Browsing by Subject "velocities"
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Item Convective Line Shifts For The Gaia RVS From The CIFIST 3D Model Atmosphere Grid(2013-02) Prieto, C. Allende; Koesterke, L.; Ludwig, H. G.; Freytag, B.; Caffau, E.; Koesterke, L.Context. To derive space velocities of stars along the line of sight from wavelength shifts in stellar spectra requires accounting for a number of second-order effects. For most stars, gravitational redshifts, convective blueshifts, and transverse stellar motion are the dominant contributors. Aims. We provide theoretical corrections for the net velocity shifts due to convection expected for the measurements from the Gaia Radial Velocity Spectrometer (RVS). Methods. We used a set of three-dimensional time-dependent simulations of stellar surface convection computed with CO5BOLD to calculate spectra of late-type stars in the Gaia RVS range and to infer the net velocity offset that convective motions will induce in radial velocities derived by cross-correlation. Results. The net velocity shifts derived by cross-correlation depend both on the wavelength range and spectral resolution of the observations. Convective shifts for Gaia RVS observations are less than 0.1 km s(-1) for late-K-type stars, and they increase with stellar mass, reaching about 0.3 k ms(-1) or more for early F-type dwarfs. This tendency is the result of an increase with effective temperature in both temperature and velocity fluctuations in the line-forming region. Our simulations also indicate that the net RVS convective shifts can be positive (i.e. redshifts) in some cases. Overall, the blueshifts weaken slightly with increasing surface gravity, and are enhanced at low metallicity. Gravitational redshifts amount to 0.7 km s(-1) and dominate convective blueshifts for dwarfs, but become much weaker for giants.Item Detection Of A Third Planet In The HD 74156 System Using The Hobby-Eberly Telescope(2008-01) Bean, Jacob L.; McArthur, Barbara E.; Benedict, G. Fritz; Armstrong, Amber; Bean, Jacob L.; McArthur, Barbara E.; Benedict, G. Fritz; Armstrong, AmberWe report the discovery of a third planetary-mass companion to the G0 star HD 74156. High-precision radial velocity measurements made with the Hobby-Eberly Telescope aided the detection of this object. The best-fit triple-Keplerian model to all the available velocity data yields an orbital period of 347 days and a minimum mass of 0.4 M-Jup for the new planet. We determine revised orbital periods of 51.7 and 2477 days and minimum masses of 1.9 and 8.0 M-Jup, respectively, for the previously known planets. Preliminary calculations indicate that the derived orbits are stable, although all three planets have significant orbital eccentricities (e = 0.64, 0.43, and 0.25). With our detection, HD 74156 becomes the eighth normal star known to host three or more planets. Further study of this system's dynamical characteristics will likely give important insight into planet formation and evolutionary processes.Item The Lick-Carnegie Exoplanet Survey: Gliese 687 B-A Neptune-Mass Planet Orbiting A Nearby Red Dwarf(2014-07) Burt, Jennifer; Vogt, Steven S.; Butler, R. Paul; Hanson, Russell; Meschiari, Stefano; Rivera, Eugenio J.; Henry, Gregory W.; Laughlin, Gregory; Meschiari, StefanoPrecision radial velocities from the Automated Planet Finder (APF) and Keck/HIRES reveal an M sin(i) = 18 +/- 2M(circle plus) planet orbiting the nearby M3V star GJ 687. This planet has an orbital period P = 38.14 days and a low orbital eccentricity. Our Stromgren b and y photometry of the host star suggests a stellar rotation signature with a period of P = 60 days. The star is somewhat chromospherically active, with a spot filling factor estimated to be several percent. The rotationally induced 60 day signal, however, is well separated from the period of the radial velocity variations, instilling confidence in the interpretation of a Keplerian origin for the observed velocity variations. Although GJ 687 b produces relatively little specific interest in connection with its