3,119 results on '"Giant star"'
Search Results
2. Preliminary Evaluation of the Kepler Input Catalog Extinction Model Using Stellar Temperatures
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Zasowski, Gail, An, Deokkeun, Pinsonneault, Marc, Miglio, Andrea, editor, Eggenberger, Patrick, editor, Girardi, Léo, editor, and Montalbán, Josefina, editor
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- 2015
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3. The Effects of Close-in Exoplanets on Their Host Stars
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Guenther, Eike W., Geier, Stephan, Burton, W.B., Series editor, Lammer, Helmut, editor, and Khodachenko, Maxim, editor
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- 2015
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4. Asteroseismology of Eclipsing Binary Stars
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Huber, Daniel, Burton, W.B., Series editor, Ake, Thomas B., editor, and Griffin, Elizabeth, editor
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- 2015
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5. The Hertzsprung-Russell Diagram
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Inglis, Michael, Watson, John, Series editor, and Inglis, Michael
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- 2015
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6. The Hertzsprung-Russell Diagram
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Michael Inglis
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Physics ,symbols.namesake ,Hertzsprung–Russell diagram ,law ,Object diagram ,symbols ,Mathematics::Metric Geometry ,A* search algorithm ,Astrophysics ,Giant star ,Graph ,Main sequence ,law.invention - Abstract
We have already covered many topics in our description of a star’s basic characteristics, such as its mass, radius, spectral type and temperature. We can now put all of these parameters together to form a picture of how a star evolves. This is often quite useful in many sciences to represent the characteristics, or data, about a group of objects in the form of a graph.
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- 2023
7. The Mysterious Case of V838 Monocerotis and the Red Novae
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Stevenson, David S. and Stevenson, David S.
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- 2014
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8. Northern Hemisphere: The Empty Sky
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Bordeleau, André G. and Bordeleau, André G.
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- 2014
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9. NGC 6124: a young open cluster with anomalous- and fast-rotating giant stars
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F. A. Ferreira, Natalia A. Drake, Laura Magrini, J. R. P. da Silva, F. F. S. Maia, N. Holanda, W. J. B. Corradi, and C. B. Pereira
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Physics ,Space and Planetary Science ,Astronomy and Astrophysics ,Astrophysics ,Giant star ,Open cluster - Abstract
We present the results of a chemical analysis of fast and anomalous rotator giants members of the young open cluster NGC 6124. For this purpose, we carried out abundances of the mixing sensitive species such as Li, C, N, Na, and 12C/13C isotopic ratio, as well as other chemical species for a sample of four giants among the seven observed ones. This study is based on standard spectral analysis technique using high-resolution spectroscopic data. We also performed an investigation of the rotational velocity ($v\, \sin \, i$) once this sample exhibits abnormal values – giant stars commonly present rotational velocities of few km s−1. In parallel, we have performed a membership study, making use of the third data release from ESA Gaia mission. Based on these data, we estimated a distance of d = 630 pc and an age of 178 Myr through isochrone fitting. After that procedure, we matched all the information raised and investigated the evolutionary stages and thermohaline mixing model through of spectroscopic Teff and $\log \, g$ and mixing tracers, such as 12C/13C and Na, of the studied stars. We derived a low mean metallicity of [Fe/H] = −0.13 ± 0.05 and a modest enhancement of the elements created by the s-process, such as Y, Zr, La, Ce, and Nd, which is in agreement with what has already been reported in the literature for young clusters. The giants analysed have homogeneous abundances, except for lithium abundance [$\log \, \epsilon$(Li)NLTE = 1.08 ± 0.42] and this may be associated with a combination of mechanisms that act increasing or decreasing lithium abundances in stellar atmospheres.
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- 2021
10. Frequency Dependence of Δν of Solar-Like Oscillators Investigated: Influence of HeII Ionization Zone
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Hekker, S., Basu, Sarbani, Elsworth, Y., Chaplin, W. J., Suárez, J.C., editor, Garrido, R., editor, Balona, L. A., editor, and Christensen-Dalsgaard, J., editor
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- 2013
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11. The Hunter’s Stars
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Marett-Crosby, Michael and Marett-Crosby, Michael
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- 2013
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12. Red Giant Stars: Probing the Milky Way Chemical Enrichment
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Chiappini, Cristina, Miglio, Andrea, editor, Montalbán, Josefina, editor, and Noels, Arlette, editor
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- 2012
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13. Recognizing Black Holes
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Meier, David L. and Meier, David L.
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- 2012
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14. Naked-Eye Objects
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Inglis, Michael D. and Inglis, Michael D.
