2009 Fermi Symposium, Washington, D.C., Nov. 2-5 3
FIG. 3: Cen A light curve. Horizontal scale is in modiﬁed
Julian days.
to observe these breaks, GBM is able to see signiﬁcant
emission above 300 keV, consistent with the canonical
hard spectrum.
Cen A(Fig. 3) is a Sy 2 galaxy that is the brightest
AGN in hard x-rays/low energy gamma rays. It has
a hard spectrum (Γ = 1 .8) and has been observed at
energies > 1 MeV [9]. The GBM results are consis-
tent with this hard spectrum, though GBM does not
have the sensitivity to determine if the hard spectrum
continues beyond 300 keV or if the spectrum cuts oﬀ.
Cyg X-1 (Fig. 4) is a HMXB and one of the
ﬁrst systems determined to contain a black hole. It
has been observed to emit signiﬁcant emission above
100 keV including a power law tail extending out to
greater than 1 MeV [10, 11]. The GBM results show
signiﬁcant emission above 300 keV, consistent with
the power law tail observed when Cyg X-1 is in its
hard state.
GRS 1915+105(Fig. 5) is a LMXB with the com-
pact object being a massive black hole. Evidence for
emission above 100 keV has been seen previously [12]
with BATSE. The GBM light curve integrated over
490 days shows signiﬁcant emission above 100 keV.
1E 1740-29 (Fig. 6) is a LMXB very near the
Galactic Center. It is a microquasar, and spends most
of its time in the low/hard state. Integral observa-
tions indicate the presence of a power law tail above
200 keV [13]. The present GBM results are consis-
tent with this high energy emission. In the future, we
FIG. 4: Cyg X-1 light curve. Horizontal scale is in modi-
ﬁed Julian days.
FIG. 5: GRS 1915+105 light curve. Horizontal scale is in
modiﬁed Julian days.
eConf C091122