Search Publications
3C 273 revisited : confirmation by COS-B of high energy gamma-ray emission.
Caraveo, P. A.; Bignami, G. F.; Hermsen, W. +11 more
The results of a second observation in the Virgo region by the ESA COS-B satellite are presented. The presence of a high- energy (50-800 MeV) gamma-radiation source is confirmed, and its position is consistent with 3C273. The error box at the 90% confidence level containing the quasar is ∼2.5 square degrees, and the probability of a chance coincid…
Search for gamma-radiation from extragalactic objects using a likelihood method.
Bignami, G. F.; Hermsen, W.; Masnou, J. L. +5 more
A search through COS-B data for gamma-radiation from a number of extragalactic objects reveals no strong evidence for any positive identification except, as already reported, for the region around the quasar 3C273. Upper limits to the photon fluxes from active extragalactic objects are evaluated using a likelihood method. They reinforce the conclu…
A change in light curve asymmetry and the ephemeris of CYG X-3.
van der Klis, M.; Bonnet-Bidaud, J. M.
Cygnus X-3 was observed in the 2-12 keV range for 40 days in May-June 1980. The mean 4.8 h light curve was seen to change significantly in a way suggestive of the existence of an underlying binary with an eclipse duration of 40 percent of the period. The observed time of X-ray minimum was found to increase the level of confidence of a period deriv…
The X-ray modulation of CYG X-3.
van der Klis, M.; Bonnet-Bidaud, J. M.
Results of three 40d COS-B X-rays observations of Cyg X-3 are presented. The shape of the light curve, although variable from cycle to cycle, is generally very stable when averaged over many cycles. During one four-week period, however, a different mean light curve was observed. It is shown that the correlated behavior of amplitude, average level,…
Long term X-ray observations of SMC X-1 including a turn-on.
van der Klis, M.; Bonnet-Bidaud, J. M.
A 38 d COS-B observation of SMC X-1 in the 2-12 keV band is presented, the observation including a turn-on of this source. The data are analyzed within the framework of the stellar wind accretion model, both from the point of view of the expected accretion rate and of the absorption of X-rays in the wind. It is noted that neither the high state lu…