 Great welcome everyone. Thank you for joining us for today's webinar My name is Alejandro, and I'm going to be today your host today We're presenting an X-ray view for physical black holes by Javier Garcia So hold on I have an issue Okay, I was getting a feedback. Sorry Okay, so let me talk a little bit about Javier Javier is our research assistant professor of physics at Caltech and a humble fellow Since 2017 that he took to remise observatory in Germany He obtained his PhD from the Catholic University of America in Washington DC in 2010 Then he did a couple of post-docs in Maryland, CFA, Harvard, Smithsonian and Caltech But before that he got his bachelor from University of Desulia in Venezuela and a master's in physics from the Venezuelan Institute of Scientific Research Javier simulates the interaction of gas and radiation in the very hot vicinity of black holes and works in the new star team at Caltech In collaboration with many other scientists He has developed a state of art model for the X-ray radiation around black holes that is widely used in the community So remember that you can ask questions over email through our YouTube channel or Twitter And the questions will be read at the end of Javier's talk Now, without further ado, we will turn it to Javier So please share your screen Thank you, Alejandro. Hi everyone. It's a real pleasure to have the opportunity to talk to you I admit I've been a little bit bad on following on the talks on live, but I've watched many of them on YouTube So I think it's a great idea. It's a great initiative And I'm certainly very happy to be part of this Yeah, so I'll talk about Something that is that is central of my research as Alejandro already mentioned I work with you know, I try to model the interaction of radiation and matter in the vicinity of black holes and We use this to to learn physics about the systems I think Until very recently this was the only way to to really access this sort of This quantities And I say until now because now you all have seen The really nice picture the first direct image of a black hole by the event horizon telescope collaboration And and also we getting a lot of new Discoveries with LIGO by detecting gravitational wave signals from merging of two black holes But this is just literally happened now For the past I'll say 40 or 50 years maybe a little bit more The really the the best and almost only way to detect black holes and learn about them Was through the very energetic electromagnetic emissions In in in their vicinity. So this is mostly happens in x-rays You you also see gamma rays and radio And sometimes something called but x-rays have a very particular Usefulness for understanding black holes. So that's that's what I mostly do So the outline of my talk is going to be very very short history of, you know, black holes and x-ray astronomy they're the good kind of hand-in-hand together and How do we model the Emission and reflection of the of the radiation With and without gr. I'll talk about my current research on black hole binaries. These are systems where you have Black hole and a stellar companion And and how we use them the models and to get of course with observations to derive These about black holes such as their angular momentum or spin um, and we learn a lot about this and this Other region called the corona, which is where most of the x-rays we we think are emitted and and also something that is happening much We really now start learning more about the micro physics of the material of the of the accretion outflow So I'll I'll I'll say some things some New things about that so I to High and typically we we're talking about 0.1 to a bit more kv We're never very well We're talking about kilo electron Between 0.1 to about a hundred amstrons We use bins Low then you're talking about temperatures of between said, you know a million To a hundred billion degrees. So we're Definitely we associate x-rays with you know, high very high temperature environments. They can be produced by non-thermal particular acceleration, for example in the stroke magnetic fields And uh, and they also They either produce or induce transitions atomic transitions that involve the innermost shells in the atom. So Whenever you talk about x-rays if you think about atoms or atomic transitions, you're you're thinking about transitions that involve the most the deepest levels in the atom So x-rays were discover Is one of the funny stories of of physics. They were discovered almost by by casualty by uh, this german researcher will him rotten and um, he was he was doing experiments with With kathos and and essentially by almost by by coincidence He realized that there were some there was some emission That was energetic not to pass through thick materials and then he started Figuring out there were some mysterious extra some mysterious rays coming out from his experiment he called x because he didn't know how to call it and And he figured out this this had to do with some, you know, very energetic particles And and you see his picture and also the first radiography of the the hand of his wife Right there. So he he was brave enough to experiment with his wife So there you go. That's the first medical x-ray in in history so at the same time I'll I'll say Not at the same time. Sorry. Well roughly at the same time We I'll talk in a minute about general relativity in eichstein theory of general relativity Um, so that was happening pretty much at the same time, but it took quite many years for x-rays to make a two x-ray as two astronomy as as a as a As a Abandoned people will study and this also happened in a kind of a funny way There were people like Ricardo Giacconi here who thought x-rays were interesting to study in astronomical sources We were talking about back in the 50s or 60s where you know, there's About it and all that people knew Was that um son the song x-rays in the sky so they were trying to study the son and Observe x-rays the problem is the atmosphere of the earth the atmosphere is is opaque to most x-rays So you need to kind of go above it So they they have to convince Agencies to build either balloons or sounding rockets to go above So that's that was one of first Giacconi's ideas and the way they sold it to the u.s. Government is to say well, we can put essentially like a geiger counter and You know, it's a super and look and spy on the russians and see bomb testing or something atomic bombs x-rays coming from the Yeah, or whether they're doing or not Of getting funding, but they were of course been looking down but also up so when when they They were expecting um, they were So on to be the right they found so was Very much brighter So was the con So they call this source Scorpio x1 obviously once again extra know what it is One detected in the first x-ray source other than the