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Single vs Double hot spots for BH Jets? (e.g. Pictor A)
Example object, Pictor A
http://chandra.harvard.edu/photo/2016/pictora/ in particular, the x ray Chandra image: http://chandra.harvard.edu/photo/201...ctora_xray.jpg Question 1: Has anyone proposed any model that describes a mechanism to produce a single BH jet, or, alternating BH jets (e.g. the jet shoots one way for a while, then the other way for a while, alternating back and forth)? Question 2: *IF* there are 2 jets active, and both are active for the same duration, then wouldn't we observe a pair of Hot Spots of the same size? We clearly see a hot spot on the right side, but there isn't one on the left side (there are other sources, but they are all smaller in angular size, and there isn't a source at the location of the protrusion where the jet recently had been.) If one is to contend that the jet wanders, and that's why we don't see the counter hot spot because it recently moved from where the optical / radio extension is, then the same must be true for the primary jet coming toward us.............is there an example of a primary jet coming toward us *without* a hot spot? Question 3: If the primary jet on the right side were to turn off at time 0, how long would it take for the heated x ray gas to cool off so that we no longer saw a hot spot? tens, thousands, millions of years? I have no sense on time scale for this intergalactic gas cooling process so any guesses appreciated. The point is, if the counter jet hot spot has cooled due to motion, the cooling time is indicative of the jet pointing change velocity if there is no observable hot spot. But the same must then apply to all of the many similar objects that do not show counter jet hot spots. Am I missing something important here? What is it? Thanks, rt |
#2
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Single vs Double hot spots for BH Jets? (e.g. Pictor A)
On 19/01/2017 03:53, wrote:
Example object, Pictor A http://chandra.harvard.edu/photo/2016/pictora/ in particular, the x ray Chandra image: http://chandra.harvard.edu/photo/201...ctora_xray.jpg Question 1: Has anyone proposed any model that describes a mechanism to produce a single BH jet, or, alternating BH jets (e.g. the jet shoots one way for a while, then the other way for a while, alternating back and forth)? The only way I could see that there might be a significant asymmetry is when a BH has run out of matter to consume and the last gulp wasn't evenly distributed so that one pole runs out before the other. This would be quite rare and only during the transition to quiescence. Otherwise for an active BH I think the standard model pretty much requires that the jets are symmetric. See for example: http://ned.ipac.caltech.edu/level5/Carilli/Car2_1.html And go back to contents for a nice review of Cygnus A. However time of flight considerations could mean that there hasn't yet been time for the light from the more distant hotspot of two to reach us in the case of a source where the jet is almost pointing at us. Question 2: *IF* there are 2 jets active, and both are active for the same duration, then wouldn't we observe a pair of Hot Spots of the same size? We clearly see a hot spot on the right side, but there isn't one on the left side (there are other sources, but they are all smaller in angular size, and there isn't a source at the location of the protrusion where the jet recently had been.) The main reasons for not seeing the other hotspot I can think of are either relativistic beaming making the one coming towards us appear very much brighter or something in the way (or a bit of both). The angle the jet makes with our line of sight affects how they look. If one is to contend that the jet wanders, and that's why we don't see the counter hot spot because it recently moved from where the optical / radio extension is, then the same must be true for the primary jet coming toward us.............is there an example of a primary jet coming toward us *without* a hot spot? I suspect relativistic beaming makes this very unlikely. Question 3: If the primary jet on the right side were to turn off at time 0, how long would it take for the heated x ray gas to cool off so that we no longer saw a hot spot? tens, thousands, millions of years? I have no sense on time scale for this intergalactic gas cooling process so any guesses appreciated. 