ART Data Reduction Pipeline

This package takes raw images and calibration frames and returns cleaned images and photometric lightcurves for the object of interest. It consists of three routines:

art_calibrate.py
art_extract
art_phot.py

The routines are used in the above order. The first and last are python scripts and are called from the command line by:

python /path/to/script.py

art_extract is a c shell script and can be called form the command line by:

/path/to/art_axtract

An outline of each of the routines is given below.

art_calibrate

Purpose: Takes raw science frames and calibration frames. Bias and flat field corrects the science frames.

Input:

• Name of the target object (for naming of images)
• Location of the bias frames
• Location of the flat field frames
• Location of the science frames
• Wildcard specifications of the bias, flat field and science frames (eg. B*.fit for bias frames) Edit the lines indicated at the top of the script to change the input.

Output:

• Master bias frame (in bias frame directory)
• Bias subtracted flat field frames (called Flatcal001.fit etc. in flat field frame directory)
• Master flat field frame and normalised master flat field frame (in flat field frame directory)
• Bias corrected science images in science/image/location/Less_bias/
• Bias and flat field corrected science images in science/image/location/Cal/

Caution:

• Images must all have the same dimensions
• If images already exist they will not be re-calculated
• If you have over 1000 images, make sure they are named Example-0001.fit etc. rather than Example-001.fit. Images names can be changed using Automator in mac. Choose ‘Files and Folders’ and then ‘Get specified Finder items’ and ‘Replace Text’. Then you can select your files and replace ‘-’ with ‘-0’.

Requires:

• Pyraf
• Pyfits
• Spicy
• glob
• os

art_extract

Purpose: Cleans the calibrated images of bad pixels and cosmic rays using BCLEAN. Extracts the fluxes of objects in the field using S-extractor.

Usage:

• Move the SE_config directory to the directory containing the corrected science frames.
• Change directory to the SE_config directory.
• Run art_extract from the command line
• To change BCLEAN parameters, edit line 31 of art_extract.
• To change S-extractor parameters, edit the existing configuration file (or create a new one). The configuration file is specified in line 39.

Output:

. Cleaned images in the directory CleanImages . S-extractor output catalogues in the PhotCatalogues directory

Requires:

• Starlink (Figaro, Convert)
• S-extractor

art_phot

Input:

• Location of S-extractor output catalogues
• Location of calibrated science frames (to construct time array)
• Wild card specifications of catalogues and images
• Where output is to be stored
• Number of parameters returned in the S-extractor catalogue (inspect a catalogue to find this)
• Columns corresponding to x, y and flux in the S-extractor catalogue. Note that first column is 0, second is 1 etc. (inspect a catalogue to find these).
• Positions of the target and reference stars. Use GAIA to inspect a clean image to find these.
• Threshold for target and reference star fluxes. If the flux falls below its threshold, the star is no longer recognised.
• Portion of lightcurve to zoom in on (inspect the output before deciding this) Edit the lines indicated at the top of the script to change the input.

Output:

• Numpy save file with time (Julian Date) and normalised flux arrays. Access this from within a python session by:

  . import numpy as np
  . arrays = np.load(‘/path/to/flux_ratio_save.npz’)
  . time = arrays[‘arr_0’]
  . flux = arrays[‘arr_1’]

• Numpy save files with time and reference star flux ratio arrays (not normalised).

• A .dat file containing time (Julian Date) and normalised flux columns.

• .dat files containing time and reference star flux ratio (one for each reference star).

• Plots of raw flux and normalised flux ratio versus time (lightcurves) with a zoomed in portion also plotted.

Note:

• To add more reference stars, change line 76
• To change the plots produced, change from line 203 onwards

Requires:

• glob
• pyfits
• numpy
• math
• os
• matplotlib

Author: Rebecca Feeny-Barry: December 2012