Journal articles: 'Stars with planets'

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MacCAIG, Norman. "Stars and planets." Medicine, Conflict and Survival 14, no. 3 (July 1998): 272. http://dx.doi.org/10.1080/13623699808409404.

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Hirano, Teruyuki, Bun'ei Sato, Kento Masuda, Othman Michel Benomar, Yoichi Takeda, Masashi Omiya, and Hiroki Harakawa. "Search for Close-in Planets around Evolved Stars with Phase-curve variations and Radial Velocity Measurements." Proceedings of the International Astronomical Union 11, A29A (August 2015): 63–64. http://dx.doi.org/10.1017/s1743921316002404.

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AbstractTidal interactions are a key process to understand the evolution history of close-in exoplanets. But tidals still have a large uncertainty in their prediction for the damping timescales of stellar obliquity and semi-major axis. We have worked on a search for transiting giant planets around evolved stars, for which few close-in planets were discovered. It has been reported that evolved stars lack close-in planets, which is often attributed to the tidal evolution and/or engulfment of close-in planets by the hosts. Meanwhile, Kepler has detected a certain fraction of transiting planet candidates around evolved stars. Confirming the planetary nature for these candidates is especially important since the comparison between the occurrence rates of close-in planets around main sequence stars and evolved stars provides a unique opportunity to discuss the final stage of close-in planets. With the aim of confirming KOI planet candidates around evolved stars, we measured precision radial velocities (RVs) for evolved stars with transiting planet candidates using Subaru/HDS. We also developed a new code which simultaneously models and fits the observed RVs and phase-curve variations in the Kepler data (e.g., transits, stellar ellipsoidal variations, and planet emission/reflected light). As a result of applying the global fit to KOI giants/subgiants, we confirmed two giant planets around evolved stars (Kepler-91 and KOI-1894), as well as revealed that KOI-977 is more likely a false positive.

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Carlberg, Joleen K., Steven R. Majewski, Verne V. Smith, Katia Cunha, Richard J. Patterson, Dmitry Bizyaev, Phil Arras, and Robert T. Rood. "A New Spin on Red Giant Rapid Rotators: Evidence for Chemical Exchange Between Planets and Evolved Stars." Proceedings of the International Astronomical Union 5, S265 (August 2009): 408–11. http://dx.doi.org/10.1017/s1743921310001092.

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AbstractRapid rotation in red giant stars may be one signature of the past engulfment of a planetary companion. Models of the future tidal interaction of known exoplanet host stars with their planets show that many of these stars will accrete one or more of their planets, and the orbital angular momentum of these accreted planets is sometimes sufficient to spin up the host stars to a level commonly accepted as “rapid rotation” for giant stars. Planets accreted during the red giant phase should leave behind a chemical signature in the form of unusual abundance patterns in the host red giant's atmosphere. Proposed signatures of planet accretion include the enhancement of Li and 12C; both species are generally depleted in giant star atmospheres by convection but could be replenished by planet accretion. Moreover, accreted planets may preferentially enhance the stellar abundance of refractory elements assuming that the refractory nature of these elements leads to their relative enhancements in the planets themselves. Here we present preliminary results of a search for these predicted chemical signatures through high resolution spectroscopic abundance analysis of both rapidly rotating giant stars (i.e., stars with a higher probability of having experienced planet accretion) and normally rotating giant stars. We find that the rapid rotators are enhanced in Li relative to the slow rotators — a result consistent with Li replenishment through planet absorption.

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Dvorak, R., E. Pilat-Lohinger, E. Bois, B. Funk, F. Freistetter, and L. Kiseleva-Eggleton. "Planets in Double Stars: The ϒ Cephei System." International Astronomical Union Colloquium 191 (August 2004): 222–26. http://dx.doi.org/10.1017/s0252921100008800.

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AbstractUp to now we have evidence for some 15 planets moving in double stars. They are all of the so-called S-type, which means that they are orbiting one of the primaries. Only two of the binaries have separations in the order of the distances where the planets in our Solar system orbit the Sun, namely Gliese 86 and ϒ Cep. In this study we investigate the stability of the recently discovered planet in ϒ Cep with respect to the orbital parameters of the binary and of the planet. Additionally we check the region inside and outside the planet’s orbit (a = 2.1 AU). Even when the mass of an additional planet in 1 AU would be in the order of that of Jupiter, the discovered planet would be in a stable orbit.

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Marcy, G. W., R. Paul Butler, and D. A. Fischer. "Doppler Detection of Extrasolar Planets." International Astronomical Union Colloquium 170 (1999): 121–30. http://dx.doi.org/10.1017/s0252921100048466.

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AbstractWe have measured the radial velocities of 540 G and K main sequence stars with a precision of 3−10 ms−1 using the Lick and Keck échelle spectrometers. We had detected 6 companions that have m sin i < 7 MJup. We announce here the discovery of a new planet around Gliese 876, found in our Doppler measurements from both Lick and Keck. This is the first planet found around an M dwarf, which indicates that planets occur around low-mass stars, in addition to solar-type stars. We combine our entire stellar sample with that of Mayor et al. to derive general properties of giant planets within a few AU of these stars. Less than 1% of G and K main sequence stars harbor brown dwarf companions with masses between 5 and 70 MJup. Including Gliese 876b, 8 companions exhibit m sin i < 5 MJup which constitute the best planet candidates to date. Apparently, 4% of stars have planetary companions within the range m sin i = 0.5 to 5 MJup. Planets are distinguished from brown dwarfs by the discontinuous jump in the mass function at 5 MJup. About 2/3 of the planets orbit within just 0.3 AU due in part to their favorable detectability, but also possibly due to a real “pile up” of planets near the star. Inward orbital migration after formation may explain this, but the mechanism to stop the migration remains unclear. Five of eight planets have orbital eccentricities greater than that of our Jupiter, eJup = 0.048, and tidal circularization may explain most of the circular orbits. Thus, eccentric orbits are common and may arise from gravitational interactions with other planets, stars, or the protoplanetary disk. The planet-bearing stars are systematically metal-rich, as is the Sun, compared to the solar neighborhood.

