Discussion: The Birth of a New Black Hole?

[Fraser]

SUMMARY: Monday's gamma ray burst might have been just what astronomers have been hoping to see for decades - the birth of a new black hole. GRB 050509B was a short gamma ray burst, lasting only 50 milliseconds, which means it could be the result of a collision between two neutron stars, or even two black holes. NASA's Swift observatory detected the explosion, tracked its location, and focused its large telescope within a minute of its occurrence.

View full article (http://www.universetoday.com/am/publish/birth_new_black_hole.html)

What do you think about this story? Post your comments below.

[AstroStart.nl]

Well, you can see that the Swift observatory is already a true legend. I think the telescope will discover much more in the future.

[The Near-Sighted Astronomer]

It's interesting that the most exotic type phenomenon possible is being ascribed to GRB 050509B when major papers are coming forward now (based on other dark GRBs) that suggest other less-sophisticated mechanisms. It may very well turn out that black/neutron star assimilation is at cause but most scientists like to first "round up the usual suspects" before playing "the third man" theme song...

[antoniseb]

Originally posted by The Near-Sighted Astronomer@May 11 2005, 07:31 PM
It's interesting that the most exotic type phenomenon possible is being ascribed to GRB 050509B when major papers are coming forward now (based on other dark GRBs) that suggest other less-sophisticated mechanisms. It may very well turn out that black/neutron star assimilation is at cause but most scientists like to first "round up the usual suspects" before playing "the third man" theme song...
I think the lack of afterglows and light echos is pretty clear that whatever is happening, takes place somewhere smaller than 9000 miles across (much smaller than a star) with nothing major around in the way of out-gassed nebulas or other objects. For this particular event, I don't see what other usual suspect could be out there.

[Greg]

Even I with little expierence in this field came to the fairly obvious conclusion that the event was caused by the merger of 2 super-dense objects (in isolation). It is a simple and straightforward theory, which means ithere is a good chance it is correct. But it is always possible that there can be more than one source of such events, so it certainly pays to continue observing.

[Don Alexander]

While this is a lot better than the other story, I do have some comments and corrections to add:

The standard theory for long GRBs, Woosley's Collapsar model, also posits that a long GRB marks the creation of a Black Hole - within a star that goes supernova. So every GRB marks the "birth of a Black Hole", not just this one.

This was not the first short burst Swift detected, but the second one. The first one was 050202 (2nd February, 2005), but it was too close to the sun and was not observed at all.

Something that isn't mentioned at all is that Swift is not good at even detecting short GRBs. BAT works up to 350 keV photon energy, and short bursts, being spectrally hard, have higher peak energies. Swift only catches the low-frequency flank, often not enough to trigger the detector. While Swift has localized dozens of long GRBs, it has only seen two short ones. BATSE on CGRO found a rate of 1 in 3.

Swift most assuredly did not have to "focus" its (not very large) telescopes... It had to slew to the burst position, as the field of view of XRT and UVOT are far smaller than BAT.

To update some people: All that has been detected is the X-ray afterglow (which IS a historic first&#33;&#33;&#33;). Image subtraction via images from the RAPTOR robotic telescope reveals no optical afterglow down to R = 18.8 14 SECONDS after the GRB, and a similar process on deep Keck images gives R < 25.6 about 6 hours later. This is incredibly faint but predicted from merger theory. Afterglows happen when the ultrarelativistic jets plough into the surrounding medium, and a neutron star binary in the halo of an elliptical galaxy will have a very low density around it.

Short bursts have not been too "fast" to observe. The higher the gamma ray energy, the harder it is to detect the point in the sky where the emission is issuing from. Missions that are sensitive to short burst peak energies have almost no location sensitivity. They can say which side of the sky it came from, and that&#39;s it.

Another update on the X-ray afterglow: Chandra has probably detected it in an observation lasting 50000 seconds. A second observation will be needed to confirm if the source is fading.

Black Holes do not have a material surface, but an Event Horizon - the point of no return. Quantum physics shows that a Black Hole&#39;s entropy is coupled to the size of its surface.

There have been long GRBs detected at nearer redshifts than 050509B - but only one "classical" one, the famous GRB 030329 (at z = 0.1686).

Finally, it is "politically uncorrect" to call Swift a "NASA satellite" - it is an international project, with especially Italy having made a large contribution.

[The Near-Sighted Astronomer]

Thank you Don for giving us all an inside look at the GRB phenomenon - it helps to have knowledgeable folks such as yourself offer your input. Those of us who are science writers simply can not be expected (or can we) to know "everything about everything under the night sky" and it is not always possible to get the attention of subject matter experts - especially when emerging events demand their attention...

Chers,

jeff