 Okay, we'll jump right in. So in the long list of superlatives you can use to describe Kepler and Gaia, stellar rotation will be one that people in this room will appreciate for a generation. Before Kepler, we knew, I would say broadly, the rotation of like a thousand, a few thousand stars. It was hard work, me sign eyes, and for a handful you could do phase curves with Kepler thanks to the incredible precision and years-long photometry that's available. We can take something that looks like this little animated rotating star and we can transform it into a rotation period. So the thesis work by Amy McClendon, working with Susana Grain to be about cool stars 18, showed us more than order of magnitude increase in the number of stars a rotation period is available. So here we have the rotation period on the vertical versus the implied mass from the kick. Kepler and Gaia about 34,000 stars. And the diagram I'm sure we'll see throughout the week is this sort of manifold that we expect at stars. Perfect. That stars, as they age, should slow down. They should lose angular momentum and sort of march up this manifold. We have handfuls of clusters sort of before and during Kepler that we could use to calibrate this surface. And this is the so-called gyrochronology work. We've heard about it and we'll hear about it again with Gaia later today. So that applies that a star should sort of move vertically in the space. That a star here, say an M-worth of stars that people in this room care about, should march upwards in this diagram. And in principle, we could imply ages for tens of thousands of field stars directly. This is the dream, this is the promise of gyrochronology that many people in this room are working hard to fulfill. Now, there's a lot of interesting structure in this diagram. The sun is here near sort of this conspicuous edge in the diagram, which we're going to talk about. There's, let's see a little better here. There's interesting structure as the M-worths seem to tip up here. There does seem to be an upper limit. There's lots of very rapid rotating stars here. And I will draw your attention to further an interesting sort of like bifurcation here split in the distribution. That's what I'll be talking about today. This was discovered in his initial paper in 2013 just for the M-worths. It said, indeed the distribution was possible that there was a slower and more rapidly rotating chunk here, about evenly split. There's also the very rapid rotators, sometimes called bifurcation here, very rapid rotators and hours to a day period. So there's a bifurcation here somewhere around 10 to 20 days, you can see it again. A little split here in the distribution. The mystery deepened a little bit when they extended the sample to all of the Kepler sources. And that this bimodality you can see in these clumps here of range of the white curve versus a period. You can see it for the M-worths, you can sort of see it for the K-worths, but by the time you get to the G-dwarfs in the F-stars, there's no evidence of a bimodality. This is an interesting mystery. Two possible explanations that represent it. The first is that it represents a variation in the star formation history. This is arguably the simpler explanation. Jaroconology must work, and therefore this bimodality represents a bimodal star formation history. The second, and though it seems a little out of hand, it's not totally unreasonable, is that this bimodality represents a new unknown phase of stellar revolution, some sort of spin down phase or rosmy number that is jumped through quickly. This is not completely unreasonable to expect, especially considering the observation that it was only the K- and M-worths. Maybe they are special, and then the G-dwarfs were traced into star formation history. So how do we tell these two scenarios apart? There's a few ways of poking them that I will discuss today. Do we actually see the bimodality in FMG stars? I'm buried in the lead here a little bit. Is the bimodality everywhere? You need something like Gaia. And can we connect this feature to other age indicators? Okay, so with Gaia DR-1, which some of us haven't quite forgotten, we were able to filter out subgiants that were contaminating this sample. So there was a lot of these subgiants in Amy's original sample that the kick mistakenly identified as dwarfs. And so this period histogram here, before the Gaia filtering and after we see nicely these G-dwarfs actually do show a viral rotation period distribution. And this age, this dip here, corresponds to something like 600 million years depending on what flavor of gyrocnology model you adopt. So that's the first test. The FG, maybe the FGK and M-stars all show consistent bimodal gap. The DR-1, of course we are now gloriously in the Gaia DR-2 era. This is the full catalog of Amy's rotation sample, and it has 34,000 stars with good Gaia distances and parallaxes, of course. And you can see lots of interesting structure here. The subgiants, there's binary stars up here, this is an incredible glorious detail in this diagram. I'll just brutally grab a box of only the clearly single main sequence stars. We'll throw out all these interesting subgiants, we'll throw out all these binaries though I invite you