3C452 sort of answers this slightly in that there are faint relics of much older radio lobes seen at 325MHz but not at GHz and some distance far out from the modern hotspots and brighter lobes associated with them. See for example: http://iopscience.iop.org/article/10...8205/765/1/L11 As high resolution high dynamic range aperture synthesis images become available at lower frequencies I expect more of these will be found. The point is, if the counter jet hot spot has cooled due to motion, the cooling time is indicative of the jet pointing change velocity if there is no observable hot spot. But the same must then apply to all of the many similar objects that do not show counter jet hot spots. Am I missing something important here? What is it? One thing is that the light travel time to us from the furthest hotspot is significantly longer than for the nearest one. So we are seeing the two hotspots being illuminated by beams emitted from the BH at two quite different times. If the beam wasn't steady then it is possible that at the time we see the more distant spot the beam was quiescent. I am out of date on some of this stuff but the fundamentals probably haven't changed. Corrections and refinements welcomed. BTW to the OP it would help point you at the right material if you gave some idea of the level of mathematics and physics that you understand. -- Regards, Martin Brown |
#3
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Single vs Double hot spots for BH Jets? (e.g. Pictor A)
On Friday, January 20, 2017 at 8:44:02 AM UTC-8, Martin Brown wrote:
On 19/01/2017 03:53, wrote: Example object, Pictor A http://chandra.harvard.edu/photo/2016/pictora/ in particular, the x ray Chandra image: http://chandra.harvard.edu/photo/201...ctora_xray.jpg Question 1: Has anyone proposed any model that describes a mechanism to produce a single BH jet, or, alternating BH jets (e.g. the jet shoots one way for a while, then the other way for a while, alternating back and forth)? However time of flight considerations could mean that there hasn't yet been time for the light from the more distant hotspot of two to reach us= in the case of a source where the jet is almost pointing at us. Regards, Martin Brown [Moderator's note: Please send non-encoded short lines. Hit RETURN after 70 characters if your software shows you line breaks but doesn't send them. -P.H.] Thanks and good point, time of flight, as the jets are million light year l= ong, we would see the jet toward us first, and the jet away from us second,= with perhaps 2 million years to who knows, 10 million years from jet emerg= ence to our current view which could be anywhere along that entire evolutio= n. The thing is, I've seen a lot of pictures, but it's always presented th= at the hot spot is coming toward us. My point is that there ought to be 50% of these objects where the hot spot = we observe is the hot spot of the receding jet. I understand beaming and h= ow we might not observe the receding jet vs the jet coming at us. But, the= hot spot should be relatively stationary and glowing, so that we see both = hot spots if there are two to be seen. And if they shut down so, we ought = to see half of them with the receding hot spot and no observed jet because = it is receding. I don't recall seeing a hot spot without a jet feeding it such that the hot= spot is supposed to be the receding hot spot, and no jet is observed due t= o alignment. Is there an image of this out there that anyone knows? rt |
#5
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Single vs Double hot spots for BH Jets? (e.g. Pictor A)
@ross.t: there's a citizen science (crowd sourcing) project which
is very much related to your questions, in a general sense, Radio Galaxy Zoo. Main page: https://radio.galaxyzoo.org/#/ Discussion forum: https://radiotalk.galaxyzoo.org/ To repeat what's already been said, to be visible as radio lobes/hotspots/jets/etc, the back-to-back relativistic jets created near the SMBH in the nucleus have to get through, and be seen through, first the ISM of the galaxy, then the IGM between galaxies. It's nice if both are homogeneous, but often they aren't. And there's relative motion too, producing such things as 'narrow angle tails' and 'wide angle tails'. On timescales: there's a class of radio sources called "giants", lobe-to-lobe distances as great as 5 Mpc. There are also some which are "restarted", in at least one case, at least three times.=20 On single vs double jets, there's a rare class of object called "hybrid" or "HyMoRS" (Hybrid Morphology Radio Sources), where the radio morphology of one side (jet/lobe) is extremely different from that of the other. |
#6
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Single vs Double hot spots for BH Jets? (e.g. Pictor A)
On Tuesday, January 24, 2017 at 9:06:13 AM UTC-8, Martin Brown wrote:
