Re-analysis of polarization in the γ-ray flux of GRB 021206

Robert E. Rutledge, Derek B. Fox

Research output: Contribution to journalArticle

119 Citations (Scopus)

Abstract

A previous analysis of the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observation of GRB 021206 found that the γ-ray flux was 80 ± 20 per cent polarized. We re-examine these data and find no signal that can be interpreted as due to polarization. First, we find that the number of scattering events suitable for measuring polarization - having been scattered from one detector to another, with a count produced in both - is considerably lower than estimated by Coburn & Boggs, by a factor of 10 (830 ± 150, versus 9840 ± 96). The signal-to-noise ratio of the data set is thus too low to produce a detection, even from a 100 per cent polarized source. None the less, we develop a polarization-detection analysis limited in sensitivity only by Poisson noise, which does not require a spacecraft mass model to detect polarization, as in Coburn & Boggs. We find no signal which might be interpreted as due to polarization of GRB 021206. Separately, we reproduce the Coburn & Boggs signal and show that it is not due to polarization. Rather, the Coburn & Boggs signal is consistent with the previously neglected systematic uncertainty in the 'null light curve' used for detection. Due to the low signal-to-noise ratio of the RHESSI data, our Poisson noise-limited analysis results in an upper limit consistent with 100 per cent polarization of the γ-ray flux from GRB 021206. Thus, no observational constraint on the polarization of GRB 021206 can be derived from these data.

Original languageEnglish (US)
Pages (from-to)1288-1300
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Volume350
Issue number4
DOIs
StatePublished - Jun 1 2004

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rays
polarization
solar energy
signal-to-noise ratio
signal to noise ratios
analysis
light curve
spacecraft
scattering
sensitivity
detectors
detection

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

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title = "Re-analysis of polarization in the γ-ray flux of GRB 021206",
abstract = "A previous analysis of the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observation of GRB 021206 found that the γ-ray flux was 80 ± 20 per cent polarized. We re-examine these data and find no signal that can be interpreted as due to polarization. First, we find that the number of scattering events suitable for measuring polarization - having been scattered from one detector to another, with a count produced in both - is considerably lower than estimated by Coburn & Boggs, by a factor of 10 (830 ± 150, versus 9840 ± 96). The signal-to-noise ratio of the data set is thus too low to produce a detection, even from a 100 per cent polarized source. None the less, we develop a polarization-detection analysis limited in sensitivity only by Poisson noise, which does not require a spacecraft mass model to detect polarization, as in Coburn & Boggs. We find no signal which might be interpreted as due to polarization of GRB 021206. Separately, we reproduce the Coburn & Boggs signal and show that it is not due to polarization. Rather, the Coburn & Boggs signal is consistent with the previously neglected systematic uncertainty in the 'null light curve' used for detection. Due to the low signal-to-noise ratio of the RHESSI data, our Poisson noise-limited analysis results in an upper limit consistent with 100 per cent polarization of the γ-ray flux from GRB 021206. Thus, no observational constraint on the polarization of GRB 021206 can be derived from these data.",
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Re-analysis of polarization in the γ-ray flux of GRB 021206. / Rutledge, Robert E.; Fox, Derek B.

In: Monthly Notices of the Royal Astronomical Society, Vol. 350, No. 4, 01.06.2004, p. 1288-1300.

Research output: Contribution to journalArticle

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AB - A previous analysis of the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observation of GRB 021206 found that the γ-ray flux was 80 ± 20 per cent polarized. We re-examine these data and find no signal that can be interpreted as due to polarization. First, we find that the number of scattering events suitable for measuring polarization - having been scattered from one detector to another, with a count produced in both - is considerably lower than estimated by Coburn & Boggs, by a factor of 10 (830 ± 150, versus 9840 ± 96). The signal-to-noise ratio of the data set is thus too low to produce a detection, even from a 100 per cent polarized source. None the less, we develop a polarization-detection analysis limited in sensitivity only by Poisson noise, which does not require a spacecraft mass model to detect polarization, as in Coburn & Boggs. We find no signal which might be interpreted as due to polarization of GRB 021206. Separately, we reproduce the Coburn & Boggs signal and show that it is not due to polarization. Rather, the Coburn & Boggs signal is consistent with the previously neglected systematic uncertainty in the 'null light curve' used for detection. Due to the low signal-to-noise ratio of the RHESSI data, our Poisson noise-limited analysis results in an upper limit consistent with 100 per cent polarization of the γ-ray flux from GRB 021206. Thus, no observational constraint on the polarization of GRB 021206 can be derived from these data.

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