Prospects for Measuring Differential Rotation in White Dwarfs Through Asteroseismology

We examine the potential of asteroseismology for exploring the internal rotation of white dwarf stars. Data from global observing campaigns have revealed a wealth of frequencies, some of which show the signature of rotational splitting. Tools developed for helioseismology to use many solar p-mode frequencies for inversion of the rotation rate with depth are adapted to the case of more limited numbers of modes of low degree. We find that the small number of available modes in white dwarfs, coupled with the similarity between the rotational-splitting kernels of the modes, renders direct inversion unstable. Accordingly, we adopt what we consider to be plausible functional forms for the differential rotation profile; this is sufficiently restrictive to enable us to carry out a useful calibration. We show examples of this technique for PG 1159 stars and pulsating DB white dwarfs. Published frequency splittings for white dwarfs are currently not accurate enough for meaningful inversions; reanalysis of existing data can provide splittings of sufficient accuracy when the frequencies of individual peaks are extracted via least-squares fitting or multipeak decompositions. We find that when mode trapping is evident in the period spacing of g modes, the measured splittings can constrain dOmega/dr.Comment: 26 pages, 20 postscript figures. Accepted for publication in The Astrophysical Journa

Lignin dynamics in two13C-labelled arable soils during 18 years

Lignin has long been considered a relatively stable component of soil organic matter. However, recent studies suggest that lignin may turn over within years to decades in arable soil. Here we analyzed lignin concentrations in an 18 year field experiment under continuous silage maize where two soils were sampled at six points in time. Our objectives were to examine the long-term dynamics of (i) lignin derived from a previous C3-vegetation and (ii) lignin derived from maize, as influenced by two levels of maize biomass input. Total lignin concentrations in soil were quantified by gas chromatography of lignin cupric oxide oxidation products. Compound-specific 13C isotope analysis allowed discrimination between C3-derived lignin and maize-derived lignin. Degradation dynamics of C3-derived lignin were independent of biomass input level, suggesting that priming did not affect soil lignin concentrations over almost two decades. After 18 years approximately two thirds of the initial C3-derived lignin remained in the soils, whereas, on average, 10 % of the recent maize-derived lignin input was retained. We suggest that lignin is effectively stabilized in these arable soils, although the mechanisms involved remain unclear

Two-dimensional higher-derivative gravity and conformal transformations

We consider the lagrangian $L=F(R)$ in classical (=non-quantized) two-dimensional fourth-order gravity and give new relations to Einstein's theory with a non-minimally coupled scalar field. We distinguish between scale-invariant lagrangians and scale-invariant field equations. $L$ is scale-invariant for F = c_1 R\sp {k+1} and a divergence for $F=c_2 R$. The field equation is scale-invariant not only for the sum of them, but also for $F=R\ln R$. We prove this to be the only exception and show in which sense it is the limit of \frac{1}{k} R\sp{k+1} as $k\to 0$. More generally: Let $H$ be a divergence and $F$ a scale-invariant lagrangian, then $L= H\ln F$ has a scale-invariant field equation. Further, we comment on the known generalized Birkhoff theorem and exact solutions including black holes.Comment: 16 pages, latex, no figures, [email protected], Class. Quant. Grav. to appea

SN Refsdal: Classification as a Luminous and Blue SN 1987A-like Type II Supernova

We have acquired Hubble Space Telescope (HST) and Very Large Telescope near-infrared spectra and images of supernova (SN) Refsdal after its discovery as an Einstein cross in Fall 2014. The HST light curve of SN Refsdal matches the distinctive, slowly rising light curves of SN 1987A-like supernovae (SNe), and we find strong evidence for a broad H-alpha P-Cygni profile in the HST grism spectrum at the redshift (z = 1.49) of the spiral host galaxy. SNe IIn, powered by circumstellar interaction, could provide a good match to the light curve of SN Refsdal, but the spectrum of a SN IIn would not show broad and strong H-alpha absorption. From the grism spectrum, we measure an H-alpha expansion velocity consistent with those of SN 1987A-like SNe at a similar phase. The luminosity, evolution, and Gaussian profile of the H-alpha emission of the WFC3 and X-shooter spectra, separated by ~2.5 months in the rest frame, provide additional evidence that supports the SN 1987A-like classification. In comparison with other examples of SN 1987A-like SNe, SN Refsdal has a blue B-V color and a high luminosity for the assumed range of potential magnifications. If SN Refsdal can be modeled as a scaled version of SN 1987A, we estimate it would have an ejecta mass of 20+-5 solar masses. The evolution of the light curve at late times will provide additional evidence about the potential existence of any substantial circumstellar material (CSM). Using MOSFIRE and X-shooter spectra, we estimate a subsolar host-galaxy metallicity (8.3+-0.1 dex and <8.4 dex, respectively) near the explosion site.Comment: Submitted to ApJ; 26 page

