In-orbit instrument performance study and calibration for POLAR polarization measurements

Li, Zheng-Heng; Kole, Merlin; Sun, Jiulin; Song, Liming; Produit, N.; Wu, B. B.; Bao, Tianwei; Bernasconi, T.; Cadoux, F.; Dong, Yongwei; Feng, M. Z.; Gauvin, N.; Hajdas, W.; Li, Hancheng; Li, Lü; Liu, Xin; Marcinkowski, R.; Pohl, M.; Rybka, D.; Shi, Hongyuan; Szabelski, J.; Tymieniecka, T.; Wang, Ruijie; Wang, Yuanhao; Wen, X. Y.; Wu, X.; Xiong, S. L.; Zwolinska, A.; Zhang, Li; Zhang, Laiyu; Zhang, Shuang‐Nan; Zhang, Yongjie; Zhao, Y.

doi:10.1016/j.nima.2018.05.041

Cited by 22 publications

(23 citation statements)

References 20 publications

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“…A significant number of detailed measurements from a dedicated gamma-ray polarimeter are required to allow for a more clear view of the polarization parameters of the prompt emission of GRBs. The POLAR mission, which underwent detailed calibration measurements both on ground (Kole et al 2017) and in orbit (Li et al 2018), thereby reducing systematic errors significantly, measured a total of 55 GRBs during the mission lifetime. Using these data here, we aim to provide the first catalog of detailed polarization measurements capable of resolving some of the open questions regarding GRBs.…”

Section: Introductionmentioning

confidence: 99%

The POLAR gamma-ray burst polarization catalog

Kole

Angelis²,

Berlato³

et al. 2020

A&A

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Context. Despite over 50 years of research, many open questions remain about the origin and nature of gamma-ray bursts (GRBs). Linear polarization measurements of the prompt emission of these extreme phenomena have long been thought to be key to answering a range of these questions. The POLAR detector was designed to produce the first set of detailed and reliable linear polarization measurements in the 50 − 500 keV energy range. During late 2016 and early 2017, POLAR detected a total of 55 GRBs. The analysis results of 5 of these GRBs have been reported, and were found to be consistent with a low or unpolarized flux. However, previous reports by other collaborations found high levels of linear polarization, including some as high as 90%. Aims. We study the linear polarization for the 14 GRBs observed by POLAR for which statistically robust inferences are possible. Additionally, time-resolved polarization studies are performed on GRBs with sufficient apparent flux. Methods. A publicly available polarization analysis tool, developed within the Multi-Mission Maximum Likelihood framework (3ML), was used to produce statistically robust results. The method allows spectral and polarimetric data from POLAR to be combined with spectral data from the Fermi Gamma-ray Burst Monitor (Fermi-GBM) and the Neil Gehrels Swift Observatory (hereafter Swift) to jointly model the spectral and polarimetric parameters. Results. The time-integrated analysis finds all results to be compatible with low or zero polarization with the caveat that, when timeresolved analysis is possible within individual pulses, we observe moderate linear polarization with a rapidly changing polarization angle. Therefore, time-integrated polarization results, while pointing to lower polarization, are potentially an artifact of summing over the changing polarization signal and thus washing out the true moderate polarization. We therefore caution against overinterpretation of any time-integrated results inferred herein and encourage the community to wait for more detailed polarization measurements from forthcoming missions such as POLAR-2 and LEAP.

