 Vseh natakjev je zelo gravitesno otev, evočenje gravitesno otev z tem, da je naša vseh naša vseh naša, da je naša vseh naša vseh, da je naša vseh naša vseh naša, da je naša vseh naša vseh naša, ta heliskopem od radioj do vseh v sej optikal. Vseh nekaj nekaj ne bozim, in zelo človek in izvahovati. Zelo smo zelo svečno vzivati v transjetnih gravitajšnjih vevstih, ker so to vzivati vse, da je bolj zelo, da je vzivati vzivati vzivati vzivati vzivati. To je, da so neseljamo, da vzivamo, da je vzivati vzivati vzivati vzivati vzivati vzivati koalizenje z kompakte občet, so neutron star and all black coal binaries and core collapse of mass star. And also yesterday we saw that the coalescence of compact objects are more promising in terms of energy emitted and also rate with respect to the core collapse of mass star. Again, the slide of yesterday that showed you the rate. So yesterday we said that the rate is very, very uncertain but if we believe to the most likely rate we will have more or less one event per week when the LIGO and Virgo will see the sky as a network in full sensitivity. Today we will focus on neutron star, neutron star, neutron star black coal and not black coal, black coal because black coal, black coal, stellar mass black coal, black coal I'm not expected to emit electromagnetic emission. So we will focus on these two class of objects. And here is, I repeat again, is the distance up to which LIGO and Virgo will see this object when they will be in full sensitivity. This distance is an average in the sky taking into account the sensitivity of the detectors in the sky that is a bit different in the different part of the sky and it's also an average on the system of orientation. For the core collapse of massive star we said yesterday that the energy emitted, the waveform are more uncertain. We expect less energy emitted in gravitational waves and so the majority of the model expect this sources in the local galaxies. And there are some optimistic scenarios, some optimistic models for which we can arrive also to 10, 100 megapars. This event are very energetic event and they are also expected to emit electromagnetic emission and they are linked to the gamma rebarst. I don't know how many people are familiar with gamma rebarst but I will give you an introduction on them, on this object. And Kilo Novi and Super Novi. And we will talk about these objects today. Why it is very important to try to find, to try to see the electromagnetic counterpart signal when we have a gravitational wave signal. First of all because when we will have the first event it will be very important to say this is the object, this is the astrophysical sources that emit this object and so it will be a confirmation of the fact that we are really finding something that is an astrophysical sources. Another thing is that to discover an electromagnetic counterpart means also to have a better sky localization. Yesterday we saw that the gravitational wave detector is not a good sky localization. And so if we are able to find the electromagnetic counterpart we are able to reduce and to know exactly what is the sources and so also to know what is the host galaxies of our signal. And very, very important is also the fact that we can use all the messenger to understand our object and gravitational wave and electromagnetic messenger provide insight into a complementary physics because electromagnetic give us information on the environment so temperature, density and also we can look for a shift and on the other side of the gravitational wave give us direct information on spin, mass and also distance. And other things for which is very important to have an electromagnetic counterpart is that yesterday we saw that in the case of binary system we can make an analysis that allow us to know all the parameters of the system and so if we know the electromagnetic counterpart we can fix some of these parameters. For example, we can fix the distance, we can fix the orientation and so these allow a better estimation of all the other parameters. And now there is also a very important study that start to try to understand how to use both information to constrain very important things like the neutral star equation of state and they will come back on this point later. And so we will open really a new window and we have also this possibility to put together all these different ingredients. So now we will see more detail what we expect from these sources from electromagnetic point of view and then we start with gamma rebarst. So gamma rebarst were first seen around in the 70s and at the beginning by military and are these very brief, sudden and very, very intense flash in the gamma ray. And the duration go from few millisecond to 100 of second. The band is typically so hard X, X and gamma and these are the flux. A satellite very important was BATSI to understand this type of object because BATSI shows that this object that happen more or less with the current satellite we see them more or less one per day of this event show that this object are distributed in a uniform way and so that they are of extragalactic origin. Another big step to understand the gamma rebarst was done by BEPOSUX. This is a really very good example on how much increase the sky localization is important because with BEPOSUX BEPOSUX was this satellite, this gamma ray satellite with also an X-ray satellite and so when BATSI saw a GRB in the gamma ray point the X-ray satellite and it was able to reduce the error box very big that is typical of gamma ray to a very small error box and so we were able to identify the first afterglow of a gamma ray barst. And after this the same gamma ray barst and I will say you in detail what is an afterglow but it is the emission in the X-ray that happen later with respect to the gamma ray and with the ground based telescope it was also possible to see this object in the optical. So from many degree this allow to pass to have object within arc mean. This is