Gravitational Wave Background from Magnetars

We investigate the gravitational wave background produced by magnetars. The statistical properties of these highly magnetized stars were derived by population synthesis methods and assumed to be also representative of extragalactic objects. The adopted ellipticity was calculated from relativistic models using equations of state and assumptions concerning the distribution of currents in the neutron star interior. The maximum amplitude occurs around 1.2 kHz, corresponding to $\Omega_{gw} \sim 10^{-9}$ for a type I superconducting neutron star model. The expected signal is a continuous background that could mask the cosmological contribution produced in the early stage of the Universe.Comment: accepted for publication in A&A; 17 pages, 7 figures; formula 21 has been corrected with respect to the published versio

A serendipitous all sky survey for bright objects in the outer solar system

We use seven yearʼs worth of observations from the Catalina Sky Survey and the Siding Spring Survey covering most of the northern and southern hemisphere at galactic latitudes higher than 20° to search for serendipitously imaged moving objects in the outer solar system. These slowly moving objects would appear as stationary transients in these fast cadence asteroids surveys, so we develop methods to discover objects in the outer solar system using individual observations spaced by months, rather than spaced by hours, as is typically done. While we independently discover eight known bright objects in the outer solar system, the faintest having $V=19.8\pm 0.1,$ no new objects are discovered. We find that the survey is nearly 100% efficient at detecting objects beyond 25 AU for $V\lesssim 19.1$ ($V\lesssim 18.6$ in the southern hemisphere) and that the probability that there is one or more remaining outer solar system object of this brightness left to be discovered in the unsurveyed regions of the galactic plane is approximately 32%

Momentum asymmetries as CP violating observables

Three body decays can exhibit CP violation that arises from interfering diagrams with different orderings of the final state particles. We construct several momentum asymmetry observables that are accessible in a hadron collider environment where some of the final state particles are not reconstructed and not all the kinematic information can be extracted. We discuss the complications that arise from the different possible production mechanisms of the decaying particle. Examples involving heavy neutralino decays in supersymmetric theories and heavy Majorana neutrino decays in Type-I seesaw models are examined.Comment: 20 pages, 9 figures. Clarifying comments and one reference added, matches published versio

Retromer binds the FANSHY sorting motif in SorLA to regulate amyloid precursor protein sorting and processing

sorLA is a sorting receptor for amyloid precursor protein (APP) genetically linked to Alzheimer's disease (AD). Retromer, an adaptor complex in the endosome-to-Golgi retrieval pathway, has been implicated in APP transport because retromer deficiency leads to aberrant APP sorting and processing and levels of retromer proteins are altered in AD. Here we report that sorLA and retromer functionally interact in neurons to control trafficking and amyloidogenic processing of APP. We have identified a sequence (FANSHY) in the cytoplasmic domain of sorLA that is recognized by the VPS26 subunit of the retromer complex. Accordingly, we characterized the interaction between the retromer complex and sorLA and determined the role of retromer on sorLA-dependent sorting and processing of APP. Mutations in the VPS26 binding site resulted in receptor redistribution to the endosomal network, similar to the situation seen in cells with VPS26 knockdown. The sorLA mutant retained APP-binding activity but, as opposed to the wild-type receptor, misdirected APP into a distinct non-Golgi compartment, resulting in increased amyloid processing. In conclusion, our data provide a molecular link between reduced retromer expression and increased amyloidogenesis as seen in patients with sporadic AD