individual properties, a compelling case can be argued that it is worthy of remark as an eminently typical, yet at a distance of 4.52 pc, a very nearby representative of the galactic planetary census. The detection of GJ 687 b indicates that the APF telescope is well suited to the discovery of low-mass planets orbiting low-mass stars in the as yet relatively un-surveyed region of the sky near the north celestial pole.Item An M Sin I=24 M-Circle Plus Planetary Companion To The Nearby M Dwarf Gj 176(2008-02) Endl, Michael; Cochran, William D.; Wittenmyer, Robert A.; Boss, Alan P.; Endl, Michael; Cochran, William D.; Wittenmyer, Robert A.; Boss, Alan P.We report the detection of a planetary companion with a minimum mass of m sin i 0.0771 M-Jup 24.5 M-circle plus to the nearby (d 9.4 pc) M2.5 V star GJ 176. The star was observed as part of our M dwarf planet search at the Hobby-Eberly Telescope (HET). The detection is based on 5 years of high-precision differential radial velocity (RV) measurements using the High-Resolution Spectrograph (HRS). The orbital period of the planet is 10.24 days. GJ 176 thus joins the small (but increasing) sample of M dwarfs hosting short-period planets with minimum masses in the Neptune-mass range. Low-mass planets could be relatively common around M dwarfs, and the current detections might represent the tip of a rocky planet population.Item New Precision Orbits Of Bright Double-Lined Spectroscopic Binaries. III. HD 82191, Omega Draconis, And 108 Herculis(2009-04) Fekel, Francis C.; Tomkin, Jocelyn; Williamson, Michael H.; Fekel, Francis C.; Tomkin, Jocelyn; Williamson, Michael H.We have determined improved spectroscopic orbits for three double-lined binaries, HD 82191 (Am), omega Dra (F5 V), and 108 Her (Am), using radial velocities from the 2.1 m telescope at McDonald Observatory, the coude feed telescope at Kitt Peak National Observatory, and 2 m telescope at Fairborn Observatory. The orbital periods range from 5.28 to 9.01 days, and all three systems have circular orbits. The new orbital dimensions (a(1) sin i and a(2) sin i) and minimum masses (m(1) sin(3) i and m(2) sin(3) i) have accuracies of 0.2% or better. Our improved results confirm the large minimum masses of HD 82191 and also agree with the values previously found for. Dra. However, for the components of 108 Her our minimum masses are about 20% larger than the previous best values. We conclude that both components of HD 82191 as well as the primary of 108 Her are Am stars. However, the A9 secondary of 108 Her has normal abundances. We estimate spectral types of F4 dwarf and G0 dwarf for the components of. Dra. The primaries of the three binaries are synchronously rotating as is the secondary of 108 Her. The secondaries of HD 82191 and omega Dra are possibly synchronously rotating.Item The Pan-Pacific Planet Search. I. A Giant Planet Orbiting 7 CMa(2011-12) Wittenmyer, Robert A.; Endl, Michael; Wang, Lifan; Johnson, John A.; Tinney, C. G.; O'Toole, S. J.; Endl, MichaelWe introduce the Pan-Pacific Planet Search, a survey of 170 metal-rich Southern Hemisphere subgiants using the 3.9 m Anglo-Australian Telescope. We report the first discovery from this program, a giant planet orbiting 7 CMa (HD 47205) with a period of 763 +/- 17 days, eccentricity e = 0.14 +/- 0.06, and msin i = 2.6 +/- 0.6 M(Jup). The host star is a K giant with a mass of 1.5 +/- 0.3M(circle dot) and metallicity [Fe/H] = 0.21 +/- 0.10. The mass and period of 7 CMa b are typical of planets which have been found to orbit intermediate-mass stars (M(*) > 1.3M(circle dot)). Hipparcos photometry shows this star to be stable to 0.0004 mag on the radial-velocity period, giving confidence that this signal can be attributed to reflex motion caused by an orbiting planet.Item The Pan-Pacific Planet Search. II. Confirmation Of A Two-Planet System Around Hd 121056(2015-02) Wittenmyer, Robert A.; Wang, Lifan; Liu, Fan; Horner, Jonathan; Endl, Michael; Johnson, John A.; Tinney, C. G.; Carter, B. D.; Endl, MichaelPrecise radial velocities from the Anglo-Australian Telescope (AAT) confirm the presence of a rare short-period planet around the K0 giant HD 121056. An independent two-planet solution using the AAT data shows that the inner planet has P = 89.1 +/- 0.1 days, and m sin i = 1.35 +/- 0.17 M-Jup. These data also confirm the planetary nature of the outer companion, with m sin i = 3.9 +/- 0.6 M-Jup and a = 2.96 +/- 0.16 AU. HD 121056 is the most-evolved star to host a confirmed multiple-planet system, and is a valuable example of a giant star hosting both a short-period and a long-period planet.Item A Search for Multi-Planet Systems Using the Hobby-Eberly Telescope(2009-05) Wittenmyer, Rrobert A.; Endl, Michael; Cochran, William D.; Levison, Henry F.; Henry, Gregory W.; Wittenmyer, Rrobert A.; Endl, Michael; Cochran, William D.Extrasolar multiple-planet systems provide valuable opportunities for testing theories of planet Formation and evolution. The architectures of the known multiple-planet systems demonstrate a fascinating level of diversity, which motivates the search for additional examples of such systems in order to better constrain their Formation and dynamical histories. Here we describe a comprehensive investigation of 22 planetary systems in an effort to answer three questions: (1) are there additional planets? (2) where could additional planets reside in stable orbits? and (3) what limits can these observations place on such objects? We find no evidence for additional bodies in any of these systems; indeed, these new data do not support three previously announced planets (HD 20367 b: Udry et al.; HD 74156 d: Bean et al.; and 47 UMa c: Fischer et al.). The dynamical simulations show that nearly all of the 22 systems have large regions in which additional planets could exist in stable orbits. The detection-limit computations indicate that this study is sensitive to close-in Neptune-mass planets for most of the systems targeted. We conclude with a discussion on the implications of these nondetections.Item Transiting Exoplanets From The Corot Space Mission XIV. CoRoT-11B: A Transiting Massive >Hot-Jupiter> In A Prograde Orbit Around A Rapidly Rotating F-Type Star(2010-12) Gandolfi, D.; Hebrard, G.; Alonso, R.; Deleuil, M.; Guenther, E. W.; Fridlund, M.; Endl, M.; Eigmuller, P.; Csizmadia, S.; Havel, M.; Aigrain, S.; Auvergne, M.; Baglin, A.; Barge, P.; Bonomo, A. S.; Borde, P.; Bouchy, F.; Bruntt, H.; Cabrera, J.; Carpano, S.; Carone, L.; Cochran, W. D.; Deeg, H. J.; Dvorak, R.; Eisloffel, J.; Erikson, A.; Ferraz-Mello, S.; Gazzano, J. C.; Gibson, N. B.; Gillon, M.; Gondoin, P.; Guillot, T.; Hartmann, M.; Hatzes, A.; Jorda, L.; Kabath, P.; Leger, A.; Llebaria, A.; Lammer, H.; MacQueen, P. J.; Mayor, M.; Mazeh, T.; Moutou, C.; Ollivier, M.; Patzold, M.; Pepe, F.; Queloz, D.; Rauer, H.; Rouan, D.; Samuel, B.; Schneider, J.; Stecklum, B.; Tingley, B.; Udry, S.; Wuchterl, G.; Cochran, W. D.; Endl, M.; MacQueen, P.J.The CoRoT exoplanet science team announces the discovery of CoRoT-11b, a fairly massive hot-Jupiter transiting a V = 12.9 mag F6 dwarf star (M(*) = 1.27 +/- 0.05 M(circle dot), R(*) = 1.37 +/- 0.03 R(circle dot), T(eff) = 6440 +/- 120 K), with an orbital period of P = 2.994329 +/- 0.000011 days and semi-major axis a = 0.0436 +/- 0.005 AU. The detection of part of the radial velocity anomaly caused by the Rossiter-McLaughlin effect shows that the transit-like events detected by CoRoT are caused by a planet-sized transiting object in a prograde orbit. The relatively high projected rotational velocity of the star (upsilon sin i(star) = 40 +/- 5 km s(-1)) places CoRoT-11 among the most rapidly rotating planet host stars discovered so far. With a planetary mass of M(p) = 2.33 +/- 0.34 M(Jup) and radius R(p) = 1.43 +/- 0.03 R(Jup), the resulting mean density of CoRoT-11b (rho(p) = 0.99 +/- 0.15 g/cm(3)) can be explained with a model for an inflated hydrogen-planet with a solar composition and a high level of energy dissipation in its interior.Item Transiting Exoplanets From The CoRoT Space Mission XXIV. CoRoT-25b and CoRoT-26b: two low-density giant