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IGRJ12580+0134, a flaring Seyfert 2 galaxy

ATel #3108; R. Walter, P. Bordas, E. Bozzo (ISDC, Geneva), V. Beckmann, S. De Jong (APC Paris), F. Panessa (IASF, Roma)
on 14 Jan 2011; 17:27 UT
Credential Certification: Roland Walter (Roland.Walter@unige.ch)

Subjects: X-ray, AGN

IGRJ12580+0134 was discovered by INTEGRAL during the observations of the 3C 273 field performed from 2011 January 2 to 11. The source was detected by IBIS/ISGRI (effective exposure time of 400 ks) at a significance level of 9.7 sigma (20-40 keV). The corresponding flux is 3.3+/-0.4 mCrab. IGRJ12580+0134 was also detected by JEMX in the soft energy band (3-10 keV), and the corresponding flux was 3.6+/-1.0 mCrab (effective exposure time 13 ks). The best determined position was found at: RA=194.5212 DEC=1.5738 (+/-2.3 arcmin, J2000), thus suggesting an association with the Seyfert 2 galaxy NGC 4845, which is not known as an X-ray source.

IGRJ12580+0134 was not detected during the observations of the same field performed previously from 2010 December 30 to 2011 January 2 nor from deep INTEGRAL observations of the field performed in the previous years and providing an upper limit of 0.3 mCrab in the 20-40 keV energy band. The source brightened by a factor >10, an unusual factor for a Seyfert 2. The ISGRI spectrum is very steep with a photon index of ~3.

A Swift XRT TOO observation performed on January 13 confirmed the association with the central regions of NGC 4845 with RA=194.5048 DEC=1.5753 (+/-3.6 arcsec, J2000). The Swift XRT spectrum can be modeled with an absorbed (NH ~ 8E22 cm-2) powerlaw (gamma ~ 3.3+/-0.3).

A radio observation would be useful to check the possible occurrence of a flare in NGC 4845.