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[Music]

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so I met salim a graduate student at

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University of Washington working with

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the vdl and recently we did a project to

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see if we could constrain anything about

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Proxima Centauri be looking at the

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overall emission specifically the five

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five seven seven a green line which you

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can see here this beautiful image so a

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little review about Aurora they are

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driven by star planet interaction

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typically you have some forcing from the

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stellar wind or a transient activity

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like what you see here in this cartoon

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which compresses the magnetosphere

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energizes particles and causes a lot of

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interesting physics but what you get in

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the end is the precipitation of

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particles down into the atmosphere along

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the magnetic field and forms these

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beautiful bands of color and around in

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forms it's a royal oval that we are

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where this characteristic a little years

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to seeing and so in general I want to

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point out that we are looking for Aurora

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airglow so we're looking for these

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discrete localized and intense emissions

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coming from the planet where don't care

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about air glow it's a little too faint

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we could put our calculations in oh

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there's no real chance to see that at

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least with present instruments and

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so we want a really good star planet

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contrast luckily Proxima Centauri is an

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indoor so it's beneficial to look in the

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optical region if we want to see

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something from the planet so the harps

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data you can see here yes here check it

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in blue if you can actually see that is

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right in the middle the optical where

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Proxima Centauri actually has whoops so

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Proxima Centauri actually has very low

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flux and so we're going to look for the

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50 577 oxygen line there and it's really

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exciting if we could see these lines

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because not only would it provide

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independent verification of the planet

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itself it would also help to constrain

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orbital parameters as well as be a

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direct verification and identification

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of atmospheric species so that would be

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very awesome whether it's oxygen or

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nitrogen or hydrogen or whatever it'll

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be a nice direct observation of the

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atmosphere so in general I'm going to

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tell you how we estimated the signal

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strength how detectable we think those

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signals are and then about the search

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through the harps the available harps

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data the discovery data so for the

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signal strength we use two separate

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models the one is just a simple kinetic

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forcing model and the second is an

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empirical image CD fit model by weighing

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at all 2014 both of which miss a lot of

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magneto spirit physics but they should

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be just good enough close to close

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enough to a nice order of magnitude

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calculation for the aural emission

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and so you can think of the

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magnetosphere as basically an obstacle

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and the fluid flow of the stellar winds

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it has some cross-sectional area that is

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upon which the stellar wind will impact

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and dump energy and so the stellar wind

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has some kinetic energy and so therefore

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you can calculate simply the power

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dumped onto the surface of the

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magnetosphere however only a fraction of

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that power is then transformed into

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electromagnetic auroral emission which

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you can see here for Earth it happens to

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be by 1% efficiency on average and only

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about 2% of that is the five five seven

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seven green line and actually that's a

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pretty big percentage for a single line

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but only got two percent so this is a

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very simple kinetic forcing model which

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we can use and this gives us a value of

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approximately 40 to 50 gigawatts for the

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output of just this five five seven

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seven green line which is about seventy

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to eighty times that of Earth okay so

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fairly bright on the second method I

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mentioned is wing at all 2014 this

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horribly ugly non-linear equation here

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they used a 3d global MHD model to fit

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the magnetopause surface and across a

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wide range of stellar wind parameters

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and then fitted or excuse me an invalid

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ated against satellite data

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magnetospheric satellite data to get an

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empirical fit to make sure that is

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empirically correct and you can see that

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it has the kinetic portion can

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contribute by the stellar wind but it

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also importantly includes the magnetic a

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flower power that you're connecting on

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to the magnetosphere both includes the

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magnitude and the orientation of the

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field which are important because you

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must take into account the pointing flux

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entering my needle sphere as well as the

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orientation of a field which can drive

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energetic reconnection events both of

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which can affect energization particles

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and overall precipitation so we followed

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their lead and found a few empirical

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measurements of say electron populations

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and how they relate to the brightness of

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the 577 green line and tried to

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determine as close to data as possible

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what we would actually see and this is

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what we find so for the quiet version

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meaning we have no stellar activity and

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no geomagnetic activity occurring it

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matches pretty well with just a simple

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kinetic model including geomagnetic sub

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storm activity which we use we use a

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proxy basically within

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assume very strong reconnection at the

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Magneto's claws and reality the

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geomagnetic storms have stronger

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connections with magneto caused by

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driver strong marine current which

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effectively weakens the magnetic field

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of the planet and can affect their world

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activity but you see here we jump up to

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140 to 240 gigawatts or so for the Green

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Line including the effects of stellar

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activity this is a coronal mass ejection

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so you know order magnitude greater

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density and magnetic flux and a factor

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of two or three higher speed and this

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ejection of energetic particles out from

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the star we jump up to four to eight

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terawatts and then if you assume that

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this one of these coronal mass ejections

