  We present the first maps of cyanoacetylene isotopologues in Titan's
atmosphere, including H$^{13}$CCCN and HCCC$^{15}$N, detected in the 0.9 mm
band using the Atacama Large Millimeter/submillimeter array (ALMA) around the
time of Titan's (southern winter) solstice in May 2017. The first
high-resolution map of HC$_3$N in its $v_7=1$ vibrationally excited state is
also presented, revealing a unique snapshot of the global HC$_3$N distribution,
free from the strong optical depth effects that adversely impact the
ground-state ($v=0$) map. The HC$_3$N emission is found to be strongly enhanced
over Titan's south pole (by a factor of 5.7 compared to the north pole),
consistent with rapid photochemical loss of HC$_3$N from the summer hemisphere
combined with production and transport to the winter pole since the April 2015
ALMA observations. The H$^{13}$CCCN/HCCC$^{15}$N flux ratio is derived at the
southern HC$_3$N peak, and implies an HC$_3$N/HCCC$^{15}$N ratio of $67\pm14$.
This represents a significant enrichment in $^{15}$N compared with Titan's main
molecular nitrogen reservoir, which has a $^{14}$N/$^{15}$N ratio of 167, and
confirms the importance of photochemistry in determining the nitrogen isotopic
ratio in Titan's organic inventory.