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- 2012
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15. Two-wind interactions in binaries with two orbiting giant stars
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A. C. Raga, Jorge Cantó, P. R. Rivera-Ortiz, Zakaria Meliani, Ary Rodríguez-González, and A. Castellanos-Ramírez
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Orbital plane ,Red giant ,Astrophysics::High Energy Astrophysical Phenomena ,Continuum (design consultancy) ,FOS: Physical sciences ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,01 natural sciences ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,Physics ,Spiral galaxy ,010308 nuclear & particles physics ,Astronomy and Astrophysics ,Giant star ,Astrophysics - Astrophysics of Galaxies ,Planetary nebula ,Orbit ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,Astrophysics::Earth and Planetary Astrophysics - Abstract
Some red giant envelopes present spiral structures (seen either in dust scattered stellar continuum or in molecular line emission), the most striking example probably being AFGL 3068. This object has been modeled (both analytically and numerically) in terms of a wind ejected from a star in orbit around a binary companion. We revisit both analytical models and 3D simulations of a wind from an orbiting red giant star, and extend the numerical simulations to the case of a binary with two red giants with strong winds. We find that most two-wind models on the orbital plane show a "double spiral" structure close to the binary source, and that these two arms merge into a single spiral structure at larger distances. However, for the case of a binary with two identical winds the two spiral arms are still present at large distances from the binary source. We also find that for models of two (not identical) dynamically important winds, a region close to the orbital plane has material from both winds. Also, an approximately conical region centered on the orbital axis is filled exclusively by the wind with larger momentum rate. These two structures lead to morphologies reminiscent of the so-called "hour glass" planetary nebulae. Finally, we find that increasing wind velocity disparities lead to the formation of clumpy structures along the spiral amrs. Observations of "clumpy spirals" are therefore likely to indicate the presence of two strong winds from the stars in the central binary system., Comment: 9 pages, 10 figures
- Published
- 2021
16. Asteroseismology of overmassive, undermassive, and potential past members of the open cluster NGC 6791
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Andrea Miglio, Torben Arentoft, Jens Jessen-Hansen, Karsten Brogaard, Brogaard, K, Arentoft, T, Jessen-Hansen, J, and Miglio, A
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oscillations [stars] ,peculiar [stars] ,Physics ,010308 nuclear & particles physics ,fundamental parameters [stars] ,FOS: Physical sciences ,stars: peculiar– stars: fundamental parameters – stars: evolution – stars: oscillations – open clusters and associations: individual: NGC 6791 ,Astronomy and Astrophysics ,Astrophysics ,Radius ,Effective temperature ,Giant star ,01 natural sciences ,Asteroseismology ,Photometry (astronomy) ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,evolution [stars] ,0103 physical sciences ,Cluster (physics) ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,individual: NGC 6791 [open clusters and associations] ,Open cluster - Abstract
We perform an asteroseismic investigation of giant stars in the field of NGC 6791 with previous indications of atypical evolution. The analysis makes use of observations from Kepler and Gaia in combination with ground-based photometry, a literature radial-velocity study, and measurements of eclipsing binaries in the cluster. We derive mass, radius, effective temperature, evolutionary stage and apparent distance modulus of each target. Among the investigated cluster giants we find clear evidence of overmassive and undermassive members, and non-members with strong hints of potential past membership. Our results indicate that about 10% of the red giants in the cluster have experienced mass-transfer or a merger. High resolution, high-S/N spectroscopic follow-up could confirm potential past membership of the non-members, and reveal whether certain element abundances might expose the non-standard evolution of overmassive and undermassive stars. If so, field stars of similar type could be identified as what they are, i.e. over- or undermassive stars, and not mistakenly classified as younger or older than they are., 14 pages, 5 figures, accepted for publication in MNRAS
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- 2021
17. Physical Parameters of Evolved Stars in Clusters and in the Field from Line-depth Ratios
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Biazzo, K., Pasquini, L., Frasca, A., da Silva, L., Girardi, L., Hatzes, A. P., Setiawan, J., Catalano, S., Marilli, E., Leibundgut, Bruno, editor, Santos, Nuno C., editor, Pasquini, Luca, editor, Correia, Alexandre C. M., editor, and Romaniello, Martino, editor
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- 2008
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18. Stellar Diameters: Breaking the Barriers
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Richichi, A., Leibundgut, Bruno, editor, Richichi, A., editor, Delplancke, F., editor, Paresce, F., editor, and Chelli, A., editor
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- 2008
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19. KIC 7732964 – A Possible Candidate FK Com-Type Star
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I. S. Savanov, V. B. Puzin, and E. S. Dmitrienko
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Physics ,Subgiant ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Star (graph theory) ,Stellar classification ,Giant star ,Subdwarf ,law.invention ,Stars ,Photometry (astronomy) ,law ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics::Galaxy Astrophysics ,Flare - Abstract
This article is a brief survey of our previous work devoted to searching for candidate type FK Com giant stars and an analysis of data for yet another new candidate, KIC 7732964. Establishing that KIC 7732964 belongs to this group of stars requires further study of the evolutionary status of the star (dwarf, subdwarf, or giant). The star has fast rotation and high flare activity, which are more typical of dwarf or subgiant stars. As for other candidates, in the case of KIC 7732964 additional spectral observations are required to establish the absence of binarity, refine the value of the acceleration of gravity, and its spectral classification.
