SPI-specific analysis method and software overview

Diehl, R.; Baby, N.; Beckmann, V.; Connell, P.; Dubath, P.; Jean, P.; Knödlseder, J.; Roques, J. P.; Schanne, S.; Shrader, C. R.; Skinner, G.; Strong, A. W.; Sturner, Steven J.; Teegarden, B. J.; Kienlin, A. von; Weiderspointner, G.

doi:10.1051/0004-6361:20031365

Cited by 29 publications

(29 citation statements)

References 15 publications

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“…The spectrum of GRB 041219a was extracted using specific GRB tools from the Online Software Analysis (Diehl et al 2003;Skinner & Connell 2003) version 5.0 available from the INTEGRAL Science Data Centre. GRB 041219a is the brightest burst localised by INTEGRAL with a peak flux of 43 ph cm −2 s −1 (20 keV-8 MeV).…”

Section: Spectral Analysismentioning

confidence: 99%

Polarisation studies of the prompt gamma-ray emission from GRB 041219a using the spectrometer aboard INTEGRAL

McGlynn

Clark

Dean

et al. 2007

A&A

155

138

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Context. Linear polarisation in gamma-ray burst prompt emission is an important diagnostic with the potential to significantly constrain models. The spectrometer aboard INTEGRAL, SPI, has the capability to detect the signature of polarised emission from a bright γ-ray source. GRB 041219a is the most intense burst localised by INTEGRAL with a fluence of 5.7 ×10 −4 erg cm −2 over the energy range 20 keV-8 MeV and is an ideal candidate for such a study. Aims. Polarisation can be measured using multiple events scattered into adjacent detectors because the Compton scatter angle depends on the polarisation of the incoming photon. A search for linear polarisation in the most intense pulse of duration 66 seconds and in the brightest 12 seconds of GRB 041219a was performed in the 100-350 keV, 100-500 keV and 100 keV-1 MeV energy ranges. It was possible to divide the events into six directions in the energy ranges of 100-350 keV and 100-500 keV using the kinematics of the Compton scatter interactions. Methods. The multiple event data from the spectrometer was analysed and compared with the predicted instrument response obtained from Monte-Carlo simulations using the GEANT 4 INTEGRAL mass model. The χ 2 distribution between the real and simulated data as a function of the percentage polarisation and polarisation angle was calculated for all three energy ranges. The degree and angle of polarisation were obtained from the best-fit value of χ 2 . Results. A weak signal consistent with polarisation was found throughout the analyses. The degree of linear polarisation in the brightest pulse of duration 66 s was found to be 63 +31 −30 % at an angle of 70 +14 −11 degrees in the 100-350 keV energy range. The degree of polarisation was also constrained in the brightest 12 s of the GRB and a polarisation fraction of 96 +39 −40 % at an angle of 60 +12 −14 degrees was determined over the same energy range. However, despite extensive analysis and simulations, a systematic effect that could mimic the weak polarisation signal could not be definitively excluded. Conclusions. Our results over several energy ranges and time intervals are consistent with a polarisation signal of about 60% but at a low level of significance (∼2σ). The polarisation results are compared with predictions from the synchrotron and Compton drag processes. The spectrum of this GRB can also be well fit by a combined black body and power law model which could arise from a combination of the Compton and synchrotron processes, with different degrees of polarisation. We therefore conclude that the procedure described here demonstrates the effectiveness of using SPI as a polarimeter, and is a viable method of measuring polarisation levels in intense gamma-ray bursts.

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Section: Spectral Analysismentioning

confidence: 99%

Polarisation studies of the prompt gamma-ray emission from GRB 041219a using the spectrometer aboard INTEGRAL

McGlynn

Clark

Dean

et al. 2007

A&A

155

138

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“…The spectra were extracted using specific GRB tools from the Online Software Analysis (Diehl et al 2003;Skinner & Connell 2003) version 5.1 available from the INTEGRAL Science Data Centre. The T 90 duration (the time for 5%-95% of the GRB counts to be recorded) was determined using the lightcurve generated from the IBIS/ISGRI data in 1 s bins.…”

