Late time HST UV and optical observations of AT~2018cow: extracting a cow from its background
Anne Inkenhaag, Peter G. Jonker, Andrew J. Levan, Ashley A. Chrimes,, Andrew Mummery, Daniel A. Perley, Nial R. Tanvir

TL;DR
This study analyzes late-time HST UV and optical data of AT2018cow, revealing fading emission, complex background challenges, and potential TDE origins, with implications for understanding its nature and environment.
Contribution
It provides the first detailed late-time photometric analysis of AT2018cow using HST data, exploring the transient's fading behavior and possible tidal disruption event origin.
Findings
Fading UV and optical emission observed over time.
Complex background complicates precise photometry.
TDE-like model fits suggest a black hole of about 10^3.2 solar masses.
Abstract
The bright, blue, rapidly evolving AT2018cow is a well-studied peculiar extragalactic transient. Despite an abundance of multi-wavelength data, there still is no consensus on the nature of the event. We present our analysis of three epochs of Hubble Space Telescope (HST) observations spanning the period from 713-1474 days post burst, paying particular attention to uncertainties of the transient photometry introduced by the complex background in which AT2018cow resides. Photometric measurements show evident fading in the UV and more subtle but significant fading in the optical. During the last HST observation, the transient's optical/UV colours were still bluer than those of the substantial population of compact, young, star-forming regions in the host of AT2018cow, suggesting some continued transient contribution to the light. However, a compact source underlying the transient would…
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Taxonomy
TopicsAstrophysical Phenomena and Observations · Gamma-ray bursts and supernovae · Astrophysics and Star Formation Studies
