Pointing history file [spacecraft_data_file.fits] :
Prefix for output files [galactic_back] : galactic_back_GP
Simulation time (seconds) [86400] :
Simulation start date [2008-12-31] :
Apply acceptance cone? [no] :
Response functions [P6_V3_DIFFUSE] :
Random number seed [29304] :
added source "Galactic_Diffuse"
Generating events for a simulation time of 86400 seconds....
Done.
Two files were created: galactic_back_GP_events_0000.fits (the fits
file with the events) and galactic_back_GP_srcIds.txt (an ASCII file
with the summary information). This input generated 36952 events.
That previous example could be also run in the command line as follows:
>gtobssim infile= src_sim.xml srclist=sources.dat
scfile=spacecraft_data_file.fits evroot= galactic_back_GP simtime=86400
startdate=2008-12-31 use_ac=no irfs=P6_V3_DIFFUSE seed=29304
2b) Other Extragalactic Emission Model:
The source model file below implements the extragalactic diffuse
inferred by EGRET (Sreekumar et al. ApJ 494 pag 523 1998). The flux
has units of photons m^-2 s^-1 integrated between Emin and Emax. The
photon spectral index is gamma, i.e., dN/dE = Const*E -gamma .
This source model file could be obtained using directly model editor
(see model editor help).
For this example the ASCII source data file should read:
Extragalactic_Diffuse
An example of how to run gtobssim to simulate these sources is given below:
> gtobssim
File of flux-style source definitions [none] src_sim.xml
File containing list of source names [source_names.txt] : sources.dat
Pointing history file [none] : spacecraft_data_file
Prefix for output files [test] : extragalactic_back
Simulation time (seconds) [86400]
Simulation start date [2001-01-01 00:00:00] 2008-12-31
Apply acceptance cone? [no] :
Response functions [] P6_V3_DIFFUSE
Random number seed [29304] :
added source "Extragalactic_Diffuse"
Generating events for a simulation time of 86400 seconds....
Done.
Two files were created: extragalactic_back_events_0000.fits (the fits
file containing the events) and extragalactic_back_srcIds.txt (an
ASCII file with the summary information). This source generated 12136
events in the 1-day observation. The response function used was
P6_V3_DIFFUSE.
That last example could be also run in the command line as follows:
>gtobssim infile=src_sim.xml srclist=sources.dat
scfile=spacecraft_data_file.fits evroot= extragalactic_back simtime=86400
startdate=2008-12-31 use_ac=no irfs= P6_V3_DIFFUSE seed=29304
3) Broken Power Law spectra
An example of an xml source file to simulate a point source with a
broken power-law spectra is given below:
The total integrated flux between 20 and 200000 MeV is, in this case,
5e-4m^-2s^-1. The photon spectral index is 1.80 between 20 MeV and
1000 MeV (the break in the spectra) and 2.30 between 1000 MeV and
200000 MeV.
This source model file could be obtained using directly model editor
(see model editor tool).
The ASCII data file for this source should read:
mysource
An example of input parameters is given below:
> gtobssim
File of flux-style source definitions [src_sim.xml] :
File containing list of source names [sources.dat] :
Pointing history file [spacecraft_data_file.fits] :
Prefix for output files [3C279] : mysource
Simulation time (seconds) [2592000] :
Simulation start date [2008-12-31] :
Apply acceptance cone? [yes] :
RA of cone center (degrees) <-360 - 360> [193.98] : 195.555759
Dec of cone center (degrees) <-90 - 90> [-5.82] : 57.066813
Acceptance cone radius (degrees) <0 - 180> [40] :
Response functions [P6_V3_DIFFUSE] :
Random number seed [29304] :
added source "mysource"
Generating events for a simulation time of 2.592e+06 seconds....
Done.
In this case the simulation started on 2008-12-31 and lasted for 1
month (2592000 seconds). The Pointing history file used was
spacecraft_data_file.fits. The Response Function used was P6_V3_DIFFUSE.
The number of events generated was: 24. Two files were created
mysource_events_0000.fits (the fits file with the events) and
mysource_srcIds.txt (an ASCII file with the summary information).
That last example could be also run in the command line as follows:
>gtobssim infile= src_sim.xml srclist= sources.dat
scfile=spacecraft_data_file.fits evroot=mysource simtime=2592000
startdate=2008-12-31 use_ac=yes ra=195.555759 dec=57.066813 radius=40
irfs=P6_V3_DIFFUSE seed=29304
4) Gaussian source:
In this case, the incident photons are distributed as a 2D Gaussian projected on the sky.
An example of source model is given below:
The parameters are:
Total flux in units of m^-2 s^-1
Photon spectral index such that dN/dE~E^-/Gamma
Source centroid J2000 right ascension in degrees.
Source centroid J2000 declination in degrees.
Semi-major axis of the 68% CL contour in degrees (default: 1).
Semi-minor axis of the 68% CL contour in degrees (default: 1).
Position angle of the major axis measured wrt North in degrees (default: 0)
Minimum photon energy in MeV (default: 30).
