HD 101088, An Accreting 14 AU Binary in Lower Centaurus Crux With Very Little Circumstellar Dust

TL;DR

This study investigates a 12-million-year-old binary system, HD 101088, revealing ongoing accretion with minimal circumstellar dust, challenging traditional disk classification methods based solely on infrared luminosity.

Contribution

It provides detailed spectroscopic and photometric analysis of HD 101088, demonstrating active accretion in a system with very little dust, and questions the reliability of infrared luminosity for disk classification.

Findings

Active accretion detected despite low dust mass.

Accretion rate varies over months.

Circumbinary dust mass is less than 0.16 moon masses.

Abstract

We present high resolution (R=55,000) optical spectra obtained with MIKE on the 6.5 m Magellan Clay Telescope as well as Spitzer MIPS photometry and IRS low resolution (R~60) spectroscopy of the close (14 AU separation) binary, HD 101088, a member of the ~12 Myr old southern region of the Lower Centaurus Crux (LCC) subgroup of the Scorpius-Centaurus OB association. We find that the primary and/or secondary is accreting from a tenuous circumprimary and/or circumsecondary disk despite the apparent lack of a massive circumbinary disk. We estimate a lower limit to the accretion rate of > 1x10^-9 solar masses per year, which our multiple observation epochs show varies over a timescale of months. The upper limit on the 70 micron flux allows us to place an upper limit on the mass of dust grains smaller than several microns present in a circumbinary disk of 0.16 moon masses. We conclude that the classification of disks into either protoplanetary or debris disks based on fractional infrared luminosity alone may be misleading.