Precise radial velocities of giant stars
Affiliation
Univ Arizona, Dept AstronIssue Date
2016-10-28Keywords
planetary systemsplanets and satellites: formation
planets and satellites: fundamental parameters
planets and satellites: gaseous planets
planets and satellites: detection
planets and satellites: general
Metadata
Show full item recordPublisher
EDP SCIENCES S ACitation
Precise radial velocities of giant stars 2016, 595:A55 Astronomy & AstrophysicsJournal
Astronomy & AstrophysicsRights
© ESO, 2016Collection Information
This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.Abstract
Context. For over 12 yr, we have carried out a precise radial velocity (RV) survey of a sample of 373 G- and K-giant stars using the Hamilton Echelle Spectrograph at the Lick Observatory. There are, among others, a number of multiple planetary systems in our sample as well as several planetary candidates in stellar binaries. Aims. We aim at detecting and characterizing substellar and stellar companions to the giant star HD 59686 A (HR 2877, HIP 36616). Methods. We obtained high-precision RV measurements of the star HD 59686 A. By fitting a Keplerian model to the periodic changes in the RVs, we can assess the nature of companions in the system. To distinguish between RV variations that are due to non-radial pulsation or stellar spots, we used infrared RVs taken with the CRIRES spectrograph at the Very Large Telescope. Additionally, to characterize the system in more detail, we obtained high-resolution images with LMIRCam at the Large Binocular Telescope. Results. We report the probable discovery of a giant planet with a mass of m(p) sin i = 6.92(-0.24)(+0.18) M-Jup orbiting at a(p) = 1.0860(-0.0007)(+0.0006) aufrom the giant star HD 59686 A. In addition to the planetary signal, we discovered an eccentric (e(B) = 0.729(-0.003)(+0.004)) binary companionwith a mass of m(B) sin i = 0.5296(-0.0008)(+0.0011) M-circle dot orbiting at a close separation from the giant primary with a semi-major axis of a(B) = 13.56(-0.14)(+0.18) au. Conclusions. The existence of the planet HD 59686 Ab in a tight eccentric binary system severely challenges standard giant planet formation theories and requires substantial improvements to such theories in tight binaries. Otherwise, alternative planet formation scenarios such as second-generation planets or dynamical interactions in an early phase of the system's lifetime need to be seriously considered to better understand the origin of this enigmatic planet.Note
Open Access Journal.ISSN
0004-63611432-0746
Version
Final published versionSponsors
National Aeronautics and Space Administration; National Science Foundation; Hong Kong RGC grant [HKU 17305015]Additional Links
http://www.aanda.org/10.1051/0004-6361/201628791Scopus Count
Collections
Related items
Showing items related by title, author, creator and subject.
-
Composition of Jupiter irregular satellites sheds light on their origin(EDP SCIENCES S A, 2017-12-08)Context. Irregular satellites of Jupiter with their highly eccentric, inclined and distant orbits suggest that their capture took place after the giant planet migration. Aims. We aim to improve our understanding of the surface composition of irregular satellites of Jupiter to gain insight into a narrow time window when our solar system was forming. Methods. We observed three Jovian irregular satellites, Himalia (JVI), Elara (JVII), and Carme (JXI), using a medium-resolution 0.8-5.5 mu m spectrograph, SpeX on the NASA Infrared Telescope Facility (IRTF). Using a linear spectral unmixing model we have constrained the major mineral phases on the surface of these three bodies. Results. Our results confirm that the surface of Himalia (JVI), Elara (JVII), and Carme (JXI) are dominated by opaque materials such as those seen in carbonaceous chondrite meteorites. Our spectral modeling of NIR spectra of Himalia and Elara confirm that their surface composition is the same and magnetite is the dominant mineral. A comparison of the spectral shape of Himalia with the two large main C-type asteroids, Themis (D similar to 176 km) and Europa (D similar to 352 km), suggests surface composition similar to Europa. The NIR spectrum of Carme exhibits blue slope up to 1.5 mu m and is spectrally distinct from those of Himalia and Elara. Our model suggests that it is compositionally similar to amorphous carbon. Conclusions. Himalia and Elara are compositionally similar but di ff er significantly from Carme. These results support the hypotheses that the Jupiter's irregular satellites are captured bodies that were subject to further breakup events and clustered as families based on their similar physical and surface compositions.
-
EFFECT OF SURFACE-MANTLE WATER EXCHANGE PARAMETERIZATIONS ON EXOPLANET OCEAN DEPTHS(IOP PUBLISHING LTD, 2016-11-16)Terrestrial exoplanets in the canonical habitable zone may have a variety of initial water fractions due to random volatile delivery by planetesimals. If the total planetary water complement is high, the entire surface may be covered in water, forming a "waterworld." On a planet with active tectonics, competing mechanisms act to regulate the abundance of water on the surface by determining the partitioning of water between interior and surface. Here we explore how the incorporation of different mechanisms for the degassing and regassing of water changes the volatile evolution of a planet. For all of the models considered, volatile cycling reaches an approximate steady state after similar to 2 Gyr. Using these steady. states, we find that if volatile cycling is either solely dependent on temperature or seafloor pressure, exoplanets require a high abundance (greater than or similar to 0.3% of total mass) of water to have fully inundated surfaces. However, if degassing is more dependent on seafloor pressure and regassing mainly dependent on mantle temperature, the degassing rate is relatively large at late times and a steady. state between degassing and regassing is reached with a substantial surface water fraction. If this hybrid model is physical, super-Earths with a total water fraction similar to that of the Earth can become waterworlds. As a result, further understanding of the processes that drive volatile cycling on terrestrial planets is needed to determine the water fraction at which they are likely to become waterworlds.
-
Exoplanet Classification and Yield Estimates for Direct Imaging Missions(IOP PUBLISHING LTD, 2018-03-30)Future NASA concept missions that are currently under study, like the Habitable Exoplanet Imaging Mission (HabEx) and the Large Ultra-violet Optical Infra Red Surveyor, could discover a large diversity of exoplanets. We propose here a classification scheme that distinguishes exoplanets into different categories based on their size and incident stellar flux, for the purpose of providing the expected number of exoplanets observed (yield) with direct imaging missions. The boundaries of this classification can be computed using the known chemical behavior of gases and condensates at different pressures and temperatures in a planetary atmosphere. In this study, we initially focus on condensation curves for sphalerite ZnS, H2O, CO2, and CH4. The order in which these species condense in a planetary atmosphere define the boundaries between different classes of planets. Broadly, the planets are divided into rocky planets (0.5-1.0 R-circle plus), super-Earths (1.0-1.75 R-circle plus), sub-Neptunes (1.75-3.5 R-circle plus), sub-Jovians (3.5-6.0 R-circle plus), and Jovians (6-14.3 R-circle plus) based on their planet sizes, and "hot," "warm," and "cold" based on the incident stellar flux. We then calculate planet occurrence rates within these boundaries for different kinds of exoplanets, eta(planet), using the community coordinated results of NASA's Exoplanet Program Analysis Group's Science Analysis Group-13 (SAG-13). These occurrence rate estimates are in turn used to estimate the expected exoplanet yields for direct imaging missions of different telescope diameters.
