The r-Process in Neutrino-Driven Winds from Nascent, "Compact" Neutron Stars of Core-Collapse Supernovae

We present calculations of r-process nucleosynthesis in neutrino-driven winds from the nascent neutron stars of core-collapse supernovae. A full dynamical reaction network for both the alpha-rich freezeout and the subsequent r-process is employed. The physical properties of the neutrino-heated ejecta are deduced from a general relativistic model in which spherical symmetry and steady flow are assumed. Our results suggest that proto-neutron stars with a large compaction ratio provide the most robust physical conditions for the r-process. The third peak of the r-process is well reproduced in the winds from these ``compact'' proto-neutron stars even for a moderate entropy, \sim 100-200 N_A k, and a neutrino luminosity as high as \sim 10^{52} ergs s^{-1}. This is due to the short dynamical timescale of material in the wind. As a result, the overproduction of nuclei with A \lesssim 120 is diminished (although some overproduction of nuclei with A \approx 90 is still evident). The abundances of the r-process elements per event is significantly higher than in previous studies. The total-integrated nucleosynthesis yields are in good agreement with the solar r-process abundance pattern. Our results have confirmed that the neutrino-driven wind scenario is still a promising site in which to form the solar r-process abundances. However, our best results seem to imply both a rather soft neutron-star equation of state and a massive proto-neutron star which is difficult to achieve with standard core-collapse models. We propose that the most favorable conditions perhaps require that a massive supernova progenitor forms a massive proto-neutron star by accretion after a failed initial neutrino burst.Comment: 12 pages, 6 figures, accepted for publication in the Astrophysical Journa

General relativistic effects on neutrino-driven wind from young, hot neutron star and the r-process nucleosynthesis

Neutrino-driven wind from young hot neutron star, which is formed by supernova explosion, is the most promising candidate site for r-process nucleosynthesis. We study general relativistic effects on this wind in Schwarzschild geometry in order to look for suitable conditions for a successful r-process nucleosynthesis. It is quantitatively discussed that the general relativistic effects play a significant role in increasing entropy and decreasing dynamic time scale of the neutrino-driven wind. Exploring wide parameter region which determines the expansion dynamics of the wind, we find interesting physical conditions which lead to successful r-process nucleosynthesis. The conditions which we found realize in the neutrino-driven wind with very short dynamic time scale $\tau_{\rm dyn} \sim 6$ ms and relatively low entropy $S \sim 140$. We carry out the $\alpha$-process and r-process nucleosynthesis calculation on these conditions by the use of our single network code including over 3000 isotopes, and confirm quantitatively that the second and third r-process abundance peaks are produced in the neutrino-driven wind.Comment: Accepted for publication in Ap

Neutron-capture elements in the metal-poor globular cluster M15

We report on observations of six giants in the globular cluster M15 (NGC 7078) using the Subaru Telescope to measure neutron-capture elemental abundances. Our abundance analyses based on high-quality blue spectra confirm the star-to-star scatter in the abundances of heavy neutron-capture elements (e.g., Eu), and no significant s-process contribution to them, as was found in previous studies. We have found, for the first time, that there are anti-correlations between the abundance ratios of light to heavy neutron-capture elements ([Y/Eu] and [Zr/Eu]) and heavy ones (e.g., Eu). This indicates that light neutron-capture elements in these stars cannot be explained by only a single r-process. Another process that has significantly contributed to the light neutron-capture elements is required to have occurred in M15. Our results suggest a complicated enrichment history for M15 and its progenitor.Comment: Accepted to ApJ

Association between reduced serum BDNF levels and insomnia with short sleep duration among female hospital nurses

Objective: Previous studies have suggested that brain-derived neurotrophic factor (BDNF) is associated with sleep regulation in humans. However, its relationship with self-reported sleep problems has not been clarified. The aim of the present study was to examine the association between serum BDNF levels and sleep problems among hospital nurses. Methods: Participants were enrolled from among nurses working at a general hospital in Tokyo, Japan. Data from 577 women (age: 35.45 ± 10.90 years) were analyzed. This cross-sectional survey was conducted from November to December 2015. Serum BDNF concentrations were evaluated. Participants completed a self-reported questionnaire on sleep including the presence or absence of insomnia symptoms (ie, difficulty initiating sleep (DIS), difficulty maintaining sleep (DMS), and early morning awakening [EMA]), and sleep duration. Insomnia with short sleep duration (ISS) was defined as: DIS, or DMS, or EMA; and <6 h sleep duration. Results: Among 577 participants, 21.3% reported insomnia, 41.4% slept less than 6 h, and finally 12.5% suffered from ISS. Serum BDNF levels were significantly lower in subjects with ISS than in those without ISS. The serum BDNF levels in insomniacs were significantly lower than in non-insomniacs for short sleep duration (<6 h), while serum BDNF levels did not differ between insomniacs and non-insomniacs for normal sleep duration (≥6 h). Conclusion: This is the first documented study to indicate that ISS is associated with reduced serum BDNF levels. These results may lead to clarification of the underlying pathophysiological relationship between BDNF and poor sleep

Classical and Quantum Solutions and the Problem of Time in R2R^2 Cosmology

We have studied various classical solutions in $R^2$ cosmology. Especially we have obtained general classical solutions in pure $R^2$\ cosmology. Even in the quantum theory, we can solve the Wheeler-DeWitt equation in pure $R^2$\ cosmology exactly. Comparing these classical and quantum solutions in $R^2$\ cosmology, we have studied the problem of time in general relativity.Comment: 17 pages, latex, no figure, one reference is correcte