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IAUC 8056: XTE J1720-318; 2002ka; 2002jy

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IAUC number

                                                  Circular No. 8056
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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XTE J1720-318
     C. B. Markwardt, University of Maryland and Goddard Space
Flight Center (GSFC); and J. H. Swank, GSFC, write: "The best x-ray
position of the transient XTE J1720-318, derived from RXTE PCA
scans on Jan. 15.06 UT, is R.A. = 17h20m00s, Decl. = -31o44'.8
(equinox 2000.0).  The estimated systematic uncertainty is 0'.5,
consistent with the radio position (IAUC 8054).  The x-ray flux
declined 30 percent between Jan. 14 and 19, from a maximum of 1.0 x
10**-8 erg cm**-2 s**-1 (2-10 keV).  The soft spectrum and low
high-frequency variability are consistent with the high soft states
of black-hole candidates."
     D. Kato and T. Nagata, Nagoya University, on behalf of the
InfraRed Survey Facility (IRSF)/Simultaneous three-color InfraRed
Imager for Unbiased Survey (SIRIUS) team of Nagoya University and
the National Astronomical Observatory of Japan; T. Kato and M.
Uemura, Kyoto University; and H. Yamaoka, Kyushu University, report
on near-infrared (J, H, K_s) imaging of the field of the x-ray
transient XTE J1720-318 (IAUC 8050) with the IRSF (which consists
of the Nagoya-South African Astronomical Observatory 1.4-m
telescope + SIRIUS) at Sutherland on Jan. 18.1 and 19.1 UT.  A
likely infrared counterpart was detected at R.A. = 17h19m59s.00,
Decl. = -31o45'01".2 (equinox 2000.0; about 150 2MASS reference
stars; rms error 0".2), located within 1".7 of the proposed radio
counterpart (IAUC 8054).  The new object is invisible on public
2MASS images; any definite identification would require further
follow-up observations, since the brightness of the new object is
close to the limiting magnitudes of the 2MASS survey.  Magnitudes
for the likely infrared counterpart of XTE J1720-318 are:  Jan.
18.1, J = 16.73 +/- 0.02, H = 15.91 +/- 0.03, K_s = 15.31 +/- 0.03;
19.1, 16.68 +/- 0.02, 15.80 +/- 0.03, 15.27 +/- 0.05.

     W. M. Wood-Vasey, Lawrence Berkeley National Laboratory,
reports that prediscovery NEAT observations of SN 2002ka (cf. IAUC
8038), taken with the NEAT 1.2-m reflector at Haleakala, yield
unfiltered magnitudes of 15.7 on 2002 Dec. 13.7 UT and 15.8 on Dec.

     Unfiltered CCD magnitude estimates by T. Vanmunster, Landen,
Belgium:  2002 Dec. 26.817 UT, 15.9; 2003 Jan. 8.733, 16.6.

                      (C) Copyright 2003 CBAT
2003 January 24                (8056)            Daniel W. E. Green

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