Additional material for ATel 1264:
INTEGRAL detection of two Seyfert 1 galaxies: ESO 140-43 and ESO 141-55

by V. Beckmann (APC), D. Petry (MPE), and G. Weidenspointner (MPE/MPI HLL)

Subjects: X-ray, Gamma Ray, Optical, AGN

A region centered roughly on RA 18:30 h, DEC -60 deg (constellation Pavo) was observed by INTEGRAL from 2007 Oct 29 to Nov 4 for about 378 ks. In this observation, proposed to observe extended galactic diffuse emission, we discovered in IBIS/ISGRI sky maps two new INTEGRAL hard X-ray (20-80 keV) sources:
1) A source with 14 sigma significance at position RA = 18 45 10, DEC = -62 21 21 (J2000.0; estimated uncertainty 2 arcmin), consistent with ESO 140-43, a Seyfert-1 galaxy at z=0.0141. A power-law fit resulted in a spectral index of Γ = 1.8 ± 0.3 and a flux of 1.7e-11 erg/cm**2/sec (20-40 keV) and 2.6e-11 erg/cm**2/sec (40-100 keV), respectively. The combined JEM-X and ISGRI data show an overall luminosity of L=3e43 erg/sec in the 5-100 keV energy band. INTEGRAL's optical monitor OMC gives a V-band magnitude of 13.4 mag.
2) Another source with 19 sigma at position RA = 19 21 19, DEC = -58 39 49 (J2000.0; estimated uncertainty 2 arcmin), consistent with ESO 141-55, a Seyfert-1 galaxy at z=0.0366. Here, a power-law spectral fit resulted in a photon index of Γ = 1.9 ± -0.4 and a flux of 1.9e-11 erg/cm**2/sec (20-40 keV) and 1.2e-11 erg/cm**2/sec (40-60 keV), respectively. The combined spectrum gives a luminosity of 2e44 erg/sec in the 5-60 keV band, and also this source has V=13.4 mag according to the OMC.

Both objects have not previously been detected above 20 keV. They were detected in soft X-rays by ROSAT (0.1-2.4 keV, Voges et al., 1999, A&A, 349, 389) and RXTE (3-20 keV, Revnivtsev et al., 2004, A&A, 418, 927). ESO 141-55 was also detected by ASCA (0.7-2 keV, Ueda et al., 2005, ApJS, 161, 185).

Results based on spectral modelling (fluxes in erg cm^-2 s^-1):

	ESO 140-43	ESO 141-55
Γ	1.7 ± 0.2	1.9 ± 0.4
fX(5-20 keV)	0.9·10-11	3.4·10-11
fX(20-40 keV)	1.7·10-11	1.9·10-11
fX(40-100 keV)	2.6·10-11	2.8·10-11*
LX(5-100 keV)	3·1043 erg s-1	2.5·1044 erg s-1 *
V	13.4 mag	13.4 mag

^* extrapolated

Find below images and spectra extracted from IBIS/ISGRI and JEM-X1.

Figure 1: INTEGRAL IBIS/ISGRI 20-40 keV significance map of the area (revolution 616). ESO 141-55 and ESO 140-43 are located in a rich extragalactic field.

Figure 2: INTEGRAL JEM-X1 6-10 keV significance map of the area (combined data revolution 616 and 617). The exposure times in JEM-X1 on the two newly detected Seyfert 1 are 79.9 ksec for ESO 141-55 and 27.7 ksec for ESO 140-43.

Figure 3: INTEGRAL spectrum of ESO 140-43 based on JEM-X1 and IBIS/ISGRI data. The over all luminosity is L_{3-100 keV} = 3.3 x 10⁴³ erg sec^-1.

Figure 4: INTEGRAL spectrum of ESO 141-55 based on JEM-X1 and IBIS/ISGRI data. The over all luminosity is L_{5-60 keV} = 2 x 10⁴⁴ erg sec^-1.

Last update: November 9, 2007

In case of questions and comments: contact me at the APC.