TY - JOUR
T1 - Spectral Evidence for an Inner Carbon-rich Circumstellar Belt in the Young HD 36546 A-star System
AU - Lisse, C. M.
AU - Sitko, M. L.
AU - Russell, R. W.
AU - Marengo, M.
AU - Currie, T.
AU - Melis, C.
AU - Mittal, T.
AU - Song, I.
N1 - Publisher Copyright:
© 2017. The American Astronomical Society. All rights reserved.
PY - 2017/5/10
Y1 - 2017/5/10
N2 - 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 o, 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.
AB - 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 o, 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.
UR - http://www.scopus.com/inward/record.url?scp=85019492630&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85019492630&partnerID=8YFLogxK
U2 - 10.3847/2041-8213/aa6ea3
DO - 10.3847/2041-8213/aa6ea3
M3 - Article
AN - SCOPUS:85019492630
SN - 2041-8205
VL - 840
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 2
M1 - L20
ER -