Search Publications
Ephemeris, orbital decay, and masses of ten eclipsing high-mass X-ray binaries
Bonnet-Bidaud, J. M.; Lutovinov, A.; Bozzo, E. +3 more
We update the ephemeris of the eclipsing high-mass X-ray binary (HMXB) systems LMC X-4, Cen X-3, 4U 1700-377, 4U 1538-522, SMC X-1, IGR J18027-2016, Vela X-1,IGR J17252-3616, XTE J1855-026, and OAO 1657-415 with the help of more than ten years of monitoring these sources with the All Sky Monitor onboard RXTE and with the Integral Soft Gamma-Ray Im…
The spectral variability of the gamma-ray emission from Geminga and VELA and its implications.
Grenier, I. A.; Hermsen, W.; Henriksen, R. N.
The gamma-ray emissions from Geminga and from the Interpeak 1 component of the Vela pulsar were analyzed in order to compare their spectral properties between 50 MeV and 5 GeV and to study their variability between 1975 and 1982 using the COS-B data. The stability of both sources above about 200 and 300 MeV, respectively, retaining an E exp -2.0 +…
Precise measurement of the right ascension of the Geminga pulsar using COS-B data.
Li, T. P.; Cheng, L. X.; Ma, Y. Q. +2 more
We have obtained a more precise value of the right ascension and a new spin evolution law of the Geminga pulsar using COS-B data on the assumption 0r high stability of the absolute phase. The new value is a(1950)=6h30m59s .057, with error about 0.5 arcsec, compared with the 3.2 arcsecs from the Einstein HRI result.…
Search for short bursts of gamma-ray emission in spark chamber data: application to COS-B
Buccheri, R.; Maccarone, M. C.; Fry, W. F.
We describe an analysis method aimed to the detection of short (<1000 s) bursts in the emission of gamma-ray sources using spark chamber data. The method utilizes a maximum likelihood technique which looks for accumulations of photons, compatible with the point spread function of the experiment, within the whole observing time and the field-of-…
Leptonic origin of diffuse galactic high-energy gamma rays - Indications for a varying cosmic ray proton-to-electron ratio
Schlickeiser, R.; Pohl, M.
The flux of high-energy (more than 300 MeV) gamma rays - caused by nonthermal bremsstrahlung and inverse Compton scattering - and the synchrotron flux at 408 MHz are calculated with the same power-law spectrum of relativistic electrons. Both are compared with the values observed at higher latitudes in the anticenter direction by employing the COS-…
An upper limit on the high-energy gamma-ray emission of VELA X-1.
Kanbach, G.; Oegelman, H.; Mattox, J. R.
The possibility of high-energy gamma-ray emission from the X-ray binary Vela X-1 was investigated by analyzing the COS-B satellite observations, using the COS-B X-ray detector for a phase coherent analysis in the search of rotational periodicity. The rotational upper limit is compared to the X-ray, TeV, and PeV fluxes reported by Chodil et al. (19…
The radial distribution of galactic gamma rays. IV. The whole galaxy.
Strong, A. W.; Grenier, I. A.; Hermsen, W. +6 more
The correlation between diffuse galactic γ-rays and gas tracers is studied using the final COS-B database and H I and CO surveys covering the entire galactic plane. A good quantitative fit to the γ-rays is obtained, with a small gradient in the γ-ray emissivity per hydrogen atom. The average ratio of H2 column density to integrated CO t…
High energy gamma rays from the VELA pulsar : long-term variability and energy distribution.
Grenier, I. A.; Hermsen, W.; Clear, J.
New results on the temporal and spectral characteristics of the high energy (50 MeV to 5 GeV) gamma ray emission from the Vela pulsar are presented. A new sensitive analysis method using maximum likelihood techniques has been applied to the final COS-B dataset. The whole pulsed flux is found to exhibit long term variability. The energy spectrum of…
High-energy gamma rays as a probe of cosmic-ray spectral differences throughout the Galaxy. II - A comparison with radio synchrotron emission
Schlickeiser, R.; Bloemen, J. B. G. M.; Reich, W. +1 more
A spectral analysis of the galactic high-energy γ-ray emission (300 MeV-6 GeV) is presented using the observations obtained with the COS-B satellite. Large-scale spectral variations are found and compared with recent results from a study of the galatic radio-continuum emission at 408 and 1420 MHz. The combination of the radio and γ-ray findings es…
High resolution cluster method for topological studies of the light curves of gamma-ray pulsars.
Buccheri, R.; Sacco, B.; di Gesu, V. +1 more
The authors describe a non-parametric, binning-free, adaptive method for the detection and the analysis of structures in the light curves of gamma-ray pulsars, based on a clustering technique. They use computer simulated data and a sample of COS-B data relative to the Vela pulsar to show its behavior and robustness. As a main result they find that…