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View Full Version : GRB 110328A - A possible beamed tidal disruption of a star by a supermassive BH!



Don Alexander
2011-Mar-31, 08:59 AM
Hey, everyone!!

Here's some hot news!! :eek: :evil:

A few days ago, a rather weird Gamma-Ray Burst occurred, very faint but very long - the trigger lasted over 1000 seconds! Swift detected an strong X-ray source which actually rose in brightness during the observation. During this, the gamma-ray detector on Swift triggered again.

Since then, this source has done crazy things in X-rays: Flares with no end! (http://www.swift.ac.uk/xrt_curves/00450158/)

Fact #1: The source lies far from the Galactic plane. Still, it was initially thought to be a Galactic transient (of a special subclass called SuperFast X-ray Transients), since the X-ray light curve behavior was roughly similar.

Fact #2: The X-rays show strong absorption which can not be of normal Galactic origin.

Fact #3: Initial optical observations revealed nothing at all, but deep imaging of this field with the Palomar Transient Factory (obtained way before this event happened) showed an optical source at about 22nd magnitude.

Fact #4: Two independent teams took spectroscopy of this source, with an extremely surprising result: It turns out to be a star-forming galaxy at redshift z=0.35, that's six billion light years away! The energy involved must be gigantic. This seemed to kill the Galactic source theory. And the X-ray light curve looks nothing like any GRB ever seen.

Fact #5: Integrated observations have revealed the source first became active several days before the first Swift trigger!!

Fact #6: Radio observations have detected a bright radio/mm source.

Possible fact: Optical and near-IR observations seem to show that is finally brightening slowly in the optical/NIR.

Whatever this is, it's totally unique.

Here's some technical analysis that seems to indicate the source is strongly beamed. (http://gcn.gsfc.nasa.gov/gcn3/11847.gcn3)

And finally, the most promising theory at this early stage (http://gcn.gsfc.nasa.gov/gcn3/11848.gcn3) seems to be that a supermassive black hole at the core of this small galaxy has swallowed and torn to shreds a passing star, a so-called "tidal disruption" event. There have been some candidates for this phenomenon, but nothing definite yet.

So we may be seeing a first here. :dance:

I'll keep you updated if there are any cool developments.

Hungry4info
2011-Mar-31, 10:50 AM
Very interesting! Thanks. Will be keeping an eye out for more information.

slang
2011-Mar-31, 12:07 PM
Awesome! I hope someone is keeping a close eye on those stars orbiting closely around Sag A*! And Swift might well be the most under appreciated orbiting observatory of all.. I wonder how much longer she will be active, and if there are plans yet for a replacement.

Ara Pacis
2011-Mar-31, 07:42 PM
I tried to find information on how bright something like that might appear to us if it happened in the center of our galaxy. No joy. But I did find a page (http://crts.caltech.edu/CSS100217.html) about an optical transient seen about a year ago that might also have been a tidal disruption event.

borman
2011-Apr-01, 01:47 AM
Tidal disruption could take place near the event horizon of a multi-solar mass black hole. The tidal force to disrupt a star is significantly interior to the event horizon of a supermassive black hole. According to Hawking, one could cross the event horizon without noticing the event. However, once past the event horizon of either a SMBH or solar mass black hole, no radiation can cross back including gama rays.

Don Alexander
2011-Apr-01, 07:36 AM
borman, you are not a star... While a SMBH such as those found at the hearts of galaxies has such small tidal forces that a human would not notice anything (in terms of tidal forces!) before crossing an event horizon, a star is of comparable size to the event horizon and will be ripped apart and form an accretion disk.

Furthermore, no one is claiming the emitted high energy radiation is coming from inside the event horizon. There is strong evidence this event created a strongly collimated beam similar to a blazar or classical GRB.

borman
2011-Apr-01, 01:37 PM
a star is of comparable size to the event horizon and will be ripped apart and form an accretion disk.



While this is true of a stellar black hole, it does not apply to SMBH. The event horizon is not "paper" thin for a SMBH to where tidal disruption occrs. This happens much deeper into the event horizon than the diameter of a star. If I am wrong about this, please present sources that support your view.

Further, if this were the case, the event would be quite common rather than rare. Every star that crosses the event horizon should produce tha same signal. Explain why the event is rare.

The scenario I prefer would address the particular situation where there was a binary where one star was very close to critical mass for supernova and the partner star that was feeding it crossed the event horizon. This could lead to the super critical mass star becoming a hyper velocity star at the moment it becomes supernova near the event horizon. This event might be rare enough to fit the rarity of the event which, at present, appears to be rather singular.

ngc3314
2011-Apr-01, 02:08 PM
Maybe the optical emission continues to brighten - I had a shot at it just before dawn with the SARA remote 1m at Kitt Peak (2 hours ago), and if that's the right source in the middle of this snippet, I make it R=20.6.

14784

slang
2011-Apr-01, 02:36 PM
While this is true of a stellar black hole, it does not apply to SMBH. The event horizon is not "paper" thin for a SMBH to where tidal disruption occrs. This happens much deeper into the event horizon than the diameter of a star. If I am wrong about this, please present sources that support your view.

