Day 689

Tuesday.

1406.7431
Luminous blue variables are antisocial: their isolation implies that they are kicked mass gainers in binary evolution
Smith, Tombleson

Based on their relatively isolated environments, argue that LBVs must be primarily the product of binary evolution, challenging the traditional single-star view wherein LBVs mark a brief transition between massive O stars and WR stars.  If the latter were true, then LBVs should be concentrated in young clusters and found alongside MS stars with similarly high inferred initial mass.  This is decidedly not the case.  Examining locations of LBVs compared to O stars in our Galaxy and the Magellanic Clouds reveals that LBVs systematically avoid clusters of O stars, and many reside over 100 pc from any O star.  In the LMC, LBVs are statistically much more isolated than O-type stars, and (perhaps most surprisingly) even more isolated than most WR stars.  This makes it impossible for LBVs to be massive stars in transition to WR stars.  Instead, propose that massive stars and SN subtypes are dominated by bifurcated evolutionary paths in interacting binaries, wherein most WR stars and SNeIbc correspond to the mass donors, while LBVs ( and their lower-mass analogs like B[e] supergiants, which is shown to be even more isolated) are the mass gainers.  LBVs are essentially the late evolutionary stage of massive blue stragglers.  Through binary mass transfer, rejuvenated mass gainers get enriched, spun up, and sometimes kicked far from their clustered birth sites by their companion's SN.  This scenario agrees better with LBVs exploding as SNeIIn and the observed isolation of SNe~IIn and SN impostors.  Argue that environmental trends of various SN subtypes are influenced more by binary and SN kicks, rather than tracing initial mass as is generally assumed.  Mergers of Throne-Zykow objects also give rise to LBVs, but these scenarios may have a harder time explaining why LBVs avoid clusters.

1406.7536
Estimating the distribution of galaxy morphologies on a continuous space
Vinci, Freeman, Neewman, Wasserman, Genovese

The incredible variety of galaxy shapes cannot be summarized by human defined discrete classes of shapes without causing a possibly large loss of information.  Dictionary learning and sparse coding allow reduction of the high dimensional space of shapes into a manageable low dimensional continuous vector space.  Statistical inference can be done in the reduced space via probability distribution estimation and manifold estimation.

1406.7714
The origin of galactic cosmic rays
Amato


Initial discovery of CRs dates back to a century ago (1912).  Their identification as particles rather than radiation dates to about 20 years later and in 20 more years also the first suggestion that they were associated with SNRs was in place.  The basic mechanism behind their acceleration was suggested almost 40 years ago.  Much work has been done wince then to the aim of proving that both the acceleration mechanism and site are well understood, but no definite proof has been obtained: in spite of impressive progress of both theory and observations, the evidence in support of the commonly accepted interpretation is only circumstantial.  In this paper, make the point on where we stand in terms of how the theories confront with data: review recent progress on the subject and try to point to avenues to pursue in order to farther new proofs, if not smoking gun evidence of the origin of Galactic Cosmic Rays.