Is there really a debris disc around ${\zeta }^2\mathrm{R}\mathrm{e}\mathrm{t}\mathrm{i}\mathrm{c}\mathrm{u}\mathrm{l}\mathrm{i}$ ?

The presence of a debris disc around the Gyr-old solar-type star ${\zeta }^2\mathrm{R}\mathrm{e}\mathrm{t}\mathrm{i}\mathrm{c}\mathrm{u}\mathrm{l}\mathrm{i}$ was suggested by the $Spitzer$ infrared excess detection. Follow-up observations with $Herschel$/PACS revealed a double-lobed feature, that displayed asymmetries both in brightness and position. Therefore, the disc was thought to be edge-on and significantly eccentric. Here we present ALMA/ACA observations in Band 6 and 7 which unambiguously reveal that these lobes show no common proper motion with ${\zeta }^2\mathrm{R}\mathrm{e}\mathrm{t}\mathrm{i}\mathrm{c}\mathrm{u}\mathrm{l}\mathrm{i}$. In these observations, no flux has been detected around ${\zeta }^2\mathrm{R}\mathrm{e}\mathrm{t}\mathrm{i}\mathrm{c}\mathrm{u}\mathrm{l}\mathrm{i}$ that exceeds the $3\sigma$ levels. We conclude that surface brightness upper limits of a debris disc around ${\zeta }^2\mathrm{R}\mathrm{e}\mathrm{t}\mathrm{i}\mathrm{c}\mathrm{u}\mathrm{l}\mathrm{i}$ are $5.7\mu \mathrm{J}\mathrm{y}\mathrm{/}\mathrm{a}\mathrm{r}\mathrm{c}\mathrm{s}\mathrm{e}{\mathrm{c}}^2$ at 1.3 mm, and $26\mu \mathrm{J}\mathrm{y}\mathrm{/}\mathrm{a}\mathrm{r}\mathrm{c}\mathrm{s}\mathrm{e}{\mathrm{c}}^2$ at 870 microns. Our results overall demonstrate the capability of the ALMA/ACA to follow-up $Herschel$ observations of debris discs and clarify the effects of background confusion.