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[Music]

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at Yale University I'm working on some

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exoplanet atmospheric characterization

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and this talk I feel will be a little

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bit broad in scope because I'm mainly

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interested in looking at planet

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atmosphere as a very global scale and so

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the the first topic question I want to

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talk about is what do we know about

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exoplanet atmospheres from through

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cometary so the reason I point out

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photometry in general is that there are

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two main ways to observe an atmosphere

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we had a great introduction on you know

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transits and eclipses and phase curves

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and so those I'm gonna be brief here but

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so one way that you can you can try to

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learn something about an atmosphere is

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if you have a transit so this what's

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going on that's oh here we go okay so if

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you have if you're observing a planetary

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transit this red ring is supposed to be

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like the atmosphere it's a little

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exaggerated but it could not be and if

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you get absorption through that

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atmosphere that's a transmission

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spectrum you can learn possibly learn

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something about the composition of that

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atmosphere and then and then if you're

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if you're able to observe the planet

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through its whole orbit you can see

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different phases of the planet like the

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moon's phases and the clips will show

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you the full phase of the planet the

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dayside the side facing the star and

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that will give you mostly information

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about the thermal emission of the planet

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itself and but you don't get to see the

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Eclipse if the planet's orbit is edge-on

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and it's usually with the training

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protections so you see the decrement

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here you see the the the the portion of

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the planets emission that's not being

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seen relative to the Sun and so this is

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kind of an example of what a phase curve

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looks like a curve where you get you

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observe the planet in a photometric band

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through a whole orbit

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so here the transit pairs in eclipse

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okay so I'm gonna talk about phase

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photometry I really interesting phase

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curves here are three space telescopes

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that have done great work in looking at

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phase curves and then eclipses in

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general

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Kepler no this wasn't catalyst primary

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mission but you can you can use this two

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phase curves and that was invisible and

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then Hubble's Wide Field Camera 3 looked

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a little bit redder in the near infrared

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and but I

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going to talk about Spitzer bans which

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are in a little bit redder than that

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primarily because well these exoplanets

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their own thermal emissions a little bit

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cooler than their host stars so you're

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gonna move a little bit towards the

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redder including your infrared so let's

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talk first about eclipses why because

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well there's more of them it's easier to

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look for at a planet during just the

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Eclipse then for the whole orbit so I'll

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be very brief about this these are two

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plots from my recent paper I'd like to

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focus on the right one but to give

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context this is a this is a scatter plot

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of the Eclipse Tepes right that

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represents the dayside thermal emission

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of the planet relative to its thermal

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expectation so if the planet were

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radiating purely thermally at its

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equilibrium temperature that would be

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one here this dotted line and so

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anything above this is super thermal and

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so I'm gonna focus on the redder points

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here which just represent the Spitzer

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Iraq or infrared camera bands so zooming

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in and making a distribute showing a

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distribution of those fluxes relative to

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thermal we see we have some interesting

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distribution and so in the paper ice I

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sort of quantify that this approach is

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something called the log normal

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distribution if you remember from

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statistics if you have an observable or

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measurable quantity that is composed of

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many independent processes that are all

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combining to create this measurement

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then then in the limit of many

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independent processes you expect that

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some to approach a Gaussian distribution

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with some mean and standard deviation so

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in log space or correspondingly if you

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have that be a product of many

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independent processes you would expect

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to see a log normal distribution so why

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did I bring this up well it's suggesting

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that this distribution looking at all

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these eclipses as a whole is suggesting

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that there are many physical processes

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or maybe even instrumental processes

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that are creating this distribution so

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that seems like there's a lot going on

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here just looking at all the Eclipse

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steps as a whole and so if you have this

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observational data what can you what can

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you throw at it like what's a good

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physical physically motivated way to

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reproduce these observations well the

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most sophisticated way is to use a 3d

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climate model so these were originally

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developed for Earth climate models and

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I'm sure several of you that many of you

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have worked with these or seen these and

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so I'll be

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quickly just you know there are 3d

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treatment of the atmospheric physics and

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they also couple to the surface so if

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you have oceans or if you have carbon

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cycle all those sorts of things you can

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take care of that and most interesting

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to me is that you can capture the

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dynamics and the formation of things

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like clouds and the molecular absorption

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of species in the atmosphere so it's

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really useful and this is a really

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physically grounded approach and and

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very sophisticated to try to you know

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model now exoplanet atmosphere so a lot

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of work has been done to movies the

