boxfitting

NAME

boxfitting -- either search for box-shaped transit signatures within a lightvurve or fold a lightcurve


USAGE

boxfitting [flags] lightcurve(s)

SDE_min s 6.0
clipping c 0
error_clipping e 0
file_column 0
folding f false
lightcurve l lightcurve_
logfile logfile
mag false
nchi_column 0
number n 10
output o SR_
p_end 50.0
p_start 1.1
period 2.5
precision p 1001
q_end 0.1
q_start 0.01
t0 0.0
use_nchi false


PARAMETERS

SDE_min = 6.0
Minimum Signal Detection Efficiency. A good value to start is maybe 5.5 or 6.0, but clear detections should show a SDE higher than 10.
clipping = 0.0 (not functioning yet!!!)
After average and sigma of the whole dataset are estimated all datapoints {i} with values flux(i) - average >= clipping * sigma or flux(i) - average <= clipping * sigma are dropped. For clipping the lightcurve must contain at least 30 datapoints.
error_clipping = 0.0 (not functioning yet!!!)
After average and sigma of the whole dataset's errorbars are estimated all datapoints {i} with errorbars error(i) - average >= error_clipping * sigma or
error(i) - average <= error_clipping * sigma are dropped. For error_clipping the lightcurve must contain at least 30 datapoints.
file_column = 0
Column number of filename informations. If used the folded output lightcurves will also contain these informations.This is done to connect each datapoint to the filename of the image in which the flux measurement has been made. If specified also the output lightcurve will have a colum with the filename information. Also it is calculated in how many different nights the exposures corresponding to the datapoints within the transit phase were made.
folding = false
If true, the lightcurve specified by the lightcurve(s) ist folded to the period and epoch specified by the period- and t0-flags. The folded lightcurve is written to the file specified by the lightcurve-flag.
lightcurve = lightcurve_
Output lightcurve prefix. Each detection will result in one folded lightcurve. The prefix will be followed by a number expressed in 5 digits (starting with "00001") and the suffix ".tbl". If a single lightcurve is folded (folding-flag) the name specified by lightcurve is the total output filename.
logfile = logfile
Logfile containing all parameters of the detections. The logfile is not created in the folding mode (folding-flag).
mag = false
If true, the output lightcurve(s) are written in Magnitude units. The flux of the input lightcurve(s) must be expressed in Jansky [Jy].
nchi_column = 0
Column number containing the normalized chi2 of the fit in the final PSF-measuring step. If used the folded output lightcurves will also contain these informations. If in addition the use_nchi-flag is used the individual errors of all measurements are scaled with the values in the given column.
number = 10
Maximum number of detections per input lightcurve.
output = SR_
Output frequency spectrum prefix. Each detection will result in one spectrum. The prefix will be followed by a number expressed in 5 digits (starting with "00001") and the suffix ".tbl". The first column of the output file is giving in (period)-1.
p_end = 50.0
Maximum period tested.
p_start = 1.1
Minimum period tested.
period = 2.5
If a lightcurve is simply folded with the task boxfitting (folding-flag) this period is used.
precision = 1001
Number of periods tested. The periods are equaly distributed in the (period)-1-space enclosed by (p_end)-1 and (p_start)-1. The precision must be higher than 20.
q_end = 0.1
Maximum fractional transit length tested. The fractional transit length is the length of the transit in units of phase.
q_start = 0.01
Minimum fractional transit length tested. The fractional transit length is the length of the transit in units of phase.
t0 = 0.0
If a lightcurve is simply folded with the task boxfitting (folding-flag) this epoch is used. The specified value is set to phase equal to 0.5. If t0 is equal to 0.0 the first time value in the input lightcurve is set to phase equal to 0.0.
use_nchi = false
If true, the individual errors of all measurements are scaled with the values in the column specified by the nchi_column-flag.
lightcurve(s)
Input lightcurve(s) to be inspected or folded. The File(s) must contain three colums: the first must specify the time in days, the second the flux in arbitrary units and the third column has to contain the errors of the flux-measurements in the same units.

