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(1993 Jan. 11)
GRO J0422+32
Further analysis of photometry of GRO J0422+32 since Dec. 13 confirms
that the variability in Dec. and Jan. is excellently expressed by a single
period of P=0.21193 days. The folded light curve show rather sinusoidal
profile. Therefore the period change is real and the fact strongly favors
the origin of the prevously reported period other than orbital modulation.
The maxima is double-peaked, or more exactly expressed by dip-like structure
at phase 0.8 (phase 0 = main hump).
This folded light curve is removed from the original data, and further
power analysis can not yield any periodicity below P=1 day. Therefore there
is no sign of the double period at this time. However, nightly variation of
the mean magnitude very probably exists. Preliminary analysis gives a
possible period of P=9.65 days (other periods are also possible) with an
amplitude of 0.1 mag, but the run is not yet long enough compared to this
period and the fading trend may not be properly removed. If we take this
period and the beat period with the persent P becomes 0.21668 days, which
is close to the period previously reported.
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