The mass distribution of Galactic double neutron stars

The conventional wisdom, dating back to 2012, is that the mass distribution of Galactic double neutron stars is well-fit by a Gaussian distribution with a mean of $1.33 M_\odot$ and a width of $0.09 M_\odot$. With the recent discovery of new Galactic double neutron stars and GW170817, the first neutron star merger event to be observed with gravitational waves, it is timely to revisit this model. In order to constrain the mass distribution of double neutron stars, we perform Bayesian inference using a sample of 17 Galactic double neutron stars effectively doubling the sample used in previous studies. We expand the space of models so that the recycled neutron star need not be drawn from the same distribution as the non-recycled companion. Moreover, we consider different functional forms including uniform, single-Gaussian, and two-Gaussian distributions. While there is insufficient data to draw firm conclusions, we find positive support (a Bayes factor of 9) for the hypothesis that recycled and non-recycled neutron stars have distinct mass distributions. The most probable model---preferred with a Bayes factor of 29 over the conventional model---is one in which the recycled neutron star mass is distributed according to a two-Gaussian distribution and the non-recycled neutron star mass is distributed uniformly. We show that precise component mass measurements of $\approx 20$ double neutron stars are required in order to determine with high confidence (a Bayes factor of 150) if recycled and non-recycled neutron stars come from a common distribution. Approximately $60$ are needed in order to establish the detailed shape of the distributions.Comment: Minor update of PSR J1913+1102 masses, 13 pages, 7 figures, 5 table

Research in Economics and Management in France: A bibliometric study using the h-index

This paper presents an application of new measures of research excellence, namely Hirsch's index (2005) and derived indexes. It gives a ranking of French departments of Economics, departments of Management and Business schools based on the quality of the academic environment offered by these institutions using these measures. It argues that, since the bulk of the research is done by a very small number of researchers, a greater concentration of the best researchers seems necessary for France to achieve international visibility in Economics and Management.h-index, g-index, publication activity