Accretion in Evolved and Transitional Disks in Cep OB2: Looking for the Origin of the Inner Holes

We present accretion rates for a large number of solar-type stars in the Cep OB2 region, based on U band observations. Our study comprises 95 members of the ~4 Myr-old cluster Tr 37 (including 20 "transition" objects; TO), as well as the only CTTS in the ~12 Myr-old cluster NGC 7160. The stars show different disk morphologies, with the majority of them having evolved and flattened disks. The typical accretion rates are about one order of magnitude lower than in regions aged 1-2 Myr, and we find no strong correlation between disk morphology and accretion rates. Although half of the TO are not accreting, the median accretion rates of normal CTTS and accreting "transition" disks are similar (~3 10^{-9} and 2 10^{-9} Msun/yr, respectively). Comparison with other regions suggests that the TO observed at different ages do not necessarily represent the same type of objects, which is consistent with the fact that the different processes that can lead to reduced IR excess/inner disk clearing (e.g., binarity, dust coagulation/settling, photoevaporation, giant planet formation) do not operate on the same timescales. Accreting TO in Tr 37 are probably suffering strong dust coagulation/settling. Regarding the equally large number of non-accreting TO in the region, other processes, like photoevaporation, the presence of stellar/substellar companions, and/or giant planet formation may account for their "transitional" SEDs and negligible accretion rates.Comment: 37 pages, 5 figures, 6 tables Accepted by Ap

A General Theory of Oscillon Dynamics

We present a comprehensive, nonperturbative analytical method to investigate the dynamics of time-dependent oscillating scalar field configurations. The method is applied to oscillons in a double well Klein-Gordon model in two and three spatial dimensions, yielding high accuracy results in the characterization of all aspects of the complex oscillon dynamics. In particular, we show how oscillons can be interpreted as long-lived perturbations about an attractor in field configuration space. By investigating their radiation rate as they approach the attractor, we obtain an accurate estimate of their lifetimes in d=3 and explain why they seem to be perturbatively stable in d=2, where d is the number of spatial dimensions.Comment: 15 pages, 17 figures, RevTe

The Transitional Protoplanetary Disk Frequency as a Function of Age: Disk Evolution in the Coronet Cluster, Taurus, and Other 1--8 Myr-old Regions

We present Spitzer 3.6--24 micron photometry and spectroscopy for stars in the 1--3 Myr-old Coronet Cluster, expanding upon the survey of Sicilia-Aguilar et al. (2008). Using sophisticated radiative transfer models, we analyze these new data and those from Sicilia-Aguilar et al. (2008) to identify disks with evidence for substantial dust evolution consistent with disk clearing: transitional disks. We then analyze data in Taurus and others young clusters -- IC 348, NGC 2362, and eta Cha -- to constrain the transitional disk frequency as a function of time. Our analysis confirms previous results finding evidence for two types of transitional disks -- those with inner holes and those that are homologously depleted. The percentage of disks in the transitional phase increases from ~ 15--20% at 1--2 Myr to > 50% at 5--8 Myr; the mean transitional disk lifetime is closer to ~ 1 Myr than 0.1--0.5 Myr, consistent with previous studies by Currie et al. (2009) and Sicilia-Aguilar et al. (2009). In the Coronet Cluster and IC 348, transitional disks are more numerous for very low-mass M3--M6 stars than for more massive K5--M2 stars, while Taurus lacks a strong spectral type-dependent frequency. Assuming standard values for the gas-to-dust ratio and other disk properties, the lower limit for the masses of optically-thick primordial disks is Mdisk ~ 0.001--0.003 M*. We find that single color-color diagrams do not by themselves uniquely identify transitional disks or primordial disks. Full SED modeling is required to accurately assess disk evolution for individual sources and inform statistical estimates of the transitional disk population in large samples using mid-IR colors.Comment: 43 pages in emulateapj format, Accepted for publication in Ap

Mid-morning Break and Poster Sessions: Comorbidity among pathological gamblers seeking treatment

Context of the study Pathological gambling prevalence in the general population: United States 0.42% (Petry et al., 2005), Canada 0.5% (Rush et al., 2008), Quebec 0.7% (Kairouz et al., 2011) Epidemiological surveys (i.e. NESARC) indicate that pathological gambling is usually accompanied by other comorbid disorders, such as: Alcohol and drug abuse (prevalence of 25 and 27%, respectively), alcohol and drug dependence (48 and 11%), mood disorders (50%), anxiety disorders (41%), personality disorders (61%). (Petry et al., 2005) The comorbidity found in clinical samples is usually higher than that in the general population because it is more likely for a person to seek professional help when presenting more symptoms or more psychiatric disorders compared to individuals with only one condition or a less severe problem. (Petry et al., 2005) Importance of assessing the prevalence of comorbid disorders in pathological gamblers in treatment, in order to better address their needs and reduce the risk of recurrence

