GCN Circular 17318

S. Campana (INAF-Osservatorio astronomico di Brera) reports

XMM-Newton observed GRB 150101B/Swift J123205.1-10560
(Cummings 2015, GCN 17267
Not found
 
 
) on Jan 07, 2015 10:13:31 UT
(5.79 d after the burst discovery). The last ~16 ks of the observation were
affected by a mildly-enhanced background and were filtered out.
The resulting EPIC/pn exposure times is 33.2 ks.

A source is well detected at a position consistent with the Swift's
(Cummings et al. 2015, GCN 17268
Not found
 
 
), Chandra's (Troja et al. 2015, GCN
17289
Not found
 
 
), and radio (Fong 2015, GCN 17288
Not found
 
 
) ones.
No X-ray source is detected at the position of a second radio source (Fong
2015), whereas the two closeby sources detected by Chandra are too close
to be separated by XMM-Newton.
The source is relatively bright with a pn count rate of (2.8+/-0.1)x10^{-1}
cts/s.
We extracted 8620 source photons from the pn and fitted the X-ray spectrum
with a power law model including a non-negligible absorption component
at the galaxy redshift (z=0.134, Levan et al 2015, GCN 17281
Not found
 
 
) in addition
to the Galactic one (3.5x10^{20} cm^{-2}).
The best fit power law (chi2=1.03 with 244 degrees of freedom) implies
a photon index of Gamma=2.29+/-0.06 (90% c.l. for one parameter of
interest) and an additional column density marginally not consistent
with zero NH_z=(1.3+/-0.9)x10^{20} cm^{-2} (90% c.l.).
Any unresolved iron emission line (6.4-6.9 keV interval) should have an
equivalent width <230 eV.
The 0.5-8 keV unabsorbed flux is (4.3+/-0.1)x10^{-13} erg/cm^2/s, fully
consistent with the with the Chandra observation (Troja et al 2015).

This testifies that we are observing emission from a low luminosity Active
Galactic Nucleus (2x10^{43} erg/s) and not from the GRB afterglow.