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exoplanets and so one of the things that

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gives us away from a takes us away from

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the earth like regime is particularly

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the orbital geometries of these

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exoplanets different stellar types how

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big and how you know in mass and radius

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of the planet that could change your

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surface gravity and also atmospheric

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composition and a lot of these planets

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that I'm going to talk about coming out

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data on our hot Jupiters so here I'm

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going to show some predictions from a

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very influential model from showman at

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all in 2009 so they used one of these

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three models to try to model a very

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well-studied

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hot Jupiter called to a nine four five

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eight and so here you're seeing the

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model curves and the Spitzer infrared

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bands and I'm just highlighting here in

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the red as the four point five model

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light curve and you see that at that

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time we weren't able to reproduce the

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Eclipse deaths so we have a

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sophisticated technique but we're

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missing something when we're trying to

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compare it to these data points right

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and so five years later paper buys

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element all take a full phase light

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curve in 4.5 so now you have data over

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the whole orbit in this four point five

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band and still and and here it's

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highlighting even more how what how the

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models disagree with the data and so

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we're this is pointing to that while you

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can have all the physics in there and

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it's all well-motivated

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at this point it's not clear that the

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that we can strain those physical

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properties using the data that we have

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available and so here you can see that

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the the minimum here is over predicted

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and so what we were thinking is well

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we'd want to at least fit the broad

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properties of these light curves right

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so you want to fit say the amplitude of

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the light curve you want to fit you know

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so that would be also the Eclipse step

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so you'd also want to fit where this

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minimum occurs

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if you remember during transit you've

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got the new phase of the planet the

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Nightside and so you expect maybe that

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the minimum temperature or the minimum

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flux would be during the nights the the

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new phase which is during transit but if

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you see the minimum that's offset a

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little bit that could tell you something

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about the circulation the atmosphere

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because that's telling you something as

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you know like a wind is moving the the

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cold spot away from that expectation so

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that's one metric that you can fit so

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these are all empirical properties of

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the light curve that you would like to

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fit to first order before you start

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moving on and and it's difficult it's

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compounded by the fact that this is an

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example of what the spits are like our

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spits of photometry starts out as so

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this is the raw photometry and so as

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young a tall paper from 2017 they

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outline a really good outline of how how

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much work has gone into reduce spits or

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light curve data to get something that

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you can use right and even though

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there's been a lot of work to to reduce

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the data and try to get at the real

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physical signal there is in many of

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these works a lot of these experts are

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pointing out that there could still be

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very very well be uncharacterized noise

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sources and in the in the data and so

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that's also hindering us that could be

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one of or several of the physical

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processes that are giving us that

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distribution of eclipsed depths so our

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approach so our approach is to start

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very simply so we we use the most simple

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physical model and so as a grad student

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this is nice for me because I can code

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up a model that takes four parameters so

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we take a planet that rotates we have a

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planet that heats up and cools down with

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some characteristic time scale we have a

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planet that stays some minimum

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temperature and that can encompass

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anything that's not the stellar heating

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and we have an albedo so the planet has

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some reflectivity again this is very

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very basic and we also again know the

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orbital geometry of some of these

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systems that we like to model the

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stellar and the mass and the radius and

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the temperature of the star and then the

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internal band passes like Spitzer and so

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we can model a generated temperature map

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we can involve that with how you're

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viewing it to get through light curves

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and then you can you can try to optimize

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to find the best fit parameter is a be

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score and so here's a non animated

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version of what the kind of the data

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price we get out so this is

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designing the orbit of another well have

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studied hot Jupiter 189 733 and here

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just kind of showing you where we have

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orbit data here's the data and these

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black dots and here's how we're fitting

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the data so we can do multiple fits and

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different wavelengths and we do this for

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a lot of planets in fact there are 13

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planets that we looked at some of them

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are eccentric and I'll get to why we

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like eccentric plants or I like these

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centered planets and when we compare

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these models at least at the first-order

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level we're doing a pretty good job and

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so what this is suggesting is that there

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is a need at this point that even though

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Spitzer has done an amazing amount of

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work it wasn't designed to do exoplanet

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asks for a characterization so we need

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to be aware of how how we approach the

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data especially when we're moving

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forward to James Webb one thing I wanted

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to point out is that circular orbits and

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this is motivating I like eccentric

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orbits they can have this even with the

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for printer model you expect there's

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some difficulties and one thing is that

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we have a time scale degeneracy so I

