CONSTRAINING MASS RATIO AND EXTINCTION IN THE FU ORIONIS BINARY SYSTEM WITH INFRARED INTEGRAL FIELD SPECTROSCOPY

Abstract

We report low resolution near infrared spectroscopic observations of the\neruptive star FU Orionis using the Integral Field Spectrograph Project 1640\ninstalled at the Palomar Hale telescope. This work focuses on elucidating the\nnature of the faint source, located 0.5" south of FU Ori, and identified in\n2003 as FU Ori S. We first use our observations in conjunction with published\ndata to demonstrate that the two stars are indeed physically associated and\nform a true binary pair. We then proceed to extract J and H band\nspectro-photometry using the damped LOCI algorithm, a reduction method tailored\nfor high contrast science with IFS. This is the first communication reporting\nthe high accuracy of this technique, pioneered by the Project 1640 team, on a\nfaint astronomical source. We use our low resolution near infrared spectrum in\nconjunction with 10.2 micron interferometric data to constrain the infrared\nexcess of FU Ori S. We then focus on estimating the bulk physical properties of\nFU Ori S. Our models lead to estimates of an object heavily reddened, A_V\n=8-12, with an effective temperature of ~ 4000-6500 K . Finally we put these\nresults in the context of the FU Ori N-S system and argue that our analysis\nprovides evidence that FU Ori S might be the more massive component of this\nbinary system\n