APSFFit: An automatic procedure for photometry and astrometry in crowded fields

• Leonardo A. Almeida USP

Abstract

A number of astronomical problems require accurate measurements of the brightness of stars located in crowded fields. These include the search for extrasolar planets, gravitational microlensing amplification events, as well as the search for variable stars. In this work, I describe an automatic procedure for photometry and astrometry in crowded fields (APSFFit) using a methodology similar to the one used in DAOPHOT/IRAF, but with capability of processing a list of the images automatically. This procedure uses the Amoeba algorithm to fit either a Gaussian function or a Moffat function to the stellar profile. Two applications are presented: the light curve of the eclipsing binary BUL SC16 335 which is located in the Galactic bugle and the identification of the flaring components of the astrometric triple LHS 1070. Although not shown in the body of this paper, the astrometric and photometric precision obtained by APSFFit and DAOPHOT is similar.

References

Almeida, L. A., Jablonski, F., and Martioli, E. (2011). Identication of strong photometric activity in the components of LHS 1070. A&A, 525:A84.

Costa, E., Méndez, R. A., Jao, W.-C., Henry, T. J., Subasavage, J. P., Brown, M. A., Ianna, P. A., and Bartlett, J. (2005). The Solar Neighborhood. XIV. Parallaxes from the Cerro Tololo Inter-American Observatory Parallax Investigation-First Results from the 1.5 m Telescope Program. AJ, 130:337–349.

Leinert, C., Jahreiß, H., Woitas, J., Zucker, S., Mazeh, T., Eckart, A., and Köhler, R. (2001). Dynamical mass determination for the very low mass stars LHS 1070 B and C. A&A, 367:183–188.

Polubek, G., Pigulski, A., Baran, A., and Udalski, A. (2007). BUL–SC16 335: A New Eclipsing Pre-Cataclysmic Binary with a Very Short Orbital Period. In Napiwotzki, R. and Burleigh, M. R., editors, 15th European Workshop on White Dwarfs, volume 372 of Astronomical Society of the Pacic Conference Series, page 487.

Press, W. H., Teukolsky, S. A., Vetterling, W. T., and Flannery, B. P. (1992). Numerical recipes in FORTRAN. The art of scientic computing.

Seifahrt, A., Röll, T., Neuhäuser, R., Reiners, A., Kerber, F., Käu, H. U., Siebenmorgen, R., and Smette, A. (2008). Improved orbital solution and masses for the very low-mass multiple system LHS 1070. A&A, 484:429–434.