1 research outputs found
Optical Spectroscopy of the environment of a ULX in NGC 7331
Optical photometric and spectroscopic data are presented that show an
association of an ultraluminous X-ray source in NGC 7331 with a young star
cluster of mass 1.1e5 solar masses and age 4.25 Myr. If the ULX is part of the
bright stellar cluster, then the mass of the progenitor of the compact accretor
must have been greater than about 40-50 solar masses in order to already have
evolved through the supernova stage to a compact object. The companion star is
also likely an evolved massive star. The emission line spectrum of the nebula
surrounding the cluster can be interpreted as a result of photoionization by
the cluster OB stars with an additional source of shock excitation producing
strong [SII], [OI] and NII lines. This additional source appears to be as much
as five times more powerful than the supernovae and stellar winds in the
cluster can provide. Additional mechanical energy input associated with the ULX
itself can help explain the residual shock excited line luminosities of the
emission region.Comment: 17 pages, accepted to Ap