Predicting the α Comae Berenices Time of Eclipse: How 3 Ambiguous Measurements out of 609 Caused a 26 Year Binary’s Eclipse to be Missed

The dwarf stars in the 26 year period binary α Com were predicted to eclipse each other in early 2015. That prediction was based on an orbit model made with over 600 astrometric observations using micrometers, speckle interferometry, and long baseline optical interferometry. Unfortunately, it has been realized recently that the position angle measurements for three of the observations from ~100 years ago were in error by 180°, which warped the orbital fit. The eclipse was likely 2 months earlier than predicted (MJD 56979, 2014 November 18 UT, 7 days before the first photometric observations of this system for the season were made at Fairborn Observatory), at which point the system was low on the horizon at sunrise

Catching a grown-up starfish planetary nebula - I. morpho-kinematical study of PC 22

We present the first part of an investigation on the planetary nebula (PN) PC 22 that focuseson the use of deep imaging and high-resolution echelle spectroscopy to perform a detailedmorpho-kinematical analysis. PC 22 is revealed to be a multipolar PN emitting predominantlyin [O III] and displaying multiple non-symmetric outflows. Its central region is found to be alsoparticularly inhomogeneous with a series of low-ionization structures (knots) located on thepath of the outflows. The morpho-kinematical model obtained with SHAPE indicates that (i) thede-projected velocities of the outflows are rather large, ≥100 km s, while the central regionhas expansion velocities in the range ∼25 to ∼45 km s following the 'Wilson effect'; (ii) themajority of the measured structures share similar inclination, ≃100°, i.e. they are coplanar;(iii) and all outflows and lobes are coeval (within the uncertainties). All these results make usto suggest that PC 22 is an evolved starfish PN.We propose that the mechanism responsible forthe morphology of PC 22 consists of a wind-shell interaction, where the fast post-asymptoticgiant branch (AGB) wind flows through a filamentary AGB shell with some large voids.© 2017 The Authors.LS acknowledges support from PAPIIT grant IA-101316 (Mexico). GR-L acknowledges support from CONACYT, CGCI, PRODEP and SEP (Mexico). MAG acknowledges support of the grant AYA 201457280-P, co-funded with FEDER funds. SZ acknowledges support from the UNAM-ITE collaboration agreement 1500-479-3-V-04.Peer Reviewe

Distinctive features of the Gac‐Rsm

Productive plant–bacteria interactions, either beneficial or pathogenic, require that bacteria successfully sense, integrate and respond to continuously changing environmental and plant stimuli. They use complex signal transduction systems that control a vast array of genes and functions. The Gac-Rsm global regulatory pathway plays a key role in controlling fundamental aspects of the apparently different lifestyles of plant beneficial and phytopathogenic Pseudomonas as it coordinates adaptation and survival while either promoting plant health (biocontrol strains) or causing disease (pathogenic strains). Plant-interacting Pseudomonas stand out for possessing multiple Rsm proteins and Rsm RNAs, but the physiological significance of this redundancy is not yet clear. Strikingly, the components of the Gac-Rsm pathway and the controlled genes/pathways are similar, but the outcome of its regulation may be opposite. Therefore, identifying the target mRNAs bound by the Rsm proteins and their mode of action (repression or activation) is essential to explain the resulting phenotype. Some technical considerations to approach the study of this system are also given. Overall, several important features of the Gac-Rsm cascade are now understood in molecular detail, particularly in Pseudomonas protegens CHA0, but further questions remain to be solved in other plant-interacting Pseudomonas.This research was supported by grants BIO2014-55075-P and BIO2017-83533-P from the ERDF/Spanish Ministry of Science, Innovation and Universities - State Research Agency. M.D.F. was supported by a FPU contract from the Spanish MECD/MEFP (ECD/1619/2013)