The Swift UVOT grism calibration and example spectra

TL;DR

This paper details the calibration process of the UVOT grisms, providing spectral resolution data, correction methods for detector pile-up, and example spectra to demonstrate their capabilities.

Contribution

It presents the complete calibration of UVOT grisms, including resolution metrics, pile-up correction techniques, and example spectra, which were not previously available.

Findings

UV grism spectral resolution of 75 at 2600 Å

Visible grism spectral resolution of 100 at 4000 Å

Developed correction for coincidence loss in spectra

Abstract

The calibration of the two UVOT grisms which provide slitless spectroscopy in the 170-500 nm (UV grism) and 295-660 nm (visible grism) ranges has been completed. The UV grism has a spectral resolution ($\lambda/\Delta\lambda$) of 75 at $\lambda$2600 \AA\ for source magnitudes of u=10-16 mag, while the visible grism has a spectral resolution of 100 at $\lambda$4000 \AA\ for source magnitudes of b=12-17 mag. For brighter spectra, coincidence loss (pile-up) occurs in the photon-counting detector. A correction for the coincidence loss in grism spectra has been developed, and limits have been established above which that correction fails. After discussing the UVOT grisms and their calibration, an illustration is given of the breadth of the UVOT grism spectroscopy.