Usage Example 1
- Load URL: http://tgcat.mit.edu
- Use the "Quick Search" menu form and type in "sigma Gem"
Then you get a source table with basic info about sigma Gem.
- Click on the name and you get the extractions table showing the
individual observations. You should see at least 3, one LETG and two
HETG. Click on any one of these names (in the "object" column) and
you get preview plots (new window or new tab, depending on your
browser setup). (LETG was done in continuous clocking mode, which is
why the sky images are one dimensional.) One of the preview plots is
the high-resolution spectrum.
- In the source table, use the check-boxes on the left to select the
HETG observations. Then go to the menu,
"Actions -> Limit"
to show only the HETG.
- Since we want to combine the two HETG observations, check both
extractions again in the limited view, and ghen use the menu,
"Actions -> Plot Combined"
to go to the interactive plotter. After a pause, you'll get a plot
using default settings.
- Now you can go to the "plotting controls" button in the plot window to
set parameters as you like them. E.g.:
Plot Type: F\gamma/\chi X-units: A Y-scale: Photons
- Uncheck "Xlog" "Ylog" to get linear scales.
- To get just HEG, uncheck "MEG orders", and check "HEG orders" and
- Set xmin, xmax field to 3 and 5; leave ymin, ymax blank to autoscale.
- For binning, check the "bin min S/N" box, set the min S/N to some very
low number to disable that part (e.g., 1.e-8), then set the channel
binning to 4. (these fields allow you to have group a minimum S/N per
bin, or a minimum number of bins, simultaneously).
After a delay during which data are retrieved and loaded, the plot
will be updated.
- Now, if you are happy with the plot, you can go to the menu,
"View -> Custom Plotting -> ASCII dump"
and it will download an ASCII table to your computer.
- If you want the Chandra data products (FITS files, for spectrum,
effective area, and line profile - a.k.a PHA, ARF, & RMF), go back to
the "Extractions Table" (showing the 2 HETG observations), click the
check-boxes again to select both, then go to the menu
"Actions -> Download"
You will get a dialog allowing you to select among the files, then the
package will be prepared (and a subtle message at the bottom of your
browser display). If you gave an email address, then you'll get a
notice when ready. Or you can go to menu,
"TGCat -> Package Download Area"
and you will see your request (and anyone else's done in the last
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