an example of what we do today. Today we are able to identify the host galaxy of this object because we are able so to see this object in very detail so to identify the gamma ray barst and then to make a campaign of observation, a multivavelent observation that allow us to see this object in all the band from the radio to the X-ray. So now today we know that they are cosmological event and that they emit very high quantity of energy up to 10 to the 53 hair and I told you in really few seconds. So since the beginning, since with bats it was clear that there are two population. This is the bimodal duration distribution is the duration of this gamma ray and these are the one that are called long gamma ray barst and these are the short gamma ray barst. The long gamma ray barst have a gamma ray duration that is larger than two seconds and the short gamma ray barst shorter than two seconds. These two population are different also for their emission and here there is the so-called hardness ratio. It is the ratio between the hard counts and the soft counts so this is the two band of batsy this is the plot of tin for batsy for this population here and so this is the counts in the more energetic band with respect to the counts in the less energetic band and what you see is that the short gamma ray barst are more hard and the soft gamma ray barst are more soft. These represent two populations of events and how we can explain these two populations? These populations are objects come from different progenitors. For the long GRB we have strong observational evidence that they are associated with the core collapse of mass star because in the same position of the gamma ray after a time that sometimes is a week, other times is months we saw in the same position a supernovae and so this means that these objects are linked to core collapse of mass star. The harder population, the short gamma ray barst we have no strong observational evidence of their origin but there are some indication. First of all we never see associated with this type of object supernovae and they are typically associated with an older stellar population with respect to the long and they are typically located at larger distance with respect to the center of the galaxies and the larger distance with respect to this type of object. This association with older stellar population and the larger distance from the center of the galaxies is the ones that we expect for binary system of compact object because when a binary systems forms what happens is that there is some kick velocity that tend to bring them away from the center of the galaxy and so their position and their also association with this older stellar population let all people think that these objects are associated with the merger of neutron star, neutron star and neutron star black hole in the sources of gravitational waves and a big observational proof of this scenario of progenitor will be to discover gravitational waves and a short gamma rebarst together. This is the model that explains their emission so independently of the progenitors what happen after the merger or after the core collapse is that we will have a black hole within a creation disk or in some cases we will have a magnetar so a neutron star, a very, very rapid neutron star in a very high magnetic field and we will have a relativistic jet and in this jet we will have internal shocks and these internal shocks can give rise to our prompt emission so to the gamma ray emission that I told you before and this emission last seconds less than two for the short and two 100 seconds for the long then this shock then we have this jet that interact with the surrounding medium and we have the external shock and this shock give rise to the afterglow emission and the afterglow emission is in hold we can see them in all the band optical, x-ray and radio and last hours, days and months so this is what happen we have this merger or we have a core collapse and we have before we have nothing in the sky then we have an object and this object disappear very rapidly and how much rapidly depend on the band we will see I told you before because this is an optical emission an optical images so we are searching for transient so object that appear and disappear in the sky with different time scales that depends on the band another important thing is the evolution with time of the jet so the jet this is the afterglow emission so the jet with time decelerate at some point is spread sideways here and so I think that I didn't told you later that the the emission is very beamed so when we have the gamma ray we can see the gamma ray only if the the jet point to us and this is true also for the for the afterglow emission but after a while when the jet spread sideways so when the jet decelerate and spread sideways we can also an observer that is not along the the jet can see this emission so you can understand that we can have also observer here not only on axis so some observer here can see the emission the moment in which the jet break give rise to this to this these are called like curves this is the flux, this is the time and the moment that the jet spread sideways we have this break in this afterglow emission and extremely important to see this because give us an indication of the beaming angle of this jet now I show you this like curves of flux against time for different observer so in this plot are on axis GRB so all the GRB that are observed along the jet and this is an afterglow emission and this is the optical this gray here are long gamma rebarst these here are short gamma rebarst I reproduce this plot here this is the region occupied by long gamma rebarst this is the region occupied by short gamma rebarst typically in the optical band these are the power so the flux is the case as a power law with time with time minus alpha and alpha is between 1 and 1.5 so these are on axis afterglow and these are long, these are short GRB and before I told you that we expect