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)

SPHiNX satellite 0.5m (Plan: 2021~)

PoGO+ balloon 10m (2016)

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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)

SPHiNX satellite 0.5m (Plan: 2021~)

PoGO+ balloon 10m (2016)

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Scattering

Cygnus X-1

Synchrotron emission

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)

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- 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.eduGamma-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.eduGamma-ray (20-120 keV) ~40 km Weight (wo ballast) : ~1750 kg

Power : ~300 W (Instrument) ~200 W (Gondola, etc.)

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Flight Plan (1-day long)

(c) astro.psu.edu

Crab nebula (Pulsar) Cyg X-1 (Black hole binary)(c) ESA

Solar flare(c) JAXA

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

-  PoGO+: 7 days: July 12~18, 2016 from Sweden to Canada

(Unfortunately) the polarimeter worked only 3 days (Crab: 3 times)

Many updates from PoGOLite We performed observations of (Crab: 7 times, Cyg X-1: 6 times)

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〜40 cm

Fast plastic scintillator (12-cm long)

Pb/Sn/Cu collimator

BGO scintillator

1.5 m

- 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.

Top view

Gamma-ray

One direction detects more events

- Instrument is rotated (6 mins/rotation) to cancel instrumental systematics.

Polyethylene shield 8

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Preliminary

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Preliminary

- As same as PoGOLite in 2013,we managed to detect Crab pulsation (33 ms) in 2016 flight datausing only polarization information (2 hits of Compton + photoabsorption).- Polarization analysis is on-going for Crab and Cyg X-1.

1000 events

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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+

Cou

nts

Phase

PoGOLite (20-110 keV) Suzaku/PIN (10-70 keV)

200 events

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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)

Pol

ariz

atio

n an

gle

Polarization degree

SPHiNX (Segmented Polarimeter for High eNergy X-rays)

- GRB dedication (50-500 keV), 25 / year - Large effective area for polarization: 70 cm2

- 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 <= One of the 3 candidates (the other two are for geo science)

Scatter: Plastic + PMT Absorber: GAGG (or BGO) scintillator +APD or SiPM

〜30 cm

Scientific goals: Emission mechanism of gamma-ray burst jets (Synchrotron + photosphere?)

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-  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.

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15 YouTube: PoGO+ Balloon Launch