PoGOLite, PoGO+, SPHiNX High-Energy Polarimetry Missions between Japan and Sweden Hiromitsu Takahashi (Hiroshima University) hirotaka@astro.hiroshima-u.ac.jp PoGOLite balloon 10m (2013) PoGO+ balloon 10m (2016) SPHiNX satellite 0.5m (Plan: 2021~) 1
Polarized Gamma-ray Observer (PoGO) Sweden (KTH, Stockholm Univ., Esrange, DST Control) Japan (Hiroshima Univ., Nagoya Univ., Waseda Univ., Tokyo Tech., ISAS/JAXA) PI: Mark Pearce (KTH, Royal Institute of Technology) http://web.particle.kth.se/pogo/ PoGOLite balloon 10m (2013) PoGO+ balloon 10m (2016) SPHiNX satellite 0.5m (Plan: 2021~) 2
Crab Synchrotron emission: - Rotation-powered neutron stars (e.g. Crab pulsar) - Pulsar wind nebulae (e.g. Crab nebula) - Jets in active galactic nuclei (e.g. Mkn 501, 1E1959+65) - Gamma-ray bursts Compton scattering: - Accretion disk around black holes (e.g. Cygnus X-1) Propagation in strong magnetic field: - Highly magnetized neutron stars (e.g. Hercules X-1, Magnetars) Cygnus X-1 Scattering Synchrotron emission 3
- Polarization measurements in X/gamma-rays have been expected to provide a powerful probe into high-energy emission mechanism around pulsars, black hole binaries, active galactic nuclei etc. - However, X/gamma-ray polarization has been measured only GRBs and at 2.6/5.2 kev and above 200 kev from the Crab nebula and Cyg X-1. - Additional measurements (middle10s kev band / other sources) are needed (New missions: X-Calibur, Hitomi, Astrosat, IXPE, XIPE, ). (c) astro.psu.edu Gamma-ray (20-120 kev) ~40 km 4
- PoGOLite and PoGO+, are a balloon experiment of Compton kinematics with the capability of detecting 10% polarization from a 1 Crab celestial object in the energy-range 20 120 kev. (1 Crab ~ 0.2 photons/s/cm2 @30 kev, power-law index ~ 2.1) - The project is international collaboration including Japan and Sweden. - Their flights took place in the summer of 2013 & 2016 from Sweden. (c) astro.psu.edu Gamma-ray (20-120 kev) ~40 km Weight (wo ballast) : ~1750 kg Power : ~300 W (Instrument) ~200 W (Gondola, etc.) 5
Flight Plan (1-day long) Crab nebula (Pulsar) Cyg X-1 (Black hole binary) (c) ESA Solar flare (c) JAXA (c) astro.psu.edu PoGO: - large effective area, low background => Suitable for bright sources. - long exposure => high statistics, variability, flaring activities. 6
- PoGOLite: 2 weeks: July 12~26, 2013 from Sweden to Russia (Unfortunately) the polarimeter worked only 3 days (Crab: 3 times) - PoGO+: 7 days: July 12~18, 2016 from Sweden to Canada Many updates from PoGOLite We performed observations of (Crab: 7 times, Cyg X-1: 6 times) 7
- PoGO captures a pair of Compton scattering and photoabsorption for one X/gamma-ray event with 61 phoswich detector cells, and measure the azimuthal angle anisotropy of Compton-scattering. - Instrument is rotated (6 mins/rotation) to cancel instrumental systematics. Gamma-ray 1.5 m Top view Pb/Sn/Cu collimator Fast plastic scintillator (12-cm long) BGO scintillator 40 cm One direction detects more events Polyethylene shield 8
Preliminary 9
Preliminary 1000 events - As same as PoGOLite in 2013, we managed to detect Crab pulsation (33 ms) in 2016 flight data using only polarization information (2 hits of Compton + photoabsorption). - Polarization analysis is on-going for Crab and Cyg X-1. 10
Counts 200 events PoGOLite (20-110 kev) Suzaku/PIN (10-70 kev) Phase There are 4 papers: M. Chauvin et al. (2015, 2016abc) - 3 papers about ground calibration, flight and polarization analysis - 1 about the update from PoGOLite to PoGO+ 11
Polarization angle Polarization degree Polarization: 20-120 kev, phase averaged degree:(18.4, +9.8, -10.6)% <= 99% U.L. 42.4% angle:(149.2 ± 16.0) (M. Chauvin et al. 2016) 12
SPHiNX (Segmented Polarimeter for High energy X-rays) Scientific goals: Emission mechanism of gamma-ray burst jets (Synchrotron + photosphere?) Scatter: Plastic + PMT Absorber: GAGG (or BGO) scintillator +APD or SiPM 30 cm - GRB dedication (50-500 kev), 25 / year - Large effective area for polarization: 70 cm 2 - Swedish satellite (50 kg), Japan contributes detector and ground station. <= Low inclination (close to equator) orbit is better for low background. - Currently Phase-A/B1 and will be selected in 2017 end 13 <= One of the 3 candidates (the other two are for geo science)
- There are 2 high energy polarimetry missions between Sweden and Japan. PoGOLite, PoGO+: 20-120 kev balloon SPHiNX: 50-500 kev small satellite (plan) - PoGO flights were performed from Sweden in 2013 and 2016. From 2013 flight, only the upper limit of the polarization degree is obtained. Crab: Degree: <42.4% (99% U.L.), Angle: (149.2 ± 16.0) Data analysis of 2016 flight is on-going about Crab and Cyg X-1. - SPHiNX is now in Phase-A/B1 and will be selected in 2017 end. 14
YouTube: PoGO+ Balloon Launch 15