The Nature of Transition Circumstellar Disks. Ii. Southern Molecular Clouds

Abstract

Based in part on observations made with ESO telescopes at Paranal and APEX Observatories, under ESO programs 083.C-0459(A), 085.C-0571(D), 083.F-0162(A). This paper includes data gathered with the 6.5-m Magellan Telescopes located at Las Campanas Observatory. AbstractTransition disk objects are pre-main-sequence stars with little or no near-IR excess and significant far-IR excess, implying inner opacity holes in their disks.Here we present a multifrequency study of transition disk candidates located in Lupus I, III, IV, V, VI, Corona Australis, and Scorpius. Complementing the information provided by Spitzer with Adaptive Optics (AO) imaging (NaCo, VLT), submillimeter photometry (APEX), and echelle spectroscopy (Magellan, Du Pont Telescopes), we estimate the multiplicity, disk mass, and accretion rate for each object in our sample in order to identify the mechanism potentially responsible for its inner hole. We find that our transition disks show a rich diversity in their SED morphology, have disk masses ranging from < ∼ 1 to 10 M JUP and accretion rates ranging from < ∼ 10 −11 to 10 −7.7 M yr −1 . Of the 17 bona fide transition disks in our sample, 3, 9, 3, and 2 objects are consistent with giant planet formation, grain growth, photoevaporation, and debris disks, respectively. Two disks could be circumbinary, which offers tidal truncation as an alternative origin of the inner hole. We find the same heterogeneity of the transition disk population in Lupus III, IV, and Corona Australis as in our previous analysis of transition disks in Ophiuchus while all transition disk candidates selected in Lupus V, VI turned out to be contaminating background AGB stars. All transition disks classified as photoevaporating disks have small disk masses, which indicates that photoevaporation must be less efficient than predicted by most recent models. The three systems that are excellent candidates for harboring giant planets potentially represent invaluable laboratories to study planet formation with the Atacama Large Millimeter/Submillimeter Array.. Subject headings: accretion disk -binaries: general -line: identification -planetary systems: protoplanetary disks -stars: pre-main sequence a b " · · · " implies that the signal to noise in this region of the spectrum is too low to measure the width or establish the presence of the line c "-1" implies that Hα is seen in absorption. d "<" implies upper limits value (3 σ) e Sources # 1, 3, 4, and 9 have been identified as binaries by WFI observations . The binary nature of source # 14 was discovered using speckle interferometry at the NTT (La Silla) revealing a projected separation of 0.132 ± 0.009 (Köhler et al. 2008). Sources # 11, 13 are triple systems with tight binary components consistent with two equally bright objects and a projected separation of ∼0.05 .f The spectral type derived by us is significantly later than the previously obtained value. We consider our estimate of M5.25 based on a high quality optical spectrum to be more reliable than the rather rough guess of Merín et...

Evolution of the T Tauri star population in the Lupus association

“…Another interesting point in our study is the existence of six stars (Sz91, Sz95, Sz96, Sz112, RX J1609.9-3923, and RX J1608.5-3847) in our sample that were first identified as CTTSs and later reclassified as transition disk objects (see Romero et al 2012;Tsukagoshi et al 2014). We have labeled them with the mention "CTTS/TD" in Table 1 to distinguish them from the remaining CTTSs.…”

“…We have labeled them with the mention "CTTS/TD" in Table 1 to distinguish them from the remaining CTTSs. Romero et al (2012) claim that RX J1609.9-3923, the youngest transition disk object in the sample, is a "triple system with tight binary components consistent with two equally bright objects". Later in the text, they state that the source has an uncertain classification because its spectral energy distribution resembles a CTTS of M spectral type.…”

“…Eighteen stars in our sample were identified as binary systems in the literature. The photometry of these stars was corrected for binarity with the information (mainly the flux ratio of the components) provided by Reipurth & Zinnecker (1993), Brandner et al (1996), Ghez et al (1997), Guenther et al (2001), Torres et al (2006), and Romero et al (2012).…”

Probing the final stages of protoplanetary disk evolution with ALMA

“…Figure 5 compares the ages and dust masses of the systems in our sample to those in the literature. Literature values for dust mass were all calculated from optically thin emission in a similar manner to this paper, and ages were estimated using either evolutionary track models (Greaves et al 2004;Sheret et al 2004;Matthews et al 2007;Ricci et al 2010;Romero et al 2012), Stromgren photometry (Wyatt et al 2003), lithium lines (Liu et al 2004;Sheret et al 2004;Najita & Williams 2005;Lestrade et al 2006), or cluster membership (Williams & Andrews 2006). The upper limits and detections for our sample clearly show that the dust masses for 23 of the 24 objects lie in the debris disk regime.…”

“…Cyan symbols denote the systems in our sample with detected 1.3 mm flux (numbered for clarity) and red symbols denote those with upper-limits. Black symbols that lie above the dotted line correspond to known protoplanetary disks (data taken from Wyatt et al 2003;Ricci et al 2010;Romero et al 2012). Black symbols in the lower portion correspond to known debris disks (data taken from Greaves et al 2004;Liu et al 2004;Sheret et al 2004;Najita & Williams 2005;Lestrade et al 2006;Williams & Andrews 2006;Matthews et al 2007).…”