POLAR-2: a large scale gamma-ray polarimeter for GRBs

The prompt emission of GRBs has been investigated for more than 50 years but remains poorly understood. Commonly, spectral and temporal profiles of γ-ray emission are analysed. However, they are insufficient for a complete picture on GRB-related physics. The addition of polarization measurements provides invaluable information towards the understanding of these astrophysical sources. In recent years, dedicated polarimeters, such as POLAR and GAP, were built. The former of which observed low levels of polarization as well as a temporal evolution of the polarization angle. It was understood that a larger sample of GRB polarization measurements and time resolved studies are necessary to constrain theoretical models. The POLAR-2 mission aims to address this by increasing the effective area by an order of magnitude compared to POLAR. POLAR-2 is manifested for launch on board the China Space Station in 2024 and will operate for at least 2 years. Insight from POLAR will aid in the improvement of the overall POLAR-2 design. Major improvements (compared to POLAR) will include the replacement of multi-anode PMTs (MAPMTs) with SiPMs, increase in sensitive volume and further technological upgrades. POLAR-2 is projected to measure about 50 GRBs per year with equal or better quality compared to the best seen by POLAR. The instrument design, preliminary results and anticipated scientific potential of this mission will be discussed.

[1]  Nicolas Produit,et al.  The POLAR gamma-ray burst polarization catalog , 2020, Astronomy & Astrophysics.

[2]  J. E. Hill,et al.  Performance of the PRAXyS X-Ray Polarimeter , 2016, 1610.06677.

[3]  Lifan Wang,et al.  The supernova-gamma-ray burst connection , 1998, astro-ph/9806212.

[4]  A. Beloborodov,et al.  Polarization of Gamma-Ray Bursts in the Dissipative Photosphere Model , 2016, 1611.01451.

[5]  Xilei Sun,et al.  Energy response of GECAM gamma-ray detector based on LaBr3:Ce and SiPM array , 2018, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment.

[6]  G. Olofsson,et al.  The design and flight performance of the PoGOLite Pathfinder balloon-borne hard X-ray polarimeter , 2015, 1508.03345.

[7]  Nicolas Produit,et al.  POLAR: Final calibration and in-flight performance of a dedicated GRB polarimeter , 2016, 2016 IEEE Nuclear Science Symposium, Medical Imaging Conference and Room-Temperature Semiconductor Detector Workshop (NSS/MIC/RTSD).

[8]  Xin Wu,et al.  Detailed polarization measurements of the prompt emission of five gamma-ray bursts , 2019, Nature Astronomy.

[9]  Nicolas Produit,et al.  In-orbit instrument performance study and calibration for POLAR polarization measurements , 2018, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment.

[10]  K. Toma.  Polarization of GRB Prompt Emission , 2013, 1308.5733.

[11]  Nicolas Produit,et al.  Design and construction of the POLAR detector , 2017, 1709.07191.

[12]  M. Moszynski,et al.  SiPM proton irradiation for application in cosmic space , 2020, Journal of Instrumentation.

[13]  Nicolas Produit,et al.  Instrument performance and simulation verification of the POLAR detector , 2017, 1708.00664.

[14]  L. S. Collaboration,et al.  Gravitational Waves and Gamma-rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A , 2017 .

[15]  F. Ryde,et al.  XL-Calibur – a second-generation balloon-borne hard X-ray polarimetry mission , 2020, 2010.10608.

[16]  M. Kole.  POLAR-2: The First Large Scale Gamma-ray Polarimeter , 2019, Proceedings of 36th International Cosmic Ray Conference — PoS(ICRC2019).

[17]  A. Kozyrev,et al.  A comparative study of LaBr3(Ce(3+)) and CeBr3 based gamma-ray spectrometers for planetary remote sensing applications. , 2016, The Review of scientific instruments.

[18]  Tanmoy Chattopadhyay,et al.  Prompt Emission Polarimetry of Gamma-Ray Bursts with the AstroSat CZT Imager , 2017, The Astrophysical Journal.

[19]  M. Feroci,et al.  eXTP: Enhanced X-ray Timing and Polarization mission , 2016, Astronomical Telescopes + Instrumentation.

[20]  L. A. Antonelli,et al.  Discovery of an X-ray afterglow associated with the γ-ray burst of 28 February 1997 , 1997, Nature.

[21]  C. Kouveliotou,et al.  Spatial distribution of γ-ray bursts observed by BATSE , 1992, Nature.

[22]  Fei Xie,et al.  In-flight calibration system of imaging x-ray polarimetry explorer , 2020, Journal of Astronomical Telescopes, Instruments, and Systems.

[23]  Riken,et al.  Gamma-Ray Burst Polarimeter (GAP) aboard the Small Solar Power Sail Demonstrator IKAROS , 2010, 1010.5305.

[24]  C. I. O. Technology.,et al.  Polarization of Prompt Gamma-Ray Burst Emission: Evidence for Electromagnetically Dominated Outflow , 2003, astro-ph/0305410.

[25]  A. Dell'Acqua,et al.  Geant4 - A simulation toolkit , 2003 .

[26]  C. Tseng,et al.  Polarimetric Analysis of the Long Duration Gamma-Ray Burst GRB 160530A With the Balloon Borne Compton Spectrometer and Imager , 2017, 1709.05349.