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black holes

This tag is associated with 55 posts

A Faint Black Hole?

The authors report the discovery of perhaps the faintest black hole x-ray binary. But this conclusion is limited by the uncertainty in the distance to the object.

Tracking the Accretion Flow Geometry Around Black Holes

By looking at the spectral changes of the accretion disk emission around black holes, we can trace the physical changes of the accreting material.

Making Lanthanide Metals…or Not

There aren’t many places in the universe that you can find a bunch of free neutrons not already trapped inside a nucleus—except in neutron stars. Luckily, neutron stars in violent mergers with other neutron stars, or with black holes, tend to disperse a little bit of their matter into the interstellar medium. Tidal forces eject some matter as the two objects swing around each other in their final orbits. Then, if an accretion disk forms, winds blown off the surface of the disk disperse even more matter. Surman and her colleagues look at the nucleosynthesis that occurs in this latter process, and find something surprising.

Information Preservation and Weather Forecasting for Black Holes

Stephen Hawking proposes that black holes may not have definite event horizons, meaning they’re really more like “gray” holes.

How Not Detecting Anything Can Be Useful

Null data are still data! Chen & Holz use a lack of detections to place a lower limit on the beaming angle of SGRBs.

What Fed Sgr A* its Latest Meal?

The black hole at the center of our galaxy, Sgr A*, is a very picky eater. However, with the discovery of the G2 cloud, astronomers have had the opportunity to watch the infrequent feeding process in Sgr A* in action. While the origin of this cloud is still debated, research is beginning to suggest that G2 is a gas cloud that was ripped away from a giant star in orbit around our galaxy’s central black hole.

The Changing Faces of Active Galactic Nuclei

Has a multi-wavelength study of AGN across a large redshift range revealed that these energetic giants do not impact upon their host galaxy as significantly as previously thought?

Orbital Decay of X-ray Binaries

In today’s paper, the authors study how the periods of two black hole x-ray binaries are changing. They find that the periods are decaying faster than expected based on standard theoretical arguments.

Pictures of Gravity

Field lines are a powerful tool for building intuition for a complex geometric object.

The Densest Galaxy Discovered

The densest galaxy in the local Universe may have been found. M60-UCD1 is most likely a tidally-stripped remnant of a more massive progenitor galaxy. Strader et al. predicts that the progenitor of M60-UCD1 was ~ 50-200 times more massive, suggesting that it was once an elliptical galaxy that has been stripped of most of its mass.

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