Planetary companions around 42 Draconis and HD 139357

Waiting for discovery paper, here I post from EPE

Quote :

DOELINGER M., HATZES A., PASQUINI L., GUENTHER E., HARTMANN M. & GIRARDI L. , 2009 (update : 20 March 2009)

Planetary companion candidates around the K giant stars 42 Draconis and HD 139357
Astron. & Astrophys. , - , -
accepted

Hi!

Here is the paper: http://arxiv.org/abs/0903.3593

Bye!

Thanks, Michael.

I'm noticing a little delay between posting the paper link at EPE and making the "Note for star...." page.

However 42 Draconis really looks like an old Sun close to die.

Hmm 42 Dra b would have been located quite close to the main sequence habitable zone. Not that it really matters so much for a gas giant. And the system is very low metallicity: [Fe/H] = -0.46, i.e. 35% solar.

Perhaps any hypothetical moons of 42 Dra b may have been habitable.

Would a system with low metallicity crank out more moons than a system with high metallicity? The trend so far favors gas planets around high-metallicity stars, and low-mass planets around metal-poor stars.

That's probably a topic for another thread though. And needless to say, there isn't a lot of data points concerning the types of moons around various exoplanets.

Indeed. There are several important questions that need to be answered (of which the issue of formation is just one) before I'm convinced by the habitable moon idea.

Looks like there are reasons to doubt the existence of 42 Draconis b...

Döllinger & Hartmann, "A Sanity Check for Planets around Evolved Stars"
https://ui.adsabs.harvard.edu/abs/2021ApJS..256...10D/abstract

Quote :

One hypothesis for the large scatter of the planet frequency of evolved stars might be false positives, i.e., some RV variations of K giants are actually due to intrinsic stellar variability. This assumption is based on additional RV measurements for 42 Dra. This giant star, a member of 62 K giants investigated by Döllinger (2008) within the TOPS program, showed RV variations with a period of 479.1 days consistent with the presence of a substellar companion with a minimum mass of 3.9 MJup (Döllinger et al. 2009a). Continued RV measurements, however, are inconsistent with the published planet orbit because the RV amplitude decreased by a factor of about 4, casting serious doubt on the existence of 42 Dra b. However, we cannot exclude a two-planet solution. We suggest that the variable RV signal is very likely due to a yet unknown phenomenon that is intrinsic to the star, resistant to the current standard activity indicators and might be common among evolved stars. These stars have extended atmospheres as well as deep convection zones. Our knowledge about the structure and activity of giants is very limited. Consequently, intrinsic stellar jitter can be caused by rotational modulation (e.g., spots) and/or known short-term and possibly long-period oscillations.

(emphasis mine)

And IAU has given it the name Orbitar...

Instead there's nothing orbiting there, seemingly.

Edasich wrote:

And IAU has given it the name Orbitar...

Instead there's nothing orbiting there, seemingly.

Yeah, can't say this was my favourite exoplanet name.