Title: GRS1227+025: A Hidden AGN or Transient?
Proposal ID: 0120180
Subject category: Extragalactic Object
Principal investigator: Grindlay
Institute: Harvard College Observatory
Abstract
We propose to observe GRS1227+025, a serendipitous source discovered by SIGMA in the vicinity of 3C273, with
IBIS. We have confirmed the existence of this source with out balloon-borne hard X-ray imager EXITE2. The
source is highly variable, with the EXITE2 flux (1997) a factor of ~ 5 - 10 larger than he SIGMA flux
(1991), and the SIGMA detections themselves variable over a factor of 3. Both the SIGMA and EXITE2
observations show a relatively soft spectrum in the 40-100 keV band. There is no soft X-ray (ROSAT) source
within the combined SIGMA/ART-P spectrum. The variability suggests a non-thermal (or beamed) source,
implying this may be the first example of a "Type 2" BL Lac. Our proposed observation can test this, and
other equally intriguing possibilities (e.g., the source may be a highly absorbed magnetic CV), with
important implications for the origin of the hard X-ray background.