An Orbit Fit to Likely Hermus Stream Stars
  We selected blue horizontal branch (BHB) stars within the expected distance
range and sky position of the Hermus Stream from Data Release 10 of the Sloan
Digital Sky Survey. We identify a moving group of $19$ BHB stars that are
concentrated within two degrees of the Hermus Stream, between $10$ and $14$ kpc
from the Sun. The concentration in velocity is inconsistent with a Gaussian
distribution with 98% confidence (2.33 sigma).The stars in the moving group
have line-of-sight velocities of v$_{\rm gsr} \sim 50$ km s$^{-1}$, a velocity
dispersion of $\sigma_v\lesssim11$ km s$^{-1}$, a line-of-sight depth of $\sim
1$ kpc, and a metallicity of [Fe/H] $=-2.1 \pm 0.4$. The best-fit orbit has a
perigalacticon of $\sim4$ kpc, apogalacticon of $\sim 17$ kpc, orbital period
of $\sim247$ Myr, eccentricity $e = 0.62$, and inclination $i \sim75^\circ$
from $b=90^\circ$. The BHB stars in the stream are estimated to be $12$ Gyr
old. An N-body simulation of a mass-follows-light ultrafaint dwarf galaxy with
mass $10^6M_{\odot}$ and radius $40$ pc is consistent with the observed
properties. The properties of the identified moving group of 19 BHB stars are
close enough to those of the Hermus Stream (which is traced predominantly in
turnoff stars) that we find it likely that they are associated. If that is the
case, then our orbit fit would imply that there is no relationship between the
Hermus and Phoenix streams, as previously proposed.
