Unveiling the Structure of Pre-Transitional Disks

Abstract

In the past few years, several disks with inner holes that are relatively empty of small dust grains have been detected and are known as transitional disks. Recently, Spitzer has identified a new class of "pre-transitional disks" with gaps based on near-infrared photometry and mid-infrared spectra; these objects have an optically thick inner disk separated from an optically thick outer disk by an optically thin disk gap. A near-infrared spectrum provided the first confirmation of a gap in the pre-transitional disk of LkCa 15 by verifying that the near-infrared excess emission in this object was due to an optically thick inner disk. Here we investigate the difference between the nature of the inner regions of transitional and pre-transitional disks using the same veiling-based technique to extract the near-infrared excess emission above the stellar photosphere. However, in this work we use detailed disk models to fit the excess continua as opposed to the simple blackbody fits used previously. We show that the near-infrared excess emission of the previously identified pre-transitional disks of LkCa 15 and UX Tau A in the Taurus cloud as well as the newly identified pre-transitional disk of Rox 44 in Ophiuchus can be fit with an inner disk wall located at the dust destruction radius. We also present detailed modeling of the broad-band spectral energy distributions of these objects, taking into account the effect of shadowing by the inner disk on the outer disk, but considering the finite size of the star, unlike other recent treatments. The near-infrared excess continua of these three pre-transitional disks, which can be explained by optically thick inner disks, are significantly different from that of the transitional disks of GM Aur, whose near-infrared excess continuum can be reproduced by emission from sub-micron-sized optically thin dust, and DM Tau, whose near-infrared spectrum is consistent with a disk hole that is relatively free of small dust. The structure of pre-transitional disks may be a sign of young planets forming in these disks and future studies of pre-transitional disks will provide constraints to aid in theoretical modeling of planet formation.

Sparse aperture masking interferometry survey of transitional discs

“…ALMA observations taken in 138 and 230GHz (Tsukagoshi et al 2016) revealed a shallow gap of a few percent centred at ∼6 au in agreement with the location of our companion candidate. Espaillat et al (2010) modelled the Spitzer SED and found a disc cavity extending to 36 au containing some optically thin dust consistent with other resolved observations of V2062 Oph. finds a cavity in the disc extending out to 30 au.…”

Circumstellar discs in Galactic centre clusters: Disc-bearing B-type stars in the Quintuplet and Arches clusters

“…We compare our findings to studies of transition discs with near-to mid-infrared emission recently discovered by the Spitzer and AKARI surveys (e.g. Fujiwara et al 2013;Maaskant et al 2013;Espaillat et al 2010Espaillat et al , 2011Muzerolle et al 2010;Teixeira et al 2012;Furlan et al 2009) to investigate the evolutionary state of the disc candidates in the Arches and Quintuplet clusters. The problem of the disc lifetime is addressed, and secondary disc formation will be proposed as a possible scenario to explain the Arches and Quintuplet nearinfrared excess sources and their apparent expanded lifetime compared to primordial discs around Herbig Be stars.…”

Multi-epoch observations with high spatial resolution of multiple T Tauri systems

“…11 and 12. 5 References: (1) Torres et al (2013), (2) Hartigan & Kenyon (2003), (3) Yang et al (2012), (4) Skemer et al (2011), (5) Espaillat et al (2010), (6) White & Ghez (2001), (7) Duchêne et al (1999), (8) Stapelfeldt et al (1998), (9) Furlan et al (2009), (10) Duchêne et al (2010), (11) Harris et al (2012), (12) (TYC 1290-457-1) was observed right after the IRDIFS observation of V1000 Tau, at similar airmass and atmospheric conditions as the science target. The obtained data sets were reduced with the pre-release version 0.15.0-2 of the SPHERE pipeline.…”

“…Espaillat et al (2007) have analysed the Spitzer IRS spectra for UX Tau A and their SED fittings suggested the existence of a disk gap of ≈ 56 AU. A few years later Espaillat et al (2010) measured the gap to be 71 AU wide, using near-infrared spectral measurements. Tanii et al (2012) also examined the disk around UX Tau A, using near-infra-red observations from the Subaru telescope, who found a strongly polarized circumstellar disk surrounding UX Tau A and extending to 120 AU, at a spatial resolution of 0.1 (14 AU).…”