2-planet system around red giant branch star HD 121056

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HIP 67851 - Jupiter and super-Jupiter mass planets (and a brown dwarf at HIP 97233)

Post by Sirius_Alpha on 28th September 2014, 8:23 pm

A planetary system and a highly eccentric brown dwarf around the giant stars HIP67851 and HIP97233
http://arxiv.org/abs/1409.7429

Context: So far more than 60 substellar companions have been discovered around giant stars. These systems present physical and orbital properties that contrast to those detected orbiting less evolved stars. Aims: We are conducting a radial velocity survey of 166 bright giant stars in the southern hemisphere. The main goals of our project are to detect and characterize planets in close-in orbits around giant stars in order to study the effects of the host star evolution on their orbital and physical properties. Methods: We have obtained precision radial velocities for the giant stars HIP67851 and HIP97233 that have revealed periodic signals, which are most likely induced by the presence of substellar companions. Results: We present the discovery of a planetary system and an eccentric brown dwarf orbiting the giant stars HIP67851 and HIP97233, respectively. The inner planet around HIP67851 has a period of 88.8 days, a projected mass of 1.4 Mjup and an eccentricity of 0.09. After Kepler 91b, HIP67851b is the closest-in known planet orbiting a giant star. Although the orbit of the outer object is not fully constrained, it is likely a super-Jupiter. The brown dwarf around HIP97233 has an orbital period of 1058.8 days, a minimum mass of 20.0 Mjup and an eccentricity of 0.61. This is the most eccentric known brown dwarf around a giant star.

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2-planet system around red giant branch star HD 121056

Post by Edasich on 23rd December 2014, 4:28 am

The Pan-Pacific Planet Search. II. Confirmation of a two-planet system around HD 121056

Precise radial velocities from the Anglo-Australian Telescope confirm the presence of a rare short-period planet around the K0 giant HD 121056. An independent two-planet solution using the AAT data shows that the inner planet has P=89.1+/-0.1 days, and m sin i=1.35+/-0.17 Mjup. These data also confirm the planetary nature of the outer companion, with m sin i=3.9+/-0.6 Mjup and a=2.96+/-0.16 AU. HD 121056 is the most-evolved star to host a confirmed multiple-planet system, and is a valuable example of a giant star hosting both a short-period and a long-period planet.
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Re: 2-planet system around red giant branch star HD 121056

Post by Shellface on 23rd December 2014, 7:39 am

Dangit Edasich, it even said it was a confirmation

Figure 4 does suggest that RV surveys are missing short-period planets in the log g = 3 - 3.5 cgs range. I wonder where they are…

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Re: 2-planet system around red giant branch star HD 121056

Post by Lazarus on 23rd December 2014, 8:02 am

Yeah HD 121056 = HIP 67851. Those pesky astronomers and their overlapping star catalogues! Smile
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Re: 2-planet system around red giant branch star HD 121056

Post by Sirius_Alpha on 23rd December 2014, 8:54 am


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Re: 2-planet system around red giant branch star HD 121056

Post by Sirius_Alpha on 25th May 2015, 9:32 pm

Second planet at HIP 67851, and a couple planets around other intermediate-mass stars.

Giant planets around two intermediate-mass evolved stars and confirmation of the planetary nature of HIP67851 c
http://arxiv.org/abs/1505.06718

Precision radial velocities are required to discover and characterize planets orbiting nearby stars. Optical and near infrared spectra that exhibit many hundreds of absorption lines can allow the m/s precision levels required for such work. However, this means that studies have generally focused on solar-type dwarf stars. After the main-sequence, intermediate-mass stars (former A-F stars) expand and rotate slower than their progenitors, thus thousands of narrow absorption lines appear in the optical region, permitting the search for planetary Doppler signals in the data for these types of stars. We present the discovery of two giant planets around the intermediate-mass evolved star HIP65891 and HIP107773. The best Keplerian fit to the HIP65891 and HIP107773 radial velocities leads to the following orbital parameters: P=1084.5 d; mbsini = 6.0 Mjup; e=0.13 and P=144.3 d; mbsini = 2.0 Mjup; e=0.09, respectively. In addition, we confirm the planetary nature of the outer object orbiting the giant star HIP67851. The orbital parameters of HIP67851c are: P=2131.8 d, mcsini = 6.0 Mjup and e=0.17. With masses of 2.5 M⊙ and 2.4 M⊙ HIP65891 and HIP107773 are two of the most massive stars known to host planets. Additionally, HIP67851 is one of five giant stars that are known to host a planetary system having a close-in planet (a< 0.7 AU). Based on the evolutionary states of those five stars, we conclude that close-in planets do exist in multiple systems around subgiants and slightly evolved giants stars, but probably they are subsequently destroyed by the stellar envelope during the ascent of the red giant branch phase. As a consequence, planetary systems with close-in objects are not found around horizontal branch stars.

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Re: 2-planet system around red giant branch star HD 121056

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