91 Aquarii and Tau Geminorum

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91 Aquarii and Tau Geminorum

Post by Lazarus on 23rd May 2013, 2:11 am

Precise radial velocities of giant stars V. A brown dwarf and a planet orbiting the K giant stars tau Gem and 91 Aqr
http://fr.arxiv.org/abs/1305.5107

IIRC these two have been listed in various planet catalogues for quite some time based on being presented in conferences.
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Re: 91 Aquarii and Tau Geminorum

Post by Edasich on 23rd May 2013, 4:08 am

For nearly 9-10 years...

I wonder what's with Iota Aurigae too.
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Re: 91 Aquarii and Tau Geminorum

Post by Shellface on 23rd May 2013, 6:12 pm

Uhh…
Received 1 January 2001/Accepted 1 January 2001
what? Is that what happens when those are left as the defaults? I hope so.

Ignoring that, why have these been kept away from a proper paper for ten years?! The whole CRIRES measurements aren't exactly the entire confirmation of not-keplerian-siney-boo, and planets from the same survey that were detected much later were paper'd a long time ago (HD 210702, etc).

The other two systems from the original announcement, Nu Oph and HD 59686, have had their data appear in other papers (1, 2), with the former being in a two-brute system while the latter seems to be some sort of false positive involving stellar components (binarity of the secondary?) Maybe those will get a paper in the series?

Concerning these two: Tau Gem was probably a late B star when on the main sequence and is currently approaching the transition to bright gianthood, while 91 Aqr was an F dwarf and is currently a typical giant. 91 Aquarii is in a 40 Eridani-like triple system, so it was once not the most massive component.

91 Aquarii Ab seems to be a typical, if massive, AU Jovian, within expectations for an approximately mid F-dwarf. However, Tau Gem b (and Nu Oph bc) are clear examples that planet formation gets really… weird in the top percentage of the stellar mass hierarchy. The zone where gas should be cleared out in the protoplanetary disk gets very large (>10 AU?) for B-stars, so how could such massive companions form and then migrate, even twice in the same system? The line:
Our results show that red giant stars with masses greater than 2.7 M⊙ host very few planets (Reffert et al. in prep.)
suggests that core accretion really does struggle at the top.

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Re: 91 Aquarii and Tau Geminorum

Post by Lazarus on 24th May 2013, 4:18 pm

Do you have a reference for 91 Aquarii containing a white dwarf star? The most I've been able to find is that the overall spectrum of the BC binary is K-type.
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Re: 91 Aquarii and Tau Geminorum

Post by Shellface on 24th May 2013, 9:14 pm

I'm… not sure. I think I'm remembering it from the wikipedia article which lists its spectral type as D, which is white dwarf, but I can't find anything in literature either. The component mass is consistent with both an early K dwarf or a WD, but considering that the subsystem B-V is consistent with ~K3.5 it's likely that both components are orange dwarfs.

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Re: 91 Aquarii and Tau Geminorum

Post by Lazarus on 25th May 2013, 5:21 am

Ah ha I think Wikipedia has interpreted the SIMBAD quality flag (D) on the combined spectral type of the BC components to be the spectral type of star C.

For the individual components, SIMBAD gives K6 for star B and does not list a spectral type for the C component.

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Re: 91 Aquarii and Tau Geminorum

Post by Edasich on 12th October 2015, 4:34 am

Thread bump. After years of waiting it's been possible to access David S. Mitchell's original PhD thesis announcing detection of extrasolar planets around Tau Gem, 91 (Psi1) Aqr and other K giant stars.

http://works.bepress.com/dsmitche/12

It's really worth browsing... cyclops
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