Imaging and Spectral Fitting of Bright Gamma-ray Sources with the COSI Balloon Payload

Abstract

The Compton Spectrometer and Imager balloon payload (COSI-Balloon) is a wide-field-of-view Compton $\gamma$-ray telescope that operates in the 0.2 - 5 MeV bandpass. COSI-Balloon had a successful 46-day flight in 2016 during which the instrument observed the Crab Nebula, Cygnus X-1, and Centaurus A. Using the data collected by the COSI-Balloon instrument during this flight, we present the source flux extraction of signals from the variable balloon background environment and produce images of these background-dominated sources by performing Richardson-Lucy deconvolutions. We also present the spectra measured by the COSI-Balloon instrument, compare and combine them with measurements from other instruments, and fit the data. The Crab Nebula was observed by COSI-Balloon and we obtain a measured flux in the energy band 325 - 480 keV of (4.5 $\pm$ 1.6) $\times$ 10${}^{-3}$ ph cm${}^{-2}$ s${}^{-1}$. The model that best fits the COSI-Balloon data combined with measurements from NuSTAR and Swift-BAT is a broken power law with a measured photon index $\Gamma$ = 2.20 $\pm$ 0.02 above the 43 keV break. Cygnus X-1 was also observed during this flight, and we obtain a measured flux of (1.4 $\pm$ 0.2) $\times$ 10${}^{-3}$ ph cm${}^{-2}$ s${}^{-1}$ in the same energy band and a best-fit result (including data from NuSTAR, Swift-BAT, and INTEGRAL/ IBIS) was to a cutoff power law with a high-energy cutoff energy of 138.3 $\pm$ 1.0 keV and a photon index of $\Gamma$ = 1.358 $\pm$ 0.002. Lastly, we present the measured spectrum of Centaurus A and our best model fit to a power law with a photon index of $\Gamma$ = 1.73 $\pm$ 0.01.

References in corpus (16)

• X-ray Properties of Black-Hole Binaries
• Bright AGN Source List from the First Three Months of the Fermi Large Area Telescope All-Sky Survey
• INTEGRAL observations of the cosmic X-ray background in the 5-100 keV range via occultation by the Earth
• Broadband X-ray Imaging and Spectroscopy of the Crab Nebula and Pulsar with NuSTAR
• Background for a gamma-ray satellite on a low-Earth orbit
• Calibrations of the Compton Spectrometer and Imager
• Detection of the 511 keV Galactic positron annihilation line with COSI
• Polarimetric Analysis of the Long Duration Gamma Ray Burst GRB 160530A With the Balloon Borne Compton Spectrometer and Imager
• Imaging the 511 keV positron annihilation sky with COSI
• Potential origin of the state-dependent high-energy tail in the black hole microquasar Cygnus X-1 as seen with INTEGRAL
• Analysis of extremely low signal-to-noise ratio data from INTEGRAL/PICsIT
• Benchmarking simulations of the Compton Spectrometer and Imager with calibrations
• The hard X-ray continuum of Cen A observed with INTEGRAL SPI
• Probing the Galactic Diffuse Continuum Emission with COSI
• 2003-2019 Monitoring of the Crab emission through INTEGRAL SPI, or vice versa
• Measurement of Galactic ${}^{26}$Al with the Compton Spectrometer and Imager

Cited by in corpus (1)

• Enhancing Compton telescope imaging with maximum a posteriori estimation: a modified Richardson-Lucy algorithm for the Compton Spectrometer and Imager