FWIW: A bit of searching (http://iopscience.iop.org/1538-4357/680/1/L13/pdf/1538-4357_680_1_L13.pdf) seems to show that tidal disruption would occur inside the event horizon of a black hole of > 108 Msol. The analysis Don Alexander linked to says the data implies a black hole on the order of 106 Msol.

peteshimmon
2011-Apr-01, 07:07 PM
Two ordinary stars bumping into each other must
be quite a conflagration. Must happen sometime,
somewhere in the vast Universe. Two cores full
of gamma rays that suddenly dont have to spend
centuries diffusing out very weakened. Wonder
if anyone has modeled this?

Alternative scenario number 43!

Don Alexander
2011-Apr-02, 02:10 AM
While this is true of a stellar black hole, it does not apply to SMBH. The event horizon is not "paper" thin for a SMBH to where tidal disruption occrs. This happens much deeper into the event horizon than the diameter of a star. If I am wrong about this, please present sources that support your view.
Hills showed in 1975 in Nature that for SMBHs with a mass under 10^8 solar masses do tear up stars. What Slang said.

This probably includes a good overview of the field now: White Paper submitted to the 2010 Decadal Survey Galaxies Across Cosmic Time Science Frontiers Panel by Suvi Gezari et al. (http://arxiv.org/abs/0903.1107)


Further, if this were the case, the event would be quite common rather than rare. Every star that crosses the event horizon should produce tha same signal. Explain why the event is rare.
Because... stars very rarely come really close to central black holes??:shifty: Look at the stars orbiting the central black hole of the Milky Way, S2 approaches up to 17 light hours at perinigricon - that's about 20000 times larger than the diameter of a main sequence star. After all, there's something called orbital mechanics and conservation of angular momentum, after all. Black holes, after all, do not suck.


The scenario I prefer would address the particular situation where there was a binary where one star was very close to critical mass for supernova and the partner star that was feeding it crossed the event horizon. This could lead to the super critical mass star becoming a hyper velocity star at the moment it becomes supernova near the event horizon. This event might be rare enough to fit the rarity of the event which, at present, appears to be rather singular.
First of all, that sounds like it might happen once in an eon in the entire Hubble volume... Secondly - I do assume you mean a tight MS-WD binary leading to a Type Ia SN - the two stars will orbit so closely that they will very likely both be destroyed.

And you don't need a binary, IIRC stars get so distorted that they create something akin to a supernova anyway.


Maybe the optical emission continues to brighten - I had a shot at it just before dawn with the SARA remote 1m at Kitt Peak (2 hours ago), and if that's the right source in the middle of this snippet, I make it R=20.6.

Too bad this is not in the SDSS. Can you do a good USNO-B1 astrometry?? I looked at the DSS-2 red image, and it's possible there's a faint splotch at the position of your R = 20.6 object (this would be in good agreement with the typical DSS limits), and you may be a few arcseconds off.

Alas, no one has linked a finding chart.

@pete: Two colliding main sequence stars are, AFAIK, just going to merge and not expose their cores.

Ara Pacis
2011-Apr-02, 03:53 AM
Question: How cohesive are stars? If a star approaches the event horizon and grazes it, would the portion of the star that passed through the event horizon be sheared off while the rest of the star continues to in it's trajectory past perinigricon? What effect would the loss of mass have on the remaining star?

Also, per Pete, what is the likelihood of two stars in orbit around a SMBH might collide, is it increased due to the gravitational gradient and velocities involved? Is it possible that two may collide head on at high velocity while near perinigricon and what would the result look like?

Don Alexander
2011-Apr-02, 04:29 AM
Ara Pacis, the situation you describe would not come to pass. At least I think this would imply that most of the star passes within the innermost stable circular orbit (ISCO), which means it will just get swallowed and torn apart.

borman
2011-Apr-02, 04:41 AM
If mass transport across an event horizon is rare, then how do you account for quasar jets and AGNs? Or do these active sites show the same GRB signatures?

Don Alexander
2011-Apr-02, 07:35 AM
Those aren't stars! That's gas being accreted. And actually, blazars and GRBs have a lot of similarities.

Ara Pacis
2011-Apr-02, 07:53 AM
Ara Pacis, the situation you describe would not come to pass. At least I think this would imply that most of the star passes within the innermost stable circular orbit (ISCO), which means it will just get swallowed and torn apart.

Not sure I follow. What if it was an eccentric elliptical orbit or hyperbolic trajectory?

Don Alexander
2011-Apr-02, 08:53 AM
Doesn't matter for the elliptical orbit. It's general relativity. Anything that comes closer than the ISCO and is on a Keplerian orbit* inevitably falls into the black hole. This isn't flat space-time as we know it, it's a high-gravity environment with relativistic effects. A hyperbolic orbit should carry it out again, but don't quote me on that. Not to mention: How do you realize a hyperbolic orbit? For a test-particle free-falling from infinity, a parabolic orbit is the boundary.
Though assuming your scenario somehow comes to pass, my understanding is that the rest of the star has an easier way out. Remember this weird energy generator in which spaceships dive into a black hole, release a container full of trash and then gain energy when coming out again? Would be the same principle.
Realistically, the star will not be cohesive enough to escape mostly unscathed. It will disrupt, and a large part of it will be captured in a highly elliptical orbit, creating a tidal debris tail which will lead to multiple episodes of matter accretion on to the black hole - just what might create the X-ray flaring we are seeing for 110328A. Such processes have been simulated in detail for Neutron Star collisions with Black Holes, other NS, and White Dwarfs (e.g., Lee, Ramirez-Ruiz & van den Ven 2010, ApJ, 720, 953).