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- 2021
20. Lithium Rich Red Giant Branch Stars
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de la Reza, R., Leibundgut, Bruno, editor, Randich, Sofia, editor, and Pasquini, Luca, editor
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- 2006
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21. The Prospects of Searching for Planets of Brown Dwarfs with CRIRES
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Guenther, Eike W., Käufl, Hans Ulrich, editor, Siebenmorgen, Ralf, editor, and Moorwood, Alan F. M., editor
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- 2005
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22. Infrared Searches for Extrasolar Planets
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Hatzes, Artie, Käufl, Hans Ulrich, editor, Siebenmorgen, Ralf, editor, and Moorwood, Alan F. M., editor
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- 2005
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23. Observing the influence of the youngest super star clusters in NGC 1569: Keck Brackett α spectroscopy
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D. Cohen, S. Michelle Consiglio, Sara C. Beck, and Jean L. Turner
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Physics ,010308 nuclear & particles physics ,Astronomy and Astrophysics ,Astrophysics ,Giant star ,Astrophysics - Astrophysics of Galaxies ,01 natural sciences ,Spectral line ,Delta-v (physics) ,Stars ,Star cluster ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,0103 physical sciences ,Continuum (set theory) ,Spectroscopy ,010303 astronomy & astrophysics ,Line (formation) - Abstract
We report Keck-NIRSPEC observations of the Brackett $\alpha$ 4.05 $\mu$m recombination line across the two candidate embedded super star clusters (SSCs) in NGC 1569. These SSCs power a bright HII region and have been previously detected as radio and mid-infrared sources. Supplemented with high resolution VLA mapping of the radio continuum along with IRTF-TEXES spectroscopy of the [SIV] 10.5 $\mu$m line, the Brackett $\alpha$ spectra data provide new insight into the dynamical state of gas ionized by these forming massive clusters. NIR sources detected in 2 $\mu$m images from the Slit-viewing Camera are matched with GAIA sources to obtain accurate celestial coordinates and slit positions to within $\sim 0.1''$. Br$\alpha$ is detected as a strong emission peak powered by the less luminous infrared source, MIR1 ($L_{\rm IR}\sim 2\times10^7~L_\odot$). The second candidate SSC MIR2 is more luminous ($L_{\rm IR}\gtrsim 4\times10^8~L_\odot$) but exhibits weak radio continuum and Br$\alpha$ emission, suggesting the ionized gas is extremely dense ($n_e\gtrsim 10^5$ cm$^{-3}$), corresponding to hypercompact HII regions around newborn massive stars. The Br$\alpha$ and [SIV] lines across the region are both remarkably symmetric and extremely narrow, with observed line widths $\Delta v \simeq 40$ km s$^{-1}$, FWHM. This result is the first clear evidence that feedback from NGC 1569's youngest giant clusters is currently incapable of rapid gas dispersal, consistent with the emerging theoretical paradigm in the formation of giant star clusters., Comment: Accepted for publication in MNRAS 2021 Feb 26; 9 pages, 7 figures
- Published
- 2021
24. Surface Rotation of LAMOST-Kepler Li-rich Giant Stars
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BI Shao-lan, Yan Hong-liang, Shi Jian-Rong, and DU Ming-hao
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Physics ,Rotation period ,010308 nuclear & particles physics ,Stellar rotation ,Astronomy and Astrophysics ,Astrophysics ,Rotation ,Giant star ,01 natural sciences ,Asteroseismology ,Spectral line ,Red-giant branch ,Stars ,Space and Planetary Science ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
The years-long high-precision photometric data observed by Kepler satellite combining with huge amount of spectra observed by LAMOST provide a great opportunity to study the relations between surface rotation and lithium abundance of li-rich giants. In this study, we cross match the Kepler data with li-rich giants catalog from LAMOST, and obtain 619 common sources. Then we measure 36 rotation periods from the full set of 295 li-rich giants with good data quality which consists of two sub-samples. The rotation periods of 14 stars was extracted from 205 stars with evolutionary stages determined using asteroseismology, including 11 core helium-burning stars (HeBs), 2 red giant branch stars (RGBs), and 1 unclassified star. All the super lithium-rich giant stars ( A ( Li ) > 3.3 dex ) are HeBs in our sample. The remaining 90 giants do not have evolutionary stages confirmed, and in this sub-sample, 22 giants have their rotation period measured. The rotation detection rate of the former sub-sample is 6.8%, which is significantly higher than the detection rate of a large giant sample in previous studies (2.08%). With the surface rotation period measured, we confirm the relation between stellar rotation and lithium enrichment of giants. Meanwhile, we find that the less Li-enriched stars have a relatively dispersed distribution of rotation periods, and the giants with a high Li enrichment is concentrated on the rapidly rotating area, which is consistent with earlier studies. The present work also shows a jump at A ( Li ) ≈ 3.3 dex in the relation between rotation period and Li abundance that coincidently is the boundary between Li-rich giants and super Li-rich giants which may indicate the different mechanisms. The rotation periods of super Li-rich giants become shorter as the lithium enrichment increases. This correlation provides an evidence for the rotational induced extra-mixing mechanism responsible for Li enrichment of giants.
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- 2021
25. Stellar Distribution in the Galactic Disk from NIR Color-Magnitude Diagrams
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Cabrera-Lavers, A., Garzón, F., Hammersley, P., Burton, W. B., editor, Alfaro, Emilio J., editor, Pérez, Enrique, editor, and Franco, José, editor
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- 2004
- Full Text
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26. Elevating the Status of Dust
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Wickramasinghe, Chandra, Wickramasinghe, Chandra, editor, Burbidge, Geoffrey, editor, and Narlikar, Jayant, editor
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- 2003
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27. Ground Based Testing of the GAIA Filters
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Flynn, Chris, Vansevičius, Vladas, editor, Kučinskas, Arūnas, editor, and Sūdžius, Jokūbas, editor
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- 2002
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28. Tomography of the Atmosphere of Long-Period Variable Stars
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Jorissen, A., Alvarez, R., Plez, B., Gillet, D., Fokin, A., Beig, R., editor, Ehlers, J., editor, Frisch, U., editor, Hepp, K., editor, Hillebrandt, W., editor, Imboden, D., editor, Jaffe, R. L., editor, Kippenhahn, R., editor, Lipowsky, R., editor, Löhneysen, H. v., editor, Ojima, I., editor, Weidenmüller, H. A., editor, Wess, J., editor, Zittartz, J., editor, Boffin, Henri M.J., editor, Cuypers, Jan, editor, and Steeghs, Danny, editor
- Published
- 2001
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29. Virtual reality — symbiosis of science and art
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Bulirsch, R., Hardt, M., and Hruby, Walter, editor
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- 2001
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30. Metal-rich Globular Clusters: An Unaccounted Factor Responsible for Their Formation?
