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  • 1
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    The GALAH survey: scientific motivation (2015)
    Oxford University Press
    Details
    Publication Date: 2015-04-10
    Description: The Galactic Archaeology with HERMES (GALAH) survey is a large high-resolution spectroscopic survey using the newly commissioned High Efficiency and Resolution Multi-Element Spectrograph (HERMES) on the Anglo-Australian Telescope. The HERMES spectrograph provides high-resolution ( R  ~ 28 000) spectra in four passbands for 392 stars simultaneously over a 2 deg field of view. The goal of the survey is to unravel the formation and evolutionary history of the Milky Way, using fossil remnants of ancient star formation events which have been disrupted and are now dispersed throughout the Galaxy. Chemical tagging seeks to identify such dispersed remnants solely from their common and unique chemical signatures; these groups are unidentifiable from their spatial, photometric or kinematic properties. To carry out chemical tagging, the GALAH survey will acquire spectra for a million stars down to V  ~ 14. The HERMES spectra of FGK stars contain absorption lines from 29 elements including light proton-capture elements, α-elements, odd-Z elements, iron-peak elements and n-capture elements from the light and heavy s-process and the r-process. This paper describes the motivation and planned execution of the GALAH survey, and presents some results on the first-light performance of HERMES.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 2
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    Asteroseismic inference on rotation, gyrochronology and planetary system dynamics of 16 Cygni (2014)
    Oxford University Press
    Details
    Publication Date: 2014-12-03
    Description: The solar analogues 16 Cyg A and B are excellent asteroseismic targets in the Kepler field of view and together with a red dwarf and a Jovian planet form an interesting system. For these more evolved Sun-like stars we cannot detect surface rotation with the current Kepler data but instead use the technique of asteroseimology to determine rotational properties of both 16 Cyg A and B. We find the rotation periods to be $23.8^{+1.5}_{-1.8}$ and $23.2^{+11.5}_{-3.2} \rm \, d$ , and the angles of inclination to be $56^{+6}_{-5} \, ^{\circ }$ and $36^{+17}_{-7} \, ^{\circ }$ , for A and B, respectively. Together with these results we use the published mass and age to suggest that, under the assumption of a solar-like rotation profile, 16 Cyg A could be used when calibrating gyrochronology relations. In addition, we discuss the known 16 Cyg B star–planet eccentricity and measured low obliquity which is consistent with Kozai cycling and tidal theory.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 3
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    The GALAH survey: the data reduction pipeline (2016)
    Oxford University Press
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    Publication Date: 2016-10-27
    Description: We present the data reduction procedures being used by the GALactic Archeology with Hermes (GALAH) survey, carried out with the HERMES fibre-fed, multi-object spectrograph on the 3.9-m Anglo-Australian Telescope. GALAH is a unique survey, targeting 1 million stars brighter than magnitude V = 14 at a resolution of 28 000 with a goal to measure the abundances of 29 elements. Such a large number of high-resolution spectra necessitate the development of a reduction pipeline optimized for speed, accuracy, and consistency. We outline the design and structure of the iraf -based reduction pipeline that we developed, specifically for GALAH, to produce fully calibrated spectra aimed for subsequent stellar atmospheric parameter estimation. The pipeline takes advantage of existing iraf routines and other readily available software so as to be simple to maintain, testable, and reliable. A radial velocity and stellar atmospheric parameter estimator code is also presented, which is used for further data analysis and yields a useful verification of the reduction quality. We have used this estimator to quantify the data quality of GALAH for fibre cross-talk level (0.5 per cent) and scattered light (~5 counts in a typical 20 min exposure), resolution across the field, sky spectrum properties, wavelength solution reliability (better than 1 km s –1 accuracy), and radial velocity precision.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 4
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    HD 181068: a red giant in a triply eclipsing compact hierarchical triple system (2011)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2011-04-09
