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IAUC 8096: IGR J16320-4751; C/2001 RX_14

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                                                  Circular No. 8096
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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IGR J16320-4751
     J. Rodriguez, Commissariat a l'Energie Atomique (CEA), Service
d'Astrophysique (SA), Saclay; J. A. Tomsick, University of
California, San Diego (UCSD); L. Foschini, Instituto di Astrofisica
Spaziale e Fisica Cosmica, Consiglio Nazionale delle Ricerche,
Bologna; R. Walter, Integral Science Data Center, Versoix; A.
Goldwurm, CEA/SA, report that an XMM-Newton target-of-opportunity
observation on Mar. 4.85 UT shows a bright source at R.A. =
16h32m01s.9, Decl. = -47o52'29" (equinox 2000.0; uncertainty about
4"), with both EPIC cameras (pn and MOS) during an effective
exposure of about 4500 s.  The source location is consistent with
that for IGR J16320-4752 and AX J1631.9-4752 reported from earlier
INTEGRAL, ASCA, and Beppo-SAX observations (IAUC 8076, 8077;
Sugizaki et al. 2001, Ap.J. Suppl. 134, 77).  A fit to an EPIC-pn
spectrum with an absorbed power law gives a photon index of 1.6
(+0.2, -0.1) and a hydrogen column density of 21.3 (+3.7, -1.4) x
10**22 cm**-2 (1-sigma uncertainties).  The EPIC-pn source count
rate varies between about 0.1 and 0.6 count/s during the
observation.  The difference in the power-law index, compared to
that obtained with ASCA and Beppo-SAX, may suggest that the source
undergoes spectral transitions similar to those of x-ray binaries.
Longer x-ray observations and multiwavelength follow-ups are
strongly encouraged.
     Tomsick, Rodriguez, Goldwurm, Walter, and Foschini, also write:
"Infrared images from the 2MASS database show that two sources are
present within the XMM-Newton error circle for IGR J16320-4751 = AX
J1631.9-4752 (IAUC 8076, 8077).  The position of the source (with
magnitudes K_s = 10.9 +/- 0.1, H = 12.9 +/- 0.2, J > 16) that is
closest to the center of the x-ray error circle is R.A. =
16h32m01s.75, Decl. = -47o52'28".9 (equinox 2000.0; uncertainty 1").
The second source (K_s = 10.8, H = 11.2, J = 12.1) is on the
southeast edge of the x-ray error circle at position end figures
02s.18, 32".1.  For the first source, the colors suggest a
relatively high level of extinction, which is compatible with the
high neutral hydrogen column density inferred from x-ray
observations of this source.  This, along with the better
positional agreement, makes the first source a more likely
candidate.  Infrared observations are encouraged to check the

     Visual m_1 estimates:  Feb. 23.90 UT, 10.3 (K. Hornoch,
Lelekovice, Czech Rep., 0.13-m reflector); Mar. 4.01, 11.0 (J.
Carvajal, Madrid, Spain, 0.21-m refl.); 13.17, 11.1 (A. Diepvens,
Balen, Belgium, 0.15-m refractor).

                      (C) Copyright 2003 CBAT
2003 March 20                  (8096)            Daniel W. E. Green

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