son discover me uh gave birth to x-rays By doing this kind of mission And we now know this is an actual Where there is a compartment of just not a black hole, but it's an interesting start um, but they have very So x-rays definitely open a whole new window to see uh A kind of physical process Consistent this is for example supernova Okay, you see it in the optical and you see this the shape Expanded after explosion And in the visible but then um if you look at the next race is quite different as you can see The different colors here represent different temperatures emitted by different ions So you see green yellow red and blue there, you know, you have different material Moving at different velocities at different temperatures. So it is quite a contrast What you can learn by looking Of flipping like I'm doing right now between optical and x-rays And if you pay attention in the middle um There is this little point which is not it's not a it's not a but pixel is actually A very strong x-ray emitter and we now know this is a neutron star that is the remnant of the That the left is left after the supernova explosion Um, so again at the beginning of last century Grayson came out with the retina retivity theory and that also opened up a whole as you very well known a whole a whole other Set of new ways to look at the universe And and we now understand that space and times are not absolute. They're they're they're connected and The ions and field equations were first sold by this other guy Uh, Carl Schreiber and and also in 1915 But it's soon right after Einstein publishes his first paper on general relativity and um This is also a beautiful story that I always bring up my talks I think it is it's quite remarkable that he was able to do this during during the war literally during the war He was just reading nice and papers and working on this He died shortly after this but he provided the first exact solution to add some field equations For a non-rotating mass. So this this is what we now refer to as a Schwarzschild Black hole, which will be the solution of a black hole that is not rotating And you you might have heard of things like the Schwarzschild radius um That that's it. So um, what will will the event horizon of this kind of black hole will be two times g over cm squared so um After all this development after jacuni, uh, discovery Then um, if many other observatories were launched either by rockets as I'm saying sounding rockets that are orbital flies or or um Balloons That can go high above the atmosphere such as you can actually detect x-rays and these are just a couple of examples of the early observations Just a few points as you can see in in in the spectral energy distribution if you know, you're measuring different energies You try to come up with something that looks like an spectrum So so the initial ones were very obviously very limited but um by the 1980s there was already enough enough Sensitivity in the detectors to observe x-ray sources that were identified Uh, especially with uh galaxies that were People understood immediately that this emission the x-ray mission were coming from these galaxies Most likely from the nucleus of the galaxy. So that's what we refer to an active galactic nuclear or agn and By looking at many of them we see People saw that their spectrum looks in general like a power law continuum with um with a photon index around You know, um about 1.7 or now this is more about two is the standard um distribution of of energy but when A lot lots of them were observed and put together They come out with enough signal to detect that it was not just a pure power law There were some residuals as you see in the plot down there on the left and that little peak there Um Is is placed at an energy that correspond with emission Inner shell I don't emission is also referred as I don't k emission k is because in the topic model k The k shell is the innermost one so, um, so it become clear later in the 90s with the Precision detectors that there was uh, there was enough there were enough atomic Features in the spectra and when similar spectra were taken from another agn They they were able to identify much better the I don't k emission There also something happened and is that they realized that the emission Is not symmetric It's actually quite a symmetric and skew as you can see on the also on the left bottom panel For a famous agn galaxy mcg minus six thirty fifteen and People were quickly realized that this This could only be explained if you include relativistic effects They figured out well This is coming from the center of galaxies and we believe there might be a super massive black hole in the center Then if this emission is produced close enough to the black hole, then Um The that there might be effects that change the way the the line looks like So in fact, um, when you think about christian to a black hole The the first thing that comes to mind is an accretion this and this is because of conservation of angular momentum All the creative material will tend to form a flat structure circling around a spider later on so, um you have uh you have, um You have a the it forms a relatively Thing a structure or disk But it doesn't go all the way to the horizon. Um, there is a point There is an actual sharp edge to the disk Where um, there cannot be more circular orbits So it's called the innermost stable circular orbit radius or isco For for any Particle beyond this point or closer to the black hole from this point It will essentially plunge directly. So they will not it will not spiral anymore It will can sustain any any kind of orbit. It will just go directly. So as appropriate structures as a disk Uh, that's what it will stop Um, and and and going back to the idea of the relativistic iron lines So this shows a little bit more what I was mentioning about the relativistic effects And you know, what happens to a single line a single photon Or not necessarily a single photon, but a um a line and a single energy That is produced at a particular orbit in in a rotating disk So a newtonian physics will tell you that you should see a double horn A structure because you're going to see part of the disk That is receding from you and part of the disk that is approaching towards you So one part is blue shifted the other one is red shifted and then you have the double horn But because of a special relativity The part that is blue shifted is going to be boosted. It's it's going to be boosted In in intensity towards you while the part that is reshifted is t boosted. So that's what you see Uh in the second panel the asymmetric double horn So one is going to be more intense as the other and then general relativity will uh will um Add the additional effect of the gravitational redshift. So the entire structure get gets redshifted By gravitational