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arXiv · 1704.06348

Spectral Evidence for an Inner Carbon-Rich Circumstellar Dust Belt in the Young HD36546 A-Star System

Carey M. Lisse·Mike L. Sitko·Ray W. Russell·Massimo Marengo·Thayne Currie·Carl Melis·Tushar Mittal·Inseok Song
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Abstract

Using the NASA/IRTF SpeX & BASS spectrometers we have obtained novel 0.7 - 13 um observations of the newly imaged HD36546 debris disk system. The SpeX spectrum is most consistent with the photospheric emission expected from an Lstar ~ 20 Lsun, solar abundance A1.5V star with little/no extinction and excess emission from circumstellar dust detectable beyond 4.5 um. 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 and BASS spectra with archival WISE/AKARI/IRAS/Herschel photometery, we find an outer cold dust belt at ~135K and 20 - 40 AU from the primary, likely coincident with the disk imaged by Subaru (Currie et al. 2017), and a new second inner belt with temperature ~570K and an unusual, broad SED maximum in the 6 - 9 um region, tracing dust at 1.1 - 2.2 AU. An SED maximum at 6 - 9 um has been reported in just two other A-star systems, HD131488 and HD121191, both of ~10 Myr age (Melis et al. 2013). From Spitzer, we have also identified the ~12 Myr old A7V HD148567 system as having similar 5 - 35 um excess spectral features (Mittal et al. 2015). 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 um excess. Assuming a common origin for the 4 young Astar systems' disks, we suggest they are experiencing an early era of carbon-rich planetesimal processing.

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Carey M. Lisse, Mike L. Sitko, Ray W. Russell, Massimo Marengo, Thayne Currie, Carl Melis, Tushar Mittal, Inseok Song. 2017-04-20. Spectral Evidence for an Inner Carbon-Rich Circumstellar Dust Belt in the Young HD36546 A-Star System. https://doi.org/10.3847/2041-8213/aa6ea3

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