- All right. So I'm happy to be here presenting an update on SAG 21 the study analysis 21 on The Effect of Stellar Contamination on Space-based Transmission Spectroscopy. We want to give a huge shout out to the entire SAG 21 team, who are here. Ben, I think, is in the audience. And I'm presenting on behalf of the entire SAG 21 group. Has been a very, very, very productive analysis group. So just a little outline. So when I go first to the goal from the timeline of SAG 21, then I'm gonna go into explain a little bit about our community symposium, something that we're very proud that we did, and that we felt was so well that we had to share here with you. And then finally, I'm gonna give you the status of the report, which is the main deliverable that we giving SAG 21. So let's jump right into the goal and a timeline. So what is SAG 21 about? In SAG 21, we're focusing on the challenge of stellar contamination. This is an effect that happens during transmissions, specifically when the sun is backed in front of the star, and this happens because you're not transmitting like a uniform source, which is what we would love to, but stars have their own heterogeneity and they can affect the transit depth that you measure the . So if you measure that as a function of wavelength, then each pass of wavelength depend on impact that we call the contamination. For stellar astrophysicist out there, this is actually a signal contamination. So let's say that's an important detail we have here. So what the impact of this does, in the middle panel, the middle figure, you can see that you have a difference between the seen light source that you're assuming the entire star is uniform, but then the actual light source, these spots and faculae that can impact the real stellar spectrum. So when do you divide the in and out of transit spectrum and get the chance of depth, basically, what you see in that right figure, then your observed transit spectrum will defer from the true transplanetary spectrum by the impact of these spots and faculae. So the main goals, the main question that SAG 21 is trying to answer or to give a summary on is to what extent will this impact the space-based transmission spectra? Thinking of all this estimations from , and then also the missions that are gonna come after that, what's the limit to all this? So the goals were divided as basically what do we know and what can we learn from this star? Doing different types of observations from chromospheric activity, photometric monitoring polarization. Can this give us some information about the diffraction, the temperatures, the contrast faculae and spots in stars, that we can use them to understand its effect better? What have we learned from transit spectroscopy? Both from the planet, and from transit spectroscopy itself, but also from the star. So when planets go in front of the star, they can occult some spots, for instance. And also, you can see some shapes in the outer transit flock given by these spots and faculae. Even flairs can also be informative in the stellar activity itself. And then with that, we can then give an input onto what will be the impact on future studies, and what complementary observations will be useful in order to handle this stellar contamination? So the main deliverable is a report to NASA by mid-2021. So we're very close to that. And we're en route to delivering that report. And I'll talk a little bit about that in a minute. So here's the timeline. This timeline, we have been updating it, but basically, this thing that we have to send in a previous update. So at the very beginning last year, we had a kickoff meeting. We defined the way in which we were gonna operate. So we operated to subgroups, and I'm gonna share with you in a minute. And then we defined the final questions for the subgroup in November last year. Then new year came, then we had our community symposium, which I'm gonna explain it a little bit. So we had, I think, bout to gather more feedback from the community. And right now, we're in the red point after the draft report that has been handed in by most of the subgroups, and we're heading into a set of Red Team reviews. So we're crosschecking the reports between subgroups. And then we're on good with the submission of the report to NASA in mid-August. So let me tell you a little bit about this community symposium. So the main motivation of having a community symposium was based on the fact that we know that not everyone had, maybe interest at the beginning or time itself to join SAG 21 and be a part of these analysis. And we know that there was a ton of science happening out there. So we wanted to have that plan in the report in one way or another, and also to have a hug, to have some community input from people outside of SAG 21 itself. So this is where this idea of the community symposium began. And the aim of community symposium was to make a call for contributed talk, and then have a set of contributed talk and on top of that, also provides some overviews from our subgroups in order to let the community know what we were up to with SAG 21. And I'm happy to report that it was a huge success. I'm really proud by the entire SAG 21 team on this. So here's some numbers. So this happened between March eight and nine. All the info is in our website. We had these five overview presentations from subgroup leads, one from each subgroup. We had 21 contributors talks, which were really, really exciting. And we had over 100 attendees with about 50 active participants on Slido making questions. So here's a snapshots of what you can find the website of the community symposium. So we have the whole agenda of the program for day one and day two. So you have title, you have the abstract that you check out here. But also, we recorded the talks. So you can have a detailed view of what happened, not only the talk, but also the discussions from the discussion section, which were