TGCat video demos:
Video Demo 1 --
Video Demo 2 --
Video Demo 3 --
on plotting combined observations, and then identifying lines with
This catalog is an interface to an archive of X-ray spectra taken
with the diffraction grating spectrometers on the Chandra X-ray
Observatory. Here you can
- search for observations by source,instrument, or other criteria
- browse selections
- review pre-computed summary products
- generate custom plots
- download data for detailed analysis
Chandra has two diffraction grating instruments, the High Energy
Transmission Grating (HETG), and the Low Energy Transmission Grating
(LETG). When used with their primary readout arrays, they are known
as the HETG and LETG spectrometers (HETGS and LETGS, respectively).
The readout arrays are a CCD array (ACIS), or a microchannel plate
detector (HRC). The LETG is also often paired with ACIS. The
instruments have different sensitivities, resolving powers, and
wavelength coverages. The HETGS itself has two channels, the Medium
Energy Grating and the High Energy Grating (MEG and HEG).
The Chandra grating spectrometers are fully described in the
Proposers' Observatory Guide (POG;
In particular, see:
which describe the wavelength coverage, efficiency, and resolving
power of these instruments.
Note for non-X-ray spectroscopists:
On the summary pages, you will see spectra in counts units which
includes the strong signature of the instrumental response.
Quantitative analysis of X-ray spectra --- even at high resolution
--- is most often done using the counts in conjunction with the
response files via forward-folding. In addition, some instruments
do not allow direct inversion - the LETG/HRC configuration does not
allow separation of overlapping orders, so we cannot provide an
accurate flux corrected spectrum (it is source-model dependent).
On these pages, you will find flux-corrected spectra, and you can
plot in spectra in flux units (for data taken with ACIS), and
download an ASCII table of the plot. But be aware that these are
still approximations and that robust results are available through