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Underwood, D. R., B. W. Jones, and P. N. Sleep. "The evolution of habitable zones during stellar lifetimes and its implications on the search for extraterrestrial life." International Journal of Astrobiology 2, no. 4 (October 2003): 289–99. http://dx.doi.org/10.1017/s1473550404001715.

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A stellar evolution computer model has been used to determine changes in the luminosity L and effective temperature Te of single stars during their time on the main sequence. The range of stellar masses investigated was from 0.5 to 1.5 times that of the Sun, each with a mass fraction of metals (metallicity, Z) from 0.008 to 0.05. The extent of each star's habitable zone (HZ) has been determined from its values of L and Te. These stars form a reference framework for other main sequence stars. All of the 104 main sequence stars known to have one or more giant planets have been matched to their nearest stellar counterpart in the framework, in terms of mass and metallicity, hence closely approximating their HZ limits. The limits of HZ, for each of these stars, have been compared to their giant planet(s)'s range of strong gravitational influence. This allows a quick assessment as to whether Earth-mass planets could exist in stable orbits within the HZ of such systems, both presently and at any time during the star's main sequence lifetime. A determination can also be made as to the possible existence of life-bearing satellites of giant planets, which orbit within HZs. Results show that about half of the 104 known extrasolar planetary systems could possibly have been housing an Earth-mass planet in HZs during at least the past billion years, and about three-quarters of the 104 could do so for at least a billion years at some time during their main sequence lives. Whether such Earth-mass planets could have formed is an urgent question now being investigated by others, with encouraging results.

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Beichman, C. A., S. C. Unwin, M. Shao, A. M. Tanner, J. H. Catanzarite, and G. W. Marcy. "Astrometric planet searches with SIM PlanetQuest." Proceedings of the International Astronomical Union 3, S248 (October 2007): 238–43. http://dx.doi.org/10.1017/s1743921308019169.

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AbstractSIM will search for planets with masses as small as the Earth's orbiting in the ‘habitable zones’ around more than 100 of the nearest stars and could discover many dozen if Earth-like planets are common. With a planned “Deep Survey” of 100–450 stars (depending on desired mass sensitivity) SIM will search for terrestrial planets around all of the candidate target stars for future direct detection missions such as Terrestrial Planet Finder and Darwin. SIM's “Broad Survey” of 2100 stars will characterize single and multiple-planet systems around a wide variety of stellar types, including many now inaccessible with the radial velocity technique. In particular, SIM will search for planets around young stars providing insights into how planetary systems are born and evolve with time.

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Hidas, M. G., J. K. Webb, M. C. B. Ashley, C. H. Lineweaver, J. Anderson, and M. Irwin. "Searching for Extrasolar Planets Using Transits." Symposium - International Astronomical Union 213 (2004): 77–79. http://dx.doi.org/10.1017/s0074180900193015.

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The presence of an extrasolar planet can be revealed when it passes in front of its host star, reducing the star's apparent brightness by ∼ 1%. We are monitoring a large sample (of order 104) of stars using our own 0.5 m telescope at Siding Spring Observatory, Australia, in search of such transiting planets.

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Gazzano, Jean-Christophe, Magali Deleuil, Patrick De Laverny, Alejandra Recio Blanco, François Bouchy, Davide Gandolfi, and Benoît Loeillet. "From stars to planets." Proceedings of the International Astronomical Union 4, S253 (May 2008): 404–5. http://dx.doi.org/10.1017/s174392130802677x.

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AbstractA large program of multi-fibre (FLAMES) spectroscopic observations of the stellar population in two CoRoT/Exoplanet field with the GIRAFFE/VLT, took place in spring 2008. It aims at characterizing the brightest dwarf population and providing the ground for statistical analysis of the planetary population found by CoRoT.To perform such an ambitious analysis, we use an automated software based on the MATISSE algorithm, originally designed for the GAIA/RVS spectral analysis. This software derives the atmospheric stellar parameters: effective temperature, surface gravity and the overall metallicity.Further improvements are foreseen in order to measure also individual abundances. By comparing the main physical and chemical properties of the host stars to those of the stellar population they belong to, this will bring new insights into the formation and evolution of exoplanetary systems and the star-planet connection.

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Moya, A. "Pulsating stars harbouring planets." EPJ Web of Conferences 47 (2013): 09005. http://dx.doi.org/10.1051/epjconf/20134709005.

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Nielsen, Eric L., Michael C. Liu, Zahed Wahhaj, Beth A. Biller, and Thomas L. Hayward. "The Gemini NICI Planet-Finding Campaign: The Frequency of Giant Planets around Young B and A Stars." Proceedings of the International Astronomical Union 8, S299 (June 2013): 60–61. http://dx.doi.org/10.1017/s1743921313007874.

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AbstractWe have carried out high contrast imaging of 70 young, nearby B and A stars to search for brown dwarf and planetary companions as part of the Gemini NICI Planet-Finding Campaign. Our survey represents the largest, deepest survey for planets around high-mass stars (≈1.5–2.5 M⊙) conducted to date and includes the planet hosts β Pic and Fomalhaut. Despite detecting two new brown dwarfs, our observations did not detect new planets around our target stars, and we present upper limits on the fraction of high-mass stars that can host giant planets that are consistent with our null result.

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Lissauer, Jack J. "Formation, Frequency and Spacing of Habitable Planets." International Astronomical Union Colloquium 161 (January 1997): 289–97. http://dx.doi.org/10.1017/s0252921100014809.

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AbstractModels of planet formation and of the orbital stability of planetary systems are described and used to discuss estimates of the abundance of habitable planets which may orbit stars within our galaxy. Modern theories of star and planet formation, which are based upon observations of the Solar System and of young stars and their environments, predict that most single stars should have rocky planets in orbit about them. Terrestrial planets are believed to grow via pairwise accretion until the spacing of planetary orbits becomes large enough that the configuration is stable for the age of the system. Giant planets orbiting within or near the habitable zone could either prevent terrestrial planets from forming, destroy such planets or remove them from habitable zones. The implications of the giant planets found in recent radial velocity searches for the abundances of habitable planets are discussed.

