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arXiv · 2610.32746

Systematic Slopes in NIRSpec BOTS Observations

Munazza K. Alam·Leonardo Ubeda·Sophie von Coelln·Ceiligh Cacho-Nagrete·Nestor Espinoza
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Abstract

We investigate empirical white light and spectroscopic trends in the temporal systematic slopes seen in NIRSpec Bright Object Time Series (BOTS) observations. Using a sample of 14 high-resolution G395H (dispersed across both the NRS1 and NRS2 detectors) and 10 low-resolution Prism (dispersed across NRS1 only) transit light curves, we measured the visit-long, pre-transit, and post-transit slopes. For the G395H white light curves, we find a correlation between the G395H NRS1 systematic slope and the host star magnitude, as well as the number of groups per integration. We also note that the systematic slopes vary with time over the course of a given time-series, with steeper pre-transit slopes compared to post-transit. These trends in the white light slopes are not apparent for G395H NRS2 or Prism. At the spectroscopic light curve level, the NRS1 and Prism slopes show a distinct wavelength-dependent signature across the full sample with the largest slopes between ~3-3.4 microns. At these wavelengths, the brightest targets display the strongest chromatic slope signatures. The NRS2 slopes show no apparent chromaticity across the full sample.

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Munazza K. Alam, Leonardo Ubeda, Sophie von Coelln, Ceiligh Cacho-Nagrete, Nestor Espinoza. 2026-10-23. Systematic Slopes in NIRSpec BOTS Observations. https://arxiv.org/abs/2610.32746

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