SPECTRUM AND MORPHOLOGY OF THE TWO BRIGHTEST MILAGRO SOURCES IN THE CYGNUS REGION: MGRO J2019+37 AND MGRO J2031+41

Journal Article · Tue Jul 10 00:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/753/2/159· OSTI ID:22039376

Abdo, A A; Abeysekara, U; Linnemann, J T ^[1]; Allen, B T ^[2]; Aune, T ^[3]; Berley, D; Goodman, J A ^[4]; Bonamente, E; Galbraith-Frew, J G; Huentemeyer, P H; Hui, C M ^[5]; Christopher, G E; Kolterman, B E; Mincer, A I ^[6]; DeYoung, T ^[7]; Dingus, B L; Hoffman, C M ^[8]; Ellsworth, R W ^[9]; Gonzalez, M M ^[10]; others, and

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1. Department of Physics and Astronomy, Michigan State University, 3245 BioMedical Physical Sciences Building, East Lansing, MI 48824 (United States)
2. Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States)
3. Santa Cruz Institute for Particle Physics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)
4. Department of Physics, University of Maryland, College Park, MD 20742 (United States)
5. Department of Physics, Michigan Technological University, Houghton, MI 49931 (United States)
6. Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States)
7. Department of Physics, Pennsylvania State University, University Park, PA 16802 (United States)
8. Group P-23, Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545 (United States)
9. Department of Physics and Astronomy, George Mason University, 4400 University Drive, Fairfax, VA 22030 (United States)
10. Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, 74D.F., Mexico 04510 (Mexico)

The Cygnus region is a very bright and complex portion of the TeV sky, host to unidentified sources and a diffuse excess with respect to conventional cosmic-ray propagation models. Two of the brightest TeV sources, MGRO J2019+37 and MGRO J2031+41, are analyzed using Milagro data with a new technique, and their emission is tested under two different spectral assumptions: a power law and a power law with an exponential cutoff. The new analysis technique is based on an energy estimator that uses the fraction of photomultiplier tubes in the observatory that detect the extensive air shower. The photon spectrum is measured in the range 1-100 TeV using the last three years of Milagro data (2005-2008), with the detector in its final configuration. An F-test indicates that MGRO J2019+37 is better fit by a power law with an exponential cutoff than by a simple power law. The best-fitting parameters for the power law with exponential cutoff model are a normalization at 10 TeV of 7{sup +5}{sub -2} Multiplication-Sign 10{sup -10} s{sup -1} m{sup -2} TeV{sup -1}, a spectral index of 2.0{sup +0.5}{sub -1.0}, and a cutoff energy of 29{sup +50}{sub -16} TeV. MGRO J2031+41 shows no evidence of a cutoff. The best-fitting parameters for a power law are a normalization of 2.1{sup +0.6}{sub -0.6} Multiplication-Sign 10{sup -10} s{sup -1} m{sup -2} TeV{sup -1} and a spectral index of 3.22{sup +0.23}{sub -0.18}. The overall flux is subject to a {approx}30% systematic uncertainty. The systematic uncertainty on the power-law indices is {approx}0.1. Both uncertainties have been verified with cosmic-ray data. A comparison with previous results from TeV J2032+4130, MGRO J2031+41, and MGRO J2019+37 is also presented.

• OSTI ID: 22039376
• Journal Information: Astrophysical Journal, Vol. 753, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACCELERATION
ASTROPHYSICS
COMPARATIVE EVALUATIONS
COSMIC PHOTONS
COSMIC RAY DETECTION
COSMIC RAY PROPAGATION
EMISSION SPECTRA
EXTENSIVE AIR SHOWERS
GAMMA RADIATION
INDEXES
MORPHOLOGY
PHOTOMULTIPLIERS
PULSARS
TEV RANGE