# ROXs 12 b and FW Tau b

## ROXs 12 b and FW Tau b

Three Wide Planetary-Mass Companions to FW Tau, ROXs 12, and ROXs 42B
http://arxiv.org/abs/1311.7664

We report the discovery of three planetary-mass companions ($M = 6$--$20 M_{Jup}$) in wide orbits ($\rho \sim 150$--$300$ AU) around the young stars FW Tau (Taurus-Auriga), ROXs 12 (Ophiuchus), and ROXs 42B (Ophiuchus). All three wide planetary-mass companions ("PMCs") were reported as candidate companions in previous binary survey programs, but then were neglected for $>$10 years. We therefore obtained followup observations which demonstrate that each candidate is comoving with its host star. Based on the absolute $M_{K'}$ magnitudes, we infer masses (from hot-start evolutionary models) and projected separations of $10 \pm 4$ $M_{Jup}$ and $330 \pm 30$ AU for FW Tau b, $16 \pm 4$ $M_{Jup}$ and $210 \pm 20$ AU for ROXs 12 b, and $10 \pm 4$ $M_{Jup}$ and $140 \pm 10$ AU for ROXs 42B b. We also present similar observations for ten other candidates which show that they are unassociated field stars, as well as multicolor $JHK'L'$ near-infrared photometry for our new PMCs and for five previously-identified substellar or planetary-mass companions. The NIR photometry for our sample of eight known and new companions generally parallels the properties of free-floating low-mass brown dwarfs in these star-forming regions. However, 5 of the 7 objects with $M < 30 M_{Jup}$ are redder in $K'-L'$ than the distribution of young free-floating counterparts of similar $J-K'$. We speculate that this distinction could indicate a structural difference in circum-planetary disks, perhaps tied to higher disk mass since at least two of the objects in our sample are known to be accreting more vigorously than typical free-floating counterparts.
ROXs 42Bb is of course mentioned here:
http://solar-flux.forumandco.com/t1418-roxs-42b-young-binary-m-dwarf-with-substellar-companions

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## Re: ROXs 12 b and FW Tau b

Perhaps discussion could be merged. I'd also like to highlight this statement:

The binary survey by Ratzka et al. (2005) also identified a faint candidate companion at a much wider projected separation (∼1.1′′; ∼140 AU) in the shift-andadded stack of their speckle data. However, it has been neglected in the subsequent literature, so we observed the system in 2011 and 2012 to confirm its existence (Figure 2, left) and test for common proper motion (Figure 2, right). Our observations recovered the candidate companion, but as can be seen in Figure 2 (left), they also revealed another candidate companion even closer to ROXs 42B ( = 0.55′′; ∼70 AU).

That is ROXs 42 B cc1 ("ROXs 42 Bc" or "ROXs (ABC)c") yet to be confirmed, I suppose. And then...

As we show in Figure 2 (right), the outer candidate is indeed a comoving companion to ROXs 42B, with a relative motion of 0.7±1.6 mas/yr (∼0.5 km/s) with respect to the photocenter of the central binary. [...] Given its bound nature and apparently planetary mass, we hereafter denote the companion (with some regret regarding the nomenclature) as “ROXs 42B (AB) b”, or “ROXs 42B b” for simplicity.

For even more simplicity... isn't it easier ROXs 42 (ABC)b??

I repost the visual configuration if it could help.

We have:

ROXs A-B: a = 56 milliarcsec = ca. 7.6 AUs

ROXs 42 AB-C: a = 0.157 arcsec = ca. 23 AUs

ROXs 42 Ca-Cb: a = 0.00195 arcsec (=1.95 milliarcsec) = ca. 0.26 AUs (with Porb=39 days).

"ROXs 42 Bb" (or (ABC)b...): a = 150 AUs

I would call it "circumquaterary" planet/companion, since orbiting two spectroscopic binaries.

Edasich
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## Re: ROXs 12 b and FW Tau b

I think the general concensus here is that ROXs 42B is a binary system and the planet is a circumbinary planet. See here.
ROXs 42 A, B and C are physically unrelated to each other.

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## Re: ROXs 12 b and FW Tau b

This is in fact noted in the paper itself. See footnote 8:
Regarding nomenclature, we note that the “B” in ROXs 42B indicates that it is the second-brightest optical counterpart in the error circle for the X-ray source ROXs 42. It does not denote anything regarding the binarity of the system (which is unlikely to be associated with ROXs 42A or ROXs 42C).
In fact, they denote the individual stars in this binary system as "ROXs 42B A" and "ROXs 42B B", the companion as "ROXs 42B (AB) b" or "ROXs 42B b" for short.

Lazarus
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## Re: ROXs 12 b and FW Tau b

So the C component is to be considered an unrelated spectroscopic/eclipsing pair then. I wanted it to be quadruple...

Anyway ROXs 12 b and FW Tau b have been added to EPE's count, though I still don't understand which planet has been removed from the count:

http://exoplanet.eu/catalog/roxs_12_b/
http://exoplanet.eu/catalog/fw_tau_b/

Edasich
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## Re: ROXs 12 b and FW Tau b

FW Tau b may be a low-mass star instead.

An ALMA Dynamical Mass Estimate of the Proposed Planetary-mass Companion FW Tau C
https://arxiv.org/abs/1708.08122

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## Re: ROXs 12 b and FW Tau b

Update on ROXs 12 B, there is an additional companion star 2MASS J16262774-2527247. The system is misaligned, which is the norm for wide stellar systems.

Bowler et al. "The Young Substellar Companion ROXs 12 B: Near-Infrared Spectrum, System Architecture, and Spin-Orbit Misalignment"
https://arxiv.org/abs/1708.07611

Lazarus
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