On 23/01/2017 22:45, wrote: On Friday, January 20, 2017 at 8:44:02 AM UTC-8, Martin Brown wrote: Thanks for the links and comments. Question: Is there evidence that material (gas and or stars) is "raining" back down onto galaxies where the radio jets appear to be old and fading? In other words, suppose FR I galaxies with intense jets observed near the central engine are "young" and FR II galaxies with wider opening angles are "older", meaning, it's been longer since the initial launch of the radio jets. then, objects with fading radio lobes, and no central jets, are taken to be older still. (does this classification fit what people think?.....and) Is there any evidence for material (gas and or stars) raining back down onto the galaxies? And if so, does it fit that the above sequence holds, with the matter raining back down being most associated with the "oldest" systems, ie, longest time since initial jet launch? In other words, if excess angular momentum is what gives rise to the jets, then, shutting down that angular momentum would kill the jets. If matter is ejected along the polar axis, and then that material later rains down onto the galaxy, the angular momentum of the "rain" would be orthogonal to the angular momentum of the jets, thus, shutting down the jets. Is this logic in keeping with consensus thinking? Thanks, Ross [[Mod. note -- I am not an expert in this area, but (following the standard model of jet production from accretion onto a supermassive central black hole): 1. The angular momentum which gives rise to the jet would be that of the accretion disk very close to the central supermassive BH (say within no more than 100 Schwarzschild radia). The jets would come out just about radially (along the BH's rotation axis, perpendicular to the accretion disk), and so carry little net angular momentum. (Recall that purely radial motion has zero angular momentum.) 2. I think jets usually start out going much faster than a galaxy's (or even a galaxy cluster's) escape velocity. The jet then plows into the interstellar medium in the galaxy, but I personally have no idea of how much mass or linear/angular momentum ever returns to the vicinity of the central BH. Is there enough to be a significant influence on the accretion disk, magnetic field, or the BH's mass/spin? Hopefully someone who knows the relevant modelling can provide better-informed answers than my educated-guesses. -- jt]] |
#7
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Single vs Double hot spots for BH Jets? (e.g. Pictor A)
On 06/02/2017 05:56, wrote:
On Tuesday, January 24, 2017 at 9:06:13 AM UTC-8, Martin Brown wrote: On 23/01/2017 22:45, wrote: On Friday, January 20, 2017 at 8:44:02 AM UTC-8, Martin Brown wrote: Thanks for the links and comments. Question: Is there evidence that material (gas and or stars) is "raining" back down onto galaxies where the radio jets appear to be old and fading? I shouldn't expect so. The momentum of the jet carries the shocked material along with it away from the galaxy probably forever. There will be some backwash but it won't have anything like the velocity to carry it back to the core. Rough indications from the shapes of radio lobes in powerful FR II sources are perhaps 1/3 the way back at most. In other words, suppose FR I galaxies with intense jets observed near the central engine are "young" and FR II galaxies with wider opening angles are "older", meaning, it's been longer since the initial launch of the radio jets. There is a significant difference between the power of the central engine in FR I and FR II galaxies with the latter being pretty much the biggest and most powerful things in the universe. Whilst I would think it possible that an FR I might sometimes evolve into an FR II by either excessive feeding or BH merger. I don't think any would go the other way. A discussion of their characteristics and modern interpretation is online he https://ned.ipac.caltech.edu/level5/..._fanaroff.html then, objects with fading radio lobes, and no central jets, are taken to be older still. (does this classification fit what people think?.....and) Is there any evidence for material (gas and or stars) raining back down onto the galaxies? And if so, does it fit that the above sequence holds, with the matter raining back down being most associated with the "oldest" systems, ie, longest time since initial jet launch? I get the feeling you are thinking about the jets as fountains rather than as astrophysical things. The backwash does fill up some of the void punched out by the jet but I can't see if has much scope for raining down onto the galaxy. It is way too tenuous for that. One of the early incorrect models for double radio galaxies were that the lobes were effectively plumes of less dense hot plasma rising buoyantly in the intergalactic medium. Like hot air does on Earth. In other words, if excess angular momentum is what gives rise to the jets, then, shutting down that angular momentum would kill the jets. If matter is ejected along the polar axis, and then that material later rains down onto the galaxy, the angular momentum of the "rain" would be orthogonal to the angular momentum of the jets, thus, shutting down the jets. It isn't excess angular momentum