Abstract. Let
$H$
be the Hilbert class field of a
$\text{CM}$
number field
$K$
with maximal totally real subfield
$F$
of degree
$n$
over
$\mathbb{Q}$
. We evaluate the second term in the Taylor expansion at
$s\,=\,0$
of the Galois-equivariant
$L$
-function
${{\Theta }_{{{S}_{\infty }}\,}}\left( s \right)$
associated to the unramified abelian characters of
$\text{Gal}\left( H/K \right)$
. This is an identity in the group ring
$\mathbb{C}\left[ \text{Gal}\left( H/K \right) \right]$
expressing
$\Theta _{{{S}_{\infty }}}^{(n)}\,\left( 0 \right)$
as essentially a linear combination of logarithms of special values
$\left\{ \Psi ({{z}_{\sigma }}) \right\}$
, where
$\Psi :\,{{\mathbb{H}}^{n}}\,\to \,\mathbb{R}$
is a Hilbert modular function for a congruence subgroup of
$S{{L}_{2}}\left( {{\mathcal{O}}_{F}} \right)$
and
$\left\{ {{z}_{\sigma }}\,:\,\sigma \,\in \,\text{Gal}\left( H/K \right) \right\}$
are
$\text{CM}$
points on a universal Hilbert modular variety. We apply this result to express the relative class number
${{h}_{H}}/{{h}_{K}}$
as a rational multiple of the determinant of an
$\left( {{h}_{K}}\,-\,1 \right)\,\times \,\left( {{h}_{K}}\,-\,1 \right)$
matrix of logarithms of ratios of special values
$\Psi ({{z}_{\sigma }})$
, thus giving rise to candidates for higher analogs of elliptic units. Finally, we obtain a product formula for
$\Psi ({{z}_{\sigma }})$
in terms of exponentials of special values of
$L$
-functions.