Astrophys. Space Sci. Trans., 7, 65-68, 2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
09 Feb 2011
Gamma ray sources observation with the ARGO-YBJ detector
S. Vernetto on behalf of the ARGO-YBJ collaboration
IFSI-INAF Corso Fiume 4, 10133 Torino, Italy

Abstract. In this paper we report on the observations of TeV gamma ray sources performed by the air shower detector ARGO-YBJ. The objects studied in this work are the blazar Markarian 421 and the extended galactic source MGROJ1908+06, monitored during ~2 years of operation.

Mrk421 has been detected by ARGO-YBJ with a statistical significance of ~11 standard deviations. The observed TeV emission was highly variable, showing large enhancements of the flux during active periods. The study of the spectral behaviour during flares revealed a positive correlation of the hardness with the flux, as already reported in the past by the Whipple telescope, suggesting that this is a long term property of the source.

ARGO-YBJ observed a strong correlation between TeV gamma rays and the X-ray flux measured by RXTM/ASM and SWIFT/BAT during the whole period, with a time lag compatible with zero, supporting the one-zone SSC model to describe the emission mechanism.

MGROJ1908+06 has been detected by ARGO-YBJ with ~5 standard deviation of significance. From our data the source appears extended and the measured extension is
σext = 0.48°  +0.26
, in agreement with a previous HESS observation. The average flux is in marginal agreement with that reported by MILAGRO, but significantly higher than that obtained by HESS, suggesting a possible flux variability.

Citation: S. Vernetto on behalf of the ARGO-YBJ collaboration: Gamma ray sources observation with the ARGO-YBJ detector, Astrophys. Space Sci. Trans., 7, 65-68, doi:10.5194/astra-7-65-2011, 2011.
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