| 2.1 | Optical layout of the FUSE instrument showing the 4-channel design. | ||
| 2.2 | Locations of the FUSE apertures and reference point (RFPT) on the FPA. Note that the RFPT is not an aperture. With north on top and east on the left, this diagram corresponds to an aperture position angle of 0°. Positive aperture position angles correspond to a counterclockwise rotation of the spacecraft (e.g. this FOV) about the target aperture. Projected onto an FES camera, this diagram only represents a small portion of the full 19′ × 19′ active area of the FES, whose center would be out of the field to the right from this Figure. The aperture centers shown in this coordinate system are reported in Table 2.1. | ||
| 2.3 | Schematic view of the wavelength coverage, dispersion directions, and image locations
for the FUSE detectors. In this figure, the detector pixel coordinates of the corner
of each segment are shown. The X and Y
axes indicate orientation on the sky.
Wavelength ranges shown are approximate (see Table 2.2).
| ||
| 4.1 | A geometrically corrected image of spectra on the Side 1 detector for a single exposure, shown with a log display function. For each exposure, four spectra are produced for each side. The variable vertical height of the spectra is the result of astigmatism introduced by the FUSE spectrographs. Note the minimum astigmatic points, as mentioned in the text. The vertical emission line near the narrowest part of the LiF1A spectrum is due to Lyβ airglow (the airglow from the HIRS and MDRS apertures can be seen faintly above it). The horizontal stripes visible in the LiF1A and LiF1B spectra are termed "worms" (see Chapter 7). The small dots near Y ~ 800 are due to STIM pulses injected into the electronics (see Section 2.2.3). Slight misalignments between the detector segments are due to varying pixel scales. | ||
| 4.2 | Same as Fig. 4.1, but for the Side 2 detector. Again a log display function has been used to show the faintest emission features. | ||
| 4.3 | Example of a count rate plot (*rat.gif) for detector segment 1A of exposure 001 for the TTAG observation C1600101. These plots show the count rates within the science apertures. The various reasons for flagging bad data are shown below the figure. The dashed curve is the count rate from the sections of the detector used for burst detection. In this case, the plot shows that the observation was obtained during the day, and that several bursts were detected and eliminated from the final spectrum. It also shows that the SiC1A count rate varied significantly during the observation. Because the same plot for LiF1A is stable, we conclude that the target was wandering in and out of the SiC1 aperture (see Chapter 7). As a result, the flux level of the SiC1A spectrum will be less than other channels covering similar wavelengths (see Fig. 4.7). CalFUSE cannot check for this effect since different segments are processed independently and cannot be compared. However, users can use the FUSE tools to exclude these regions (see Chapters 3 and 8). | ||
| 4.4 | Example of a detector image (*ext.gif) for the same segment as shown in Figure 4.3 for a target in the LWRS aperture. This image is made from the IDF file and has been geometrically corrected for instrumental effects. It is not to scale since the actual detector has a 16:1 aspect ratio. Both pixel and wavelength scales are shown, as are the locations of the spectra from the different apertures on the segment. In the TTAG data, the effect of the different aperture sizes on airglow line intensity is clearly apparent. The vertical lines appearing at Lymanβ in both spectra are due to airglow emission. Some of the airglow emission falls outside of the extraction window because it is an extended emission. Note that the colors are reversed so that absorption features appear as bright stripes and emission features appear as dark stripes. | ||
| 4.5 | Similar to Fig. 4.4, except for the 1B segment of the HIST observation M1030606002. In this case, the data have a striped appearance. This is because the raw HIST image is binned in Y, and the pipeline simply maps all of events registered by a binned pixel onto the mean value of the bin. This results in rows of filled pixels, separated by several rows of vacant pixels. The rows in this image are curved because they have been corrected for geometric distortions. The top part of the plot is an image of the LiF1B segment. The elongated white stripe in LiF1 near 1150 Å in this segment is due to the "worm" (see Section 7.5). For HIST, data are only collected from the region around the science aperture, LWRS in this case. So no data are seen on most of the segment. Note that the colors are reversed so that absorption features appear as bright stripes and emission features appear as dark stripes. | ||
| 4.6 | Examples of coadded detector spectra for two channels of observation D0640301. These plots are for both segments of the SiC1 (left) and LiF1 (right) channels. Note that total exposure times for each segment can be different, since CalFUSE may eliminate different portions of the data for each segment from the final spectra due to its detection of various anomalies (see Chapter 7). | ||
| 4.7 | Examples of coadded detector spectra for two channels of observation C1600101. These plots are for both segments of the SiC1 (left) and LiF1 (right) channels. Note the difference in flux level over the wavelength range common to both channels. Such discrepancies usually indicate that the target was either partly or completely out of the aperture of one channel during part of the observation. | ||
| 4.8 | Example of a combined, observation-level preview file for observation D0640301. The image presents spectra from three segments that span the FUSE wavelength range. It also contains the number of exposures that were combined and the total observation time of the combined exposures. Note that the total exposure time as well as the number of exposures can be different for each segment since CalFUSE processing may eliminate portions of the data affected by various effects or anomalies (see Chapter 7). | ||
| 4.9 | Plot of an exposure-summed spectrum (black trace) and its associated error array (red trace)
for observation D0640301 (*nvo.fit). The error array contains sharp
discontinuities due to the fact that the data from different
segments have been spliced together to form this overview
spectrum.
