A planet at Alpha Centauri B

http://www.planetary.org/blogs/bruce-betts/20130726-upgraded-alpha-centauri.html

Upgraded Alpha Centauri Planet Search Underway
(The Planetary Society)

HST transit non-detection.

Worth a shot.   

Lets say that we took a NWM style telescope and tried to focus it on Alpha Cen B. Would we be able to capture any planets or would Alpha Cen A drown them out or vice versa?

Edit: Or did I just describe the TPF   

http://arxiv.org/abs/1503.07528

Hubble Space Telescope search for the transit of the Earth-mass exoplanet Alpha Centauri Bb

Results from exoplanet surveys indicate that small planets (super-Earth size and below) are abundant in our Galaxy. However, little is known about their interiors and atmospheres. There is therefore a need to find small planets transiting bright stars, which would enable a detailed characterisation of this population of objects. We present the results of a search for the transit of the Earth-mass exoplanet Alpha Centauri Bb with the Hubble Space Telescope (HST). We observed Alpha Centauri B twice in 2013 and 2014 for a total of 40 hours. We achieve a precision of 115 ppm per 6-s exposure time in a highly-saturated regime, which is found to be consistent across HST orbits. We rule out the transiting nature of Alpha Centauri Bb with the orbital parameters published in the literature at 96.6% confidence. We find in our data a single transit-like event that could be associated to another Earth-size planet in the system, on a longer period orbit

It must have been hell to observe a first magnitude star for nearly 2 days with the HST. With observations that're saturated with 6 second exposure times, it's fortunate they were able to get a ~100 ppm raw precision at all!

The transit-like signal they do detect is rather convincing. I agree that the implied orbital period is in the range of 10 - 20 days (eccentricity notwithstanding). It also would imply a companion orbital inclination of almost exactly 90°, which is unequal with the binary orbital inclination (79.2°), and B's rotational axis (45°). Since it is also unlikely that an exterior planet would transit but an interior one not, the reality of this signal would be somewhat fatal to the 3 day planet.

This will be very interesting to see followed up. Can you imagine the value of a transiting terrestrial planet around one of the brightest stars in the sky? It would be extraordinary! But, with a largely unconstrained transit window, I wonder how this could be done…

…Maybe it's about time Alpha Centauri B got another radial velocity analysis.

I'm not convinced the reality of the HST transit-like signal would be bad for Alf Cen Bb. The inclination of the orbit plane of the binary system and of Alf Cen B's rotation axis are misaligned. This could result in planets being influenced through Kozai mechanism and ending up in orbits that are mutually inclined by several degrees, similar to what we see at Ups And.

Some amount of non-coplanarity in a planetary system orbiting Alpha Cen B would not particularly surprise me, especially given the apparent non-alignment of the stellar rotation and the binary orbit, so I'd hesitate to call the presence of an outer transiting planet as "fatal" to the case for Alpha Cen Bb. But more data definitely needed.

Hmm, yes, I suppose you're both right. It does seem like a natural conclusion that any planetary system in such a tight binary would have an exceptionally complex dynamical history. Very well then; perhaps both planets can coexist, be it somewhat haphazardly. We shall have to see!

http://www.drewexmachina.com/2015/10/16/the-discovery-of-alpha-centauri-bb-three-years-later/

The Discovery of Alpha Centauri Bb: Three Years Later

No planet at Alf Cen B.
http://arxiv.org/abs/1510.05598

Interesting analysis, wonder how much back-and-forth there will be about it. Yet another potential pitfall to watch out for in RV modelling.

No despair. I'm trusting in confirmation of putative outer planet's transit.

yes exactly me too

Lazarus wrote:

Interesting analysis, wonder how much back-and-forth there will be about it.

Apparently not much, Xavier Dumusque is quoted in the news story agreeing with the conclusion:

Quote :

Even the team that originally reported the planet agrees. “This is really good work,” said Xavier Dumusque of the Harvard-Smithsonian Center for Astrophysics. “We are not 100 percent sure, but probably the planet is not there.”