Table 1
Log of the two sets of SPHERE observations of HR 4796 A.
| Date | Set-up | DITa (s) × | Par. | Seeing | Coh. | Wind | True | Platescaled |
| NDIT × NEXP | angleb (°) | (′′) | timec (ms) | (m/s) | northd (°) | (mas/pixel) | ||
|
|
||||||||
| 2014/05/19 | IRDIS H | 3 × 15 × 32 | 8.1; 39.3 | 0.8; 1.2 | 2.3; 1.0 | 10.5 | −134.87 ± 0.6 | 12.238 ± 0.020 |
|
|
||||||||
| 2015/02/02 | IRDIS H2H3 | 32 × 8 × 14 | −9.3; 39.4 | 0.6; 0.7 | 11 | 3 | −134.155 ± 0.006 | 12.257 ± 0.03 |
| IFS YJ | 64 × 4 × 9 | −33.65e ± 0.13 | 7.46 ± 0.02 | |||||
Notes.
Parallactic angle at the start and end of the observations. For the April 2014 observations, not all the available field rotation was used (see Sect. 2 for details).
The coherence time τ0 is defined as τ0 = 0.31r0/v, where r0 is the Fried parameter measured by the DIMM and v is the maximum of the wind speed measured at30 m height, and 0.4 times the predicted wind speed at an altitude of 400 mbar (Sarazin & Tokovinin 2002).
The calibration of the true north and platescale are detailed in Maire et al. (2016). The true north indicated here includes the offset between the pupil-stabilised and field-stabilised mode.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.