to come talk to me about those. And we'll left with about 16,000 stars that are obviously single-looking main sequence stars. This gives us a more complete view, so in the inner regions here within 300 parsecs, we can see this bimodality again clearly, this is my PowerPoint isochrone. Again, this gap is somewhere around 600 million years. Very clearly stands out, maybe even some other structure. Fine, thank you. Some other structure, clumpiness that seems to be visible, but there might be even more age structure in here. But again, you can see this nice track right here, clearly showing up in the nearby stars. Now Gaia doesn't work, DR2 doesn't work just for the inner 300 parsecs, we can explore this as a function of distance. And we can see that as we march out, okay, within 500 parsecs, you can still kind of squint and see this little gap, maybe in the 500 to 600 parsecs, and then it starts to go away when you get out here towards a kilo parsec. This bimodality seems to disappear. In the correct direction, not just distance from the sun, but instead galactic height, which we know to be an age indicator, this bimodal distribution here, I smoothed it and centered it around a 600 million year old gyrochrome, gyrochrome, isochrome. You can see that within about 100 parsecs of the midplane, the bimodality is very strong, and as you march upwards from the disk, the fraction stars, the young stars, defines as you expect. So this looks like it is consistent with a burst of young star formation here near the midplane. Now there's something unexpected that we saw when we were looking at this diagram, and you can squint very hard, maybe, and see there's sort of a yellow band here in the middle. This is not particularly colorblind from there, I apologize, but you have the single main sequence stars here, the equal mass binary track line right up here, and then there's sort of a gradient in color. So let me blow that up and twist the color scheme a little bit. And indeed we see a period gradient that seems to exist across the main sequence here, one of this portion of the main sequence, and throughout the binaries. And we see this goes in this diagram from blue on the left to red, slow rotating on the right. This is pretty cool. Now this here is the evolution you expect from 10 to the 8, 10 to the 9, and 10 to 10 giga-years, 10 to 10 years for a cavework, for example, that would be a star right about here. And you can see that during the first gig year it kind of marches slowly redward, and then between 10 to the 9 and 10 to 10 years it actually makes quite a large jaunt upwards and left. This is somewhat inconsistent with what we're seeing here. We see presumably young rapidly rotating stars lying bluer and maybe fainter and older slow rotating stars existing here on the top right. This also I'll note goes the opposite direction of what you expect from metalicity, that younger stars should be metal rich and therefore redder, and they should draw younger stars to the right in this diagram instead of see them moving to the left, which is sort of interesting. Perfect. So this has all been observations and games with just a couple of field of view, something over here, but of course we have K2 and now, as we all heard, we have TESS. This is going to let us use gyroponology and rotation to study how localize this bimodality, i.e. this star formation history is, and on what spatial scales can we compare? We have lots of massive star formation history nearby galaxies from HST. Could we play this sort of games of understanding how clumping star formation is your pattern is in our own field of stars? Could we see the effects of spiral-armed passages triggering star formation, if that is indeed how star formation happens? I think there's some really interesting quote here. Just to tantalize you a little bit, we are working on this. This is a figure from an undergrad I've been working with Zoe Bell, who's been working to use the Everest Likers, like many other people, to get rotation periods. You can see Recepti here showing up very nicely, but we do see evidence here. You can squint and see the bimodality showing up in the K2 field as well. So it's not just an artifact of only the Kepler field, which is exciting. Okay, and in my very last minute, a total left turn. For the last six years, we've been studying the gender dynamics of questions and answers in astronomy, most of the double-edged spinning, but also the last two cool star spinning. There's lots I can say about this. We can give a long talk about this. For me, Sarah Schmidt, Stephanie Douglas, a ton of people in this room have helped with the study. The takeaway, men ask twice as many questions as women, especially even when you account for the demographics of the audience. And we've learned that the longer a Q&A period goes, the better the resulting gender ratio is. You sort of approach the attendees' gender ratio instead of some skewed ratio. This brings us to two obvious conclusions. Let junior people, let women and minorities and people of color and disabled people, who don't usually feel like they have the opportunity and encouragement to set up the mic, let them speak, and let them speak first. There's a triggering that happens when