Central Bureau for Astronomical Telegrams
IAUC 5593: GRO J0422+32
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Circular No. 5593
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM EASYLINK 62794505
MARSDEN@CFA or GREEN@CFA (.SPAN, .BITNET or .HARVARD.EDU)
GRO J0422+32
X. Han and R. M. Hjellming, National Radio Astronomy Observatory,
report: "A radio counterpart to GRO J0322+32 = GRS 0417+335
has been detected with the Very Large Array at the position R.A. =
4h21m42s.8, Decl. = +32 54'27" (equinox J2000.0; uncertainty about
5"). This is consistent with the IUE position on IAUC 5591.
Preliminary analysis indicates that the source was increasing in flux
from a level of 4 mJy at 4.9 GHz on Aug. 13 to about 8 mJy on Aug.
17 at 1.49 and 4.9 GHz. This is consistent with the early behavior
of the V404 Cyg radio source after the decay of its initial fast
radio transient."
R. Sunyaev, E. Churazov, M. Gilfanov, B. Novikov, A. Goldwurm,
J. Paul, P. Mandrou, and P. Techine, on behalf of the Granat team
(Space Research Institute, Moscow; Service d'Astrophysique du CEA,
Saclay; Centre d'Etude Spatiale des Rayonnements, Toulouse), report:
"GRO J0422+32 was observed by SIGMA/Granat on Aug. 15, 16, and 17.
The source flux in the energy range 40-150 keV, when averaged daily,
is remarkably stable: 2.91 +/- 0.01, 2.88 +/- 0.01, 2.82 +/- 0.01
Crab for Aug. 15, 16, and 17, respectively. The spectrum exhibits
clear steepening at energies above 150 keV. In terms of thermal
emission of optically thin plasma, the shape of the spectrum
corresponds to a temperature of about 120 keV. A single temperature
comptonization model requires T about 50 keV and a Thomson scattering
depth of 2.5 (for a sphere; 0.9 for disk geometry). The 400-
to 600-keV flux (detected at the 5.4-sigma level) of the spectrum
averaged over Aug. 15, 16, and 17 seems to be in excess (by 3.8-
sigma) of crude extrapolation of the lower-energy part of the
spectrum. This result could indicate the presence of a hot region in
the disk or high energy excess related to electron-positron
annihilation (similar to one reported previously by SIGMA/Granat for
the black hole candidate 1E 1740.7-2942). The power density spectra
of the 40- to 70-keV and 70- to 150-keV fluxes were obtained in
the range 0.00002-0.1 Hz. The squared fractional rms density (
averaged over Aug. 15, 16, and 17) in the range 0.001-0.04 Hz has a
level of 0.36 HzE-1 at 40-70 keV and resembles that of Cygnus X-1.
In the energy range 70-150 keV, the rms density level is significantly
lower (about 0.21 HzE-1). At frequencies lower than 1 mHz,
the rms density is much lower than that of Cygnus X-1 for both
energy bands. Although the global shape of the power spectrum is
flat between a few hundred microHz and 40 mHz, structures of broad
dips and humps are present."
1992 August 22 (5593) Daniel W. E. Green
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