Final Report Summary - GRB-SMB-2008 (Gamma-ray bursts - Current and Future)
This project pertains to the study of astrophysical explosions called gamma-ray bursts (GRBs) which release a huge amount of energy in the gamma-ray energy band over a few minutes followed by a slower decay at longer wavelengths in the weeks following the initial trigger. These events are detected by orbiting satellites equipped with wide-field gamma-ray sensors (e.g. GRB monitor (GBM) on NASA's Fermi mission or the burst alert telescope on NASA's Swift satellite). Once an increase in the gamma-ray rate is detected onboard, the instrument 'triggers' and the coordinates on the sky are sent to observers who use more precise instruments to obtain a better localisation. This is necessary to enable them to find the glowing embers of the explosion, to learn about the star(s) which exploded, the galaxies which host them and the distance to the source. The latter is particularly important in order to determine the total energy budget of the explosion (about 10^54 erg). In the absence of a distance estimate, the event could be very distant and very energetic, or very near and relatively weak. An understanding of the energy output is vital for theoretical work.
The aims of this project were two-fold:
1) investigate the prompt emission and afterglows of GRBs; and
2) investigate and advance the technological case for the next generation space mission in the gamma-ray regime.
In part 1) of the project, the researcher (hereafter awardee) investigated the gamma-ray emission from GRBs detected by the GBM and the higher energy instrument, the Large Area Telescope (LAT). The former is sensitive from 10 keV to 40 MeV and the latter from tens of MeV to hundreds of GeV. As part of this project, the awardee continued in her role as a Fermi / GBM and Fermi GRB science group member which began when she was a Marie Curie Intra-European Fellow in the Max Planck for extraterrestrial physics (MPE). One aspect of the work involved participating the daily shifts to analyse GRBs. The preliminary results of this work were published in over 80 bulletin type reports called gamma-ray burst coordinate network circulars. These short reports are published promptly to inform the scientific community of the type of event that has occurred. More detailed results were published in GBM team papers, for example the first trigger and spectral catalogs:
- Paciesas et al., 'The Fermi GBM Gamma-Ray Burst Catalog: The First Two Years', The Astrophysical Journal Supplement, Volume 199, 18 (2012), and
- Goldstein et al., 'The Fermi GBM Gamma-Ray Burst Spectral Catalog: The First Two Years', The Astrophysical Journal Supplement, Volume 199, 19 (2012).
The fluxes, fluences and spectral characteristics of over 400 GRBs detected in the first two years of operations were presented in these papers. The GBM team published over fifteen papers on GRBs during the lifetime of the project.
As part of the Fermi collaboration, the applicant also worked in the GRB science group which focused on bursts detected not only by the GBM instrument, but also by the LAT at MeV - GeV energies. Bursts detected at higher energies are rarer, but extremely interesting. One particular example is GRB090902B which was discovered to have an unusual spectrum. The results of the GBM and LAT were published in a paper on which the applicant was a coordinating author:
- Abdo et al., 'Fermi Observations of GRB 090902B: A Distinct Spectral Component in the Prompt and Delayed Emission', The Astrophysical Journal Letters, Volume 706, L138-L144 (2009).
The paper has been cited 148 times to date. A number of other important papers were published by the team, for example an investigation in to the possible effects of quantum gravity on the speed of photons of different energies published in Nature. Abdo et al., 'A limit on the variation of the speed of light arising from quantum gravity effects', Nature, Volume 462, Issue 7271, pp. 331 - 334 (2009). These results depended crucially on the distance determination published by McBreen et al. (2010) (see below). The applicant was involved as an author in ten papers by the GRB science group and also acted as one of the group coordinator for one year. The travel funds available to the awardee via this project, made her role as coordinator feasible. It would not have been possible to take on this role in the absence of funding.
Apart from the studies of the properties of GRBs detected at high energies, the awardee also worked on the afterglows of these events, in particular the afterglows of bursts detected by the Fermi / LAT. The reason that these events were of special interest is that they had photons detected up to very high energies and the afterglows were required to determine the distance to the source (redshift) and hence the energetics. Moreover, the precision of the location determined by the LAT was more precise and enabled more productive studies. To facilitate this part of the project, the applicant submitted a proposal to the European Southern Observatory (ESO) to conduct follow-up studies using the Very Large Telescope facility in Chile. The large telescopes were used to obtain spectra of the afterglow and host galaxies of GRBs detected initially by Fermi and subsequently by other instruments such as the Swift X-Ray Telescope and the GROND multi band imager on the Max Planck / ESO 2.2 m telescope (Principal Investigator (PI): Greiner at MPE). The results of this study were published in a couple of papers:
- McBreen et al., 'Optical and near-infrared follow-up observations of four Fermi/LAT GRBs: redshifts, afterglows, energetics, and host galaxies', Astronomy and Astrophysics, 516, A71 (2010), and
- Rau et al., 'A Very Metal-poor Damped Lyman-alpha System Revealed Through the Most Energetic GRB 090926A', The Astrophysical Journal, Volume 720, 862-871 (2010).
