Suzaku Help Jp: Question #0030

Question ID = 0030

Assigned Member (担当者)

There's no problem on the pipe-line processing. The value of ONTIME is the same value of "TSTART - TSTOP", and the value TELAPSE is the same as the summation of 50 time-intervals in GTI extension. It is OK.
The reason the efficiency of TELAPSE par ONTIME is low (31%) is the condition of your observation, we checked. The spacecraft has about 90-minutes orbital-period, and sometimes the satellite observes the earth (i.e., not the source). In addition, the quality of the observation becomes bad during the spacecraft passes the SAA, or during the time interval that COR is less than 8 GV for the HXD.
You can check how the exposure is reduced by accepting cleaning criteria, one by one, from unscreened events list, by using the following commands on xselct;
> read event .
ae501109010hxd_1_wel_uf.evt ae501109010hxd_2_wel_uf.evt
> read hk .
ae501109010.ehk.gz
yes
> select hk
ELV>5
> extract event
> save event
The results are as follows. Thus, about 60 ksec observation of the earth and 15 ksec bad-COR intervals are included in your 150 ksec observation.

Step-0. Unscreened event
148956. seconds
Step-1. Exclude Earth observation (ELV>5 && DYE_ELV>20)
84360. seconds
Step-2. Exclude bad COR interval (++ && COR>8)
59701. seconds
Step-3. Exclude SAA passage (++ && SAA_HXD.eq.0 && T_SAA_HXD>436)
43932. seconds

Please note that the earth event is very useful if you want to check systematic errors of the NXB model of the HXD.