Fermi GBM detection of a rise in Hard X-rays from Cyg X-1
ATel #6119; C. A. Wilson-Hodge (NASA/MSFC), G. Case (LaSierra Univ.), M. Cherry (LSU), J. Rodi (LSU), P. Jenke (UAH), M. Finger (USRA)
on 5 May 2014; 16:24 UT
Credential Certification: Colleen A. Wilson (Colleen.Wilson@nasa.gov)
Subjects: X-ray, Gamma Ray, Black Hole
Fermi GBM data show an increase in hard X-rays consistent with the transition to the hard state reported by MAXI (ATel #6115). Recently, Fermi GBM observations using the Earth occultation technique show an increase in the hard X-ray flux, beginning about February 28 (MJD 56716). The fluxes in the 12-25, 25-50, 50-100, and 100--300 keV bands, averaged over 25 days from MJD 56686-56711, have increased from 353+/-11, 275+/-18, 228+/-27, and 73+/-52 mCrab, respectively, to a 5-day average (MJD 56776-56781) of 678+/-24, 783+/-37, 846+/-52, 646+/-94 mCrab, respectively. These fluxes indicate that Cyg X-1 is transitioning to the hard state. Observations at other wavelengths are encouraged to further verify that Cyg X-1 has returned to the hard state. The daily-updated Fermi GBM light curves for Cyg X-1 are available at the link below.
Daily Updated Fermi GBM Light Curves for Cyg X-1