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  • 1
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    A test of the asteroseismic {nu}max scaling relation for solar-like oscillations in main-sequence and subgiant stars (2015)
    Oxford University Press
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    Publication Date: 2015-06-20
    Description: Large-scale analyses of stellar samples comprised of cool, solar-like oscillators now commonly utilize the so-called asteroseismic scaling relations to estimate fundamental stellar properties. In this paper, we present a test of the scaling relation for the global asteroseismic parameter max , the frequency at which a solar-like oscillator presents its strongest observed pulsation amplitude. The classic relation assumes that this characteristic frequency scales with a particular combination of surface gravity and effective temperature that also describes the dependence of the cut-off frequency for acoustic waves in an isothermal atmosphere, i.e. $\nu _{\rm max} \propto gT_{\rm eff}^{-1/2}$ . We test how well the oscillations of cool main-sequence and subgiant stars adhere to this relation, using a sample of asteroseismic targets observed by the NASA Kepler Mission. Our results, which come from a grid-based analysis, rule out departures from the classic $gT_{\rm eff}^{-1/2}$ scaling dependence at the level of ~=1.5 per cent over the full ~= 1560 K range in T eff that we tested. There is some uncertainty over the absolute calibration of the scaling. However, any variation with T eff is evidently small, with limits similar to those above.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 2
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    Asteroseismology of the Hyades with K2: first detection of main-sequence solar-like oscillations in an open cluster (2016)
    Oxford University Press
    Details
    Publication Date: 2016-10-08
    Description: The Hyades open cluster was targeted during Campaign 4 (C4) of the NASA K2 mission, and short-cadence data were collected on a number of cool main-sequence stars. Here, we report results on two F-type stars that show detectable oscillations of a quality that allows asteroseismic analyses to be performed. These are the first ever detections of solar-like oscillations in main-sequence stars in an open cluster.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 3
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    Electronic structure and defect properties of B6O from hybrid functional and many-body perturbation theory calculations: A possible ambipolar transparent conductor (2014)
    American Physical Society (APS)
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    Publication Date: 2014-07-17
    Description: Author(s): J. B. Varley, V. Lordi, A. Miglio, and G. Hautier B6O is a member of icosahedral boron-rich solids known for their physical hardness and stability under irradiation bombardment, but it has also recently emerged as a promising high mobility p-type transparent conducting oxide. Using a combination of hybrid functional and many-body perturbation theor... [Phys. Rev. B 90, 045205] Published Wed Jul 16, 2014
    Keywords: Semiconductors I: bulk
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
    Published by American Physical Society (APS)
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  • 4
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    Deviations from a uniform period spacing of gravity modes in a massive star (2010)
    Nature Publishing Group (NPG)
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    Publication Date: 2010-03-12
    Description: The life of a star is dominantly determined by the physical processes in the stellar interior. Unfortunately, we still have a poor understanding of how the stellar gas mixes near the stellar core, preventing precise predictions of stellar evolution. The unknown nature of the mixing processes as well as the extent of the central mixed region is particularly problematic for massive stars. Oscillations in stars with masses a few times that of the Sun offer a unique opportunity to disentangle the nature of various mixing processes, through the distinct signature they leave on period spacings in the gravity mode spectrum. Here we report the detection of numerous gravity modes in a young star with a mass of about seven solar masses. The mean period spacing allows us to estimate the extent of the convective core, and the clear periodic deviation from the mean constrains the location of the chemical transition zone to be at about 10 per cent of the radius and rules out a clear-cut profile.