* That is, unpowered. A spacecraft with an engine would still get out.

slang
2011-Apr-02, 09:30 AM
Hills showed in 1975 in Nature that for SMBHs with a mass under 10^8 solar masses do tear up stars. What Slang said.

Thanks. I don't want to leave behind the impression that I actually know what I'm talking about though! I just figured that these Berkeley guys probably do know a bit on the subject, and wouldn't propose it if there were such an obvious argument against it. So, off to ADS (http://adsabs.harvard.edu/), search for SMBH and tidal disruption, and there it was. And if a nobody with a passing interest like me can find it..

slang
2011-Apr-02, 10:34 AM
This probably includes a good overview of the field now: White Paper submitted to the 2010 Decadal Survey Galaxies Across Cosmic Time Science Frontiers Panel by Suvi Gezari et al. (http://arxiv.org/abs/0903.1107)

That's a fascinating paper, gives some insight why we don't see lots of these events too. Are the instruments that the authors argue for, like LSST, all going to happen? 130 detections per year sounds nice!

peteshimmon
2011-Apr-02, 01:57 PM
Well I would have thought of a fast, flat
spinning disk of hot gas with a lot of
high energy radiation suddenly free.

Merge indeed! I am not talking about
custard pies!

borman
2011-Apr-02, 02:03 PM
Those aren't stars! That's gas being accreted. And actually, blazars and GRBs have a lot of similarities.

That seems to be a remarkable claim! Do you suggest that the Equivalence Principle is different for gas from stars? Or do you suggest that no stars can form where there is gas? Is there something that prevents star formation along the lines of the Toomre Criterion? Even though the Milky Way's central mass is rather quiescent, there are stars noted in the vicinity exterior to the event horizon.

StupendousMan
2011-Apr-02, 04:53 PM
The physics of accretion disks are fairly well understood in many ways, since we can observe their behavior on different length scales and at different wavelengths. Astronomers know what happens when gas forms a disk around a compact object and gradually, in a quasi-static manner, moves inwards and finally accretes. There are plenty of details that we don't yet understand, but the big picture is clear.

The physics of stars being ripped apart by a very close passage to a compact object are NOT so well understood, in large part because we haven't had the opportunity to study any events and so to test different models and ideas. This event, GRB 110328A, may be such an event; if so, it will tell us quite a lot.

Don Alexander has done the site a great service by bringing the news of this event to us and providing updates and some brief analysis. That's not part of his job -- his job is to analyze the data for his team and to write technical papers for publication. If people here make pointed remarks indicating that he doesn't know what he's talking about, it's quite possible that he'll just stop participating in BAUT -- and I wouldn't blame him.

borman
2011-Apr-02, 08:07 PM
There is nothing remarkable about accretion disks made of gas. What is remarkable is the suggestion that it is not possible for any of the gas to be collected into a star, brown dwarf, gas planet, etc. I don't see why these more massive collections of gas are forbidden. They follow the same mass geodesics that the gas does. The existence of stars observed near our galactic core, whether or not they formed there, are still there nevertheless.

Ara Pacis
2011-Apr-02, 09:34 PM
Though assuming your scenario somehow comes to pass, my understanding is that the rest of the star has an easier way out. Remember this weird energy generator in which spaceships dive into a black hole, release a container full of trash and then gain energy when coming out again? Would be the same principle.

The Oberth Effect?

Don Alexander
2011-Apr-02, 10:08 PM
@slang: I do know the Berkeley guys, one is actually a good friend of mine, and yes, they do not what they are talking about. I'll actually have to read that white paper if you consider it so interesting. ;) I just know Suvi is one of the world experts on TDFs, so it looked like a good overview paper. And I found the Hills reference in there. So I can't answer you yet if all the instruments are going to happen, but LSST will with 99.999% chance. They're building the camera and making the mirror already, afaik.

@borman: To put it lightly, you seem to be completely misunderstanding what I'm saying...

Point 1: Similarity of blazars and GRBs: Both are driven by Black Holes as central engines (one supermassive, one stellar mass). Both eject relativistic, highly collimated jets. In both cases, these jets are pointed right at us, and we see a brilliant, featureless synchrotron spectrum. The physics are very similar, even if the length and time scales are very different.

Point 2: Concerning AGN mechanics. AGNs (of which quasars and blazars are special types) shine by accreting vast amounts of gas on supermassive black holes. The physics of gas around a BH and a star coming close to a BH are generally the same, but very different in details. Gas is viscous (mean free path length, anyone), it will shed potential/orbital energy through its internal viscosity. It will heat up, radiate in emission lines (keywords Narrow-Line Region, Broad-Line Region), lose orbital energy, and drop into the BH. Unless it comes really close, a star will just orbit normally (like the well known stars around the Milky way's central BH).

As Stupendous Man points out, these two very different processes have very different levels of understanding in modern science. Gas accretion is rather simple to model, you need relatively few key parameters (chemical makeup, viscosity, radiation transport dynamics, atomic excitation levels etc.). A star being warped in a strongly curves space-time is a 3D hydrodynamics problem that needs very precise knowledge of the stellar interior, and we are still far from knowing all about this.