more binary system with respect to core collapse event so we expect more event like this associated to a gravitational wave with respect to these events we expect more short GRB so you can see that is really very important to observe this object as soon as possible this is one days in order to try to detect them here I put three telescope this is the paramatransient factory this is the VLT survey telescope and this is LSST Future Synoptic Survey these are I think some of the project that will look to this type of sources linked to gravitational waves these are large field of view telescope and you can see for example for pdf you can see that you need to observe this object as soon as possible so within one day in order to try to catch their emission the things became also more difficult in the case of axis GRB so far there is no of axis GRB observed and because for the on axis we are lucky, we see the gamma ray and we point the telescope so we see the gamma ray and then we point the optical telescope the x-ray telescope so we can catch their emission because we know where they are for the of axis GRB what we do is to make this big survey and try to find them so it's really also more difficult they are more faint and they are also more difficult so for the of axis these are model of aftergloss and again in the optical band and these are long this is the region of transition between long and short and this is a short GRB these have different features of beaming angle of observing angle so this is 0.3 this is 0.6 what you see is that this aftergl peak later and with respect to day one that I show you before are more faint so this emission is more difficult to be observed and we need to wait some days to observe this type of object so the gravitational wave we can consider it is isotropic the emission that I show you before is on axis this is an emission that we can see of axis and so we expect that more event associated to a gravitational wave sources will be like this because the gravitational waves we can see from everywhere the emission before we can see only if the observer is along the jet and here this emission we can see this emission from more angle with respect to the beam emission this is what I told the short are more weaker than the long GRB there are two reasons they are intrinsically weaker in both cases so you look here so this is the short, this is the long on axis in a contrary way so the short in the first slide when I show you the hardest ratio is something different is how the spectra is distributed because you have an energy that is more at high energy with respect to low energy that is something different here so in the first one you can see these are the long and these are the short so the short are more fainter and also here you can see these are the long and these are the short one so the short are more fainter so there are two reasons for this one is because they are intrinsically more faint and also because I told you before they are typically in the region where the density is lower and so another reason is that the density is lower so you have two regions for which the short are fainter I can show you so I can show you these these are the slide before this one this is something different because you have to evaluate how many photons arrive but also the energy of them and so you can have the energy depends also on how many photons you have so you have to integrate it over the photons so this is not directly linked to the luminosity and see that this one because they are more energetic means that you have more flux this means only the distribution of your energy and this plot I think is very useful to see this because all these GRB where observed GRB all bring to the same distance and so this plot really give you an idea of the intrinsic luminosity of this object these are what I told you before that these are what we see for long gamma ray bars so this is the afterglow emission and there is also the supernova emission and so what we see for the long GRB is this bump after a while, sometimes weeks or months and this is what was observed and the presence of a supernova was also confirmed spectroscopically because we see this type of spectra in the same position of the long GRB this is what we expect in X-ray this is what we observed on axis with swift and this is the model of axis these are only short GRB also in X-ray you can see the difference between long and short in terms of flux and here you can see that also in this case the off axis are more faint and peak later for the long GRB there is also another type of emission that is linked to the supernova so when there is the explosion of the supernova we can have the shock breakout that is typically seen in X-ray and also in UV and this one is a few thousand of seconds or long and so last for some days this is in the radio so I go back one second in the X-ray also for the X-ray you can see here hours so it's really very important to observe this object as soon as possible after the gravitational waves to try to see this type of object we consider the gravitational wave contemporary to the merger to the moment of the gamma-ray emission that is zero so the time zero is the time of the gamma-ray this is in radio in radio I don't know if you can see here but this is the radio band these are some model cores of a radio emission and typically the radio is after days after many days you can see here we are 100 days later so we lose the temporal coincidence with the gravitational wave event there is also some model of radio precursor so when there is binary systems there is this model that predict a radio emission a bit before the merger that for this dispersion you can see a few minutes after the merger but in reality people expected many events like this because you can typically see these events at low frequency but up to now so far lofar didn't see any of them there is also calibration problems with lofar so about this I think that we need