Cygnus X-3 Flaring Activity during 13 Years of Observation and New Galactic Binary 4U 2129+47XR

Abstract

The new galactic gamma-source neutron star 2129+47XR is detected at energy > 0.8 TeV with flux (0.19±0.9)×10−12 cm−2s−1 and indices of the integral spectra are kγ = −1.05±0.10, kON = −1.54± 0.10 and kOFF = −1.74± 0.10. Cygnus X-3 is an X-ray binary system located about 10 kpc from earth. However, the nature of Cygnus X-3 is still unresolved. Attempts of detection of TeV emission from Cygnus X-3 were first made in the mid of 1970s and continued through the mid 1980s. Two observations were particularly important: the Kiel results and contemporaneous observation at Haverah Park. These results indicated a very large UHE flux from Cygnus X-3. The 13 year’s observation results of point source Cygnus X-3 by SHALON mirror Cherenkov telescope are presented. The galactic source Cygnus X-3, known more than twenty years as a source with variable intensity 10−11 − 5× 10−12cm−2s−1, has been regularly observed since a 1995 with average gamma-quantum flux of F (EO > 0, 8TeV ) = (6.2± 0.5)× 10−13 cm−2s−1. The energy spectrum of Cygnus X-3 at 0.8 65 TeV F (> EO) ∼ Eγ , where kγ = −1.21 ± 0.05 is obtained for the first time with flux on the order the less than upper limits published before. The spectrum of events passing through distinguishing criteria with background with index of kON = −1.33 ± 0.05 and spectrum of background events observed simultaneously with source with index of kOFF = −1.74 ± 0.05 are shown in comparison. The flux in 2003 year is (1.79 ± 0.33) × 10−12 cm−2s−1. The indexes of integral spectra are kγ = −1.28 ± 0.06, kON = −1.65 ± 0.11, kOFF = −1.74 ± 0.11, respectively. Earlier, in 1997, the increase of flux was also observed (1.2±0.5)×10−12 cm−2s−1. Thus, among ten observable gamma-quantum objects, there is galactic source Cygnus X-3, with periodic change of intensity. The variability of radiation can give essential information on a source nature. The binary Cyg X-3 came to new period of flaring activity at radioand X-ray energies in 2006. In May and July 2006 the significant increase of Cyg X-3 flux have detected with SHALON at TeV energy. The gamma-ray flux detected by SHALON in 2006 was estimated as (1.47±0.24)×10−12 cm−2s−1.