Astro Coffee

Suggested papers for
Tue, Jul 10, 2018, Thu, Jul 12, 2018, and Fri, Jul 13, 2018 at 11 am

12 Jul 2018

Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A

The IceCube Collaboration, Fermi-LAT, MAGIC, AGILE, + 11 more

Previous detections of individual astrophysical sources of neutrinos are limited to the Sun and the supernova 1987A, whereas the origins of the diffuse flux of high-energy cosmic neutrinos remain unidentified. On 22 September 2017, we detected a high-energy neutrino, IceCube-170922A, with an energy of ~290 tera–electronvolts. Its arrival direction was consistent with the location of a known γ-ray blazar, TXS 0506+056, observed to be in a flaring state. An extensive multiwavelength cam...

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22 Nov 2013

Evidence for High-Energy Extraterrestrial Neutrinos at the IceCube Detector

IceCube Collaboration*

We report on results of an all-sky search for high-energy neutrino events interacting within the IceCube neutrino detector conducted between May 2010 and May 2012. The search follows up on the previous detection of two PeV neutrino events, with improved sensitivity and extended energy coverage down to about 30 TeV. Twenty-six additional events were observed, substantially more than expected from atmospheric backgrounds. Combined, both searches reject a purely atmospheric origin for the 28 events...

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10 Jul 2018

Multi-Wavelength Properties of Radio-loud Narrow-Line Seyfert 1 Galaxies

Radio-loud Narrow-line Seyfert 1 (NLS1) galaxies are unique probes of the formation of powerful radio jets at extreme (near-Eddington) accretion rates and low black hole masses, in a regime very different from classical blazars and, therefore, not probed before. Further, strong thermal and non-thermal components simultaneously present in their spectral energy distributions (SEDs), shed new light on the jet-disk connection at much shorter timescales, given their low SMBH masses. While NLS1 galax...

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10 Jul 2018

The effect of AGN feedback on the migration timescale of supermassive black holes binaries

The gravitational interaction at parsec to sub-parsec scales between a circumbinary gas disc and a super massive black hole binary (SMBHB) is a promising mechanism to drive the migration of SMBHBs toward coalescence. The typical dynamical evolution can be separated in two main regimes: I) Slow migration ($T_{\rm mig}$ $\sim$ $10^{3-4}\times T_{\rm orb}$), where viscous torques are not efficient enough to redistribute the extracted angular momentum from the binary, leading to the formation of a ...

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6 Jul 2018

Dark Matter in Disequilibrium: The Local Velocity Distribution from SDSS-Gaia

We use the distribution of accreted stars in SDSS-Gaia DR2 to demonstrate that the local dark matter halo may not be in equilibrium and that a non-trivial fraction is in substructure. Using a mixture likelihood analysis, we separate the contributions of an old, isotropic stellar halo and a younger anisotropic population. The latter dominates and is uniform within Galactocentric radii of $7.5-10$ kpc and $|z| > 2.5$ kpc. It can be explained as the tidal debris of a disrupted massive satellite...

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28 Jun 2018

Far-IR dust properties of highly dust obscured AGNs from the AKARI and WISE all-sky surveys

The combination of the AKARI and WISE infrared all-sky surveys provides an unique opportunity to identify and characterize the most highly dust obscured AGNs in the universe. Dust-obscured AGNs are not easily detectable and potentially underrepresented in extragalactic surveys due to their high optical extinction, but are readily found in the WISE catalog due to their extremely red mid-IR colors. Combining these surveys with photometry from Pan-STARRS and Herschel, we use SED modeling to charac...

30 Jun 2018

Predicting radial-velocity jitter induced by stellar oscillations based on Kepler data

Radial-velocity (RV) jitter due to intrinsic stellar variability introduces challenges when characterizing exoplanet systems, particularly when studying small (sub-Neptune-sized) planets orbiting solar-type stars. In this Letter we predicted for dwarfs and giants the jitter due to stellar oscillations, which in velocity have much larger amplitudes than noise introduced by granulation. We then fitted the jitter in terms of the following sets of stellar parameters: (1) Luminosity, mass, and effec...

29 Jun 2018

Assembling the Milky Way bulge from globular clusters: Evidence from the double red clump

The two red clumps (RCs) observed in the color-magnitude diagram of the Milky Way bulge is widely accepted as evidence for an X-shaped structure originated from the bar instability. A drastically different interpretation has been suggested, however, based on the He-enhanced multiple stellar population phenomenon as is observed in globular clusters (GCs). Because these two scenarios imply very different pictures on the formation of the bulge and elliptical galaxies, understanding the origin of t...

10 Jul 2018

DEIMOS Observations of WISE-Selected, Optically Obscured AGNs

While there are numerous criteria for photometrically identifying active galactic nuclei (AGNs), searches in the optical and UV tend to exclude galaxies that are highly dust obscured. This is problematic for constraining models of AGN evolution and estimating the AGN contribution to the cosmic X-ray and IR backgrounds, as highly obscured objects tend to be underrepresented in large-scale surveys. To address this, we identify potentially obscured AGNs using mid-IR color colors from the Wide-fiel...

3 Jul 2018

STROBE-X: A probe-class mission for X-ray spectroscopy and timing on timescales from microseconds to years

We describe the Spectroscopic Time-Resolving Observatory for Broadband Energy X-rays (STROBE-X), a probe-class mission concept that will provide an unprecedented view of the X-ray sky, performing timing and spectroscopy over both a broad energy band (0.2-30 keV) and a wide range of timescales from microseconds to years. STROBE-X comprises two narrow-field instruments and a wide field monitor. The soft or low-energy band (0.2-12 keV) is covered by an array of lightweight optics (3-m focal length...

5 Jul 2018

Faraday rotation maps of disk galaxies

Faraday rotation is one of the most widely used observables to infer the strength and configuration of the magnetic field in the ionised gas of the Milky Way and nearby spiral galaxies. Here we compute synthetic Faraday rotation maps at $z=0$ for a set of disk galaxies from the Auriga high-resolution cosmological simulations, for different observer positions within and outside the galaxy. We analyse the formation of the synthetic Faraday rotation signal and compare to observations of the Milky ...

5 Jul 2018

Testing the Breathing Mode in Intermediate Mass Galaxies and its Predicted Star Formation Rate-Size Anti-Correlation

Recent hydrodynamical simulations predict that stellar feedback in intermediate mass galaxies (IMGs) can drive strong fluctuations in structure (e.g., half-light radius, $R_e$). This process operates on timescales of only a few hundred Myr and persists even at late cosmic times. One prediction of this quasi-periodic, galactic-scale "breathing" is an $anti$-correlation between star formation rate (SFR) and half-light radius as central gas overdensities lead to starbursts whose feedback drags sta...

Updated 2018/07/13 11:26:54