Extremely short and puzzling pulses of gamma rays are daily bombarding Earth. We’ve been aware of their existence for half a century and learned quite a lot about them too. Two classes of gamma-ray bursts exist. Long bursts are the last screams of dying massive stars, so bright that we can see them all across the Universe. They are not-so-distant cousins of more familiar supernovae. And then there’s the short class of bursts, produced in a violent merger of two neutron stars. Gamma-ray bursts teach us about the evolution of stars and about the evolution of the Universe.
My career has always been intimately linked with gamma-ray bursts. I have studied the emission mechanisms of gamma-ray burst afterglows; afterglow is a long-lived emission following the initial short bursts of gamma rays. As a member of international collaborations, I observed and studied the galaxies in which gamma-ray bursts explode. One of the main questions permeating my research was the nature of long burst progenitors, that is, stars that give rise to the bursts.
Large scale structure in the Universe
Space between galaxies is filled with gas. Actually, galaxies and galaxy clusters, and all the gas between them, are a part of the large structure called the cosmic web. The web spreads throughout the Universe. We want to understand the properties of the structure: its dimension, how the galaxies are connected, how it changes as we travel back in time as the Universe was very young.
Almost all the gas in the web is composed of hydrogen. Today most of that hydrogen is ionized—it misses its electron. But it wasn’t always like that. Hydrogen in a very young Universe wasn’t ionized. What caused the ionization? The blame likely goes to galaxies that actively formed stars. Such galaxies give away a lot of light that can ionize hydrogen. We would like to know the properties of these galaxies in order to understand the process of ionization better. I used both galaxy observations and gamma-ray bursts (these beast are useful in so many ways!) to study such galaxies. See my blog post for more details.
New instruments often lay path to new discoveries. Extremely Large Telescope (ELT) will be the largest optical telescope on Earth (the diameter of its primary mirror will measure 38 meters, almost four times the size of the largest optical telescope today). I studied how the MOSAIC instrument, a spectrograph that will operate on the ELT, will help in the studies of the large scale structure.
Electromagnetic counterparts of gravitational waves
There are systems in the Universe which radiate gravitational waves. For example, a system of black holes rotating around each other, or a system of neutron stars. The two members of the system slowly drift towards each other and eventually merge, radiating strong gravitational waves. In 2017, LIGO and Virgo gravitational wave detectors detected a merger of two binary neutron stars. Other observatories have detected electromagnetic counterparts following the merger: a short gamma-ray burst and a kilonova emission. It is difficult to overstate the importance of this object for astronomy.
I am a member of ENGRAVE collaboration, a big group of scientists using (mostly) the Very Large Telescope in Chile to search for electromagnetic counterparts to newly detected gravitational waves. In the past year, we were not lucky, but our efforts did return some interesting results.