A New Transition Wolf-Rayet WN/C Star in the Milky Way
  We report the discovery of a new transition type Wolf-Rayet (WR) WN/C star in
the Galaxy. According to its coordinates (R.A., Dec)J2000 = 18h51m39.7s,
-05d34m51.1s, and the distance (7.11 kpc away from Earth) inferred from the
second Gaia, data release, it's found that WR 121-16 is located in the Far 3
kpc Arm, and it is 3.75 kpc away from the Galactic Center. The optical spectra
obtained by the Large Sky Area Multi-Object Fiber Spectroscopic Telescope
(LAMOST) and the 2.16 m telescope, both located at the Xinglong Observatory in
China, indicate that this is a WR star of the transitional WN7o/WC subtype. A
current stellar mass of about 7.1 M_solar, a mass-loss rate of M_dot =
10^(-4.97) M_solar/yr, a bolometric luminosity of log L/L_solar = 4.88, and a
stellar temperature of T_* = 47 kK are derived, by fitting the observed
spectrum with a specific Potsdam Wolf-Rayet (PoWR) model. The magnitude in
V-band varies between 13.95 and 14.14 mag, while no period is found. Based on
the optical spectra, the time domain data, and the indices of the astrometric
solution of the Gaia data, WR 121-16 is likely a transitional WN/C single star
rather than a WN+WC binary.