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Marcy, Geoffrey W., R. Paul Butler, Steven S. Vogt, and Debra A. Fischer. "Extrasolar Planets and Prospects for Terrestrial Planets." Symposium - International Astronomical Union 213 (2004): 11–24. http://dx.doi.org/10.1017/s0074180900192903.

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Examination of ∼2000 sun–like stars has revealed 97 planets (as of 2002 Nov), all residing within our Milky Way Galaxy and within ∼200 light years of our Solar System. They have masses between 0.1 and 10 times that of Jupiter, and orbital sizes of 0.05–5 AU. Thus planets occupy the entire detectable domain of mass and orbits. News & summaries about extrasolar planets are provided at: http://exoplanets.org. These planets were all discovered by the wobble of the host stars, induced gravitationally by the planets, causing a periodicity in the measured Doppler effect of the starlight. Earth–mass planets remain undetectable, but space–based missions such as Kepler, COROT and SIM may provide detections of terrestrial planets within the next decade.The number of planets increases with decreasing planet mass, indicating that nature makes more small planets than jupiter–mass planets. Extrapolation, though speculative, bodes well for an even larger number of earth–mass planets. These observations and the theory of planet formation suggests that single sun–like stars commonly harbor earth–sized rocky planets, as yet undetectable. The number of planets increases with increasing orbital distance from the host star, and most known planets reside in non–circular orbits. Many known planets reside in the habitable zone (albeit being gas giants) and most newly discovered planets orbit beyond 1 AU from their star. A population of Jupiter–like planets may reside at 5–10 AU from stars, not easily detectable at present. The sunlike star 55 Cancri harbors a planet of 4–10 Jupiter masses orbiting at 5.5 AU in a low eccentricity orbit, the first analog of our Jupiter, albeit with two large planets orbiting inward.To date, 10 multiple–planet systems have been discovered, with four revealing gravitational interactions between the planets in the form of resonances. GJ 876 has two planets with periods of 1 and 2 months. Other planetary systems are “hierarchical”, consisting of widely separated orbits. These two system architectures probably result from gravitational interactions among the planets and between the planets and the proto-planetary disk out of which they formed.

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Valenti, Jeff A. "Metallicity and Planet Formation – Observations." Proceedings of the International Astronomical Union 5, S265 (August 2009): 403–7. http://dx.doi.org/10.1017/s1743921310001080.

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AbstractEarly abundance measurements established that stars known to host giant planets are metal rich compared to the Sun. More extensive abundance measurements then showed that giant planet hosts are metal rich compared to the parent sample in planet searches. Stars spanning a range of convection zone depths all show the same metallicity effect, ruling out significant abundance enhancements due to selective accretion. Most known planets migrated inwards from the snow line, but subsamples closer to and further from the star have similar iron abundances, so the stopping point of migration does not depend on metallicity. Stars recently discovered to host Neptune mass planets may be metal poor compared to the Sun, particularly if one focusses on stars that do not also host higher mass planets. This would be consistent with core-accretion models of planet formation. Before drawing physical conclusions, it will be necessary to check for metallicity bias in the subsample of stars around which Neptune mass planets could have been found. M dwarf abundances are currently too uncertain to relate planet frequency and host star metallicity, due mainly to missing or incorrect molecular line data.

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Saffe, C., P. Miquelarena, J. Alacoria, M. Flores, M. Jaque Arancibia, D. Calvo, G. Martín Girardi, M. Grosso, and A. Collado. "Chemical analysis of early-type stars with planets." Astronomy & Astrophysics 647 (March 2021): A49. http://dx.doi.org/10.1051/0004-6361/202040132.

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Aims. Our goal is to explore the chemical pattern of early-type stars with planets, searching for a possible signature of planet formation. In particular, we study a likely relation between the λ Boötis chemical pattern and the presence of giant planets. Methods. We performed a detailed abundance determination in a sample of early-type stars with and without planets via spectral synthesis. Fundamental parameters were initially estimated using Strömgren photometry or literature values and then refined by requiring excitation and ionization balances of Fe lines. We derived chemical abundances for 23 different species by fitting observed spectra with an iterative process. Synthetic spectra were calculated using the program SYNTHE together with local thermodynamic equilibrium ATLAS12 model atmospheres. We used specific opacities calculated for each star, depending on the individual composition and microturbulence velocity vmicro through the opacity sampling method. The complete chemical pattern of the stars were then compared to those of λ Boötis stars and other chemically peculiar stars. Results. We compared the chemical pattern of the stars in our sample (13 stars with planets and 24 stars without detected planets) with those of λ Boötis and other chemically peculiar stars. We have found four λ Boötis stars in our sample, two of which present planets and circumstellar disks (HR 8799 and HD 169142) and one without planets detected (HD 110058). We have also identified the first λ Boötis star orbited by a brown dwarf (ζ Del). This interesting pair, the λ Boötis star and brown dwarf, could help to test stellar formation scenarios. We found no unique chemical pattern for the group of early-type stars bearing giant planets. However, our results support, in principle, a suggested scenario in which giant planets orbiting pre-main-sequence stars possibly block the dust of the disk and result in a λ Boötis-like pattern. On the other hand, we do not find a λ Boötis pattern in different hot-Jupiter planet host stars, which does not support the idea of possible accretion from the winds of hot-Jupiters, recently proposed in the literature. As a result, other mechanisms should account for the presence of the λ Boötis pattern between main-sequence stars. Finally, we suggest that the formation of planets around λ Boötis stars, such as HR 8799 and HD 169142, is also possible through the core accretion process and not only gravitational instability.

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Butler, R. Paul, Geoffrey W. Marcy, Debra A. Fischer, Steven S. Vogt, C. G. Tinney, Hugh R. A. Jones, Alan J. Penny, and Kevin Apps. "Statistical Properties of Extrasolar Planets." Symposium - International Astronomical Union 202 (2004): 3–11. http://dx.doi.org/10.1017/s0074180900217397.

