OSSE Observations of the Temporal Behavior of GRO J0422+32
Abstract
The OSSE instrument on the Compton Gamma Ray Observatory observed the hard X-ray transient source GRO J0422+32 (N Per 92) between 11 August and 17 September 1992. High time resolution data were obtained over several energy bands in the 0.05--4.5 MeV range with timing resolutions of 8 ms and 125 mu s. Power spectra at energies below 175 keV show substantial low-frequency noise and clear evidence of quasi-periodic oscillations (QPOs) with characteristic frequencies near 0.04 Hz and 0.2 Hz. The lower frequency QPO shows considerable variability in intensity from day to day, while the higher frequency QPO is broad and asymmetric, with a high-frequency tail. Analysis to date shows no evidence of signficant QPO at higher frequencies or energies. We will present a summary of the energy-dependence and temporal evolution of the low-frequency spectral components. We performed Fourier transform searches for coherent ms pulsations at frequencies up to 4 kHz, including acceleration corrections for binary orbits >7 hours. No statistically significant pulsations were seen, with 95% confidence upper limits to the pulsed fraction near 100 keV of ~ 0.5% for no acceleration and ~ 2% including accelerations.
- Publication:
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American Astronomical Society Meeting Abstracts
- Pub Date:
- December 1992
- Bibcode:
- 1992AAS...181.8507G