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Context. Two classes of gamma-ray bursts (GRBs), short and long, have been determined without any doubts, and are usually prescribed to different physical scenarios. A third class, intermediate in T90 durations has been reported in the datasets of BATSE, Swift, RHESSI, and possibly BeppoSAX. The latest release of >1500 GRBs observed by Fermi gives an opportunity to further investigate the duration distribution. Aims. The aim of this paper is to investigate whether a third class is present in the log T90 distribution, or whether it is described by a bimodal distribution. Methods. A standard χ² fitting of a mixture of Gaussians was applied to 25 histograms with different binnings. Results. Different binnings give various values of the fitting parameters, as well as the shape of the fitted curve. Among five statistically significant fits, none is trimodal. Conclusions. Locations of the Gaussian components are in agreement with previous works. However, a trimodal distribution, understood in the sense of having three distinct peaks, is not found for any binning. It is concluded that the duration distribution in the Fermi data is well described by a mixture of three log-normal distributions, but it is intrinsically bimodal, hence no third class is present in the T90 data of Fermi. It is suggested that the log-normal fit may not be an adequate model. [ABSTRACT FROM AUTHOR]

Aims. We describe a new algorithm for extracting photometric information from meteor images. Methods. The time history of a moving point source of variable brightness is explicitly deconvolved from the spatial distribution of the meteor signal on the image. The method can be applied to time-integrated meteor images if kinematic information is independently available or, alternatively, assumed. Formal uncertainty estimation and reporting is included. Results. We test the algorithm on synthetic meteor images and meteors recorded during a recent double-station meteor observing campaign in Greece. In the first case, we find that both the synthetic signal and the a priori time variation of the flux are faithfully reproduced. In the second, the fluxes obtained from the two stations agree to ~20%. [ABSTRACT FROM AUTHOR]

We present a photometric and spectroscopic study of the polar ring galaxy A0136-0801 in order to constrain its formation history. Near-infrared and optical imaging data are used to extract surface brightness and colour profiles of the host galaxy and the wide polar structure in A0136-0801. The host galaxy dominates the light emission in all bands; the polar structure is more luminous in the optical bands and is three times more extended than the main spheroid. The average stellar population in the spheroid is redder than in the polar structure and we use their (B - K) versus (J - K) colours to constraint the ages of these populations using stellar population synthesis models. The inferred ages are 3-5 Gyr for the spheroid and 1-3 Gyr for the polar structure. We then use long slit spectra along the major axis of the polar structure to derive the emission line ratios and constrain the oxygen abundance, metallicity and star formation rate in this component. We find 12 + log(O/H) = 8.33 ± 0.43 and Z ~ 0.32 Z⊙, using emission line ratios. These values are used, together with the ratio of the baryonic masses of the host galaxy and polar structure, to constrain the possible models for the formation scenario. We conclude that the tidal accretion of gas from a gas-rich donor or the disruption of a gas-rich satellite are formation mechanisms that may lead to systems with physical parameters in agreement with those measured for A0136-0801. [ABSTRACT FROM AUTHOR]