The issue of whether stars can form from the hot gas near a SMBH is utterly irrelevant to the topic at hand. If GRB 110328A was a TDF, the star could have come from "outside", say, from the bulge or whatever. It might have been a massive binary which was broken up and we now also have a new HVS which we will of course never detect... Just as an aside, indeed, basic theory predicts star formation will not occur near a SMBH, and there is good evidence that some of the stars very near Sgr A* DID form in situ, which is still quite a mystery. But a) not relevant to the issue at hand, as stated, and b) as always, a single unexplained fact does mean that mainstream science is an utter failure and needs to be replaced. :razz:

@Stupendous Man: First, I'm actually not participating in any work on this event right now. It's northern hemisphere, and the team I work with - and am working for right this moment, at ESO La Silla Observatory, Chile - does not have access to the NH, our detector is right here. I'm doing this because I know some people at BAUT are interested in reading about it. Second, I may actually add my little quantum to research on this event tonight, if so, I'll inform you here. I think you'll be amused by it if it works out. ;)

Oh, and finally, don't worry about me leaving. I may only post intermittently and in bursts, like the stuff I'm studying, but I've been here nigh seven years now, you aren't getting rid of me.:whistle:

Don Alexander
2011-Apr-03, 03:38 AM
This! (http://gcn.gsfc.nasa.gov/gcn3/11872.gcn3)

:D

borman
2011-Apr-03, 05:46 AM
The odd X-ray behavior is not typical for a binary inspiral. Could not a rogue stellar BH that wandered close to a neutron binary induce a premature chirp without neccessarily causing tidal disruption betray a similar signature? Beamed energy passing close to a stellar hole's horizon might suffer some Shapiro delay in addition to any time dilation due to the strong gravitational fields just outside the BH.

slang
2011-Apr-03, 07:52 AM
This! (http://gcn.gsfc.nasa.gov/gcn3/11872.gcn3)

Hehe. Bringing spam to astronomical levels! :)

grapes
2011-Apr-03, 08:30 AM
This! (http://gcn.gsfc.nasa.gov/gcn3/11872.gcn3)

:D"This GCN resulted from a collaboration initiated by the BAUTforum."

Hmmm...

Don Alexander
2011-Apr-05, 10:06 PM
The event - and BAUTforum - have made it to the Bad Astronomer's blog!! (http://blogs.discovermagazine.com/badastronomy/2011/04/05/astronomers-may-have-witnessed-a-star-torn-apart-by-a-black-hole/)

Ara Pacis
2011-Apr-05, 11:07 PM
The event - and BAUTforum - have made it to the Bad Astronomer's blog!! (http://blogs.discovermagazine.com/badastronomy/2011/04/05/astronomers-may-have-witnessed-a-star-torn-apart-by-a-black-hole/)

I have a question about something the BA wrote in that blog:

The material swirled around the black hole, forming a small and temporary accretion disk. Observations indicate that for a short time, two beams of matter and energy called jets erupted from the doomed star, and it was the flash of tremendous energy from this that triggered Swift, and a flurry of observations from other telescopes cascaded from that.Were the beams emitted from the star or from the accretion disk of the black hole?

slang
2011-Apr-06, 12:03 AM
Were the beams emitted from the star or from the accretion disk of the black hole?

Don Alexander answered that question in comment #31 (http://blogs.discovermagazine.com/badastronomy/2011/04/05/astronomers-may-have-witnessed-a-star-torn-apart-by-a-black-hole/#comment-374116):


It’s definitely the BH which is launching the jets, but the magnetic fields come from the accreted material and thus, in essence, from the star.

It's pretty cool to have the forum mentioned there, maybe it'll end up in a published paper somewhere, and all of us can be proud of having a citation! (Even if we have to share it between 84,161 members). *wanders off in a proud glow of glory*

Don Alexander
2011-Apr-06, 12:32 AM
Actually, the BA is a bit wrong there...

The event is ongoing, the radiation that triggered Swift was not even the most powerful outburst, that one occurred about a day later.

It's definitely the black hole launching the jets, probably via the Blandford-Sznajek effect, where magnetic fields trapped in the inspiraling plasma get twisted up (static field lines of a magnetic field actually can pass through the event horizon) and can create a "magnetic tower" which funnels the jets.

antoniseb
2011-Apr-06, 09:43 AM
The event - and BAUTforum - have made it to the Bad Astronomer's blog!! (http://blogs.discovermagazine.com/badastronomy/2011/04/05/astronomers-may-have-witnessed-a-star-torn-apart-by-a-black-hole/)

Very cool! Thanks for bringing it here.

Ara Pacis
2011-Apr-06, 07:49 PM
Actually, the BA is a bit wrong there...

The event is ongoing, the radiation that triggered Swift was not even the most powerful outburst, that one occurred about a day later.

It's definitely the black hole launching the jets, probably via the Blandford-Sznajek effect, where magnetic fields trapped in the inspiraling plasma get twisted up (static field lines of a magnetic field actually can pass through the event horizon) and can create a "magnetic tower" which funnels the jets.

Thanks, I'm just trying to visualize it and wasn't sure if the jets come from the pole of the BH, if it's spinning and has a pole, or if the beam is from a "pole". which is merely a location perpendicular to the plane of the accretion disk.

Alternately, I was thinking that if the BA was right that it came from the star, that the beam came from the star's poles (axis of rotation) as it was disrupted... or if the beam came from the axis of elongation, and wondered if either of them might make the beam pan across the sky as the material spun into the BH (kinda like a flashing/rotating police light). I know, it probably sounds silly.

publiusr
2011-Apr-06, 10:09 PM
Elsewhere, there were talks of "laser stars" formed by asteroids falling into a sun.


