Cluster planet IC 4651 9122 b

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Cluster planet IC 4651 9122 b

Post by Sirius_Alpha on 9th July 2018, 9:14 pm

On the incidence of planet candidates in open clusters and a planet confirmation
https://arxiv.org/abs/1807.03196

Detecting exoplanets in clusters of different ages is a powerful tool for understanding a number of open questions, such as how the occurrence rate of planets depends on stellar metallicity, on mass, or on stellar environment. We present the first results of our HARPS long-term radial velocity (RV) survey which aims to discover exoplanets around intermediate-mass (between ~ 2 and 6 Msun) evolved stars in open clusters. We selected 826 bona fide HARPS observations of 114 giants from an initial list of 29 open clusters and computed the half peak-to-peak variability of the HARPS RV measurements, namely DeltaRV/2, for each target, to search for the best planet-host candidates. We also performed time series analysis for a few targets with enough observations to search for orbital solutions. Although we attempted to rule out the presence of binaries on the basis of previous surveys, we detected 14 new binary candidates in our sample, most of them identified from a comparison between HARPS and CORAVEL data. We also suggest 11 new planet-host candidates based on a relation between the stellar surface gravity and DeltaRV/2. Ten of the candidates have less than 3 Msun, showing evidence of a low planet occurrence rate for massive stars. One of the planet-host candidates and one of the binary candidates show very clear RV periodic variations, allowing us to confirm the discovery of a new planet and to compute the orbital solution for the binary. The planet is IC 4651 9122b, with a minimum mass of msini = 6.3 MJ and a semi-major axis a = 2.0 AU. The binary companion is NGC 5822 201B, with a very low minimum mass of msini = 0.11 Msun and a semi-major axis a = 6.5 AU, which is comparable to the Jupiter distance to the Sun.

SIMBAD link for star:
http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Cl*+IC+4651+MMU+9122&NbIdent=1&Radius=2&Radius.unit=arcmin&submit=submit+id


Last edited by Sirius_Alpha on 10th July 2018, 8:32 pm; edited 1 time in total

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Re: Cluster planet IC 4651 9122 b

Post by Lazarus on 10th July 2018, 3:05 pm

To find the star in SIMBAD, use "Cl* IC 4651 MMU 9122"
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Re: Cluster planet IC 4651 9122 b

Post by Sirius_Alpha on 10th July 2018, 8:32 pm

Thanks! I've thrown in a SIMBAD link in the original post.

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Re: Cluster planet IC 4651 9122 b

Post by Edasich on 11th July 2018, 5:02 am

I had to browse through Vizier catalogs to get some information about stellar parameters (not provided in discovery paper, neither the mass). So we're dealing with a 2.4 Gyrs-old, 1.83 MSun K-giant 58-60 times more luminous than Sun. Another evolved exoplanet host, then. Smile

An average metallicity of 0.21 is estimated, no clue about distance from Sun, but likely within 890-900 pc.
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Re: Cluster planet IC 4651 9122 b

Post by Lazarus on 11th July 2018, 3:24 pm

The paper notes that they are looking for planets around evolved host stars. They are assuming all the target stars are at the main sequence turnoff for the cluster, details of which are given in table 4. For IC 4651, this is 2.1 solar masses, with a metallicity of +0.12 dex and an age of about 1.1 Gyr.

The Gaia DR2 parallax on SIMBAD page is 1.1372▒0.0429 milliarcseconds. Na´ve conversion of parallax to distance using 1/parallax gives 879▒33 parsecs, though the na´ve conversion leads to biased estimates.
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