Faint warm debris disks around nearby bright stars explored by AKARI and IRSF
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Context. Debris disks are important observational clues for understanding planetary-system formation process. In particular, faintwarm debris disks may be related to late planet formation near 1 au. A systematic search of faint warm debris disks is necessary toreveal terrestrial planet formation.Aims. Faint warm debris disks show excess emission that peaks at mid-IR wavelengths. Thus we explore debris disks using theAKARI mid-IR all-sky point source catalog (PSC), a product of the second generation unbiased IR all-sky survey.Methods. We investigate IR excess emission for 678 isolated main-sequence stars for which there are 18 m detections in the AKARImid-IR all-sky catalog by comparing their fluxes with the predicted fluxes of the photospheres based on optical to near-IR fluxes andmodel spectra. The near-IR fluxes are first taken from the 2MASS PSC. However, 286 stars with Ks < 4:5 in our sample have largeflux errors in the 2MASS photometry due to saturation. Thus we have measured accurate J, H, and Ks band fluxes, applying neutraldensity (ND) filters for Simultaneous InfraRed Imager for Unbiased Survey (SIRIUS) on IRSF, the 1.4m near-IR telescope in SouthAfrica, and improved the flux accuracy from 14% to 1.8% on average.Results. We identified 53 debris-disk candidates including eight new detections from our sample of 678 main-sequence stars. Thedetection rate of debris disks for this work is 8%, which is comparable with those in previous works by Spitzer and Herschel.Conclusions. The importance of this study is the detection of faint warm debris disks around nearby field stars. At least nine objectshave a large amount of dust for their ages, which cannot be explained by the conventional steady-state collisional cascade model.
- ASTRONOMY & ASTROPHYSICS
ASTRONOMY & ASTROPHYSICS (601), A72-A72, 2017-05