On the Diversity of the Taurus Transitional Disks: UX Tauri A and LkCa 15

By Catherine C. Espaillat, N. Calvet, P. D’Alessio, Jesús Hernández, C. Qi, L. Hartmann, E. Furlan, Danisha Watson. 2007

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The recently recognized class of "transitional disk" systems consists of young stars with optically thick outer disks but inner disks which are mostly devoid of small dust grains. Here we introduce a further class of "pre-transitional disks" with significant near-infrared excesses which indicate the presence of an optically thick inner disk separated from an optically thick outer disk; thus, the spectral energy distributions of pre-transitional disks suggest the incipient development of disk gaps rather than inner holes. In UX Tau A, our analysis of the Spitzer IRS spectrum finds that the near-infrared excess is produced by an inner optically thick disk and that a gap of ~56 AU is present. The Spitzer IRS spectrum of LkCa 15 is suggestive of a gap of ~46 AU, confirming previous millimeter imaging. In addition, UX Tau A contains crystalline silicates in its disk at radii ≳ 56 AU which poses a challenge to our understanding of the production of this crystalline material. In contrast, LkCa 15's silicates are amorphous and pristine. UX Tau A and LkCa 15 increase our knowledge of the diversity of dust clearing in low-mass star formation.

Subfields: Astronomy and Astrophysics, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/23effe0f9bc96fa6a74b4d4a5817b3a06ce87fd9

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Citations in the corpus

AN INFRARED/X-RAY SURVEY FOR NEW MEMBERS OF THE TAURUS STAR-FORMING REGION (2009, methodology): “Mid-IR spectroscopy and millimeter imaging of this disk are needed for a detailed characterization of the inner hole (Espaillat et al. 2007a,b; Furlan et al. 2007; Brown et al. 2008; Dutrey et al. 2008; Hughes et al. 2007, 2009).”
PROTOPLANETARY DISK STRUCTURES IN OPHIUCHUS (2009, background): “Alternatively, a “gap” model, where the cavity contains a detached remnant of the inner disk, could generate similar observational signatures (e.g., Espaillat et al. 2007, 2008).”
Protoplanetary Disks and Their Evolution (2011, background): “As part of the c2d project, Spitzer observed over 150 WTTS associated with the Chameleon, Lupus, Ophiuchus, and Taurus star-forming regions, all within 200 pc of the sun.”
Ring shaped dust accumulation in transition disks (2012, background): “They still present relatively high accretion rates (∼ 10−8M yr−1; see e.g.,Calvet et al. (2005); Espaillat et al. (2007)) which implies that the inner cavity is not completely empty and that some gas flows through the gap.”
ACCRETION RATES FOR T TAURI STARS USING NEARLY SIMULTANEOUS ULTRAVIOLET AND OPTICAL SPECTRA (2013, background): “Several of the sources have disks which show evidence for gaps or holes in their infrared spectral energy distributions, including CS Cha, DM Tau, GM Aur and LkCa 15, but all of these sources are still accreting (Strom et al. 1989; Espaillat et al. 2007a,b, 2010).”
DUST FILTRATION BY PLANET-INDUCED GAP EDGES: IMPLICATIONS FOR TRANSITIONAL DISKS (2012, background): “Pre-transitional disks still have some infrared emission from warm, optically-thick dust near the star (Espaillat et al. 2007, 2008, 2010), while transitional disks only have near- and mid-infrared emission from optically-thin dust (Calvet et al. 2002, 2005; Espaillat et al. 2010).”
A Spitzer View of Protoplanetary Disks in the γ Velorum Cluster (2008, methodology): “Two stars have photometric colors between K5 and M0; one of them (star 52) shows infrared excesses similar to pre-transitional disks objects (Espaillat et al. 2007b).”
TRANSITIONAL AND PRE-TRANSITIONAL DISKS: GAP OPENING BY MULTIPLE PLANETS? (2010, background): “…to evacuation of the disk interior to scales ∼ 5 to ∼ 50 AU (Marsh & Mahoney 1992; Calvet et al. 2002, 2005; Rice et al. 2003; Schneider et al. 2003; Espaillat et al. 2007, 2008, 2010; Hughes et al. 2009), an interpretation confirmed in some cases via direct sub-mm imaging (e.g., Pietu et al.…”
Observational Signatures of Planets in Protoplanetary Disks I: Gaps Opened by Single and Multiple Young Planets in Disks (2014, background): “Discovered through their unique infrared deficit from NIR to ∼ 10 µm, which signals a lack of warm dust in the inner disk (Calvet et al. 2005; Espaillat et al. 2007, 2010), these disks have been subsequently shown to harbor large gaps or cavities with sizes often up to tens of AU in spatially…”
THE DISK POPULATION OF THE UPPER SCORPIUS ASSOCIATION (2012, background): “…the disk classifications based on colors from Luhman et al. (2010), Currie & Sicilia-Aguilar (2011) noted that UX Tau A has a disk with a large gap (Espaillat et al. 2007) but did not satisfy the color criteria for a transitional disk from Luhman et al. (2010) and instead was classified as a…”
CRYSTALLINE SILICATES AND DUST PROCESSING IN THE PROTOPLANETARY DISKS OF THE TAURUS YOUNG CLUSTER (2007, background): “…15 disk has a large gap (Piétu et al. 2006)—that is, it is a transitional disk—but the gap is separated from the star by an optically thick inner disk, which in turn extends to the dust-sublimation point (Espaillat et al. 2007; 2008); thus the disk still has an inner edge near the central star.”
PROTOPLANETARY DISK STRUCTURES IN OPHIUCHUS. II. EXTENSION TO FAINTER SOURCES (2010, methodology): “Following the approach of Espaillat et al. (2007) for other “pre-transitional” disks, we proceeded by first finding a good match to the millimeter visi- bilities, and then artificially increasing the surface densities near the star until sufficient infrared emission was produced to match the SED…”
THE ROLE OF MULTIPLICITY IN DISK EVOLUTION AND PLANET FORMATION (2011, background): “The 20–30µm emission from these systems tracks dust out to separations of at least ∼50 AU (as seen from modeling for the inner wall of LkCa 15; Espaillat et al. 2007), so this criterion should include all circumstellar disks and any circumbinary disks out to radii of at least this limit.”
THE DISK POPULATION OF THE TAURUS STAR-FORMING REGION (2009, methodology): “Similar analysis was applied to UX Tau A and LkCa 15, which show evidence of disk gaps (Furlan et al. 2006; Espaillat et al. 2007b).”
LkCa 15: A YOUNG EXOPLANET CAUGHT AT FORMATION? (2011, background): “Finally, if the putative companion was obscured by a massive circumstellar disk, then it should produce significant midinfrared and submm continuum emission that would be distinguished from the outer disk (Espaillat et al. 2007; Andrews et al. 2011).”
The Disk Population of the Chamaeleon I Star-forming Region (2008, background): “We then use the Spitzer photometry of the known members of the cluster to investigate the global properties of the disk population of Chamaeleon I (§ 4).”