Confirmation of a Stellar Microjet in the Rosette H<scp>ii</scp>Region (NGC 2244)

A possible microjet from a low-mass but young star, which has already shed its cocoon, could be rendered observable by the Lyman photon flux in the interior of the Rosette Nebula. Outside this environment it may not have been observable at optical wavelengths. The kinematics of this proposed monopolar microjet from an F8 Ve star have been investigated by spatially resolved, long-slit, spectral observations with the Manchester Echelle Spectrometer on the San Pedro Martir telescope (Mexico). The flow is shown to be approaching to give a radial velocity difference from the host nebula of -56 km s-1. An outflow velocity of, at the most, a few hundreds of km s-1 is therefore indicated. If the flow velocity is taken as 200 km s-1, which is found in other microjets, then this jet&#39;s inclination to the sky is ≈16&#176;. The mass in the outflowing ionized gas is estimated from the surface brightness of the Hα emission as ≈6 &#215; 1027 g to give an estimated mass-loss rate of 10-8 M⊙ yr-1, which, along with the detection of the outflow velocity, confirms its microjet identification even though an uncertain filling factor was used in these calculations. The hottest cluster star, which is also in the neighborhood of the microjet, is found alone to emit marginally sufficient Lyman photons to account for the ionization of the jet, although direct observations of the local electron density from optical line ratios are required to confirm this point conclusively.