observation to confirm or not confirm their existence so about short GRB I told you that the short GRB are the most promising sources associated to gravitational waves so far we have 100 short GRB the number of long is higher and for them we know the distance for 20 more or less they are typically the median reshift is around 3 giga parsec the most nearby was at 500 mega parsec for us is really very important to try to understand how many gamma ray burst inside the LIGO and VIRG horizon and so what people do was this is to take the distribution of GRB observed GRB these are on axis GRB and to this is swift to extrapolate to a fermiol skaj monitor and to put there the horizon of LIGO and VIRGO and we use the we expect that the short GRB is associated also to neutron star black hole so we use the horizon of neutron star black hole and what you can obtain is that we expect 0.3 short GRB per year when LIGO and VIRGO will be in full sensitivity for the neutron star neutron star range or 3 short GRB per year for neutron star black hole so these are on axis GRB so GRB that point to us and these events are rare but they are very important because these events allow us to make important study one of them is the one that I show you at the beginning if these events are for example neutron star black hole we can try to constrain the equation of state of neutron star and this study of mazelje panarale show that only for some parameter space you can have the electromagnetic emission and in particular when you have a neutron star and black hole you can have the electromagnetic emission and when you have a ratio between the mass smaller than 3 because if the ratio is larger than 3 what happen is that you are not able to create the creation disk that give you the jet because the neutron star is captured by the black hole and you have no time to make tidal destruction and create this disk and this is also linked to the spin higher spin allow you to have an electromagnetic emission because higher spin means shrink the last stable orbit nearby to the black hole and is smaller with respect to the tidal disruption orbit and in terms of equation of state of neutron star if you have an equation of state that is more stiff you have a larger radius for your neutron stars and so you have a larger possibility to have an electromagnetic emission so looking at the electromagnetic emission in traditional ways on the basis of estimation of the mass of the speed you can try to because these works show that you can put constraint on the equation of state of the neutron star other work that you can make with this type of object so on axis is also cosmology that this is possible with LIGO and VIRGO because this event you see are very rare so it is impossible to have large sample for this type of study but what happen is this that you can have two ways to estimate the distance because you can have the distance from an electromagnetic point of view the distance of the galaxies of this object and so you can have the the dash shift and on the other side you have a totally different way to estimate the distance that is from the gravitational waves itself and so this allow you to make cosmology but you need many many events to make this and so LIGO and VIRGO I think we will not be used for this even if there is article that say yes it's possible I think that the third generation of detector yesterday I didn't tell you about this but there is a third generation of ground based detector our only project one of them is the Einstein telescope will give an improvement in sensitivity of a factor 10 with respect to the advanced LIGO and VIRGO and this means a larger number of these events and so with ET would be possible to make cosmology with these events so this again these are on axis GRB we expect more of axis GRB with respect to on axis so use them as standard candle with the afterglow more than the afterglow is the prompt mission there is this hamatic correlation that try to make this but in this case you can use them and in this case the standard candle come from the gravitational waves and so you can use and the most easy way to these are at the hand are nearby GRB and so we think that it's easy also to find the galaxy and so have a good estimation of the ratio through the galaxy that I told you yesterday bit that now people try to estimate the number of gravitational wave events using the number of GRB so GRB observed on axis so if you have if you take the number of GRB observed on axis you can evaluate the number of neutral star neutral star merger if you know the beaming angle so if you know well the beaming angle you can extrapolate, you can evaluate very well the rate of binary systems and the problem is that we don't know the beaming angle for the short GRB we have only 2 observations 2 estimated that come from the observation one is 7 degree, the other is 14 degree so we don't know really the beaming angle but if you assume different beaming angle so this is an isotropic emission this is a beaming angle of 10 this is another type of emission that we expect from a binary system so during the merger what happen is that we have a significant mass that is dynamically ejected so we have a significant mass that is dynamically ejected at subrelativistic velocity and in this matter for neutron capture we have very heavy element that decay through stability they hit the material around and when this material is enough expanded we can have this emission similar to a supernova emission but with a different time scale and with a different luminosity that is called macronove or kilonovi and it typically is a transit of a few days and I show you the light curves expected for this object and when this material is interact with the surrounding medium we can have radio remnants so very similar to the supernova events but with different energetics this was the first simulated light curves for this type of object you can see here different model this is I think