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Kravtsov, V.V., Leibundgut, Bruno, editor, Richtler, Tom, editor, and Larsen, Søren, editor
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- 2009
- Full Text
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31. Elliptical Galaxy Chemical Evolution
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Worthey, Guy, Bergeron, Jacqueline, editor, Walsh, Jeremy R., editor, and Rosa, Michael R., editor
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- 1999
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32. New Views on the Early Evolution of Oxygen in the Galaxy
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Rebolo, R., Israelian, G., López, R. J. García, and Spite, M., editor
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- 1999
- Full Text
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33. Abundances in Globular Clusters
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Sneden, C. and Spite, M., editor
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- 1999
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34. Li-rich giant stars under scrutiny: binarity, magnetic activity, and the evolutionary status after Gaia DR2
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Matthieu Castro, B. F. O. Gonçalves, L. de Almeida, J. S. da Costa, and J-D do Nascimento
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Evolution – stars ,FOS: Physical sciences ,radial velocities – techniques [Techniques] ,Astrophysics ,Spectroscopic – stars ,01 natural sciences ,Spectral line ,Photometry (optics) ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Emission spectrum ,010303 astronomy & astrophysics ,Spectrograph ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,Physics ,010308 nuclear & particles physics ,Astronomy and Astrophysics ,Giant star ,Magnetic field ,Radial velocity ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Late-type – stars ,Abundances – stars ,Astrophysics::Earth and Planetary Astrophysics - Abstract
We present a study of the evolutionary state of a few lithium-rich giant stars based on the Gaia Data Release 2 (DR2) parallaxes and photometry. We also investigate the chromospheric activity, the presence of a surface magnetic field, and the radial velocity for our sample stars. We analysed both archive and new data. We gathered archive spectra from several instruments, mainly ELODIE and NARVAL, and we added new data acquired with the spectrograph MUSICOS. We applied the least-squares deconvolution technique to obtain Stokes V and I mean profiles to compute longitudinal magnetic field for a subset. Moreover, for the same subset, we analysed the Ca ii H&K emission lines to calculate the S-index. We also derived atmospheric parameters and Li abundances for all 18 stars of our sample. We found that stars previously classified as red giant branch (RGB) may actually be at a different evolutionary state. Furthermore, we identified that most stars in our sample with detection of surface magnetic field show at least moderate rotation velocities, but none the less, we could not detect a magnetic field in two fast rotators. Because of our small sample of magnetic giants, it is difficult to determine if the presence of surface magnetic field and the Li-rich giant phenomena could be somehow linked. The large variation of the radial velocity of part of our sample indicates that some of them might have a binary companion, which may change the way we look at the Li problem in giant stars.
- Published
- 2020
35. Photometric and Spectral Study of the Be/X-Ray Binary Object V725 Tau=A0535+262
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M. Krugov, G. K. Aimanova, B. K. Omar, A. V. Kusakin, E. K. Denissyuk, L. N. Kondratyeva, and I. V. Reva
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Physics ,Brightness ,010308 nuclear & particles physics ,X-ray binary ,Astronomy and Astrophysics ,Astrophysics ,Giant star ,Stellar classification ,01 natural sciences ,Pulsar ,0103 physical sciences ,Radiative transfer ,Emission spectrum ,Variable star ,010303 astronomy & astrophysics - Abstract
This is a study of spectral and photometric observations of the binary system with an X-ray component V725 Tauri=A0535+262. It consists of a giant star HDE 245770 of spectral class O9.7 and the pulsar A0535+26 with a pulsation period of ~103 s. Active stages of this object, accompanied by “giant” X-ray outbursts, have been observed repeatedly. The last events occurred during 2009-2011. Our studies in 2017-2020 yielded the following data: over the last three years the B and V band brightness of the object has remained at a high level and began to decrease at the end of 2019. Here, beginning in 2016 a gradual increase in the radiative fluxes in the Hβ and Hα emission lines has been observed. At present the equivalent widths of these lines exceed the values recorded during the time of the gigan X-ray outburst of 2011. Previous studies have shown that a similar combination of the characteristics of this object, specifically an increase in emission line fluxes as the brightness decreases. is detected just before the onset of an active stage.
