Cluster membership for the long period Cepheid calibrator SV Vul
  Classical Cepheids represent the first step of the distance scale ladder.
Claims of tension between the locally calculated Hubble constant and the values
deduced from $Planck$'s results have sparked new interest in these distance
calibrators. Cluster membership provides an independent distance measurement,
as well as astrophysical context for studies of their stellar properties. Here
we report the discovery of a young open cluster in the vicinity of SV Vul, one
of the most luminous Cephedis known in the Milky Way. $Gaia$ DR2 data show that
SV Vul is a clear astrometric and photometric member of the new cluster, which
we name Alicante 13. Although dispersed, Alicante 13 is moderately well
populated, and contains three other luminous stars, one early-A bright giant
and two low-luminosity red supergiants. The cluster is about 30 Ma old at a
nominal distance of 2.5 kpc. With this age, SV Vul should have a mass around
$10\:$M$_{\odot}$, in good accordance with its luminosity, close to the highest
luminosity for Cepheids allowed by recent stellar models.
