Ring-averaged central velocity of the NH₃ (1, 1) (blue circles)and (2, 2) (red circles) lines in the Guitar core in L1287. The error bars are the rms of the values inside each ring. The central dashed line is the best fit of the infall hallmark model for a central mass of 2.1 M_⊙, and the horizontal dotted line is the best-fit systemic velocity, V_sys = −18.67 km s⁻¹. The fits for central masses of 1.1 and 3.4 M_⊙ are also shown.