- Published
- 2020
36. Determining rotational and macroturbulent velocities of cool magnetic giant stars
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Agnès Lèbre, Julien Morin, Stefan Georgiev, Eric Josselin, Renada Konstantinova-Antova, Laboratoire Univers et Particules de Montpellier (LUPM), and Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Montpellier 2 - Sciences et Techniques (UM2)
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Physics ,010308 nuclear & particles physics ,stars: late-type ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Giant star ,01 natural sciences ,Astrophysics - Solar and Stellar Astrophysics ,stars: rotation ,Space and Planetary Science ,0103 physical sciences ,stars: individual (RZ Arietis) ,stars: fundamental parameters ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
An original method of estimating the projected rotational velocity, $vsini$, and the macroturbulent velocity, $v_{\rm mac}$, of evolved M giant stars is presented. It is based on the use of spectrum synthesis and multi-line analysis tools. The goal is to fit the mean line profile of observations with that of synthetic spectra. The method is applied to the red giant star RZ Ari and the results $v\sin i$ = 6.0 $\pm$ 0.5 km/s and $v_{\rm mac}$ = 2.0 $\pm$ 1.0 km/s are obtained.
- Published
- 2020
37. Bisector Analysis of HD 199719
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M. Yılmaz and Didem Dilan Izci
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yıldızlar ,stars ,Science (General) ,ötegezegenler ,dikine hız ,Astrophysics ,Spectral line ,Q1-390 ,dev yıldızlar ,çizgi ortay analizi ,Astrophysics::Solar and Stellar Astrophysics ,exoplanet ,giant stars ,Line (formation) ,Physics ,Cross-correlation ,Stars,Giant stars,Exoplanet,Bisector,Radial velocity,Cross-correlation function ,cross-correlation function ,General Medicine ,Giant star ,çapraz korelasyon fonksiyonu ,Exoplanet ,Radial velocity ,Stars ,radial velocity ,Astrophysics::Earth and Planetary Astrophysics ,bisector ,Equivalent width ,Yıldızlar,Dev yıldızlar,Ötegezegenler,Çizgi ortay analizi,Dikine Hız,Çapraz korelasyon fonksiyonu - Abstract
Bu çalışmada, TÜBİTAK Ulusal Gözlemevinde (TUG) devam etmekte olan ötegezegen araştırmasının bir parçası olarak HD 199719’un tayfsal çizgi ortaylarının (bisektör) değişimleri incelendi. Gözlemsel tayflara bir şablon tayf ile çapraz korelasyon fonksiyonları (CCF) uygulanarak, ortalama çizgi profilleri elde edildi. Bu profillerden çizgi ortayları belirlendi. Bu çizgi ortaylarını nicel olarak tanımlamak için çizgi ortay ölçütleri kullanıldı. Bu ölçütler ile çizgi profillerindeki hız alanları hesaplandı ve dikine hız ölçümleri arasındaki ilişki araştırıldı. Yıldızın doğası kaynaklı (bulgurlanma (granülasyon), zonklama (pulsasyon), manyetik etkinlik kaynaklı yüzey lekeleri ve manyetik çevrim gibi) etkileri araştırmak için çizgi ortayların yanı sıra, Hα ve H çizgilerinin eşdeğer genişlik ölçümleri de yapıldı. Yıldızın çizgi ortay hız ile dikine hız değerleri arasında bir korelasyon olmadığı görüldü. Çizgi ortay hız ölçümleri (BIS ve BVC) için yapılan dönem analizlerinde 4.88 ve 10.36 günlük dönemleri işaret eden pikler elde edildi. Hα’nın eşdeğer genişlik ölçümleri için uzun dönemli bir değişim olabileceği görülse de, benzer bir değişim H’nın eşdeğer genişlik ölçümlerinde elde edilmedi., In this study, an analysis of spectral line bisector variations for HD 199719 which was examined as a part of the exoplanet studies that carried on the TÜBİTAK National Observatory (TUG). Cross-correlation functions (CCF) were implemented to the observed spectra using some template spectra to determine mean line profile. Line bisectors were derived from mean line profiles. In order to quantify asymmetries on the line profiles, some bisectors criteria were used. The velocity spans were calculated in the profiles with these criteria and correlation between the star’s radial velocity measurements were investigated. In addition, equivalent width measurements of the Hα and H were performed to check other variability due to nature of star (granulation, pulsation, magnetic cycle and stellar spots due to activity). No correlation has been found between the radial velocity and line bisectors measurements. Period analysis for bisectors (BIS and BVC) show that significant periodicity appearing around 4.88 and 10.36 days. Although there was a long-term variation for the equivalent width measurements of Hα, a similar change was not obtained for equivalent width measurements of H.
