2013A&A...556A.119B

A set of six debris disk candidates identified with IRAS or WISE excesses were observed at either 350µm or 450µm with the Caltech Submillimeter Observatory. Five of the targets - HIP51658, HIP68160, HIP73512, HIP76375, and HIP112460 - have among the largest measured excess emission from cold dust from IRAS in the 25-100µm bands. Single temperature blackbody fits to the excess dust emission of these sources predict 350-450µm fluxes above 240mJy. The final target - HIP73165 - exhibits weak excess emission above the stellar photosphere from WISE measurements at 22µm, indicative of a population of warm circumstellar dust. None of the six targets were detected, with 3σ upper limits ranging from 51-239mJy. These limits are significantly below the expected fluxes from SED fitting. Two potential causes of the null detections were explored - companion stars and contamination. To investigate the possible influence of companion stars, imaging data were analyzed from new adaptive optics data from the ARIES instrument on the 6.5m MMT and archival HST, Gemini NIRI, and POSS/2MASS data. The images are sensitive to all stellar companions beyond a radius of 1-94AU, with the inner limit depending on the distance and brightness of each target. One target is identified as a binary system, but with a separation too large to impact the disk. While the gravitational effects of a companion do not appear to provide an explanation for the submm upper limits, the majority of the IRAS excess targets show evidence for contaminating sources, based on investigation of higher resolution WISE and archival Spitzer and Herschel images. Finally, the exploratory submm measurements of the WISE excess source suggest that the hot dust present around these targets is not matched by a comparable population of colder, outer dust. More extensive and more sensitive Herschel observations of WISE excess sources will build upon this initial example to further define the characteristics of warm debris disks sources.