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actually drive sub storm activity on the

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planet we jump up in the tens of

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terawatts

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okay so again missing a lot of physics

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but decent order of magnitude estimation

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and so this ends up being on the order

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of tens of thousands of times Earth's

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nominal five five seven seven emission

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for low to moderate geomagnetic

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geomagnetic activity so it looks pretty

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good it looks fairly promising I mean

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relatively anyway but let's actually

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talk about the technical team so this is

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the line here on the right this is a

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nice high-resolution spectrum we

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produced for Proxima Centauri B as

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viewed from quadrature you can see the

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green line here that we injected it's a

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point one terawatt so at the lower end

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of our estimations that I just showed

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you it has pretty high flux density so

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that looks promising however it's an

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extremely narrow line and so your active

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width is around a third of an angstrom

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or so and so you're going to be very

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high resolving power to be able to see

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any of these very narrow very intense

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lines and my understanding is for a lot

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of these future missions we discussed

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this week we're discussing them in terms

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of our value about 100 resolving power

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100 which for our full width half max of

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this line we calculated means the

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spectral element width is about 1,000

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times the width of our line so we're not

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going to be able to see anything it just

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going to be smeared out and lost so we

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have to have high resolving power to

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view any of these these lines that are

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extremely narrow like this obviously so

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that means we want to have the best

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planet star contrast possible and so

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this is a plot of a planet star contrast

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in colors and contours

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with resolving power on the y-axis and

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mom scale and our calculated five five

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seven seven green overall power on the

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x-axis in log scale also the dashed

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lines represent the full width half

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maximum selling power in orange and the

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equivalent whip resolving power and the

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diagonal as it is a function of the

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power of emission and so basically you

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want to have your observation be inside

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this wedge and with the best climate

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stark contrast possible harpes for

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instance has a resulting power of one

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hundred and fifteen thousand so that's

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that's our nominal idea that we need to

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know somewhere in the order of 10 to the

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4 is 10 to the 5 resolving power and if

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you look at the powers that we I just

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told you on the estimates of our signal

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we see that we obtain a star planet

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contrast or keeping planet star contrast

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of 8 times 10 to the 7 and 7 times 10 to

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the minus 5 for direct observation in

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the optical around for this emission of

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Proxima Centauri so I'm pretty good for

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direct observation looking for the

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submission but what does this say about

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the actual integration time you would

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need well so we calculated the

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integration time to reach a signal noise

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of 6 with an R value of 150 thousand in

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all cases so here in x-axis we're

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looking at integration time and hours

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log scale and we did this for harps have

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exlude war and a 30 meter telescope the

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green bar is one point our low end point

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one terawatts a yellow bar is 10

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terawatts

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and then highly unlikely which I mostly

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ignore the tails and terawatt emission

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in red and so you can see for harps we

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need somewhere between present-day

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hundred thousand to one billion hours of

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integration time highly unlikely say

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unlikely but for these future

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instruments you can see especially on

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the top end here for 10 terawatts we

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start getting down to the 10 hour one

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hour point three hours of integration

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time so this becomes highly probable and

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I will say that given the activity at

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high activity Proxima Centauri and

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assuming of course that you have a

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magnetic field which we've assumed in

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Earth's dipole our sized planet

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given exactly if you have a magnetic

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field you're likely to drive these logs

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team activity is going to likely drive

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sub storm activity on the planet there

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all these assumptions and

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you're going to have some signal that's

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between the two bounds that we got at

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this point one terawatt in 10 terawatts

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so the average flux that we'll see when

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we look to cross missing tardy if it has

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an atmosphere in a magnetic field it's

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going to be somewhere between these

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green and yellow lines and you look at

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these future missions and you absolutely

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see that within a few days these

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missions could your admissions and/or

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ground-based scope for the 30-meter I

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could actually pick out these signals

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within a reasonable time and so I should

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I should mention I shoulda mentioned

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this at the beginning leVoir we

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estimated this for a 16 years of war and

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this is the certainty of telescope with

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a coronagraph of design contrast 10 to

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the minus 7 ok so given what I just told

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you about harps we did look through the

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data and we need you know at least a

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hundred thousand hours but we have 70 so

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let's see what we can actually find so

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to the pipeline that we followed for

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time purposes I'm not going to go into

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it too much but basically remove the

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stellar signal we docile ship into the

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proximities rest frame and then want to

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stack all of this flux and book for our

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5 5 7 7 but it's a radial velocity

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measurement so we have to be careful

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about looking through the Earth's

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atmosphere where we have 5 5 7 7 airglow

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and or and the fact that we're looking

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to Proxima Centauri which relatively

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orbits rapidly and therefore the Rd

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signal will be passing through what

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we're seeing in overlapping from the

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earth so anytime anyone overlaps occurs

