Step-by-Step APT Guide for NIRCam Time-Series Imaging Science Use Case

Instructions are provided for filling out the APT observing template for the JWST NIRCam Time Series Imaging Observations of HAT-P-18 Science Use Case.

Astronomer's Proposal Tool

 Main Article: Astronomer's Proposal Tool     

We now construct an APT file that will execute our desired observations. We will use the NIRCam imaging time series template to specify a single-exposure observation with a real-time duration of 3 × T14 (2.71 hours) + 1 hour for detector settling, to be conservative. We enter the following values in APT:

  • Input fixed target name HAT-P-18, resolved with SIMBAD.

  • NIRCam time-series imaging template.

    • SUB64P subarray.

    • Filters: F210M and F444W.

    • Readout: RAPID, with 10 groups/integration and 60,000 integrations in 1 exposure: a bit over 9 hours covers 3 times its 2.71 hour transit time.

  • The long exposure is allowed but gives a warning that the high gain antenna may be moved during the exposure.

  • Special requirements: PHASE = 0.43854 to 0.43927, with period = 5.508023 days and ZERO-PHASE = 2454715.02174 HJD.

Hartman et al. (2011), predict that the HAT-P-18 b secondary eclipse will come 2.63 days after transit, at an equivalent 0 eccentricity PHASE of 0.4772, given its 5.508 days period. We will center the schedule of the exposure to start 5.07 hours before the predicted secondary eclipse time, allowing for 1 hour of detector settling and one transit time before the predicted time of the secondary eclipse start. This corresponds to PHASE 0.4385 and will allow us to catch the secondary eclipse if it occurs within ±1 transit time (2.71 hours) of the predicted value. We thus set the special requirement to start the exposure at PHASE 0.4385 to 0.4392 with period 5.508023 days and zero-phase 2454715.02174 HJD, just outside of the minimum allowed 5 minute tolerance.

A check with the Visit Planner shows that the observations in schedulable. A visualization in Aladin using the 2MASS image shows no nearby bright stars, so the observations will not suffer from confusion.

The total program length is 12.56 hours, including 8.23 hours of science time, for an efficiency of 0.66.

Figure 1. APT observation setup

Screenshot of APT NIRCam time-series template with this program's selected observation parameters.

The APT file for this program can be downloaded here: NIRCam_imaging_time_series_example.aptx



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