Abstract
We analyze VLA-A observations made at 6 cm towards the Cepheus A star-forming region at three epochs: 1982.4, 1986.4, and 1990.2. We confirm that the thermal jet Cep A HW2 shows clear time variability in flux density and morphology. The radio-continuum source R5 is located about 0''.6 south of Cep A HW2 and seems to be the exciting source of the expanding bubble of H[2]O masers detected with the VLBA. Our maps of the region suggest that the source R5 was considerably weaker in 1982.4 than in the other two later epochs, showing for the first time evidence of its time variability. This variability is consistent with that expected for an expanding H II region. We speculate that the ``turn on'' of the source R5 between 1982.4 and 1986.4 may be related with an enhancement in the mass loss of the nearby thermal jet Cep A HW2 during the same epoch.