causing the jets it is the very fact that the BH is spinning and magnetised. This provides a way to extract a huge amount of rest mass energy out of infalling matter some of which gets converted to jets escaping at the *poles* like aurora in reverse but carrying away very little angular momentum compared with what is being the input by the accretion disk. Arguably it may well be spinning up a central BH by accretion of gas and stars at the centre of the galaxy that spins them up to the point where the FRII relativistic jets kick in. Prior to that FRI's only have jets with a roughly comparable energy to the IGM and so get blown around more like smoke on Earth. Is this logic in keeping with consensus thinking? Not really. You are guessing and still haven't provided us with some idea of where to pitch explanations. [[Mod. note -- I am not an expert in this area, but (following the standard model of jet production from accretion onto a supermassive central black hole): 1. The angular momentum which gives rise to the jet would be that of the accretion disk very close to the central supermassive BH (say within no more than 100 Schwarzschild radia). The jets would come out just about radially (along the BH's rotation axis, perpendicular to the accretion disk), and so carry little net angular momentum. (Recall that purely radial motion has zero angular momentum.) One of the classic papers on jets is from 1979 Blandford & Konigl https://ned.ipac.caltech.edu/level5/..._fanaroff.html (Blandford and Rees is behind a paywall for non-academic use) 2. I think jets usually start out going much faster than a galaxy's (or even a galaxy cluster's) escape velocity. The jet then plows into the interstellar medium in the galaxy, but I personally have no idea of how much mass or linear/angular momentum ever returns to the vicinity of the central BH. Is there enough to be a significant influence on the accretion disk, magnetic field, or the BH's mass/spin? Hopefully someone who knows the relevant modelling can provide better-informed answers than my educated-guesses. -- jt]] I don't know for certain but my instinct is that once the radiation from the central source really gets going its radiation pressure will expel any gas and dust that isn't falling towards it in big chunks and quite fast. This isn't a bad review for the OP with fewer equations: https://arxiv.org/pdf/astro-ph/0301309v1.pdf -- Regards, Martin Brown |
#8
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Single vs Double hot spots for BH Jets? (e.g. Pictor A)
On Wednesday, February 8, 2017 at 7:45:27 AM UTC-8, Martin Brown wrote:
On 06/02/2017 05:56, wrote: On Tuesday, January 24, 2017 at 9:06:13 AM UTC-8, Martin Brown wrote: On 23/01/2017 22:45, wrote: On Friday, January 20, 2017 at 8:44:02 AM UTC-8, Martin Brown wrote: Thanks for the links and comments. Question: Is there evidence that material (gas and or stars) is "raining" back down onto galaxies where the radio jets appear to be old and fading? Not really. You are guessing and still haven't provided us with some idea of where to pitch explanations. See Malin image at end of this post...........that's the stuff above the galaxy that's observed for many galaxies. I'm looking for evidence that stuff falls back inward and reduces the angular momentum of the material and stars around the central BH system. I forget the references (could look them up, but....), but I recall that active galaxies with jets have excess angular momentum compared to average. So what I'm exploring and asking about, is the idea that a pair of galaxies merge, the angular momentum of the stars is over time communicated to the center. The massive black holes meanwhile move and themselves merge....my idea I'm exploring is that this creates a bar of stars, then the black holes slide down the bars and merge........see wiki: https://en.wikipedia.org/wiki/Barred_spiral_galaxy A dust lane is easy to see in many barred galaxies, and the dust lanes are not aligned. They are offset and near center, curve into a circular geometry. Imagine that's the ~path taken by the black holes which began at the ends of the bar and created the bar, then after losing some angular momentum, slid down the bar into the center and merged (or will merge in cases where there still exists a pair of BH's observed) (is there any observation where there is a bar in a galaxy, AND, there are a pair of bright knots mid way to the center? ie, is there any galaxy where there are perhaps two partial bars that don't connect on center?) That then creates excess angular momentum in the core after the BH's have merged, and that then creates the jets. At least that's the idea I'm exploring. If true, then the only galaxies that should have jets are those where there is excess angular momentum near the central black holes. The question the n