IGR J16558-4150: a new hard X-ray transient detected by INTEGRAL
ATel #987; S. Soldi (ISDC, Switzerland), S. Shaw (Southampton, UK), J. Miller (Univ. of Michigan), E. Kuulkers (ESA/ESAC), M. D. Caballero-Garcia (LAEFF/INTA), M. Diaz Trigo (ESA/ESAC), on behalf of a larger collaboration
on 5 Feb 2007; 16:08 UT
Credential Certification: Erik Kuulkers (ekuulker@rssd.esa.int)
Subjects: X-ray, Transient
A new hard X-ray transient has been discovered by the imager IBIS/ISGRI on
board of INTEGRAL, during the public ToO observation of GX 339-4 conducted between 2007 Jan 30th 15:55 and 2007 Feb 1st 06:11 UTC (ATel #980, #986).
The new source, IGR J16558-4150, was detected at the position RA = 253.95 DEC = -41.83,
with 3 arcmin accuracy.
The source was clearly visible in the 127 ksec mosaic image of the
observation, with an average flux of about 8 mCrab and a detection
significance of 8.6 sigma, in the 20-40 keV band. In individual 2.6 ksec pointings, the source is not detected, indicating that 20-40 keV flux is not strongly variable. The source is not detected in the mosaic image at higher energies, with an
upper limit of 4 mCrab in the 40-80 keV band. IGR J16558-4150 is not
detected at lower energies by the JEM-X instrument, with an upper limit of ~15 mCrab in the 3-30 keV range.
Only the IR source IRAS 16520-4146 is reported in Simbad within the ISGRI
error circle, at 2.6 arcmin. The closest known X-ray source is XMMU
J165520.0-41485, at a distance of 5.3 arcmin from our above quoted position.
This region will be observed again by INTEGRAL in the coming weeks (schedule available here http://integral.esac.esa.int/isoc/html/schedules/AO4_Long_Term_Plan.html ).
Follow-up observations of this new transient are strongly encouraged at
all wavelengths.
