- So our next speaker is Adina Feinstein. So Adina, if you can share your screen. And she will tell us about HST/COS observations of AU Mic, Flares. And Adina I will give you two minutes warning before the end of your 12 minutes talk. Thank you.

- Great, thanks so much. Can you hear me okay, and see my screen?

- Yes.

- Oop, spoilers.

- Great. Hi everyone. My name is Adina Feinstein. I am a fourth year graduate student at the University of Chicago, and today I am hoping to convince you, that if you go after these really young planets and you see a flare in your data do not like roll your eyes and be like, "Oh, another sign of solar activity, something in the way." But really there's a lot of really interesting science that you can do with these flares. And so just to motivate this a little bit, I'm sure a lot of people here are familiar with this period radius diagram. What I'm showing here on the Kepler distribution of planets in the contours, which tend to be older planets. And what's really interesting now is all of these discoveries of new young planets. So I've highlighted a few of those here in the yellow points. And these planets are all less than 300 million years old. What's great about these planets is that they occupy this really sparse region of period radius space. You can see the background in that region is quite dark. And what we believe is gonna happen is that their radios are gonna evolve such that they will eventually become part of this more densely occupied region of Kepler planet space. Now, there are two main current working theories about how these radios can evolve. And what's great is that they work on two different timescales. So the first one is photoevaporation, where you are having these young planets be very close into their host stars, which tends to be really active in the SUV. And so photoevaporation of their atmosphere is just from this high energy radiation, and that tends to operate, we think on timescales about less than 100 million years. And then we also have the second theory of core-powered mass-loss, where after these planets have formed, their cores are really quite hot. And so the radiation from the core can also cause their atmospheres to erode over time. And that works on timescales of about a billion years. And so for going after transmission spectroscopy for these young planetary atmospheres, you're really gonna wanna see, where is the mass-loss the fastest? What is the highest mass-loss space that you can get as a function of age? And so, that really motivates the observations that we're taking here. And I wanna highlight the system that we're looking at. And so, TESS I'm sure we're all aware of the Transiting Exoplanet Survey Satellite has really played a major role in increasing the population of young planets that we have today. So this is just the most updated image that we have so far test sectors, one through 44 from Ethan cruise. And so, because it's an all sky survey, you're really able to get planets and stars of all ages, and look at their light curves and try to find new transiting exoplanets. The system that I'm going to be talking about today is AU Mic b & c. And so AU Mic is a very well known young star . It's about 25 million years old with a debris dust that recently had two transiting exoplanets found around it and test data. And so I've highlighted those here, with the transits of AU Mic b in yellow, and AU Mic c in green. Now, for those who are unfamiliar, looking at young light curves, you can look at this and have a bit of a headache 'cause it's not the nice flat light curves that we all might be used to. There's lots of beautiful spot much relation, and there's also lots of flares. And so what I'm showing here in this new light curve are the test observations, now colored, by if they are not credible flair, where the flares really light up in yellow. And so there was a great paper that was recently published by a co graduate student of mine, Emily Gilbert, that looked at the flare frequency distributions for the AU Mic light curves, where she found that in sector one of these observations AU make flared `had about 1.8 flares per day, and the most recent sector had about two flares per day. So really if you're going after your transits of AU Mic b & c it shouldn't be surprising that you would catch a flare or maybe more. And so as an overview of our observations, this was a Hubble program that was led by Wilson Collie. And the goal was to observe three transits of AU Mic b using the cosmic origin spectrograph from wavelengths about 1060 to 1360 angstroms with a mass climate alpha line. Cause it would be too bright. And some of the spectrum that I'll show later on, there's going to be a gap, and that's just where the lime and alpha line would be. What's great about the cosmic oranges spectrograph is not only do you get the wavelengths dimension, but you can also use create Lakers there's the time functionality to it. And so this was all done. The analysis part using some awesome tools that provided by the Space Telescope Science Institute, where you can go in and every, excuse me, photon that hits the detector has a time associated with it. So we'd bend our light curves to about 30 seconds. So I encourage you to go check out the tools if you have cost data yourself, but you know, if you want, you can also check out the get hub repository that I've put below is all of the analysis that I have done will be publicly available there. So let's look at our light curves. The title of my talks had 13 FUV flares from AU Mic c shouldn't be surprising that there are 13 players in this dataset. There's a really obvious one, right in this smack dab in the middle of visit one where you get this really beautiful double page flair. And just to highlight where all the flares are occurring during our observations, I've put them here in yellow. And so, because our dataset was quite small, basically just went in by eye and identified all the flare events, so we didn't do any kind of fancy tools for that. And most of the analysis that I've been working on and we'll talk about today, focus on these two specific regions of our light curve. The first one is around flare B, B before biggest flare also B for second in our set and we're labeling them by letters. And then we also focused on this last orbit, a visit to where we have about five or so flares consecutively after one another to see, how those kinds of flares would build up and change our spectrum. And so the first thing that we wanted to do other than creating these light curves was see how far morphology changes as a function of a formation temperature for the emission features in our spectrum. So this is just an example of our quiescent spectrum that I wanted to highlight. You get these really beautiful emission features and again there's that gap in the middle where the Lyman alpha line would have been, except it was masked. And the most, some of the analysis that we're focusing on, look at these five emission features. So these were chosen specifically because they have formation temperatures ranging from about log temperature, 4.5 to seven. And so you can really start to trace different formation locations for these flares. So I want to show you what all those different flares look like at these different temperatures, but what I'm showing here on the right-hand side is the log formation temperature on the X axis and the measured absolute energy of the flare from that emission feature. I'm going to start to fill out this plot in a second. And on the left-hand side, I will show you what those light curves look like for those specific emission features as well. So just highlighting that the right hand plot is ineffective temperature and not time on the x-axis. So I know we're used to looking at time and like curves. So trying to clarify. So the first light curve that we're looking at is a Silicon two line that has a formation temperature, lot formation temperature about 4.5. You see that it has this really nice peak and for this flares, I was actually able to fit it with two flare models. So you see kind of a little bit of a bump at the bottom there. I don't know if you can see my pointer, but hopefully you can. The next feature we looked at is look in three line where you start to really see this kind of double flare morphology, as well as that little flare down. So still going strong, but we see that the flare really peaks from this carbon three line where it has the highest energy of around 10 to the 32 ERs in a formation temperature of log permission temperature of around five. And then you can keep moving forward. So in the nitrogen five line, you see this double peak kind of go away. And then we're actually also able to trace the iron 21 line for flare B the biggest flirt in our dataset. And what's cool about this is it has such a high formation temperature. We believe this actually starts to trace what's going on in the x-ray. And I also just want to highlight that the flare models that we're currently using and these gray lines are a little bit different from what we've used in tests in the past. So the test white light flares tends to be a bit pickier or sharp at the top. We actually noticed from looking at solar flare data that the light curves for specific emission features tend to be rounded or rounded at the top. And so we're currently working on building a better model to go and fit like Herb's as observed as a function of wavelength. Another thing that I want to note about our spectra is just looking at the specific continuum regions. So these were regions with no features that we went in and been down. So what I'm showing here in gray is the quiescent spectrum, but you'll see, as I start plotting these different flares. So flare be the biggest one. And then all the flares that happen in that kind of five flare region, not only is the general flux higher, but we also get this really strange region at the bluest wavelengths of our spectrum. That really start to jump up. And what we think is happening here is that there's a thermal Bremsstrahlung component that's being added due to the formation of these flares. We were actually able to compare our data to some fuse data that was taken about two decades ago by Seth Redfield and his 2002 paper where they were observing AU Mic and they were able to catch two flares. So I'm showing that here as these little triangles, but as you can see the flares in our Hubble cosmic origins spectrograph data, the continuum is really just doing something that's about two orders of magnitude, sorry, two times the strength of what was going on in their data. So looking at different kinds of flares and how that changes the continuum is starting to become really interesting as we can compare it to archival data. Now, this is an exoplanet meeting. So I figured that a lot of people here would be interested in what's going on to AU Mic b & c during these observations. And I just want to highlight that a lot of this work is very preliminary. And so I'll go through some of the caveats that we have right now, and it's possible that these results will change by the time that the paper is ready. So kind of keep this in mind, but don't take it as absolute truth yet.

