Marcella Wijngaarden – Speckle Interferometry as a tool to distinguish binary stars

is also low in garden from the University of Amsterdam and she will talk about going apparently so everybody reads my salon I see my slides okay so okay it’s yours okay thank you for introducing me I’m very happy to be talking to you all the way from Amsterdam and to be part in this wave of the conference I hope you’ve been having a very good and interesting time so far so as what I mentioned my name is Marissa and I had and I study and work at the untold one who Institute for astronomy in the Dallas and today we will talk to you about speckle interferometry for binary stars for patients and in particular about the technique of full of furniture speckle interferometry so let’s begin with a quick overfilled to talk i will start with an interest introduction i will give a few reason on why reasons on why we should study binary star systems what are they interesting and then why speckle interferometry is a good technique to do this then of course you talk about what is speckle interferometry which is goes through some theory and also observations data reduction and calibrations and all end with showing you some of the applications and also i’ll show you some of the applications that we do at until particle Observatory where where I work so why study binary stars I heard that some of you are already interested in binary stars so I probably won’t have to convince you too much soda sculpture is quickly the first reason in my opinion has to do with stellar evolution models and they’re off often visualized as inherits from Russell diagram as shown here on the slide where you see the luminosity and that temperature of the stars and this shows how we think how stars evolve to time and one of the most important properties to derive this and to describe these evolution is Tomas of the stars and the most of the stars can only be determined by analysis of binary star orbits so it’s very important that we have good up to patients to dusty’s models and also it’s actually for the most common starts in our universe and for massive OB stars the mass is still not well known and it is actually one of the open problems in that in modern astrophysics so the next reason why binary star systems are interesting is because it’s very important role in many theories of interesting extra physical processes for example though they are the originator of type 1a supernovae also interesting processes neutron star accretion which happens in binary star systems they play an important role for black hole formation and also mutant store information you can see an example you’re on god you’re on the slide also which i think is an important issue there is a big lack of observational data of binary star systems so in our are over a hundred thousand systems in the Washington double star catalogue the WDS which is the largest one of the largest catalogue for multiple star systems and only of the order of about 100 systems of them have grade 1 orbits and grade one orbit just means that the orbit is very well this friend so we have full coverage so there’s much data needed and also to complement space missions for example we have the Gaia mission that one is first data release this year but to describe binary orbit we need good time come first so we still even even with the space missions we need observations from earth-based telescopes so these were a few reasons why we should study finally star systems and now let’s talk a little bit about why is speckle interferometry is a good technique to do it and in order to do that we need to talk a little bit about what limits the resolution of our telescopes because providing store

observations you want to have the highest resolution possible so you can distinguish the closest binary stars possible for your system in a probably all familiar with this but we’ll just go through it quickly the first limit is of course the diffraction limit and it is determined by the size of the telescope and this limit arises because light will get diffracted at the edges of your telescopes as shown in these pictures as well and for larger telescopes the for larger apertures the fraction of the total incoming light that gets deflected is smaller and just a higher and there’s a higher resolution is possible another way to think of this is that ratio of the edge of the telescope to the total size of the telescope aperture is smaller so of course less of the light gets distracted then secondly with for all earth-based telescopes we have the single image and this is set by a masseur distortion and we’ll talk more about this in a minute and this is actually the most constraining limit for larger telescopes alright so the ceiling limit is set by our hemisphere distortion and this just means that as the light comes in from an infinite distance as shown inspector it can be regarded as a playing way front and a plane wave one just describes all the points where the incoming light has the same place but as it grows goes through your atmospheres the wavefront that just gets distorted as can be seen in this picture and this is because the atmosphere consists of small packets of air that changed the face of the light different day and these air pockets in the atmosphere change on a characteristic time scale which we will follow t0 and we will come back to this time school while we discussed a technique to offer complete sentence your artifacts so let’s have a look at how these limits on resolution of our telescope look like in pictures here you see on the left a short exposure image with a small telescope and when I say small telescope in this case I mean a telescope of about a dying leader of 10 centimeters so really small and you can see that for a small telescope diffraction rates will form around the central peak so we can see clearly that the diffraction limit is ruling here in the middle you see a short exposure with a larger telescope and larger just means that its larger than 10 centimeters and you can see small dots and these are called and hope it’s clear friend for everybody in boom but these are called speckles and they are the result of the incoming light going to the different air pockets and just landing on different places on a detector and it was on the right you can see how longer exposures just a combination of all these speckles and results in a blurred image so you can see from this picture that we do not reach the theoretical diffraction limit of a telescope if the telescope is larger than 10 seen in centimeters because of atmospheric effects and this is very unfortunate if you want to distinguish binary stars and this is where as speckle interferometry comes into play since strike wanted from 83 is a technique to overcome in clearing facts of the Earth’s atmosphere so what is back 12 from three let’s start but how it works and how you can and how you can use these techniques the basic idea behind speckle interferometry is to take multiple short exposures usually would take about four hundred frames with exposure times that are smaller than 10 milliseconds and I smaller than Sydney seconds because this is the variability time scale of the atmosphere in in the visible light so the idea is that in these frames you actually freeze the atmosphere so that it’s no longer changing with a design that image taken so in all of these prints we see multiple struggles and the idea is actually get the most occuring separation between these speckles represent information about the components of the binary systems and we can use them a statistical analysis on all the form of 400 frames to retrieve the most important information to describe the orbit and this is the position angle between the components and the separation between the components and this is the big this is just a very basic I even the technique and I hope in the next few slides it