a black hole black hole and all these three are star and these are neutron star so in this model you can see that we have the peak of the light curves after one day more or less and this simulation used an iron opacity so the heavy element are in this case iron and the simulation also indicated that the element that forms through neutron capture are more heavy than iron and so now we have more realistic simulation of this object and taking into account so these more heavy elements what happen is that this is the light curves and this one is the light curves for heavy elements so these objects are a bit more faint and peak a bit later after more or less eight days and the emission this is iron this is more heavy than iron and the emission is more in the infrared than in the optical so we expect more infrared emission than optical why I told you about this object because this emission is isotropic like the gravitational wave and so we expect that the majority of our gravitational wave event will have this signal associated so in 2013 there was a first observational evidence is the only one of a kilonova so these could be the first kilonova observed it was not confirmed by other observations so we are waiting for other observations like this what happens was this that there was a GRB and with AHST people observed this GRB after few days and after nine days they don't see nothing in the optical but they see a transient in the infrared so if you look here this is the X-ray afterglow this is the optical afterglow and these are the point observed in the infrared so in the infrared you have this point here and this point here give you what we expect as afterglow and there is a point here that is the HST point so this one is impossible to be explained with an afterglow emission because the power law is this one and so people say this point can be explained if we assume a kilonova emission these are two like correspond to a different mass for a kilonova emission so this point is maybe the first evidence of a kilonova emission but was seen only in this GRB so we wait for other of this event because now we have only model of kilonova so to constrain the model for the radio these are what we expect from the simulation of radioremnant coming from these events but what you can see from the radio is that these transient event are after many years so 2, 5 years 1.55 so it's really in the radio it's really very complicated to associated our gravitational waves with the radio emission because we lose completely the temporal coincidence with our events so to summarize we have the gamma ray beam the emission in the gamma and these last seconds it's impossible to discover a gravitational waves and ask to the satellite to point in the direction of the gravitational waves because these emission last seconds so in this case we developed an analysis that use the electromagnetic information so use the information coming from the gamma ray to focus the gravitational waves search and on the other hand the GRB after glow emission the kilonova are emission that are expected hours, days after our event our gravitational wave event and so we developed a program that is called electromagnetic follow up program in which we try to discover the gravitational wave and send alert around the world to the optical telescope or the x-ray satellite and we ask them to observe to try to find this emission for the radio I told you that we lose the temporal coincidence so what we do is to try to make a high latency follow up so to make observation after weeks or we can use something similar to this one so we find the transient in the radio and we look back to our gravitational wave data to see if in the same direction there is something in the gravitational wave data so we start with the first type of search in which we use the electromagnetic observation to focus the gravitational wave analysis what we do so what we do is this we use the gamma ray bar time and the gamma ray bar sky position and we fix these in the gravitational wave search and so these allow us to reduce the parameter space of our search and so to gain sensitivity we make this search for the model and also for the compact binary coalescence this is the place of the trigger where we make the analysis and here and here we estimate the background we studied about 200 gamma ray bars in this way and we didn't find any gravitational wave associated to them these allow us to put upper limit on the distance of this object and you can see here that these distance are very nearby and this is the reason why we didn't discover any gamma ray bars because these gamma ray bars are all at a higher distance with respect to this value so we make also some population study on these these are the cumulative ratio of distribution of our upper limit the one that I showed you before this is the region occupied by the observed GRB and the same for this, this is a model search this is a binary system coalescence search you can see these are two plots one for neutral star, neutral star, this is for neutral star black coal this is what we were able to do are very distant with respect to the observation in this case and in this case this is also what will happen in the future in the future we will have an improvement in sensitivity of a factor 10 and we will have also more GRB we can use for example two years of observation of the satellite and what you can see is that these curves come over here so this means that it will be possible to make a detection or in any case to put important constraint on the GRB model these are other type of of study that we we do, we did with the initial eigen virgo on some specific event, on some single event so there were two gamma ray bars that exploded in the same region of nearby galaxies one was Andromeda and the other one AM81 and so some people thought at the beginning because we didn't know the reshift of this event, that this event were gamma ray bars in these two in these two