THE DECAY OF DEBRIS DISKS AROUND SOLAR-TYPE STARS

We present a Spitzer MIPS study of the decay of debris disk excesses at 24 and 70 mu m for 255 stars of types F4-K2. We have used multiple tests, including consistency between chromospheric and X-ray activity and placement on the H-R diagram, to assign accurate stellar ages. Within this spectral typ...

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Bibliographic Details
Published in:The Astrophysical journal 2014-04, Vol.785 (1), p.1-13
Main Authors: Sierchio, J M, Rieke, G H, Su, K Y L, Gaspar, Andras
Format: Article
Language:English
Subjects:
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Debris
DECAY
Disks
EVOLUTION
LUMINOSITY
Samples
STARS
Statistical analysis
Statistical methods
X RADIATION
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Summary:We present a Spitzer MIPS study of the decay of debris disk excesses at 24 and 70 mu m for 255 stars of types F4-K2. We have used multiple tests, including consistency between chromospheric and X-ray activity and placement on the H-R diagram, to assign accurate stellar ages. Within this spectral type range, at 24 mu m, 13.6% + or - 2.8% of the stars younger than 1 Gyr have excesses at the 3[sigma] level or more, whereas none of the older stars do, confirming previous work. At 70 mu m, 22.5% + or - 3.6% of the younger stars have excesses at [> or =, slanted]3[sigma] significance, whereas only 4.7 super(+3.7) sub(-2.2)% of the older stars do. To characterize the far-infrared behavior of debris disks more robustly, we doubled the sample by including stars from the DEBRIS and DUNES surveys. For the F4-K4 stars in this combined sample, there is only a weak (statistically not significant) trend in the incidence of far-infrared excess with spectral type (detected fractions of 21.9 super(+4.8) sub(-4.3)%, late F; 16.5 super(+3.9) sub(-3.3)%, G; and 16.9 super(+6.3) sub(-5.0)%, early K). Taking this special type range together, there is a significant decline between 3 and 4.5 Gyr in the incidence of excesses, with fractional luminosities just under 10 super(-5). There is an indication that the timescale for decay of infrared excesses varies roughly inversely with the fractional luminosity. This behavior is consistent with theoretical expectations for passive evolution. However, more excesses are detected around the oldest stars than are expected from passive evolution, suggesting that there is late-phase dynamical activity around these stars.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/785/1/33