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Degroote, Pieter -- Aerts, Conny -- Baglin, Annie -- Miglio, Andrea -- Briquet, Maryline -- Noels, Arlette -- Niemczura, Ewa -- Montalban, Josefina -- Bloemen, Steven -- Oreiro, Raquel -- Vuckovic, Maja -- Smolders, Kristof -- Auvergne, Michel -- Baudin, Frederic -- Catala, Claude -- Michel, Eric -- England -- Nature. 2010 Mar 11;464(7286):259-61. doi: 10.1038/nature08864.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven, Belgium. pieter.degroote@ster.kuleuven.ac.be〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20220844" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 5
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    Stellar spin-orbit misalignment in a multiplanet system (2013)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2013-10-19
    Description: Stars hosting hot Jupiters are often observed to have high obliquities, whereas stars with multiple coplanar planets have been seen to have low obliquities. This has been interpreted as evidence that hot-Jupiter formation is linked to dynamical disruption, as opposed to planet migration through a protoplanetary disk. We used asteroseismology to measure a large obliquity for Kepler-56, a red giant star hosting two transiting coplanar planets. These observations show that spin-orbit misalignments are not confined to hot-Jupiter systems. Misalignments in a broader class of systems had been predicted as a consequence of torques from wide-orbiting companions, and indeed radial velocity measurements revealed a third companion in a wide orbit in the Kepler-56 system.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Huber, Daniel -- Carter, Joshua A -- Barbieri, Mauro -- Miglio, Andrea -- Deck, Katherine M -- Fabrycky, Daniel C -- Montet, Benjamin T -- Buchhave, Lars A -- Chaplin, William J -- Hekker, Saskia -- Montalban, Josefina -- Sanchis-Ojeda, Roberto -- Basu, Sarbani -- Bedding, Timothy R -- Campante, Tiago L -- Christensen-Dalsgaard, Jorgen -- Elsworth, Yvonne P -- Stello, Dennis -- Arentoft, Torben -- Ford, Eric B -- Gilliland, Ronald L -- Handberg, Rasmus -- Howard, Andrew W -- Isaacson, Howard -- Johnson, John Asher -- Karoff, Christoffer -- Kawaler, Steven D -- Kjeldsen, Hans -- Latham, David W -- Lund, Mikkel N -- Lundkvist, Mia -- Marcy, Geoffrey W -- Metcalfe, Travis S -- Silva Aguirre, Victor -- Winn, Joshua N -- New York, N.Y. -- Science. 2013 Oct 18;342(6156):331-4. doi: 10.1126/science.1242066.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉NASA Ames Research Center, MS 244-30, Moffett Field, CA 94035, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24136961" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 6
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    Hot super-Earths stripped by their host stars (2016)
    Springer Nature
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    Publication Date: 2016-04-13
    Description: Article Theory predicts a deficit of super-Earth sized planets, which orbit close to their host star. Here, Lundkvist et al . use data from the NASA Kepler mission to show that this deficit is also seen in observations, thereby providing new insight into exoplanetary systems. Nature Communications doi: 10.1038/ncomms11201 Authors: M. S. Lundkvist, H. Kjeldsen, S. Albrecht, G. R. Davies, S. Basu, D. Huber, A. B. Justesen, C. Karoff, V. Silva Aguirre, V. Van Eylen, C. Vang, T. Arentoft, T. Barclay, T. R. Bedding, T. L. Campante, W. J. Chaplin, J. Christensen-Dalsgaard, Y. P. Elsworth, R. L. Gilliland, R. Handberg, S. Hekker, S. D. Kawaler, M. N. Lund, T. S. Metcalfe, A. Miglio, J. F. Rowe, D. Stello, B. Tingley, T. R. White
    Electronic ISSN: 2041-1723
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 7
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    A sub-Mercury-sized exoplanet (2013)
    Nature Publishing Group (NPG)
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    Publication Date: 2013-02-22
