-
set up your SAS environment (following the
SAS
start-up thread)
-
extract an image (in sky coordinates in this example; extraction in detector
- DET[XY] - coordinates is possible as well)
evselect table=PN.evt:EVENTS imagebinning=binSize imageset=PNimage.fits withimageset=yes \
xcolumn=X ycolumn=Y ximagebinsize=80 yimagebinsize=80
-
display the image
imgdisplay withimagefile=true imagefile=PNimage.fits
-
select the region, from which the light curve shall be accumulated, using
the
Region/Circle in ds9 (see Fig.1)
Fig.1: ds9 main window. A circular region (green circle)
has been defined using the highlighted menu.
-
double-click with the cursor on the defined region. A window pops up, showing
the properties of the region (Fig.2). Write down the coordinates of the
Center (25910.5, 25870.5) and the Radius(400).
Fig.2: Selection region properties window, pop'd-up by double-clicking
on the region in the main ds9 window
Units of sky coordinates (X,Y) are 0.05 arcsec, hence the radius in
our example is 20 arcsec.
-
extract a source+background light curve,
using all the selection expressions defined
so far. In the example, the binsize is 100 seconds and the energy range is 0.2 to 10 keV. Please take into account that operating
with non-synchronous time series can introduce artifacts when they are added or subtracted
by programs such as the ftools "lcmath". To avoid this problem use time limits explicitely
set in the command line.
evselect table=PN.evt energycolumn=PI expression='#XMMEA_EP&&(PATTERN<=4)&& \
((X,Y) IN circle(25910.5,25870.5,400))&&(PI in [200:10000])' withrateset=yes rateset="light_curve.fits" timebinsize=100 \
maketimecolumn=yes makeratecolumn=yes timemin=126991800 timemax=130000000
The parameter makeratecolumn=yes produces a light curve in count
rates (with errors). Otherwise the light curve is produced in counts
(with errors).
-
repeat step 4. to 6. above to determine the region, from which the
background light curve is to be extracted. We will assume in the following
the the extraction region correspond to an annulus, centered in
(25910.5,25870.5) and with inner and outer radii 1000
and 2000 pixels, respectively
-
extract a background light curve,
using all the selection expressions defined
so far, and the same binsize (100 seconds) and energy range as for the source+background
light curve
evselect table=PN.evt energycolumn=PI expression='#XMMEA_EP&&(PATTERN<=4)&& \
((X,Y) IN annulus(25910.5,25870.5,1000,2000)&&(PI in [200:10000])' withrateset=yes rateset="light_curve_background.fits" timebinsize=100 \
maketimecolumn=yes makeratecolumn=yes timemin=126991800 timemax=130000000
-
plot the resulting light curves, eg.
dsplot table=light_curve_background.fits withx=yes x=TIME withy=yes y=RATE
This command will launch the following xmgrace window
Fig.3: xmgrace window, containing the extracted light curve
The light curves are OGIP-complaint, and therefore analyzable with standard
XRONOS-like LHEASOFT packages.
RGS
We will assume in what follows that RGS products are available in the work
directory, as according to the PPS naming convention. If
the following files are available: a) RGS event list; b) RGS source
list, just a single evselect command allows a user to create a
light curve, corresponding to the extraction regions in the
spatial and order images.
-
set up your SAS environment (following the
SAS
start-up thread)
-
create a 1st order, 100-seconds binned
source light curve, for the n-th source in
the RGS1 source list
evselect table=P0133120201R1S001EVENLI0000.FTZ expression='region(P0133120201R1S001SRCLI_0000.FTZ:RGS1_SRCn_SPATIAL,BETA_CORR,XDSP_CORR) \
&®ion(P0133120201R1S001SRCLI_0000.FTZ:RGS1_SRCn_ORDER_1,BETA_CORR,PI)' withrateset=yes rateset="light_curve.fits" \
timebinsize=100 maketimecolumn=yes makeratecolumn=yes
-
create a 2nd order, 100-seconds binned
source light curve, for the n-th source in
the RGS1 source list
evselect table=P0133120201R1S001EVENLI0000.FTZ expression='region(P0133120201R1S001SRCLI_0000.FTZ:RGS1_SRCn_SPATIAL,BETA_CORR,XDSP_CORR) \
&®ion(P0133120201R1S001SRCLI_0000.FTZ:RGS1_SRCn_ORDER_2,BETA_CORR,PI)' withrateset=yes rateset="light_curve.fits" \
timebinsize=100 maketimecolumn=yes makeratecolumn=yes