Between patronage and good governance: organizational arrangements in (local) public appointment processes

This article investigates whether certain organizational arrangements in (local) public appointment processes could encourage the use of appointments as a tool of good governance rather than as a tool of patronage. Specifically, we studied the role of six organizational arrangements in 10 case studies of intra- and inter-organizational public appointment processes held in Italian local government. We found that good governance (in terms of perception of overall integrity and fairness) was found in processes of public appointments where there was independent scrutiny, and when the process involved local councillors and/or external stakeholders – that is, actors beyond those with the formal power to appoint. In these cases, making appointments was seen as a tool of good governance rather than of patronage. These organizational arrangements were more relevant than other ones such as the transparency of public advertisements, job descriptions and educational/professional requirements, and media and public awareness. The article describes the relevant literature and the research study, and discusses implications for research, policy and management

Is the European Central Bank (and the United States Federal Reserve) predictable?

The objective of this paper is to examine the predictability of the monetary policy decisions of the Governing Council of the ECB and the transmission of the unexpected component of the monetary policy decisions to the yield curve. We find, using new methodologies, that markets do not fully predict the ECB decisions but the lack of perfect predictability is comparable with the results found for the United States Federal Reserve. We also find that the impact of monetary policy shocks on bond yields declines with the maturity of the bonds, and that this impact is significantly lower when the shock stems from a monetary policy meeting of the ECB. Using implicit rates instead of bond yields, we find evidence that the market views the ECB as credible. JEL Classification: C22, E52

Protostars and stars in the Coronet cluster: Age, evolution, and cluster structure

We present new optical spectroscopy with FLAMES/VLT, near-IR imaging with HAWK-I/VLT, and 870 micron mapping with APEX/LABOCA of the Coronet cluster. The optical data allow to estimate spectral types, extinction and the presence of accretion in 6 more M-type members, in addition to the 12 that we had previously studied. The submillimeter maps and near-IR data reveal the presence of nebular structures and high extinction regions, which are in some cases associated to known IR, optical, and X-ray sources. Most star formation is associated to two elongated structures crossing in the central part of the cluster. Placing all the 18 objects with known spectral types and extinction in the HR diagram suggests that the cluster is younger than previously thought (<2 Myr, and probably ~0.5-1 Myr). The new age estimate is in agreement with the evolutionary status of the various protostars in the region and with its compactness (<1.3 pc across), but results in a conflict with the low disk and accretion fraction (only 50-65% of low-mass stars appear to have protoplanetary disks, and most transitional and homologously depleted disks are consistent with no accretion) and with the evolutionary features observed in the mid-IR spectra and spectral energy distributions of the disks.Comment: 30 pages, 9 figures, 6 tables, ApJ in pres

Wide-Field Survey of Emission-line Stars in IC 1396

We have made an extensive survey of emission-line stars in the IC 1396 HII region to investigate the low-mass population of pre-main sequence (PMS) stars. A total of 639 H-alpha emission-line stars were detected in an area of 4.2 deg^2 and their i'-photometry was measured. Their spatial distribution exhibits several aggregates near the elephant trunk globule (Rim A) and bright-rimmed clouds at the edge of the HII region (Rim B and SFO 37, 38, 39, 41), and near HD 206267, which is the main exciting star of the HII region. Based on the extinction estimated from the near-infrared (NIR) color-color diagram, we have selected pre-main sequence star candidates associated with IC 1396. The age and mass were derived from the extinction corrected color-magnitude diagram and theoretical pre-main sequence tracks. Most of our PMS candidates have ages of < 3 Myr and masses of 0.2-0.6 Mo. Although it appears that only a few stars were formed in the last 1 Myr in the east region of the exciting star, the age difference among subregions in our surveyed area is not clear from the statistical test. Our results may suggest that massive stars were born after the continuous formation of low-mass stars for 10 Myr. The birth of the exciting star could be the late stage of slow but contiguous star formation in the natal molecular cloud. It may have triggered to form many low-mass stars at the dense inhomogeneity in and around the HII region by a radiation-driven implosion.Comment: 48 pages, 12 figures, 5 tables, accepted for publication in A