super, super interesting with a ton of feedback that was super useful to form the final report that we're about to submit. So I really encourage you to check it out. Again, it's an amazing set of science, really cool bit of feedback and discussions in the community, which is really, really great to have. Let me come now to the status of the report. I want to explain first how we're handling this from a management standpoint. So how we're moving forward with the entire team. So the road to submission, we like to call it. So we started with step one here, which is what has already happened. So the subgroups submit a draft report at the beginning of the month. But of course, this was full of previous work, as I showed you the timeline. So in total we have five sub groups and we have 11 subgroup leads that led the work of each subgroup. We have over around 40 contributors, and how these work is that we had monthly meetings with the subgroup leads in order to check in because, as you're gonna see, there's a lot of cross information that we have to share. So we had to organize all this, and we organized this through these monthly subgroup lead meetings. So we met, we the chairs, met with the leads, and we tried to communicate with each other, and then the subgroup leads, they also had their own meetings with their subgroups in order to organize as well. So we're jumping right now to step two, which is a set of Red team reviews. So people need did not work in a given subgroup, they're gonna read the chapter from a different subgroup plan than the one that they worked on in order to provide feedback. So we created a set of guidelines for these Red Team reviewers. We have 19 Red Team reviewers. They have also different career stages and expertise, which is great because we have different eyes on the chapters because it's gonna happen in a few week turn around. After this is done, so this it's ongoing right now, Red Team reviews are happening right now. We're gonna have revisions by the subgroups, given these Red Team reviews. And that has a three week turnaround. And then, after that, it's updated, then we're gonna have, we the co-chairs, we're gonna review and revise the entire chapters, sometimes general editing, fill some gaps in the introduction, and then we go on and submit. So let me give you a little bit of a taste on what are the findings of each of these five subgroups. So the first subgroup group is stellar photospheric heterogeneity. And this subgroup, basically, it's the physical picture of what's going on in stars. It's a very stellar-focused subgroup. which has been amazing. We have learned the extraplanetary . They're learning a ton on the subgroups. So it goes all the way from what do you know from stars, all the way to the planets as well. So the first finding that they have is that, basically, the main idea I'm gonna highlight with colors here so you don't have to read these parts. But the most important point here is that solar surface structures and timescales from minutes to years will provide a benchmark for these kind of study. So if you go into detail into them, you can learn a ton of information about what's going on in other stars. There's a need to do this, to feed that information. That is important. The second finding that they have is that many lower activity stars are actually faculae-dominated. And we don't know a ton of facts about faculae. So they've had an urgent need to understand this because the lower activity stars are the ones to which typically changing exoplanets folks go to because they have supposedly lower stellar activity, but then they have a kind of stellar activity, these faculae, that you don't know very well. And it's very hard to understand what the impact will be. So there's a need to study them. The third finding has to be with the effect of magnetic fields. So magnetic fields drive these stellar The execution to actually develop further models and understand as well in order to understand what's going on with these stars, to understand better the contamination. The second subgroup- - Nestor? - Yes. Go ahead. - [Moderator] Sorry to interrupt. You're about halfway through your time, including questions. - Okay. That's great. So the second subgroup is stellar spectral decomposition. They focused on understanding the idea of when you get chance of , you get an extra spectrum from both the stars and the planets. So you can use that to understand both your star and the planet. So it's based on, for example, retrievals. The first finding of this subgroup is that retrieval of a transmission spectra can actually include the effects of this unocculted active regions and can help you guard against biases. So there's more work needed, especially fill the limitations of these particular tools. Second finding is that retrieval approaches rely on stellar models, of course, because when you actually retrieve this stuff, you need to make some assumptions about the stars. But then, they are accuracy of this stellar model is limited by model fidelity. So how much do you believe the model? So there's a ton of work to be done here as well. The second finding that I found super, super interesting as well. And the third finding had to do with the fact that, for low-resolution transmission spectroscopy, the impact of this contamination is larger at shorter wavelengths. So there's a complementarity that can happen with missions, like infrared, the far infrared, all the way, complementing that with both HST and norm-based studies that can help you join and understand fully the extent of this stellar contamination. Subgroup three have to do with occulted active regions. This is a very cool spectra transit. So if you have a transit, sometimes the planet occults a spot or a faculae as well, like a bright region. And then, you can get this information as a function of wavelength. And I can tell you a ton of information about what's going