Day 720

Tuesday.

1408.2050
Stellar origin of the 182Hf cosmochronometer and the presolar history of solar system matter
Lugaro et al

Among the short-lived radioactive nuclei inferred to be present in the early solar system via meteoritic analyses, there are several heavier than iron whose stellar origin has been poorly understood.  In particular, the abundances inferred for 182Hf (half-life = 8.9Myr) and 129I (half-life=15.7Myr) are in disagreement with each other if both nuclei are produced by the rapid neutron-capture process.  Here, demonstrate that contrary to previous assumption, the slow neutron-capture process in asymptotic giant branch stars produces 182Hf.  This has allowed us to date the last rapid and slow neutron-capture events that contaminated the solar system material at roughly 100Myr and 30 Myr, respectively, before the formation of the Sun.

1408.2295
Measurement of differential magnification
Er

In gravitational lensing, the magnification effect changes the luminosity and size of a background galaxy.  If the image sizes are not small compared to the scale over which the magnification and shear vary, higher-order distortions occur which are termed differential magnification.  Give an approximation of the magnification gradient for several halo models.  Assuming a symmetric distribution of source brightness, estimate for the differential magnification are obtained and then tested with simulations.  One of the main uncertainties of the estimators comes from the finite resolution of the image.  Study the strength of the method with the resolution of current and future telescopes.  Point out that the method is a potential approach to estimate the first flexion, and can be used to study galaxy and cluster mass profiles.

1408.2337
Supermassive black holes with high accretion rates in active galactic nuclei: II. the most luminous standard candles in the Universe
Wang, et al

Use reverberation mapping (RM) to measure BH mass; identify super-Eddington accreting massive black holes (SEAMBHs) and use their unique properties to construct a new method for measuring cosmological distances.  The saturated bolometric luminosity of such sources is proportional to the BH mass which can be used to obtain their distance.  Report on five new RM measurements and show that in four of the cases, can measure the BH mass and 3 of these sources are SEAMBHs.  Collect more samples.  The ratio of the newly measured distance s to the standard cosmological ones has a mean scatter of 0.14 dex, indicating that SEAMBHs can be used as cosmological distance probes.  With their high luminosity, long period of activity and large numbers at high redshifts, SEAMBs have a potential to extend the cosmic distance ladder beyond the range now explored by Type Ia SNe.