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HD 48757


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A GLIMPSE into the Nature of Galactic Mid-IR Excesses
We investigate the nature of the mid-IR excess for 31 intermediate-massstars that exhibit an 8 μm excess in either the Galactic LegacyInfrared Mid-Plane Survey Extraordinaire or the Mid-Course SpaceExperiment using high-resolution optical spectra to identify starssurrounded by warm circumstellar dust. From these data we determineprojected stellar rotational velocities and estimate stellar effectivetemperatures for the sample. We estimate stellar ages from thesetemperatures, parallactic distances, and evolutionary models. Using MIPS[24] measurements and stellar parameters we determine the nature of theinfrared excess for 19 GLIMPSE stars. We find that 15 stars exhibitHα emission and four exhibit Hα absorption. Assuming thatthe mid-IR excesses arise in circumstellar disks, we use the Hαfluxes to model and estimate the relative contributions of dust andfree-free emission. Six stars exhibit Hα fluxes that implyfree-free emission can plausibly explain the infrared excess at [24].These stars are candidate classical Be stars. Nine stars exhibitHα emission, but their Hα fluxes are insufficient to explainthe infrared excesses at [24], suggesting the presence of acircumstellar dust component. After the removal of the free-freecomponent in these sources, we determine probable disk dust temperaturesof Tdisk~=300-800 K and fractional infrared luminosities ofLIR/L*~=10-3. These nine stars may bepre-main-sequence stars with transitional disks undergoing diskclearing. Three of the four sources showing Hα absorption exhibitcircumstellar disk temperatures ~=300-400 K,LIR/L*~=10-3, IR colors K-[24]<3.3,and are warm debris disk candidates. One of the four Hα absorptionsources has K-[24]>3.3 implying an optically thick outer disk and isa transition disk candidate.

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观测天体数据

星座:大犬座
右阿森松:06h44m10.85s
赤纬:-18°23'54.8"
视星:8.653
距离:438.596 天文距离
右阿森松适当运动:-3.1
赤纬适当运动:2.3
B-T magnitude:8.634
V-T magnitude:8.652

目录:
适当名称   (Edit)
HD 1989HD 48757
TYCHO-2 2000TYC 5953-883-1
USNO-A2.0USNO-A2 0675-03760933
HIPHIP 32259

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