| ||
| 5.1 | A calibrated FES A image for exposure P1171901701. In this case, there is significant scattered light on the FPA, so that the apertures are visible (see Table 5.2), along with a few stars. (The distorted region around the apertures is an artifact of the manufacturing process.) Note that the colors are reversed in this image so that bright objects appear as black points. | ||
| 5.2 | FUSE pointing in 1 second intervals for an exposure scheduled with stable pointing (left) and one with unstable pointing (right). For the former case, loops outside of the LWRS aperture occur while settling during the target acquisition. The target remains well-centered for the exposure. For the case with unstable pointing, excursions can take the target out of the aperture, but the target returns when pointing control is regained. | ||
| 5.3 | The time series of LiF2 count rates and pointing errors for the exposures shown in Fig. 5.2. For the one with stable pointing (left), the target remains well within the aperture and the count rate is constant during the exposure. For the other, when control becomes unstable, photons are lost when the target is out of the aperture (right). | ||
| 5.4 | Example of an MPS timeline chart for a 24h period, demonstrating several of the features described in the text. | ||
| 5.5 | Example of a mission planning guide star plot. The apertures are located at ~Y = 400. The crosshairs show which aperture is being used, LWRS in this case. | ||
| 5.6 | Example of a daily count rate plot. See text for details. | ||
| 5.7 | Example of a Science Data Assessment Form. | 7.1 | The difference in the degree of airglow contamination between "day + night" spectra and "night-only" spectra of an O4 supergiant in the LMC. This observation (A1330121) was obtained through the LWRS aperture in TTAGmode. The integration time was divided approximately equally between orbital "day" and "night." Top: Note the greatly decreased airglow contamination from Lyβ and the O I λλ1025.76, 1027.43, 1028.16 Å triplet in the "night-only" spectrum. Bottom: Airglow emission partially fills in the interstellar lines of the N I λλ 1134.17, 1134.42, 1134.98 Å triplet. If not reealized, this contamination would lead to erroneous inferences concerning N I along this line of sight using these lines alone. Note also that because the airglow emission is extended, the astigmatism correction applied is inaccurate. |
| 7.2 | portion of Segment 1A showing the stray light band in an airglow spectrum. Note the pattern of alternating bright and dark arcs. LiF Lymanβ is on the upper left and SiC Lymanβ is on the lower right. The greyscale has been reversed so that darker shades of grey represent more counts. | ||
| 7.3 | small region of the LiF2B and SiC1A spectra from P1161401 is plotted, showing saturated H2 absorption. The lower panel gives a magnified view showing the difference in the scattered flux in the two channels. | ||
| 7.4 | pattern noise due to moiré structure in the SiC1B HIST data from target HD 22136 (program Z9011501). The moiré ripples are strongest in segment 2B, but are also seen in segments 1A and 1B as shown here (see also Dixon et al. (2007)). Associated errors are overplotted in red. The upward peak is due to H I airglow emission. | ||
| 7.5 | point-source spectra obtained with the LiF1B (spectra A and B taken at different vertical positions) and LiF2A (spectrum C) segments. The large depressions occuring around 1145 Å in spectrum A and 1160 Å in spectrum B are due to worms. Note that spectrum C is unattenuated in this particular case (see Dixon et al. (2007)). | ||
| 7.6 | Data from the IDF file for segment 2A of exposure D0640301002 obtained by observing target HD 91597 in LWRS. The cf_edit.pro routine (see Chapter 8) was used to display this IDF file and shows the full spectra displayed in the bottom panel of the plot. The top panels show the presence of a Type I dead zone in the SiC2A segment around 997 Å. This plot displays reversed colors where absorption features appear as bright stripes against the dark continuum emission. Right: A comparison of the extracted spectra from segment SiC2A (black trace) and LiF1A (red trace) over their overlapping wavelength range for target HD 91597. In SiC2A, the strong absorption feature around 997 Å is spurious and due the presence of a dead zone at this particular detector location. Note its absence in the LiF1A spectrum. | ||