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The emerging statistical properties from the first 50 extrasolar planets are startlingly different from the picture that was imagined prior to 1995. About 0.75% of nearby solar type stars harbor jovian planets in 3 to 5 day circular orbits. Another ∽7% of stars have jupiter–mass companions orbiting in eccentric orbits within 3.5 AU. The mass distribution of substellar companions rises abruptly near 5 MJup and continues increasing down to the detection limit near 1 MJup-Orbital eccentricities correlate positively with semimajor axes, even for planets beyond the tidal circularization zone within 0.1 AU, distinguishing planets from binary stars. The planet bearing stars are metal–rich relative to both nearby stars and to the Sun. Analogs of Solar System planets have not been detected to date as they require precision of 3 m s−1 maintained for more than a decade.

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Bashi, D., S. Zucker, V. Adibekyan, N. C. Santos, L. Tal-Or, T. Trifonov, and T. Mazeh. "Occurrence rates of small planets from HARPS." Astronomy & Astrophysics 643 (November 2020): A106. http://dx.doi.org/10.1051/0004-6361/202038881.

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Context. The stars in the Milky Way thin and thick disks can be distinguished by several properties such as metallicity and kinematics. It is not clear whether the two populations also differ in the properties of planets orbiting the stars. In order to study this, a careful analysis of both the chemical composition and mass detection limits is required for a sufficiently large sample. Currently, this information is still limited only to large radial-velocity (RV) programs. Based on the recently published archival database of the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph, we present a first analysis of low-mass (small) planet occurrence rates in a sample of thin- and thick-disk stars. Aims. We aim to assess the effects of stellar properties on planet occurrence rates and to obtain first estimates of planet occurrence rates in the thin and thick disks of the Galaxy. As a baseline for comparison, we also aim to provide an updated value for the small close-in planet occurrence rate and compare it with the results of previous RV and transit (Kepler) works. Methods. We used archival HARPS RV datasets to calculate detection limits of a sample of stars that were previously analysed for their elemental abundances. For stars with known planets we first subtracted the Keplerian orbit. We then used this information to calculate planet occurrence rates according to a simplified Bayesian model in different regimes of stellar and planet properties. Results. Our results suggest that metal-poor stars and more massive stars host fewer low-mass close-in planets. We find the occurrence rates of these planets in the thin and thick disks to be comparable. In the iron-poor regimes, we find these occurrence rates to be significantly larger at the high-α region (thick-disk stars) as compared with the low-α region (thin-disk stars). In general, we find the average number of close-in small planets (2–100 days, 1–20M⊕) per star (FGK-dwarfs) to be: n¯p = 0.36 ± 0.05, while the fraction of stars with planets is Fh = 0.23−0.03+0.04. Qualitatively, our results agree well with previous estimates based on RV and Kepler surveys. Conclusions. This work provides a first estimate of the close-in small planet occurrence rates in the solar neighbourhood of the thin and thick disks of the Galaxy. It is unclear whether there are other stellar properties related to the Galactic context that affect small-planet occurrence rates, or if it is only the combined effects of stellar metal content and mass. A future larger sample of stars and planets is needed to address those questions.

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Sahu, Kailash C., Stefano Casertano, Jeff Valenti, Howard E. Bond, Thomas M. Brown, T. Ed Smith, Will Clarkson, et al. "Transiting Planets in the Galactic Bulge from SWEEPS Survey and Implications." Proceedings of the International Astronomical Union 4, S253 (May 2008): 45–53. http://dx.doi.org/10.1017/s1743921308026227.

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AbstractThe SWEEPS (Sagittarius Window Eclipsing Extrasolar Planet Search) program was aimed at detecting planets around stars in the Galactic bulge, not only to determine their physical properties, but also to determine whether the properties of planets found in the solar neighborhood, such as their frequency and the metallicity dependence, also hold for the planets in the Galactic bulge. We used the Hubble Space Telescope to monitor 180,000 F, G, K, and M dwarfs in the Galactic bulge continuously for 7 days in order to look for transiting planets. We discovered 16 candidate transiting extrasolar planets with periods of 0.6 to 4.2 days, including a possible new class of ultra-short period planets (USPPs) with P < 1 day. The facts that (i) the coverage in the monitoring program is continuous, (ii) most of the stars are at a known distance (in the Galctic bulge), (iii) monitoring was carried out in 2 passbands, and (iv) the images have high spatial resolution, were crucial in minimizing and estimating the false positive rates. We estimate that at least 45% of the candidates are genuine planets. Radial velocity observations of the two brightest host stars further support the planetary nature of the transiting companions. These results suggest that the planet frequency in the Galactic bulge is similar to that in the solar neighborhood. They also suggest that higher metallicity favors planet formation even in the Galactic bulge. The USPPs occur only around low-mass stars which may suggest that close-in planets around higher-mass stars are irradiately evaporated, or that planets are able to migrate to and survive in close-in orbits only around such old and low-mass stars.

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Haywood, Misha. "On the origin of giant planets and their hosts." Proceedings of the International Astronomical Union 5, S265 (August 2009): 434–35. http://dx.doi.org/10.1017/s1743921310001195.

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AbstractThe correlation between stellar metallicity and giant planets has been tentatively explained by the possible increase of planet formation probability in stellar disks with enhanced amount of metals. There are two caveats to this explanation. First, giant stars with planets do not show a metallicity distribution skewed towards metal-rich objects, as found for dwarfs. Second, the correlation with metallicity is not valid at intermediate metallicities, for which it can be shown that giant planets are preferentially found orbiting thick disk stars.None of these two peculiarities is explained by the proposed scenarios of giant planet formation. We contend that they are galactic in nature, and probably not linked to the formation process of giant planets. It is suggested that the same dynamical effect, namely the migration of stars in the galactic disk, is at the origin of both features, with the important consequence that most metal-rich stars hosting giant planets originate from the inner disk. A planet-metallicity correlation similar to the observed one is easily obtained if stars from the inner disk have a higher percentage of giant planets than stars born at the solar radius, with no specific dependence on metallicity. We propose that the density of H2 in the inner galactic disk (the molecular ring) could play a role in setting the high percentage of giant planets that originate from this region.

