Abstract
This paper compares the population of binary black hole (BBH) mergers detected by LIGO/Virgo with selected long gamma-ray burst (GRB) world models convolved with a delay function (LGRBs are ...used as a tracer of stellar-mass BH formation). The comparison involves the redshift distribution and the fraction of LGRBs required to produce the local rate of BBH mergers. We find that BBH mergers and LGRBs cannot have the same formation history, unless BBH mergers have a long coalescence time of several Gyr. This would imply that BHs born during the peak of long GRB formation at redshift
z
≈ 2−3 merge within the horizon of current GW interferometers. We also show that LGRBs are more numerous than BBH mergers, meaning that most of them do not end their lives in BBH mergers. We interpret these results as an indication that BBH mergers and LGRBs constitute two distinct populations of stellar-mass BHs, with LGRBs being more frequent than BBH mergers. We speculate that the descendants of LGRBs may resemble galactic high-mass X-ray binaries more than BBH mergers. Finally, we discuss the possible existence of a subpopulation of fast-spinning LGRB descendants among BBH mergers, showing that this population, if it exists, is expected to become dominant beyond redshift
z
≈ 1, leading to a change in the observed properties of BBH mergers.
Context. The Space-based multi-band astronomical Variable Objects Monitor is a Chinese-French mission dedicated to the study of the transient sky. It is scheduled to start operations in 2024. ECLAIRs ...is a coded-mask telescope with a large field of view. It is designed to detect and localize gamma-ray bursts in the energy range from 4 keV up to 120 keV. In 2021, the ECLAIRs telescope underwent various calibration campaigns in vacuum test-chambers to evaluate its performance. Between 4 and 8 keV, the counting response of the detection plane shows inhomogeneities between pixels from different production batches. The efficiency inhomogeneity is caused by low-efficiency pixels (LEPs) from one of the two batches, together with high-threshold pixels (HTPs) whose threshold was raised to avoid cross-talk effects. In addition, some unexpected noise was found in the detection plane regions close to the heat pipes. Aims. We study the impact of these inhomogeneities and of the heat-pipe noise at low energies on the ECLAIRs onboard triggers. We propose different strategies in order to mitigate these impacts and to improve the onboard trigger performance. Methods. We analyzed the data from the calibration campaigns and performed simulations with the ground model of the ECLAIRs trigger software in order to design and evaluate the different strategies. Most of the impact of HTPs can be corrected for by excluding HTPs from the trigger processing. To correct for the impact of LEPs, an efficiency correction in the shadowgram seems to be a good solution. An effective solution for the heat-pipe noise is selecting the noisy pixels and ignoring their data in the 4–8 keV band during the data analysis. Results. The trigger threshold is the minimum value of the signal-to-noise ratio that is required to claim that ECLAIRs has detected a candidate event that is not related to a background fluctuation. After introducing the efficiency inhomogeneity in the imaging simulation, the trigger threshold in the 4–8 keV band increased by a factor of 5.75 times and 1.43 times due to the impact of HTPs and LEPs, respectively, in the worst case (on a timescale of about 20 min). The trigger threshold value was restored to its normal value after we applied an efficiency-correction method. Introducing the heat-pipe noise in our simulations in the worst case (timescale of about 20 min) resulted in an increase in the trigger threshold of approximately 100% in the 4–8 keV band compared to observations without heat-pipe noise. Moreover, even with this increased threshold, we estimated a false-trigger rate of 99.26% in the 4–8 keV band and 4.44% in the 4-120 keV band. By accepting a loss of 2.5-5% noisy pixels in the 4–8 keV energy band, we can prevent false triggers caused by heat-pipe noise and reduce the threshold increment to about 20% for the longest timescale (about 20 min) of the ECLAIRs trigger in the 4–8 keV range.
