Quantum efficiencies of the XIS CCDs onboard Suzaku

1. Quantum efficiencies of the XIS CCDs onboard Suzaku T. Miyauchi, K. Hayashida, K. Torii, M. Namiki, N. Anabuki, S. Katsuda, N. Tawa, D. Matsuura, H. Tsunemi, Osaka Univ. (Japan); H. Nakajima, H. Yamaguchi, H. Matsumoto, T. G. Tsuru, Kyoto Univ. (Japan); T. Kohmura, Kougakuin Univ. (Japan); H. Katayama, Japan Aerospace Exploration Agency (Japan); E. Miller, B. LaMarr, S. E. Kissel, M. W. Bautz, Massachusetts Institute of Technology [6266-100]

2. Outline of the Problem Findings • Some of the observed spectra at low energy (<1keV) were not what we expected • According to the knowledge from previous missions. • Inconsistent among the XIS 4 sensors • QE degradation at low energy is explained by introducing extra carbon absorber in the XIS response (~2005Dec). Contamination is most likely cause. • We performed repeated observations of one source (E0102). Evolution of the QE degradation was found. • XIS response in which extra carbon absorber was prepared and distributed to SWG members and GOs, with empirical model of its time evolution. • Analysis of diffuse sources indicated non-uniformity of the carbon absorber within XIS FOV. Contamination on OBF is most likely cause. • Analysis of atmospheric fluorescent line provided further data for time evolution and non-uniformity. • Detailed spectrum analysis of some sources provided information on the composition of the absorber.

3. RXJ1856.5-3754 Discovered with ROSAT Nearby (D~120pc) Isolated Neutron Star X-ray spectrum is fitted with a simple blackbody ( against NS atmosphere model). R~4-5km Quark Star ?

4. RXJ1856 Observed with Suzaku 2005-10/24~26RMF 20051210 a-d for XIS1 Rev0.3 data -10eV offset C-K edge ~0.3keV a: Based on the Cal on the Ground b: a x excess0.15mmC c: Dead Layer =Design Value d: c x excess0.15mmC

5. Suzaku/XIS ContaminationMeasurements with E0102 • E0102: SNR in SMC, bright in soft X-ray lines • excellent calibrator for low-E gain, QE changes • contamination degrading low-E eff. area of all XIS’s • model • thermal bremss + 24 Gaussian emission lines • Galactic + SMC absorption • pure C absorption from contaminant (varabs) • gain shift -5 eV ~ -15 ev • r2 ~ 1.6 (FIs) to 2.5 (BI) NeIX OVIII NeX MgXI OVII 2005-08-13 2005-08-31 2005-12-16 2006-01-17 2006-02-02

6. XIS Contamination Rate • empirical correction for observers • contamination rate turnover (?) • SMC NH uncertainty  systematic error ±0.02 m independent of epoch change in effective C column: chip slope intercept (1016 cm-2/day) XIS0 1.6 ±0.1 4.4 ±4.0 XIS1 2.7 ±0.1 -9.6 ±15 XIS2 3.1 ±0.1 -3.2 ±14 XIS3 4.1 ±0.5 54. ±50.

7. Cyg Loop • Nearby Old Super Nova Remnant • 2005Nov 4pointgs C-band CVI-band

8. C-band/CVI-band map in detector coordinate =Inidicating absorber thickness is not uniform

9. Center Rim C Absorber thickness is about 1/2 at Rim (2005 Nov)

10. Atmospheric Fluorescence Line • When the telescope is looking at the shining Earth or its atmosphere, fluorescence lines of the Earth atmosphere (N-K, O-K) by Solar X-rays are contaminated in the observed spectra. • Intensity and line ratio depends on the elevation angle from the Earth rim and the Solar activity. N-K (0.39keV) O-K (0.52keV) DAY EARTH 0 < DYE_ELV < 5 5 < DYE_ELV < 10 10 < DYE_ELV < 20 20 < DYE_ELV < 30

11. N-K line 2005-8-13 2005-9-4 2005-10-22 2005-11-28 2005-12-24 2006-2-6 Day Earth 0 < DYE_ELV < 5 5 < DYE_ELV < 10 10 < DYE_ELV < 15 15 < DYE_ELV < 20 20 < DYE_ELV < 25 From Anabuki et al.’s poster Atmospheric N-K line Map XIS1(BI) Color code is adjusted for each map

12. 2005-8-13 2005-9-4 2005-10-22 2005-11-28 2005-12-24 2006-2-6 Day Earth 0 < DYE_ELV < 5 5 < DYE_ELV < 10 10 < DYE_ELV < 15 15 < DYE_ELV < 20 20 < DYE_ELV < 25 Atmospheric O-K line Map XIS1(BI)

13. E0102-72 SN1006_NE_BGD Mrk 3 A2811_offset NGC 4388 MBM12_off Cloud N-K line O-K line N-K line O-K line N-K line O-K line N-K line O-K line N-K line O-K line N-K line O-K line Day Earth Radial Profile(vignetting corrected,normalized by center region)

14. N-K line O-K line Center 6mm radius / Other area • Mean Free Path in C(2.2g/cc) • 0.182mm for N-K line • 0.375mm for O-K line • Spatial Difference in Carbon contamination thickness can be modeled with Atmospheric N-K, O-K data. • Thickness at the center is evaluated by E0102 and RXJ1856 obs. • Thickness (t,detx,dety) will be modeled/introduced in arfbuilder (or rmfbuilder).

15. PKS2155-304 NH(Gal)=1.65e20cm~-2 XIS1(BI) NH(Gal)*Pow NH(Gal)*N_C*Pow NH(Gal)*N_C*N_O*Pow XIS3(FI) NH(Gal)*Pow NH(Gal)*N_C*Pow NH(Gal)*N_C*N_O*Pow

16. N_C vs N_O Cf DEHP(C24H38O4) N_O/N_C=1/6=0.17

17. If we assume the contaminant is DEHP… XIS1 XIS3 Assuming DEHP NH(Gal)*DEHP*Pow NH(Gal)*DEHP*Pow XIS1 XIS3 Best fit C/O ratio NH(Gal)*N_C*N_O*Pow NH(Gal)*N_C*N_O*Pow The data may not reject the possibility of DEHP.

18. Contamination 2D model • E0102 +RXJ1856 Obs →Contaminant thickness at Center • Atmospheric N-K/O-K → Difference in Contaminant thickness as a function of radius E(t) is the thickness of the carbon at the center

21. Recent Obs. of RXJ1856 &E0102

22. If we assume the contaminant has significant contribution from Oxygen C:O=6:1

23. Summary • QE degradation in Suzaku XIS has been studied. • Absorber (Contaminat) thickness: XIS0<XIS1<XIS2<XIS3 • Absorber thickness: Rim ~ 1/2 of the Center. Atmospheric N-K, O-K line is efficient to evaluate the distribution of the absorber. • Contamination Rate was almost constant in 2005, but the rate is decreasing recently. • Carbon is dominant in the contaminant . There is a small contribution of O. PKS2155 results gives O/C <0.13. • Empirical model of the QE degradation as a function of time and location has been made. • Recent RXJ1856 & E0102 observations indicate O contribution might be significant. Assuming O/C =1/6 gives smooth connection in time plot.