will become more clear because you really understand what is going on you need to go to a little bit of math but it’s not important to understand the phone as completely as we go to them it’s more important what we can learn from that from them and how we can use them easily so each of the images i just showed in previous slides can be a spread expressed as a function which is shown here on this slide and this function consists of two components so you see the be there and that is the point spread function and this just describes how the light of the point sources is distributed across the image and this function is that involve convolved with a functions that describe the true intrinsic shape of the light of the objects and what is important to take away from from this slides actually that we take we assume the point spread function to be constant during each exposure so you assume that it doesn’t change out whether 11 exposure is taken so as I certainly assume that the atmosphere is not changing within that time and this is actually the reason why we need to take such short exposures ok so to simplify the calculations we do a trick that to usually do if you want to simplify complicated calculations we transform or our functions to free a space because in free space we have a multiple multiplication instead of convolution between the point spread function which is now called the transfer function and the object function so if these are just the same functions as we saw before but with a capital letter with which cysteine notes that they are Fourier transforms ok so now you may be thinking that is nice of these formulas but how do we get to information from the binary system from from using them and we’ll just go through the simple steps so first it’s important to realize that for a binary image there are actually two overlapping object functions that we want to learn information about it on the left so it’s the same function as before but you’re letting out to object function so you actually have to open up inspect all products in your image the second step is to rewrite these dysfunctions in terms of the separation between the object functions in pixel space assist again shown on the left and it’s not I understand it’s a lot about you but I just put this format on for anybody that is interested i will post it and then take as mentioned before we take the Fourier transform too and so now we have a now an image that is described as a function that has both an entity data and face and for full purchase patent spirometry you’re just interested in there in the amplitude at first and we’ll take the square of this function because this can be easily related to a power spectrum which we will see in and makes light and notice here that we are we ended up with a cosine function and this will allow helped us today in right because here you see above you see the same function as before and we and by using the speckle friends of also a single calibration star and reference star and obtain the point spread function and use the middle formula that divides the average of the image functions by then average of the retina star functions and the resulting image you see below and this is called the power spectrum and here you see how the fridges how other finches with light and dark pants and these are described by cosine cosine function such as we are seeing above and it’s actually possible to obtain information how to binary components directly from this image but usually we go one step further and we calculate the outer correlation this is the last step predict so so we use the power spectrum to calculate autocorrelation an example of an algebra no Graham is shown in the lower right image and I’ll just explain what this means so the pictures above to two pictures above they represent the speckle frame and with the most boring

