The RXTE/ASM reveals rebrightening of GROJ1655-40
ATel #445; Smith, D. A. (U. of Michigan)
on 28 Mar 2005; 18:04 UT
Credential Certification: Donald A. Smith (dasmith@space.mit.edu)
Subjects: Optical, X-ray, Binary, Black Hole, Transient
The RXTE/ASM reveals rebrightening of GROJ1655-40.
The 1-day averaged x-ray intensity of GRO J1655-40 has been declining since its
maximum of 1.70±0.02 Crab (2-12 keV) on 2005 Mar 19 (UT), reaching a
minimum of 940±10 mCrab on Mar 26. On Mar 27, the average intensity was
960±10 mCrab. The average of the five 90-s observations taken on Mar 28
(at this writing) yield an average of 1.06±0.03 Crab, indicating that
the source is rebrightening or possibly undergoing short-term flaring.
The ASM hardness ratios for today are consistent with no change in color compared
to the last two days.
The southern half of the ROTSE-III world-wide telescope system
has been monitoring GROJ1655-40 since 2005 Mar 8.6. The features of the
optical light curve do not match the features of the ASM X-ray light curve.
The optical intensity peaks around Mar
23.657 at 14.10±0.05 magnitudes (ROTSE-III magnitudes are unfiltered,
calibrated to the USNO A2.0 R-band catalog.). The source then fell by 0.6 mags
over 1.1 days, before beginning to rise again. Our last measurement at Mar
28.095 yields an intensity of 14.14±0.05 mags. The source is clearly
behaving differently at different wavelengths, and observations over a wide
range of frequencies would be useful.
X-ray and optical light curves can be seen in this
PDF file.
Thanks to the RXTE/ASM teams at MIT and NASA/GSFC. Also thanks to
the members of the ROTSE collaboration at UNSW Sydney, Siding Spring
Observatory, MPI-Heidelberg, and the HESS team in Namibia.
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