I have often wondered about extrasolar foci sweeping like searchlights through the cosmos. Suppose a star falls behind a BH. Would not the BH act like a lens and concentrate a stars light. All the talk about telescopes to the solar foci made me wonder if a form of Space based solar power might be had even at great distances from stars--you just have to have a passive structure 'stand' in the right spot.

ngc3314
2011-Apr-07, 02:03 PM
Just out - the HST image (http://www.spacetelescope.org/announcements/ann1108/), taken a mere three days ago. As I stare at the released JPEG, there's an elliptical-looking galaxy there, but it's hard to tell more by inspection.

neilzero
2011-Apr-07, 04:35 PM
A star closer than a light year from a black hole would produce concentrated energy at a rather small focal point. The focal point moves in a curved path, so a colony would need lots of energy to stay at the focal point, perhaps more than could be harvested, except in rare scenarios. More than a light year would be too puny an energy source to be practical. The accretion disc of a super massive black hole would be dangerous out to about one light year from the black hole, so a ten solar mass black hole would possibly be better for harvesting energy at the focal point. Can some one give us an idea how far the focal point is from a ten solar mass black hole? Assume a one solar mass star 1/2 light year from the black hole in a circular orbit that is at a 45 degree angle with respect to the accretion disc which is puny. Yes, some accretion discs are puny. Neil

ngc3314
2011-Apr-07, 06:22 PM
Gravitational lensing by what is effectively a point mass doesn't really have a focal point, but a focal line - each point on that line receives the energy through a ring around the lens, with that ring moving outwards as one looks from farther away from it along the line. There is a minimum distance for strong lensing (i.e. multiple images or the theoretical Einstein ring) - for a star, the light rays have to miss the photosphere.

Don Alexander
2011-Apr-07, 09:55 PM
It actually took me quite a long time to track down the info that the HST image "was taken in visible light". So I assume it's the F606W image. which is kind of weird, as the description in the GCN was that the IR F160W image was dominated by a bright point source, whereas the F606W image showed the extended galaxy. That doesn't really look so extended to me...

Also, I'm highly disappointed. UT now features the story... and all it is is a copy/paste of the NASA press release. The whole story about the involvement of BAUT that the BA wrote about has gone completely missing. :(

Not to mention that the blogosphere is obviously nothing but a mirror maze... A blog linked in the comments of the BA's post writes: "And interesting side note; astronomers established a thread to track GRBs in another pair of science/astronomy blogs that you might have heard of, the Bad Astronomy/Universe Today bulletin board. Much of the initial discovery and follow-up action occurred here, a forum worth following. And they say, “What good is blogging…”"

Which is, of course, complete bull...

Tensor
2011-Apr-07, 10:07 PM
Not to mention that the blogosphere is obviously nothing but a mirror maze... A blog linked in the comments of the BA#s post writes: "And interesting side note; astronomers established a thread to track GRBs in another pair of science/astronomy blogs that you might have heard of, the Bad Astronomy/Universe Today bulletin board. Much of the initial discovery and follow-up action occurred here, a forum worth following. And they say, “What good is blogging…”"

Which is, of course, complete bull...

You really didn't expect the blogosphere to get it right, did you Don? :wall:Well, except for a few who actually pay attention....:whistle: BTW, good job, Bill, Don, Adria, and Dieter.

slang
2011-Apr-07, 10:50 PM
Also, I'm highly disappointed. UT now features the story... and all it is is a copy/paste of the NASA press release. The whole story about the involvement of BAUT that the BA wrote about has gone completely missing. :(

But at least there's a very "interesting" EU discussion! I thought UT had a comments policy which prohibited the posting of those kinds of comments..

Don Alexander
2011-Apr-08, 05:21 AM
I always thought BAUTforum had a policy on not discussing ATM ideas in the astronomy part of the forum, too...

Swift
2011-Apr-08, 01:28 PM
I always thought BAUTforum had a policy on not discussing ATM ideas in the astronomy part of the forum, too...
It absolutely does. Is there some ATM here that you are concerned about - if so, please report the post.

(mod hat off)
Oh, and nice work and a fascinating discussion.

Cougar
2011-Apr-08, 01:35 PM
Some blog: ...the Bad Astronomy/Universe Today bulletin board... Much of the initial discovery and follow-up action occurred here, a forum worth following.

D.A.: Which is, of course, complete bull...

Except for the "worth following" part. :)

Don Alexander
2011-Apr-09, 01:41 AM
Just to give an update:

A radio observation has been done with the VLBA+Effelsberg, they detect the source at very high significance, and give a position to the precision of 0.5 MILLIarcseconds.

This position is in full agreement with the Chandra X-ray (500 marcsec), HST optical (100 marcsec) and other radio positions, and also with the galaxy nucleus.

Furthermore, the source size is unresolved down to ~ 1 marcsec, which would be entirely expected. It remains a strong, flaring X-ray source.

publiusr
2011-Apr-09, 07:56 PM
Gravitational lensing by what is effectively a point mass doesn't really have a focal point, but a focal line - each point on that line receives the energy through a ring around the lens, with that ring moving outwards as one looks from farther away from it along the line. There is a minimum distance for strong lensing (i.e. multiple images or the theoretical Einstein ring) - for a star, the light rays have to miss the photosphere.


The only reason I made mention of that and the idea of laser stars was as a possible explanation to any unusual optical artifacts later scopes might see sweeping around.

