Assume all the capacitors to be discharged at first. The output of the op-amp Vo at node c is +Vsat initially. At node a, a voltage of +β Vsat is formed due to voltage division where formula_12. The current that flows from nodes c and b to ground charges the capacitor C towards +Vsat. During this charging period, the voltage at b becomes greater than +β Vsat at some point. The voltage at inverting terminal will be greater than the voltage at the non-inverting terminal of the op-amp. This is a comparator circuit and hence, the output becomes -Vsat. The voltage at node a becomes -βVsat due to voltage division. Now the capacitor discharges towards -Vsat. At some point, the voltage at b becomes less than -β Vsat. The voltage at the non-inverting terminal will be greater than the voltage at the inverting terminal of the op-amp. So, the output of the op-amp is +Vsat. This repeats and forms a free-running oscillator or an astable multivibrator.