Faint warm debris disks around nearby bright stars explored by AKARI and IRSF

Abstract

Context. Debris disks are important observational clues for understanding planetary-system formation process. In particular, faint warm debris disks may be related to late planet formation near 1 au. A systematic search of faint warm debris disks is necessary to reveal terrestrial planet formation. Aims. Faint warm debris disks show excess emission that peaks at mid-IR wavelengths. Thus we explore debris disks using the AKARI 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 µm detections in the AKARI mid-IR all-sky catalog by comparing their fluxes with the predicted fluxes of the photospheres based on optical to near-IR fluxes and model spectra. The near-IR fluxes are first taken from the 2MASS PSC. However, 286 stars with Ks<4.5 in our sample have large flux errors in the 2MASS photometry due to saturation. Thus we have measured accurate J, H, and Ks band fluxes, applying neutral density (ND) filters for Simultaneous InfraRed Imager for Unbiased Survey (SIRIUS) on IRSF, the φ1.4 m near-IR telescope in South Africa, 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. The detection 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 objects have a large amount of dust for their ages, which cannot be explained by the conventional steady-state collisional cascade model.

Fundamental parameters and infrared excesses of Tycho–Gaia stars

“…In most cases, we therefore expect a slow rise in infrared excess between ∼4 and 25 µm, often including a sudden jump near 10 µm (e.g. Boyer et al 2011;Woods et al 2011;Adams et al 2013;Ishihara et al 2016). There are exceptions.…”

Unbiased Large Spectroscopic Surveys of Galaxies Selected by SPICA Using Dust Bands

“…Here we assume an isotropic distribution of stars with 400 pc in the height of the Galactic disk in the solar neighborhood (Siebert et al 2003). AKARI detected debris disks of luminosity levels ∼ 1 × 10 3 times higher than that of our zodiacal cloud (L Zodi ≃ 1 × 10 −7 L ⊙ ; Nesvorný et al 2010) in an unbiased manner, and revealed that ∼ 10% of the stars possess debris disks at that luminosity threshold (Ishihara et al 2017). Then we estimate what fraction of the main-sequence stars detected in the SMI survey possess detectable debris disks, assuming a luminosity function of debris disks, which is unknown for faint disks and thus could be determined by SPICA.…”

“…(L Zodi 1 × 10 −7 L ; Nesvorný et al 2010) in an unbiased manner, and revealed that ∼10% of the stars possess debris disks at that luminosity threshold (Ishihara et al 2017). Then we estimate what fraction of the main-sequence stars detected in the SMI survey possess detectable debris disks, assuming a luminosity function of debris disks, which is unknown for faint disks and thus could be determined by SPICA.…”

The Statistics of Extended Debris Disks Measured with Gaia and Planck

“…Studies of debris disks with wide field surveys provide measurements of a substantially larger number of potential debris disk hosting stars than pointed observations. Other all-sky surveys used in previous debris disk analyses include IRAS, 2MASS, and AKARI, all observing at shorter wavelengths compared to Planck (Rhee et al 2007;Ishihara et al 2017).…”