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IAUC 8076: IGR J16320-4751; IGR J16318-4848

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                                                  Circular No. 8076
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
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IGR J16320-4751
     J. A. Tomsick and R. Lingenfelter, University of California at
San Diego; R. Walter, INTEGRAL Science Data Centre; J. Rodriguez
and A. Goldwurm, Commissariat a l'Energie Atomique (CEA), Saclay;
S. Corbel, Universite Paris 7 and CEA, Saclay; and P. Kaaret,
Harvard-Smithsonian Center for Astrophysics, report the detection
of a variable hard x-ray source, IGR J16320-4751, with the IBIS
instrument's ISGRI detector onboard the INTEGRAL satellite.  The
source was detected at R.A. = 16h32m.0, Decl. = -47o51' (equinox
2000.0; uncertainty 2') during an observation of 4U 1630-47 on Feb.
1.4 UT.  The 15-40-keV source flux varies from < 10 to 50 mCrab on
a time scale of 1000 s, and the source was detected above 60 keV.
The position is consistent with that of the source AX J1631.9-4752
(detected during ASCA observations in 1994 and 1997).  The ASCA/GIS
source count rate varies by a factor of 4 during the 14000-s 1997
observation, and Sugizaki et al. (2001, Ap.J. Suppl. 134, 77) fit
the GIS energy spectrum with an absorbed power law with a photon
index of 0.2 +/- 0.2 and a hydrogen column density of (9 +/- 1) x
10**22 cm**-2, finding a mean 0.7-10-keV flux near 5 x 10**-11 erg
cm**-2 s**-1.  The hard power-law index may suggest that the source
is a high-mass x-ray binary, indicating that it may be possible to
identify the source at other wavelengths.


IGR J16318-4848
     L. Foschini, Istituto di Astrofisica Spaziale e Fisica Cosmica,
Consiglio Nazionale delle Ricerche, Bologna; J. Rodriguez, Service
d'Astrophysique, CEA, Saclay; and R. Walter, INTEGRAL Science Data
Centre, Geneva, report on the Digitized Sky Survey (DSS) II, 2MASS,
and Midcourse Space Experiment (MSX) archival data analyses of the
field of IGR J16318-4848 (IAUC 8063).  A clear source is detected
in the 2MASS All-Sky Quicklook image archive in the three bands J,
H, and K, at R.A. = 16h31m48s.3, Decl. = -48o49'01" (equinox 2000.0;
nominal uncertainty about 0".2) -- consistent with ASCA (IAUC 8070)
and XMM positions (IAUC 8072).  Very rough magnitude estimates (1-
mag uncertainties):  J = 10, H = 9, K = 9.  A counterpart is also
clearly detected in the I band of the second DSS at position end
figures 48s.2, 49'00".  No counterpart is visible in the R band of
the second DSS, to R = 21.  A source is also visible in the MSX5C
catalogue at position end figures 48s.3, 48'57" (uncertainty 1".5),
consistent with that of 2MASS.  The flux density at 8 microns is
0.4557 Jy.  The above data confirm that the source is heavily
absorbed.

                      (C) Copyright 2003 CBAT
2003 February 19               (8076)            Daniel W. E. Green

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