on in the spot, what the spot contrast looks like, what the spikes are. So their findings are basically focused on , and the first one is that precision improves. We expect to be sensitive to smaller spots, which are more numerous. So these smaller spots we have not had access before, and the only ones we know are from the sun. There's a huge need here to understand these smaller spots in detail in order to guard against what we're gonna start seeing with improved spectral precision, spectral precision is what Second finding here is that there's several publicly available forward modeling tools to model these spot tracking events. So there's some work necessary to fully leverage space-based datasets. Kepler, TESS, CHEOPS, HST, and with these tools in order to evaluate them and try to extract the information with them. The third finding has to do with the need to understand the difference between what you can learn from lower resolution and high resolution studies with occulted active regions. There might be things out there that we're missing because of the different resolutions. So this is also very important to look into, according to subgroup three. And finally, the fourth finding of subgroup three, have to do with actually linking stellar models of ab initio calculations of stellar magnetic activity to what we find. So far, when you try to model this are completely ignorant about any models that we have. There's a need to join these two things, the best of both worlds. Sorry, that was the second plan. The fifth is that long term and multi wavelength monitoring of exoplanet host stars can constrain otherwise degenerate properties of occulted active regions. So when you're tied to space for this parameter, the and of the size of the spots are completely degenerate. But then, you can have multi wavelength or long-term monitoring in order to understand this much better. This fourth subgroup, they did this fourth set of findings, the last set of findings, sorry, that I'm gonna present here had to do with unocculted active regions. So this has to do both with what you're measuring with transit spectroscopy, but also with longterm monitoring. So this finding number one of this subgroup has to do with, it's high cadence light curves provided by different missions, but our biggest measurements are loose as of right now as of present. How can we suppress it? There's a need to actually go and develop these tools in order to develop relationship between observational signatures of high-cadence light curves. The second finding has to do with simultaneous photometry and spectroscopy, which provides critical information for understanding the aspects of active regions. But there's work needed to maximize the retrieval . One thing I need, if I'm gonna do transit spectroscopy, what exactly do I need in order to maximize my constraints on active regions? And then, this finding is super important, which is the fact that as you improve the position, you're actually more and more sensitive to smaller noise floors, and in particular, granulation flickers. It's a fundamental noise floor that, no matter how good your photo noise is gonna be, you cannot beat it. You cannot beat the star. You cannot quiet the star. So this is a larger or short wavelength there's a need to understand this noise floor in order to try to account for it in actual datasets. So now there's a fixed group, but the actual findings from these five subgroups these future complementary observations is dependent on the rest of the findings. So this is a subgroup in which we're gonna be presenting findings which are built on earlier analyses, which are in preparation. And with that, I was just gonna meet you with all the information is in the Google group site, SAG 21 webpage. I'm gonna leave the summary right here, and I will take any questions. Thank you. - Perfect. Thank you, Nastor. Okay. That was a great update. Do we have questions? I don't see any in the website yet. I had one question. So you mentioned several times the long-term monitoring of host stars and their planets will be important. Is this the SAG identifying explicitly what long-term means in this scenario? - What, sorry? - What the definition of long-term is. How much long-term data is required? - Yeah. Yes. That's part of the discussion ongoing in the report. But yeah. - [Moderator] Okay. - Yeah, look out for the report. - [Moderator] Perfect. Perfect. - [Moderator 2] I have a hand up from Renu. - Thank you. Renu, would you like to unmute? Unless that was accidental. Oh, there you go. - [Renu] All right. So great. I just have a question about one of the recommendation in subgroup four, and you said that simultaneous photometric and spectroscopy observation will be helpful to constraint some of the unocculted active region contribution. So do you mean that photometric in the same wavelength span as the spectroscopy, or you mean the photometric in a different wavelength region? - Yeah. That's a very good question. I think it all depends on where your observations are located. So I think it's linked with what subgroup two and three were talking about in terms of going to shorter waving. It's usually very, very useful, and it's very information-rich. There's a huge discussion on this on the report, but it basically depends on what you're currently observing and what is complimentary enough from your spectroscopic monitoring in order to feed that into your retrieval. So, for example, it doesn't make sense to do a lower resolution optical if you're already observing or doing full spectroscopy monitoring in the optical, or you will have a ton of information, you'll go to the optical with this spectroscopic monitoring if you're observing that very infra, like . Maybe observations are near infrared. So the strategy will vary, I would say, depending on where you're actually observing. - [Renu] I see. Thank you. Look forward to the report. - Thanks.