Optical Spectroscopy of the ULX-Associated Nebula MF16

Understand

We present the results of optical panoramic and long-slit spectroscopy of the nebula MF16 associated with the Ultraluminous X-ray Source NGC6946 ULX-1.

• More than 20 new emission lines are identified in the spectra.
• Using characteristic line ratios we find the electron density n_e ~ 600cm^{-3}, electron temperature in the range from ~9000K to ~20 000K (for different diagnostic lines) and the total emitting gas mass M ~ 900 Msolar.
• We also estimate the interstellar extinction towards the nebula as A_V = 1.m54 somewhat higher than the Galactic absorption.