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XRT position for GRB 090817 enhanced by UVOT field astrometry
Data were analysed using HEASOFT version 6.32
| RA (J2000): | 04h 15m 51.78s (63.96574) |
|---|---|
| Dec (J2000): | +44° 07′ 43.4′′ (44.12872) |
| 90% Error radius: | 2.1′′ |
| Number of overlaps included in position: | 4 |
| Exposure time in final position: | 1767 s |
| Total number of overlaps considered: | 5 |
| Total overlap time: | 1971 s |
| Number of overlaps where no X-ray source was found: | 1 |
| Number of low-X-ray-count fits rejected: | 0 |
| Number of spurious fits rejected: | 0 |
| Number of bad astrometric corrections: | 0 |
| Number of outliers removed: | 0 |
For details of how these positions are produced, and why some positions are rejected, see the online documentation.
Final Position
The image below shows the UVOT field with the final, astrometrically corrected XRT refined position. The image is 50" to a side, and contains 786 s of data in the B filter.
Individual Frame Positions
The final position (magenta) is the weighted mean of 4 positions (green). A further 0 positions were rejected, either because they had too few photons to be secure (red) or because they are more than 3 sigma away from the mean position, more than 40" from the early mean, or had a problematic astrometric correction (yellow). The image is 50" to a side.