Don Alexander
2011-Apr-14, 01:58 AM
The first paper on the event is out... (http://arxiv.org/abs/1104.2528)
And it immediately reminded me of these blatant, cheap Disney/Dreamworks ripoffs...

Who ARE these two guys, even??

Things they should be told:

- GCNs are people too! I mean, citeable publications. They are going to get flak like hell for not actually putting them in the reference list.
- There is something called XRT PC data. You're allowed to use it too!!
- Maybe you should make short version of the title...

And finally: Blatant ripoff of the Campana and Bloom GCNs without ever correctly acknowledging them.

And for A&A: It's \titlerunning, not \titilerunning.

Ouch.

StupendousMan
2011-Apr-14, 12:39 PM
From this page

http://www.insapvii.org/posters/UlissesBarresdeAlmeida.html

one can conclude that U. Barres de Almeida is a brand new Ph.D. who has just moved from Durham -- where he worked on HESS -- to Max Planck.

And from this page

http://www.fisica.uniud.it/~deangeli/

we see that Alessandro de Angelis is an established high-energy particle physicist who is on leave from the University of Udine, perhaps taking a sabbatical to have some fun doing research at Max Planck.

One might guess that Dr. Barres de Almeida, having spent time working with the HESS collaboration, would be familiar with the conventions of the astronomical community dealing with giving credit where credit is due.

publiusr
2011-Apr-16, 05:45 PM
Gravitational lensing by what is effectively a point mass doesn't really have a focal point, but a focal line - each point on that line receives the energy through a ring around the lens, with that ring moving outwards as one looks from farther away from it along the line. There is a minimum distance for strong lensing (i.e. multiple images or the theoretical Einstein ring) - for a star, the light rays have to miss the photosphere.

I wonder if this effect can be used for beamed energy propulsion as well as communication. Dyson dots gather energy, beam it to the opposite side of the sun from the solar sail, then beam it back, passing by the sun, to the solar sail. In this way the solar sail uses direct pressure from sunlight at first, and when it goes extra solar, ride the beam from behind.

On topic: On page 14 of the March 12 2011 issue of Science News is the report on how Black Holes put a spin on light, as reported in the Feb 15 online version of Nature Physics.

Also in the March 12 issue of Science News (on page 20) is an article on vortices: http://complex.umd.edu
Hydrogen ice particles in supercooled helium look like solar eruptions. Something to think about

banquo's_bumble_puppy
2011-Apr-18, 05:55 PM
Two ordinary stars bumping into each other must
be quite a conflagration. Must happen sometime,
somewhere in the vast Universe. Two cores full
of gamma rays that suddenly dont have to spend
centuries diffusing out very weakened. Wonder
if anyone has modeled this?

Alternative scenario number 43!

sounds like a Haiku...sorry OT

publiusr
2011-Apr-18, 11:00 PM
According to a recent article in Science News, there was talk about a wormhole star. Wonder how that might look if stripped
http://onlinelibrary.wiley.com/doi/10.1002/scin.5591790706/abstract

rchoppin
2011-Apr-19, 02:08 PM
Given that we're seeing the same event generating radiation across a wide frequency spectrum, is it possible to correlate across
these frequencies to give a second distance measurement based on the differences in propagation to compare to values derived
from red shift?

ngc3314
2011-Apr-19, 03:41 PM
Given that we're seeing the same event generating radiation across a wide frequency spectrum, is it possible to correlate across
these frequencies to give a second distance measurement based on the differences in propagation to compare to values derived
from red shift?

Only in the broad sense that propagation delays cannot be large than the whole range of lag times for peak flux. Our ignorance of the detailed generating processes is so vast that anything beyond that barely goes beyond conjecture. Not to mention that our detailed knowledge of propagation details in intergalactic space is also very sketchy - as far as I can tell, it's confined to dispersion measures for pulsars in the Magellanic Clouds, where effects of the interstellar media in both host and foreground galaxies dominate by far. (Well, OK, we know from supernovae and variable stars that differential propagation delays in the optical and radio can't be weeks or more, except for special cases such as multipath gravitational lensing).

deangeli97
2011-Apr-19, 10:49 PM
arXiv:1104.2528v1 [astro-ph.HE]

Enhanced emission from GRB 110328A could be evidence for tidal disruption of a star
Ulisses Barres de Almeida, Alessandro De Angelis
(Submitted on 13 Apr 2011)

On March 28, Swift's Burst Alert Telescope discovered a source in the constellation Draco when it erupted in a series of X-ray blasts. The explosion, catalogued as gamma-ray burst (GRB) 110328A, repeatedly flared in the following days, making the interpretation of the event as a GRB unlikely. Here we suggest that the event could be due to the tidal disruption of a star that approaches the pericentric distance of a black hole, and we use this fact to derive bounds on the physical characteristics of such system, based on the variability timescales and energetics of the observed X-ray emission.

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Extragalactic Astrophysics (astro-ph.CO)

deangeli97
2011-Apr-20, 06:03 AM
Hi

We did not quote properly the GCN in the bibliography (although we quoted them in the text) due to inexperience; now we learned we should do it, and we'll do it replicating them in the list of the references, and adding a couple of them, for the revised version when we'll get comments from the referees.

We apologized already to the people who wrote us in this sense, signaling their GCN. Please write us if you have suggestion/comments.

