ROSAT observations of the SIGMA source GRS 1227 + 025 near 3C 273

BeppoSAX observations of 3C 273

Long - Term Variability of the Hard X - ray Source GRS 1758 – 258 : GRANAT / SIGMA Observations

The results of GRANAT/SIGMA hard X-ray observations of GRS 1758–258 in 1990–1998 are presented. The source lies at ∼ 5 from the Galactic Center and was within the SIGMA field of view during the GRANAT surveys of this region. The total exposure time of the Galactic Center was 11×10 s. The regular SIGMA observations revealed strong variability of the source: the 40–150 keV flux varied at least by...

Time Variable Faraday Rotation Measures of 3c 273 & 3c 279

Multifrequency polarimetry with the VLBA confirms the previously reported timevarying Faraday rotation measure (RM) in the quasar 3C 279. Variability in the RM and electric vector position angle (EVPA) of the jet component (C4) is seen making it an unreliable absolute EVPA calibrator. 3C 273 is also shown to vary its RM structure on 1.5 year time-scales. Variation in the RM properties of quasar...

ROSAT observation of GRS 1739 – 278

We have observed GRS 1739–278 with the ROSAT HRI on March 31, 1996. The improved X-ray position proves the identification with an earlier discovered variable radio source. We derive an extinction of A V = 14 ± 2 from the dust scattering halo, which implies a distance of d ≈ 6–8.5 kpc. Thus, GRS 1739–278 radiates at least near the Eddington limit for a 1 M ⊙ compact object. The existence of the ...

ar X iv : a st ro - p h / 04 02 13 3 v 1 5 F eb 2 00 4 EXITE 2 Observation of the SIGMA Source GRS 1227 + 025

We report the EXITE2 hard X-ray imaging of the sky around 3C273. A 2h observation on May 8, 1997, shows a ∼260 mCrab source detected at ∼4σ in each of two bands (50-70 and 70-93 keV) and located ∼30' from 3C273 and consistent in position with the SIGMA source GRS1227+025. The EXITE2 spectrum is consistent with a power law with photon index 3 and large low energy absorption, as indicated by the ...