effects. So this is on top of the standard Doppler redshift, right? So um When you combine all this you you get this this um line profile That actually seems to fit well What it was observed back in in the 90s And you see that that is in the right panel I show the difference in in a line feature For a schwarzschild black hole and for a kerber hole and the difference as they mentioned schwarzschild is The black hole that has zero rotation while the care comes from the caring human solution That's the case of a of a rotating mass So for a maximal rotation, you see that the shape of the line is actually different And this is because this has to do with the location of that inner Inner radius of the christian d's or the isco That location the place where the christian d's edge ends is dependent on On how fast it's retaining because frame frame dragon effects and other things It will move around so In the middle I show the non-rotating black hole It's it's the the inner most radius is set a certain distance Then if if you have maximum rotation Like in the bottom panel it moves closer a lot closer almost touching The heaven horizon and the other extreme case will be maximum retrograde rotation that will be You know the the disc and the black hole spinning in opposite directions and in that case it actually was farther away And because you're changing the location of the christian d's you also change um the the location of where the The spectra features are being produced. Of course, how close to the black hole are they being produced and therefore The gravitational distortion they suffer is going to be different. So in this way you have some some sort of direct connection to The spin of the black hole and and this has been known for quite some time You have a monotonic relationship between the spin And the position of the of the isco radius We typically refer or we typically measure this With a dimensions list spin parameter that i'm showing here c j over g m Square where j is the actual angular momentum of the black hole And and you see here two cases for you know zero spin. It will be a star zero This this spin parameter zero is obviously no rotation and for a 10 solar mass black hole The the radius of the isco will be about 90 kilometers as opposed to the maximum rotation Where you have a radius of 15 kilometers. So this is the kind of um a small Spatial differences that we're trying to measure here um With modern observatory things have got of course a lot better. I have worked a lot with Uh a satellite call r x d the rostics ray timing Explorer it was already the commission in 2012 and it had a resolution of about one kv at six kv And i showed an example there from a paper a few years ago And i'll talk more about that particular case These are these two cases are the same object. It's a black hole binary now We're galaxy gx 339 minus four the one on the right is Is um data taken by two newer instruments nosa and suave No studies the color one. So you see on the top the actual spectrum that Detected counts in x-rays In a in a much broader band and the level of background noise that you have or background counts from the sky or from the instrument for anything else And you see how much better the resolution has gotten It's a 0.4 kv a 6 kv. So it hasn't improved a lot in the future. Respect things Uh dramatically better. So this is what it's being currently work on for future x-ray observatories This is a european mission called athena that will have five bb So we're talking about, you know one kv a 6 kv We're talking about just a few electron volts at the same energy It will be remarkable what we can see and then Definitely get a lot more detail of What's going on in this system So there's a clear need um already and it will be even more in the future for models that work on on that are capable to um reproducing these sort of observations and this is uh really important because the physics that we're talking about this physics of accretion uh emission of x-rays And and all this is applicable for in a in a wide range of masses It's it's observing neutron stars that are in binary system. It's definitely observing stellar mass black holes that are also in binary systems And it's also observed in in supermassive black holes in agn Which also have um, they don't have a companion, but they have a whole galaxy to supply Gas and they also form accretion this and the phenomenology is It's pretty much similar the scales The time scales are different The masses scales are certainly different, but the rest um Anything that is mass invariant will kind of apply equally so, um What I've dedicated a lot of all my efforts in precisely modeling what the x-rays look like near the subjects and in particular the um component that is reflected from the accretion this so, um I'm not going to go through the details now just you know If anybody obviously is interested on this it can contact me and I'll I'll bore you to that with the details, but um It suffices to know that it's a fairly complicated problem because you need What you need is to solve the problem of rigidity transfer in an optically thick gas Put in a lot of lines. So that requires a lot of um first a lot of Knowledge on the tomic physics. So you need atomic quantities for all Astrophysically relevant ions for as many lines as possible, but then that makes the calculations quite um CPU intensive so We've essentially we've done this and this is just an example of One calculation where we solve for the unisation structure of a gas that is illuminated with x-rays We see the changes in temperature And then we see what the reflection Spectra comes back. So in the rise i'm showing the spectrum in x-rays If you illuminate a parcel of gas with a power law like they continue observing In most of these sources, which is shown with the dash black line there then What you what you might get back depending on the on the situation is something like the blue line, which is a very rich Spectrum with a force of lines that are both emission and absorption lines And there are features that have to do with electron scattering as well So we need to Essentially do this as best as we can before we can reproduce observations This is these are more examples of How things change with the parameters in the model Most of the models that are going to be parameterized with this unisation Parameter that has to do with the flux that goes into illuminating the disc versus the density and That essentially gives you a measure of how ionised the gas can be and if you look at the numbers and you don't need to Understand the details of it, but obviously that psi number that ionisation parameter the larger it is The more I united you nice the gas will be So you see the changes in spectral features as you increase more and more the unisation This can be