slotview

Name

slotview – Analysis and display of slotmode data

Usage

slotview images indata fileout srcfile (fps) (phottype) (sigdet) (contpix) (vignfile) (clobber) (logfile) (verbose)

Parameters

newfits

String. Output fits file from slotphot. This file should be a multi-extension fits file containing only images where the target and comparison star appear.

indata

String. Name of the output light curve file from slotphot. The output file is a 12-column ascii table. There is one row in the table for each exposed frame of the image sequence.

fileout

String. Name of the output file. The output file is a 12-column ascii table. There is one row in the table for each exposed frame of the image sequence. This will only be produced if new photometry is performed.

srcfile

String. Name of the file defining the raw CCD pixel position of two sources in the image data and defining the size of circular aperture for the extraction of source counts and and a circular annulus for the extraction of background counts. The file format is an ascii table with 7 columns and 2 rows. An example is provided below:

# star amplifier   x   y  r r_bkg1 r_bkg2
# ---------------------------------------
1         3 193  11 12     13     14
2         3  37  12 12     13     14

Rows beginning with the character ‘#’ are ignored. Column 1 contains a numeric flag for the star which is either 1 or 2. The target star should be indicated by the value ‘1’ or ‘t’. This should be the same file used to produce the light curve data using slotphot. See slotphot for additional information about the file.

fps

Real. For playing the image data, this is the number of frames per second that will appear.

phottype = [square|circular|cog|optimal]

String. The type of photometric method used for data analysis. The options are:

“square”

A square aperture with sides of length 2xr in the srcfile is used for both target and companion star

“circular”

A circular aperture with radius of r as indicated in the srcfile is used for both target and companion star

“cog”

Perform curve of growth photometry. Will measure even placed square apertures between 2 pix and the br2 radius as indicated in the srcfile. The number of square apertures is given by the radius in the srcfile. The sky background level is deteremined locally between the br1 and br2 radii. Photometry is returned in the square aperture with the maximum signal to noise for the comparison star. Photometry of the target star uses an aperture of the same size.

“optimal”

Calculate the optimal ratio between the two sources based X^2 pixel fit of the comparison star to the object star. For both stars the background will be removed and then the comparison star will be used as a ‘model’ psf for the X^2 fit. To simplify the error calculation, we are assume the errors on the comparison star are much smaller than the errors on the target star

sigdet

Real. sigdet is the significance a source must have in order to be detected in the image. This is only used in the sub routine that follows the drift of the comparison star. If the comparison star has relatively small drift, this parameter will not be used. However, if the drift becomes large or a major shift occurs in the image, slotphot will detect all nearby objects and select the closest one to the previous location as the companion star.

contpix

Int. The number of continous pixels a source must have in order to be deemed a significant detection. Combined with sigdet, it is used for tracking a companion star with dramatic drift. If only small drift occurs, this parameter is not used. A large value is typically set so that comsic rays are not misidentified as the companion star.

driftlimit

Real. If drifitlimit is set to a positive value, the star will only be looked for in an area set by this radius. If no star is found in this area, the coordinates for the object will remain as in the previous frame. If drift limit is negative, the star will be searched for in the entire frame.

vignfile

String. An ascii table containing approximate limits of the vignetting profile across the SALTICAM SLOT. The table is contained in the salt/salticam/data directory and can be modified if the user wishes. The use of this data is purely cosmetic, providing diagnostic information in the tools plotting window, and helps the user understand potential structure in their light curve This functionality is likely to be removed or adapted for the next version. .He

clobber

Hidden Boolean. If clobber=y the tool is permitted to overwrite an existing file with name outfile.

logfile

String. Name of an ascii file for storing log and error messages from the tool. The file may be new, or messages can also be appended to a pre-existing file.

verbose

Boolean. If verbose=n, log messages will be suppressed.

Description

This tool has been developed primarily to analyze the output from slotphot and determine the quality of the observations and photometric analysis of SALTICAM slot mode data. This task is designed for use with the output from SLOTPHOT and specifically for SALTICAM slotmode observations. SLOTVIEW will plot the light curve, display individual frames with the target data, and allow new photometry to be performed.

Using the data in the indata file that contains the information about the light curve, SLOTVIEW will display the lightcurve. By using the right mouse button, the user can zoom in on the time curve and examine a smaller space along the time axis. The graph will automatically resize the flux ratio axis to the data within the selected time region. The frame can be reset by clicking on the reset button which will redraw the original graph over the whole time interval. By clicking on any given time, the frame associated with that time will be displayed.

In addition to display the light curve, slotview will also display individual frames. In each of these frames, the amplifier containing the target star and the comparison star will be displayed. The target will be indicated by a yellow box and the comparison star will be indicated by a green box. The box size is given by the aperture size used in the srcfile and is the aperture in which photometry is performed. The user can watch the time series by using the action buttons below the image display. The user can run the series in forward or revese at the speed set by the fps parameter (single arrow on the display) or at the maximum speed of the computer system (double arrow). The fps parameter gives the frames per second for the display.

If needed, the user can perform new photometry on the image. To perform new photometry for a single image, simple press ‘p’ and press ‘P’ or ‘shift+p’ to perform photometry on all subsequent images. To reset the comparison star in case the object has drifted or disappeared from the frame, place the mouse near the center of the object and press ‘c’. The target star should be re-identified as well, but if it is not or is improperly, the target star can be identified by placing the mouse over the target star and pressing ‘t’. A single frame can be removed from the analysis by pressing ‘D’, and undeleted by pressing ‘u’ with that frame displayed in the ImageData plot.

When complete, the user can close the display either using the quit button or simply by closing the window. If any new photometry has been performed, the fileout file will be written with the new values. The format for fileout will be the same as the indata file.

Observations:

–> saltview images=”object.fits” outfile=”object.dat” outfile=”object.newdat” srcfile=”targets.dat” fps=”10” phottype=’optimal’ sigdet=5 contpix=10 vignfile=”iraf/extern/salt/salticam/data/SALTICAMslot.def” clobber=y logfile=salt.log verbose=y

Time and disk requirements

The newfits file produced by SLOTPHOT may be very large and as such, it is suggested that a minimum of 512 Mb of RAM be available for the program. As SLOTVIEW does completely read in the newfits file, this may require a large amount of memory and may take some time depending on the system specifications.

Bugs and limitations

The current version of SLOTVIEW has been tested only on SALTICAM slot mode data using slotphot analysis.

Send feedback and bug reports to salthelp@saao.ac.za

See also

saltslot slotphot