These papers have been cited 40 and 38 times respectively. Among the important results published by McBreen et al. (2010) were the overall energetics of bursts detected by the Fermi / LAT and the distance to GRB090510, without which the quantum gravity limits of Abdo et al. 2009 could not have been obtained. A rare host galaxy metallicity measurement was published by Rau et al. (2010). As part of this project, the awardee was an author of seven papers on the afterglows and host galaxies of GRBs.
The applicant also presented her work at several conferences and workshops including as an invited speaker at the Munich GRB2012 conference.
In part 2) of this project, the aim was to develop the case for one of the proposed future gamma-ray missions. The applicant is a member of the Gamma-Ray Imaging, Polarimetry and Spectroscopy (GRIPS) and as part of this project has investigated the suitability of silicon photomultiplier (SiPM) technology from SensL for the calorimeter of the instrument. Traditional photomultiplier tubes (PMTs) are not suitable for GRIPs because of the mass budget and resolution. In order for the calorimeter to be viable, more lightweight solutions such as SiPMs are required. As part of the effort on the mission, a proposal was submitted by the collaboration to the European Space Agency (ESA)'s Cosmic Vision (Greiner et al., 2011, 'GRIPS - Gamma-Ray Imaging, Polarimetry and Spectroscopy', Experimental Astronomy); unfortunately, the mission was not selected for a detailed study by ESA at this time. More work needs to be done to make a stronger future case and this work is continuing via hardware testing and simulations using the MEGAlib package in UCD. The applicant successfully obtained funding (as co-PI) from ESA for the following project: 'Novel silicon photomultiplier configurations for high-energy detection in space'.
The awardee presented talks on this part of the project at several meetings including the EMMI Workshop on Opportunities for Nuclear Astrophysics in Space in GSI, Darmstadt.
The funding obtained via this project, enabled travel for the awardee and her students to conferences, workshops and collaboration meetings without which participation in the Fermi team and maintaining connections with colleagues in Europe and the United States of America (USA) would not have been possible. Moreover, the project funded collaboration visits from colleagues from MPE (e.g. Dr Andreas von Kienlin and David Gruber), the USA (e.g. Dr Michael Briggs) and the author of MEGAlib (e.g. Dr Andreas Zoglauer).
The awardee has obtained tenure in University College in 2012. The reintegration grant was crucial in maintaining a research profile and international contacts during the three years of employment prior to the tenure application.
The aims of this project were two-fold:
1) investigate the prompt emission and afterglows of GRBs; and
2) investigate and advance the technological case for the next generation space mission in the gamma-ray regime.
In part 1) of the project, the researcher (hereafter awardee) investigated the gamma-ray emission from GRBs detected by the GBM and the higher energy instrument, the Large Area Telescope (LAT). The former is sensitive from 10 keV to 40 MeV and the latter from tens of MeV to hundreds of GeV. As part of this project, the awardee continued in her role as a Fermi / GBM and Fermi GRB science group member which began when she was a Marie Curie Intra-European Fellow in the Max Planck for extraterrestrial physics (MPE). One aspect of the work involved participating the daily shifts to analyse GRBs. The preliminary results of this work were published in over 80 bulletin type reports called gamma-ray burst coordinate network circulars. These short reports are published promptly to inform the scientific community of the type of event that has occurred. More detailed results were published in GBM team papers, for example the first trigger and spectral catalogs:
- Paciesas et al., 'The Fermi GBM Gamma-Ray Burst Catalog: The First Two Years', The Astrophysical Journal Supplement, Volume 199, 18 (2012), and
- Goldstein et al., 'The Fermi GBM Gamma-Ray Burst Spectral Catalog: The First Two Years', The Astrophysical Journal Supplement, Volume 199, 19 (2012).
The fluxes, fluences and spectral characteristics of over 400 GRBs detected in the first two years of operations were presented in these papers. The GBM team published over fifteen papers on GRBs during the lifetime of the project.
