Gamma ray observations of black hole candidates nova Ophiuchus 1993 and nova Velorum 1993.

摘要

Results of spectral analysis and time series analysis of the transient source x-ray nova Velorum 1993 (GRS 1009-45) and x-ray nova Ophicuhus 1993 (GRS 1716-249) are presented. These data were accumulated using the OSSE (Oriented Scintillation Spectrometer Experiment) low-energy gamma ray telescope on the Compton Gamma Ray Observatory.; Spectral observations of the two x-ray novae showed the presence of gamma ray emission to greater than 100 keV, which is thought to be a signature of a binary system with an accreting black hole. Observations of GRS 1009-45 shows that it was in a gamma-ray soft state during the one-day OSSE observation, which occurred during the exponential decay phase of the outburst. The spectrum of GRS 2716-249 acquired during the plateau stage of outburst indicated a hard state, while spectra acquired during the sawtooth outbursts suggest that a hard to soft transition occurs as the decay progresses. The 40-200 keV pre-outburst luminosity of GRS 1716-249 is shown to be two orders of magnitude less than that estimated during the plateau-stage observation.; The only significant power density spectrum was that acquired for GRS 1716-249 during the plateau stage of outburst. It is consistent with the sum of two QPO peaks at 0.128 and 0.32 Hz and a red noise ({dollar}nusp{lcub}-1{rcub}{dollar}) component. This power spectrum is consistent with other black hole candidate power spectra for which the source is in the low state. Power spectra for GRS 1009-45 and GRS 1716-249 during the peak of a sawtooth outburst are also presented. They are consistent with band-limited white noise. Corresponding autocorrelations are shown for all observations.