We present a re-discovery of G278.94+1.35a as possibly one of the largest known Galactic supernova remnants (SNRs) – that we name Diprotodon. While previously established as a Galactic SNR, Diprotodon is visible in our new Evolutionary Map of the Universe (EMU) and GaLactic and Extragalactic All-sky MWA (GLEAM) radio continuum images at an angular size of $3{{{{.\!^\circ}}}}33\times3{{{{.\!^\circ}}}}23$, much larger than previously measured. At the previously suggested distance of 2.7 kpc, this implies a diameter of 157$\times$152 pc. This size would qualify Diprotodon as the largest known SNR and pushes our estimates of SNR sizes to the upper limits. We investigate the environment in which the SNR is located and examine various scenarios that might explain such a large and relatively bright SNR appearance. We find that Diprotodon is most likely at a much closer distance of $\sim$1 kpc, implying its diameter is 58$\times$56 pc and it is in the radiative evolutionary phase. We also present a new Fermi-LAT data analysis that confirms the angular extent of the SNR in gamma rays. The origin of the high-energy emission remains somewhat puzzling, and the scenarios we explore reveal new puzzles, given this unexpected and unique observation of a seemingly evolved SNR having a hard GeV spectrum with no breaks. We explore both leptonic and hadronic scenarios, as well as the possibility that the high-energy emission arises from the leftover particle population of a historic pulsar wind nebula.

We briefly discuss the history of membership and the current position of Serbia inside the International Astronomical Union. We give an overview of astronomy education, research and public outreach in Serbia. Some statistics are presented concerning the number and gender of BSc, MSc and PhD students that graduated/obtained their degree in astronomy/astrophysics from the Department of Astronomy, Faculty of Mathematics, University of Belgrade. Due attention is paid to the most important scientific/educational institutions in Serbia in which the majority of astronomers are employed as well as various research topics investigated.

New photoelectric BV light curves of three close eclipsing binaries XY Leo, EE Cet and AQ Psc were observed and studied with the aim to derive the physical parameters of these systems. The following results were obtained: (a) the W-type contact binary system XY Leo is in a marginal overcontact configuration (fover ∼ 2.4%) with a relatively large temperature difference between the components (∼330K); (b) due to the proximity of the companion of EE Cet in the visual binary ADS 2163, the light curves of EE Cet were contaminated by the third light, having a relatively large impact on the system-parameter estimates, and the solutions made with the third light parameter, L3 ∼ 0.54, describe EE Cet as a high-overcontact (fover ∼ 33%) W-type system; (c) the A-type W UMa contact eclipsing binary AQ Psc is in an overcontact configuration (fover ∼ 20%). The relatively small temperature difference (∼150K) and large difference in component masses suggest a significant energy transfer through the connecting neck of the common envelope. The absolute system parameters are obtained by combining our photometric solution with the spectroscopic elements given by other authors.

Recently, the modified equipartition calculation for supernova remnants (SNRs) has been derived by Arbutina et al. (2012). Their formulae can be used for SNRs with the spectral indices between 0.5 < α < 1. Here, by using approximately the same analytical method, we derive the equipartition formulae useful for SNRs with spectral index α=0.5. These formulae represent next step upgrade of Arbutina et al. (2012) derivation, because among 30 Galactic SNRs with available observational parameters for the equipartition calculation, 16 have spectral index α = 0.5. For these 16 Galactic SNRs we calculated the magnetic field strengths which are approximately 40 per cent higher than those calculated by using Pacholczyk (1970) equipartition and similar to those calculated by using Beck & Krause (2005) calculation.