    Description: Since the discovery of the first exoplanets, it has been known that other planetary systems can look quite unlike our own. Until fairly recently, we have been able to probe only the upper range of the planet size distribution, and, since last year, to detect planets that are the size of Earth or somewhat smaller. Hitherto, no planets have been found that are smaller than those we see in the Solar System. Here we report a planet significantly smaller than Mercury. This tiny planet is the innermost of three that orbit the Sun-like host star, which we have designated Kepler-37. Owing to its extremely small size, similar to that of the Moon, and highly irradiated surface, the planet, Kepler-37b, is probably rocky with no atmosphere or water, similar to Mercury.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Barclay, Thomas -- Rowe, Jason F -- Lissauer, Jack J -- Huber, Daniel -- Fressin, Francois -- Howell, Steve B -- Bryson, Stephen T -- Chaplin, William J -- Desert, Jean-Michel -- Lopez, Eric D -- Marcy, Geoffrey W -- Mullally, Fergal -- Ragozzine, Darin -- Torres, Guillermo -- Adams, Elisabeth R -- Agol, Eric -- Barrado, David -- Basu, Sarbani -- Bedding, Timothy R -- Buchhave, Lars A -- Charbonneau, David -- Christiansen, Jessie L -- Christensen-Dalsgaard, Jorgen -- Ciardi, David -- Cochran, William D -- Dupree, Andrea K -- Elsworth, Yvonne -- Everett, Mark -- Fischer, Debra A -- Ford, Eric B -- Fortney, Jonathan J -- Geary, John C -- Haas, Michael R -- Handberg, Rasmus -- Hekker, Saskia -- Henze, Christopher E -- Horch, Elliott -- Howard, Andrew W -- Hunter, Roger C -- Isaacson, Howard -- Jenkins, Jon M -- Karoff, Christoffer -- Kawaler, Steven D -- Kjeldsen, Hans -- Klaus, Todd C -- Latham, David W -- Li, Jie -- Lillo-Box, Jorge -- Lund, Mikkel N -- Lundkvist, Mia -- Metcalfe, Travis S -- Miglio, Andrea -- Morris, Robert L -- Quintana, Elisa V -- Stello, Dennis -- Smith, Jeffrey C -- Still, Martin -- Thompson, Susan E -- England -- Nature. 2013 Feb 28;494(7438):452-4. doi: 10.1038/nature11914. Epub 2013 Feb 20.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉NASA Ames Research Center, Moffett Field, California 94035, USA. thomas.barclay@nasa.gov〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23426260" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 8
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    Gravity modes as a way to distinguish between hydrogen- and helium-burning red giant stars (2011)
    Nature Publishing Group (NPG)
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    Publication Date: 2011-04-02
    Description: Red giants are evolved stars that have exhausted the supply of hydrogen in their cores and instead burn hydrogen in a surrounding shell. Once a red giant is sufficiently evolved, the helium in the core also undergoes fusion. Outstanding issues in our understanding of red giants include uncertainties in the amount of mass lost at the surface before helium ignition and the amount of internal mixing from rotation and other processes. Progress is hampered by our inability to distinguish between red giants burning helium in the core and those still only burning hydrogen in a shell. Asteroseismology offers a way forward, being a powerful tool for probing the internal structures of stars using their natural oscillation frequencies. Here we report observations of gravity-mode period spacings in red giants that permit a distinction between evolutionary stages to be made. We use high-precision photometry obtained by the Kepler spacecraft over more than a year to measure oscillations in several hundred red giants. We find many stars whose dipole modes show sequences with approximately regular period spacings. These stars fall into two clear groups, allowing us to distinguish unambiguously between hydrogen-shell-burning stars (period spacing mostly approximately 50 seconds) and those that are also burning helium (period spacing approximately 100 to 300 seconds).〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bedding, Timothy R -- Mosser, Benoit -- Huber, Daniel -- Montalban, Josefina -- Beck, Paul -- Christensen-Dalsgaard, Jorgen -- Elsworth, Yvonne P -- Garcia, Rafael A -- Miglio, Andrea -- Stello, Dennis -- White, Timothy R -- De Ridder, Joris -- Hekker, Saskia -- Aerts, Conny -- Barban, Caroline -- Belkacem, Kevin -- Broomhall, Anne-Marie -- Brown, Timothy M -- Buzasi, Derek L -- Carrier, Fabien -- Chaplin, William J -- Di Mauro, Maria Pia -- Dupret, Marc-Antoine -- Frandsen, Soren -- Gilliland, Ronald L -- Goupil, Marie-Jo -- Jenkins, Jon M -- Kallinger, Thomas -- Kawaler, Steven -- Kjeldsen, Hans -- Mathur, Savita -- Noels, Arlette -- Aguirre, Victor Silva -- Ventura, Paolo -- England -- Nature. 2011 Mar 31;471(7340):608-11. doi: 10.1038/nature09935.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Sydney Institute for Astronomy, School of Physics, University of Sydney, New South Wales 2006, Australia. t.bedding@physics.usyd.edu.au〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21455175" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 9