done by increasing the flux or just decreasing the density Once this is done that it takes For a Essentially you have to code a range of parameters and make a table of many many as synthetic spectra It could take you know, or the of the order of a million CPU hours Um Then you have to include the relativistic effects as a post-processing Technique and and we do this We do this by a ray tracing convolution Um, essentially you follow photons in a curved space time And you predict what the effect is going to be given, you know their position in the disc And how the illumination of the disc uh was produced in the first place So this is all combined in a single model that people can now use To model any given observation in x-rays. So the model parameters are many But that's this good thing and a bad thing is a bad big thing because then you have too many degeneracies sometimes But it's a good thing because essentially the model is sensitive to many important physical parameters and then you see once again The the spin of the black hole is one important parameter You can measure the image of the Christian disc might not be right at the east going You can also measure if it is highly truncated or not inclination of the Of the disc is also very important and then um It will it will change the the amount of um relativistic blurring you have in the spectrum There are many other parameters like uh, you know the iron abundance or Um things that have to do with the illumination of the disc I'll talk a bit more in a minute So this is the complete sort of cartoon picture that we have and we think what happens near a black hole You have then an Christian disc and then you have some A strong emission of this power law That I mentioned before we we don't clearly know what it is, but the the most um the most um Famous idea is that you have compton scattering in some sort of corona very hot Plasma is comptonizing photons that were emitted initially from the christian disc thermal photons get the get the gain energy in the hot election gas of electrons and They produce a power law like the blue Spectrum that I show on the top and then if this Part of this radiation goes to the observer directly and you see it essentially as a power law in energy But if if it illuminates some of the part of it illuminates a christian disc and you're gonna see Uh, the reflection features that I mentioned a second ago If the reflection is far enough so you see something like the green line you see sharp Emission features those are the the two big ones that are actually from iron the the k-shell But if the emission is Relatively close to the black hole then you're gonna see is you're gonna see the relativistic effects and sometimes it can be so string that they completely blur out the spectrum the smooth everything out and Essentially something like the green line will all the green spectrum will become something like the red spectrum there They it looks almost featureless. There are features that are just very soft and smooth so, um, this is just to say also that The the panel on the top is an actual feed to real data taking from this black hole binary system Gx 3 3 3 minus 4 so this is This is at the bottom is a cartoon the top is real. Uh, it's real science done So you have a combination of all these different components Um And and as This is i'm just repeating myself a little bit. This is just to show more clearly How the a given model will change depending on how you change the parameters So here i'm showing four important physical quantities the spin the more spin you have the more Blurring of the iron line you see but is it it's not just the iron line You see the entire spectrum changing to certain degree, but then there are all the quantities like the coronal high and is it how high this Uh primary source of x-rays is placed above the accretion disc Will change things because it changes the way it gets illuminated And that radiation is also affected by relativistic effects because you you can have beaming of the photons that go towards this So the closer you place this this corona The more beaming it acts like a like a magnifying glass It just focuses all the radiation in a tiny region very close to the black hole So you see when h is is small you see the this this extreme blurring of the spectrum And of course things that i mentioned inclination Essentially moves the blue side of the line you see moving to towards the right the more inclined it is And i don't have on us of course will make The item features more More prominent, but it also increases the photoelectric absorption near the The line so it makes both increases the emission But also somehow decreases the continuum around the line. So all the things are important, of course And and so far using this technique we have measured Spins for several super massive black holes in in ag n's This is uh in the field in the bottom shows an actual Distribution of spin versus mass compiled recently by Reynolds and also by Vestodavan in in 2016 and The problem here is There is a lot of there are many big error bars as you can see So the actual determination of spins is not always very well It's not very accurate And this is something we're currently working and trying to Reduce as that those uncertain things and get a better distribution. So you you essentially we need a larger number of Objects, but we also want it doesn't really help too much to increase the sample if If we don't have good constraints However, this already shows something interesting, which is most of the spins and actually the better measure ones are Um a closer towards the maximum value So it means that most of the black holes we see the super massive black holes are actually rotating close to the maximum Value and this is important because this distribution can actually help To constrain Theoretical models for the formation and evolution of super massive black holes because Different models that are based on different prescriptions. Whether, you know, black holes gray by steady grow or whether they are By mergers and if these mergers can be chaotic or can be hierarchical. So there are many different proposed channels for for the formation and grow super massive black holes But these different scenarios will then predict different distributions for spins that you will measure today So we can actually have a very good distribution measure We can go back to the theoreticians and say, you know, all these models are wrong Or or are rejected at least by the observations. These are more likely to be, uh, the right ones in the case of black hole binaries and Again, uh, when I say black hole binaries, this means Stellar mass black holes with a stellar companion Which are the systems that we can install it with x-ray reflection You see a list. It's maybe not very well