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Ultra-long Gamma-Ray Bursts (ulGRBs) are Gamma-Ray Bursts (GRBs) with an unusually long emission in X and gamma rays, reaching durations of thousands of seconds. They could form a specific class of ...high-energy transient events, whose origin is still under discussion. The current sample of known ulGRBs consists of a few tens of events which have been detected so far by the Burst Alert Telescope (BAT) aboard the Neil Gehrels Swift Observatory and some other instruments. The SVOM mission which is scheduled to begin operations after 2021 could help to detect and observe more ulGRBs thanks to its soft gamma-ray telescope ECLAIRs. After an introduction on ulGRBs and the SVOM mission, we present the results of our simulations on the capabilities of ECLAIRs to detect ulGRBs. First we use the sample of ulGRBs detected by Swift/BAT and simulate these events through a model of the instrument and the prototype trigger software that will be implemented onboard ECLAIRs. Then we present a study of the ECLAIRs capabilities to detect a synthetic population of ulGRBs built by transporting the ulGRBs detected by Swift/BAT to higher redshifts. Finally we give an estimate of the ulGRB rate expected to be detected by ECLAIRs and show that ECLAIRs can detect at least as much ulGRBs as BAT.
The
Space Variable Object Monitor (SVOM)
is a forthcoming Chinese - French astrophysics space mission dedicated to the study of Gamma-ray bursts and high-energy transients. ECLAIRs, a wide-field hard ...X-ray coded mask imager, is the leading instrument for the transient detection and their first localisation. The sensitivity of such instruments is usually limited by the background, either of instrumental or astrophysical origin. Detailed estimations of the background are obtained by simulating the interaction of particles with the matter using, in the present case, the GEANT4 Monte-Carlo toolkit. However, this is a time consuming process, especially when it is needed to carry out all possible geometrical and orbital configurations. Instead, we present a much faster method that allows computing the background in either a static or dynamic (time dependent) way. The method is based on the preliminary calculation of a large particle database using the GEANT4 toolkit followed by a selection process based on the incoming direction and energy of the particles. This approach is as accurate as direct Monte-Carlo methods, while it reduces the computation time by a factor of 10
3
− 10
4
for our application. We apply this method to compute the SVOM/ECLAIRs dynamic background.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The use of high energy transients such as Gamma Ray Bursts (GRBs) as probes of the distant universe relies on the close collaboration between space and ground facilities. In this context, the ...Sino-French mission
SVOM
has been designed to combine a space and a ground segment and to make the most of their synergy. On the ground, the 1.3 meter robotic telescope COLIBRI, jointly developed by France and Mexico, will quickly point the sources detected by the space hard X-ray imager ECLAIRs, in order to detect and localise their visible/NIR counterpart and alert large telescopes in minutes. COLIBRI is equipped with two visible cameras, called DDRAGO-blue and DDRAGO-red, and an infrared camera, called CAGIRE, designed for the study of high redshift GRBs candidates. Being a low-noise NIR camera mounted at the focus of an alt-azimutal robotic telescope imposes specific requirements on CAGIRE. We describe here the main characteristics of the camera: its optical, mechanical and electronics architecture, the ALFA detector, and the operation of the camera on the telescope. The instrument description is completed by three sections presenting the calibration strategy, an image simulator incorporating known detector effects, and the automatic reduction software for the ramps acquired by the detector. This paper aims at providing an overview of the instrument before its installation on the telescope.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Context. Gamma-ray bursts (GRBs) can be detected at cosmological distances, and therefore can be used to study the contents and phases of the early Universe. The 4−150 keV wide-field trigger camera ...ECLAIRs on board the Space-based multi-band Variable Object Monitor (SVOM) mission, dedicated to studying the high-energy transient sky in synergy with multi-messenger follow-up instruments, has been adapted to detect high- z GRBs. Aims. Investigating the detection capabilities of ECLAIRs for high-redshift GRBs and estimating the impacts of instrumental biases in reconstructing some of the source measured properties, focusing on GRB duration biases as a function of redshift. Methods. We simulated realistic detection scenarios for a sample of 162 already observed GRBs with known redshift values as they would have been seen by ECLAIRs. We simulated them at redshift values equal to and higher than their measured value. Then we assessed whether they would be detected with a trigger algorithm resembling that on board ECLAIRs, and derived quantities, such as T 90 , for those that would have been detected. Results. We find that ECLAIRs would be capable of detecting GRBs up to very high redshift values (e.g. 20 GRBs in our sample are detectable within more than 0.4 of the ECLAIRs field of view for z sim > 12). The ECLAIRs low-energy threshold of 4 keV, contributes to this great detection capability, as it may enhance it at high redshift ( z > 10) by over 10% compared with a 15 keV low-energy threshold. We also show that the detection of GRBs at high- z values may imprint tip-of-the-iceberg biases on the GRB duration measurements, which can affect the reconstruction of other source properties.
