Bleak

[The Warthog]

Rain since Christmas, rain for the next five days. Unseasonable warm weather, and rain, rain, rain. http://www.theweathernetwork.com/weather/cities/can/pages/CAON0638.htm

I am so depressed! AND, I have to go back to work tomorrow.

[mark RD]

not been a good Xmas for me neither, I got about half an hour setting my finderscope up and a quick view if Saturn and orion and that was it.

Mark

[CELESCOPE]

thick fog here for the las 3 days

[The Warthog]

Environment Canada is holding out the possibility of some holes in the cloud on Friday and Saturday, but they are probably lying. They also say the temps are going to drop back down to -10 or so. We suffer for our hobby.

[Sonia]

Not looking good for this week. Come thurs/fri possibly snow, snow and snow. Tomorrow may have chance of clear skies.

[stargeeza]

I have only been able to use my new scope twice since i got it - and not for more than 20 minutes between the clouds

still everyday is a wonderful day - in theory

[Astroman]

Cloudy here, too over the weekend. Bummer, had another chance for a GRB on Kitt Peak!

[The Warthog]

GRB? Qu'est-ce que c'est que ca?

[Astroman]

Gamma Ray Burst. There was one on Friday. Got a call on Saturday, totally clouded out through Monday.

[The Warthog]

You can see that? Tell me more!

[Astroman]

Kind of a long story. Don't really have time right now. But the short answer is a gamma ray burst is detected by satellite. a network of amateurs, alongside the pros, is notified and as many telescopes as are available on Earth will slew to it and take images. Sometimes there's a visual afterglow, sometimes not. Many times, the afterglow is redshifted to the x-ray, UV or below, down into the infrared. Sometimes there's nothing at all.

Quick response is best to catch optical afterglow. Professional scopes can do late-time spectroscopy and/or photometry. Being reasonably advanced as an amateur, and having attended the inaugural meetings for the network, (called GCN), and living within sight of Kitt Peak, I sometimes get to see a pro scope search for these afterglows.

You can check the Observations Reports link recently put up by Grant for one report on one burst. There's also a primer in the Learning Zone about GRB's.

[stargeeza]

Astro - do you know the incredible hulk?

well he got like that from gamma ray bursts and you might want to be careful.

[Astroman]

Actually, it was gamma radiation from inside his lab, but yeah, I'll be careful. Our atmosphere does a gret job of filtering GRB's, which is why we need satellites to detect them.

[The Warthog]

hmmmm. Thanks for the information, but I think GRBs go on the list of things I shall never see.

[Astroman]

hmmmm. Thanks for the information, but I think GRBs go on the list of things I shall never see.

No worries. I've never "seen" one either. It's purely an instrumental thing. They tend to fade to mv=19 within hours.

[Astroman]

Cloudy here, too over the weekend. Bummer, had another chance for a GRB on Kitt Peak!

Just got an email saying the GRB this Friday was a "particle incident", which means it was a (some?) high energy proton from the Sun. Now I don't feel so bad.

[stargeeza]

Hey Astro: I heard somewhere recently that a black hole eating a neutron star gave out gama ray bursts.

Is that what youre searching for ?

[Astroman]

Hey Astro: I heard somewhere recently that a black hole eating a neutron star gave out gama ray bursts.

Is that what youre searching for ?

Hey Stargeeza.

You are mostly correct. (Sorry about the delay-work and all that cr@p.) When the duration and "hardness" of GRB's are plotted on a graph, (I hear eyelids slamming shut all over the UK), they show a major trend toward two categories, "Short-soft" and "Long-hard". (Ok, no jokes here, I've already heard them.) I've previously said that GRB's can last from milliseconds to several minutes. It turns out the short ones, under about 5 seconds, tend to have energy levels quite low-from high ultraviolet to hard x-rays. Long bursts tend to be harder-from middle x-ray to upper gamma ray. "How can it be called a Gamma ray burst if it's in the UV band?", I hear you ask. The answer is, what we're talking about is the duration of the gamma rays present. GRB's radiate in all wavelengths, but only for a short time in the gamma range. Most of the rest of the energy produced is given in lower energies, like x-rays and on down through radio. The opposite follows for long bursts.

So, there are of course theories for why there's a difference. Most likely, it's a different mechanism for aech main group. Some long bursts have been shown to be associated with a supernova event. It takes some time for a star to implode, then bounce back to create the supernova "explosion". Lots of matter is turned to energy according to E=mc^2 and this is where the gamma rays come from.

Two compact objects, such as black holes and neutron stars merging could disrupt local space enough to generate gamma rays, but the mechanism is much different. It was previously thought that the two merging would not do so with enough force to turn matter to energy in sufficient quantity to release gamma radiation. However, the merger could accelerate particles to high enough energies to emit gamma rays when they collide with local gases and dust, as long as they do so in a "jet" that's facing us. This is good news and bad news. It radically lowers the total amount of energy released, but it tells us that we don't detect all the GRB's of this type, since some are bound to face the jet away from us. Food for thought.

Gotta go, but I hope this helps.

[stargeeza]

Cool ! - not that I really understand all this too well yet, but if you're talking about E=MCsq with regard to matter being coverted to energy and if that also applies to the neutron star when its "swallowed" by a black hole then based on the sheer unbelievable density of matter in a neutron star - wouldnt that be a pretty damn big release of energy?

[Astroman]

Cool ! - not that I really understand all this too well yet, but if you're talking about E=MCsq with regard to matter being coverted to energy and if that also applies to the neutron star when its "swallowed" by a black hole then based on the sheer unbelievable density of matter in a neutron star - wouldnt that be a pretty damn big release of energy?

You'd think so, but a stellar mass BH and neutron star pair, simply because of the compact, "exotic" matter involved, would be unable to overcome the gravitational forces to actually do the mass-energy conversion. Since the matter is compressed so tightly, there isn't enough room to "explode", so to speak. Fusion happens in stars because there is a balance between the gravity pressing in and the reaction blowing out. Exotic objects are too compressed to balance, that's why they're so compact. So, the gamma rays we detect are coming not from the NS-BH pair themselves, but form ejected matter interacting with the interstellar medium and are therefore less energetic than other sources.