First Results from Fermi GBM Earth Occultation Monitoring: Observations of Soft Gamma-Ray Sources Above 100 keV

Abstract

The NaI and BGO detectors on the Gamma-ray Burst Monitor (GBM) on Fermi are now being used for long-term monitoring of the hard X-ray/low energy gamma-ray sky. Using the Earth occultation technique as demonstrated previously by the BATSE instrument on the Compton Gamma-Ray Observatory, GBM can be used to produce multiband light curves and spectra for known sources and transient outbursts in the 8 keV to 1 MeV energy range with its NaI detectors and up to 40 MeV with its BGO detectors. Over 85% of the sky is viewed every orbit, and the precession of the Fermi orbit allows the entire sky to be viewed every ~26 days with sensitivity exceeding that of BATSE at energies below ~25 keV and above ~1.5 MeV. We briefly describe the technique and present preliminary results using the NaI detectors after the first two years of observations at energies above 100 keV. Eight sources are detected with a significance greater than 7 sigma: the Crab, Cyg X-1, SWIFT J1753.5-0127, 1E 1740-29, Cen A, GRS 1915+105, and the transient sources XTE J1752-223 and GX 339-4. Two of the sources, the Crab and Cyg X-1, have also been detected above 300 keV.

13 pages, 9 figures, submitted to ApJ

References in corpus (8)

• The Fermi Gamma-Ray Burst Monitor
• The MAXI Mission on the ISS: Science and Instruments for Monitoring All Sky X-Ray Images
• When A Standard Candle Flickers
• A Prominent Accretion Disk in the Low-Hard State of the Black Hole Candidate SWIFT J1753.5-0127
• Ground-based calibration and characterization of the Fermi Gamma-Ray Burst Monitor Detectors
• The High Energy Emission of the Crab Nebula from 20 keV to 6 MeV with INTEGRAL
• The hard state of black hole candidates: XTE J1752-223
• INTEGRAL and XMM-Newton Spectroscopy of GX 339-4 During Hard/Soft Intermediate and High/Soft States in the 2007 Outburst

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• X-Ray and Optical Observations of A 0535+26
• Three years of Fermi GBM Earth Occultation Monitoring: Observations of Hard X-ray/Soft Gamma-Ray Sources
• Earth Occultation Imaging of the Low Energy Gamma-Ray Sky with GBM
• Lens Flare: Magnified X-Ray Binaries as Passive Beacons in SETI
• Observations of V0332+53 during the 2015 Outburst using Fermi/GBM, MAXI, Swift, and INTEGRAL