Astrophys. J., 840, L20-L20 (2017/May-2)
Spectral evidence for an inner carbon-rich circumstellar belt in the young HD 36546 A-star system.
LISSE C.M., SITKO M.L., RUSSELL R.W., MARENGO M., CURRIE T., MELIS C., MITTAL T. and SONG I.
Abstract (from CDS):
Using the NASA/IRTF SpeX and BASS spectrometers we have obtained 0.7-13 µm observations of the newly imaged 3-10 Myr old HD 36546 disk system. The SpeX spectrum is most consistent with the photospheric emission expected from an L* ∼ 20 L☉, solar abundance A1.5V star with little to no extinction, and excess emission from circumstellar dust detectable beyond 4.5 µm. Non-detections of CO emission lines and accretion signatures point to the gas-poor circumstellar environment of a very old transition disk. Combining the SpeX + BASS spectra with archival WISE/AKARI/IRAS/Herschel photometry, we find an outer cold dust belt at ∼135 K and 20-40 au from the primary, likely coincident with the disk imaged by Subaru, and a new second inner belt with a temperature ∼570 K and an unusual, broad SED maximum in the 6-9 µm region, tracing dust at 1.1-2.2 au. An SED maximum at 6-9 µm has been reported in just two other A-star systems, HD 131488 and HD 121191, both of ∼10 Myr age. From Spitzer, we have also identified the ∼12 Myr old A7V HD 148657 system as having similar 5-35 µm excess spectral features. The Spitzer data allows us to rule out water emission and rule in carbonaceous materials-organics, carbonates, SiC-as the source of the 6-9 µm excess. Assuming a common origin for the four young A-star systems' disks, we suggest they are experiencing an early era of carbon-rich planetesimal processing.
© 2017. The American Astronomical Society. All rights reserved.
circumstellar matter - infrared: stars - planetary systems - radiation mechanisms: thermal - scattering - techniques: spectroscopic - techniques: spectroscopic
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