Section: Spectral Analysismentioning

confidence: 99%

High energy emission and polarisation limits for the INTEGRAL burst GRB 061122

McGlynn

Foley

McBreen

et al. 2009

A&A

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Context. GRB 061122 is one of the brightest GRBs detected within INTEGRAL's field of view to date, with a peak flux (20-200 keV) of 32 photons cm −2 s −1 and fluence of 2 × 10 −5 erg cm −2 . The Spectrometer aboard INTEGRAL, SPI, can measure linear polarisation in bright GRBs through the process of Compton scattering in the Germanium detectors. Polarisation measurements of the prompt emission are relatively rare. The spectral and polarisation results can be combined to provide vital information about the circumburst region. Aims. The two γ-ray detectors on INTEGRAL were used to investigate the spectral characteristics of GRB 061122. A search for linear polarisation in the prompt emission was carried out on GRB 061122 using the SPI multiple event data in the energy range 100 keV-1 MeV. The X-ray properties were examined using data from the X-Ray Telescope (XRT) on Swift. Methods. The γ-ray spectral and temporal properties of GRB 061122 were determined using IBIS and SPI. The afterglow properties were obtained using XRT. The multiple event data of GRB 061122 from SPI were analysed and compared with the predicted instrument response obtained from Monte-Carlo simulations using the GEANT 4 INTEGRAL mass model. The χ 2 distributions between the real and simulated data as a function of the percentage polarisation and polarisation angle were calculated and limits on the level and angle of polarisation were obtained from the best-fit value of χ 2 . Results. The prompt spectrum was best fit by a combination of a blackbody and a power-law model (the quasithermal model), with evidence for high energy emission continuing above 8 MeV. A pseudo-redshift value of pz = 0.95 ± 0.18 was determined using the spectral fit parameters. The isotropic energy at this pseudo-redshift is 8.5 × 10 52 erg. The jet opening angle was estimated to be smaller than 2.8 • or larger than 11.9 • from the X-ray lightcurve. An upper limit of 60% polarisation was determined for the prompt emission of GRB 061122, using the multiple event data from the spectrometer on INTEGRAL. Conclusions. The high energy emission observed in the spectrum may be due to the reverse shock interacting with the GRB ejecta when it is decelerated by the circumburst medium. This behaviour has been observed in a small fraction of GRBs to date, but is expected to be more commonly observed by the Fermi Gamma-ray Space Telescope. The conditions for polarisation are met if the jet opening angle is less than 2.8 • , but further constraints on the level of polarisation are not possible.

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“…The algorithms implemented in the software are described in Goldwurm et al (2003) for IBIS, Westergaard et al (2003) for JEM-X, and Diehl et al (2003) for SPI. The IBIS/ISGRI, SPI and JEM-X data have been accumulated into final images.…”

Section: Observations and Data Analysismentioning

confidence: 99%

INTEGRAL observations of the blazar 3C 454.3 in outburst

Pian

Foschini

Beckmann

et al. 2006

A&A

Self Cite

103

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In Spring 2005, the blazar 3C 454.3 underwent a dramatic outburst at all wavelengths from mm to X-rays. This prompted INTEGRAL observations, accomplished in 15−18 May 2005. The source was detected by the INTEGRAL instruments from 3 to 200 keV in a bright state (∼5 × 10 −10 erg s −1 cm −2 ), at least a factor of 2−3 higher than previously observed. This is one of the brightest blazar detections achieved by INTEGRAL. During the 2.5 days of INTEGRAL monitoring, we detected a ∼20% decrease in the hard X-rays (20−40 keV), indicating that we have sampled the decaying part of the flare. The decrease is less apparent in the soft X-rays (5−15 keV). The simultaneous optical variations are weakly correlated with those at soft X-rays, and not clearly correlated with those at hard X-rays. The spectral energy distribution exhibits two components, as typically seen in blazars, which can be modeled with synchrotron radiation and inverse Compton scattering occurring in a region external to the broad line region.

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SPI-specific analysis method and software overview

Cited by 29 publications

References 15 publications

Polarisation studies of the prompt gamma-ray emission from GRB 041219a using the spectrometer aboard INTEGRAL

Polarisation studies of the prompt gamma-ray emission from GRB 041219a using the spectrometer aboard INTEGRAL

High energy emission and polarisation limits for the INTEGRAL burst GRB 061122

INTEGRAL observations of the blazar 3C 454.3 in outburst

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