As part of the Fermi collaboration, the applicant also worked in the GRB science group which focused on bursts detected not only by the GBM instrument, but also by the LAT at MeV - GeV energies. Bursts detected at higher energies are rarer, but extremely interesting. One particular example is GRB090902B which was discovered to have an unusual spectrum. The results of the GBM and LAT were published in a paper on which the applicant was a coordinating author:
- Abdo et al., 'Fermi Observations of GRB 090902B: A Distinct Spectral Component in the Prompt and Delayed Emission', The Astrophysical Journal Letters, Volume 706, L138-L144 (2009).
The paper has been cited 148 times to date. A number of other important papers were published by the team, for example an investigation in to the possible effects of quantum gravity on the speed of photons of different energies published in Nature. Abdo et al., 'A limit on the variation of the speed of light arising from quantum gravity effects', Nature, Volume 462, Issue 7271, pp. 331 - 334 (2009). These results depended crucially on the distance determination published by McBreen et al. (2010) (see below). The applicant was involved as an author in ten papers by the GRB science group and also acted as one of the group coordinator for one year. The travel funds available to the awardee via this project, made her role as coordinator feasible. It would not have been possible to take on this role in the absence of funding.
Apart from the studies of the properties of GRBs detected at high energies, the awardee also worked on the afterglows of these events, in particular the afterglows of bursts detected by the Fermi / LAT. The reason that these events were of special interest is that they had photons detected up to very high energies and the afterglows were required to determine the distance to the source (redshift) and hence the energetics. Moreover, the precision of the location determined by the LAT was more precise and enabled more productive studies. To facilitate this part of the project, the applicant submitted a proposal to the European Southern Observatory (ESO) to conduct follow-up studies using the Very Large Telescope facility in Chile. The large telescopes were used to obtain spectra of the afterglow and host galaxies of GRBs detected initially by Fermi and subsequently by other instruments such as the Swift X-Ray Telescope and the GROND multi band imager on the Max Planck / ESO 2.2 m telescope (Principal Investigator (PI): Greiner at MPE). The results of this study were published in a couple of papers:
- McBreen et al., 'Optical and near-infrared follow-up observations of four Fermi/LAT GRBs: redshifts, afterglows, energetics, and host galaxies', Astronomy and Astrophysics, 516, A71 (2010), and
- Rau et al., 'A Very Metal-poor Damped Lyman-alpha System Revealed Through the Most Energetic GRB 090926A', The Astrophysical Journal, Volume 720, 862-871 (2010).
These papers have been cited 40 and 38 times respectively. Among the important results published by McBreen et al. (2010) were the overall energetics of bursts detected by the Fermi / LAT and the distance to GRB090510, without which the quantum gravity limits of Abdo et al. 2009 could not have been obtained. A rare host galaxy metallicity measurement was published by Rau et al. (2010). As part of this project, the awardee was an author of seven papers on the afterglows and host galaxies of GRBs.
The applicant also presented her work at several conferences and workshops including as an invited speaker at the Munich GRB2012 conference.
In part 2) of this project, the aim was to develop the case for one of the proposed future gamma-ray missions. The applicant is a member of the Gamma-Ray Imaging, Polarimetry and Spectroscopy (GRIPS) and as part of this project has investigated the suitability of silicon photomultiplier (SiPM) technology from SensL for the calorimeter of the instrument. Traditional photomultiplier tubes (PMTs) are not suitable for GRIPs because of the mass budget and resolution. In order for the calorimeter to be viable, more lightweight solutions such as SiPMs are required. As part of the effort on the mission, a proposal was submitted by the collaboration to the European Space Agency (ESA)'s Cosmic Vision (Greiner et al., 2011, 'GRIPS - Gamma-Ray Imaging, Polarimetry and Spectroscopy', Experimental Astronomy); unfortunately, the mission was not selected for a detailed study by ESA at this time. More work needs to be done to make a stronger future case and this work is continuing via hardware testing and simulations using the MEGAlib package in UCD. The applicant successfully obtained funding (as co-PI) from ESA for the following project: 'Novel silicon photomultiplier configurations for high-energy detection in space'.
The awardee presented talks on this part of the project at several meetings including the EMMI Workshop on Opportunities for Nuclear Astrophysics in Space in GSI, Darmstadt.
The funding obtained via this project, enabled travel for the awardee and her students to conferences, workshops and collaboration meetings without which participation in the Fermi team and maintaining connections with colleagues in Europe and the United States of America (USA) would not have been possible. Moreover, the project funded collaboration visits from colleagues from MPE (e.g. Dr Andreas von Kienlin and David Gruber), the USA (e.g. Dr Michael Briggs) and the author of MEGAlib (e.g. Dr Andreas Zoglauer).
The awardee has obtained tenure in University College in 2012. The reintegration grant was crucial in maintaining a research profile and international contacts during the three years of employment prior to the tenure application.