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Slysh, V. I. "Stars, planets, and cosmic masers." Uspekhi Fizicheskih Nauk 167, no. 10 (1997): 1131. http://dx.doi.org/10.3367/ufnr.0167.199710o.1131.

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Kley, Wilhelm. "Planet Formation in Binary Systems." Symposium - International Astronomical Union 200 (2001): 511–18. http://dx.doi.org/10.1017/s007418090022562x.

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Among the 50 discovered extrasolar planets orbiting main-sequence solar type stars only three are confirmed to be in a binary star system. However, the majority of stars seem to form in binary or even multiple stellar systems. Standard planet formation scenarios consider the creation of planets or planetary systems only for isolated solitary stars. The presence of a companion creates tidal torques on the protoplanetary disk, which may influence the formation process of planets in disks. In this contribution the consequences of the companion's perturbation on the formation scenario of planets is briefly discussed.

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Sicardy, Bruno. "Small Bodies Around Other Stars." Symposium - International Astronomical Union 160 (1994): 429–42. http://dx.doi.org/10.1017/s0074180900046696.

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We briefly review recent advances in the observation and study of planetary bodies in extra-solar systems. We summarize in particular the main physical properties of the β-Pictoris dust disk, and the status of new disk observations. Theoretical implications of infalling discrete bodies are considered, in particular, the existence of possible perturbing planet(s) causing this influx. Such planets could spectacularly disturb circumstellar dust disks, thus revealing themselves in spite of their intrinsic faintness as mere point sources. Finally, we describe the recent possible discovery of at least two planets around a pulsar. This underlines the potential existence of planets in rather exotic circumstances.

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Marcy, Geoffrey W., Debra A. Fischer, R. Paul Butler, and Steven S. Vogt. "Planetary Messages in the Doppler Residuals." Symposium - International Astronomical Union 202 (2004): 20–28. http://dx.doi.org/10.1017/s0074180900217415.

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The Doppler residuals to the Keplerian fits for extrasolar planets reveal important properties of the planets and host stars. Stellar magnetic fields modify the photospheric velocity fields, causing Doppler fluctuations with unknown time scales. This Doppler “jitter”, seen prominently in the magnetic stars Epsilon Eridani and ξ Boo A, compromises the detectability of planets. The Doppler residuals during the transit of HD209458 reveal that the planet orbits in the same direction as the star spins. Moreover, the transit path across the star is nearly parallel to the stellar equator. Most interestingly, the Doppler residuals of known planets often reveal additional coherent variations, probably caused by additional companions. Both 55 Cancri and HD168443 reveal such coherent Doppler residuals. Another five planet–bearing stars observed at Lick show trends in the Doppler residuals indicating the presence of additional companions. Remarkably, about half of the known extrasolar planets reveal such coherent variations. This suggests that stars with planets have a high occurrence rate of harboring more distant companions, planetary or otherwise.

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Dawson, Rebekah I., Ruth A. Murray-Clay, and John Asher Johnson. "Constraining Planetary Migration Mechanisms in Systems of Giant Planets." Proceedings of the International Astronomical Union 8, S299 (June 2013): 386–90. http://dx.doi.org/10.1017/s1743921313009046.

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AbstractIt was once widely believed that planets formed peacefully in situ in their proto-planetary disks and subsequently remain in place. Instead, growing evidence suggests that many giant planets undergo dynamical rearrangement that results in planets migrating inward in the disk, far from their birthplaces. However, it remains debated whether this migration is caused by smooth planet-disk interactions or violent multi-body interactions. Both classes of model can produce Jupiter-mass planets orbiting within 0.1 AU of their host stars, also known as hot Jupiters. In the latter class of model, another planet or star in the system perturbs the Jupiter onto a highly eccentric orbit, which tidal dissipation subsequently shrinks and circularizes during close passages to the star. We assess the prevalence of smooth vs. violent migration through two studies. First, motivated by the predictions of Socrates et al. (2012), we search for super-eccentric hot Jupiter progenitors by using the “photoeccentric effect” to measure the eccentricities of Kepler giant planet candidates from their transit light curves. We find a significant lack of super- eccentric proto-hot Jupiters compared to the number expected, allowing us to place an upper limit on the fraction of hot Jupiters created by stellar binaries. Second, if both planet-disk and multi-body interactions commonly cause giant planet migration, physical properties of the proto-planetary environment may determine which is triggered. We identify three trends in which giant planets orbiting metal rich stars show signatures of planet-planet interactions: (1) gas giants orbiting within 1 AU of metal-rich stars have a range of eccentricities, whereas those orbiting metal- poor stars are restricted to lower eccentricities; (2) metal-rich stars host most eccentric proto-hot Jupiters undergoing tidal circularization; and (3) the pile-up of short-period giant planets, missing in the Kepler sample, is a feature of metal-rich stars and is largely recovered for giants orbiting metal-rich Kepler host stars. These two studies suggest that both disk migration and planet-planet interactions may be widespread, with the latter occurring primarily in metal-rich planetary systems where multiple giant planets can form. Funded by NSF-GRFP DGE-1144152.

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Kubyshkina, Daria, and Aline A. Vidotto. "How does the mass and activity history of the host star affect the population of low-mass planets?" Monthly Notices of the Royal Astronomical Society 504, no. 2 (March 27, 2021): 2034–50. http://dx.doi.org/10.1093/mnras/stab897.

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ABSTRACT The evolution of the atmospheres of low- and intermediate-mass planets is strongly connected to the physical properties of their host stars. The types and the past activities of planet-hosting stars can, therefore, affect the overall planetary population. In this paper, we perform a comparative study of sub-Neptune-like planets orbiting stars of different masses and different evolutionary histories. We discuss the general patterns of the evolved population as a function of parameters and environments of planets. As a model of the atmospheric evolution, we employ the own framework combining planetary evolution in Modules for Experiments in Stellar Astrophysics (mesa) with the realistic prescription of the escape of hydrogen-dominated atmospheres. We find that the final populations look qualitatively similar in terms of the atmospheres survival around different stars, but qualitatively different, with this difference accentuated for planets orbiting more massive stars. We show that a planet has larger chances of keeping its primordial atmosphere in the habitable zone of a solar-mass star compared to M or K dwarfs and if it starts the evolution having a relatively compact envelope. We also address the problem of the uncertain initial temperatures (luminosities) of planets and show that this issue is only of particular importance for planets exposed to extreme atmospheric mass losses.