Uh, it's not very clear the names, but it doesn't matter what you see is a compilation of Moral is where we are with measuring spins. So in this case, there is some, um Sort of a better picture, uh, there is a wider distribution of spins. It also I'll say They're slightly better constraints. There are still some cases especially towards the lowest spin that are difficult to measure because typically those are the ones Um, when you see an error line, so you need better data in order to have a better constraint of of the Of the spin parameter But, you know, it's not it's not, um, it's not all roses Is not all great because for example in the case of ckx one, which is a very famous black hole system when you look at the reporter values in the literature in the last 10 or so years you see, uh, a dramatic change of Both accuracy and the precision of the measurement So I say that that's not a real trend. It's not It's a real trend because it exists, but it's not it's not a physical trend It's not that the spin is changing what is changing is the quality of the data and the quality of the model Um, hopefully we're getting smarter in understanding How to feed these observations and derive a proper quantity that actually makes sense So we're now consistently getting to agree that the spin in the system is close to the maximum There are other things, uh, very interesting that you can do with reflection spectroscopy and you can look at evolution of Things that the corona and the christian this especially in black hole binaries because The given that there are smaller systems the time scales are much shorter. So they evolve much faster in time So for the corona is we always call it some sort of a mysterious thing because It is something that has been proposed, but we don't understand much Of what is its origin or or even the geometry you can you can play with different models That say well, it could be a sphere. It could be a just this spherical gas of a hot elections Near the or around the black hole. It could be a sandwich In the desk it could be some sort of a slab Or it could be a points or sitting on the axis that will resemble something like the base of a jet or or something like that So depending on what you assume for the geometry of the corona, you're gonna get Different reflection features or slightly different behavior of the system So we're trying to learn how What is the connection between the corona and the disk and how the two of them evolve? One way to do this is of obviously absurd systems for a very long time And what i'm showing you in these little movies actual data from The satellite rxt taking over I'll say over a decade for This source gx 339 and you see this these tracks that they're doing in in this plot is that is showing In the y-axis shows the x-ray luminosity While in the x-axis it shows the spectra slow meaning The spectrum is changing quite a lot But it also is luminosity because these sources typically go into what we call albergs So they flare up in x-rays for a relatively short amount of time they evolve Lots of changes happen and then they go in quiescence again They kind of are all barely detectable or simply non detectable in x-rays So we're trying to understand and follow this evolution with the rich amount of data that we have in hand This is to show what the heart and surface state looks like Heart state because the spectrum looks hard meaning it has most of these photons in high energies while the surface state is you know most of the signal that you see comes in soft photons soft x-ray photons This is because one is dominated by non thermal emission Power law the other one the surface state is dominated by thermal emission from likely from the christianness This is another example. This is cx1 look With almost every single x-ray instrument In both the heart state and the surface state and you see this huge dramatic difference in the spectrum distribution You have to think about in terms of energy. How much energy is Is put in terms, you know in photons For example in the heart state you have most of the energy coming at 100 kv While in the surface state most of the energy is coming close to Maybe a few kv Maybe a few kv. So this is this is a huge difference in terms of energetics. So there is something very very Big and dramatic changing and the system to behave in this way and the time scales for Changes between these states can be between weeks and months. So it's relatively short It's quite impressive. So we follow in the heart state one of these sources gx339 We look at the spectrum When you feed a continuum to all the spectra what you see something like this, you see very clear features of reflection the item k emission What is called the item k edge is an absorption feature and also The thing on the right is called the Compton hump because this is Is a broad feature that comes from electron scattering So photons Scatter from electrons in the in the christianness itself So which we feed our models You see the the version called silver is the ombre or Reflection that means no gr The one called relcil is a relativistic reflection meaning you include the gr effects So in this case as I show before you need both of them because likely you have reflection from both close and farther away from the black hole and The panel in the bottom shows the residuals to fit in this model to the data that there is a lot of counts in this data So it's a highly highly significant detection And this is a pretty good feed The good thing about all these colors that show different spectra is that they're showing a spectra different Um at different levels of luminosity of the source and we measure this in terms of the editing to luminosity So between 1 and 20 percent So you're seeing essentially a change of a factor of 20 in luminosity But we can feed all this spectrum with the same model. Of course some parameters will change And and the ones that changes are precisely the location of the inner disc the edge of the inner disc and um Something that is called the high energy cutoff That is related to the temperature of the corona So in short what we're seeing in this in the system is as the luminosity increase You're seeing that this coming closer and closer Towards the black hole So likely that this was receded and that's what this the system was not detected in x-rays and for um through some mechanism There's no Well understood yet You you'll increase accretion rate in the system. You start the outburst start filling in the accretion flow Forms accretion this and that this is just getting closer and closer It's so is it's also increasing the luminosity likely because accretion rate is is increasing But then you see the temperature of the corona is going down and And this also makes sense because the more luminosity A plasma will put out