The nature of gamma-ray bursts (GRBs) and their use as cosmological probes

Lead Research Organisation: University of Leicester
Department Name: Physics and Astronomy

Abstract

Gamma-ray bursts, usually known as GRBs, were originally discovered in the 1960s by orbiting military satellites, but only in 1997 was the distance to one first measured. To many astronomers' surprise it turned out to be about half way across the observable Universe, which meant that GRBs are by far the most luminous objects known to science. This breakthrough observation was made possible by the first detection of the faint remnant, a so-called afterglow, of the GRB in optical light. GRBs themselves are characterised by the intense bursts of high-energy gamma-rays they produce, which only last typically a few seconds or minutes. By contrast, the afterglows, fade away over a period of days and weeks. Optical detection turned out to be critical because it provided a very accurate position for the GRB, and ultimately a spectroscopic redshift, which astronomers can easily translate into a measurement of distance. Since 1997, further research has shown that GRBs are produced when certain rare kinds of star, much more massive than the Sun, collapse at the end of their lives to form black holes. In the process, by means we still do not understand, jets of material are ejected at velocities very close to the speed of light. These jets are the source of the flashes of gamma-rays we see, and when they crash into the tenuous gas surrounding the star, the afterglow light is produced. My research is aimed at better understanding these astonishing events, and using these ultimate cosmic light-houses to probe the distant regions of the Universe. The next few years promise to be a very exciting time in the GRB field thanks to the imminent launch of a new US/UK/Italian satellite called Swift. This satellite will detect more GRBs than previously, and rapidly transmit their positions to the ground. My own programs are largely concerned with following up these positions, to find and monitor afterglows, and to search for rare exciting types of GRBs. To do this I will use the UK's RoboNet network of three large robotic telescopes sited at various locations around the world. These are ideal for rapid, intensive follow-up of GRB afterglows. I will also make use of other facilities, such as the VLT and Gemini 8m telescopes, the Hubble Space Telescope and other observatories. A particularly exciting possibility is that with Swift we will discovery GRBs at distances greater than any previous galaxy or quasar has been found. Since when we look across the Universe we are looking backward in time, such a discovery would open a new window on the very earliest times, shortly after the Big Bang. At these distances galaxies and even quasars are expected to be rare and faint. GRBs by contrast should be bright enough to detect, and providing we can observe them quickly enough, should provide a great deal of information about the regions they occur in, and the state of matter in the Universe at that time. Another prime goal is to investigate the nature of so-called 'short duration' bursts. These events are very similar to the standard GRBs, but their gamma-ray flashes are briefer, often much less than a second. So far no afterglows have been found for short-duration bursts, so we do not even known how far away they are, let alone what causes them. A favourite idea is that they might be produced when two neutron-stars, extremely dense objects with masses similar to that of the Sun, but sizes only a few miles across, collide and merge with each other releasing enormous reservoirs of energy.

Publications

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Bersier D. (2006) Evidence for a supernova associated with the X-ray flash 020903 in ASTROPHYSICAL JOURNAL

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Chen H (2010) A MATURE DUSTY STAR-FORMING GALAXY HOSTING GRB 080607 AT z = 3.036 in The Astrophysical Journal

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D'Elia V (2010) VLT/X-shooter spectroscopy of the GRB 090926A afterglow in Astronomy & Astrophysics

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Levan A. J. (2006) The first Swift X-ray flash: The faint afterglow of XRF 050215B in ASTROPHYSICAL JOURNAL

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Levan A. J. (2006) The faint afterglow and host galaxy of the short-hard GRB 060121 in ASTROPHYSICAL JOURNAL

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Pandey S (2010) GRB 090902B: AFTERGLOW OBSERVATIONS AND IMPLICATIONS in The Astrophysical Journal

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Rol E (2007) The early- and late-time spectral and temporal evolution of GRB 050716 in Monthly Notices of the Royal Astronomical Society

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Starling R (2011) Discovery of the nearby long, soft GRB 100316D with an associated supernova Discovery of GRB 100316D in Monthly Notices of the Royal Astronomical Society

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Tanvir N. R. (2012) STAR FORMATION IN THE EARLY UNIVERSE: BEYOND THE TIP OF THE ICEBERG in ASTROPHYSICAL JOURNAL

 
Description This grant funded research into gamma-ray bursts (GRBs), which are the most luminous objects in the universe. Work done under this award consolidated the evidence that GRBs are extraordinarily violent explosions of massive stars when the reach the ends of their lives. One of the main achievements I made was the discovery of a gamma-ray burst (in April 2009) that still holds the record as the most distant object so far identified, at 13.1 billion light years. The importance of this is that it provides a new window into the formation of early stars and galaxies, in the first few hundred million years after the Big Bang.
Exploitation Route GRBs are continuing to shed new light on the early stages of structure formation in the universe.
Sectors Education

URL http://www.star.le.ac.uk/~nrt3/
 
Description My findings have been used to provide motivation for new observational programmes and satellite proposals. They have also been used to further our understanding of the universe.
First Year Of Impact 2010
Sector Education
Impact Types Cultural