separation indicators so for the left image this would be the separation between the black and the white dots and then what you do is for when the separation and orientation for each of the pixels which each of the other pixels is calculated then we retrieve the picture so you see a central p and two peaks on the side and the two bright pics on either side of the middle they denote the most recurring separation and orientation okay so how do we derive binary properties from this diagram the separation between the two do two peaks so one on the side and middle peak is dead of the binary but I’m in pixel space so we have to convert them to for example our seconds and we done meet another place kill the system so we need to know how many arc seconds is covered by each pixel in a frame and in the same way you can dress to fit the position angle from the angle between the peaks of course then the image orientation must be known as well in order to wake know which way is north and east and so on in the image and I’m just like to emphasize your get this out of parallelogram is modern image two stars since for that we need information the face as well and we disregarded that in the batter’s earlier but there are also a little slightly more complicated methods to also retrieve the face and who should we will see examples from that later on and also what you can see here instead of Terry some 180 degrees and baby t and this is because the separation between two pixels is calculated twice one for each one time for each of the pixel and therefore we have two peaks on the other side of the central base but there but fortunately there are numerical techniques to overcome this problem as well so just a recap of the matter we started with taking a lot of very short exposures of we took the Fourier transform of those exposures as shown on the left panel they were used to calculate the power spectrum an average power spectrum and the power spectrum ones used to calculate two out of correlogram on the right below and from the auto program we derived the binary properties so this is it serially let’s talk a bit about some of our how to do these occupations and let’s start with some instrumental considerations so larger telescopes for spectrums of Rama tree produce smaller and we disks and more speckles but you need enough not open up their speckles in order to do the methods which is described so we need to use magnification techniques or shorter exposure times to get enough of these not of lapping speckles but in this way larger telescopes lose some of their advantages of course they still have better resolution but it’s not necessarily it’s now it’s a trade-off really between the size of the telescopes and this is actually what makes a spec wanted for three perfect technique for a mature size telescopes you don’t need a very large telescope and do not need a complex set so as I mentioned here already if is we need enough mum of weapons speckles in order to get them even for a mature size telescopes we can use techniques such as I PT projection so because what is this experiment you determine that it is best to have an airy disk size of about 10 to 3 pixels and in order to get death we can use projection techniques because this course increases the focal length of the optical system and with that you get a larger magnification as it’s also showing by the formulas below you see that effective focal a determines the size of the areas in its own formula and what modern form I can see that you can may have a larger effective focal length by using a an eyepiece I was going to discuss a little bit about the spectral set of the reappearance on top one loop and I instituted is shown here on the slide now but in order to stay in time I think it’s best just to skip ahead but if anyone’s and anybody’s interested I’d be happy to explain more about this

later and then move let’s move on to the data reduction because more most important things we already discussed in the cheering section but an important thing is that the quality of the result have we realized on that how well the image is calibrated so we really need to know the image skill and the image orientation of your system when our several methods to do this perhaps you’re familiar with them one obvious one is to use calibration quite fair so use final repairs with no separate separations a position angle and we use these images to calibrate the place of the image orientation another weight could be to use treat analysis so you have a single star on the side of your image and switch of mount motor and analyze the star trail and you can derive which way is east to west for that so of course you can write your own reduction routines based on the theory but i want to mention here that there’s fairy who software available and very easy to use and also free software so for example rated by for loss there’s place of tree that is a slightly more professional and we’re several pointing routines um and I would encourage everybody to give it a try because this this software I’ll they do all the cheering steps for you so you just have to do to patients and make sure your system is well calibrated and then you can use the software to easily retrieve them by the Bible store information from that so some applications of course the most obvious one is that at least in the in the in this stock is that they can be used for binaries for refining when we store or this here on the mess you can see an image of an orbit from taken from the WDS catalog where you see it into blue dots they represent spectral measurements and the spectral measurements are really one of the best quality measurements that are new chanel for binary star orbits and they are used to refine these orbits in there are no me and they are the use both amateur and professional data this is really a field where both play an important role so as I mentioned earlier week by the techniques we described we didn’t retreat an image but there are also techniques we can retrieve the face information maxcom Thompson techniques there call and I just wanted to show you a very nice example of this that I found on the Internet where you’re on the left you see in here you see the speckle frames and you’re on the right in a smaller image you see the reconstruction of the image and you can really see two small components appeared in wouldn’t imagine maybe initially that from these frames you could get such a high quality diffraction-limited image yet to enter it I wanted to show you this picture of our Observatory it is located very near the center of Amsterdam and you can see it’s a horrible sight to do astronomy there’s we have a lot of light pollution and sorry that seeing and the point that i am i showing you this picture it is really to encourage you because if we’re a good spec when spirometry and this such a bad side we were able to do a good quality segment of roma three observations binary star observations so if we can do it here you will probably have better conditions in another place so you can definitely use this technique so yes as I said we have that seeing and a very bright background one of the things that we are currently doing is we are trying to set up a semi semi automated spectrometry program that’s going to be used for student occupations and the students from the University of Amsterdam can actually contribute with their observations to binary star science so just to compute with a speckle interferometry is a method to approach the diffraction limit of your of the telescope so to overcome really the

