Demographics of Transition Objects

By J. Najita, S. Strom, J. Muzerolle. 2007

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The unusual properties of transition objects (young stars with an optically thin inner disc surrounded by an optically thick outer disc) suggest that significant disc evolution has occurred in these systems. We explore the nature of these systems by examining their demographics, specifically their stellar accretion rates ˙ M∗ and disc masses Mdisc compared to those of accreting T Tauri stars of comparable age. We find that the transition objects in Taurus occupy a restricted region of the ˙ M∗ versus Mdisc plane. Compared to non-transition single stars in Taurus, they have stellar accretion rates that are typically ∼10 times lower at the same disc mass and median disc masses approximately four times larger. These properties are anticipated by several proposed planet formation theories and suggest that the formation of Jovian mass planets may play a significant role in explaining the origin of at least some transition objects. Considering transition objects as a distinct demographic group among accreting T Tauri stars leads to a tighter relationship between disc masses and stellar accretion rates, with a slope between the two quantities that is close to the value of unity expected in simple theories of disc accretion.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/0d4556e468316edf36328a4147c5d735e7f0ecb4

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Citations in the corpus

Star and Protoplanetary Disk Properties in Orion's Suburbs (2009, background): “Note that Najita et al. (2007) find a median accretion rate of 3.2×10−9 M⊙ yr−1 for their transition disks, which is consistent with the value we find.”
Resolved gas cavities in transitional disks inferred from CO isotopologs with ALMA (2015, background): “The presence of gas inside the dust cavities was discovered through accretion (e.g., Valenti et al. 1993; Najita et al. 2007) and H2 emission (Bergin et al. 2003; Ingleby et al. 2009).”
Spectroastrometric Imaging of Molecular Gas within Protoplanetary Disk Gaps (2008, background): “The recent identification of a significant class of protoplanetary disks with gaps and inner holes in their radial dust distribution has given rise to a debate regarding their origin (Najita et al. 2007).”
On the Diversity of the Taurus Transitional Disks: UX Tauri A and LkCa 15 (2007, background): “Moreover, Najita et al. (2007) have found that the intrinsic properties of transitional disks may favor planet formation.”
Protoplanetary Disks and Their Evolution (2011, background): “Because the focus of this review is on the outer disk, we discuss mid-infrared observations of H2 only and refer the reader to Najita et al. (2007) for details on the inner disk gas component.”
TIME EVOLUTION OF VISCOUS CIRCUMSTELLAR DISKS DUE TO PHOTOEVAPORATION BY FAR-ULTRAVIOLET, EXTREME-ULTRAVIOLET, AND X-RAY RADIATION FROM THE CENTRAL STAR (2009, background): “Transition disks may however also result from processes other than photoevaporation, such as grain growth, planet-disk dynamics or binarity (e.g., Najita et al. 2007).”
DUST FILTRATION BY PLANET-INDUCED GAP EDGES: IMPLICATIONS FOR TRANSITIONAL DISKS (2012, background): “Furthermore, many of these objects also exhibit gas accretion rates comparable to but slightly smaller than T Tauri disk accretion rates (∼ 10−8M⊙ yr−1; Hartmann et al. 1998) onto their central stars (e.g. Calvet et al. 2002, 2005; Espaillat et al. 2007, 2008; Najita et al. 2007).”
TRANSITIONAL AND PRE-TRANSITIONAL DISKS: GAP OPENING BY MULTIPLE PLANETS? (2010, background): “First, the transitional and pre-transitional disk systems exhibit average gas accretion rates close to T Tauri disk accretion rates (∼ 10−8M⊙ yr −1; Hartmann et al. 1998) onto their central stars (e.g. Calvet et al. 2002, 2005; Espaillat et al. 2007, 2008; Najita et al. 2007).”
Accretion onto Pre-Main-Sequence Stars (2016, background): “Comparing accretion rates of transitional disks to those of full disks indirectly informs how much gas is left in the inner cavity and may thereby discriminate between different physical mechanisms that can carve out inner holes (e.g., Najita et al. 2007, Zhu et al. 2011).”
Gas density drops inside dust cavities of transitional disks around young stars observed with ALMA (2015, background): “High accretion rates (∼ 10−8 M⊙ yr−1, e.g. Calvet et al. 2005; Najita et al. 2007) indicate that the dust cavities are not empty, but gas is still flowing through the gap.”
PROTOPLANETARY DISK STRUCTURES IN OPHIUCHUS. II. EXTENSION TO FAINTER SOURCES (2010, background): “At this point, the physical mechanism responsible for the dust evolution in these disk cavities remains a subject of active debate (e.g., see D’Alessio et al. 2005; Najita et al. 2007).”
Protoplanetary disc evolution and dispersal: the implications of X-ray photoevaporation (2010, background): “Furthermore, there have been several observations of discs thought to be caught in the act of clearing (e.g Calvet et al. 2002; Najita et al. 2007); these ‘transition’ discs show a deficit in emission at near-IR (NIR) wavelengths compared to a primordial optically thick disc (one that is optically…”
PROTOPLANETARY DISK STRUCTURES IN OPHIUCHUS (2009, background): “While a variety of mechanisms could produce this kind of structure (see D’Alessio et al. 2005; Najita et al. 2007), perhaps the most compelling is the presence of a giant planet just inside the ring edge.”
A SPATIALLY RESOLVED INNER HOLE IN THE DISK AROUND GM AURIGAE (2009, background): “A wide variety of mechanisms has been invoked to explain the low optical depth of the central regions of transition disks (see e.g. Najita et al. 2007, and references therein), each with different implications for planet formation and the process of evolution between the primordial and debris disk…”
GIANT PLANET MIGRATION, DISK EVOLUTION, AND THE ORIGIN OF TRANSITIONAL DISKS (2009, methodology): “We also omit known binaries from the figure, as well as disks whose classification is uncertain (those classified “C/T” by Najita et al. 2007).”
THE DISK POPULATION OF THE TAURUS STAR-FORMING REGION (2009, background): “There are several possible mechanisms that may drive the evolution of primordial disks, including giant planet formation and the growth and settling of dust grains (Najita et al. 2007, references therein).”