is, do the radio jets carry matter and or stars with them? Easy answer, no, but, see: David Malin ultra deep image of Centaurus A showing faint stellar extension s aligned with galactic radio jets (google search images, "david malin, deep image, centaurus A" if link doesn't work: https://www.google.com/url?sa=i&rct=...urce=images&cd =&cad=rja&uact=8&ved hUKEwie4q-Ro5_SAhUCyWMKHRfuClkQjRwIBw&url= http%3A%2F%2Fwww.pbase.com%2Fimage%2F110608746&psi gQjCNHhArY_rn55WQOZp Sdxzgu6_6ah0g&ust=1487700691719675 There is something that is out along the line of the jets (gas, stars, both?). And IF matter were to rain back down onto a system with increased angular momentum, the "rain" would be perpendicular to the angular momentum of the initial system, thus reducing the angular momentum............transforming a spiral into an elliptical (or increasing the size of a central bulge). Thoughts? rt |
#9
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Single vs Double hot spots for BH Jets? (e.g. Pictor A)
On 20/02/2017 19:50, wrote:
On Wednesday, February 8, 2017 at 7:45:27 AM UTC-8, Martin Brown wrote: On 06/02/2017 05:56, wrote: On Tuesday, January 24, 2017 at 9:06:13 AM UTC-8, Martin Brown wrote: On 23/01/2017 22:45, wrote: On Friday, January 20, 2017 at 8:44:02 AM UTC-8, Martin Brown wrote: Thanks for the links and comments. Question: Is there evidence that material (gas and or stars) is "raining" back down onto galaxies where the radio jets appear to be old and fading? Not really. You are guessing and still haven't provided us with some idea of where to pitch explanations. See Malin image at end of this post...........that's the stuff above the galaxy that's observed for many galaxies. I'm looking for evidence that stuff falls back inward and reduces the angular momentum of the material and stars around the central BH system. I forget the references (could look them up, but....), but I recall that active galaxies with jets have excess angular momentum compared to average. The reason that a black hole spins up is that it is very compact just like a ballet dancer spins up when they bring their arms in. The stars and other infalling matter in the accretion disk brings in ever more angular momentum with it and that has to be conserved. It would be as well to study the standard explanation of how Centaurus A looks like it does before concocting a new explanation. http://chandra.harvard.edu/photo/2002/0157/ Fairly serious shockwave through it around 10My ago is the favourite. So what I'm exploring and asking about, is the idea that a pair of galaxies merge, the angular momentum of the stars is over time communicated to the center. The massive black holes meanwhile move and themselves merge....my idea I'm exploring is that this creates a bar of stars, then the black holes slide down the bars and merge........see wiki: https://en.wikipedia.org/wiki/Barred_spiral_galaxy A dust lane is easy to see in many barred galaxies, and the dust lanes are not aligned. They are offset and near center, curve into a circular geometry. Imagine that's the ~path taken by the black holes which began at the ends of the bar and created the bar, then after losing some angular momentum, slid down the bar into the center and merged (or will merge in cases where there still exists a pair of BH's observed) The general theory is that as galaxies age they mature towards having a barred spiral structure through perturbations of the stellar orbits in the galactic gravitational potential. See for example: https://www.nasa.gov/mission_pages/h..._galaxies.html http://hubblesite.org/hubble_discove..._evolution.pdf The same happens in numerical simulations of stars in galaxies. (is there any observation where there is a bar in a galaxy, AND, there are a pair of bright knots mid way to the center? ie, is there any galaxy where there are perhaps two partial bars that don't connect on center?) That then creates excess angular momentum in the core after the BH's have merged, and that then creates the jets. At least that's the idea I'm exploring. If true, then the only galaxies that should have jets are those where there is excess angular momentum near the central black holes. The question the n is, do the radio jets carry matter and or stars with them? The jets will surely entrain a small cylinder of material with them but they won't do much to a star or gas cloud beyond a quick bright flash (and slowing it down for a while) - especially since the motion of a star would not leave it in the jet for very long. Scheuer's denist's drill model of jets still fits the observations pretty well. http://mnras.oxfordjournals.org/cont.../1513.full.pdf Easy answer, no, but, see: David Malin ultra deep image of Centaurus A showing faint stellar extension s aligned with galactic radio jets (google search images, "david malin, deep