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EXITE2 Observation of the SIGMA Source GRS 1227+025

J. E. Grindlay·P. F. Bloser·Y. Chou·T. Narita
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Abstract

We report the EXITE2 hard X-ray imaging of the sky around 3C273. A 2h observation on May 8, 1997, shows a $\sim$260 mCrab source detected at $\sim4σ$ in each of two bands (50-70 and 70-93 keV) and located $\sim$30' from 3C273 and consistent in position with the SIGMA source GRS1227+025. The EXITE2 spectrum is consistent with a power law with photon index 3 and large low energy absorption, as indicated by the GRANAT/SIGMA results. No source was detected in more sensitive followup EXITE2 observations in 2000 and 2001 with 3$σ$ upper limits of 190 and 65 mCrab, respectively. Comparison with the flux detected by SIGMA shows the source to be highly variable, suggesting it may be non-thermal and beamed and thus the first example of a ``type 2'' (absorbed) Blazar. Alternatively it might be (an unprecedented) very highly absorbed binary system undergoing accretion disk instability outbursts, possibly either a magnetic CV, or a black hole X-ray nova.

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J. E. Grindlay, P. F. Bloser, Y. Chou, T. Narita. 2004-02-05. EXITE2 Observation of the SIGMA Source GRS 1227+025. https://doi.org/10.1086/383457

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