| 7.7 | The effect of gain sag and walk is illustrated in spectra of the photometric standard G191-B2B taken immediately before and immediately after the largest change in detector high voltage. Top: Although the S/N is different in the two spectra, notice how walk subtly shifts the position and shape of the prominent interstellar absorption lines. Bottom: The narrow "P Cygni" morphology of lines in black is a diagnostic of gain-sag in regions of the detector that have been heavily overexposed. In this case, the over-exposure is quite localized due to the presence of strong airglow lines of N I and O I. Gain sag in these regions causes the positions of photon events to be misregistered, which produces the tell-tale morphology. Raising the high-voltage compensates for the gain sag, and the strange morphology disappears. However, only a crude walk correction is available for HIST spectra. The correction for these effects is much better for data obtained in TTAG mode. | ||
| 7.8 | Use of FP splits to achieve S/N ratios above 30. Top: Portion of the LiF1A spectrum for target HD220057. These observations used the FP split technique in order to achieve S/N ratios ~40. Most sharp absorption lines are due to the presence of molecular hydrogen (H 2). Bottom: Portion of the LiF2A spectrum for target HD220057. Most sharp absorption lines are due to the presence of C I, corresponding fine-structure lines C I* and C I** and Fe II. The broader features have a stellar origin. | ||
| 7.9 | Left: Data from the IDF file for segment 1A of exposure D0640301006 obtained by observing target HD 91597 in LWRS. The spectral line curvature and their variable heights induced by astigmatism are obvious in LiF1A and SiC1A spectra. Note that colors are inverted so that absorption features appear as bright stripes. Right: Image (*ext.gif) of detector segment 1A once the data for exposure D0640301006 have been fully corrected for astigmatism, detector effects and other effects described in this Chapter. | ||
| 7.10 | Left: The FUSE spectrum of GD71 is plotted in the top panel, along with the synthetic spectrum (see text). All LWRS observations have been combined; data from each channel are color-coded as described below. The bottom panel shows the ratio of the data to the model. Right: Same as GD71, but for GD659. In all panels, the red trace represents LiF1, the brown trace represents LiF2, the purple trace represents SiC1, and the majenta trace represents SiC2. The model spectrum is plotted in green. | ||
| 7.11 | Same as Figure 7.10 above, but for GD153 (Left) and HZ43 (Right). | ||
| 7.12 | Same as Figure 7.10 above, but for GD246 (Left) and G191-B2B (Right). | ||
| 7.13 | A zoomed-view of the spectrum of GD71 is shown, as in Figure 7.10 above. The synthetic spectrum computed using Allard's line profiles is over-plotted in blue. The Lyman β, γ profiles appear too broad (see text), but the discrete absorption features do appear in the spectrum. | ||
| 7.14 | A zoomed-view of the spectrum of GD659 is shown, as in Figure 7.13 above. The quasi-molecular satellites are too weak to be apparent at this higher effective temperature. | ||
| 7.15 | A zoomed-view of the spectrum of HZ43 is shown, as in Figure 7.13 above. The discrete quasi-molecular features have essentially disappeared at this temperature, but the Lyman β and Lyman γ profiles are still measurably broader than in the nominal model (see text). | ||
| 7.16 | A zoomed view of a small region of the spectrum of G191-B2B is shown, illustrating the presence of numerous weak metal lines. Over half of the pixels shown are affected by absorption amounting to several percent of the continuum. | ||
| 7.17 | The effective area of the LiF1 channel through the LWRS aperture is shown in the left panel; each curve represents a different time during the mission. The dramatic drop shortward of 1000Å is caused by the decrease in transmission of the LiF layer applied to protect the Aluminum coating. The right panel shows the evolution of the LiF2 channel sensitivity. The sensitivity of LiF2B is substantially less than LiF2A, due to the low QE of the MCPs in detector 2B. | ||