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In this paper, we discuss the need for very large detection planes for the detection of hard X-ray transients in the multi-messenger era, started with the quasi-simultaneous detection of GRB 170817A ...by
Fermi
/GBM and
INTEGRAL
/SPI and the gravitational waves event GW 170817, detected by the LVC collaboration.
After pointing that current and future instruments gain in the number of GRBs thanks to their larger field of view rather than to their larger effective area, we address various problems associated with the realization of very large detection planes
(≥ 1m
2
).
Based on our experience with
SVOM
/ECLAIRs, we demonstrate that CdTe detectors are well suited for this task.
We conclude with a discussion of some key parameters that must be taken into account in the realization of instruments based on these detectors. We hope that this paper will contribute to promote the construction of large area wide-field hard X-ray monitors that will be crucially needed in the next decade.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Context. The Space-based multi-band astronomical Variable Objects Monitor is a Chinese-French mission dedicated to the study of the transient sky. It is scheduled to start operations in 2024. ECLAIRs ...is a coded-mask telescope with a large field of view. It is designed to detect and localize gamma-ray bursts in the energy range from 4 keV up to 120 keV. In 2021, the ECLAIRs telescope underwent various calibration campaigns in vacuum test-chambers to evaluate its performance. Between 4 and 8 keV, the counting response of the detection plane shows inhomogeneities between pixels from different production batches. The efficiency inhomogeneity is caused by low-efficiency pixels (LEPs) from one of the two batches, together with high-threshold pixels (HTPs) whose threshold was raised to avoid cross-talk effects. In addition, some unexpected noise was found in the detection plane regions close to the heat pipes.Aims. We study the impact of these inhomogeneities and of the heat-pipe noise at low energies on the ECLAIRs onboard triggers. We propose different strategies in order to mitigate these impacts and to improve the onboard trigger performance.Methods. We analyzed the data from the calibration campaigns and performed simulations with the ground model of the ECLAIRs trigger software in order to design and evaluate the different strategies. Most of the impact of HTPs can be corrected for by excluding HTPs from the trigger processing. To correct for the impact of LEPs, an efficiency correction in the shadowgram seems to be a good solution. An effective solution for the heat-pipe noise is selecting the noisy pixels and ignoring their data in the 4–8 keV band during the data analysis.Results. The trigger threshold is the minimum value of the signal-to-noise ratio that is required to claim that ECLAIRs has detected a candidate event that is not related to a background fluctuation. After introducing the efficiency inhomogeneity in the imaging simulation, the trigger threshold in the 4–8 keV band increased by a factor of 5.75 times and 1.43 times due to the impact of HTPs and LEPs, respectively, in the worst case (on a timescale of about 20 min). The trigger threshold value was restored to its normal value after we applied an efficiency-correction method. Introducing the heat-pipe noise in our simulations in the worst case (timescale of about 20 min) resulted in an increase in the trigger threshold of approximately 100% in the 4–8 keV band compared to observations without heat-pipe noise. Moreover, even with this increased threshold, we estimated a false-trigger rate of 99.26% in the 4–8 keV band and 4.44% in the 4-120 keV band. By accepting a loss of 2.5-5% noisy pixels in the 4–8 keV energy band, we can prevent false triggers caused by heat-pipe noise and reduce the threshold increment to about 20% for the longest timescale (about 20 min) of the ECLAIRs trigger in the 4–8 keV range.
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