    Description: Hierarchical triple systems comprise a close binary and a more distant component. They are important for testing theories of star formation and of stellar evolution in the presence of nearby companions. We obtained 218 days of Kepler photometry of HD 181068 (magnitude of 7.1), supplemented by ground-based spectroscopy and interferometry, which show it to be a hierarchical triple with two types of mutual eclipses. The primary is a red giant that is in a 45-day orbit with a pair of red dwarfs in a close 0.9-day orbit. The red giant shows evidence for tidally induced oscillations that are driven by the orbital motion of the close pair. HD 181068 is an ideal target for studies of dynamical evolution and testing tidal friction theories in hierarchical triple systems.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Derekas, A -- Kiss, L L -- Borkovits, T -- Huber, D -- Lehmann, H -- Southworth, J -- Bedding, T R -- Balam, D -- Hartmann, M -- Hrudkova, M -- Ireland, M J -- Kovacs, J -- Mezo, Gy -- Moor, A -- Niemczura, E -- Sarty, G E -- Szabo, Gy M -- Szabo, R -- Telting, J H -- Tkachenko, A -- Uytterhoeven, K -- Benko, J M -- Bryson, S T -- Maestro, V -- Simon, A E -- Stello, D -- Schaefer, G -- Aerts, C -- ten Brummelaar, T A -- De Cat, P -- McAlister, H A -- Maceroni, C -- Merand, A -- Still, M -- Sturmann, J -- Sturmann, L -- Turner, N -- Tuthill, P G -- Christensen-Dalsgaard, J -- Gilliland, R L -- Kjeldsen, H -- Quintana, E V -- Tenenbaum, P -- Twicken, J D -- New York, N.Y. -- Science. 2011 Apr 8;332(6026):216-8. doi: 10.1126/science.1201762.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Astronomy, Eotvos University, Budapest, Hungary. derekas@konkoly.hu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21474755" 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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  • 5
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    Stellar spin-orbit misalignment in a multiplanet system (2013)
    American Association for the Advancement of Science (AAAS)
    Details
    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
    Details
    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)
    Details
    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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    The excitation of solar-like oscillations in a deltaSct star by efficient envelope convection (2011)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2011-09-16
    Description: Delta Scuti (deltaSct) stars are opacity-driven pulsators with masses of 1.5-2.5 Mmiddle dot in circle, their pulsations resulting from the varying ionization of helium. In less massive stars such as the Sun, convection transports mass and energy through the outer 30 per cent of the star and excites a rich spectrum of resonant acoustic modes. Based on the solar example, with no firm theoretical basis, models predict that the convective envelope in deltaSct stars extends only about 1 per cent of the radius, but with sufficient energy to excite solar-like oscillations. This was not observed before the Kepler mission, so the presence of a convective envelope in the models has been questioned. Here we report the detection of solar-like oscillations in the deltaSct star HD187547, implying that surface convection operates efficiently in stars about twice as massive as the Sun, as the ad hoc models predicted.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Antoci, V -- Handler, G -- Campante, T L -- Thygesen, A O -- Moya, A -- Kallinger, T -- Stello, D -- Grigahcene, A -- Kjeldsen, H -- Bedding, T R -- Luftinger, T -- Christensen-Dalsgaard, J -- Catanzaro, G -- Frasca, A -- De Cat, P -- Uytterhoeven, K -- Bruntt, H -- Houdek, G -- Kurtz, D W -- Lenz, P -- Kaiser, A -- Van Cleve, J -- Allen, C -- Clarke, B D -- England -- Nature. 2011 Sep 29;477(7366):570-3. doi: 10.1038/nature10389.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Astronomy, University of Vienna, Turkenschanzstrasse 18, A-1180 Vienna, Austria. victoria.antoci@univie.ac.at〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21918514" 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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    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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  • 10
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    Fast core rotation in red-giant stars as revealed by gravity-dominated mixed modes (2011)
    Nature Publishing Group (NPG)
    Details
    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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