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    Fast core rotation in red-giant stars as revealed by gravity-dominated mixed modes (2011)
    Nature Publishing Group (NPG)
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    Publication Date: 2011-12-14
    Description: When the core hydrogen is exhausted during stellar evolution, the central region of a star contracts and the outer envelope expands and cools, giving rise to a red giant. Convection takes place over much of the star's radius. Conservation of angular momentum requires that the cores of these stars rotate faster than their envelopes; indirect evidence supports this. Information about the angular-momentum distribution is inaccessible to direct observations, but it can be extracted from the effect of rotation on oscillation modes that probe the stellar interior. Here we report an increasing rotation rate from the surface of the star to the stellar core in the interiors of red giants, obtained using the rotational frequency splitting of recently detected 'mixed modes'. By comparison with theoretical stellar models, we conclude that the core must rotate at least ten times faster than the surface. This observational result confirms the theoretical prediction of a steep gradient in the rotation profile towards the deep stellar interior.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Beck, Paul G -- Montalban, Josefina -- Kallinger, Thomas -- De Ridder, Joris -- Aerts, Conny -- Garcia, Rafael A -- Hekker, Saskia -- Dupret, Marc-Antoine -- Mosser, Benoit -- Eggenberger, Patrick -- Stello, Dennis -- Elsworth, Yvonne -- Frandsen, Soren -- Carrier, Fabien -- Hillen, Michel -- Gruberbauer, Michael -- Christensen-Dalsgaard, Jorgen -- Miglio, Andrea -- Valentini, Marica -- Bedding, Timothy R -- Kjeldsen, Hans -- Girouard, Forrest R -- Hall, Jennifer R -- Ibrahim, Khadeejah A -- England -- Nature. 2011 Dec 7;481(7379):55-7. doi: 10.1038/nature10612.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, 3001 Leuven, Belgium. paul.beck@ster.kuleuven.be〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22158105" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 10
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    Multi-periodic pulsations of a stripped red-giant star in an eclipsing binary system (2013)
    Nature Publishing Group (NPG)
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    Publication Date: 2013-06-28
    Description: Low-mass white-dwarf stars are the remnants of disrupted red-giant stars in binary millisecond pulsars and other exotic binary star systems. Some low-mass white dwarfs cool rapidly, whereas others stay bright for millions of years because of stable fusion in thick surface hydrogen layers. This dichotomy is not well understood, so the potential use of low-mass white dwarfs as independent clocks with which to test the spin-down ages of pulsars or as probes of the extreme environments in which low-mass white dwarfs form cannot fully be exploited. Here we report precise mass and radius measurements for the precursor to a low-mass white dwarf. We find that only models in which this disrupted red-giant star has a thick hydrogen envelope can match the strong constraints provided by our data. Very cool low-mass white dwarfs must therefore have lost their thick hydrogen envelopes by irradiation from pulsar companions or by episodes of unstable hydrogen fusion (shell flashes). We also find that this low-mass white-dwarf precursor is a type of pulsating star not hitherto seen. The observed pulsation frequencies are sensitive to internal processes that determine whether this star will undergo shell flashes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Maxted, Pierre F L -- Serenelli, Aldo M -- Miglio, Andrea -- Marsh, Thomas R -- Heber, Ulrich -- Dhillon, Vikram S -- Littlefair, Stuart -- Copperwheat, Chris -- Smalley, Barry -- Breedt, Elme -- Schaffenroth, Veronika -- England -- Nature. 2013 Jun 27;498(7455):463-5. doi: 10.1038/nature12192.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Astrophysics Group, Keele University, Keele, Staffordshire ST5 5BG, UK. p.maxted@keele.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23803845" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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