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Lozovsky, M., R. Helled, I. Pascucci, C. Dorn, J. Venturini, and R. Feldmann. "Why do more massive stars host larger planets?" Astronomy & Astrophysics 652 (August 2021): A110. http://dx.doi.org/10.1051/0004-6361/202140563.

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Aims. It has been suggested that planetary radii increase with stellar mass for planet sizes smaller than 6 R⊕ and host masses lower than 1 M⊙. In this study, we explore whether this inferred relation of planetary size and host star mass can be explained by a higher planetary mass of planets orbiting higher-mass stars, inflation of the planetary radius due to the difference in stellar irradiation, or different planetary compositions and structures. Methods. Using exoplanetary data of planets with measured masses and radii, we investigated the relations between stellar mass and various planetary properties for G and K stars. We confirm that more massive stars host larger and more massive planets. Results. We find that the differences in the planetary masses and temperatures are insufficient to explain the measured differences in radii for planets surrounding different stellar types. We show that the larger planetary radii can be explained by a larger fraction of volatile material (H-He atmospheres) in planets surrounding more massive stars. Conclusions. We conclude that planets around more massive stars are most probably larger as a result of larger H-He atmospheres. Our findings imply that planets forming around more massive stars tend to accrete H-He atmospheres more efficiently.

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Fischer, Debra, Jeff A. Valenti, and Geoff Marcy. "Spectral Analysis of Stars on Planet-Search Surveys." Symposium - International Astronomical Union 219 (2004): 29–40. http://dx.doi.org/10.1017/s0074180900181938.

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We present spectroscopic analysis of ∼1000 stars on the Lick, Keck and AAT planet search projects. This analysis provides a quantitative, and unbiased correlation between metallicity and the rate of occurrence of detected gas giant planets with orbital periods shorter than three years. As stellar metallicity increases, the occurrence of planets increases. Stars with [Fe/H] that is one third of solar only have gas giants detected ∼ 3% of the time. Stars with solar metallicity have a planet occurrence rate of 5 − 10%. The occurrence of gas giant planets rises to 20% in stars with a metallicity that is three times solar.At issue is whether the quantitative dependence of planet occurrence on metallicity is primarily an initial condition, or a by-product of accretion of gas-depleted material onto the convective zone of the star. Accretion could be distinguished as the underlying mechanism for enhanced metallicity if: 1) planet-bearing F-type stars with thinner convective envelopes show a higher mean metallicity than planet-bearing G- or K-type stars, or 2) planet-bearing sub-giants with diluted convective zones showed statistically lower metallicity than their main sequence counterparts.

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Fujii, M. S., and Y. Hori. "Survival rates of planets in open clusters: the Pleiades, Hyades, and Praesepe clusters." Astronomy & Astrophysics 624 (April 2019): A110. http://dx.doi.org/10.1051/0004-6361/201834677.

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Context. In clustered environments, stellar encounters can liberate planets from their host stars via close encounters. Although the detection probability of planets suggests that the planet population in open clusters resembles that in the field, only a few dozen planet-hosting stars have been discovered in open clusters. Aims. We explore the survival rates of planets against stellar encounters in open clusters similar to the Pleiades, Hyades, and Praesepe and embedded clusters. Methods. We performed a series of N-body simulations of high-density and low-density open clusters, open clusters that grow via mergers of subclusters, and embedded clusters. We semi-analytically calculated the survival rate of planets in star clusters up to ~1 Gyr using relative velocities, masses, and impact parameters of intruding stars. Results. Less than 1.5% of close-in planets within 1 AU and at most 7% of planets with 1–10 AU are ejected by stellar encounters in clustered environments after the dynamical evolution of star clusters. If a planet population from 0.01–100 AU in an open cluster initially follows the probability distribution function of exoplanets with semi-major axis (ap) between 0.03 and 3 AU in the field discovered by RV surveys (∝ ap−0.6), the PDF of surviving planets beyond ~10 AU in open clusters can be slightly modified to ∝ ap−0.76. The production rate of free-floating planets (FFPs) per star is 0.0096–0.18, where we have assumed that all the stars initially have one giant planet with a mass of 1–13 MJup in a circular orbit. The expected frequency of FFPs is compatible with the upper limit on that of FFPs indicated by recent microlensing surveys. Our survival rates of planets in open clusters suggest that planets within 10 AU around FGKM-type stars are rich in relatively-young (≲10–100 Myr for open clusters and ~1–10 Myr for embedded clusters), less massive open clusters, which are promising targets for planet searches.

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Sato, Bun'ei. "Radial-Velocity Searches for Exoplanets in East Asia." Proceedings of the International Astronomical Union 8, S293 (August 2012): 1–9. http://dx.doi.org/10.1017/s1743921313012441.

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AbstractHundreds of extrasolar planets have been discovered around various types of stars by various techniques during the past decade. Among them precise radial velocity measurements for stars are fundamental technique to detect and confirm exoplanets. In this paper activities in East-Asian region in this research field are introduced: East-Asian Planet Search Network, which is a network searching for planets around evolved intermediate-mass stars, and Subaru/IRD project, which will search for habitable planets around M-type dwarfs using infrared radial-velocity method.

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Dong, Subo, Ji-Wei Xie, Ji-Lin Zhou, Zheng Zheng, and Ali Luo. "LAMOST telescope reveals that Neptunian cousins of hot Jupiters are mostly single offspring of stars that are rich in heavy elements." Proceedings of the National Academy of Sciences 115, no. 2 (December 28, 2017): 266–71. http://dx.doi.org/10.1073/pnas.1711406115.