galaxies and in this case gravitational waves help to understand that this event are only background event or are not GRB because no gravitational waves were detected from these two galaxies and so we were able to exclude the presence of a GRB in Andromeda and the AM81 so this gamma ray mission could be compatible with something different with respect to a gamma ray barst that could be a soft gamma ray repeater for example or also these GRB are background GRB that are only in coincidence with our galaxies but not belong to AM81 or Andromeda so the use of the electromagnetic information to focus the gravitational waves search can be done also in not only for GRB but also for the soft gamma ray repeaters so if we see soft gamma ray repeaters in X-ray in gamma we can use this information to make the gravitational waves search the main problem is that in these cases we don't know the energy emitted in gravitational waves for different model so we have many, many order of difference so the energy go to 10-4 to 10-9 but in any case all the event that we see as soft gamma ray repeaters will be used also with the advanced Lagoon Virgo to see if there is a gravitational wave this can be done also with the pulsar glitches in these two cases what give rise to the gravitational wave is the pulse after this event that we expect from the object these are magnetars and these are neutrostars these are the glitches people think that glitches are linked to Starquake so we go to the second type of search the one that use the gravitational wave signal to ask to the telescope to point and to try to detect the afterglow emission so the first we did the first electromagnetic follow up in 2009-2010 and what we did was this try to identify gravitational wave events in real time and obtain prompt observation so Lagoon Virgo observe the sky and there was this search algorithm that try to identify as soon as possible gravitational wave trigger they select the more significant respect to the background and they ask to the telescope after a human event validation so there were some people on duty that evaluated the performances of the interferometers and we send alert to the electromagnetic facilities and all this was done in this process the software part takes about 10 minutes and then in 30 minutes we were able to send alerts to the telescope for the advanced detector here we expect to reduce these 30 minutes to more or less 10 minutes so we will send alerts in 10 minutes to the electromagnetic observatories we will try also to reduce this time because I show you before that these are very fast event in some cases so it's important to send alert as soon as possible to the satellite and to the telescope at the ground the main problem is again the sky localization because we need to say to the telescope where they have to point and yesterday we saw that the sky localization is very poor in gravitational waves in the first electromagnetic follow up this is an example of sky localization and in this case we expect low signal to noise ratio events we had 200 square degree or 300 square degree to see yesterday there was a question on the sensitivity why the sensitivity I think the guy there on the sensitivity why the sensitivity is square root of the number ok, this is the reason, this is formula this is a simplistic formula because you assume this is the network signal to noise ratio and you can see these are the three interferometers so if you assume that the three interferometers as the same sensitivity and as the same sensitivity and also a Gaussian noise you can write this like n sigma sigma square and so is like square of hand this is the reason why it's clearly a simplistic thing because you have not a Gaussian noise at the hand is a distance ok, so again the sky localization is 100 square degree but we don't have really telescope with a so large field of view these are all the telescope that participate to the first electromagnetic follow up and you can see here their field of view so we have for example quest that has a very big field of view of 10 square degree but not 100 we have one that have a very big square field of view of 400 square degree but has not a good magnitude so we need to find very faint object and we need to have very big field of view and there are not this type of instruments and so it's important to develop observational strategy for this telescope and in the past follow up what was done is not to observe all the error box of the gravitational waves but to look at the galaxy so we know what is the volume observed by Lego Virgo so instead to look everywhere we can look we looked at the galaxy at the region occupied by the galaxy this was not so difficult in the first follow up because the horizon was not so big but you can understand that going to larger and larger volume the number of galaxies increase so you can try to find some prior in the galaxy but going to larger distance this type of strategy became more difficult so these are the event that we sent to the gravitational wave event that we sent to the to the telescopes and we observed 8 gravitational wave alerts optical telescope to alerts with swift, some in the radius and I have to say you that we have this low latency search so a search that is very rapid but after this search that is very rapid with the gravitational wave data we make also a deep analysis that precise also in the evaluation of the background and these longer and deep analysis show us that no one of these event was really gravitational waves but all of them were compatible with the background and also from the electromagnetic point of view in this area were compatible with the background so the background of transient in the electromagnetic part but this was really a good exercise because show us all the challenges of this type of search so what we have all have to deal when they try to find this object is so object that as I show you before appear and disappear in the sky very rapidly