Mid-infrared imaging of young stellar objects

Journal Article · Mon Apr 01 04:00:00 EST 1996 · Astrophysical Journal

DOI:https://doi.org/10.1086/177060· OSTI ID:284642

Liu, M C; Graham, J R ^[1]; Ghez, A M ^[2]; Meixner, M ^[3]; Skinner, C J; Keto, E; Ball, R ^[4]; Arens, J F; Jernigan, J G ^[5]

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1. Department of Astronomy, University of California, Berkeley, California 94720 (United States)
2. Department of Astronomy, University of California, Los Angeles, California 90024 (United States)
3. Department of Astronomy, University of Illinois, Urbana-Champaign, Illinois 61801 (United States)
4. Institute of Geophysics and Planetary Physics, Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)
5. Space Sciences Laboratory, University of California, Berkeley, California 94720 (United States)

We present arcsecond resolution mid-infrared (8{endash}13 {mu}m) images and photometry of four young stellar objects (YSOs){emdash}L1551-IRS 5, HL Tau, AS 205, and AS 209 (V1121 Oph){emdash}taken with the Berkeley Mid-Infrared Camera. For AS 205, a known T Tauri binary, we also present near-infrared {ital JHK} images and {ital HKL}{prime} speckle imaging data. All three single stars are unresolved in our mid-IR images, consistent with current models of the circumstellar material associated with these objects. Our data are the first to resolve in the mid-IR both components of the close binary AS 205 (projected separation {approximately}1{center_dot}{double_prime}3 [210 AU]). Both stars are classical T Tauri stars and possess the 9.7 {mu}m silicate feature in emission. AS 205 North is the IR brighter star in our data, while published observations find it to be the optically fainter star. Assuming that the IR excesses of both components arise from circumstellar disks, we find the emitting regions (the inner few AU) of the disks to be optically thick in the mid-IR. Pre-main-sequence evolutionary models suggest that the AS 205 system is non-coeval; we discuss possible explanations for this result and comment on the evolutionary status of this young binary. All our objects, except perhaps AS 205 South, exhibit changes in their mid-IR flux in measurements separated by intervals of days up to many years; the variations range from 30{percent}{endash}300{percent}. For the classical T Tauri stars AS 205 North and AS 209, the magnitude of the changes seems to discount the possibility that the mid-IR variations have the same origin as the optical and near-IR variability of T Tauri stars, namely, accretion-related features on or near the stellar photosphere. We speculate that the cause of the variability lies in the accretion disks of these objects; the data suggest disk accretion rate fluctuations of nearly an order of magnitude. (Abstract Truncated)

• OSTI ID: 284642
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 461; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ACCRETION DISKS
BINARY STARS
CIRCUMSTELLAR DISKS
CLOSE BINARY STARS
FLUCTUATIONS
IMAGES
INFRARED RADIATION
OPACITY
PHOTOMETRY
PROTOSTARS
STAR EVOLUTION
STELLAR PHOTOSPHERES
T TAURI STARS
VISUAL BINARY STARS
YOUNG STARS