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We discover a population of short-period, Neptune-size planets sharing key similarities with hot Jupiters: both populations are preferentially hosted by metal-rich stars, and both are preferentially found in Kepler systems with single-transiting planets. We use accurate Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Data Release 4 (DR4) stellar parameters for main-sequence stars to study the distributions of short-period (1d<P<10d)Kepler planets as a function of host star metallicity. The radius distribution of planets around metal-rich stars is more “puffed up” compared with that around metal-poor hosts. In two period–radius regimes, planets preferentially reside around metal-rich stars, while there are hardly any planets around metal-poor stars. One is the well-known hot Jupiters, and the other one is a population of Neptune-size planets (2R⊕≲Rp≲6R⊕), dubbed “Hoptunes.” Also like hot Jupiters, Hoptunes occur more frequently in systems with single-transiting planets although the fraction of Hoptunes occurring in multiples is larger than that of hot Jupiters. About 1% of solar-type stars host Hoptunes, and the frequencies of Hoptunes and hot Jupiters increase with consistent trends as a function of [Fe/H]. In the planet radius distribution, hot Jupiters and Hoptunes are separated by a “valley” at approximately Saturn size (in the range of 6R⊕≲Rp≲10R⊕), and this “hot-Saturn valley” represents approximately an order-of-magnitude decrease in planet frequency compared with hot Jupiters and Hoptunes. The empirical “kinship” between Hoptunes and hot Jupiters suggests likely common processes (migration and/or formation) responsible for their existence.

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Barbato, D., A. Sozzetti, K. Biazzo, L. Malavolta, N. C. Santos, M. Damasso, A. F. Lanza, et al. "The GAPS Programme with HARPS-N at TNG." Astronomy & Astrophysics 621 (January 2019): A110. http://dx.doi.org/10.1051/0004-6361/201834305.

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Context. Statistical studies of exoplanets have shown that giant planets are more commonly hosted by metal-rich dwarf stars than low-metallicity stars, while no such correlation is evident for lower mass planets. The search for giant planets around metal-poor stars and the estimate of their occurrence fp is an important element in providing support to models of planet formation. Aims. We present results from the HARPS-N search for giant planets orbiting metal-poor (− 1.0 ≤[Fe/H] ≤−0.5 dex) stars in the northern hemisphere, complementing a previous HARPS survey on southern stars in order to update the estimate of fp. Methods. High-precision HARPS-N observations of 42 metal-poor stars were used to search for planetary signals to be fitted using differential evolution Markov chain Monte Carlo single-Keplerian models. We then joined our detections to the results of the previous HARPS survey on 88 metal-poor stars to provide a preliminary estimate of the two-hemisphere fp. Results. We report the detection of two new giant planets around HD 220197 and HD 233832. The first companion has Msin i = 0.20−0.04+0.07 MJup and an orbital period of 1728−80+162 days, and for the second companion, we find two solutions of equal statistical weight with periods of 2058−40+47 and 4047−117+91 days and minimum masses of 1.78−0.06+0.08 and 2.72−0.23+0.23 MJup, respectively. Joining our two detections with the three from the southern survey, we obtain a preliminary and conservative estimate of the global frequency of fp = 3.84 −1.06+2.45% for giant planets around metal-poor stars.Conclusions. The two new giant planets orbit dwarf stars at the metal-rich end of the HARPS-N metal-poor sample. This corroborates previous results that suggested that giant planet frequency is still a rising function of the host star [Fe/H]. We also note that all detections in the overall sample are giant long-period planets.

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Jin, Sheng. "Relative occurrence rates of terrestrial planets orbiting FGK stars." Monthly Notices of the Royal Astronomical Society 502, no. 4 (February 15, 2021): 5302–12. http://dx.doi.org/10.1093/mnras/stab436.

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ABSTRACT This paper aims to derive a map of relative planet occurrence rates that can provide constraints on the overall distribution of terrestrial planets around FGK stars. Based on the planet candidates in the Kepler DR25 data release, I first generate a continuous density map of planet distribution using a Gaussian kernel model and correct the geometric factor that the discovery space of a transit event decreases along with the increase of planetary orbital distance. Then, I fit two exponential decay functions of detection efficiency along with the increase of planetary orbital distance and the decrease of planetary radius. Finally, the density map of planet distribution is compensated for the fitted exponential decay functions of detection efficiency to obtain a relative occurrence rate distribution of terrestrial planets. The result shows two regions with planet abundance: one corresponds to planets with radii between 0.5 and 1.5 R⊕ within 0.2 au, and the other corresponds to planets with radii between 1.5 and 3 R⊕ beyond 0.5 au. It also confirms the features that may be caused by atmospheric evaporation: there is a vacancy of planets of sizes between 2.0 and 4.0 R⊕ inside of ∼0.5 au, and a valley with relatively low occurrence rates between 0.2 and 0.5 au for planets with radii between 1.5 and 3.0 R⊕.

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Nielsen, Eric L., Michael C. Liu, Zahed Wahhaj, Beth A. Biller, Thomas L. Hayward, Laird M. Close, Bruce Macintosh, et al. "Mapping the Distributions of Exoplanet Populations with NICI and GPI." Proceedings of the International Astronomical Union 10, S314 (November 2015): 220–25. http://dx.doi.org/10.1017/s1743921315006572.

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AbstractWhile more and more long-period giant planets are discovered by direct imaging, the distribution of planets at these separations (≳5 AU) has remained largely uncertain, especially compared to planets in the inner regions of solar systems probed by RV and transit techniques. The low frequency, the detection challenges, and heterogeneous samples make determining the mass and orbit distributions of directly imaged planets at the end of a survey difficult. By utilizing Monte Carlo methods that incorporate the age, distance, and spectral type of each target, we can use all stars in the survey, not just those with detected planets, to learn about the underlying population. We have produced upper limits and direct measurements of the frequency of these planets with the most recent generation of direct imaging surveys. The Gemini NICI Planet-Finding Campaign observed 220 young, nearby stars at a median H-band contrast of 14.5 magnitudes at 1”, representing the largest, deepest search for exoplanets by the completion of the survey. The Gemini Planet Imager Exoplanet Survey is in the process of surveying 600 stars, pushing these contrasts to a few tenths of an arcsecond from the star. With the advent of large surveys (many hundreds of stars) using advanced planet-imagers we gain the ability to move beyond measuring the frequency of wide-separation giant planets and to simultaneously determine the distribution as a function of planet mass, semi-major axis, and stellar mass, and so directly test models of planet formation and evolution.

