Multi-epoch SMA observations of the L1448C(N) protostellar SiO jet

Abstract

L1448C(N) is a young protostar in Perseus, driving an outflow and an extremely high-velocity (EHV) molecular jet. We present multi-epoch observations of SiO $J=8-7$, CO $J=3-2$ lines, and 345 GHz dust continuum toward L1448C(N) in 2006, 2010, and 2017 with the Submillimeter Array. The knots traced by the SiO line show the averaged proper motion is $\sim 0^{\prime \prime }.06\mathrm{y}{\mathrm{r}}^{-1}$ and $\sim 0^{\prime \prime }.04\mathrm{y}{\mathrm{r}}^{-1}$ for the blue- and red-shifted jet, respectively. The corresponding transverse velocities are $\sim 78\mathrm{km}{\mathrm{s}}^{-1}$ (blueshifted) and $\sim 52\mathrm{km}{\mathrm{s}}^{-1}$ (redshifted). Together with the radial velocity, we found the inclination angle of the jets from the plane of the sky to be $\sim 34$° for the blueshifted jet and $\sim 46$° for the redfshifted jet. Given the new inclination angles, the mass-loss rate and mechanical power were refined to be $\sim 1.8\times 10^{-6}{M}_{\odot }$ and $\sim 1.3L_{\odot }$, respectively. In the epoch of 2017, a new knot is detected at the base of the redshifted jet. We found that the mass-loss rate of the new knot is three times higher than the averaged mass-loss rate of the redshifted jet. Besides, continuum flux has enhanced by $\sim 37\%$ between 2010 and 2017. These imply that the variation of the mass-accretion rate by a factor of $\sim 3$ has occurred in a short timescale of $\sim 10-20$ yr. In addition, a knot in the downstream of the redshifted jet is found to be dimming over the three epochs.

16 pages, 13 figures

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