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pointed out this phase offset and so

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this phase offset you can quantify how

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displace that is and that gives that's

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represented in our model by a a rotation

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period that captures any deviation from

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synchronicity or tidal walking where the

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planet it has one day sight in one night

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side so if you wiggle that away from

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that that limit then you can get

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effectively wins or capture that wins

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and so this is kind of just a heat map

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with the likelihoods and you can see

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that there's a large energy between how

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much you wiggle that rotation period and

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what your your heating time scale is so

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those can kind of play off each other

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and that's that's partially due to the

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cement symmetry of the orbit you're

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always getting the same installation or

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a stellar heating but eccentric planets

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could break the degeneracy so here I'm

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showing a hat p2b which is an eccentric

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planet at eccentricity 0.5 interested

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and these are really really interesting

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because of the time variable heating

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from its host star so you can see here

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at it's almost I think it's like a

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factor of 3 to 5 difference this I'll

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just kind of put this as a video I had a

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video too showing like it's kind of

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thing it

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we're goals around you can you can look

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it up oh if you want I can save you a

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link but in summary so this is the first

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part of my talk is that saying that you

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know photometry can capture these

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properties and tell us a lot about the

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atmosphere but we really need to be

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careful about how we characterize our

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intrumental response and so for the next

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couple

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I want to talk about another project

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that's a little more theoretical and I

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thought it'd be a little more related to

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a lot of the astrobiology at their side

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what's going on here

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if we take this photometric approach

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could we could we learn something about

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rotation on eccentric ocean planets so

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I'm going to start with a very basic

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ocean planet model an earth-like planet

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on an orbit that is eccentric

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that's eccentric but you can you can fix

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the total orbit average stellar heating

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to match that of Earth and that's what's

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characterized by this mean flux

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approximation so all this is saying is

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that when you change the eccentricity

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here's how you scale the orbit such that

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you preserve this value of F over F flux

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over the earth blocks so just fix that

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to one tells you how to scale your orbit

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so now we know how our orbit should be

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structured to preserve that amount of

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heating and then we consider two

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rotation regimes so one will be an

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earthlike rotation and one would be

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something that extends the idea of tidal

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locking to an eccentric case using the

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same tidal arguments tidal heating

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arguments for eccentric planets there's

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a pseudo synchronous rate that remains

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pretty slow of order the orbital period

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until very high eccentricities so we're

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gonna call this the slow case and so we

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can model these planets we can we can

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look at the distribution of the ice and

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the ice cover and the open ocean cover

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and see what the surface temperatures

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are and so I'm just kind of showing you

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that you know you've probably seen some

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of these characteristic patterns of the

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eyeball where you see like a very

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concentrated melting point and then a

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more longitudinally symmetric point and

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so all us you know I'm also just crying

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pointing out to say that we did this and

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pressure and temperature some things you

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can also imagine in the atmosphere and

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so what you might expect is that for the

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slow rotating planets right around the

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point of closest approach periastron

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where there's the most heating remember

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these are eccentric planets that you

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would expect because the the planets are

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more slowly rotating they'll they'll

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have more time to evaporate and give a

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greater column density of water in the

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atmosphere so in a very very basic

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approach but we want to see whether this

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this could give a signature that could

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tell you in photometry whether you have

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a slow rotator or a fast rotator and so

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00:13:24,800 --> 00:13:21,510
what we did was we took James Webb they

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00:13:26,990 --> 00:13:24,810
and we simulated some light curves so

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these are all in the mid-infrared from

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00:13:30,560 --> 00:13:29,340
5.6 micron to 25 and a half micron and

390
00:13:32,000 --> 00:13:30,570
so you're just seeing kind of the

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differences here so one of these and the

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diamond endpoints is the slow rotator

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and the plus signs are for Earth and so

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I'm just pointing out here that in these

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00:13:39,800 --> 00:13:38,700
bands you can see that there's a

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characteristic difference and

397
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interestingly there might be something

398
00:13:45,860 --> 00:13:44,790
you know so even in the broadband you

399
00:13:47,750 --> 00:13:45,870
know there's a there's a absorption

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00:13:51,320 --> 00:13:47,760
feature of water in this second band

401
00:13:52,700 --> 00:13:51,330
here at 770 or 7.7 microns so I was

402
00:13:54,520 --> 00:13:52,710
thinking what if we took a color so we

403
00:13:57,110 --> 00:13:54,530
took the ratio of two light curves and

404
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so what I'm trying to point out here is

