Preliminary lightcurves

This memo contains a description of the preliminary lightcurve program (March 95). The program does not aim at producing precise lightcurves but should rather be used to rapidly obtain lightcurves for confirmation of candidates to follow-up during the data taking. It can, nevertheless, also be used to get preliminary lightcurves of established candidates (see examples below). Note, that in order to be visible by this program, images must be loaded in the database and reduced.

The program

Description
You will be asked to select a list of reference images and a list of new images. The first choosen reference will be subtracted to the other reference and new images. For each ref/new pair, a local subtraction is performed. Local meaning that the seeing, transformation and ratio of the images are computed using the candidate closest 25 good stars. The subtraction is done after moving the reference image in the coordinate system of the new one (This implies that the selected reference be a very good image preferably with the smallest pixel size) and convolving the best seeing one to match the other image. The signal is then calculated by integrating the counts in an aperture of 1 FWHM centered at the candidate position. This result and its uncertainty (sky background only) is saved on a file together with the reference and new image name for each subtraction. The signal counts are given in unit of the reference counts and the magnitudes are obtained after matching the reference to the APM catalog.
Syntax
This program is called reylight and is to be run on IDL. The recommanded syntax is :
```
IDL> reylight,cand=candidate_file,filter=filter_number
```
where candidate_file is a string for the selected candidate filename (eg : '2.62558_-1.7825_cand.nc' in for SN#1) and filter_number is an integer code for the selected filter number ( U=2, B=3, V=4, R=5 and I=6). It is set to 0 if not given. By default, a few controlled histograms and plots are printed (on screen). They can be deactivated. See the description of these options and others by typing : IDL> dlib,'reylight'
The name of the output file (containing the calculated signal) is built as follows : output_file_name = candidate_file.filter_number.dat (eg : '2.62558_-1.7825_cand.nc.5.dat' for candidate #1 in R filter). This file is kept in $DEEPHOME/reylight for later update and can be readout by the IDL program plotlight (same syntax as reylight ).

Exemples

Preliminary lightcurves of candidates #1, #2, #5, #6 and #7 are shown below. Other will be added soon. For each candidate, the upper plot shows the 1 FWHM aperture counts in units of the reference counts and the second one the APM calibrated magnitudes. When there exist more than one image at a given date and for a given telescope, the weighted mean is plotted. The size of the common uncertainty contribution from the reference sky noise is plotted in the upper plot with the label : from REF.

Reynald Pain (RGPain@lbl.gov) March 02, 1995