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

Jarred M. Roberts; Steven Boggs; Thomas Siegert; John A. Tomsick; Marco Ajello; Peter von Ballmoos; Jacqueline Beechert; Floriane Cangemi; Savitri Gallego; Pierre Jean; Chris Karwin; Carolyn Kierans; Hadar Lazar; Alex Lowell; Israel Martinez Castellanos; Sean Pike; Clio Sleator; Yong Sheng; Hiroki Yoneda; Andreas Zoglauer

doi:10.3847/1538-4357/ad968a

The Astrophysical Journal (Jan 2025)

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

Jarred M. Roberts,
Steven Boggs,
Thomas Siegert,
John A. Tomsick,
Marco Ajello,
Peter von Ballmoos,
Jacqueline Beechert,
Floriane Cangemi,
Savitri Gallego,
Pierre Jean,
Chris Karwin,
Carolyn Kierans,
Hadar Lazar,
Alex Lowell,
Israel Martinez Castellanos,
Sean Pike,
Clio Sleator,
Yong Sheng,
Hiroki Yoneda,
Andreas Zoglauer

Affiliations

Jarred M. Roberts: ORCiD; Dept. of Astronomy and Astrophysics, University of California, San Diego , 9500 Gilman Drive, La Jolla, CA 92093, USA
Steven Boggs: ORCiD; Dept. of Astronomy and Astrophysics, University of California, San Diego , 9500 Gilman Drive, La Jolla, CA 92093, USA
Thomas Siegert: ORCiD; Fakultät für Physik und Astronomie, Institut für Theoretische Physik und Astrophysik, Lehrstuhl für Astronomie, Julius-Maximilians-Universität Würzburg , Emil-Fischer-Straße 31, D-97074 Würzburg, Germany
John A. Tomsick: ORCiD; Space Sciences Laboratory, University of California, Berkeley , 7 Gauss Way, Berkeley, CA 94720, USA
Marco Ajello: ORCiD; Department of Physics and Astronomy, Clemson University , 118 Kinard Laboratory, Clemson, SC 29634, USA
Peter von Ballmoos: ORCiD; Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse , CNRS, CNES, Université Toulouse III Paul Sabatier, 9 avenue Colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
Jacqueline Beechert: ORCiD; Space Sciences Laboratory, University of California, Berkeley , 7 Gauss Way, Berkeley, CA 94720, USA
Floriane Cangemi: Université-Paris Cité , 45 Rue des Saints-Pères, 75006 Paris, France
Savitri Gallego: ORCiD; Institut für Physik & Exzellenzcluster PRISMA+, Johannes Gutenberg-Universität Mainz , 55099 Mainz, Germany
Pierre Jean: ORCiD; Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse , CNRS, CNES, Université Toulouse III Paul Sabatier, 9 avenue Colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
Chris Karwin: ORCiD; NASA Goddard Space Flight Center , 8800 Greenbelt Road, Greenbelt, MD 20771, USA
Carolyn Kierans: ORCiD; NASA Goddard Space Flight Center , 8800 Greenbelt Road, Greenbelt, MD 20771, USA
Hadar Lazar: ORCiD; Space Sciences Laboratory, University of California, Berkeley , 7 Gauss Way, Berkeley, CA 94720, USA
Alex Lowell: Space Sciences Laboratory, University of California, Berkeley , 7 Gauss Way, Berkeley, CA 94720, USA
Israel Martinez Castellanos: ORCiD; NASA Goddard Space Flight Center , 8800 Greenbelt Road, Greenbelt, MD 20771, USA; Center for Research and Exploration in Space Science and Technology , NASA/GSFC, Greenbelt, MD 20771, USA; Department of Astronomy, University of Maryland , College Park, MD 20742, USA
Sean Pike: ORCiD; Dept. of Astronomy and Astrophysics, University of California, San Diego , 9500 Gilman Drive, La Jolla, CA 92093, USA
Clio Sleator: ORCiD; Naval Research Laboratory , 4555 Overlook Avenue Southwest, Washington, DC 20375, USA
Yong Sheng: ORCiD; Department of Physics and Astronomy, Clemson University , 118 Kinard Laboratory, Clemson, SC 29634, USA
Hiroki Yoneda: ORCiD; Fakultät für Physik und Astronomie, Institut für Theoretische Physik und Astrophysik, Lehrstuhl für Astronomie, Julius-Maximilians-Universität Würzburg , Emil-Fischer-Straße 31, D-97074 Würzburg, Germany
Andreas Zoglauer: ORCiD; Space Sciences Laboratory, University of California, Berkeley , 7 Gauss Way, Berkeley, CA 94720, USA

DOI: https://doi.org/10.3847/1538-4357/ad968a
Journal volume & issue: Vol. 979, no. 2
p. 116

Abstract

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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 ± 1.6) × 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 Γ = 2.20 ± 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 ± 0.2) × 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 a cutoff power law with a high-energy cutoff energy of 138.3 ± 1.0 keV and a photon index of Γ = 1.358 ± 0.002. Finally, we present the measured spectrum of Centaurus A and our best model fit to a power law with a photon index of Γ = 1.73 ± 0.01.

Published in The Astrophysical Journal

ISSN: 1538-4357 (Online)
Publisher: IOP Publishing
Country of publisher: United Kingdom
LCC subjects: Science: Astronomy: Astrophysics
Website: https://iopscience.iop.org/journal/0004-637X

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