IACHEC 2020/2021 Pandemic Report

TL;DR

This report summarizes IACHEC's activities and calibration progress for high-energy astrophysics missions during 2020-2021, highlighting cross-calibration results and ongoing challenges in instrument consistency.

Contribution

It provides an updated overview of cross-calibration status and issues among major X-ray observatories, based on virtual meetings during the pandemic period.

Findings

Good agreement between NuSTAR and Swift in most energy ranges.

Persistent calibration discrepancies between XMM-Newton and Chandra.

Ongoing progress in NICER cross-calibration.

Abstract

In this report we summarize the activities of the International Astronomical Consortium for High Energy Calibration (IACHEC) and the work done since the last in-person meeting in Japan (Shonan Village Center), May 2019, through two virtual meetings that were held in November 2020 and May 2021. The on-line only meetings divided the contents of the usual in-person workshop between mission updates and working group updates. The November meeting was dedicated to mission calibration updates and the current status of the cross-calibration between NuSTAR, Swift, and NICER, which frequently join together in observations of bright transients, and a review of the XMM-Newton and Chandra cross-calibration. Results between \nustar\ and \swift\ overall show good agreement, but issues persist in the overlap region 3--5 keV for bright source with large dust scattering halos. The NICER cross-calibration is still progressing and evolving, while for the XMM-Newton and Chandra cross-calibration systematic differences both in the absolute flux and spectral shape determination still exists on different classes of sources. The meeting in May was focused on the Working Group progress and reports summarized here.