Optical spectroscopic followup of soft X-ray sources within the error boxes of two INTEGRAL objects

ATel #1540; P. Parisi, N. Masetti, R. Landi, L. Bassani (INAF/IASF, Bologna), A. J. Bird (Univ. Southampton), A. Bazzano (INAF/IASF, Rome), L. Morelli (Univ. Padua), G. Galaz and D. Minniti (PUC, Santiago)
on 20 May 2008; 15:02 UT
Credential Certification: Nicola Masetti (masetti@iasfbo.inaf.it)

Tweet

Following the detection of soft X-ray emission with Swift/XRT (Landi et al., ATel #1538) in the error boxes of the unidentified INTEGRAL sources IGR J09253+6929 and IGR J11098-6457 (Bird et al. 2007, ApJS, 170, 175), we performed optical spectroscopy on objects detected on the DSS-II-Red archive images (http://archive.eso.org/dss/dss) at the XRT positions within the 90% confidence level uncertainty circles of these two INTEGRAL sources.

The following results are obtained (coordinates refer to epoch J2000):

IGR J09253+6929: using the BFOSC instrument of the 1.5m 'Cassini' telescope of the Astronomical Observatory of Bologna in Loiano (Italy) plus Grism 4 on 2008 March 29, we acquired spectra of USNO-A2.0 optical source U1575_02974888 (RA = 09 25 47.58, Dec = +69 27 53.1) for a total exposure time of 3600 s.
Broad redshifted Halpha and Hbeta emissions, as well as narrow redshifted [OIII] emission lines, are detected. Using the observed wavelengths of the narrow lines we determine a redshift z = 0.039 for this object.
As this optical source is positionally associated with the only soft X-ray object inside the INTEGRAL error circle of IGR J09253+6929 (see Landi et al., ATel #1538), we firmly classify this hard X-ray source as a Seyfert 1 AGN.

IGR J11098-6457: optical spectra of USNO-A2.0 source U0225_10613596 (RA = 11 09 47.77, Dec = -64 52 45.4), associated with the XRT source within the INTEGRAL error circle of this hard X-ray object (as reported in Landi et al., ATel #1538), were obtained on 2008 March 3 with the R-C spectrograph of the CTIO 1.5m telescope in Cerro Tololo (Chile) plus Grating #13, for a total exposure time of 2400 s.
The object shows a continuum typical of an M-type giant, with superimposed Halpha and Hbeta lines in emission and at redshift zero.
While we are not claiming here that this is the lower-energy counterpart of IGR J11098-6457 (because of the presence of a further, harder and brighter XRT object 30 arcsec outside the INTEGRAL error circle of this source; see Landi et al., ATel #1538), we nevertheless suggest that U0225_10613596 is a Galactic symbiotic star.

We thank S. Galleti and A. De Blasi for Service Mode observations made in Loiano, and J. Velasquez for night assistance at CTIO.