DESCRIPTION

The task can be used in two different ways:

1) Searching for box-shaped transt signatures in one ore more lightcurves:

Based on a method suggested by Kovacs et al. (2002) the program is doing a simple least square analysis by fitting step functions to several trial periods specified by the p_start-, p_end- and precision-flags. For each period the best fitting box with a minimum and maximum size specified by the q_start- and q_end-flags is determined. A value "SR" is a measure for the quality of the best fit for each period (high "SR" means low least squares). Plotting all "SR"-values over 1 / period results in the "SR" frequency spectrum in which the possible detections can be seen as sharp peaks. The spectrum is normalized to the highest peak. In order to estimate the quality of a detection the signal detection efficiency "SDE" of the 10 highest peaks is calculated by dividing the difference between peak hight and average "SR" by the standard deviation of the whole "SR" frequency spectrum. For each input lightcurve a given maximum number of detections (number-flag) with a higher "SDE" than specified by the SDE_min-flag is written to a logfile (logfile-flag). Also for each detection the folded lightcurve and the "SR" frequency spectrum is written to files specified by the lightcurve- and output-flag.

2) Fold a lightcurve to a given period and epoch:

The input lightcurve is folded to the period and epoch specified by the period- and t0-fags and written to a file specified by the lightcurve-flag.

OUTPUT

1) Search for box-shaped transit signatures in one ore more lightcurves:

- logfile :
# SDE p q transits nchi filename lightcurve
#
5.6766 3.706 0.075145 5 / 11 0.75738 ../../F9/F9_00121.tbl lightcurve_00001.tbl
5.5523 2.5534 0.011874 5 / 6 1.518 ../../F9/F9_00171.tbl lightcurve_00002.tbl
6.5472 1.4674 0.078242 12 / 21 1.835 ../../F9/F9_00181.tbl lightcurve_00003.tbl
5.7278 5.8735 0.0189 6 / 9 1.8271 ../../F9/F9_00181.tbl lightcurve_00004.tbl
...
The first three columns give for each detection the Signal-Detection-Efficiency (SDE), the period p and the fractional transit length q. The fourth column is giving two numbers: first, the number of different nights from which the datapoints within transit-phase originate (only if the information is provided using the file_column-flag, if not, this value is "0") and second, the total number of datapoints within transit-phase. The fifth column is giving the normalized chi^2 of the box-fit whereas the last two columns show the filenames of the input and the folded output lightcurve.

- folded lightcurve(s) :

For each detection listed in the logfile a folded output lightcurve is written. The first column of these files is giving the phase, the second column the flux and the third column the error of each of the datapoints. If the mag-flag is used the fluxes are transformed into magnitudes assuming the fluxes in the input lightcurve is given in Jansky [Jy]. The fourth column gives the normalized If the The name(s) of the folded output lightcurve(s) consist of a prefix specified by the lightcurve-flag followed by a number expressed in 5 digits (starting with "00001") and the suffix ".tbl".

- frequency spectrum/spectra :
For each detection listed in the logfile an output frequency spectrum written. For each tested period the first column of these files is giving (period)-1, the second column a value named "SR" which is a measure of the quality of the fit. Detections show up as peaks in the SR-spectrum. The name(s) of the folded output lightcurve(s) consist of a prefix specified by the output-flag followed by a number expressed in 5 digits (starting with "00001") and the suffix ".tbl".


2) Fold a lightcurve:

- folded lightcurve:

The folded output lightcurve will be written to the file specified by the lightcurve-flag. The first column of this file is giving the phase, the second column the flux and the third column the error of each datapoint.


EXAMPLES

1) Search for eclipsing binaries with periods from 0.3 to 10 days and fractional transit lengths between 10% and 40% in the lightcurves light_*.tbl:

boxfitting -s 5.5 -n 3 --p_start 0.3 --p_end 10 -p 1001 --q_start 0.1 --q_end 0.4 light_*.tbl
2) Fold a single lightcurve to a period of 2.33 days and a t0 (in Julian Days) of 2453418.4:

boxfitting -l lightcurve_folded.tbl --period 2.33 --t0 2453418.4 lightcurve.tbl


Task index
This task was implemented by J. Koppenhöfer
Dokumentation maintained by J. Koppenhöfer
This file was last time updated on 21 Feb 2005