A Single Circumbinary Disk in the HD 98800 Quadruple System

Abstract

We present subarcsecond thermal infrared imaging of HD 98800, a young quadruple system composed of a pair of low-mass spectroscopic binaries separated by 0&farcs;8 (38 AU), each with a K-dwarf primary. Images at wavelengths ranging from 5 to 24.5 µm show unequivocally that the optically fainter binary, HD 98800B, is the sole source of a comparatively large infrared excess on which a silicate emission feature is superposed. The excess is detected only at wavelengths of 7.9 µm and longer, peaks at 25 µm, and has a best-fit blackbody temperature of 150 K, indicating that most of the dust lies at distances greater than the orbital separation of the spectroscopic binary. We estimate the radial extent of the dust with a disk model that approximates radiation from the spectroscopic binary as a single source of equivalent luminosity. Given the data, the most likely values of disk properties in the ranges considered are Rin=5.0+/-2.5 AU, DeltaR=13+/-8 AU, lambda0=2+4-1.5 µm, gamma=0+/-2.5, and sigmatotal=16+/-3 AU2, where Rin is the inner radius, DeltaR is the radial extent of the disk, lambda0 is the effective grain size, gamma is the radial power-law exponent of the optical depth tau, and sigmatotal is the total cross section of the grains. The range of implied disk masses is 0.001-0.1 times that of the Moon. These results show that, for a wide range of possible disk properties, a circumbinary disk is far more likely than a narrow ring.

Near-Infrared Coronagraphic Imaging of the Circumstellar Disk around TW Hydrae

“…1998; Webb et al 1999), is somewhat older than the ages typically reported for other CTTSs with similar disks, 10 5 to yr (Beckwith et al 1990). It is therefore surprising 6 5 # 10 that TW Hya possesses youthful disk properties, even though it exhibits a stellar age at the upper end of this range and disks around other Association members are considerably more evolved than the TW Hya disk (Koerner et al 1998;Jayawardhana et al 1998Jayawardhana et al , 1999aJayawardhana et al , 1999bSchneider et al 1999;Koerner et al 2000). However, because there can exist a wide variation in initial disk masses and lifetimes (e.g., Osterloh & Beckwith 1995) and because ages for CTTSs in star-forming regions have great uncertainties (due to poorly ascertained distances and extinction corrections), we suggest that disk properties should be taken as the key indicator of a disk evolutionary state that is only approximately correlated with H-R diagram-derived stellar ages.…”

HIGH-RESOLUTION 5 μm SPECTROSCOPY OF TRANSITIONAL DISKS

“…8 (Koerner et al 2000). Both components are themselves spectroscopic binaries with separation 23.7 mas (∼1 AU; Boden et al 2005).…”

Transient dust in warm debris disks

“…(1) Chen et al (2005); (2) Chen et al (2006); (3) Lisse et al (2008); (4) Beichman et al (2005); (5) Lisse et al (2007); (6) Beichman et al (2011); (7) Weinberger (2008); (8) Zuckerman et al (2008); (9) Weinberger et al (2011); (10) Melis et al (2010); (11) Moór et al (2009); (12) Koerner et al (2000); (13) Prato et al (2001); (14) Furlan et al (2007); (15) Verrier & Evans (2008); (16) Gorlova et al (2007); (17) Naylor & Jeffries (2006).…”

“…With their Keck diffraction-limited observations, Prato et al (2001) found that the dust belt surrounds the second spectroscopic binary HD 98800 B, and that the dust belt is located between ∼2 and 5 AU. The structure of the dusty component has also been studied by several authors, for instance, Koerner et al (2000) estimated the disk to be located at r in = 5 ± 2.5 AU with a width r out − r in of 13 ± 8 AU. Furlan et al (2007) also studied the dust content around HD 98800 B with a two components scenario: an optically thin disk located between 1.5 and 2 AU from the spectroscopic binary and an optically thick disk at a distance of 5.9 AU.…”