seeing and I’m certain facts it’s a matter that is accessible to both professionals and amateurs there’s no there are other methods that overcome the seeing such as adaptive optics but they are nearly expensive so this is really a keeper way cheaper alternative that’s going to be used by more people and there are a lot of interesting applications possible I don’t know who I am in time so if we have enough time if we have a lot of time for questions but I would really like to encourage everybody to contact me I put my email number on the slide and I’d be very interested to hear what you were thinking and maybe if you’re interested in using these techniques I’d be very interested as well so thank you for listening this was a salon picked up thank you very much a little bit hey you are perfectly fine so I’m getting a few mins for possession and questions Margaret Mary question because of waka flocka the you mentioned that there are optimal I would say that is possible to measure this technique end up with a motorcycle instruments is there it’s something like an optimal combination of technical parameters like shuttle sorry sorry sorry I love a yak I mechanize work i cannot hear you in there well could you repeat the question a little bit louder okay you get me out oh I know yes not okay my question of Esther is there something like an optimal over meeting room combination of physical leaders of another instrumentation life then it’ll objective lens and focal length pixel size to get the results because magic because version that is that these techniques within the reach of your mother yes yes definitely yes so there’s been a lot of experimenting with different setups and different parameters but really it often it depends on the system that you want to observe for example for wider binaries and you can use smaller every disks is better to be smaller it early days then for smaller for closer closer wineries but often with amateur systems and also actually with professional assistance you are limited to the instruments you have for example you put very the distance between the camera and the IPS to change the air Egypt’s eyes without using different I pieces um but then you need a system where you are into I should change that she had changed that distance and often it is not possible possible YouTube yeah limits of the instruments that you are using but there’s no one optimal distance known because it depends on the separation for example of the binary but also the brightness opto binary and also the if they are if they have the same brightness or if one is much brighter than the other and then that effects what would be the optimal systems you observe with other other animals I answered your question if there is any published there hello hello this work sorry so my question is if there is any published source of information how we can derive okay parameter power system due to achieve a certain level of precision go to the Bible fight me okay yes very good resource for this would be the giant double star to patients and there’s recently Russell Jenna wrote a book about this and if if you want I could provide some of the articles that are about these subjects and also some of the books and from sin time I could send you the links if you were interested just a let me know why your email address and meeting on than that will get it yeah we we have your address sins

yes movie room okay great no sorry Christian yeah hello this is on an hour pity oh you spoke about Gaia and its data but you’re still interested in even more powder from from Alan I say something the last five months coming true yes ok everybody is foldable guy about us and you need more bad as people from other there are you going to create some kind of program to leave on others what star they should observe that’s actually a very good ID and it’s mostly i’m not sure if there are any there are already some groups of amateurs together with professional astronomers that talk to get together by what I sources to observe but i’m not sure if there’s one why yeah one source of this information of course it are often done the white binary so with large furious that needs all so much data for managers because guy won’t have the full coverage of their out of their orbits but if if you’re interested that i will i can also send information about what are good sources to observe to anybody actually very single stager I would be happy to do this may I have one more question first and I refer to the channel 9 watt before so if you combine type of stars to be observed with need agreement size of telescope authoritah then that would guide our girl 22 in the decision but the two okay you mean as information about how to set up your system where you can find this yes you explained that depending on the distance between the buyer if you need different equipment oh no um not necessarily different equipment sorry you can you can use the same equipment to observe both systems but the question before I think was what would be the optimal configuration of your system and it would slightly it would be slightly different depending on both cases but even so with the same system you put observe both boat just both separations okay thank you already are Christians oh this author speaking thank you for very interesting speech my question is if I will inspect in your mouth is developed for distinguishing of two stars but in area of eclipsing binaries us with some bad means to this English plant or distinguish if the particle stars1 are there get any mod developed to use this technique for for searching for some walls of the energies or even instinct yes so so it just it is more for changing of course but the man also applies for other types of sources for example it can be used also for extended sources in a way that they use multi some multiple point sources energy just to describe an extended source and it could definitely be used also for multiple system for multiple components or more than two definitely yes yeah I explaining well I don’t mean any more than two sources I mean decision whether the observed star is the is it a wall single there is one okay yes it is it is actually speckle interferometry is also used in DD to discover to test single stars for if there are two virus or

multiple star systems yeah just get there this is also an application for this technique went to say Matt actually thank you okay any other questions maybe I upon if you are so short it for Yasur news and was the money people image you can reach if you’re ugly Tedesco quickies very short people yes yes okay so we are we are still pushing our limit but what we have observed we not have a meter telescope the limit is really is really ate a blanket but also your it is important whether the two starts at the same rightness or different because if they have the same brightness we can go up to we have we can go now up to 10 but if one of them as magnitude done and the other has magnitude to then it becomes more difficult because now we then it’s harder to detect the dimmer component if you have any other questions so you like to thank you very much for interesting broken thank you well and again I want to thank you as well and I hope and you will contact me because I’m very easy to discuss this further and I think that at least poop yes very good so Evan I say goodbye yes the same enjoy the conference thank you