Goodbye to a Dear Friend

I learned today that a dear friend passed away. Hakki Ogelman was not just a colleague, he was a dear friend.  A world-renowned astrophysicist, he was responsible for my first poster presentation at a professional conference; an analysis of the time series data from a gamma-ray burst. That was way back in 1995. Hakki was in charge of the research group Compact Objects at Wisconsin (COW). Hakki suffered a debilitating stroke in the mid 1990's, but perservered. He lost a months-long battle to cancer on 4 September 2011. He passed quietly, for which I am grateful. Goodbye, old friend, I will miss you...

Some new results

MAST has begun to post some research results!

1) I have started to do some dripping handrail models of accretion disks. You can find them here: http://www.madscitech.org/csg/accretion.html

2) James Firmiss and I have begun serious work on neutron star equations of state, results will be put up shortly.

3) Chris Winfield is giving a talk on local solvability at the American Mathematical Society meeting in New Orleans, that talk is located here: http://www.madscitech.org/csg/AMS10mintalk.pdf

4) We are doing research and development of database capabilities in Mathematica, mostly due to the efforts of Rocky Wenz.

More results will be reported as they occur!

Recent Papers of Interest 16 November 2010

Here are some ArXiv papers I found interesting of late.

1) Takami Kuroda and Hideyuki Umeda, Three Dimensional Magneto Hydrodynamical Simulations of Gravitational Collapse of a 15Msun Star

This is an important paper for those of us who study compact objects. It begins with a nice overview of the theory of core-collapse supernovae (CCSN) and the efforts to model these. The next two sections details the code used, both MHD and GR. This is followed by the adaptive mesh scheme used. Finally they discuss the tests of the code. This accounts for half of the paper and makes a very nice overview of modeling MHD in a GR environment. The results are very nice, great paper!

2) Manjit Bhatia, P. Narayana Swamy, Elementary Quantum Mechanics in a Space-time Lattice

This paper explores the particle-in-a-box problem under the assumption of a fundamental length scale forming a spacetime lattice. This is an interesting approach.

3) Oleg Korobkin, Ernazar B. Abdikamalov, et al, Stability of general-relativistic accretion disks,

This paper is a thorough treatment of a model of unstable accretion disks near a black hole.

4) T. Fischer, I. Sagert, et al, The revival of an explosion mechanism of massive stars - the quark hadron phase transition during the early post bounce phase of core collapse supernovae,

This is a long paper (30 pages) explores the bounce during a supernova core collapse caused by the so-called quark hadron phase transition. The introduction is a nicce overview of the topic and its history.  The second section, no pun intended, forms the theoretical core of the paper, describing the hybrid equation of state and other issues. The third section describes the simulation scheme. The fourth section explores the results of the model runs. The conclusion is that the quark matter description leads to early onset of deconfinement, a quark-gluon plasma. A very interesting paper!

The Week of 24-30 October in Astrophysics

Here are four interesting papers from arXiv astrophysics:

1) Francesca Valsecchi, Evert Glebbeek, et al, "Formation of the black-hole binary M33 X-7 via mass-exchange in a tight massive system",

M-33 X-7 is a mystery that this paper proports to solve, maybe. This binary object seems to be a ~16 solar mass black hole orbiting a ~70 solar mass hydrogen-rich O-type companion star. This binary system has a period of ~3.5 days. Up until now, no model explained all of the weird things about this system. This paper contrives a set of circumstances to explain it all.

2) Shigehiro Nagataki, "Rotating BHs as Central Engines of Long GRBs: Faster is Better,"

This paper relates the rotational rate of a black hole to the strength of any relativistic jet produced by it. This is based on numerical relativity calculations using a magnetohydrodynamic code. Four different models are run.

3) Joan M. Centrella, John G. Baker, "Black-hole binaries, gravitational waves, and numerical relativity,"

This is a very nice review of black hole modeling and numerical relativity. Of course, one of the primary applications is the support of gravitational wave detectors.

4) Rachid Ouyed, Mathew Kostka, et al, "Quark nova imprint in the extreme supernova explosion SN 2006gy: the advent of the Quark Star,"

A fascinating possibility is that at the center of neutron stars a special form of matter is produced, one where there is a region of free quarks surrounded by a screen of gluons. This is called a quark-gluon plasma. Such a state of matter was speculative for many decades, but recent results from RHIC (Relativistic Heavy Ion Collider) have given indications that this has been achieved. The authors of this paper suggest that the supernova SN2006gy was in fact a supernova that included a boost to the explosion through the release of energy by the conversion of neutons at the center of the developing neutron star, converting the center into more stable strange quark matter. If true, this is a significant event!