Instructions for Analysing SXT Data Prepared by -- K.P. Singh, PM, SXT Version: 22/9/2016 ** History ** Modified by -- Anjali, IUCAA Edited Step 3 to replace *img files with *cl.evt files. Version : v2 Date: 26/05/2017 ************** Soft X-ray Telescope (SXT) aboard AstroSat is a focusing X-ray telescope that produces images of the sky on a cooled CCD in the focal plane of the telescope. SXT covers a region of the sky of 40 arcmin diameter size (foV) . The data readout from the CCD mostly in the PC mode (99% of the time) provide energy of each photon and a readout time of 2.37s per image frame thus giving it the spectral capabilty and timing ability. The nominal energy bandwidth of the SXT is 0.2 – 7.5 keV and a nominal resolution of 2.5% at 6 keV (for more details on the SXT – please see the Handbook). The segregated SXT data are received at the SXT POC from the ISSDC for each single orbit of the AstroSat. In some cases there may be merged data also directly available. These data (level 1) are run through the SXTPIPELINE at the SXT POC and data are screened for the RAM angle, contamination by the charged particles from excursions through the SAA, the effects of bright Earth, and all events with grades > 12 are also removed, thus producing the level2 data for each orbit. The observer is provided with these level2 data only, alongwith quick look products like image, spectra and light curve for the entire foV are included here. The following steps are required to be carried out by the observer for reducing the data from the target of interest in the field of view. The example used here is the data from the target Tycho supernova remnant observed as part of the PV phase of the SXT (These data are proprietry of the SXT team and being put here solely for the purpose of explaining the steps required. Any use of these data for scientific purposes must be cleared thru the SXT project manager). Step 1: Put all the files for a given ObsID in one directory. Usually fname.tar.gz. For example, in the case of observations of Tycho these files are: 20151105_P01_014T01_9000000080_level2_00570_V1.0.tar.gz 20151105_P01_014T01_9000000080_level2_00571_V1.0.tar.gz 20151105_P01_014T01_9000000080_level2_00572_V1.0.tar.gz 20151105_P01_014T01_9000000080_level2_00573_V1.0.tar.gz 20151105_P01_014T01_9000000080_level2_00574_V1.0.tar.gz These files were created from orbits 570 to 574 of the AstroSat. Step 2: Unzip and untar all the files in the above directory. tar -xvzf 20151105_P01_014T01_9000000080_level2_00570_V1.0.tar.gz tar -xvzf 20151105_P01_014T01_9000000080_level2_00571_V1.0.tar.gz tar -xvzf 20151105_P01_014T01_9000000080_level2_00572_V1.0.tar.gz tar -xvzf 20151105_P01_014T01_9000000080_level2_00573_V1.0.tar.gz tar -xvzf 20151105_P01_014T01_9000000080_level2_00574_V1.0.tar.gz Step 3: Create a file (in text format with the name event_list) containing the location of the cleaned event files, in this case the following lines: ..home/Tycho/20151105_P01_014T01_9000000080_level2_00570_V1.0/sxt/00570/sxt.01/AS1P01_014T01_9000000080sxtPC00_level2_cl.evt ..home/Tycho/20151105_P01_014T01_9000000080_level2_00571_V1.0/sxt/00571/sxt.01/AS1P01_014T01_9000000080sxtPC00_level2_cl.evt ..home/Tycho/20151105_P01_014T01_9000000080_level2_00572_V1.0/sxt/00572/sxt.01/AS1P01_014T01_9000000080sxtPC00_level2_cl.evt ..home/Tycho/20151105_P01_014T01_9000000080_level2_00573_V1.0/sxt/00573/sxt.01/AS1P01_014T01_9000000080sxtPC00_level2_cl.evt ..home/Tycho/20151105_P01_014T01_9000000080_level2_00574_V1.0/sxt/00574/sxt.01/AS1P01_014T01_9000000080sxtPC00_level2_cl.evt The full path is required for each file. This can be done using the “ls” command in unix. Step 4: Run a python script to merge data from the above level2 products obtained for single orbits as follows: python sxt_gti_corr_evt_merger_v05.py --keep_log=yes --filelist=event_list –sname=Tycho The pythin script developed by S. Chandra of the SXT Team carefully looks