A Swift Fix for Nuclear Outbursts

TL;DR

This paper updates Swift UV data calibration, re-analyzes TDE and nuclear outburst observations, and refines the understanding of their luminosity decay relationship with improved accuracy.

Contribution

It provides corrected UV photometry data and re-evaluates the properties and light curves of nuclear outbursts, including TDEs, with updated calibration and analysis methods.

Findings

Recalibrated Swift UV data reduces systematic errors.

Recomputed host galaxy properties and transient magnitudes.

Confirmed the luminosity decay relationship with less scatter.

Abstract

In November 2020, the Swift team announced an update to the UltraViolet and Optical Telescope calibration to correct for the loss of sensitivity over time. This correction affects observations in the three near ultraviolet (UV) filters, by up to 0.3 mag in some cases. As UV photometry is critical to characterizing tidal disruption events (TDEs) and other peculiar nuclear outbursts, we re-computed published Swift data for TDEs and other singular nuclear outbursts with Swift photometry in 2015 or later, as a service to the community. Using archival UV, optical, and infrared photometry we ran host SED fits for each host galaxy. From these, we computed synthetic host magnitudes and host-galaxy properties. We calculated host-subtracted magnitudes for each transient and computed blackbody fits. In addition to the nuclear outbursts, we include the ambiguous transient ATLAS18qqn (AT2018cow), which has been classifed as a potential TDE on an intermediate mass black hole. Finally, with updated bolometric light curves, we recover the relationship of \citet{hinkle20a}, where more luminous TDEs decay more slowly than less luminous TDEs, with decreased scatter as compared to the original relationship.