- Published
- 2020
38. Giant star-forming clumps?
- Author
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Wiphu Rujopakarn, A. D. Biggs, E. Falgarone, P. van der Werf, V. Arumugam, Martin Zwaan, Rob Ivison, Johan Richard, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Strong gravitational lensing ,FOS: Physical sciences ,galaxies: starburst ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,01 natural sciences ,infrared: galaxies ,galaxies: high-redshift ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Instrumentation and Methods for Astrophysics (astro-ph.IM) ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,Galaxy cluster ,Physics ,Luminous infrared galaxy ,010308 nuclear & particles physics ,Star formation ,Molecular cloud ,Astronomy and Astrophysics ,Giant star ,Astrophysics - Astrophysics of Galaxies ,Galaxy ,Interstellar medium ,Astrophysics - Solar and Stellar Astrophysics ,[SDU]Sciences of the Universe [physics] ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,galaxies: structure ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics - Instrumentation and Methods for Astrophysics ,submillimetre: galaxies - Abstract
With the spatial resolution of the Atacama Large Millimetre Array (ALMA), dusty galaxies in the distant Universe typically appear as single, compact blobs of dust emission, with a median half-light radius, $\approx$ 1 kpc. Occasionally, strong gravitational lensing by foreground galaxies or galaxy clusters has probed spatial scales 1-2 orders of magnitude smaller, often revealing late-stage mergers, sometimes with tantalising hints of sub-structure. One lensed galaxy in particular, the Cosmic Eyelash at $z=$ 2.3, has been cited extensively as an example of where the interstellar medium exhibits obvious, pronounced clumps, on a spatial scale of $\approx$ 100 pc. Seven orders of magnitude more luminous than giant molecular clouds in the local Universe, these features are presented as circumstantial evidence that the blue clumps observed in many $z\sim$ 2-3 galaxies are important sites of ongoing star formation, with significant masses of gas and stars. Here, we present data from ALMA which reveal that the dust continuum of the Cosmic Eyelash is in fact smooth and can be reproduced using two S\'ersic profiles with effective radii, 1.2 and 4.4 kpc, with no evidence of significant star-forming clumps down to a spatial scale of $\approx$ 80 pc and a star-formation rate of $, Comment: 5 pages; 3 figures; in press as a Letter to MNRAS
- Published
- 2020
39. A high-resolution spectroscopic study of two new Na- and Al-rich field giants–likely globular cluster escapees in the Galactic halo
- Author
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Avrajit Bandyopadhyay, Sivarani Thirupathi, A Susmitha, and Timothy C. Beers
- Subjects
Physics ,FOS: Physical sciences ,chemistry.chemical_element ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Giant star ,Astrophysics - Astrophysics of Galaxies ,Galactic halo ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,chemistry ,Space and Planetary Science ,Nucleosynthesis ,Astrophysics of Galaxies (astro-ph.GA) ,Globular cluster ,Astrophysics::Solar and Stellar Astrophysics ,Lithium ,Astrophysics::Earth and Planetary Astrophysics ,Halo ,Spectrograph ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics - Abstract
The stars SDSS J064655.6+411620.5 and SDSS J193712.01+502455.5 are relatively bright stars that were initially observed as part of the SDSS/MARVELS pre-survey. They were selected, on the basis of their weak CH $G$-bands, along with a total of 60 others, in the range of halo globular cluster metallicities for high-resolution spectroscopic follow-up as a part of the HESP-GOMPA survey (Hanle Echelle SPectrograph -- Galactic survey Of Metal Poor stArs). The stars exhibit typical nucleosynthesis signatures expected from the so-called second-generation stars of globular clusters. The light-element anti-correlation of Mg-Al is detected, along with elevated abundances of Na. Carbon is found to be depleted, which is compatible with expectation. Lithium is also detected in SDSS J064655.6+411620.5 and SDSS J193712.01+502455.5; the measured abundances are similar to those of normal halo giant stars. These bright escapees provide a unique opportunity to study the nucleosynthesis events of globular clusters in great detail, and shed light on their chemical-enrichment histories., 8 pages, 5 figures, 3 tables, Accepted for publication in MNRAS
- Published
- 2020
40. Precision angular diameters for 16 southern stars with VLTI/PIONIER
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Michael J. Ireland, Luca Casagrande, Adam D. Rains, I. Karovicova, and Timothy R. White
- Subjects
FOS: Physical sciences ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,01 natural sciences ,law.invention ,Photometry (optics) ,Angular diameter ,law ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,Physics ,010308 nuclear & particles physics ,Bolometer ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astronomy and Astrophysics ,Giant star ,Stars ,Interferometry ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Limb darkening ,Astrophysics::Earth and Planetary Astrophysics ,Data reduction - Abstract
In the current era of Gaia and large, high signal to noise stellar spectroscopic surveys, there is an unmet need for a reliable library of fundamentally calibrated stellar effective temperatures based on accurate stellar diameters. Here we present a set of precision diameters and temperatures for a sample of 6 dwarf, 5 sub-giant, and 5 giant stars observed with the PIONIER beam combiner at the VLTI. Science targets were observed in at least two sequences with five unique calibration stars each for accurate visibility calibration and to reduce the impact of bad calibrators. We use the standard PIONIER data reduction pipeline, but bootstrap over interferograms, in addition to employing a Monte-Carlo approach to account for correlated errors by sampling stellar parameters, limb darkening coefficients, and fluxes, as well as predicted calibrator angular diameters. The resulting diameters were then combined with bolometric fluxes derived from broadband Hipparcos-Tycho photometry and MARCS model bolometric corrections, plus parallaxes from Gaia to produce effective temperatures, physical radii, and luminosities for each star observed. Our stars have mean angular diameter and temperatures uncertainties of 0.8% and 0.9% respectively, with our sample including diameters for 10 stars with no pre-existing interferometric measurements. The remaining stars are consistent with previous measurements, with the exception of a single star which we observe here with PIONIER at both higher resolution and greater sensitivity than was achieved in earlier work., Comment: Published in MNRAS, 22 pages, 7 figures
- Published
- 2020
41. Molecules of Non-Photospheric Origin in Red Giants and Supergiants Revealed by the ISO SWS
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Tsuji, T., Ohnaka, K., Aoki, W., Yamamura, I., Dyson, John, editor, Lamb, Susan A., editor, Cameron, A. G. W., editor, Cherepashchuk, A. M., editor, Fälthammar, C.-G., editor, Kitamura, M., editor, Waters, L. B. F. M., editor, Waelkens, C., editor, van der Hucht, K. A., editor, and Zaal, P. A., editor
- Published
- 1998
- Full Text
- View/download PDF
42. The Stars of Winter, Part 2
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Upgren, Arthur and Upgren, Arthur
- Published
- 1998
- Full Text
- View/download PDF
43. Giant Stars
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Fischer, Daniel, Duerbeck, Hilmar, Fischer, Daniel, and Duerbeck, Hilmar