people speak first. And then I want to applaud the cool stars organizers for making sure we have long Q&A periods, because when you only have one question, the person who's very confident in the proper role raises their hand and gets that one question all the time. So let me encourage you to step back just a centimeter and help encourage the younger people who are here for the first time for one of their very first meetings, help them make cool stars a wonderful event. And with that, I will conclude that Kepler is awesome, Guy is awesome, and you were awesome. Thank you. I must say that the directions to the chairs said exactly that. Perfect. But we're looking for hands, and that's why I'm going to talk for a while so that I can find, yes, there's one at the back, white dress right there. Hey, Jim, thanks for a great talk. I'm familiar with this bi-modality idea in Elizabeth Newton's work, too, and there it seemed to correlate with H-alpha emission. So you mentioned other age indicators, but I wish you had more time to speak on it. Are you looking for other spectroscopic age indicators to sort out whether that kind of signature is also present in the higher mass stars? Yeah, there's an evidence of, it's like von Preston Gamp and other kinds of bi-modalities and structures that were created by activity previously. I think, and Elizabeth can correct me about this if I'm wrong, I think bi-modality represents the chunk of very rapidly rotating stars here that are quite young, and the sort of field age stars here that are older. So really there's sort of three clumps. There's a very rapidly rotating clump here. There is these two branches of field star population, but that's in sort of several hundred million year range. I believe that's where most H-alpha structures you see come from. These are all H-alpha active, thermospherically active, and then most of these, well, I don't know, when you get out here it's an interesting debate. Most of these are thermospherically active. There's one over there. Thank you for this talk. Identify yourself, please. I'm Svi Mazle from Tel Aviv University, and I was very pleased that you used our catalogue of period when you arrived from Kepler, and I just wanted to ask whether your derivation of the period is using the same auto correlation technique so one can compare the results of the... Yeah, well, what I've been showing is exactly as Amy published it, the auto correlation, her best auto correlation function period. In the follow-up work of Endemic K2 we've been doing a lot of comparisons between loam-scargle and auto correlation, and you can chat with me and we'll think it's about what our plans are for doing it right or at least sort of right. Okay, two more, and then we'll talk. Yes. Okay, my name is Sasi Kekar from Bugsbuck Institute of Solar System Research. I have one and a half questions. So here you say that, originally that this dip implies a dip in star formation. My question would be what would cause the dip in star formation and are there other scenarios of the two you listed here that you can think of? What would cause it in star formation? I don't know. I'm not the right person to answer that. You can imagine exotic things like, again, passive spiral arms that trigger star formation, which would suggest that if you look this way versus that way along the galaxy, the stars here should be slightly younger and these should be slightly older. That's not really supported and what we see in other galaxies that by 600 million years, by a giga-year, things are all mixed up. So I don't know the answer. And I think there are other explanations for this. I think we could talk about variations in winds and breaking. We haven't been able to account for abundances here that can play into this. I don't know. I think I have presented it in a very simple way. One last question. Thanks for the thought. Where are you from? I'm from MPS, in Germany. My question is about what, if we are looking at systematic detecting rotation periods because of the G-key, K and M-thorff, have these problematic with the amplitude of the variability and the irregular modulation of the patterns in the light curves at the sun? Are you aware of that some of the methods are not able to retrieve these rotation periods? We definitely do see some interesting aliases. The autocorrelation function tends to do a little better in terms of not picking out the half period or the double period, but it's not perfect. Thankfully, the bilatality doesn't show up at a horizontal lump, which would be suggested of a Kepler systematic, but K2 has a lot of systematic structure we have to worry about. So I'm much more concerned there about seeing clumps at all masses at fixed periods. And then, as I think you suggested, there's a bias that you're always going to see, you see almost all of these rapid rotators because they're easy to see the spots are large. By the time you get down to solar age, the spots are very small. So we don't necessarily have a complete picture. It's very hard to invert this into a true star formation's history because you're missing 60% of the stars out here or something, right? As a function of age, certainly because they get fainter and harder to measure. Okay, let's say...