IGR J17418-12122 - USNO 0778-0495204 is an AGN.

ATel #264; M. A.P. Torres (CfA), M. R. Garcia (CfA), J. E. McClintock (CfA), D. Steeghs (CfA), J. Miller (CfA), P. J. Callanan (University College, Cork), P. Zhao (CfA), P. Berlind (CfA)
on 4 Apr 2004; 09:21 UT
Credential Certification: Manuel Torres (mtorres@cfa.harvard.edu)

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The INTEGRAL/EINSTEIN/ROSAT/NVSS objects IGR J17418-12122, 2E 1739.1-1210, 1RXS J174155.3-121157 and NVSS J174155-121201 have recently been suggested to be the same and considered to be a microquasar candidate with likely counterparts at optical and IR wavelengths (Tsarevsky et al. 2004, ATEL #239; Bassani et al. 2004, ATEL #232). In order to establish the identity of these sources, a 10-min spectrum of the tentative optical counterpart USNO 0778-0495204 was acquired on March 26.5 2004 (UT) with the FAST spectrograph attached to the 1.5-m telescope at the F. L. Whipple Observatory. The resulting spectrum is dominated by strong redshifted and blended emission lines at Halpha and N[II] 6548,6583. Also evident are Hbeta, [OIII] 4959,5007, HeI 5876 and [S II] 6716,6731. The spectrum is highly reminiscent of a Seyfert 1 galaxy given the large broadening of the hydrogen lines compared to the forbidden lines and the likely presence of weak FeII emission bands. The Halpha + N[II] profile has a FWZI of 12000 km/s and presents a red asymmetry partially caused by the unresolved telluric oxygen B bands at ~6870-6920. Using the narrow emission lines only, the redshift is estimated to be z=0.0372 +/- 0.0001. If we assume that USNO 0778-0495204 is the optical counterpart to 1RXS J174155.3-121157 and 2E 1739.1-1210, the intrinsic X-ray luminosities for the ROSAT and EINSTEIN sources are ~4e43 erg/s (0.1-2.4 keV) and ~1e43 erg/s (0.5-4.5 keV) respectively and they are in the range of Seyfert 1 galaxies (Rush et al.,1996,ApJ,471,190; Kriss et al.,1980,ApJ,242,492). The luminosities were estimated making use of PIMMS to convert the ROSAT PSPC and EINSTEIN IPC count rates to unabsorbed fluxes applying an absorbed power-law model with photon index 2.3 and NH=2.2e21 cm-2. These results suggest that USNO 0778-0495204, the ROSAT, the EINSTEIN and the radio sources are very likely the same extragalactic object and not a microquasar.