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Section: Introductionmentioning

confidence: 99%

The POLAR gamma-ray burst polarization catalog

Kole

Angelis²,

Berlato³

et al. 2020

A&A

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“…This is however compensated by the large exposure time to the Crab pulsar. Event selection and data reduction applied here are based on the methods described in [17]. During this process the pedestals are subtracted, common noise is removed and cross talk and energy calibration are applied for each event.…”

Section: Observation and Data Reductionmentioning

confidence: 99%

“…During this process the pedestals are subtracted, common noise is removed and cross talk and energy calibration are applied for each event. Additionally cosmic ray events and triggers induced by anomalies in the electronics are removed using the methods described in detail in [17]. For this study additionally we binned the data into one second light curve and we excluded intervals with high background, thus defining Good Time Interval (GTI) which mainly include periods where the instrument was close to the South Atlantic Anomaly (SAA), GRBs and solar flares, etc.…”

Section: Observation and Data Reductionmentioning

confidence: 99%

Phase-resolved gamma-ray spectroscopy of the Crab pulsar observed by POLAR

Gauvin

et al. 2019

Journal of High Energy Astrophysics

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The POLAR detector is a space based Gamma-Ray Burst (GRB) polarimeter sensitive in the 15-500 keV energy range. Apart from its main scientific goal as a Gamma-Ray Burst polarimeter it is also able to detect photons from pulsars in orbit. By using the six-months in-orbit observation data, significant pulsation from the PSR B0531+21 (Crab pulsar) was obtained. In this work, we present the precise timing analysis of the Crab pulsar, together with a phase-resolved spectroscopic study using a joint-fitting method adapted for wide field of view instruments like POLAR. By using single power law fitting over the pulsed phase, we obtained spectral indices ranging from 1.718 to 2.315, and confirmed the spectral evolution in a reverse S shape which is homogenous with results from other missions over broadband. We will also show, based on the POLAR in-orbit performance and Geant4 Monte-Carlo simulation, the inferred capabilities of POLAR-2, the proposed follow-up mission of POLAR on board the China Space Station (CSS), for pulsars studies.

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“…All the raw data from POLAR are in the form of a data stream of binary packets generated by the Field-Programmable Gate Array (FPGA) which are not easy to analyze directly for science purposes. Therefore, pre-processing all the detection raw data and generating well-organized, high level scientific data products as quickly as possible are the first important steps and are required by the POLAR experiment for the following science analysis, such as data quick-look, in-orbit calibration (Li et al 2018), polarization analysis for the detected GRBs, etc. The requirements of data pre-processing and scientific data products generation for POLAR mainly include:…”

Section: Introductionmentioning

confidence: 99%

“…This pipeline can work automatically without manual intervention and will send an email to notify the researchers that new scientific data products have been generated. Up to now, with scientific data products generated by the pipeline of the current version, the in-orbit instrument performance study and calibration have been finished and are presented in Li et al 2018, and the first scientific results of POLAR have been produced and published in Zhang et al 2019 recently. This paper will give a detailed introduction of this pipeline and the main algorithms that are important and specially needed by POLAR.…”

Section: Introductionmentioning

confidence: 99%

Observation data pre-processing and scientific data products generation of POLAR

Li¹,

Sun²,

Song³

et al. 2019

Res. Astron. Astrophys.

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POLAR is a compact space-borne detector initially designed to measure the polarization of hard X-rays emitted from Gamma-Ray Bursts in the energy range 50-500 keV. This instrument was launched successfully onboard the Chinese space laboratory Tiangong-2 (TG-2) on 2016 September 15. After being switched on a few days later, tens of gigabytes of raw detection data were produced in-orbit by POLAR and transferred to the ground every day. Before the launch date, a full pipeline and related software were designed and developed for the purpose of quickly pre-processing all the raw data from POLAR, which include both science data and engineering data, then to generate the high level scientific data products that are suitable for later science analysis. This pipeline has been successfully applied for use by the POLAR Science Data Center in the Institute of High Energy Physics (IHEP) after POLAR was launched and switched on. A detailed introduction to the pipeline and some of the core relevant algorithms are presented in this paper.

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In-orbit instrument performance study and calibration for POLAR polarization measurements

Cited by 22 publications

References 20 publications

The POLAR gamma-ray burst polarization catalog

The POLAR gamma-ray burst polarization catalog

Phase-resolved gamma-ray spectroscopy of the Crab pulsar observed by POLAR

Observation data pre-processing and scientific data products generation of POLAR

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