ExSSII: Extreme Solar Systems Direct Imaging

Steinn, your enthusiasm for direct imaging is apparent. :) Keep up the good work at ESS2. (Too bad I can't go to every single conference!)

Nothing with NICI? Really? Not a cheeky candidate or two?

Any direct imaging candidates mentioned at all?

Nice coverage, thank you very much.

NICI campaign has discovered a couple planets, possibly more. Not published yet. They just took the spectra of one of them with NIFS on Gemini North the other night.

â"I still think HR 8799 is a blue straggler and most all the stability analysis and age estimates are just completely off". Sorry, I disagree and would like to poke at this further (if only to make sure that my own picture of this silly star isn't broken). The star's space motion is very similar to that of other young <100 Myr groups in the stellar neighborhood. This would have to be a coincidence if it's an "older" field blue straggler. Blue stragglers are usually found in dense clusters. The dynamically "fluffy" HR 8799 system, with multiple objects + debris disk on wide orbits, would seem to suggest that HR 8799 has never been in a dense cluster. There's no evidence that HR 8799 has or has had a close stellar companion. If it's a blue straggler, from which dense cluster could HR 8799 have come from? If it's from a dense cluster, why does it have planets on circular orbits at wide separations? If it's from a dense cluster, presumably that would have to be an old cluster (no "young" globulars nearby) - why are the low-mass planets so luminous? Why does the space motion of HR 8799 seem so kinematically young compared to older field stars (and so similar to the nearby young <100 Myr populations). I guess the question is: what is the evidence that the star *is* a blue straggler?

Hmm, I'll be interested in seeing what they find. If they're able to follow this up with NIFS it probably has to either be at fairly wide separation or around a low-mass star. Either case could complicate the interpretation: high mass-ratio+ wide separation --> perhaps something more like 2M 1207B instead of HR 8799bcde/beta Pic b.

"I still think HR 8799 is a blue straggler and most all the stability analysis and age estimates are just completely off"

Can't comment on the blue straggler part, but in our paper we did the stability analysis using two different codes and couldn't find a single solution using orbits consistent with the data *and* masses above 7--9 Mj that lasts for more than about 30 Myr. Now maybe our astrometry is off/John Chambers/Hal Levison have serious bugs in their codes ... or maybe the planets' mass estimates should be revised down.

Well, it was classified as such 3 decades ago... Hm, I blogged this last year, but it is a lambda boo, low Z, inconsistent with the alleged common motion group, and astroseismology suggests it is fully mixed - that screams field BSS. it'd have to be a McCrea case A binary mass transfer, to merger, from a older field star, and the planets would have to form in an excretion disk post merger - the M and J are there, the rest are details... allows for a significantly younger formation and dynamical age for the planets, so lower mass and stable

yeah, everyone thinks it is a crazy idea, but I like it, maybe I'll write it up one day... writing papers that basically say "hey, everyone is wrong!" is not terribly inspiring

ref is Gehren 1977
HR 8799 is also a gamma dor - only star, still, I think, which is a lambda boo and gamma dor and has four planets...

Nice overview! NICI was also able to put some limits on how frequent HR 8799 planets are (~6% ish) and they were coy about having some candidates in the pipeline...

And ISM for HD 61005 is not dead yet, Fitzgerald's models looked to have problems making the "horns" of the moth :)

Add me to the "thanks for doing this" list - I wish I was there, it's nice to see the updates.

On HR8799 - I think it's fairly hard for the dynamical mass constraints on the planets to be wrong (though someone could find a "just so" resonant orbit for slightly higher masses, I think it's basically impossible for the masses they'd have to have to be a gigayear old, and the spectra and colors are also clearly different than high-mass brown dwarf spectra.) A scenario forming planets (and the debris disk, I guess) in a post-main-sequence star is interesting to develop, certainly, and I'd be interested to read a paper about it. I can't tell if you're suggesting that all Lambda Boo stars are blue stragglers or just this one?

looking over my comment I was being overly harsh--Fitzgerald's model is looking at a planet perturbing the dust which is a really interesting idea--no model perfectly fits the horns either, which is why this is such an interesting problem. Everyone needs to start putting some quantifiable measures up against the disk to see what does the best job.

@Bruce - One of the possible attractions of a BSS scenario is that it permits the planets to be lower mass and therefore both dynamically stable and consistent with cooling models.
These planets would have to form in an L2 excretion disk from the original primary as it goes off the main sequence and merges with the secondary
Possible to zeroth order, disk is massive enough, dense enough and has enough angular momentum (just) to expand that far and cool.
Maybe.

@Steinn - there's no strong inconsistency right now between cooling tracks and dynamical constraints - we have a stable 3-planet resonance for 5-7 MJ, and that's consistent with luminosity for a 30 Myr age, which Ben favors (making the star part of the Columba association.) But it's certainly interesting to contemplate other options, especially if they could lead to a disk whose density profile made the formation easier to explain. Would be happy to hear more some day - I know very little about post-main-sequence disks. (As a footnote, if phenomena like that are common, GPI ought to be able to see the disks - would be an interesting project.)

One possibility is that the HR 8799 system not stable on a timescale comparable to the age of the star. And it's not inconceivable that it is in the process of going unstable. I look forward to seeing improved observational constraints, so we can test if the system has orbits that will result in an instability fairly soon or if the system has already worked its way a stable configuration.