image, centaurus A" if link doesn't work: https://www.google.com/url?sa=i&rct=...urce=images&cd =&cad=rja&uact=8&ved hUKEwie4q-Ro5_SAhUCyWMKHRfuClkQjRwIBw&url= http%3A%2F%2Fwww.pbase.com%2Fimage%2F110608746&psi gQjCNHhArY_rn55WQOZp Sdxzgu6_6ah0g&ust=1487700691719675 There is something that is out along the line of the jets (gas, stars, both?). And IF matter were to rain back down onto a system with increased angular momentum, the "rain" would be perpendicular to the angular momentum of the initial system, thus reducing the angular momentum............transforming a spiral into an elliptical (or increasing the size of a central bulge). You clearly don't understand angular momentum so this is going nowhere. You would have to drop serious amounts of matter in a retrograde orbit into a black hole to appreciably alter its huge angular momentum. Whilst I am inclined to never say never I am pretty sure that it would require incredibly exceptional circumstances for this to happen in a real galaxy system. A retrograde orbit BH merger would be about the only thing that might. -- Regards, Martin Brown |
#10
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Single vs Double hot spots for BH Jets? (e.g. Pictor A)
On Thursday, February 23, 2017 at 7:47:09 AM UTC-8, Martin Brown
The general theory is that as galaxies age they mature towards having a barred spiral structure through perturbations of the stellar orbits in the galactic gravitational potential. See for example: https://www.nasa.gov/mission_pages/h..._galaxies.html http://hubblesite.org/hubble_discove..._evolution.pdf The same happens in numerical simulations of stars in galaxies. Nice images, some of my favorite galaxies. The sequence for bar evolution seems backwards to me (counter to entropy which wants to randomize things....globular clusters and ellipticals seem to me to be the end stage of evolution). The formation of a bar also seems counter to Rubin observation that the circular velocity is constant with radius.......the larger circular orbit would inevitably sweep the arms into a spiral. This is more the sequence that I'm studying / seeking evidence for: 1) Mice https://en.wikipedia.org/wiki/Mice_G...Telescope).jpg 2) Fornax https://en.wikipedia.org/wiki/Barred...a-99-hires.jpg 3) ngc1097 https://en.wikipedia.org/wiki/NGC_1097 4) ngc1232 https://en.wikipedia.org/wiki/NGC_12...e:NGC1232B.jpg This is about opposite the sequence at the Hubblesite link you sent. Basics: The net angular momentum of a globular cluster of stars is zero, right? Same for an elliptical (generally and ignoring the possible small rotation component some have). In contrast, spirals have large angular momentum in their outer disk stars, vs (much? near zero) smaller angular momentum in their central bulges of stars. As suggested, To merge a counter rotating galaxy is a way to zero out the angular momentum. That's not what I'm suggesting. If you instead add angular momentum that is orthogonal, then you randomize the stellar orbits. This is what we see in ellipticals and globulars. The angular momentum of matter raining down along an approximately axial line (ie, in a highly elliptical orbital geometry, with the long axis of the ellipse being the rotation axis of the galaxy. Then, the axis of rotation for the galaxy is orthogonal to the axis of rotation for the ellipse of in falling material. As this "rain" component becomes "thermalized" by interacting with the mass of the galaxy, some of the disk stars orbits are transformed into elliptical orbits. In this way, a spiral galaxy could evolve to become an elliptical galaxy. And it all began from the BH that ejected matter along the axis of too much angular momentum. Each episode of activity, increasing the size of the bulge, until eventually the galaxy is an elliptical and the stars can age from there............(ellipticals have older stars) I'm not talking (primarily) about BH angular momentum here, I'm talking about galactic angular momentum. BUT, over time, whatever angular momentum the galaxy has winds up being communicated throughout the system and right into the center where it then tells the BH what angular momentum it must adopt because it's angular momentum results from the stuff falling into it, and not the other way round.............. In this model, an active BH happens when an excess of angular momentum is communicated into the BH environment. It ejects material, the material rains down, interacts and randomizes angular momentum of the galaxy, the BH goes dormant and the spiral nature evolves toward elliptical. You would have to drop serious amounts of matter in a retrograde orbit Serious amounts of matter............yes retrograde orbit.............no. It needs to cancel out or randomize, the existing angular momentum. See above. rt |
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