THE NATURE AND EVOLUTIONARY STATE OF THE FU ORIONIS BINARY SYSTEM

Journal Article · Thu Mar 15 04:00:00 EDT 2012 · Astronomical Journal (New York, N.Y. Online)

DOI:https://doi.org/10.1088/0004-6256/143/3/55· OSTI ID:22034699

Beck, Tracy L ^[1]; Aspin, C ^[2]

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1. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
2. Institute for Astronomy, University of Hawaii, 640 North Aohoku Place, Hilo, HI 96720 (United States)

In this paper, we present the results of our adaptive optics fed three-dimensional imaging spectroscopy study of the FU Orionis binary system. Although the 0.''5 separation companion to FU Ori is {approx}4 mag fainter, we have easily spatially resolved it in the J, H, and K infrared bands and extract high signal-to-noise spectra of the two stellar components from 1.15 to 2.4 {mu}m. We derive a spectral type of K5{sup +2}{sub -1} for FU Ori S based on the stellar photospheric absorption features and find that it is an actively accreting young star (M-dot{sub acc}{approx} (2-3) Multiplication-Sign 10{sup -8} M{sub Sun} yr{sup -1}) that is likely gravitationally bound to FU Ori. We have found that the continuum shape of FU Ori S is not well fit by our spectral modeling process, and this results in a large uncertainty in the line-of-sight extinction to the star. Yet, by placing FU Ori S on the Hertzsprung-Russell diagram and comparing its estimated location with evolutionary models, we find that it is best fit as a {approx}1.2 M{sub Sun} star with a likely age of less than {approx}2 Myr. If we assume coevality of the stellar components, we have thus placed an estimated age on the FU Ori system. Moreover, assuming the canonical model for the nature of FU Ori in that its optical and infrared absorption features arise primarily from the inner circumstellar disk around a {approx}0.3 M{sub Sun} star, we find that the fainter FU Ori S component is actually the more massive star in the system. Future monitoring of FU Ori S to investigate flux variability and orbital motion should further clarify the nature of this curious young binary.

• OSTI ID: 22034699
• Journal Information: Astronomical Journal (New York, N.Y. Online), Journal Name: Astronomical Journal (New York, N.Y. Online) Journal Issue: 3 Vol. 143; ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION
ACCRETION DISKS
ASTRONOMY
ASTROPHYSICS
BINARY STARS
COMPUTERIZED SIMULATION
EMISSION SPECTROSCOPY
HERTZSPRUNG-RUSSELL DIAGRAM
INFRARED SPECTRA
MAIN SEQUENCE STARS
MONITORING
NOISE
OPTICS
THREE-DIMENSIONAL CALCULATIONS