Photometric study of the SMCNOD using variable stars from the OGLE-IV
  survey
  We present a study of a recently discovered stellar overdensity near the
northern edge of the Small Magellanic Cloud (SMCNOD). We exploited variable
stars from the fourth release of the Optical Gravitational Lensing Experiment
(OGLE). We used mainly pulsating variable stars and investigated their
potential association with the SMCNOD using their spatial distribution and
distances. We found four rather spatially concentrated anomalous Cepheids and
eight evenly dispersed RR~Lyrae stars to be most likely members of this
overdensity. The anomalous Cepheids inside the SMCNOD trace possible
intermediate-age population with ages ranging between $2-4.5$ Gyr. The age
distribution of anomalous Cepheids seems to be in a good agreement with the age
distribution of anomalous Cepheids in the SMC. Using empirical relations for
RR~Lyrae stars we determined the median metallicity for a possible old
population in the SMCNOD to be $\rm [Fe/H]_{\rm SMCNOD}=-1.71\pm0.21$ dex,
which is in agreement with median metallicity of the old SMC population. The
density profile for anomalous Cepheids shows a small anomaly at the position of
the SMCNOD, on the other hand, RR~Lyrae variables show no such deviation. The
probability of finding the observed number of variable stars at the location of
the SMCNOD by chance is very low for anomalous Cepheids (0.7 %) but high for
RR~Lyrae stars (13.0 %). Based on its variable stars content, we thus confirm
the presence of a modest overdensity in intermediate-age stars in the SMCNOD
and conclude that it probably has its origin in the SMC rather than to be the
remnant of an accreted dwarf galaxy.
