HR8799: wrap-up

So we had a rather nice discussion over the recent paper on LBT observations of HR8799. Seemed a good discussion with mostly a few people who work in the field or closely related fields. If you missed it feel free to comment. And there was a question by @LeonBaloo about resonances which got lost. Any good definitions welcome. Start from the bottom when reading.

@Matt_Burleigh: @nialldeacon thanks for organizing Niall. Goodnight from the UK #astrojc

@nialldeacon: @johngizis true, but it says those kind of objects (formed by instability) are rare #astrojc

@Matt_Burleigh: @johngizis yes, which makes it so exciting and gives us all a lot to work on! #astrojc

@johngizis:We are still too much at the tip of the iceberg, only the widest, most massive planets can be detected. right? #astrojc

@nialldeacon: Think probably a good time to wrap up #astrojc will put a review post up soon so others can contribute

@Matt_Burleigh: @astronomerslc25 50-60, late B to early F spectral types #astrojc

@astronomerslc25: @Matt_Burleigh how many in the sample? #astrojc

@Matt_Burleigh: @nialldeacon I guess we just dont have enough information yet. Fascinating system, poses many questions for different areas #astrojc

@nialldeacon: @Matt_Burleigh still would be one of the younger systems but doesn’t explain why it’s the only one #astrojc

@Matt_Burleigh: @nialldeacon @johngizis I think the sample were selected for youth (<~250My) #astrojc

@nialldeacon: @Matt_Burleigh Are all the A stars in the sample of similar age? Maybe others have had planets which were kicked out dynamically? #astrojc

@Matt_Burleigh: @nialldeacon @johngizis I guess HR8799 needed a massive, large (~100AU) disc though #astrojc

@nialldeacon: . @Matt_Burleigh My disk knowledge isn't good enough to know how exceptional the disk is @johngizis any ideas? #astrojc ‏

@Matt_Burleigh: @nialldeacon Maybe. What was special about HR8799 then? Or maybe stats arent yet good enough, #astrojc

@nialldeacon: @Matt_Burleigh so I dunno what it says about formation. That wide massive planets from disk instability are rare #astrojc

@nialldeacon: Retired A stars means ones that evolved off the main sequence so have lines that make RV planet surveys easier #astrojc

@Matt_Burleigh: @nialldeacon yes, some appear to be retired G stars! #astrojc

@nialldeacon:. @Matt_Burleigh there are some around the "retired A stars" although there is debate as to whether the retired A stars are retired #astrojc

@astronomerslc25nialldeacon oh yes. Although not as odd as 2mass1207 #astrojc

@Matt_Burleigh: Jenny Patience revealed at #nam2012 that no other A star in their survey has planets. What does all this say about their formation?#astrojc

@astronomerslc25: @Matt_Burleigh @nialldeacon #astrojc or much else I think. Looks more and more gravity dependent too

@nialldeacon: @astronomerslc25 Planet b being the poster-child for that #astrojc

@astronomerslc25: @nialldeacon #astrojc looks like more evidence for a delayed L-T transition with youth.
In reply to Niall Deacon

@Matt_Burleigh: @nialldeacon @astronomerslc25 the infamous L-T transition – where it seems spectral type does not tell you much about temperature #astrojc

@nialldeacon: @astronomerslc25 #astrojc well they all lie close to the L to T spectral type transition in temperature

@astronomerslc25: @nialldeacon so what makes them patchy? just right combo of teff and grav? #astrojc

@nialldeacon:. @Matt_Burleigh youth makes the clouds thicker hence makes them redder but they still needed patchy clouds to fit #astrojc

@astronomerslc25: @Matt_Burleigh @nialldeacon there was an Akari paper on L dwarfs in 3.3um. They found the spectra was not what was expected. #astrojc

@Matt_Burleigh: @astronomerslc25 @nialldeacon is the low gravity a factor? #astrojc

@astronomerslc25: @Matt_Burleigh probably. Although not much flux there #astrojc

@astronomerslc25: Maybe just effects of youth though? #astrojc

@astronomerslc25: @nialldeacon I suspect so, but the bright 3.3 is odd. #astrojc
In reply to Niall Deacon

@nialldeacon: too simplistic? #astrojc

@nialldeacon: my understanding of patchy clouds, cloudy parts look like L dwarfs, gaps like T dwarfs and the integrated atmosphere mixed #astrojc

@LeonBaloo:.@nialldeacon ok 5:2 means 5 inner = 2 outer orbits. But what defines a resonance? The largest/smallest/innermost/outermost planet? #astrojc

@nialldeacon: @astronomerslc25 so patchy clouds then #astrojc

@astronomerslc25: @nialldeacon hey! I'm in for the atmosphere stuff #astrojc

@nialldeacon: I've seen claims of huge free floating planetary mass things from microlensing, how believable are they? #astrojc

@nialldeacon: So @dh4gan mentioned chaotic orbits lead 2 ejections and would be a source of the population of free floating planetary mass things #astrojc

@LeonBaloo: So, basic planetary question: what’s a 4:2:1 or 5:2 resonance? #astrojc

@LeonBaloo: Hi @nialldeacon; am arriving late to the party – know nothing on planetary science so will mostly be watching and maybe questioning #astrojc

@Matt_Burleigh: Im partcularly interested in orbits and thoughts on formation mecahnism. Hoping @astronomerslc25 will join in to talk about atmos #astrojc

@nialldeacon: Right, the hour has come, let #astrojc begin. Which aspect do you want to talk about? the atmospheres, the AO or the orbits

@dh4gan: Also, ejection of such planets might help explain the apparently large number of free floating planets #astrojc

@dh4gan: HR8799 is poster child of gravitational instability mode of planet formation. Growing realisation that GI systems often unstable #astrojc

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