at the good time intervals (GTI's) in each orbit data, removes time overlaps between data from consecutive orbits and creates a merged event file of all the clean events and keeps a log of the overlaps removed and thus a continuous data of the observation and its correct exposure time. The merged data file thus prodcued can now be used with the XSELECT tool in the HEASOFT package that must be pre-installed in your machine (2015 version onwards). The script is being provided here and the observer must have python installed on the computer being used. Put the script “sxt_gti_corr_evt_merger_v02.py” in your home directory before running. The script will output the following files: Tycho_dt_orbit_information.log Tycho_or00570_00574_merged_cl.evt Tycho_or00570_00574_merged.lbt Tycho_or00570_00574_merged.mkf Tycho_TimeOverlapVerificationLog.txt The observer should look at the *Log.txt file to see what the script has done. For all subsequent analysis the observer/user will need only the *_merged_cl.evt file. This file can be read by the XSELECT programme after following the next step, and can be used to create images, x-ray spectra and x-ray light curve from any region of the image and for any energy range within the SXT bandwidth. Step 5: If you are using HEASoft version older than 6.19, add the following lines (cut and paste between – avoid ***** and do not use “Tab” key for space anywhere) to the xselect.mdb (mission database for the AstroSat SXT). HEASoft version 6.19 already incorporates this. ************************ ASTROSAT:submkey NONE ASTROSAT:instkey INSTRUME ASTROSAT:dmodekey DATAMODE ASTROSAT:mkf_def_expr NONE ASTROSAT:mkf_rel_dir . ASTROSAT:time TIME ASTROSAT:tunits s ASTROSAT:binsize 5. ASTROSAT:x X ASTROSAT:y Y ASTROSAT:xsiz TLMAX ASTROSAT:ysiz TLMAX ASTROSAT:detx DETX ASTROSAT:dety DETY ASTROSAT:detxsiz TLMAX ASTROSAT:detysiz TLMAX ASTROSAT:rawx RAWX ASTROSAT:rawy RAWY ASTROSAT:rawxsiz TLMAX ASTROSAT:rawysiz TLMAX ASTROSAT:phamax TLMAX ASTROSAT:gti GTI ASTROSAT:events EVENTS ASTROSAT:timeorder yes ASTROSAT:instruments SXT ASTROSAT:fbin 1 ASTROSAT:hbin 1 ASTROSAT:spbn 1 ASTROSAT:ecol PI ASTROSAT:ccol NONE ASTROSAT:gcol GRADE ASTROSAT:imagecoord SKY ASTROSAT:wmapcoord SKY ASTROSAT:catnum 1 ASTROSAT:grpstr NONE ASTROSAT:lststr AS1*.* ASTROSAT:ofilt NONE ASTROSAT:wtmapb yes ASTROSAT:wtmapfix yes ASTROSAT:catcol TELESCOP INSTRUME DATAMODE DATE-OBS OBJECT ORB_NUM ASTROSAT:dispcol TELESCOP INSTRUME DATAMODE DATE-OBS OBJECT ORB_NUM ASTROSAT:extract extractor ASTROSAT:respscript NONE ASTROSAT:extendresp no ASTROSAT:respneedreg no ASTROSAT:SXT:modes PC ASTROSAT:SXT:lststr AS1*sxtPC*.* ASTROSAT:SXT:adjustgti yes ASTROSAT:SXT:modes PW ASTROSAT:SXT:lststr AS1*sxtPW*.* ASTROSAT:SXT:adjustgti yes ASTROSAT:SXT:modes FW ASTROSAT:SXT:lststr AS1*sxtFW*.* ASTROSAT:SXT:adjustgti yes ASTROSAT:SXT:modes BM ASTROSAT:SXT:lststr AS1*sxtBM*.* ASTROSAT:SXT:adjustgti yes ASTROSAT:SXT:modes CM ASTROSAT:SXT:lststr AS1*sxtCM*.* ASTROSAT:SXT:adjustgti yes ASTROSAT:SXT:PC:imagecoord SKY ASTROSAT:SXT:PC:wmapcoord SKY ASTROSAT:SXT:PC:binsize 5. ASTROSAT:SXT:PW:imagecoord SKY ASTROSAT:SXT:PW:wmapcoord SKY ASTROSAT:SXT:PW:binsize 5. ASTROSAT:SXT:CM:imagecoord SKY ASTROSAT:SXT:CM:wmapcoord SKY ASTROSAT:SXT:CM:binsize 5. ASTROSAT:SXT:FW:imagecoord SKY ASTROSAT:SXT:FW:wmapcoord SKY ASTROSAT:SXT:FW:binsize 5. ASTROSAT:SXT:BM:imagecoord SKY ASTROSAT:SXT:BM:wmapcoord SKY ASTROSAT:SXT:BM:binsize 25 ********************************************** The XSELECT is now ready to read and process the *merged_cl.evt file created above and recognise that the data from the AstroSat SXT. From here onwards the observer/user can proceed further to create images (can be displayed with ds9), spectra (compatible with XSPEC) and lightcurves (compatible with various HEASOFT tools or ftools for timing analysis), in the same way that these are used for ASCA, Suzaku and Swift XRT data. -----------------The End-------------------