Possible radio, IR and soft X-ray counterpart of IGR J18027-1455

ATel #246; J. A. Combi (IAR, Argentina), M. Ribo (CEA Saclay, France), I. F. Mirabel
on 6 Mar 2004; 15:19 UT
Credential Certification: Jorge Ariel Combi (pauletich@sinectis.com.ar)

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Within the 2 arcminute-radius position error circle of the recently discovered INTEGRAL source IGR J18027-1455 (ATEL #229), we have found two weak radio sources in the 1.4 GHz NVSS maps. The first one, NVSS J180239-145453, has an estimated J2000.0 ICRS position of RA=18h02m39.94s (+/-0.25s), DEC=-14d54'53.6" (+/-3.3") (1 sigma uncertainties), has a flux density of 6.9 mJy and has no IR counterpart in 2MASS (see Ks-band 2MASS plot, where position error ellipses represent 2 sigma uncertainties). The second one, NVSS J180247-145451, has an estimated J2000.0 ICRS position of RA=18h02m47.37s (+/-0.13s), DEC=-14d54'51.6" (+/-2.2"), has a flux density of 10.5 mJy, and lies inside the 2 sigma position error circle of the faint ROSAT X-ray source 1RXS J180245.5-145432, which is well within the IBIS/ISGRI error circle. Inside the 2 sigma position error ellipse of this radio source is located an extended IR source, 2MASXi J1802473-145454, with coordinates RA=18h02m47.3s, DEC=-14d54'55" and magnitudes J=13.18, H=12.02, Ks=10.94. The optical counterpart of this IR source has average magnitudes B=19.3, R=14.9 and I=13.8 in the USNO-B1.0 catalog. The photometry of the IR/optical counterpart is not compatible with a stellar spectrum.

We suggest that the sources NVSS J180247-145451, 2MASXi J1802473-145454 and 1RXS J180245.5-145432 are the possible counterparts of IGR J18027-1455. There is no catalogued EGRET source coincident with IGR J18027-1455. Multiwavelength observations are planned to unveil the nature of this high-energy source.