Plavchan, Peter and Werner, M. W. and Chen, C. H. and Stapelfeldt, K. R. and Su, K. Y. L. and Stauffer, J. R. and Song, I. (2009) New Debris Disks Around Young, Low-Mass Stars Discovered with the Spitzer Space Telescope. Astrophysical Journal, 698 (2). pp. 1068-1094. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20090917-111058624
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We present 24 μm and 70 μm Multiband Imaging Photometer for Spitzer (MIPS) observations of 70 A through M-type dwarfs with estimated ages from 8 Myr to 1.1 Gyr, as part of a Spitzer guaranteed time program, including a re-analysis of some previously published source photometry. Our sample is selected from stars with common youth indicators such as lithium abundance, X-ray activity, chromospheric activity, and rapid rotation. We compare our MIPS observations to empirically derived K_s - colors as a function of the stellar effective temperature to identify 24 μm and 70 μm excesses. We place constraints or upper limits on dust temperatures and fractional infrared luminosities with a simple blackbody dust model. We confirm the previously published 70 μm excesses for HD 92945, HD 112429, and AU Mic, and provide updated flux density measurements for these sources. We present the discovery of 70 μm excesses for five stars: HD 7590, HD 10008, HD 59967, HD 73350, and HD 135599. HD 135599 is also a known Spitzer IRS (InfraRed Spectrograph) excess source, and we confirm the excess at 24 μm. We also present the detection of 24 μm excesses for 10 stars: HD 10008, GJ 3400A, HD 73350, HD 112429, HD 123998, HD 175742, AT Mic, BO Mic, HD 358623 and Gl 907.1. We find that large 70 μm excesses are less common around stars with effective temperatures of less than 5000 K (3.7^(+7.6)_(–1.1)%) than around stars with effective temperatures between 5000 K and 6000 K (21.4^(+9.5)_(–5.7)%), despite the cooler stars having a younger median age in our sample (12 Myr vs. 340 Myr). We find that the previously reported excess for TWA 13A at 70 μm is due to a nearby background galaxy, and the previously reported excess for HD 177724 is due to saturation of the near-infrared photometry used to predict the mid-infrared stellar flux contribution. In the Appendix, we present an updated analysis of dust grain removal timescales due to grain-grain collisions and radiation pressure, Poynting-Robertson (P-R) drag, stellar wind drag, and planet-dust dynamical interaction. We find that drag forces can be important for disk dynamics relative to grain-grain collisions for L_(IR)/L_* < 10^(–4), and that stellar wind drag is more important than P-R drag for K and M dwarfs, and possibly for young (<1 Gyr) G dwarfs as well.
|Additional Information:||© 2009 The American Astronomical Society. Received 2008 August 21; accepted 2009 April 8; published 2009 May 27. This work is based [in part] on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. This research has made use of the NASA Star and Exoplanet Database (NStED), operated by the Infrared Processing and Analysis Center, California Institute of Technology, under a contract with NASA. Thanks to Geoff Bryden, Farisa Morales, and Thayne Currie for their conversations and comments. We thank the anonymous referee for a thorough referee report.|
|Subject Keywords:||circumstellar matter; planetary systems: formation|
|Official Citation:||New Debris Disks Around Young, Low-Mass Stars Discovered with the Spitzer Space Telescope Peter Plavchan, M. W. Werner, C. H. Chen, K. R. Stapelfeldt, K. Y. L. Su, J. R. Stauffer, and I. Song 2009 ApJ 698 1068-1094 doi: 10.1088/0004-637X/698/2/1068.|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||21 Sep 2009 22:04|
|Last Modified:||26 Dec 2012 11:23|
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