Quantitative spectroscopic analysis of and distance to SN1999em

This work presents a detailed quantitative spectroscopic analysis of, and the determination of the distance to, the type II supernovae (SN) SN1999em with CMFGEN (Dessart & Hillier 2005a), based on spectrophotometric observations at eight dates up to 40 days after discovery. We use the same iron-group metal content for the ejecta, the same power-law density distribution (with exponent n~10), and a Hubble-velocity law at all times. We adopt a H/He/C/N/O abundance pattern compatible with CNO-cycle equilibrium values for a RSG/BSG progenitor, with C/O enhanced and N depleted at later times. Based on our synthetic fits to spectrophotometric observations of SN1999em, we obtain a distance of 11.5Mpc, similar to that of Baron et al. (2004) and the Cepheid distance to the galaxy host of 11.7Mpc (Leonard et al. 2003). Similarly, based on such models, the Expanding Photosphere Method (EPM) delivers a distance of 11.6Mpc, with negligible scatter between photometric bandpass sets; there is thus nothing wrong with the EPM as such. Previous determinations using the tabulated correction factors of Eastman et al. (1996) all led to 30-50% underestimates: we find that this is caused by 1) an underestimate of the correction factors compared to the only other study of the kind by Dessart & Hillier (2005b), 2) a neglect of the intrinsic >20% scatter of correction factors, and 3) the use of the EPM at late times when severe line blanketing makes the method inaccurate. The need of detailed model computations for reliable EPM distance estimates thus defeats the appeal and simplicity of the method. However, detailed fits to SN optical spectra, based on tailored models for individual SN observations, offers a promising approach to obtaining distances with 10-20% accuracy, either through the EPM or a la Baron et al. (2004).Comment: 20 pages, 13 figures, accepted for publication in A&

DRAKKAR: developing high resolution ocean components for European Earth system models

DRAKKAR is a consortium of European ocean modelling teams. It was “created to take up the challenges of developing realistic global eddy-resolving/ permitting ocean/sea-ice models, and of building an ensemble of high resolution model hindcasts representing the ocean circulation from the 1960s to present” (quoting the DRAKKAR Group, 2007, in a CLIVAR Exchanges paper where the DRAKKAR strategy was presented for the first time). Now in the second decade of its existence, the DRAKKAR Group is active and thriving, and it is now timely to present recent developments and future plans in this special issue of CLIVAR Exchanges

Examining the Engagement of Career Academy and Comprehensive High School Students in the United States

The purpose of this study was to compare the levels of student engagement of career academy students to those at a traditional comprehensive high school using propensity score matching and structural equation modeling. We found that academy students had significantly higher levels of emotional engagement and significantly lower levels of behavioral engagement than those at comprehensive schools. We also found no statistically significant differences in the levels of cognitive engagement of academy students compared to comprehensive school students. We believe the academy model has the promise of transforming the high school experience for students as it relates to their attachment to the school, their relationships with peers and teachers, and their sense of belonging and safety. However, academies need to work with students to create and develop co-curricular and extracurricular activities of interest to engage students in their schools at a higher level