and so you have to take multi-epok images you have to try to follow the like course and another big problem link to this very big error box is that you need to analyze very big images and in these very very large images you have many many contaminants so you have many transient that are not associated to the gravitational waves so you have to find one event over a thousand and thousand transients and the main complicated step is so to remove the contaminants and how you can do this this can be done by a very deep knowledge of the transient sky and what you have to do is to in a very quick way using different things like course, color, shape try to remove all the things that you know that are contaminants and I show you what are the contaminants so the exploration of the this is in the optical the exploration of the optical sky started very recently in the last ten years we had very big improvements this plot was mainly fill-in by the Palomar transient factory they discover all these objects these are time scales of days and these are the flux, this is the region expected for the kilonob the contaminants for our gravitational wave counter part are mainly galaktic we have asteroids emdor flares cataclysmic variable variable star and also background A, G, N and supernova asteroids are the more easy to remove because they move in the images so if you take multi-epok images you see some object that move and you can remove them the main contaminants that I put here some number in ten square degree you have if you make the sum of these two you have so 100 contaminant transients so they are a lot and in many many square degree, in hundreds of square degree I have to say that they have different time scales because the emdor flares have case of minutes hours the supernova days months so if you are able to follow the light course for long period you can discriminate in this object but the problem is that you are trying to find something that is very fast that is a very short time scale transients and so you need to remove this event in few hours so this is the problem in the optical skies the main problem are these objects in x-ray and in the radio the situation is better from the point of view of contaminants it is more empty the sky in radio and x-ray and so it is you have really less contamination here I put some number but you have other type of problems in x-ray we don't have large field of view the most useful x-ray satellite that we can use for this type of studies swift that has arc mean field of view so you have arc mean field of view to image hundreds of square degree so the problem is the field of view in this case it is smaller with respect to the optical you can make mosaic but it is really very hard and the people are thinking to use this galaxy targeting strategy with swift in radio we have very big field of view also for order of 50 square degree but in radio the problem is the temporal coincidence or that the radio mission is not coincident with the gravitational wave emission and so we don't know when we have to observe and so we cannot observe the sky for weeks weeks and weeks up to here so I think the optical can be one of the most promising place to try to find and if we will have some large field of view monitor in x-ray would be also better than the optical advanced era what will happen yesterday I show you the full sensitivity but to arrive to the full sensitivity it will keep some here and these are all the steps to arrive to the full sensitivity here you can see the the improvement in the average distance for neutral star neutral star binary and we expect full sensitivity around 2019 more or less so 2019 we will have the full sensitivity sky localization the sky localization will not improve because improve a lot only if we have another detector and these are the big improvement that we will have and we expect around 2022 with in this case there is kagra and so we can also reduce this error box with kagra so for many years from now to 2020 we need to deal with error box that are of order of tens to hundreds of square degree this is a table that summarized the observing scenario from now to 2020 here are the estimated round duration so this year we will have 3 months of science observation with LIGO, only LIGO in 2016-17 we will have 6 months of LIGO and Virgo will join LIGO and then we will have 9 months and so on here you can see the maximum distance for a burst this is a maximum distance for a binary system and these are the expected rate with big uncertainties from now to 2020 and these are the percentage of binary that are localized within 5 square degree and 20 square degree for all these here, so big improvement only when we will have a four detector this block show more or less the number of expected binary neutron star in the next years and I think that a promising year will be in 2017 this is a link to this year a work on what will happen with the observation in 2015 people are trying to use all the information also to try to improve the sky localization also with only two telescope and so there is this software called BISAR and BISAR make the sky localization using the triangulation but try to use also try to evaluate the consistency of timing, phase and amplitude in the two interferometer and with this they are a bit able to improve the sky localization in 2015 they expect 500 square degree as median so I told you yesterday after this detection search there is also a full parameter search and so obviously if you are able to find the correct parameters you will be able to improve the sky localization and with only two detector use these faster sky localization code this parameter estimation code doesn't help and so you can see that the blue and red line are not give the same results and also if Virgo will be in 2016 Virgo will not have a good sensitivity so also with Virgo but with a not good sensitivity the presence of Virgo will improve in the case of parameter estimation code will