The High Energy Astronomy Research Team (HEART)

The High Energy Astronomy Research Team (HEART) at Budapest does research on topics related to gamma-ray bursts, high energy astrophysics and cosmology.
   

Our studies address the internal properties of the GRBs from the central engine to the optical transients. We are dealing with studying the statistical properties of all types of the GRBs and try to find observable differences. According to the most widely accepted view there are two basic types but we found strong evidences for an intermediate one.
   

We identified complex structures on very large scales of the observable Universe by studying statistical properties of the spatial point process displayed by GRBs of known redshift.There's a large clustering of GRBs in the redshift range 1.6 < z < 2.1, with an estimated size of about 2-3 Gpc, centered at the general direction of the constellations of Hercules and Corona Borealis. We also discovered a ring with a diameter of 1.7 Gpc, displayed by 9 GRBs.   *  Its size exceeds the transition scale to the homogeneous and isotropic distribution by a factor of five.  *
   

We developed a method for the Fermi satellite called the Direction Dependent Background Fitting,   *  which characterizes and filters the background noise in an effective and physically realistic way.   We also developed the Automatized Detector Weight Optimization (ADWO) method, which identifies weak, short-duration electromagnetic transients in continuous  (e.g. Fermi GBM) data.  *
   

The GRB observed by Fermi GBM in possible coincidence with GW150914 offers new ways to test GRB prompt emission models. We modeled the gamma-ray emission with the currently favored GRB models  *  (internal shocks, dissipative photosphere and external shocks) and constrained their physical parameters (e.g. Lorentz factor).
     

Concerning the prompt and afterglow emission theory, we developed a method that can be used to establish if the energy in the jets is carried by baryons or by the magnetic field.   *  *  We also contributed to the design of the scientific program of future Cherenkov telescopes, calculating the detection prospects of GRBs.  *  *
     

Using the Fermi catalog data, we found highly significant physical differences among the peak flux and the other fluence spectral type.  *  Our results also show that the synchrotron mechanism is dominant in the GRB spectra, because the mean low-energy photon index is close to the canonical -2/3 value of during the peak flux.
   

We corrected the intrinsic ISM parameters of GRBs based on multi-wavelength measurements (Effelsberg-100m; Parkes-64m; ATCA; AKARI; Planck) of the galactic foreground.   *  *
   

We worked on the analysis and interpretation of the newly discovered magnetar giant flare detected for the first time from an extra-galactic source.   *  This involved identifying the shortest timescales (~0.08 msec) from a cosmic source and the first conclusive proof of relativistic outflow in a giant flare.
   

Our team effectively involved several young researchers in the group's scientific work, marked by 4 PhD and over a dozen MSc theses recently.