  $\tau^{9}$ Eri is a Bp star that was previously reported to be a single-lined
spectroscopic binary. Using 17 ESPaDOnS spectropolarimetric (Stokes $V$)
observations we identified the weak spectral lines of the secondary component
and detected a strong magnetic field in the primary. We performed orbital
analysis of the radial velocities of both components to find a slightly
eccentric orbit ($e= 0.129$) with a period of $5.95382(2)$ days.
  The longitudinal magnetic field ($B_\ell$) of the primary was measured from
each of the Stokes $V$ profiles, with typical error bars smaller than 10 G.
Equivalent widths (EWs) of LSD profiles corresponding to only the Fe lines were
also measured. We performed frequency analysis of both the $B_\ell$ and EW
measurements, as well as of the Hipparcos, SMEI, and TESS photometric data. All
sets of photometric observations produce two clear, strong candidates for the
rotation period of the Bp star: 1.21 days and 3.82 days. The $B_\ell$ and EW
measurements are consistent with only the 3.82-day period. We conclude that HD
25267 consists of a late-type Bp star (M= $3.6_{-0.2}^{+0.1} M_\odot$, T=
$12580_{-120}^{+150}$ K) with a rotation period of 3.82262(4) days orbiting
with a period of 5.95382(2) days with a late-A/early-F type secondary companion
(M= $1.6\pm 0.1 M_\odot$, T= $7530_{-510}^{+580}$ K). The Bp star's magnetic
field is approximately dipolar with $i= 41\pm 2^{\circ}$, $\beta= 158\pm
5^{\circ}$ and $B_{\rm d}= 1040\pm 50$ G. All evidence points to the strong
$1.209912(3)$ day period detected in photometry, along with several other
weaker photometric signals, as arising from $g$-mode pulsations in the primary.
