# A Flaring AGN In a ULIRG candidate in Stripe 82

## TL;DR

This paper reports the discovery of a mid-infrared variable AGN within a ULIRG candidate in Stripe 82, showing long-term variability likely due to accretion rate changes, and suggests it is a composite AGN/starburst galaxy.

## Contribution

First identification of a flaring AGN in a ULIRG candidate in Stripe 82 with detailed analysis of its variability and host galaxy properties.

## Key findings

- Detected a twofold mid-infrared variability over 8 years.
- Estimated the host galaxy's star formation rate at ~70 M_sun/year.
- Suggested the variability is due to accretion rate changes near the AGN.

## Abstract

We report the discovery of a mid-infrared variable AGN which is hosted by an ultraluminous infrared galaxy (ULIRG) candidate in the Sloan Stripe 82 field. \textit{WISE} \textit{J030654.88+010833.6} is a red, extended galaxy, which we estimate to be at a photometric redshift of 0.28 $\leq$ z $\leq$ 0.31, based on its optical and near-infrared spectral energy distribution (SED). The factor of two variability over 8 years seen in the \textit{WISE} 3.4 and 4.6 $\mu$m wavelength channels is not clearly correlated with optical variability in archival data. Based on our estimation of the physical parameters of the host galaxy, \textit{J030654.88+010833.6} is possibly a composite AGN/starburst ULIRG in a phase where high star formation $\sim$ 70 M$_{\odot}$ year$^{-1}$ is occurring. Our estimate of the black hole mass to stellar mass ratio also appears to be consistent with that of broad-line AGN in the local universe. The long-term variability of \textit{J030654.88+010833.6} as seen in the \textit{WISE} \textit{W1} and \textit{W2} light curves is likely due to variations in the accretion rate, with the energy being reprocessed by dust in the vicinity of the AGN.