Question ID = 0033
Question ID = 0033
Assigned Member (担当者)2006-11-23 A.KubotaName and Institute (質問者/機関)Dr. Jukka Nevalainen (Helsinki Univerity Observatory)Question (質問)Is there an published estimate for the stability of the particle-induced XIS background? If not, is it safe to assume that (at least front illuminated) XIS detector background reproducibility will be similar as in the case of ASCA (Kushino et al, 2002, PASJ, 54, 327) i.e. 3% at the 1-10 keV band at 1 sigma confidence level?Answer from(回答の文責)XIS teamAnswer (答え)The background study will be presented at Suzaku conference in coming December by Tawa & Nagai et al. Since study of background stability generally takes long time to accumulate enough data, published estimate on it has not been available yet. And the direct application of the ASCA/SIS estimation to the XIS is not so reliable. Currently, to estimate NXB of the XIS, the night earth data are prepared on the following web page.http://www.astro.isas.jaxa.jp/suzaku/analysis/xis/nte/ In this web page, the NXB background model is also prepared by perl script considering only COR condition. Accuracy of the model is currently 5-10% (depending on an exposure) in the energy band of 5-12keV for the FI-CCDs. Take this value as preliminary one. Details will be reported in the conference paper and in a calibration report in the near future. Followup Question (再質問)The accuracy of the NXB modeling has a range of 5-10%, due to different exposure time, you say. What is the range of the exposure times corresponding to the above 5-10% accuracy range? What are the accuracy values in the 1-7 keV band? The numbers seem quite high. In case of XMM-Newton PN, the closed-cover observations (= quiescent NXB) showed that the average NXB spectrum, scaled with the > 10 keV band count rate of individual observations ' (= NXB model) predicts the NXB in the 1-7 keV band with 5% accuracy at 90% confidence level (Nevalainen et al, 2005, ApJ 629, 172, Fig.1).Answer (答え)It is difficult to answer your questions right now. As the XIS team wrote, "Details will be reported in the conference paper and in a calibration report in the near future". please wait those reports. The values of 5-10% are 1 sigma for 5ks or 50ks exposures on the dark Earth observations. Please note that, for example, one 5ks exposure of the dark Earth observation consists of many chunks of short exposures, spannig for several hours to a few days. To evaluate the NXB model accuracy, the NXB level itself ( in terms of the S/N ratio to diffuse emissions as is defined in Katayama et al., 2004, A&A, 414, p.767) is 2-3tims higher for the XMM PN than Suzaku (or ASCA). So the direct comparison between the XMM and Suzaku (or ASCA) is not so easy.Status （詳細なステータス）2006-11-23 Accepted2006-11-23 Asking to XIS team 2006-11-24 Reply to the question 2006-11-24 Followup question 2006-11-24 Asking again to XIS team 2006-11-24 Done 
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