# New Photometric Calibration of the Wide Field Camera 3 Detectors

**Authors:** A. Calamida, V. Bajaj, J. Mack, M. Marinelli, J. Medina, A. Pidgeon, V. Kozhurina-Platais, C. Shanahan, D. Som  
**arXiv:** [2205.13014](https://arxiv.org/abs/2205.13014)  
**Date:** 2022-05-25  
**Summary page:** https://www.summarizepaper.com/en/arxiv-id/2205.13014v1/

## Key points

- The Hubble Space Telescope's Wide Field Camera 3 (WFC3) detectors have received a new photometric calibration based on observations collected between 2009 and 2020.
- Four white dwarfs and a G-type star were used for the calibration.
- Time-dependent inverse sensitivities were calculated for the two WFC3-UVIS chips, UVIS1 and UVIS2, for all 42 full-frame filters after accounting for temporal changes in the observed count rates with respect to a reference epoch in 2009.
- New encircled energy values were derived for some filters, while improved sensitivity ratios were obtained by correcting for sensitivity changes over time.
- The updated inverse sensitivity values were derived using the new models for the primary standards and the new Vega reference flux.
- New flat fields were used in the case of the IR detector.
- The new calibration provides a photometric internal precision better than 0.5% for wide-, medium-, and narrow-band WFC3-UVIS filters, 5% for quad filters, and 1% for WFC3-IR filters.
- An updated set of photometric keywords are populated in the WFC3 image headers providing more accurate information about each image taken with this instrument as of October 15th, 2020.
- Researchers from Space Telescope Science Institute contributed to refining this important calibration tool that will help astronomers make more precise measurements of celestial objects observed by Hubble's WFC3 detectors.

## Summary

The Hubble Space Telescope's Wide Field Camera 3 (WFC3) detectors have received a new photometric calibration based on observations collected between 2009 and 2020. The calibration was performed using four white dwarfs, namely GRW+70~5824, GD~153, GD~71, G191B2B, and a G-type star, P330E. The updated calibrations include recent updates to the primary standard white dwarf models and a new reference flux for Vega. Time-dependent inverse sensitivities were calculated for the two WFC3-UVIS chips, UVIS1 and UVIS2, for all 42 full-frame filters after accounting for temporal changes in the observed count rates with respect to a reference epoch in 2009. New encircled energy values were derived for some filters, while improved sensitivity ratios were obtained by correcting for sensitivity changes over time. The updated inverse sensitivity values were derived using the new models for the primary standards and the new Vega reference flux. In addition, new flat fields were used in the case of the IR detector. The new calibration provides a photometric internal precision better than 0.5% for wide-, medium-, and narrow-band WFC3-UVIS filters, 5% for quad filters, and 1% for WFC3-IR filters. As of October 15th, 2020 an updated set of photometric keywords are populated in the WFC3 image headers providing more accurate information about each image taken with this instrument. The team behind this study includes researchers from Space Telescope Science Institute who contributed to refining this important calibration tool that will help astronomers make more precise measurements of celestial objects observed by Hubble's WFC3 detectors.