 
Description PPARC/STFC Standard grant
Amount £261,714 (GBP)
Organisation Science and Technologies Facilities Council (STFC) 
Sector Public
Country United Kingdom
Start 04/2007 
End 03/2010
 
Description GRB follow-up collaborations 
Organisation Liverpool John Moores University
Department Astrophysics Research Institute
Country United Kingdom 
Sector Academic/University 
PI Contribution My team has played a leading role in the world-wide GRB follow-up activity, which has been greatly enhanced by collaboration with these many groups. The mutual benefits are access to facilities which one wouldn't otherwise have direct access to, sharing workload during time-critical follow-up periods, scientific cross-fertilisation of ideas.
Collaborator Contribution We have collaborated with the Bristol group on observations of very high redshift galaxies, as selected by GRBs.
Impact The outputs are largely the scientific papers already listed. In addition, a number of our results have generated media interest. We have supported (in the sense of helping organise, attending and speaking at etc.) meetings amongst the collaborators. These collaborations have also been vital to the work of PhD students at Leicester under my supervision.
 
Description GRB follow-up collaborations 
Organisation Reykjavík University
Department Department of Physics
Country Iceland 
Sector Academic/University 
PI Contribution My team has played a leading role in the world-wide GRB follow-up activity, which has been greatly enhanced by collaboration with these many groups. The mutual benefits are access to facilities which one wouldn't otherwise have direct access to, sharing workload during time-critical follow-up periods, scientific cross-fertilisation of ideas.
Collaborator Contribution We have collaborated with the Bristol group on observations of very high redshift galaxies, as selected by GRBs.
Impact The outputs are largely the scientific papers already listed. In addition, a number of our results have generated media interest. We have supported (in the sense of helping organise, attending and speaking at etc.) meetings amongst the collaborators. These collaborations have also been vital to the work of PhD students at Leicester under my supervision.
 
Description GRB follow-up collaborations 
Organisation Space Telescope Science Institute
Country United States 
Sector Academic/University 
PI Contribution My team has played a leading role in the world-wide GRB follow-up activity, which has been greatly enhanced by collaboration with these many groups. The mutual benefits are access to facilities which one wouldn't otherwise have direct access to, sharing workload during time-critical follow-up periods, scientific cross-fertilisation of ideas.
Collaborator Contribution We have collaborated with the Bristol group on observations of very high redshift galaxies, as selected by GRBs.
Impact The outputs are largely the scientific papers already listed. In addition, a number of our results have generated media interest. We have supported (in the sense of helping organise, attending and speaking at etc.) meetings amongst the collaborators. These collaborations have also been vital to the work of PhD students at Leicester under my supervision.
 
Description GRB follow-up collaborations 
Organisation University of Amsterdam
Department Department of Astrophysics
Country Netherlands 
Sector Academic/University 
PI Contribution My team has played a leading role in the world-wide GRB follow-up activity, which has been greatly enhanced by collaboration with these many groups. The mutual benefits are access to facilities which one wouldn't otherwise have direct access to, sharing workload during time-critical follow-up periods, scientific cross-fertilisation of ideas.
Collaborator Contribution We have collaborated with the Bristol group on observations of very high redshift galaxies, as selected by GRBs.
Impact The outputs are largely the scientific papers already listed. In addition, a number of our results have generated media interest. We have supported (in the sense of helping organise, attending and speaking at etc.) meetings amongst the collaborators. These collaborations have also been vital to the work of PhD students at Leicester under my supervision.
 
Description GRB follow-up collaborations 
Organisation University of Bristol
Department School of Physics
Country United Kingdom 
Sector Academic/University 
PI Contribution My team has played a leading role in the world-wide GRB follow-up activity, which has been greatly enhanced by collaboration with these many groups. The mutual benefits are access to facilities which one wouldn't otherwise have direct access to, sharing workload during time-critical follow-up periods, scientific cross-fertilisation of ideas.
Collaborator Contribution We have collaborated with the Bristol group on observations of very high redshift galaxies, as selected by GRBs.
Impact The outputs are largely the scientific papers already listed. In addition, a number of our results have generated media interest. We have supported (in the sense of helping organise, attending and speaking at etc.) meetings amongst the collaborators. These collaborations have also been vital to the work of PhD students at Leicester under my supervision.
 
Description GRB follow-up collaborations 
Organisation University of California, Berkeley
Department Department of Astronomy
Country United States 
Sector Academic/University 
PI Contribution My team has played a leading role in the world-wide GRB follow-up activity, which has been greatly enhanced by collaboration with these many groups. The mutual benefits are access to facilities which one wouldn't otherwise have direct access to, sharing workload during time-critical follow-up periods, scientific cross-fertilisation of ideas.
Collaborator Contribution We have collaborated with the Bristol group on observations of very high redshift galaxies, as selected by GRBs.
Impact The outputs are largely the scientific papers already listed. In addition, a number of our results have generated media interest. We have supported (in the sense of helping organise, attending and speaking at etc.) meetings amongst the collaborators. These collaborations have also been vital to the work of PhD students at Leicester under my supervision.
 