improve the sky localization and we will have a median and it is very important that Virgo will be online the next year the full parameter estimation is now taking some hours to be run but people are trying to reduce a lot this time this computational time so a similar work was done also for Barst event so what are the challenges of these type of searches we need to find fast transients we need to deal with very large error box that are difficult to be covered by the telescope and there are many contaminants and we will have larger volume to observe and so I think it is really very important that gravitational wave people are magnetic so astronomers but also the theoretical community can help and try to identify in observational strategies the best one to try to find this object so what can be one of these strategy is a so called hierarchical search so first of all we need a very wide field of view telescope that run over this very big field of view we need very fast and smart software that are able to rapidly classify the transient and exclude the contaminants and then we need to use the more expensive telescope in which it is very difficult to obtain time of observation to characterize from thousands of transients to ten candidates and thus a larger telescope to observe them and study their nature and try to find the electromagnetic counterpart this was done by the Palomar transient factory they proved that it is possible to this type of search what they do so they follow the gamma rebars observed by Fermi the gamma rebars observed by Fermi have error box of order of seventy one hundred square degree so Fermi so in the sky this gamma rebars and with this optical telescope they try to monitor this region observed the error box of Fermi they use machine learning software to remove the contaminants on the base of the shape of the color of the presence or not of object before in reference images and they were able to discover over a sample of thirty five GRB eight optical afterglows it's true that the gravitational wave error are bigger these are all long GRB afterglows so we expect of axis GRB we expect fainter object but this was a great success of pdf that showed that this is now possible in the past this was not possible because really help a lot the use of this very sophisticated machine learning software but so it's a challenge but it can be done another thing is also in the removal of the contaminants a galaxy targeting can help so if we can find some priors in the galaxies link I don't know link to the star formation rate link to the mass of the galaxies that allow us to identify the most probable host of the binary system events we can also look only on the region of the galaxies to allow help us to reduce this very bigger box and to reduce the contaminants events this is a big of policy of the LIGO and Virgo collaboration decided so the LIGO and Virgo decided to release alerts not to the broad community not a open release of this alert but the alert will be send only to the groups of astronomers that signed a memorandum of understanding in agreement with LIGO and Virgo and this will happen for the first four events so these four events are event that will be gravitational wave event only on the basis of the gravitational wave data after these four events there will be open release of gravitational wave alerts so everyone can observe these alerts and so we had to call for participation in this program and one last year, one this year and now we have about 70 group, 70 institutions that signed an MOU with LIGO and Virgo for these signs we have about 150 instrument that cover all the spectrum from very high energy and that we receive alerts and that will follow the alerts to try to find the counter part these are the last slide in which it's a bit of summary in which I say that in optimal observational strategies what we know about GRB and also theory can help us to develop a very good observational strategy from the point of view of the gravitational wave for example it's very important to have very good waveform from the binary system from the theoretical side and gravitational wave and photons will be necessary to probe single events like GRB, kilonovi, supernova, pulsars at the same time they will be very important to study, to make statistical study over population of this object and for example to know rates, distribution, demography of compact object and this will put, will allow us to constrain model of burden devolution of compact object and for this event to study really for example as I showed you before as I told you before the equation of state of neutron stars but it is also true that if we open the gravitational wave observation we expect also exotics or season also maybe new physics these are some open questions but ultimessange study can answer first of all if a short GRB is really associated to a binary system, what is for example the beaming angle of a GRB if the kilonova can explain partially the presence of heavy element in the universe and so on, equation of state mechanism of explosion of supernova and last slides in which I show you the progress of the, so this is the LIGO LIGO is in a phase in which all the part for the advanced are putting together and the first science run is in 2016 and this is a plot of LIGO taken a few days ago and so these instruments was first log Living Stone in May and Lie and M4 in March and log means that they stay they observe the sky, not in science run but they were able to observe the sky for many hours and the sensitivity of both of them surpassed a lot the initial LIGO in Virgo and you can see here at what distance they arrived few days ago that are around 60 MPa so we are really LIGO is a very very promising because it's also more than expected for September we will have the first science run with LIGO and so this is the last slides that I think is very important because you can see that we can really start observation of a large volume of universe