stdlc_export

stdlc_export.doc

Andrew Layden -- 2000 May 11

Notes on export version of Standard Light Curve Fitting Program.

This program is designed to "fill-in" a poorly-sampled (gappy) light curve of a variable star. It assumes that you know the period of the variable (if not, I have another program -- ask me about it). It will read in the data (rough phase, V magnitude, V error, ..., I magnitude, I error, ...) and fit it with 10 templates (provided). It gives statistics on the 4 best-fits and allows you to plot them using Super Mongo, and then asks you to adopt one of the fits.

It provides a final plot of the light curves in both V and I magnitudes (shifted in phase to correspond with the template's maximum at phase=0) and overplots the adopted template. It also provides light curve properties (intensity-mean V and I mags, V_max, V_min, rise time, epoch of maximum light, etc) derived both from the fitted template and from the original data points (you may chose which affords the best representation of the variable star).

This program was originated for use on very sparsely sampled light curves -- for details, see Layden, A.C. 1998, AJ, 115, 193, "RR Lyrae Variables in the Inner Halo. I. Photometry".

It was further developed for the data in Layden, A. C. & Sarajedini, A. 2000, AJ, 119, 1760, "Photometry of the Globular Cluster M54 and the Sagittarius Dwaft Galaxy: the Age-Metallicity Relation" (see for details).

I will post additional updates to this site as they become available.

1) Files you will need:

stdlc_export.f == Fortran program to fit light curve.
dat.V01 == A sample data file for 1 variable star (see below)
stdlc.all10 == The file containing 10 template light curves.
All relevant files in a UNIX tar file (read with % tar -xvf stdlc_export.tar).
Compile FORTRAN code using -e (132 char lines): f77 stdlc_export.f -e -o stdlc_export.e

2) Run-Time Inputs:

% stdlc_export.e
Enter root name for output data files (rd.* & fd.*): export

This creates two running output files containing the light curve parameters based on Real Data (eg, rd.export) and Fitted Data (eg, fd.export). Each new star is appended to the end of the file.

Enter name of input phot file (HJD,V; q=quit): dat.V01

This is the observed data for the star you want to fit; see dat.V01 to see the format:

First line is the period of the star in days.

Column format: Phase Vmag SM HJD Verr Imag Ierr

(Phase is arbitrary phase value)

(HJD is the heliocentric Julian date with 24500 removed)

(SM is a SuperMongo point style).

Enter error ratio for bad seeing pts (eg 2.0): 2.0

This allows you to put lower weight on data taken from images taken during poor seeing (to minimize blending effects). 1.0 is unweighted, 1.0--2.0 works well for me. The program identifies seeing as good or bad based on the last digit of SM in dat.V01: e.g., for SM=93, the 3 indicates good seeing, for SM=90, the 0 indicates poor seeing. You have to decide which images had seeing better/worse than the median for your data set, and assign values to SM accordingly.

PROGRAM THEN DOES THE FITTING, AND SPITS SOME INFO TO THE SCREEN

Results for best 4 templates:

Islc, A, P0, Vi, chisq = 1 1.370 -0.013 18.756 0.9434E-02
Islc, A, P0, Vi, chisq = 3 1.272 -0.014 18.714 0.1429E-01
Islc, A, P0, Vi, chisq = 2 1.307 -0.004 18.779 0.1659E-01
Islc, A, P0, Vi, chisq = 5 1.193 -0.025 18.675 0.2333E-01

Islc = Nth template in the list of 10.
A = fitted amplitude
P0 = fitted phase shift
Vi = fitted mean V magnitude
chisq = chi-squared value of fit.

SM:
macro read sdat.V01
lc

It has written out a SuperMongo macro called sdat.V01 which you can display using the indicated commands.

Enter plot number (1-4) for final LC: 1

Enter the LINE NUMBER (not the Islc number) of the template you chose as the best light curve for your final analysis. Usually, you will enter "1", since the first line has thesmallest value of chi-squared.
Column format:

outfile <V>f   Vmaxf  Vminf  Amplf dPrf  Emaxf   Nobs slc RMS Pshft
dat.V01 18.227 17.386 18.756 1.370 0.140 641.14426 32 1 0.097 -0.013

Data for the fitted light curve:

<V>f = intensity mean magnitude

Vmaxf = maximum brightness

Vminf = minimum brightness

Amplf = min-max (amplitude)

dPrf = rise time (phase difference between max and min light)

Emaxf = HJD epoch of maximum brightness

Nobs = number of photometric observations (data points)

slc = template number used

RMS = rms scatter of observed potins about template

Pshft = phase shift from original phase.

SM:
macro read zdat.V01
lc

Allows you to plot V and I light curves with best fitted template superimposed on V data.

Enter name of input phot file (HJD,V; q=quit): dat.V02

Enter the dat.* filename of the next star to fit, or quit. Note: in my notation, the variable stars are called V01, V02, etc. Anywhere you see V01 in this document, you can replace it with whatever star you are currently working on, e.g., V24.

3) Output FILES:

adat.V01 = Best fitted curve. Useful!
bdat.V01 = Best 4 fitted LCs.
cdat.V01 = Fitted coefficients for 4 fits.
ddat.V01 = Observed data, shifted in phase to match best template fit. Useful!
fdat.V01 = Final fitted template light curve.
sdat.V01 = SuperMongo macro to plot array of 4 best fits.
gdat.V01 = Final photometry.
rd.export = Real Data, column format is:
- <V>r = intensity mean magnitude (computed from data pts)
- Vmaxr = brightest data point
- Vminr = faintest data point
- Amplr = min-max (amplitude) computed from data pts
- dPrr = rise time (from data points, not fit)
- Emaxf = HJD epoch of maximum brightness (from data pts)
- Nobs = number of photometric observations (data points)
- <I>r = intensity mean I mag (from data pts)
- V-Imin= mean V-I color between 0.5 and 0.8 in phase
- SEM = standard error of the mean of V-Imin
- Nmin = number of data points used to compute V-Imin
fd.export = Fitted Data, column format is:
- <V>f = intensity mean magnitude
- Vmaxf = maximum brightness
- Vminf = minimum brightness
- Amplf = min-max (amplitude)
- dPrf = rise time (phase difference between max and min light)
- Emaxf = HJD epoch of maximum brightness
- Nobs = number of photometric observations (data points)
- slc = template number used
- RMS = rms scatter of observed potins about template
- Pshft = phase shift from original phase.
zdat.V01 = SuperMongo macro to plot best fitted light curve over V and I data points.

Please email me if you have questions, comments, or problems. My appologies for the quality and legibility of the code ... I never intended for it to be "public".

Best of luck,

Andy Layden

ACL - 2000 May 11