Structure and Evolution of Debris Disks Around F-Type Stars. I. Observations, Database, and Basic Evolutionary Aspects

Abstract

Although photometric and spectroscopic surveys with the Spitzer Space Telescope increased remarkably the number of well studied debris disks around A-type and Sun-like stars, detailed analyzes of debris disks around F-type stars remained less frequent. Using the MIPS camera and the IRS spectrograph we searched for debris dust around 82 F-type stars with Spitzer. We found 27 stars that harbor debris disks, nine of which are new discoveries. The dust distribution around two of our stars, HD 50571 and HD 170773, was found to be marginally extended on the 70µm MIPS images. Combining the MIPS and IRS measurements with additional infrared and submillimeter data, we achieved excellent spectral coverage for most of our debris systems. We have modeled the excess emission of 22 debris disks using a single temperature dust ring model and of 5 debris systems with two-temperature models. The latter systems may contain two dust rings around the star. In accordance with the expected trends, the fractional luminosity of the disks declines with time, exhibiting a decay rate consistent with the range of model predictions. We found the distribution of radial dust distances as a function of age to be consistent with the predictions of both the self stirred and the planetary stirred disk evolution models. A more comprehensive investigation of the evolution of debris disks around F-type stars, partly based on the presented data set, will be the subject of an upcoming paper.

The VLT/NaCo large program to probe the occurrence of exoplanets and brown dwarfs in wide orbits

“…The system has an additional very wide (216 arcsec = 13 000 AU projected separation) common proper motion star, HIP 12361 = HD 16743. Moór et al (2011) measured for this star a similar RV to those of HD 16699 A and B, and noted a fully consistent trigonometric parallax. It is then likely that the stars form a quadruple system.…”

“…The composite nature of TYC 8484-1507-1 might somewhat alter some of the parameters. The very young isochrone age derived by Moór et al (2011;12 Myr) for TYC 8484-1507-1 is due to this. After correcting the photometry for the flux of the new visual component, the star lies close to the main sequence.…”

Extrasolar planets and brown dwarfs around A-F type stars

“…Rhee et al (2007) estimated the age of the companion to be about 50 Myr based on its (K, V − K S ) properties and showed that the galactic (U, V, W) motion of the system is typical of a young population. We did a more robust isochronal analysis, using absolute K S -band magnitude and a spectroscopic determination of the spectral type by Moór et al (2011). We converged to a similar age of 40 ± 20 Myr, which is also incompatible with the Li age determination of the primary.…”

“…Using the BT-Settl isochrones of Allard et al (2012) derived from the stellar evolution models of Chabrier et al (2000), we find an age of 100 +100 −50 Myr. We note that our temperature estimate includes larger error bars than the estimation of Moór et al (2011), which had an uncertainty of 70 K, as we corrected the systematic error in effective temperature arising from binarity. This correction is quite crude because we can only use one single low S/N point of resolved photometry (Δz = 0.9 ± 0.27, Janson et al 2012).…”

“…An infrared (IR) excess was detected with the InfraRed Astronomical Satellite (IRAS) that Rhee et al (2007) attributed to a cold dust of ∼100 K in a ring at ∼18 au from the star. On the other hand, using Spitzer data, Moór et al (2011) estimated that the dust is located at 55 ± 3 au and has a temperature of 53 ± 1 K.…”