  We argue that a type IIB Euclidean supergravity solution of the form
$\mathbb{R}\times S^1\times \mathbb{T}^8$ with imaginary self-dual $F_1$ flux
through $\mathbb{R}\times S^1$ belongs to the chain of $AdS_d\times S^d\times
\mathbb{T}^{10-2d}$ vacua with (imaginary) self-dual $F_d$ flux, where $d\leq
5$. Such vacua come from the near-horizon of D$(d-2)$/D$(8-d)$ branes and are
supersymmetric for odd values of $d$. For $d=1$ we speculate that the hallmark
of conformal symmetry for the matrix model dual is a vanishing free energy. The
matrix dual was recently constructed by arXiv:2101.01732 by adding matrix
interactions coming from strings stretching between the D$(-1)$ and D$7$ branes
to the IKKT matrix model. We find that the corresponding supergravity solution
indeed has vanishing on-shell action. Specific $F_5$ fluxes need to be switched
on as a consequence of (a T-dual version of) the Hanany-Witten effect.
