Probable new AGN identified in S-CUBE SMC survey
ATel #9414; M. J. Coe (Southampton), J. A. Kennea (PSU), P. A. Evans (Leicester), I. McHardy (Southampton) and A. Udalski (Warsaw)
on 26 Aug 2016; 10:33 UT
Credential Certification: Malcolm Coe (mjcoe@soton.ac.uk)
Subjects: Optical, X-ray, AGN
The S-CUBED observations of the SMC (Kennea et al ATel #9299) have detected a persistent X-ray source at
the edge of the SMC. The source has been detected 44 times over the period MJD 57547 - 57624 with an
average count rate of 0.035 cts/s, which corresponds to a flux of 8.7E-13 ergs/sq-cm/s in the 2-10 keV
range. The Swift XRT values are consistent with a steady flux (reduced chi-sq of 1.04 for 43 degrees of freedom).
NuSTAR observations on 17 July 2016 revealed a flux in the 0.5-10 keV range of 1E-11 ergs/sq-cm/s and the
spectrum is well-fit by a simple power law with a photon index of 1.77 +/- 0.12. No evidence for any
temporal variations, periodic or otherwise, were detected. We note that the absorption determined from
these observations is 2.3 +/- 0.7 E21 /sq-cm, somewhat higher than the standard SMC value of 6E20 /sq-cm.
This suggest a significant amount of local absorption.
Chandra observations on 11 August 2016 located the position of the source to be 00h 32m 34.72s -73d 06m
49.14s. This position is consistent with an OGLE III and IV source (smc130.5.5002 and smc713.22.1840
respectively) which shows a non-stellar PSF. The optical source exhibits significant long term fluctuations
on timescales of years, with a mean I band magnitude of 19.2, and variations of 0.3 magnitudes.
Using the I band flux as an indicator of general optical flux levels, combined with the NuSTAR X-ray
flux levels, gives an Lx/Lopt~50. Though this is at the high end of the AGN scale normally occupied
by BL Lac systems (Maccacaro et al 1988 ApJ 680, 690), we suggest that this system is a background AGN.
S-CUBED will continue to monitor this system and we welcome any interested collaborators to contact us.