Constraints on Lorentz Invariance Violation using integral/IBIS observations of GRB041219A

One of the experimental tests of Lorentz invariance violation is to measure the helicity dependence of the propagation velocity of photons originating in distant cosmological obejcts. Using a recent determination of the distance of the gamma-ray burst GRB 041219A, for which a high degree of polarization is observed in the prompt emission, we are able to improve by four orders of magnitude the existing constraint on Lorentz invariance violation, arising from the phenomenon of vacuum birefringence.

Figure 1

Evolution during the burst duration of the polarimetric angle shift measured between the [200–250 keV] and in the [250–325 keV] energy range. The mean value, $21°\pm 47°$, is consistent with zero.

Figure 2

Scatter angle distribution of GRB041219A in the 200–250 keV and in the 250–325 keV energy band during the P9 time interval (see text). These distributions give the source count rate by azimuthal angle of the Compton scattering, and are consistent with a highly polarized signal. The chance probability of a nonpolarized signal is reported in each panel. The polarization angles derived from these distributions are consistent within 68° (see text).

Figure 3

Contour plot of the composed error on polarization angle and polarization fraction for the two energy bands, during the P9 time interval. The X cross shows the best fit position for the first energy band. Contour levels are at the 67, 90, and 95% level (from white toward black fill). The $+$ cross and dotted, dashed, and dash-dotted lines show the best fit parameters obtained for the second energy band, consistent at 95% with the first energy band best fit.