Abstract
The last decade has seen the discovery of a growing population of planetary-mass companions (<20 MJup; hereafter PMCs) to young stars which are often still in the star-forming regions where they formed. These objects have been found at wide separations (>100 AU) from their host stars, challenging existing models of both star and planet formation. Do these systems represent the low-mass end of the stellar binary model? Are they an extremely high-mass scenario of current planet formation theories? Determining the answers to these questions will come once a statistically robust sample of directly imaged wide-orbit PMCs and stellar binary companions are observed and characterized.
The extensive Spitzer/IRAC data set of every major star-forming region and association within 300 pc has great potential to be mined for wide companions to stars. In this talk, I will discuss the current development of an automated pipeline to find wide-orbit companions of stars via point spread function (PSF) subtraction in Spitzer/IRAC images. A Markov Chain Monte Carlo (MCMC) algorithm is the backbone of this PSF subtraction routine that efficiently creates and subtracts χ2-minimizing instrumental PSFS, measuring infrared photometry of the systems across the four IRAC channels (3.6 μm, 4.5 μm, 5.8 μm, and 8 μm). I will present a re-analysis of archival Spitzer/IRAC images of 11 young, low-mass (0.044-0.88 M¤;K3.5-M7.5) stars in 3 nearby star-forming regions (Chameleon, Taurus, and Upper Scorpius; ~150 pc) known to host faint companions over a range of projected separations (1.7”-7.3”). I will discuss the characteristics of the systems found to have low-mass companions with non-zero [I1] − [I4] colors, potentially signifying the presence of a circum(sub)stellar disk. Finally, I will discuss the prospect for an automated companion search of all known young stars with existing Spitzer/IRAC data and describe potential avenues for follow-up observations of candidate binary and PMC systems.
