BiRD is a browsing and visualization tool for XMM-Newton RGS fluxed spectra. It allows the user to browse and examine the data before downloading them from the XSA for full analysis.
The BiRD interface makes possible to select spectra through a variety of parameters, such as (e.g.) date of observation, level of exposure or type of object.
It also provides some basic visualization utilities, both for the RGS spectra and spectral images, as well as for the EPIC-pn images taken in parallel.
The Reflection Grating Spectrometer is one of the instruments on-board XMM-Newton. Its purpose is to obtain high spectral resolution (from 100 to 500, FWHM) X-ray spectroscopy in the range 5-38 Å.
Two of the three XMM-Newton X-ray telescopes are equipped with RGS instruments. After the first week of operations, an electronic component of one one of the RGS2 chips failed, affecting the wavelength range from 20.0 to 24.1 Å. A similar problem occurred in early September 2000 with one of the chips of RGS1 covering 10.6 to 13.8 Å. The total effective area is thus reduced by a factor of two in these wavelength bands.
A detailed description of the characteristics and performance of the RGS instruments can be found in the XMM-Newton Handbook.
RGS fluxed spectra are computed dividing the extracted spectrum by the effective area calculated from its corresponding response matrix (see the description of the SAS task rgsfluxer).
This procedure neglects the redistribution of monochromatic response into the dispersion channels, and therefore these spectra should not be used for any detailed spectral analysis of the data (e.g. measurement of line widths).
Nevertheless, fluxed spectra are extremely useful for visualizing the data free from the peculiarities of the instrument. This is especially so because of the possibility of combining data from both cameras into a single spectrum, thus eliminating many of the gaps between functioning detectors.
Fluxed spectra are given in physical units (photons/cm²/s/Å vs. Å).
The Reflection Grating Spectrometer on board XMM-Newton, den Herder, J.W. et al, 2001, A&A 365, L7
ODFs have been downloaded from the XMM-Newton Science Archive (XSA) and processed with SAS.
Data were processed with the SAS metatask rgsproc.
rgsproc was run using the target coordinates given in the XMM-Newton proposal
First order spectra (without background subtraction) were generated using 100% of the spatial PSF. A model background spectrum (generated with the SAS task rgsbkgmodel) was used for the background correction.
Response matrices were computed for each spectrum with rgsrmfgen
Finally, a fluxed spectrum was created for each observation combining all the available RGS1 and RGS2 first order spectra with rgsfluxer
In addition to the spectra themselves, the BiRD interface provides other information that might be useful for the interpretation of the data:
Start time of the observation
Target name as provided in the XMM-Newton proposal
Target coordinates as provided in the XMM-Newton proposal
RGS effective exposure time (taken as the average of the exposure time of the RGS1 and RGS2 spectra)
An estimation of the quality of the combined RGS1+RGS2 fluxed spectrum
Galactic Hydrogen column density, obtained from Dickey and Lockman (1990)
From the SIMBAD database:
SIMBAD was queried to derive a first target identification and classification using the target name given in the XMM-Newton proposal as input. In the cases where a SIMBAD object could not be unambiguously selected using the target name, the procedure was done manually, examining the different identifications of nearby objects. For a number of cases, the type of object was obtained from the abstract of the scientific justification of the proposal.
Some particular cases: