1. The PHENEX Experiment Results in 2006 and Future Plan S. Gunji* a, Y. Kishimoto a,H. Sakurai a, F. Tokanai a, M. Kanno a, Y. Ishikawa a, Hayashida b, N. Anabuki b, H. Tsunemi b, T. Mihara c, M. Kohama c, M. Suzuki c, Y. Saito d, T. Yamagami d a Yamagata University, 1-4-12 Kojirakawa Yamagata-city, 990-8560 Japan b Osaka University, 1-1 Yamadaoka Suita-city Osaka Japan c RIKEN, 2-1 Hirosawa Wako-city 351-0198 Japan d JAXA, 3-1-1 Yoshinodai Sagamihara-city 229-8510 Japan S. Gunji* a, Y. Kishimoto a,H. Sakurai a, F. Tokanai a, M. Kanno a, Y. Ishikawa a, Hayashida b, N. Anabuki b, H. Tsunemi b, T. Mihara c, M. Kohama c, M. Suzuki c, Y. Saito d, T. Yamagami d a Yamagata University, 1-4-12 Kojirakawa Yamagata-city, 990-8560 Japan b Osaka University, 1-1 Yamadaoka Suita-city Osaka Japan c RIKEN, 2-1 Hirosawa Wako-city 351-0198 Japan d JAXA, 3-1-1 Yoshinodai Sagamihara-city 229-8510 Japan Polarimetry for High ENErgy X rays

2. Table of Contents I omit the Introduction. Probably it is not necessary. The Performance of PHENEX Polarimeter The abstract for the balloon-borne experiments in 2006 The results of the polarization observation for the Crab Nebula Future plan for PHENEX and the other Japanese polarimeters I omit the Introduction. Probably it is not necessary. The Performance of PHENEX Polarimeter The abstract for the balloon-borne experiments in 2006 The results of the polarization observation for the Crab Nebula Future plan for PHENEX and the other Japanese polarimeters

3. 2. Unit Counter Side ViewTop View The PHENEX polarimeter consists of several unit counters which are Compton scattering type polarimeters. Detecting the scattering and absorbing positions, the two dimensional scattering angle is determined and the information on the polarization is acquired. The azimuthal scattering angle depends on the direction of the polarization for incident hard X rays. The opening angle is 4.8°(FWHM) and CsI(Tl) scintillators are surrounded by passive shields (Sn and Pb).

4. Performance of the unit counter Energy range40 keV ~ 200 keV Geometrical area of one unit counter ~11cm 2 Modulation factor53% (at 80 keV) Detection efficiency20% (at 80keV) Experimental setupModulation curve Irradiating the unit counter with polarized beam, we measured the modulation factor and the detection efficiency, respectively. Side view Front view

5. 3. Prototype Flight Model Four unit counters and one monitor counter are installed and they are surrounded by active shields made of CsI(Tl). The monitor counter has the same collimator as unit counters and the line of the sight is co-aligned to that of unit counters. It is only used to monitor the flux from the Crab Nebula. The whole detector is installed in the pressure vessel. The pressure vessel rotates around the line of sight. It is useful to reduce spurious modulation. The mounted sun sensor is used to control the attitude and to monitor the line of the sight.

6. 4. Balloon Flight At 5:13(JST) in Jun13 2006, the prototype PHENEX polarimeter was launched. It achieves level flight of 38km for about 6 hours. 38km ~6 hours height time launch Level flight The PHENEX polarimeter operates well on level flight and is recovered safely on the sea after the cutting. However, the attitude control system did not function correctly. As the sun sensor operates well, we can identify the line of the sight. Even so we achieve the observation of the Crab Nebula for about one hour and the background for about one hour.

7. 5. Counting rates The counting rates for the monitor counter well correlate with the acceptance by the collimator. Monitor counterFour unit counters The counting rates for the unit counters well correlate with the acceptance by the collimator. The increase of 0.2Hz on the observation of the Crab Nebula is shown in this figure. The PHENEX detected the flux from the Crab Nebula with 8σ. 0.2Hz OFF source ON source

8. 6.1 modulation curve for off-source observation North East South West Scattering angle The data were fitted with the following equation. Counts = A+B×sin(2θ+C) (A,B, and C are free parameters) The degree of modulation (B/A) was 0.018. Considering the modulation factor (53%) of the PHENEX polarimeter, the degree of the polarization for the blank sky is only 3.3%. It indicates that the PHENEX polarimeter does not make much spurious modulation. Equatorial coordinates 6. Data analysis for polarization

9. 6.2 for on-source observation 6.3 for the Crab Nebula Counts = A+B×sin(2θ+C) A=348, B=9.7, C=312 The degree of modulation was 0.028 (=9.7/348). Counts = A+B×sin(2θ+C) A=65.9, B=14.4, C=323 The reduced   for the degrees of freedom 9 was 0.65.

10. Considering the effects that the line of the sight wandered, the degree and the direction of the polarization were calculated to be 33±26% and 154 ±43 degrees, respectively. Though we can not discuss the polarization in detail due to the large error, it is not inconsistent with the previous results for soft X rays (degree:20%, direction:155degrees). Moreover, we do not also exclude the results of INTEGRAL. Results in 2006 Y.Kishimoto etal IEEE Trans. on Nucl. Sci. 54, Issue 3, pp561 – 566(2007) S. Gunji etal. Proc. of SPIE. Vol.6686 pp18-1 〜 9 (2007) M. Kanno etal. IEEE Nuclear Symposium Proceedings (2007)

11. 18’’ N S E W Soft X-ray map energy 偏光方向 Observation region optical162°Within 30’’ (without pulsar) optical123°Within 2’’ (without pulsar) 5.2keV152.6±4.0°Total region (without pulsar) 50 〜 1 ６ 0keV 154±43°Total region (with pulsar) 0.1 〜 1MeV 123±11°Total region? (without pulsar) Rotation axis of the pulsar is 124±0.1° By Dr. Weisskopf Standard scenario: For more inner region, the direction of the polarization is more co-aligned to the axis of the pulsar. Hard X-ray map By Dr. Makishima Conflict ?

12. 7. Future Plan of PHENEX In Spring 2009, increasing the number of unit counters and reinforcing the shields, we plan to observe the Crab Nebula again and will measure the polarization at accuracy. Computer simulations ON source observation ON - OFF Assumption: the degree is more than 30%. 6 hours obsrevation. The degree and direction of the polarization can be determined to ±7% and ±14 degrees, respectively.

13. 8.Other Japanese Projects GAP(GRB polarimeter) launched in ２０１０. POLARIS to be designed for small satellite Preflight Model It is very small (3.4kg) The polarization for 2 〜 3 GRB ｓ will be measured at accuracy per year. We proceed basic studies with the help of Italian.

14. 9. Conclusions To open the new window for hard X-ray astronomy, we developed the PHENEX polarimeter. It obtains the detection efficiency of 20% and the modulation factor of 53% at 80keV, respectively. Constructing the prototype flight model, we carried out balloon borne experiment in Jun.13 2006. Though the PHENEX polarimeter operated well, the attitude control system did not function correctly. Even so we succeeded in observing the Crab Nebula for about 1 hour and the blank sky for about 1 hour. We detected the flux from the Crab Nebula with 8σ by 4 unit counters. From the analysis, the degree and the direction of the polarization for the Crab Nebula were determined to be 33±26% and 154±43 degrees. Unfortunately, for the shortage of the observation time and the small detection area, the precise value can not be determined. We plan to carry out balloon-borne experiment with improved PHENEX polarimeter next year. It will determine the degree and the direction at accuracy. Moreover, we will launch the GAP in 2010 and are developing the POLARIS to observe a hundred stellar objects. To open the new window for hard X-ray astronomy, we developed the PHENEX polarimeter. It obtains the detection efficiency of 20% and the modulation factor of 53% at 80keV, respectively. Constructing the prototype flight model, we carried out balloon borne experiment in Jun.13 2006. Though the PHENEX polarimeter operated well, the attitude control system did not function correctly. Even so we succeeded in observing the Crab Nebula for about 1 hour and the blank sky for about 1 hour. We detected the flux from the Crab Nebula with 8σ by 4 unit counters. From the analysis, the degree and the direction of the polarization for the Crab Nebula were determined to be 33±26% and 154±43 degrees. Unfortunately, for the shortage of the observation time and the small detection area, the precise value can not be determined. We plan to carry out balloon-borne experiment with improved PHENEX polarimeter next year. It will determine the degree and the direction at accuracy. Moreover, we will launch the GAP in 2010 and are developing the POLARIS to observe a hundred stellar objects.

15. Rome was not built in a day neither PHENEX…. I hope the PHENEX measures the polarization at accuracy next year because the observation in hard X-ray region is the key. Grazie mille per suo attenzione My Italian makes sense?