- So right now--

- Adina, you got two minutes to go.

- Okay. Thank you. So right now what we're doing is using the photo of operation equations from James Owens paper from 2017, where you can estimate the mass loss rate from these planets using this equation here that I'm showing on the left hand side which takes in the radius of your planet, the high energy luminosity of your star, and assume some court mass. We're able to alter this equation by including this F of a parameter, which looks at how much mass loss is increased or decreased based on the amplitude of your flare. So a here being amplitude. So the high energy luminosity is given by this relationship where you get some saturation luminosity for a certain period of time, and then eventually declines as the star continues to age. So what we want to do in the future is cafe the differential emission measurement for our spectrum, both in and out of flare states at which gives us a direct measurement of the high energy luminosity during these observations, so we can then just go and plug that in directly, but right now we're doing this kind of back of the envelope calculation. And so just to show you what that looks like, I know that there's a lot going on in the slide right now. So just to break it down, when you have time on the x-axis and millions of years, so, and then the fraction of atmospheric mass retained for AU Mic b on the Y axis. And these panels here on the right are just humans. So you can see in a second, as we start to add in flares that the atmospheric mass, the fraction of atmospheric master chain does decrease as you start to include fires. And so if we assume that you make will be active for about 200 million years of its life, so it will be flying very frequently for two first, 200 million years. You see that that fraction starts to decrease. And if you include flares for the first billion years, again you get slight decrease, but nothing super significant. We can put this in terms of something that's observable. So if you're looking at mass loss rate in units of grams per second, but I'm showing here is the presence of flares in our models on the X axis, and some assumed core mass on the Y axis. And these are all tend to be around one to five times 10 to the eight grams per second. So quite small, and it's about two orders of magnitude lower than the current upper limit that was placed by the Hirano 2020 paper, which use the Meta stable helium triplet to try and constrain the mass loss rate for planet B. And so I wanted to highlight that in our models, you can actually start to increase the mass loss rate by a factor of 10 in the presence of these really high energy flares. So I think that there's a lot of awesome work to be done here, and we'll continue to make this model more and more rigorous as we move along in the analysis. And with that, I know that I've run out of time. So I'll just put up my main takeaways and thank you for listening.

- Thank you very much Adina for this great talk. There is a question actually on the Q and A tool. So great talk on a unique, and you looked at any possible connections between changing morphology of the scatter light, the rediscover time and the level of flaring you are seeing.

- Oh, that is a great question. We haven't done anything to look at what's going on in the debris disc at the same time, but that would definitely be something to look into. So thanks for bringing that up.

- Okay. I, oh yes. Another question we have time for it. Flares maybe associated with CMS, which may contribute to mass loss, what would be the impact of those?

- Yeah, so I think it was, I'm not sure off the top of my head, but I would guess that if there is some relationship between these flares and CMS that it would definitely drive some of the atmospheric muscles, although I'm not sure about the literature of what's been done to kind of include those in these masters calculation. So I think that there really is a lot of room here to build on our theoretical models for what happens to these atmospheres in the presence of flares. And hopefully, as we go after these young planets and get more and more flirt data, as well as you start measuring mass loss rates for these young systems, we'll be able to start building those and piecing those together.

- You're active. So, thank you very much again Adina.