astro-ph coffee suggested papers for Thu, Jan 05, 2012 at 03:00:00 PM

astro-ph coffee will be held at the date and time above in the PAB 3rd-floor reading room. Some suggested papers of interest are listed below.

Web Article:

14 Dec 2011
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S. Gillessen, R. Genzel, T. K. Fritz, E. Quataert, C. Alig, + 7 more
Measurements of stellar orbits provide compelling evidence that the compact radio source Sagittarius A* at the Galactic Centre is a black hole four million times the mass of the Sun. With the exception of modest X-ray and infrared flares, Sgr A* is surprisingly faint, suggesting that the accretion rate and radiation efficiency near the event horizon are currently very low. Here we report the presence of a dense gas cloud approximately three times the mass of Earth that is falling into the accret...

23 Dec 2011

Measurements of the low energy spectrum of Galactic Cosmic Rays (GCR) by detectors at or near the Earth are affected by Solar modulation. To overcome this difficulty, we consider nearby molecular clouds as GCR detectors outside the Solar system. Using gamma-ray observations of the clouds by the Fermi telescope we derive the spectrum of GCRs in the clouds from the observed gamma-ray emission spectrum. We find that the GCR spectrum has a low energy break with the spectral slope hardening by 1.1+/...

4 Jan 2012

Using high signal-to-noise spectra (S/N 30) taken with the Cosmic Origins Spectrograph (COS) of the z=0.9754 quasar PG1148+549, we report on the physical conditions of Ne VIII + OVI absorption line systems at z=0.6838, 0.7015, 0.7248. At these redshifts, absorption lines from multiple ionization stages of oxygen (O II, O III, O IV, O VI) are available to constrain the ionization and physical conditions of the gas. A single-phase model with only photoionization or collisional ionization fails to...

3 Jan 2012

It has long been suspected that metal polluted white dwarfs (types DAZ, DBZ, and DZ) and white dwarfs with dusty disks possess planetary systems, but a specific physical mechanism by which planetesimals are perturbed close to a white dwarf has not yet been fully posited. In this paper we demonstrate that mass loss from a central star during post main sequence evolution can sweep planetesimals into interior mean motion resonances with a single giant planet. These planetesimals are slowly removed...

3 Jan 2012

Two decades ago, empirical evidence concerning the existence and frequency of planets around stars, other than our own, was absent. Since this time, the detection of extrasolar planets from Jupiter-sized to most recently Earth-sized worlds has blossomed and we are finally able to shed light on the plurality of Earth-like, habitable planets in the cosmos. Extrasolar moons may also be frequent habitable worlds but their detection or even systematic pursuit remains lacking in the current literatur...

30 Dec 2011

PDS 144 is a pair of Herbig Ae stars that are separated by 5.35" on the sky. It has previously been shown to have an A2Ve Herbig Ae star viewed at 83\circ inclination as its northern member and an A5Ve Herbig Ae star as its southern member. Direct imagery revealed a disk occulting PDS 144 N - the first edge-on disk observed around a Herbig Ae star. The lack of an obvious disk in direct imagery suggested PDS 144 S might be viewed face-on or not physically associated with PDS 144 N. Multi-epoch H...

astroph.py v0.91ijc based on the original astroph.py. Updated 2012/01/05 14:49:19

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