Description GRB follow-up collaborations 
Organisation University of Copenhagen
Department Dark Cosmology Centre
Country Denmark 
Sector Academic/University 
PI Contribution My team has played a leading role in the world-wide GRB follow-up activity, which has been greatly enhanced by collaboration with these many groups. The mutual benefits are access to facilities which one wouldn't otherwise have direct access to, sharing workload during time-critical follow-up periods, scientific cross-fertilisation of ideas.
Collaborator Contribution We have collaborated with the Bristol group on observations of very high redshift galaxies, as selected by GRBs.
Impact The outputs are largely the scientific papers already listed. In addition, a number of our results have generated media interest. We have supported (in the sense of helping organise, attending and speaking at etc.) meetings amongst the collaborators. These collaborations have also been vital to the work of PhD students at Leicester under my supervision.
 
Description GRB follow-up collaborations 
Organisation University of Hertfordshire
Department School of Physics and Astronomy
Country United Kingdom 
Sector Academic/University 
PI Contribution My team has played a leading role in the world-wide GRB follow-up activity, which has been greatly enhanced by collaboration with these many groups. The mutual benefits are access to facilities which one wouldn't otherwise have direct access to, sharing workload during time-critical follow-up periods, scientific cross-fertilisation of ideas.
Collaborator Contribution We have collaborated with the Bristol group on observations of very high redshift galaxies, as selected by GRBs.
Impact The outputs are largely the scientific papers already listed. In addition, a number of our results have generated media interest. We have supported (in the sense of helping organise, attending and speaking at etc.) meetings amongst the collaborators. These collaborations have also been vital to the work of PhD students at Leicester under my supervision.
 
Description GRB follow-up collaborations 
Organisation University of Warwick
Department Department of Physics
Country United Kingdom 
Sector Academic/University 
PI Contribution My team has played a leading role in the world-wide GRB follow-up activity, which has been greatly enhanced by collaboration with these many groups. The mutual benefits are access to facilities which one wouldn't otherwise have direct access to, sharing workload during time-critical follow-up periods, scientific cross-fertilisation of ideas.
Collaborator Contribution We have collaborated with the Bristol group on observations of very high redshift galaxies, as selected by GRBs.
Impact The outputs are largely the scientific papers already listed. In addition, a number of our results have generated media interest. We have supported (in the sense of helping organise, attending and speaking at etc.) meetings amongst the collaborators. These collaborations have also been vital to the work of PhD students at Leicester under my supervision.
 
Description Astronomical Society - Bradford 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Primary Audience Public/other audiences
Results and Impact Gave a talk on record-breaking GRB 090423. Much discussion.

Many questions during talk.
Year(s) Of Engagement Activity 2010
 
Description Astronomical Society - Clacton 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Primary Audience Public/other audiences
Results and Impact Talk on recent results from HST. Much discussion.

Lengthy Question and answer session at end.
Year(s) Of Engagement Activity 2006
 
Description Astronomical Society - Mexborough and Swinton 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Primary Audience Public/other audiences
Results and Impact Delivered talk to society on gamma-ray burst results. Generated much discussion.

Extensive Q&A
Year(s) Of Engagement Activity 2010
 
Description Astronomical Society - Stratford 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Primary Audience Public/other audiences
Results and Impact Talk on the early universe, provoking much discussion.

Many questions.
Year(s) Of Engagement Activity 2010
 
Description Go Cosmic - schools event 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? Yes
Primary Audience Schools
Results and Impact Two days spent at a centre in Buxton to which many school parties visited. Did sessions with both primary and secondary children, leaving them with projects to do when they got back to school.

I believe the whole scheme was well received, with good reports from many teachers.
Year(s) Of Engagement Activity 2010
 
Description Radio - naked scientists 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Primary Audience Public/other audiences
Results and Impact Gave radio interview for programme "Naked Scientists".

Programme was aired.
Year(s) Of Engagement Activity 2010
 
Description TV - Sky at night 2 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Primary Audience Public/other audiences
Results and Impact Contributed to BBC TV programme

Programme was aired
Year(s) Of Engagement Activity 2007
 
Description TV - Wonders of the Universe 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Primary Audience Public/other audiences
Results and Impact Consulted and gave interviews for BBC documentary "Wonders of the Universe". This resulted in two sets of programmes, one for UK/US and another for other countries.

Prime-time TV series with Brian Cox. Apparently well received.
Year(s) Of Engagement Activity 2010
 
Description TV - sky at night 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Primary Audience Public/other audiences
Results and Impact Contributed to a BBC TV program

Program was aired
Year(s) Of Engagement Activity 2006
 
Description Talk at 6th form college 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Primary Audience Schools
Results and Impact Talk to Physics Club at 6th form college in Cambridge. About 20 students attended.

Many questions.
Year(s) Of Engagement Activity 2006