the more it cools down. So the this this hot gas of electrons will Uh cool down efficiently by just releasing photons So increasing in luminosity means Your your corona is is getting colder But we also see this correlated with the disc moving inwards and Just just to give you an idea The changes in the inner edge of the disc that we're detecting with this with this technique is If if the mass will be 10 solar masses, which is not certain But let's say that's a that's a typical number for 10 solar masses. We're talking about the other 45 kilometers for a system that is Maybe eight kiloparsecs away. So that's quite remarkable in my opinion This is another example of a very new Black hole binary system was detected. Maybe with this cover maybe a year or a year and a half ago It's called maxi j 1820 And it has become one of the brightest if not the brightest system in x-rays It has been observed by essentially every every detector that have been able to observe and Um, this is a very recent paper by erin cara. It was published in nature They they were able to not only get a spectrum, but they also got very good timing So you can measure Timelapse between different bands in the spectrum And plot it like here versus frequency And without borrowing with the details, what this means is you're detecting You're you're sampling the time scales of the variabilities that you might observe in the spectrum And the different colors what they're showing is um, essentially different time scales for Responses between the primary emission and the reflected So they can for the first time in a in in this kind of system. They can Have an indication that the crown is actually evolving And getting a smaller because what you're seeing is um, the frequency Changes that the changes in frequency you can connect it to some scale for The meter and for their reflection as well So this is a pretty exciting new results We have looked at other systems. We're actually doing a whole bunch of them and This is another interesting one is called xdj 1752 Is very similar to the one I showed before it has a lot It was it got really really bright in 2011 And then he died and we haven't been able to detect it anymore The data we go was so constrained and was so significant That it pushed the models to the limit and we have to revise off the models because we realized we needed to do better something we learned about this the system in particular is that We we were able to make differences between models They have different prescriptions for the illumination. So if you for as I mentioned before if you assume a lamppost Geometry in which you put the illumination you the source of photons is just sitting in the axis It will give you an answer But if you assume a power low emissivity Something a more extended corona or this lab corona that I talked before It will give you A different answer So the the thing that changes here is inclination the inclinations between two different Geometrics are very very different Are is a predicted one? So one is 67 the other one is 36 The good thing about this is that we have an independent measurement from the from a radio jet That says that the inclination should be lower than 49 degrees. So in this case We can rule out the power low emissivity and and and then we see that then in this system The illumination is likely or the configuration is likely to be more like a lamppost geometry So it doesn't have to be necessarily a point source, but it's certainly The model is calling for a source that is very compact and towards the center another system We're working right now Is called j 15 50 is very similar to gx 339 And the good thing about this system. It has very well determined properties So in this case, we know the inclination Of the binary orbit. We know the mass of the black hole. We know many things about it So we've we've done archival data analysis with different observatories For the brightest observations we found And you see this this kind of messy plot is it shows all the different Spectral components that you need to include to fit this data. So it requires It requires a corona or a non-thermal emission requires a thermal emission from the creation this Relativist reflection distance reflection and also some high energy tail That is possibly linked to emission from a jet And the difficulty we have here is that With the best fit that we have After working really hard on it We always get an inclination that is much much lower than the binary orbit inclination that as I said is very well known So our inclination is 40 degrees What the binary is supposed to be about 75 degrees So this is it's a very big difference that we don't fully understand One possibility is that you have a misaligned disc This is very interesting. You have the possibility for the inner accretion flow to be Or or let's say if the spin axis Of the black hole is misaligned with the orbital Inclination then you can have an inner accretion disc that is warped with respect to the outer accretion disc The problem is this wouldn't explain Why the also the inclination measured from a radio chip that has been observed Agrees well with the binary inclination. So another possibility Is That you have obscuration Of the inner accretion flow If you think of an accretion disc that you're seeing processed at a very high angle Like in this case you can have the disc This is not infinitiveness as small or Thing it has it might have some vertical structure And this structure will then block part of the radiation that is coming from the center And The initial tests that we've done are the initial simulations show that what this will do is mostly Reduce the amount of radiation that you see on the blue side of the iron k mission And this is the part that is most sensitive to the inclination. So in other words, you can mimic An iron line or a reflection spectrum That that is that looks like the one for low inclination in a system that is in reality High link line. So this is a possibility That would explain what we're seeing in this system This is this is really really important because then for the first time we're seeing How much information we can get for a single System we can understand now more much more about what is the structure Not only of the overall binary, but also the innermost region in terms of inclination and things like that Um Then this is to Maybe I'll skip this one But just to say that some of these albours are also failed They don't they don't follow the whole transition between hard and soft states. Sometimes they just flare up and they die again And we we get a bunch of this but when we observe and we also we still see Signatures of reflection, which means that the inner Christian this must be very still very getting very close to the black hole close to the So that's that's