It seems to us that our paper has something more than the GCN, though :)

Alessandro De Angelis


The first paper on the event is out... (http://arxiv.org/abs/1104.2528)
And it immediately reminded me of these blatant, cheap Disney/Dreamworks ripoffs...

Who ARE these two guys, even??

Things they should be told:

- GCNs are people too! I mean, citeable publications. They are going to get flak like hell for not actually putting them in the reference list.
- There is something called XRT PC data. You're allowed to use it too!!
- Maybe you should make short version of the title...

And finally: Blatant ripoff of the Campana and Bloom GCNs without ever correctly acknowledging them.

And for A&A: It's \titlerunning, not \titilerunning.

Ouch.

Don Alexander
2011-Apr-20, 07:26 AM
deangeli97, I posted a link to that paper already on the 14th. :P

Anyway, THE two papers on this event, submitted to Science, appeared on astro-ph yesterday. Enjoy!!

An extremely luminous panchromatic outburst from the nucleus of a distant galaxy (http://arxiv.org/abs/1104.3356) by A. J. Levan et al.

A relativistic jetted outburst from a massive black hole fed by a tidally disrupted star (http://arxiv.org/abs/1104.3257) by J. S. Bloom et al.

And here's something, uhhh, less mainstream:

Superlong GRB 110328A: generation in the collapsing star cluster (http://arxiv.org/abs/1104.3290) by V. I. Dokuchaev & Yu. N. Eroshenko

loglo
2011-Apr-20, 10:28 AM
deangeli97, I posted a link to that paper already on the 14th. :P

Anyway, THE two papers on this event, submitted to Science, appeared on astro-ph yesterday. Enjoy!!

An extremely luminous panchromatic outburst from the nucleus of a distant galaxy (http://arxiv.org/abs/1104.3356) by A. J. Levan et al.

A relativistic jetted outburst from a massive black hole fed by a tidally disrupted star (http://arxiv.org/abs/1104.3257) by J. S. Bloom et al.

And here's something, uhhh, less mainstream:

Superlong GRB 110328A: generation in the collapsing star cluster (http://arxiv.org/abs/1104.3290) by V. I. Dokuchaev & Yu. N. Eroshenko

I momentarily misread the title of first paper as "pangalactic" not panchromatic and was instantly reminded of the Douglas Adam drink from the Hitchhiker's Guide, the Pangalactic Gargle Blaster. Then I realised ... that would be a really good name for this type of event. :) Well, it beats "tidal disruption" event anyhow.

Don Alexander
2011-Apr-27, 06:32 AM
Like, whoa! :eek:

The Swift team has submitted their own paper on this event to Nature!! (http://arxiv.org/abs/1104.4787)

StupendousMan
2011-Apr-27, 12:14 PM
Aw, gosh, why did the authors place this sentence at the end of their abstract?


Such an event in the massive black hole at the centre of our Milky Way galaxy could strongly ionize the upper atmosphere of the Earth, if beamed towards us.

Is _every_ paper in astrophysics going to have to make a connection to "ending life on Earth" or "finding life on other planets?" Can't people study stars or galaxies for their own sakes anymore?
</curmudgeon>

Swift
2011-Apr-27, 01:11 PM
Aw, gosh, why did the authors place this sentence at the end of their abstract?

Is _every_ paper in astrophysics going to have to make a connection to "ending life on Earth" or "finding life on other planets?" Can't people study stars or galaxies for their own sakes anymore?
</curmudgeon>
If you're going to put that in, you might as well add "... as predicted by the Mayans". :p

ngc3314
2011-Apr-27, 02:07 PM
If you're going to put that in, you might as well add "... as predicted by the Mayans". :p

Hey, what a great idea! I think there's just time for me to sneak that in to a couple of AGN papers in progress...

publiusr
2011-Apr-30, 07:07 PM
Might be the only way to get people interested. All the programs on space have to have something exploding, too.
Then too, Ben Stein could make Cephid variables ho-hum. Win Ben Steins nebulae.

slang
2011-Jun-17, 11:13 PM
We at BAUT already knew, now the world finds out. BBC News: Powerful cosmic blast as black hole shreds star (http://www.bbc.co.uk/news/science-environment-13783877)


Researchers suspect that the star wandered too close to the black hole and got sucked in by the huge gravitational forces.

The star's final moments sent a flash of radiation hurtling towards Earth.

Duck!

mojocujo
2011-Aug-20, 11:06 PM
I think it is likely that very little mass accreted onto the smbh. Extant to the event horizon there will be a fission horizon a fusion gap and qgp floor. A hard evolving high pressure horizon with infalling matter being forced to the poles and ejecting a particle stream at relativistic speeds.
[ QUOTE=Don Alexander;1881557]Like, whoa! :eek:

The Swift team has submitted their own paper on this event to Nature!! (http://arxiv.org/abs/1104.4787)[/QUOTE]

loglo
2011-Aug-21, 02:03 PM
Hi mojocujo,
Welcome to BAUT.

Could you elaborate please?