| 7.18 | The effective area of the SiC1 and SiC2 channels through the LWRS aperture are shown in the left and right panels, respectively; each curve represents a different time during the mission. The sensitivity of SiC2B is much less than that of SiC2A due to the low QE of detector 2B. | ||
| 7.19 | This Figure shows the variations in LWRS LiF1 response over the course of the FUSE mission, as determined from relative changes in measured fluxes for the four primary monitoring stars. Each panel shows the variations for a 15-20Å portion of the spectrum. LiF1A is shown in the Left panel: the tight clustering of ratios about unity shows that the variations in sensitivity were well-corrected for LiF1A. LiF1B is shown in the Right panel: the wide scatter of points for four of the five spectral bins is due to the strong worm in LWRS LiF1B. | ||
| 7.20 | Same as Fig. 7.19 above, but for LiF2A and LiF2B. | ||
| 7.21 | Same as Fig. 7.19 above, but for SiC1A and SiC1B. | ||
| 7.22 | Same as Fig. 7.19 above, but for SiC2A and SiC2B. | ||
| 7.23 | Same as Figure 7.10 above, but for the MDRS spectrum of HZ43. | ||
| 7.24 | Same as Figure 7.10 above, but for the MDRS GD246 spectrum. The synthetic spectrum shown here was calculated with Teff=58,700K and logg=7.807 rather than the parameters shown in Table 7.5. The overall agreement in the shape of the spectrum is much better than that shown in Figure 7.12 for the nominal parameters. | ||
| 7.25 | Same as Figure 7.10 above, but for the MDRS spectrum of G191-B2B. | ||
| 7.26 | Residual wavelength errors in the LiF1 spectrum of the white dwarf KPD 0005+5106 observed through the FUSE LWRS aperture. Horizontal lines represent the width of a window over which wavelength errors differ by less than half a pixel. | ||
| F.1 | Residual wavelength errors in the LiF2 spectrum of the white dwarf KPD 0005+5106 observed through the FUSE LWRS aperture. Horizontal lines represent the width of a window over which wavelength errors differ by less than half a pixel. | ||
| F.2 | Residual wavelength errors in the SiC1 spectrum of the white dwarf KPD 0005+5106 observed through the FUSE LWRS aperture. Horizontal lines represent the width of a window over which wavelength errors differ by less than half a pixel. | ||
| F.3 | Residual wavelength errors in the SiC2 spectrum of the white dwarf KPD 0005+5106 observed through the FUSE LWRS aperture. Horizontal lines represent the width of a window over which wavelength errors differ by less than half a pixel. | ||
| F.4 | Residual wavelength errors in the LiF1 spectrum of the white dwarf KPD 0005+5106 observed through the FUSE MDRS aperture. Horizontal lines represent the width of a window over which wavelength errors differ by less than half a pixel. | ||
| F.5 | Residual wavelength errors in the LiF2 spectrum of the white dwarf KPD 0005+5106 observed through the FUSE MDRS aperture. Horizontal lines represent the width of a window over which wavelength errors differ by less than half a pixel. | ||
| F.6 | Residual wavelength errors in the SiC1 spectrum of the white dwarf KPD 0005+5106 observed through the FUSE MDRS aperture. Horizontal lines represent the width of a window over which wavelength errors differ by less than half a pixel. | ||
| F.7 | Residual wavelength errors in the SiC2 spectrum of the white dwarf KPD 0005+5106 observed through the FUSE MDRS aperture. Horizontal lines represent the width of a window over which wavelength errors differ by less than half a pixel. | ||
| F.8 | Residual wavelength errors in the LiF1 spectrum of the white dwarf KPD 0005+5106 observed through the FUSE HIRS aperture. Horizontal lines represent the width of a window over which wavelength errors differ by less than half a pixel. | ||
| F.9 | Residual wavelength errors in the LiF2 spectrum of the white dwarf KPD 0005+5106 observed through the FUSE HIRS aperture. Horizontal lines represent the width of a window over which wavelength errors differ by less than half a pixel. | ||
| F.10 | Residual wavelength errors in the SiC1 spectrum of the white dwarf KPD 0005+5106 observed through the FUSE HIRS aperture. Horizontal lines represent the width of a window over which wavelength errors differ by less than half a pixel. | ||
| F.11 | Residual wavelength errors in the SiC2 spectrum of the white dwarf KPD 0005+5106 observed through the FUSE HIRS aperture. Horizontal lines represent the width of a window over which wavelength errors differ by less than half a pixel. |