- Published
- 1998
- Full Text
- View/download PDF
44. Is an Engulfment Event at the Origin of the Li-Rich Giants?
- Author
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Melo, C.H.F., de Laverny, P., Santos, N.C., Israelian, G., Randich6, S., do Nascimento, J.D.Jr., De Medeiros, J.R., Leibundgut, Bruno, editor, Randich, Sofia, editor, and Pasquini, Luca, editor
- Published
- 2006
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45. The Pan-Pacific Planet Search – VIII. Complete results and the occurrence rate of planets around low-luminosity giants
- Author
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Michaela Collins, Jonathan Horner, R. P. Butler, Brad D. Carter, C. G. Tinney, Liang Wang, John Asher Johnson, Jake T. Clark, and Robert A. Wittenmyer
- Subjects
010504 meteorology & atmospheric sciences ,FOS: Physical sciences ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Luminosity ,law.invention ,Telescope ,Planet ,law ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,0105 earth and related environmental sciences ,Earth and Planetary Astrophysics (astro-ph.EP) ,Physics ,Astronomy ,Astronomy and Astrophysics ,Planetary system ,Giant star ,Radial velocity ,Orbit ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics - Earth and Planetary Astrophysics - Abstract
Our knowledge of the populations and occurrence rates of planets orbiting evolved intermediate-mass stars lags behind that for solar-type stars by at least a decade. Some radial velocity surveys have targeted these low-luminosity giant stars, providing some insights into the properties of their planetary systems. Here we present the final data release of the Pan-Pacific Planet Search, a 5-year radial velocity survey using the 3.9m Anglo-Australian Telescope. We present 1293 precise radial velocity measurements for 129 stars, and highlight six potential substellar-mass companions which require additional observations to confirm. Correcting for the substantial incompleteness in the sample, we estimate the occurrence rate of giant planets orbiting low-luminosity giant stars to be approximately 7.8$^{+9.1}_{-3.3}$\%. This result is consistent with the frequency of such planets found to orbit main-sequence A-type stars, from which the PPPS stars have evolved., Comment: Accepted for publication in MNRAS. Full text of tables A1 and A2 available from the lead author in exchange for advice on how to make MNRAS format long tables properly
- Published
- 2019
46. Asteroseismology of iota Draconis and Discovery of an Additional Long-period Companion
- Author
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Enrico Corsaro, William J. Chaplin, James S. Kuszlewicz, Zhexing Li, Benjamin J. Fulton, S. N. Breton, Rafael A. García, Derek Buzasi, Tanda Li, Dennis Stello, J. M. Joel Ong, Timothy D. Brandt, Paul A. Dalba, Marc Hon, Savita Mathur, Keivan G. Stassun, Aldo Serenelli, Timothy R. White, Timothy R. Bedding, Margarida S. Cunha, Chen Jiang, Benjamin J. S. Pope, Daniel Huber, Cenk Kayhan, Michelle L. Hill, Stephen R. Kane, Tiago L. Campante, Diego Bossini, European Commission, Ministerio de Ciencia, Innovación y Universidades (España), Alfred P. Sloan Foundation, National Aeronautics and Space Administration (US), and Australian Research Council
- Subjects
Radial velocity ,Stellar astronomy ,Exoplanet astronomy ,FOS: Physical sciences ,Statistics::Other Statistics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Asteroseismology ,Photometry ,Planetary dynamics ,Planet ,0103 physical sciences ,Exoplanet detection methods ,Astrophysics::Solar and Stellar Astrophysics ,Exoplanet systems ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,Earth and Planetary Astrophysics (astro-ph.EP) ,Physics ,010308 nuclear & particles physics ,Exoplanet dynamics ,Exoplanets ,Astronomy ,Astronomy and Astrophysics ,Astrometry ,Orbital period ,Giant star ,Exoplanet ,Detection ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,13. Climate action ,Space and Planetary Science ,Planet hosting stars ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics - Earth and Planetary Astrophysics - Abstract
Hill, Michelle L., et al., Giant stars as known exoplanet hosts are relatively rare due to the potential challenges in acquiring precision radial velocities and the small predicted transit depths. However, these giant host stars are also some of the brightest in the sky and so enable high signal-to-noise ratio follow-up measurements. Here, we report on new observations of the bright (V ∼ 3.3) giant star ι Draconis (ι Dra), known to host a planet in a highly eccentric ∼511 day period orbit. TESS observations of the star over 137 days reveal asteroseismic signatures, allowing us to constrain the stellar radius, mass, and age to ∼2%, ∼6%, and ∼28%, respectively. We present the results of continued radial-velocity monitoring of the star using the Automated Planet Finder over several orbits of the planet. We provide more precise planet parameters of the known planet and, through the combination of our radial-velocity measurements with Hipparcos and Gaia astrometry, we discover an additional long-period companion with an orbital period of ∼ {68} {-36} {+60} yr. Mass predictions from our analysis place this substellar companion on the border of the planet and brown dwarf regimes. The bright nature of the star combined with the revised orbital architecture of the system