interesting I think I'm gonna go a little bit faster now because I've been talking for a long time But I just want to mention the newer thing is For the first time we have access to More details of the micro physics of the accretion flow Particular what happens in the disc we know that the densities of the disc Accretion this around black holes can be quite high according to mhd simulations Like they weren't shown here can be can be as high as 10 to the 23 particles per centimeter cube and We realize that the reflection models we've been running there They're always assumed some sort of fiducial density of 10 to the 15 Which seemed to be okay for agn but for uh stellar mass black hole By no b and even for agn themselves. They might it might be that this is too low And this affects the shape of the reflection because Increasing the density increase I think all free free emission of brems trial emission Um So it changes it as you see in the spectrum on the bottom it changes the soft energy is quite a lot You have an enhancement of of soft x-ray flux So when we use these models we tested it on a few ag and this is one particular case of an ag in core marketing 509 we These are systems in which we already see some the strong soft access emission that is typically difficult to explain Some people have argued for a warm corona scenario where you have some older corona Even more mysterious at the first one trying to come out with an explanation for this soft emission But what we are able to do now is that with reflection itself Because of the higher density in this as we're assuming now Then it produces more free free emission And hence is the soft flux and and therefore we have a we can then now explain this this x-rays of emission In the case of black hole binaries what the high density is doing is is helping us with Having a more reasonable iron abundance So tip is very typical when you feed this the system sometimes the iron abundance require this is becomes completely unphysical And talking about in terms of the solar values, which is what more or less what you respect We're talking about factors of a few maybe Even an order of magnitude higher than the solar value. This is very very difficult to explain Because you don't expect such a large enrichment in all the systems consistently so Once again the enhanced free free emission changes the shape of the spectrum and that seem to have a positive Effect in reducing the iron abundance that you require to feed the same data We tried that back in gx339 with where we were finding something like five times solar Now we got something between one and 1.5 which is much more reasonable. So it seems that We're going in the right direction High density will have effects on the atomic data, which is something we're revising now You can imagine very very high densities the atomic potentials change uh, that are screening effects and things like that and and that will change Different atomic rates like for example, the dielectronic recombination Seems to be significantly suppressed So in short once again, you don't need to know all the details But what this will mainly changes the overall ionization of the of the gas under the same conditions So if we run something with the standard dr rates, we get we get a particular solution that says well iron 13 in this case is the most dominant iron But then exactly same conditions suppressing the r will give you a higher ionization for the same conditions So clearly a high densities. We need to to worry about these things and This is what happens to a reflection model. The ones that I showed before once you start suppressing the r It has kind of like a similar effect as they have the high density by itself increases the soft energies um flux by quite a bit But it also seems to have an effect on the iron line as i'm showing the just that the um panel in the bottom It produces more iron That the same model with the standard Yeah, so we're still investigating this so I'll stop here I'll say just you know extra reflection spectroscopy has been great continues to be a very powerful tool to study the systems um What we what we can learn the big things we can learn is evolution of this and corona and systems that change fast like black hole binaries We can measure black hole spins For quite a large number of sources. We hope to get better on this And we are now understanding even more about the micro physics of the grid inflow and even Using this as laboratories to test atomic data, sorry atomic calculations and properties Of the of the ions in it. So I'll stop here and take any questions. Thank you Thank you very much Javier for this very nice talk and very complete. I really enjoy all the details We have a couple of questions from the youtube channel By brian stevens, but I think you answer his first question Which was does the flux or the density affect the relativistic effect on the iron reflection? Right. So so I'll say just a relativistic So the the relativistic effects are separate from that, but It will affect the shape of the spectrum and And it will therefore affect, you know, it might affect what you get out of uh, say, what's what's this spin? What you derive from it, yeah Okay, and then the the other question was a low inclination maybe due to a magnetic effect I think he's talking about the degeneracy is that it might be can you can you repeat that please? Low inclination may be due to a magnetic effect Um, it's referring to that the degeneracy of that you might be able to measure something with highest spin at low inclination or I suppose Well magnetic fields in black holes are Well, I'm not I'm not exactly sure what what this question refers to If if it is going in the direction of changing The line emission or the way the line looks by it's something I see many effects. I think the The magnetic fields that you speak in black holes are much smaller to do this Okay, I don't think it will work, but maybe the person is thinking something different. Okay, so ryan if you're Here please leave this comment on that Now let's see if our coordinators have questions I have a question for Javier. Yes. So very nice to talk Javier first of all So I have a doubt is it possible With x-rays to try to constrain or to see some deviation for instance with gr Because I don't know if it is in the inner part or because yeah all the part Yeah corona is very interesting, but right also Yeah, I didn't touch on that but um, I actually work in Alejandro has been involved with this I work a lot with a group in in Fudan in Shanghai That is precisely doing tests of gr with With this with this technique with x-ray reflection. So the way they're doing it is by Everything in our model is obviously built upon the Care metric, right? So what they're doing is saying well We can change the metric we can introduce