What is a fission horizon?
What is a fusion gap?
What is a QGP floor?
How do these prevent accretion onto the BH?

mojocujo
2011-Aug-26, 11:54 PM
I will. I guess it was a little too simplistic.

mojocujo
2011-Aug-28, 09:19 PM
Grb 112803a provides a unique insight into the central engines of GRB's. There are certain deductions that can be made for 110328a that likely apply to all GRB central engines. I have long suspected that we had horizons that I was unaware of. I say this since I am not a physicist.
Classical physics assuming planck length would require two additional horizons, the first being the fission horizon where the graviatational energy as well as the shear effect of frame dragging results in an explosive effect by rending the atoms reaching this horizon releasing energy in a shaped charge effect toward the smbh.
Matter accreting below this horizon are protons, neutrons and electrons. This I call the fusion gap where the R process occurs.
Then we have the QGP floor where the protons and neutrons are rendered to a quark gluon plasma by gravity and frame dragging releasing energy at an unprecedented rate.
As a result any bh but in this case the smbh at the equator we see the accretion disc thin to a quantum level but as these horizons are reached the high pressure forces matter accreting off the equator of the smbh. Due to the two horizons this occurs relativistically to the poles of the smbh.
As a result of the two horizons matter accreted is forced to the poles and ejected as a paricle beam. The free electrons creating a synchrontron emission mildly at the equator but at the poles a very strong emission.
The fusion gap also dependant on the two horizons will relativistically emit a plasma of heavy elements created in this in high energy high pressure region.
This process would appear dominant in all GRB and act as the central engine in all GRB.

mojocujo
2011-Aug-29, 04:11 AM
He fission qgp horizons will only exist if sufficiet matter is being accreted.

Shaula
2011-Aug-29, 06:26 AM
Citations? Pretty sure the energies you are talking for the QGP horizon about are not reached outside the event horizon. Never read about anything like the fusion or fission horizons either.

The jets are normally attributed to magnetic or angular momentum type effects. Do you have any references for what you are saying? If it is mainstream I'd be interested to read up on it as it seems to be something I have missed. If not, wrong forum.

mojocujo
2011-Aug-29, 07:57 AM
Just an abstract for the swift conference. Don't know of any previous papers! I have not been invited to any conferences except the calcutta conference in 2007! It is important to note that without sufficient infalling matter the ffq horizons decay and accretions occurs to the smbh!

mojocujo
2011-Aug-30, 01:27 AM
I didn't mention angular momemtum but frame dragging can't occur without angular momentum of the smbh. I assume the angular momentum to be close to c.


Citations? Pretty sure the energies you are talking for the QGP horizon about are not reached outside the event horizon. Never read about anything like the fusion or fission horizons either.

The jets are normally attributed to magnetic or angular momentum type effects. Do you have any references for what you are saying? If it is mainstream I'd be interested to read up on it as it seems to be something I have missed. If not, wrong forum.

Shaula
2011-Aug-30, 04:56 AM
C is a speed. Angular momentum doesn't have the units of velocity. So you'd be assuming nonsense.

If this is not peer reviewed then ideally it should be presented and defended in the ATM section. If it is then citations ought to be available when requested.

mojocujo
2011-Aug-30, 06:15 PM
What is the ATM section? Should I have said the angular momentum was relativistic?


C is a speed. Angular momentum doesn't have the units of velocity. So you'd be assuming nonsense.

If this is not peer reviewed then ideally it should be presented and defended in the ATM section. If it is then citations ought to be available when requested.

mojocujo
2011-Aug-31, 01:07 AM
I am not a physicist Shaula if you can explain it better please do. Just seeing this grb with all its' additional properties made me think on the way to my real job that this process would be a simplistic way to describe the central engine of grb and xray jets. If i describe it wrongly I am sorry I have never spent an hour in a physics classroom. Nor am I a engineer. If you can say it correctly please correct me. Or in the alternative if it becomes plausible write a paper and either include or exclude me. This forum was started regarding the 110328a grb and was trying describe how it worked how can that be the wrong forum?

pzkpfw
2011-Aug-31, 01:54 AM
I am not a physicist Shaula if you can explain it better please do. Just seeing this grb with all its' additional properties made me think on the way to my real job that this process would be a simplistic way to describe the central engine of grb and xray jets. If i describe it wrongly I am sorry I have never spent an hour in a physics classroom. Nor am I a engineer. If you can say it correctly please correct me. Or in the alternative if it becomes plausible write a paper and either include or exclude me. This forum was started regarding the 110328a grb and was trying describe how it worked how can that be the wrong forum?

(Please do not respond to this in-thread).

The issue is that speculations or alternative proposals should be in the ATM sub-forum, found here: [ http://www.bautforum.com/forumdisplay.php/17-Against-the-Mainstream ].

"ATM" means "Against The Mainstream".

Alternatively, you can ask questions in the Q&A (Questions and Answers) sub-forum.


(P.S. this set of posts is called a "thread", not a "forum". A bunch of threads together under some heading is called a "forum", or "sub-forum" or "section" (it varies). This website in general is called a "forum".)

mojocujo
2011-Aug-31, 06:16 AM
Unfortunatly do a google search for grb cenral engine you won't find a good explanation I gave one that seems plausible. Simple elegant provides a means to provide the energies observed..........Against the mainstream?? I have been looking for papers for years with an explanation of the central engine and this one happens. Please do a google search you will probably get a link to this forum!


(Please do not respond to this in-thread).

The issue is that speculations or alternative proposals should be in the ATM sub-forum, found here: [ http://www.bautforum.com/forumdisplay.php/17-Against-the-Mainstream ].

"ATM" means "Against The Mainstream".

Alternatively, you can ask questions in the Q&A (Questions and Answers) sub-forum.


(P.S. this set of posts is called a "thread", not a "forum". A bunch of threads together under some heading is called a "forum", or "sub-forum" or "section" (it varies). This website in general is called a "forum".)