Maximum photon energy in MeV (default: 1e5)
This source model file could be obtained using directly model editor
(see model editor help).
The ASCII data file for this source should read:
gaussian_source
An example of inputs parameters is given below:
> gtobssim
File of flux-style source definitions [src_sim.xml] :
File containing list of source names [sources.dat] :
Pointing history file [spacecraft_data_file.fits] :
Prefix for output files [extragalactic_back] : gaussian
Simulation time (seconds) [86400] : 2592000
Simulation start date [2008-12-31] :
Apply acceptance cone? [no] : yes
RA of cone center (degrees) <-360 - 360> [266.404996] : 120
Dec of cone center (degrees) <-90 - 90> [-28.936172] : 60
Acceptance cone radius (degrees) <0 - 180> [40] :
Response functions [P6_V3_DIFFUSE] :
Random number seed [29304] :
added source "gaussian_source"
Generating events for a simulation time of 2.592e+06 seconds....
Done.
In this case the simulation started on 2008-12-31 and lasted for 1
month (2592000 seconds). The Pointing history file used was
spacecraft_data_file.fits. The number of events generated was: 6053, and two
files were created gaussian_events_0000.fits (the fits file with the
events) and gaussian_srcIds.txt (an ASCII file with the summary
information).
That last example could be also run in the command line as follows:
>gtobssim infile= src_sim.xml srclist= sources.dat
scfile=spacecraft_data_file.fits evroot= gaussian simtime=2592000
startdate=2008-12-31 use_ac=yes ra=120 dec=60 radius=40 irfs=P6_V3_DIFFUSE
seed=29304
5) Periodic source:
It is possible to simulate a point source with sinusoidal light
curve. _The example below corresponds to the simulation of a periodic
source in the center of the Galaxy:
The parameters are:
Average flux in units of m^-2 s^-1.
Photon spectral index such that dN/dE ~E^-\Gamma
Source period in seconds.
Amplitude of the sinusoidal modulation (default: 0.5).
Phase offset specified on the unit interval (default: 0).
Minimum photon energy in MeV (default: 30)
Maximum photon energy in MeV (default: 1e5)
The ASCII data file for this source should read:
periodic_source
An example of inputs parameters is given below:
> gtobssim
File of flux-style source definitions [src_sim.xml] :
File containing list of source names [sources.dat] :
Pointing history file [spacecraft_data_file.fits] :
Prefix for output files [gaussian] : periodic
Simulation time (seconds) [2592000] :
Simulation start date [2008-12-31] :
Apply acceptance cone? [yes] :
RA of cone center (degrees) <-360 - 360> [120] : 266.404996
Dec of cone center (degrees) <-90 - 90> [60] : -28.936172
Acceptance cone radius (degrees) <0 - 180> [40] :
Response functions [P6_V3_DIFFUSE] :
Random number seed [29304] :
added source "periodic_source"
Generating events for a simulation time of 2.592e+06 seconds....
Done.
In this case the simulation started on 2008-12-31 and lasted for 1
month (2592000 seconds). The Pointing history file used was
spacecraft_data_file.fits. P6_V3_DIFFUSE was used as Response Function. Two files
were created periodic_events_0000.fits (the fits file with the events)
and periodic_srcIds.txt (an ASCII file with the summary information).
That last example could be also run in the command line as follows:
>gtobssim infile=src_sim.xml srclist=sources.dat
scfile=spacecraft_data_file.fits evroot=periodic simtime=2592000
startdate=2008-12-31 use_ac=yes ra=266.404996 dec=-28.936172
radius=40 irfs=P6_V3_DIFFUSE seed=29304
6) Pulsar Source:
To simulate a pulsar you need to create an ASCII template file
containing the light curve. The file should consist of two columns:
phase and intensity. The phase intervals must be uniformly spaced. The
phase scale and absolute intensities are arbitrary and rescaled using
the period and flux parameter values.
The following is an example of the source file for a pulsar. In this
case the Crab pulsar it is simulated with the template named:
CrabTemplate.dat.
The parameters are:
Average flux in units of m^-2 s^-1.
Photon spectral index such that dN/dE~E-\gamma
Pulsar period in seconds.
Time derivative of the pulsar period in ss^-1
Reference epoch in MET seconds.
Filename of the ASCII light curve template. The file should consist of
two columns, phase and intensity. The phase intervals must be
uniformly spaced. The phase scale and absolute intensities are
arbitrary and rescaled using the period and flux parameter values.
Phase offset in the unit interval (default: 0).
Minimum photon energy in MeV (default: 30).
Maximum photon energy in MeV (default: 1e5).
The ASCII data file for this source should read:
Crab_pulsar
An example of inputs parameters is given below:
> gtobssim
File of flux-style source definitions [src_sim.xml] :
File containing list of source names [sources.dat] :
Pointing history file [spacecraft_data_file.fits] :
Prefix for output files [periodic] : crab
Simulation time (seconds) [2592000] :
Simulation start date [2008-12-31] :
Apply acceptance cone? [yes] :
RA of cone center (degrees) <-360 - 360> [266.404996] : 83.57
Dec of cone center (degrees) <-90 - 90> [-28.936172] : 22.01
Acceptance cone radius (degrees) <0 - 180> [40] :
Response functions [P6_V3_DIFFUSE] :
Random number seed [29304] :
added source "Crab_Pulsar"
Generating events for a simulation time of 2.592e+06 seconds....
