Title: Physical properties of the first spectroscopically confirmed red supergiant stars in the Sculptor Group galaxy NGC 55,
Abstract: We present K-band Multi-Object Spectrograph (KMOS) observations of 18 Red
Supergiant (RSG) stars in the Sculptor Group galaxy NGC 55. Radial velocities
are calculated and are shown to be in good agreement with previous estimates,
confirming the supergiant nature of the targets and providing the first
spectroscopically confirmed RSGs in NGC 55. Stellar parameters are estimated
for 14 targets using the $J$-band analysis technique, making use of
state-of-the-art stellar model atmospheres. The metallicities estimated confirm
the low-metallicity nature of NGC 55, in good agreement with previous studies.
This study provides an independent estimate of the metallicity gradient of NGC
55, in excellent agreement with recent results published using hot massive
stars. In addition, we calculate luminosities of our targets and compare their
distribution of effective temperatures and luminosities to other RSGs, in
different environments, estimated using the same technique.