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Probable Optical Counterpart of IGR J00234+6141

ATel #709; J. P. Halpern (Columbia. U.), N. Mirabal (U. Michigan)
on 25 Jan 2006; 03:15 UT
Credential Certification: Jules Halpern (jules@astro.columbia.edu)

Subjects: Optical, X-ray, Cataclysmic Variable

We report a probable identification of the weak hard X-ray source IGR J00234+6141 (den Hartog et al., ATel #394) with a star that has an optical spectrum of a cataclysmic variable. den Hartog et al. noted the presence of a ROSAT All-Sky Survey source 1RXS J002258.3+614111 located 3.15' from the INTEGRAL position and marginally consistent with it, given the estimated 3' error radius (90% confidence) of the latter. On two observing runs using the the MDM 2.4m telescope, we obtained low-resolution spectra of 14 bright stars within 3' of the INTEGRAL position, and another 10 stars within 1' of the ROSAT position. Only one of these stars shows emission lines. The discovery spectrum was obtained on 2006 January 24 UT. It shows four emission lines of the Balmer series, the strongest being H-alpha with E.W.=3.7 nm. He I 5876, He I 6678, and He I 7065 are also present. There is also a He II 4686 line of E.W. approximately 2/3 that of H-beta. These properties are typical of X-ray emitting cataclysmic variables. The magnitudes of the star in the USNO-B1.0 and 2MASS catalogs are B=18.01, R=16.34, I=15.63, J=15.12, H=15.05, K=14.77. Its location at R.A. = 00h 22m 57.63s, Decl. = +61o 41' 07.8" (J2000), only 6" from the ROSAT position, makes it a secure counterpart of the ROSAT source. The absence of any additional optical candidate among the examined stars closer to the INTEGRAL position argues that the INTEGRAL source is identical to the ROSAT source, although it doesn't prove it .

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