  Large, complex, active regions may produce multiple flares within a certain
period of one or two days. These flares could occur in the same location with
similar morphologies, commonly referred to as homologous flares. In 2011
September, active region NOAA 11283 produced a pair of homologous flares on the
6th and 7th, respectively. Both of them were white-light (WL) flares, as
captured by the Helioseismic and Magnetic Imager (HMI) onboard the Solar
Dynamics Observatory in visible continuum at 617.3 nm which is believed to
originate from the deep solar atmosphere.We investigate the WL emission of
these X-class flares with HMIs seeing-free imaging spectroscopy. The durations
of impulsive peaks in the continuum are about 4 minutes. We compare the WL with
hard X-ray (HXR) observations for the September 6 flare and find a good
correlation between the continuum and HXR both spatially and temporally. In
absence of RHESSI data during the second flare on September 7, the derivative
of the GOES soft X-ray is used and also found to be well correlated temporally
with the continuum. We measure the contrast enhancements, characteristic sizes,
and HXR fluxes of the twin flares, which are similar for both flares,
indicating analogous triggering and heating processes. However, the September 7
flare was associated with conspicuous sunquake signals whereas no seismic wave
was detected during the flare on September 6. Therefore, this comparison
suggests that the particle bombardment may not play a dominant role in
producing the sunquake events studied in this paper.
