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Suggested papers for
Tue, Sep 27, 2016 at 11:00 AM and Thu, Sep 29, 2016 at 11:00 AM

27 Sep 2016

PKDGRAV3: Beyond Trillion Particle Cosmological Simulations for the Next Era of Galaxy Surveys

We report on the successful completion of a 2 trillion particle cosmological simulation to z=0 run on the Piz Daint supercomputer (CSCS, Switzerland), using 4000+ GPU nodes for a little less than 80h of wall-clock time or 350,000 node hours. Using multiple benchmarks and performance measurements on the US Oak Ridge National Laboratory Titan supercomputer, we demonstrate that our code PKDGRAV3, delivers, to our knowledge, the fastest time-to-solution for large-scale cosmological N-body simulatio...

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28 Sep 2016

No Conclusive Evidence for Transits of Proxima b in MOST photometry

The analysis of Proxima Centauri's radial velocities recently led Anglada-Escud\'e et al. (2016) to claim the presence of a low mass planet orbiting the Sun's nearest star once every 11.2 days. Although the a-priori probability that Proxima b transits its parent star is just 1.5%, the potential impact of such a discovery would be considerable. Independent of recent radial velocity efforts, we observed Proxima Centauri for 12.5 days in 2014 and 31 days in 2015 with the MOST space telescope. We r...

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27 Sep 2016

Shaping of the inner Oort cloud by Planet Nine

We present a numerical calculation of the dynamical interaction between the proposed Planet Nine and an initially thin circular debris disk around the Sun for 4Gyr, accounting the secular perturbation of the four giant planets. We show that Planet Nine governs the dynamics in between 1000-5000AU and forms spherical structure in the inner part (~1000AU) surrounded by an inclined disk aligned to its orbital plane. This structure is the outcome of mean motion resonances and secular interaction wit...

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6 Sep 2016

Radial Velocity Data Analysis with Compressed Sensing Techniques

We present a novel approach for analysing radial velocity data that combines two features: all the planets are searched at once and the algorithm is fast. This is achieved by utilizing compressed sensing techniques, which are modified to be compatible with the Gaussian processes framework. The resulting tool can be used like a Lomb-Scargle periodogram and has the same aspect but with much fewer peaks due to aliasing. The method is applied to five systems with published radial velocity data sets...

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24 Sep 2016

Do Some AGN Lack X-ray Emission?

$Context:$ Intermediate-Mass Black Holes (IMBHs) are thought to be the seeds of early Supermassive Black Holes (SMBHs). While $\gtrsim$100 IMBH and small SMBH candidates have been identified in recent years, few have been robustly confirmed to date, leaving their number density in considerable doubt. Placing firmer constraints both on the methods used to identify and confirm IMBHs/SMBHs, as well as characterizing the range of host environments that IMBHs/SMBHs likely inhabit is therefore of con...

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25 Feb 2016

Variability in young very low mass stars: Two surprises from spectrophotometric monitoring

We present simultaneous photometric and spectroscopic observations of seven young and highly variable M dwarfs in star forming regions in Orion, conducted in 4 observing nights with FORS2 at ESO/VLT. All seven targets show significant photometric variability in the I-band, with amplitudes between 0.1-0.8 mag, The spectra, however, remain remarkably constant, with spectral type changes less than 0.5 subtypes. Thus, the brightness changes are not caused by veiling that 'fills in' absorption featu...

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5 Sep 2016

The search for failed supernovae with the Large Binocular Telescope: confirmation of a disappearing star

We present Hubble Space Telescope imaging confirming the optical disappearance of the failed supernova candidate identified by Gerke et al. (2015). This $\sim 25~M_{\odot}$ red supergiant experienced a weak $\sim 10^{6}~L_{\odot}$ optical outburst in 2009 and is now at least 5 magnitudes fainter than the progenitor in the optical. The mid-IR flux has slowly decreased to the lowest levels since the first measurements in 2004. There is faint ($2000-3000~L_{\odot}$) near-IR emission likely associa...

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21 Sep 2016

The effects of host galaxy properties on merging compact binaries detectable by LIGO

Cosmological simulations of galaxy formation can produce present-day galaxies with a large range of assembly and star formation histories. A detailed study of the metallicity evolution and star formation history of such simulations can assist in predicting LIGO-detectable compact object binary mergers. Recent simulations of compact binary evolution suggest the compact object merger rate depends sensitively on the progenitor's metallicity. Rare low-metallicity star formation during galaxy assemb...

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21 Sep 2016

Merging Binary Black Holes from Young and Old Massive Star Clusters

Using numerical models of star clusters spanning a wide range in stellar metallicities (Z) we study the effects of a parent cluster's metallicity on the masses of BBHs merging in the local universe (z<0.2). We connect BBH merger times (t_delay) obtained from models of a given metallicity to the corresponding merger redshifts using a distribution of formation epochs for clusters of that stellar metallicity derived based on the cosmological star formation rate and metallicity evolution. We fin...

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17 Sep 2016

Hypervelocity stars from young stellar clusters in the Galactic Centre

The enormous velocities of the so called hypervelocity stars (HVSs) derive, likely, from close interactions with massive black holes, binary stars encounters or supernova explosions. In this paper, we investigate the origin of hypervelocity stars as consequence of the close interaction between the Milky Way central massive black hole and a passing-by young stellar cluster. We found that both single and binary HVSs may be generated in a burst-like event, as the cluster passes near the orbital pe...

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15 Sep 2016

The Discovery of a Low-Luminosity SPIRAL DRAGN

Standard galaxy formation models predict that large-scale double-lobed radio sources, known as DRAGNs, will always be hosted by elliptical galaxies. In spite of this, in recent years a small number of spiral galaxies have also been found to host such sources. These so-called spiral DRAGNs are still extremely rare, with only $\sim 5$ cases being widely accepted. Here we report on the serendipitous discovery of a new spiral DRAGN in data from the Giant Metrewave Radio Telescope (GMRT) at 322 MHz....

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Updated 2016/09/29 09:57:25

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