provides an opportunity to study planetary orbital dynamics that evolve as the star moves into the giant phase of its evolution., T.L.C. acknowledges support from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No. 792848 (PULSATION). T.L.C. is supported by Fundação para a Ciência e a Tecnologia (FCT) in the form of a work contract (CEECIND/ 00476/2018). C.K. acknowledges support by Erciyes University Scientific Research Projects Coordination Unit under grant No. MAP-2020-9749. T.L. acknowledges the funding from the European Research Council (ERC) under the European Unionʼs Horizon 2020 research and innovation program (CartographY GA. 804752). D.B. and M.S.C. acknowledge supported by FCT through the research grants UIDB/04434/2020, UIDP/04434/ 2020 and PTDC/FIS-AST/30389/2017, and by FEDER— Fundo Europeu de Desenvolvimento Regional through COMPETE2020—Programa Operacional Competitividade e Internacionalização (grant: POCI-01-0145-FEDER-030389). M.S.C. is supported by national funds through FCT in the form of a work contract. R.A.G. and S.N.B. acknowledge the support of the PLATO and GOLF CNES grants. S.M. acknowledges the support from the Spanish Ministry of Science and Innovation with the Ramon y Cajal fellowship number RYC-2015-17697 and with the grant No. PID2019-107187GB-I00. D.H. acknowledges support from the Alfred P. Sloan Foundation, the National Aeronautics and Space Administration (80NSSC19K0379), and the National Science Foundation (AST-1717000). D.L.B. acknowledges support from the NASA TESS GI Program under awards 80NSSC18K1585 and 80NSSC19K0385. T.R.B. acknowledges support from the Australian Research Council (DP210103119).
- Published
- 2021
47. Radial structure and formation of the Milky Way disc
- Author
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D. Katz, A. E. Gomez, P. Di Matteo, M. Haywood, O. Snaith, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Metallicity ,Milky Way ,FOS: Physical sciences ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Galaxy: disk ,0103 physical sciences ,Galaxy formation and evolution ,Disc ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,Physics ,Galaxy: evolution ,010308 nuclear & particles physics ,Astronomy and Astrophysics ,Radius ,Galactic plane ,Giant star ,Astrophysics - Astrophysics of Galaxies ,Interstellar medium ,13. Climate action ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,Galaxy: abundances ,Astrophysics::Earth and Planetary Astrophysics ,[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph] - Abstract
The formation of the Galactic disc is an enthusiastically debated issue. Numerous studies and models seek to identify the dominant physical process(es) that shaped its observed properties. Taking advantage of the improved coverage of the inner Milky Way provided by the SDSS DR16 APOGEE catalogue and of the ages published in the APOGEE-AstroNN Value Added Catalogue (VAC), we examine the radial evolution of the chemical and age properties of the Galactic stellar disc, with the aim to better constrain its formation. Using a sample of 199,307 giant stars with precise APOGEE abundances and APOGEE-astroNN ages, selected in a +/-2 kpc layer around the galactic plane, we assess the dependency with guiding radius of: (i) the median metallicity, (ii) the ridge lines of the [Fe/H]-[Mg/Fe] and age-[Mg/Fe] distributions and (iii) the Age Distribution Function (ADF). The giant star sample allows us to probe the radial behaviour of the Galactic disc from Rg = 0 to 14-16 kpc. The thick disc [Fe/H]-[Mg/Fe] ridge lines follow closely grouped parallel paths, supporting the idea that the thick disc did form from a well-mixed medium. However, the ridge lines present a small drift in [Mg/Fe], which decreases with increasing guiding radius. At sub-solar metallicity, the intermediate and outer thin disc [Fe/H]-[Mg/Fe] ridge lines follow parallel sequences shifted to lower metallicity as the guiding radius increases. We interpret this pattern, as the signature of a dilution of the inter-stellar medium from Rg~6 kpc to the outskirt of the disc, which occured before the onset of the thin disc formation. The APOGEE-AstroNN VAC provides stellar ages for statistically significant samples of thin disc stars from the Galactic centre up to Rg~14 kpc. An important result provided by this dataset, is that the thin disc presents evidence of an inside-out formation up to R_g~10-12 kpc.(Abridged), Comment: 18 pages, 21 figures, submitted to A&A on 29/01/2021
- Published
- 2021
48. The Effect of Rotation on RGB Surface Abundances
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Charbonnel, C., Bedding, T. R., editor, Booth, A. J., editor, and Davis, J., editor
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- 1997
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49. Indirect Imaging of Stellar Surface Structure
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Hatzes, A. P., Crane, Philippe, editor, and Paresce, Francesco, editor
- Published
- 1997
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50. Imaging the Surfaces of Late-Type Stars
- Author
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Bedding, T. R., von der Lühe, O., Zijlstra, A. A., Crane, Philippe, editor, Walsh, Jeremy R., editor, and Danziger, Ivan J., editor
- Published
- 1995
- Full Text
- View/download PDF
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