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Marcy, Geoffrey W., and Andrew W. Howard. "The occurrence and the distribution of masses and radii of exoplanets." Proceedings of the International Astronomical Union 6, S276 (October 2010): 3–12. http://dx.doi.org/10.1017/s1743921311019867.

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AbstractWe analyze the statistics of Doppler-detected planets and Keplere-detected planet candidates of high integrity. We determine the number of planets per star as a function of planet mass, radius, and orbital period, and the occurrence of planets as a function of stellar mass. We consider only orbital periods less than 50 days around Solar-type (GK) stars, for which both Doppler and Kepler offer good completeness. We account for observational detection effects to determine the actual number of planets per star. From Doppler-detected planets discovered in a survey of 166 nearby G and K main sequence stars we find a planet occurrence of 15+5−4% for planets with M sin i = 3–30 ME and P < 50 d, as described in Howard et al. (2010). From Keplere, the planet occurrence is 0.130 ± 0.008, 0.023 ± 0.003, and 0.013 ± 0.002 planets per star for planets with radii 2–4, 4–8, and 8–32 RE, consistent with Doppler-detected planets. From Keplere, the number of planets per star as a function of planet radius is given by a power law, df/dlog R = kRRα with kR = 2.9+0.5−0.4, α = −1.92 ± 0.11, and R = RP/RE. Neither the Doppler-detected planets nor the Keplere-detected planets exhibit a “desert” at super-Earth and Neptune sizes for close-in orbits, as suggested by some planet population synthesis models. The distribution of planets with orbital period, P, shows a gentle increase in occurrence with orbital period in the range 2–50 d. The occurrence of small, 2–4 RE planets increases with decreasing stellar mass, with seven times more planets around low mass dwarfs (3600–4100 K) than around massive stars (6600–7100 K).

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Slysh, V. I. "Stars, planets, and cosmic masers." Physics-Uspekhi 40, no. 10 (October 31, 1997): 1079. http://dx.doi.org/10.1070/pu1997v040n10abeh001580.

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Gonzalez, G. "Are stars with planets anomalous?" Monthly Notices of the Royal Astronomical Society 308, no. 2 (September 19, 1999): 447–58. http://dx.doi.org/10.1046/j.1365-8711.1999.02717.x.

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Haghighipour, Nader. "Binary Stars with Habitable Planets." American Scientist 96, no. 4 (2008): 294. http://dx.doi.org/10.1511/2008.73.3843.

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Gonzalez, Guillermo. "Colloquium: Stars, planets, and metals." Reviews of Modern Physics 75, no. 1 (January 22, 2003): 101–20. http://dx.doi.org/10.1103/revmodphys.75.101.

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Johnson, John A. "Warm planets orbiting cool stars." Physics Today 67, no. 3 (March 2014): 31–36. http://dx.doi.org/10.1063/pt.3.2309.

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40

Liebert, James, and William B. Hubbard. "Big planets and little stars." Nature 400, no. 6742 (July 1999): 316–17. http://dx.doi.org/10.1038/22430.

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Cowen, R. "Finding Planets around Ordinary Stars." Science News 148, no. 17 (October 21, 1995): 260. http://dx.doi.org/10.2307/4018175.

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Zuckerman;, B. "Young Stars and Giant Planets." Science 277, no. 5331 (September 5, 1997): 1421a—1423. http://dx.doi.org/10.1126/science.277.5331.1421a.

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Vidotto, A. "Protecting planets from their stars." Astronomy & Geophysics 54, no. 1 (January 15, 2013): 1.25–1.30. http://dx.doi.org/10.1093/astrogeo/ats038.

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Neville, Sarah. "Exploring the planets and stars." Child Care 11, no. 10 (October 2, 2014): 10–11. http://dx.doi.org/10.12968/chca.2014.11.10.10.

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Angel, Roger, and Adam Burrows. "Seeking planets around nearby stars." Nature 374, no. 6524 (April 1995): 678–79. http://dx.doi.org/10.1038/374678a0.

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Balona, L. A. "Possible planets around A stars." Monthly Notices of the Royal Astronomical Society 441, no. 4 (May 31, 2014): 3543–49. http://dx.doi.org/10.1093/mnras/stu822.

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Murray, N., and B. Chaboyer. "Are Stars with Planets Polluted?" Astrophysical Journal 566, no. 1 (February 10, 2002): 442–51. http://dx.doi.org/10.1086/338079.

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Wolszczan, A. "Toward planets around neutron stars." Astrophysics and Space Science 212, no. 1-2 (February 1994): 67–75. http://dx.doi.org/10.1007/bf00984511.

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Wuchterl, Günther, and Eike Guenther. "Formation of Stars and Planets." Astronomische Nachrichten 325, S1 (August 2004): 1–8. http://dx.doi.org/10.1002/asna.200485061.

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Kley, Wilhelm. "Planet formation in binary stars." Proceedings of the International Astronomical Union 3, S249 (October 2007): 251–60. http://dx.doi.org/10.1017/s1743921308016657.

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AbstractAs of today more than 30 planetary systems have been discovered in binary stars. In all cases the configuration is circumstellar, where the planets orbit around one of the stars. The formation process of planets in binary stars is more difficult than around single stars due to the gravitational action of the companion. An overview of the research done in this field will be given. The dynamical influence that a secondary companion has on a circumstellar disk, and how this affects the planet formation process in this challenging environment will be summarized. Finally, new fully hydrodynamical simulations of protoplanets embedded in disks residing in a binary star will be presented. Applications with respect to the planet orbiting the primary in the system γ Cephei will be presented.

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Journal articles on the topic 'Stars with planets'

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