now metric that is modify This is um a metric in which you have deformation parameters And if you set them all to zero, obviously you record you recover the care metric If they're non-zero, then they just simply introduce different deformations. So the idea is We use this this metric we rebuild them the same model using this metric and then go back and feed and look at the same observations and and try to understand do we always recover All these parameters to be zero meaning do we always recover care metric for There might be cases in which not So I guess luckily so far we haven't found any Any case in which uh the care metric is being violated um It's a little bit more difficult because this then goes hands-to-hand with you know, what is the What is the quality of the data you're you're looking at? There are many parameters already in the model as it is that it can it can introduce degeneracies and things like that So it's not it's not a straightforward um way of doing it But I think it's interesting enough to give it a try Okay, thank you There's another question and i'm gonna copy it in our chat here a bit and it's from maria angeles pedes garcia She's asking could we know the origin of some black holes like for example, uh Newton star collapse into a black hole um I'm not sure how this technique will help you on that um That's an interesting question. No, I I don't I don't I don't have a good answer for that I'll say though that I I mentioned briefly in one of the slides, you know, this this is sort of um Phenomena are shared by many systems including neutron stars. So we do see We do see relativistic ionizing Neutron star system with a star companion As far as I know, we haven't seen a neutron star becoming a black hole um Not that i'm aware of Sorry, I don't have a better answer for that Yeah, maybe just by measuring the speed i'm making population Perhaps yeah, thanks. You might you might get some information about the origin Okay, uh, I have a question. So whenever you do those simulations about spectrum and silver How does the normalization work? like whenever you You have just different plots. So so I was wondering like whenever you really measure something. How do you compare that normalization? Well, the normalization will give you information about also the part of the geometry Because whether you have more or less reflection a It might have to do with the way this is illuminated So this is this is what we call the reflection fraction. So the amount of reflection to power law that you have okay, um One way to do it there are different ways one way to do it is to leave that as a free parameter So you have that proportionality between the two components to be free and then you just It will do what the data wants it to do But the way to connect it with the geometry is when you prescribe an actual geometry like the lamppost Then the lamppost will tell you what the number is What that normalization is based on the spin and the coronal height And the inner radius So those quantities set the normalization And if you can actually feed the data well with that with that particular configuration, then they'll That tells you that says you good information about it Okay, okay. Thank you. There's another question from Sulawf Chalice Can the inclusion of ionized absorption affect the iron abundance parameter for agn? Uh Say the last part ionized absorption can affect what sorry Can the inclusion of ionized absorption affect the iron abundance parameter for agn? Uh in a way it it might uh, it's it's in many in many agns We see what people refer to as a warm absorber right so that there is certainly some material absorbing in the line of sight and That complicates things For several reasons because you have an extra component to take care of and if the absorption Uh sort of falls in line with the mission that you're trying to measure obviously that that might are my complicated things It used to be a group of people that uh claim that through different types of ionized absorption you could mimic What it looked like a broad iron line Essentially, they will say well is it cannot it could be that you're not seeing a broad iron line What could be is that you're seeing an iron line But then a continuum that gets distorted by different types of absorption and you believe and you think Um, that it is a it's a broad iron line. I think that's that has kind of proven Um, there is not the case that doesn't work all the time first of all and second It wouldn't explain the entire reflection spectrum So to the specific question of whether it affects the iron abundance Um, I would say no because the iron abundance is something to measure directly by seeing the mission Is sensitive to the to the how how strong the mission is but also how how deep the iron k h is And typically the ionized absorption is happens at lower energies So it is a complication to overall model and if you if you don't do it properly you mind up with Um as pollutes results, but I don't think it directly affects the I don't know Thank you. Um Any other question guys, okay the the last one then I'll do it. Um So in all those models you presented like normally what you have is the corona somehow has a geometry then It illuminates the disk and then we have this reflection spectrum Do we ever consider the direct component of the corona? And yeah Yeah, for sure. That's like a huge impact. It does it change? Yeah, yeah, I mean you that is that is typically the first component you see the most obvious Okay, but that's good. Just going to be but it somehow is just like featureless In the sense that just okay It doesn't have features, but because it's a continuum. It's a long term of continuum, but it does have um For example, they have the the high energy cut off which I went very very fast over But you don't see essentially you don't always see a power of extending to infinity at some point or so energy it rolls over and We believe this is because if you are producing up this power low by um continuously Comtonizing photons in hot Gas of electrons You know photons will gain certain energy that electrons don't have infinite energy So there will be an energy up to some point So that's how we talk about the temperature of the corona that could have actually tell us What the temperature of the of this corona might be so it's it's a good It's a good um A very resourceful component. Okay. Yeah Uh, thank you Javier. Thank you everyone for your question and attendance And remember that if you have more questions, you can always email our speakers and they will be happy to Put up the subject love physics relation. So so they will not skip you or it was just let us know now. I'm kidding So thank you very much. Uh, thank you Javier and we hope to see you in the next webinar Thank you. Thank you so much. Yeah