The extended TeV gamma-ray source ARGO J2031+4157 (or MGRO J2031+41) is positionally consistent with the Cygnus Cocoon discovered by Fermi-LAT at GeV energies in the Cygnus superbubble. Reanalyzing the ARGO-YBJ data collected from 2007 November to 2013 January, the angular extension and energy spectrum of ARGO J2031+4157 are evaluated. After subtracting the contribution of the overlapping TeV sources, the ARGO-YBJ excess map is fitted with a two-dimensional Gaussian function in a square region of 10 deg × 10 deg, finding a source extension σ_ext= (1.8 ± 0.5) deg. The observed differential energy spectrum is dN/dE = (2.5 ± 0.4) × 10−11(E/1TeV)^(−2.6±0.3) photons cm^(−2) s^(−1) TeV^(−1), in the energy range 0.2–10 TeV. The angular extension is consistent with that of the Cygnus Cocoon as measured by Fermi-LAT and the spectrum also shows a good connection with the one measured in the 1–100 GeV energy range. These features suggest to identify ARGO J2031+4157 as the counterpart of the Cygnus Cocoon at TeV energies. The Cygnus Cocoon, located in the star-forming region of Cygnus X, is interpreted as a cocoon of freshly accelerated cosmic rays related to the Cygnus superbubble. The spectral similarity with supernova remnants (SNRs) indicates that the particle acceleration inside a superbubble is similar to that in an SNR. The spectral measurements from 1 GeV to 10 TeV allows for the first time to determine the possible spectrum slope of the underlying particle distribution. A hadronic model is adopted to explain the spectral energy distribution.
IDENTIFICATION OF THE TeV GAMMA-RAY SOURCE ARGO J2031+4157 WITH THE CYGNUS COCOON / B., B., P., B., X. J., B.i., P., B., A., B., P., C., Z., C., R., C., Catalanotti, S., S. Z., C., T. L., C., P., C., S. W., C., B. Z., D., A., D., Danzengluobu, ., I., D.M., B., D.P., DI GIROLAMO, T., G., D.S., et al.. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - 790:(2014), p. 152. [10.1088/0004-637X/790/2/152]
IDENTIFICATION OF THE TeV GAMMA-RAY SOURCE ARGO J2031+4157 WITH THE CYGNUS COCOON
CATALANOTTI, SERGIO;DI GIROLAMO, TRISTANO;IACOVACCI, MICHELE;
2014
Abstract
The extended TeV gamma-ray source ARGO J2031+4157 (or MGRO J2031+41) is positionally consistent with the Cygnus Cocoon discovered by Fermi-LAT at GeV energies in the Cygnus superbubble. Reanalyzing the ARGO-YBJ data collected from 2007 November to 2013 January, the angular extension and energy spectrum of ARGO J2031+4157 are evaluated. After subtracting the contribution of the overlapping TeV sources, the ARGO-YBJ excess map is fitted with a two-dimensional Gaussian function in a square region of 10 deg × 10 deg, finding a source extension σ_ext= (1.8 ± 0.5) deg. The observed differential energy spectrum is dN/dE = (2.5 ± 0.4) × 10−11(E/1TeV)^(−2.6±0.3) photons cm^(−2) s^(−1) TeV^(−1), in the energy range 0.2–10 TeV. The angular extension is consistent with that of the Cygnus Cocoon as measured by Fermi-LAT and the spectrum also shows a good connection with the one measured in the 1–100 GeV energy range. These features suggest to identify ARGO J2031+4157 as the counterpart of the Cygnus Cocoon at TeV energies. The Cygnus Cocoon, located in the star-forming region of Cygnus X, is interpreted as a cocoon of freshly accelerated cosmic rays related to the Cygnus superbubble. The spectral similarity with supernova remnants (SNRs) indicates that the particle acceleration inside a superbubble is similar to that in an SNR. The spectral measurements from 1 GeV to 10 TeV allows for the first time to determine the possible spectrum slope of the underlying particle distribution. A hadronic model is adopted to explain the spectral energy distribution.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