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that if you take if you're able to

406
00:14:02,090 --> 00:13:59,730
observe in two bands and get kind of a

407
00:14:03,050 --> 00:14:02,100
color a light curve color band then you

408
00:14:04,940 --> 00:14:03,060
could see a pretty interesting

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00:14:06,230 --> 00:14:04,950
difference potentially depending on

410
00:14:07,250 --> 00:14:06,240
where you observe even if you're not

411
00:14:09,500 --> 00:14:07,260
even able to observe the whole light

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00:14:11,360 --> 00:14:09,510
curve if you're this is one particular

413
00:14:13,400 --> 00:14:11,370
tube viewing geometry but if you looked

414
00:14:14,810 --> 00:14:13,410
right at eclipsed you may be able to see

415
00:14:17,450 --> 00:14:14,820
a pretty big difference in that color

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00:14:18,950 --> 00:14:17,460
metric may be able to tell you whether

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00:14:21,320 --> 00:14:18,960
you're looking at a slow rotating planet

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or a fast rotating planet with that I

419
00:14:40,190 --> 00:14:32,370
think I will take questions thank you do

420
00:14:49,940 --> 00:14:40,200
you have any questions Arthur when you

421
00:15:13,250 --> 00:14:49,950
showed AC 209 right so you said you

422
00:15:15,950 --> 00:15:13,260
couldn't fit into the data right so

423
00:15:17,480 --> 00:15:15,960
that's what I'm so yes so the idea is

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00:15:19,100 --> 00:15:17,490
that even with even with a full phase

425
00:15:21,110 --> 00:15:19,110
curve right we're not be able finsihed

426
00:15:22,850 --> 00:15:21,120
and and again if you if in this paper

427
00:15:24,740 --> 00:15:22,860
I'm selling and the author's point out

428
00:15:26,780 --> 00:15:24,750
that there that they think that it's due

429
00:15:28,070 --> 00:15:26,790
to eight as you point out a disagreement

430
00:15:29,600 --> 00:15:28,080
in the carbon chemistry that there may

431
00:15:31,400 --> 00:15:29,610
be some disequilibrium chemistry and the

432
00:15:33,960 --> 00:15:31,410
methane on the day and night side that

433
00:15:44,040 --> 00:15:33,970
you're not capturing work we're not

434
00:15:45,389 --> 00:15:44,050
and accurately with the model sorry yeah

435
00:15:48,720 --> 00:15:45,399
this might have been some weird data

436
00:15:51,030 --> 00:15:48,730
them from not tonight but have you

437
00:15:53,249 --> 00:15:51,040
looked at any other hot Jupiters which

438
00:15:58,850 --> 00:15:53,259
actually have has like a thermal

439
00:16:01,290 --> 00:15:58,860
inversion inhibition feature right so so

440
00:16:03,600 --> 00:16:01,300
so we have looked at planets that where

441
00:16:05,610 --> 00:16:03,610
they have been modeled using inversion I

442
00:16:08,009 --> 00:16:05,620
would say that our model itself does not

443
00:16:09,509 --> 00:16:08,019
at all capture it does not apply a

444
00:16:14,160 --> 00:16:09,519
thermal inversion model to try to

445
00:16:16,439 --> 00:16:14,170
capture the photometry even I would say

446
00:16:18,059 --> 00:16:16,449
that it even with inversions in the

447
00:16:19,889 --> 00:16:18,069
atmosphere there still remains a

448
00:16:22,769 --> 00:16:19,899
difficulty in capturing that inversion

449
00:16:25,069 --> 00:16:22,779
there's still a difficulty to capture

450
00:16:29,160 --> 00:16:25,079
the whole shape of the light curves even

451
00:16:31,499 --> 00:16:29,170
recently so it may not it may not it may

452
00:16:32,970 --> 00:16:31,509
be very well I it seems very clear that

453
00:16:34,800 --> 00:16:32,980
there are inversion layers and planets

454
00:16:35,970 --> 00:16:34,810
but whether you can take that and

455
00:16:37,619 --> 00:16:35,980
constrain the properties of that

456
00:16:39,119 --> 00:16:37,629
inversion within the context of the

457
00:16:40,619 --> 00:16:39,129
whole atmosphere in order to get the

458
00:16:47,460 --> 00:16:40,629
full picture with the light curve is

459
00:16:53,140 --> 00:16:47,470
another question so any other questions