Done.
In this case the simulation started on 2008-12-31 and lasted for 1
month (2592000 seconds). The Pointing history file used was
spacecraft_data_file.fits. P6_V3_DIFFUSE was used as Response Function.
The number of events generated was: 71 and two files were created
crab_events_0000.fits (the fits file with the events) and
crab_srcIds.txt (an ASCII file with the summary information).
That last example could be also run in the command line as follows:
>gtobssim infile=src_sim.xml srclist=sources.dat
scfile=spacecraft_data_file.fits evroot=crab simtime=2592000
startdate=2008-12-31 use_ac=yes ra=83.57 dec=22.01 radius=40 irfs=
P6_V3_DIFFUSE seed=29304
7) SimpleTransient:
This allows the user to simulate a point source with a single active
interval during which it has a constant flux and power-law
spectrum. An example of source model is given below:
The parameters are:
Flux while in the active state in units of m^-2 s^-1,
Photon spectral index such that dN/dE~E^-Gamma
Start time of the active state in MET seconds.
Stop time of the active state in MET seconds.
Minimum photon energy in MeV (default = 30)
Maximum photon energy in MeV (default = 1e5)
The ASCII data file for this source should read:
simple_transient
An example of input parameter is given below;
> gtobssim
File of flux-style source definitions [src_sim.xml] :
File containing list of source names [sources.dat] :
Pointing history file [spacecraft_data_file.fits] :
Prefix for output files [simpleT] :
Simulation time (seconds) [86400] :
Simulation start date [2008-12-31] :
Apply acceptance cone? [yes] :
RA of cone center (degrees) <-360 - 360> [83] :
Dec of cone center (degrees) <-90 - 90> [22] :
Acceptance cone radius (degrees) <0 - 180> [40] :
Response functions [P6_V3_DIFFUSE] :
Random number seed [293049] :
In this case the simulation started on 2008-12-31. The Pointing
history file used was spacecraft_data_file.fits. P6_V3_DIFFUSE was
used as Response Function. The number of events generated was:
10, and two files were created simpleT_events_0000.fits (the fits
file with the events) and simpleT_srcIds.txt (an ASCII file with
the summary information).
That last example could be also run in the command line as follows:
>gtobssim infile=src_sim.xml srclist=sources.dat
scfile=spacecraft_data_file.fits evroot=simpleT simtime=86400
startdate=2008-12-31 use_ac=yes ra=83 dec=22 radius=40 irfs=P6_V3_DIFFUSE
seed=29304
8) SpectralTransient:
It is possible to simulate a transient source giving the light curve
data as template. Here you have an example of source model:
The parameters are:
Mean flux during the active state in units of m^-2s^-1
Start time of the active state in MET seconds.
Stop time of the active state in MET seconds.
Filename of the light curve template. May be ASCII or FITS.
Minimum photon energy in MeV (default: 20).
Maximum photon energy in MeV (default: 2e5).
Light curve number, if FITS file (default: 0).
Redshift used for EBL attenuation calculation (default: useLogParabola
(default = 0)
The ASCII data file for this source should read:
spectral_transient
An example of inputs parameters is given below:
> gtobssim
File of flux-style source definitions [src_sim.xml] :
File containing list of source names [sources.dat] :
Pointing history file [spacecraft_data_file.fits] :
Prefix for output files [simpleT] : spectraT
Simulation time (seconds) [2592000] :
Simulation start date [2008-12-31] :
Apply acceptance cone? [yes] :
RA of cone center (degrees) <-360 - 360> [83] : 193.4
Dec of cone center (degrees) <-90 - 90> [22] : -5.82
Acceptance cone radius (degrees) <0 - 180> [40] :
Response functions [P6_V3_DIFFUSE] :
Random number seed [29304] :
added source "spectral_transient"
Generating events for a simulation time of 2.592e+06 seconds....
Done.
In this case the simulation started on 2008-12-31 and lasted for 1
month (2592000 seconds). The Pointing history file used was
spacecraft_data_file.fits. P6_V3_DIFFUSE was used as Response Function.
The number of events generated was: 61, and two files were created
spectraT_events_0000.fits (the fits file with the events) and
spectraT_srcIds.txt (an ASCII file with the summary information).
That last example could be also run in the command line as follows:
>gtobssim infile=src_sim.xml srclist=sources.dat
scfile=spacecraft_data_file.fits evroot=spectraT simtime=2592000
startdate=2008-12-31 use_ac=yes ra=193.4 dec=-5.82 radius=40
irfs=P6_V3_DIFFUSE seed=29304
Examples of xml files to use with the gtobssim tool could be downloaded
directly from this web site:
http://fermi.gsfc.nasa.gov/ssc/data/analysis/scitools/other_sources.html
LIST OF BUGS
SEE ALSO
* gtorbsim