XMM-Newton Users Handbook

3.4.6.3 RGS spectral quality

Examples of RGS spectra are given in Figs. 73 to 81. A significant fraction of the apparent continuum background measured underneath the Fe-L forest, is due to scattered light. This is included in the response matrix of the instrument, which has to be used to determine the underlying spectral properties.

Figure 73: Coronal spectrum of the binary star Capella adapted from Audard et al. 2001, A&A 365, L329. The RGS 1 first order spectrum is shown with some line identifications. The total exposure time is 53 ks.

Figure 74: RGS spectra of the highly variable low-mass X-ray binary EXO 0748-67. The three panels show the spectra for three different activity states: low emission, active variation and burst. The spectra are binned to 0.035 Å per bin. The cumulative exposure time for each spectrum is indicated (Cottam et al. 2001, A&A 365, L277).

Figure 75: Detail of the EXO 0748-67 RGS spectrum. The O VII He-like lines are shown overlaid with the instrument line spread function, broadened to account for a 1390 km s$^{-1}$ velocity field. The contributions from the resonance line (r), intercombination lines (i), and forbidden line (f) are shown with thin lines. The thick line shows the combined fit (Cottam et al. 2001, A&A 365, L277).

Figure 76: The first order RGS spectrum of the SMC supernova remnant 1E 0102.2-7219. The effective exposure time is 29.7 ks for each RGS after selection of low background periods in a 37.9 ks exposure. RGS 1 is plotted in black, RGS 2 in red. The data are shown in both linear and logarithmic scales. This figure and the next show that almost the nominal RGS spectral resolution can be achieved even for moderately extended ($\approx$ 2$^\prime$) objects (Rasmussen et al., 2001, A&A 365, L231).

Figure 77: Detail of the 8-20 Å region of the spectrum shown in the previous figure. First (black) and second (red) order are plotted separately. The data from the two spectrometers have been averaged for each order extraction. The higher spectral resolution and resilience to source extent is clearly seen in second order, where some line complexes blended in first order are resolved (Rasmussen et al., 2001, A&A 365, L231).

Figure 78: Detail of the Oxygen line profile in the 1E 0102.2-7219 spectrum. The plot compares the point source line spread function for RGS 1, the approximate monochromatic line profile based on the target's angular distribution and a heuristic wavelength broadening function that is applied in addition to the angular distribution (Rasmussen et al., 2001, A&A 365, L231).

Figure 79: RGS spectrum of the bright starburst nucleus of the nearby edge-on galaxy NGC 253, binned to 0.07 Å per bin. The effective exposure time is $\approx$ 53.4 ks for each spectrograph, after selection of low background periods. The extraction region is 1$^\prime$ along the minor disk axis. (Pietsch et al. 2001, A&A 365, L174).

Figure 80: RGS spectra of two bright, nearby, Narrow Line Seyfert 1 galaxies. MCG-6-30-15 (top) was observed for a total of 120 ks while the exposure time for Mrk 766 (bottom) was 55ks. (Branduardi-Raymont et al. 2001, A&A 365, L140).

Figure 81: The RGS spectrum of the rich cluster of galaxies Sérsic 159-03 (Abell S 1101). The effective exposure time is 36 ks. The plot also shows in red a fit with a two component cooling flow model. Note the red-shifted O VIII Ly $\alpha$ line at 20.0 Å and the Fe XXIV, Fe XXIII and Ne X lines between 11.2 and 12.8 Å (Kaastra et al. 2001, A&A 365, L99).