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GBM observations of V404 Cyg outburst

ATel #8457; P. Jenke (UAH), C. A. WIlson-Hodge (NASA/MSFC), V. Connaughton (USRA)
on 23 Dec 2015; 20:01 UT
Credential Certification: Peter Jenke (peter.a.jenke@nasa.gov)

Subjects: X-ray, Binary, Black Hole, Transient

Referred to by ATel #: 8458, 8462, 8475, 8489, 8494, 8499, 8501, 8507, 8512, 8520, 8531

On 2015-Dec-21 at 17:30:50.36, the Fermi Gamma Ray Burst Monitor (GBM) triggered on a source consistent with V404 Cyg (trigger 151221730/472411854; P. Jenke 2015, GCN 18719). Subsequent ground localization along with the Dec. 23 Swift trigger (S. D. Barthelmy et al. 2015, GCN 18716) confirmed that the source was V404 Cyg.

The GBM light curve consists of multiple peaks (10-1000 keV) with a duration (T90) of about 135 seconds (50 - 300 keV). The time averaged spectrum from T0-14 s to t0+12 s is best fit by a power law function with an index = -1.83+/-0.05. The energy flux (10-1000 keV) measured during this period was (1.17 +/- 0.09)E-7 erg/cm^2/s.

This event reached 7% of its Eddington luminosity (10-1000 keV) which is 10 times fainter than at its peak on 2015-June-26, but similar to the initial triggers on 2015-June-15 (G. Younes 2015, GCN 17932).

GBM observes sources between 8 keV and 40 MeV, with a ~60% duty cycle. GBM triggers and their source classification can be seen at the Fermi Science Support http://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigtrig.html.