National Aeronautics and Space Administration

efsearch

In this example, we search for the period of a light curve from EXOSAT ME of the transient pulsar, EXO 2030+375.

Executing the efsearch task (Screen output is in a fixed width font, while commentary is italicized):

 
efsearch 1.1 (xronos5.18)
 
Ser. 1 filename +options (or @file of filenames +options)[file1] me_a52385.lc.Z
 Series 1 file   1:me_a52385.lc.Z

We enter the light curve, me_a52385.lc.Z directly as the time series to be considered.

 
 Selected FITS extensions: 1 - RATE TABLE;
 
 Source ............ EXO2030+375         Start Time (d) ....  6208 05:05:35.725
 FITS Extension ....  1 - `RATE      `   Stop Time (d) .....  6208 06:41:19.250
 No. of Rows .......         5737        Bin Time (s) ......    1.000
 Right Ascension ... 307.588622760       Internal time sys.. Converted to TJD
 Declination ....... 37.382217390        Experiment ........ EXOSAT   ME
 
 Corrections applied: Vignetting - Yes; Deadtime - Yes; Bkgd - Yes; Clock - No
             values: .983574270       .756429610       1.00000000
 
 Selected Columns:  1- Y-axis;  2- Y-error;
 
 File contains binned data.
 
Name of the window file ('-' for default window)[-] 

Entering a - indicates that the default exposure windows are to be applied ($XRDEFAULTS/default_win.wi). A custom windows file may be generated with the xronwin task.

 
 Expected Start ...  6208.21221903629  (days)       5: 5:35:725  (h:m:s:ms)
 Expected Stop ....  6208.27869502456  (days)       6:41:19:250  (h:m:s:ms)
 
 Default Epoch is:  6208.000000
Type INDEF to accept the default value
 Epoch format is days.
Epoch[34 234.23] 6208

In this example we choose 6208.0 as the Epoch. Entering INDEF would have the same result.

 Period format is seconds.
Period[88.87] 40

Enter a guess for the period (default units are seconds) of the light curve. The period value will be used as the center of the range of trial values.

 Expected Cycles ..            143.59
 Default phase bins per period are:         8
 Type INDEF to accept the default value
Phasebins/Period {value or neg. power of 2}[-3] 

The phasebins/period (nphase) setting represents the resolution of the trial folded light curves (i.e. the number of bins that the range from phase of 0.0 to phase of 1.0 is divided into). If a negative value is given, the phasebins/period is 2 to the power of the absolute value of that number. (e.g. nphase=-3 -> nphase=2^abs(-3)=8). The default (8), corresponding to INDEF may be altered with the hidden parameter nbdf.

 
 Newbin Time ......     5.0000000      (s)
 Maximum Newbin No.              1149
 
 Default Newbins per Interval are:        1149
 (giving       1 Interval of         1149 Newbins)
 Type INDEF to accept the default value
 
Number of Newbins/Interval[10] 1149

Entering INDEF would include exactly the timespan of the input in the resulting plot. Giving a smaller number than the indicated INDEF value would result in multiple intervals. In this example, we enter the default value, 1149, directly so only one interval is calculated.

 Maximum of       1 Intvs. with         1149 Newbins of       5.00000     (s)
 Default resolution is 0.1392515231
 Type INDEF to accept the default value
Resolution for period search {value or neg. power of 2}[.03] 0.1
 Default number of periods is       128
 Type INDEF to accept the default value
Number of periods to search[100] 

The period, resolution of period search, and number of periods to search together define the range of periods to search. In this example, 100 periods are searched around 40 seconds in steps of 0.1 (i.e. 35.0, 35.1, 35.2, ... 44.7, 44.8, 44.9)

Name of output file[default]  

In this example, we enter a space before pressing Return to indicate that an output FITS file is not desired, however, entering default for the output file, will result in a folded FITS light curve file to be written with the extension .fes.

Do you want to plot your results?[yes] 

In general, we want to plot the results of the search, however, entering no will prevent efsearch from plotting the output. This is useful when only the output FITS file is desired.

Enter PGPLOT device[/XW] 

The Xwindows device, /xw is recommended as the results may be viewed immediately and the plot may be manipulated interactively with PLT. In some cases, however, other file-based devices such as /ps and /gif may be desired.

 
     100 analysis results per interval
 
 
 Period :   41.80    dP/dt :  0.0000E+00
 Intv    1   Start  6208  5: 5:37
     Ser.1     Avg  400.0        Chisq 0.1214E+06   Var 0.1171E+05 Newbs.      8
               Min  268.6          Max  554.2    expVar 0.7800      Bins   5713

By default, the following plot is produced. Note that the x axis represents the attempted periods offset by the best period found.

PLT> quit