In their paper (Harrington, et al.), for example, they have a plot of day/night temperature difference versus inclination that is consistent with the observations. The plot shows that a family of solutions are possible… and the plot doesn’t even show the effect of variations in planetary radius. Even so, I’m excited by the fact that the data are good enough to exclude objects that are less than 30 degrees inclined to the line of sight, meaning that the maximum mass of Ups And b is 2-3 Jupiter masses. Note that radial velocities only give you a minimum mass and, in general, maximum masses are not known for planets that are not transiting. (Although, for this system, it might be possible to determine maximum masses from noting the radial velocity effect of integrating the multiple-planet system, which would be observable for large masses.)

Andy, because of strong degeneracies in the parameters, it isn’t possible to say anything much about the radius of Ups And b.

Mike, we know from transiting planets that these objects have radii consistent with gas giants. While there is some disagreement, most people who have studied the problem find that atmospheric loss isn’t expected, even for objects close in.

I anticipate that Harrington, et al. or other teams will continue to gather data about this system, which will eventually put much tighter constraints on all the parameters. In addition, I assume someone is working on the full infrared light curve of transiting planet HD209458b, for which we already know the fluxes at superior and inferior conjunction, as well as the radius and inclination.

I agree with you that we should trust their expertise in Spitzer data reduction.
However, the fact that there is no comparison star observed (not necessarily in the same field) bugs me
a bit as the photometric stability they claimed
during their observations is extremely high. Plus
it’s impossible to see enough details on data
reduction out of a paper published in Science…

Regarding Mike’s point, the infrared observations presumably give some kind of handle on the radius of Ups And b – is it good enough to tell whether the planet is larger than expected?

Wl: that’s an interesting point. I’d tend to assume that they did the corrections properly, and hence would trust the reduced data more than the raw data. The Harrington et al. team has a great deal of experience with Spitzer, and they understand the instruments and observing situation extremely well. But as you point out, the zodiacal dust IR background correction is tricky, and it could conceivably be that there is a behavior outside the modeling assumptions that they used.

Mike: If the planet doesn’t have an atmosphere, then it would essentially be a large rock, and as you point out, such an object would cool off very quickly. The IR emission in this case, however, would this be considerably lower than observed because the radius of the planet would be much smaller. So a rock would give the correct phase variation, but a much smaller amplitude than observed.

Andy: We’ll reveal that one shortly. Jonathan has done the hydro calculations for that case (Cassini State II)…

Why do you assume an atmosphere?
It would be logical to assume that a planet, that close to its primary, has lost its atmosphere long ago.
If there is no atmosphere, the analysis makes sense, there is only conduction through the solid to transfer heat.

Mike