Speaker
Description
AT2021lwx/ZTF20abrbeie, also known as Scary Barbie, is an ultra-luminous optically discovered transient at z $\sim$ 1 with no previously cataloged host. It is the most energetic non-jetted transient ever observed, exhibiting a single optical brightening by a factor of over 100 to an optical luminosity of $few \times 10^{46}$ erg s$^{-1}$, surpassing any known optical transient. Here, we present SRG/eROSITA, XMM-Newton, and Chandra X-ray observations of the source throughout its evolution.
We demonstrate that the X-ray spectral shape and light curve, along with multi-wavelength data, indicate that the source is an Active Galactic Nucleus (AGN) rather than a tidal disruption event (TDE, as suggested by the discovery authors). Specifically, it has all the characteristics of the Narrow Line Seyfert 1 class of AGN. Through comprehensive spectral energy distribution (SED) fitting from infrared to X-rays, we show that the bolometric luminosity of the source has varied from less than $10^{44}$ erg s$^{-1}$ to a peak of approximately a few $\times 10^{47}$ erg s$^{-1}$. The peak bolometric luminosity is observationally and theoretically inconsistent with a TDE, but it makes the source, for a brief period, one of the brightest AGNs in the z $\leq$ 1 universe. This work demonstrates the fundamental role of X-ray data in understanding astronomical transients' nature.