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either you know from earth signal with

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the planet or Proxima Centauri or signal

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with the planet we removed that data and

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don't consider it to make sure we're not

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contaminating and then we use a filter

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to get rid of the noise and stack around

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the second two bins around the line of

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interest so here's a strongest signal we

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performing a grid search because we had

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to constrain some orbit parameters of

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the Rd measurement because the

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inclination is absolutely unknown due to

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the method used so but our strongest

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signal came out with an inclination of

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52 degrees this period in the mean

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longitude and you can see that here this

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is in the rest frame of Proxima Centauri

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B this is the blue window you see the

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center here centered on our line of

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interest and you can see that the earth

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lines and then the tiller Cline's from

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Earth in green and the lines from the

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host star in red and again because we're

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now in the rest frame Proxima Centauri B

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we see

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the nice Doppler shift of Earth and the

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star from that point of view so since we

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have all of our flux stacked up we can

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just are in the flux alone nicely lined

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up here for the planet we can just add

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all the flux together and look for our

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signal we do this and this is what we

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see here is the signal it's there's a

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bump there yes unfortunately it's in the

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middle of bunch of noise and

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inconsistent with rest of the noise and

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when you've been at the same thing

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happens so and in fact it is consistent

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with noise what we do is we take we did

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then saw this and took a window of 200

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angstroms around the other side of the

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line of interest and ran this exact this

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exact same pipeline the exact same grid

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search found the strongest signal for

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each wavelength in a 200 angstrom window

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and we see this so it's consistent with

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correlated stellar noise unfortunately

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and we don't expect any emission from

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the planet on either side of the 577

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line so yeah there's a lot of this going

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on so we failed to move all the noise

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and that's going to be a limiting

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factors or they're seeing these lines at

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this point I think at least with the

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harps data so the significance is point

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7 sigma 20% false alarm probability so

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we will actually say that absolutely not

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detection because we don't have the

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requisite 1 billion hours of data ok but

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all is not lost as I mentioned these

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future missions have a do enough of a

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light bucket that they can collect the

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signal and but we need a high resolution

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spectrograph to take these signals out

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and so that's part of the hope that

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we'll see that in the future that these

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you know 10 to the 4 to the 5

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spectrograph will be included we did

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actually elevation we did actually also

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ran a search for the strong 3917

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nitrogen line and the 6300 oxygen line

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but also it's all nothing

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so I told you about our signal strength

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which is many times that of Earth I told

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you about our expected detect ability

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and making all these assumptions it

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requires really high resolving power and

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a large aperture we didn't have that

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large aperture unfortunately so we

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didn't see anything in the data but we

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think the future missions it's it's

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likely that we can get some sort of

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exciting observation like this and

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constrain the atmosphere directly if we

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can get all of the technology in place

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so thanks to my co-authors and BPL and

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thanks to all of you for your attention

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[Music]

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we have a few minutes for quick

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questions hi this is a great effort as I

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was wondering if you stack all the lines

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together to have in your spectrum is

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that a way to sort of decrease the

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amount of observing time you need to

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detect any emission at all

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I'm sorry so if you stack multiple lines

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together

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I said away sort of to decrease your

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observing time you would need I'm not an

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observer so that's a really good

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question I would refer you to when I co

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others and maybe Rodrigo can answer that

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now do you mean lines of different

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elements or different lines of oxygen

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absolutely right but you want to make

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sure that you're stacking lines that

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exist and so like if you were to stack

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the oxygen and the nitrogen line the

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00:14:04,920 --> 00:14:03,280
nitrogen line doesn't exist you'll get a

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00:14:07,260 --> 00:14:04,930
lower signal because you're stacking

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00:14:09,630 --> 00:14:07,270
signal with noise but you've definitely

404
00:14:11,580 --> 00:14:09,640
do a search that way where you you

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obviously oxygen has tons of lines of

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00:14:14,250 --> 00:14:13,030
need for red as well and we could stack

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all of those and do some kind of grid

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00:14:20,180 --> 00:14:15,670
search it would definitely increase your

409
00:14:27,000 --> 00:14:23,040
what is the upper limit correspond to in

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terms of terawatts welcome sorry you are

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giving the detectability you are

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measuring the line strength in terms of

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terawatts yes and then you presented an

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upper limit in terms of Sigma's what

415
00:14:42,300 --> 00:14:36,370
does that correspond to it in terawatts

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oh so I believe so mmm the point seven

417
00:14:46,950 --> 00:14:44,170
think I'm not really sure but we did run

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an upper bound of eight segment

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detection and I've ended up being

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something on the border freed alcantara

421
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watts or so but but the point seven is

422
00:14:55,320 --> 00:14:53,980
no it's something ridiculous that okay

423
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it's in the paper kendra has a spare

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let's go let's thank Matt again