Table 1
GRAVITY observation log of the target HIP 99770 b and of the swap calibrator HD 196885 AB.
| Target | Start (UTC) | End (UTC) | NEXP/NDIT/DIT(s) Airmass | τ0 (ms) | Seeing (arcsec) | Fibre placement | γ | ||
|---|---|---|---|---|---|---|---|---|---|
| ΔRA (mas) | ΔDec (mas) | ||||||||
| 31st May | |||||||||
| HIP 99770 A | 09:19:59 | 09:25:04 | 2/96/0.5 | 2.19 | 8.2 | 0.62 | 0.0 | 0.0 | 100% |
| HIP 99770 b | 09:27:53 | 09:39:12 | 2/32/10 | 2.25 | 7.2 | 0.63 | 323.87 | −272.72 | 96.3% |
| 2nd July 2023 | |||||||||
| HIP 99770 b | 07:05:36 | 07:32:34 | 3/12/30 | 2.22 | 2.9 | 0.55 | 323.6 | −261.6 | 99.8% |
| HD 196885 AB | 07:43:03 | 07:56:17 | 4/32/3 | 1.31 | 2.4 | 0.91 | 285.0 | 430.0 | 44.8% |
Notes. The reported start and end times indicate the duration of the full observation, consisting of a series of NEXP exposures, each subdivided into NDIT detector integrations per exposure, that were taken over a duration of DIT. τ0 is the mean atmospheric coherence time during the observation, and the fibre placement columns display where the centre of the science fibre was located relative to the host star at the time of observation. The positions are given as on-sky Cartesian coordinates in separation relative to the host star along the right ascension axis, ΔRA, and the declination axis, ΔDec. The last column lists the normalised coupling efficiency, γ, by which the respective contrast spectrum needs to be divided to correct for the throughput loss resulting from an imperfect alignment of the fibre centre and the companion (see Appendix C).
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