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Stellar Objects with Infrared Excess in the\textit {Spitzer Space Telescope} Wide-Area Infrared Extragalactic Survey (SWIRE)

We have identified two new debris disk candidates in the \textit{Spitzer Space Telescope} Legacy Project Wide-Area InfraRed Extragalactic Survey (SWIRE). We searched two of the six SWIRE photometric survey fields, and present 3.6-160 μ m photometry obtained with the Infrared Array Camera (IRAC) and the Multiband Imaging Photometer (MIPS) instruments. We followed up the candidates with spectro-photometry from 4-36 μ m using the Infrared Spectrometer (IRS) low resolution modules. The candidates spectral energy distributions (SEDs) were constructed from Keck's LRIS optical spectroscopy, \textit{2MASS} J, H, Ks, \textit{Spitzer's} IRAC 3.6, 4.5, 5.8, 8.0 μ m bands, and MIPS 24 m photometry (70 and 160 μ m when detected). The two candidates, Lockman_tile32_1228 and EN1_tile22_11767, were selected by their 24 μ m emission above photospheric expected levels, an indicator of the Vega phenomenon, or the presence of circumstellar dust at ˜120 K. Object Lockman_tile32_1228 has 70 and 160 μ m surplus in flux, suggesting the presence of cold dust represented by blackbody curves of ˜65 and ˜23 Kelvin. The infrared spectra reveal both sources to have infrared excess at wavelengths shorter than 24 μ m as well. The shape of Lockman_tile32_1228's SED exhibits interesting features from 8 to 20 μ m, possibly due to the composition of the emitting material. To confirm these sources are stellar objects, 0.32-0.95 μ m optical spectra was obtained via W.M. Keck Observatory's LRIS dual spectrometer. LRIS blue and red arm spectroscopy confirms the candidates are K-type main sequence stars about 195 and 160 pc away from the Sun. At high-galactic latitudes, where interstellar material is scarce, the SEDs of these sources illustrate there can exist a diversity of debris disk evolutionary states in foreground stars of the Galaxy.

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