The interesting object G76.9+1.0 was detected by Wendker et al. (1991) in
their survey of
continuum emission from the Cygnus X region. Those observations,
with an angular resolution of 3.5
5.2
at 408 MHz,
established that the source is an extended object, about 5
to half power, with a non-thermal spectrum (measured between 408
and 4800 MHz). The structure of the object was revealed in
observations of higher angular resolution made by Landecker
et al. (1993). These observations showed that G76.9+1.0 is
morphologically similar to the sub-class of supernova remnants
(SNRs) which resemble the Crab Nebula, the filled-centre
remnants.
The emission from G76.9+1.0 has a spectral index
(where
) between 408 and 2700 MHz
(Landecker et al. 1993). However, there is some evidence that
the spectral index is lower at lower frequencies: Taylor et al.
(1992) measured a flux density at 327 MHz which is
approximately the same as the 408-MHz value, and is
significantly less than the flux density predicted by
extrapolating the high-frequency spectrum. In fact, a recent recalibration
of the 327-MHz observations (Taylor et al. 1996) indicates that the
value reported by Taylor et al. (1992) should be revised downward. To
investigate the spectrum of the source further, we sought to
make a flux-density measurement at a lower frequency, and in
this paper we report a flux density obtained at 232 MHz. To
give confidence in our spectrum for G76.9+1.0 we have also
obtained flux densities for a number of other
sources in the vicinity over as wide a frequency range as
possible.