planets(2013-07) Almenara, J. M.; Bouchy, F.; Gaulme, P.; Deleuil, M.; Havel, M.; Gandolfi, D.; Deeg, H. J.; Wuchterl, G.; Guillot, T.; Gardes, B.; Pasternacki, T.; Aigrain, S.; Alonso, R.; Auvergne, M.; Baglin, A.; Bonomo, A. S.; Borde, P.; Cabrera, J.; Carpano, S.; Cochran, W. D.; Csizmadia, S.; Damiani, C.; Diaz, R. F.; Dvorak, R.; Endl, M.; Erikson, A.; Ferraz-Mello, S.; Fridlund, M.; Hebrard, G.; Gillon, M.; Guenther, E.; Hatzes, A.; Leger, A.; Lammer, H.; MacQueen, P. J.; Mazeh, T.; Moutou, C.; Ollivier, M.; Ofir, A.; Patzold, M.; Parviainen, H.; Queloz, D.; Rauer, H.; Rouan, D.; Santerne, A.; Samuel, B.; Schneider, J.; Tal-Or, L.; Tingley, B.; Weingrill, J.; Cochran, W. D.; Endl, M.; MacQueen, P.J.We report the discovery of two transiting exoplanets, CoRoT-25b and CoRoT-26b, both of low density, one of which is in the Saturn mass-regime. For each star, ground-based complementary observations through optical photometry and radial velocity measurements secured the planetary nature of the transiting body and allowed us to fully characterize them. For CoRoT-25b we found a planetary mass of 0.27 similar to 0.04 M-Jup, a radius of 1.08(-0.10)(+0.3) R-Jup and hence a mean density of 0.15(-0.06)(+ 0.15) g cm(-3). The planet orbits an F9 mainsequence star in a 4.86-day period, that has a V magnitude of 15.0, solar metallicity, and an age of 4.5(-2.0) (+1.8)-Gyr. CoRoT-26b orbits a slightly evolved G5 star of 9.06 +/- 1.5-Gyr age in a 4.20-day period that has solar metallicity and a V magnitude of 15.8. With a mass of 0.52 +/- 0.05 MJup, a radius of 1.26(-0.07)(+0.13) R-Jup, and a mean density of 0.28(-0.07)(+0.09) g cm(-3), it belongs to the low-mass hot-Jupiter population. Planetary evolution models allowed us to estimate a core mass of a few tens of Earth mass for the two planets with heavy-element mass fractions of 0.52(-0.15)(+0.08) and 0.26(-0.08)(+0.05), respectively, assuming that a small fraction of the incoming flux is dissipated at the center of the planet. In addition, these models indicate that CoRoT-26b is anomalously large compared with what standard models could account for, indicating that dissipation from stellar heating could cause this size.Item Transiting Exoplanets From The CoRoT Space Mission: XXVI. CoRoT-24: a transiting multiplanet system(2014-07) Alonso, R.; Moutou, C.; Endl, M.; Almenara, J. M.; Guenther, E. W.; Deleuil, M.; Hatzes, A.; Aigrain, S.; Auvergne, M.; Baglin, A.; Barge, P.; Bonomo, A. S.; Borde, P.; Bouchy, F.; Cavarroc, C.; Cabrera, J.; Carpano, S.; Csizmadia, S.; Cochran, W. D.; Deeg, H. J.; Diaz, R. F.; Dvorak, R.; Erikson, A.; Ferraz-Mello, S.; Fridlund, M.; Fruth, T.; Gandolfi, D.; Gillon, M.; Grziwa, S.; Guillot, T.; Hebrard, G.; Jorda, L.; Leger, A.; Lammer, H.; Lovis, C.; MacQueen, P. J.; Mazeh, T.; Ofir, A.; Olivier, M.; Pasternacki, T.; Patzold, M.; Queloz, D.; Rauer, H.; Rouan, D.; Santerne, A.; Schneider, J.; dos Santos, M. T.; Tingley, B.; Titz-Weider, R.; Weingrill, J.; Wuchterl, G.; Cochran, W. D.; Endl, M.; MacQueen, P.J.We present the discovery of a candidate multiply transiting system, the first one found in the CoRoT mission. Two transit like features with periods of 5.11 and 11.76 d are detected in the CoRoT light curve around a main sequence K1V star of r = 15.1. If the features are due to transiting planets around the same star, these would correspond to objects of 3.7 +/- 0.4 and 5.0 +/- 0.5 R-circle plus, respectively. Several radial velocities serve to provide an upper limit of 5.7 M-circle plus for the 5.11 d signal and to tentatively measure a mass of 28(-11)(+11); M-circle plus for the object transiting with a 11.76 d period. These measurements imply low density objects, with a significant gaseous envelope. The detailed analysis of the photometric and spectroscopic data serves to estimate the probability that the observations are caused by transiting Neptune-sized planets as much as over 26 times higher than a blend scenario involving only one transiting planet and as much as over 900 times higher than a scenario involving two blends and no planets. The radial velocities show a long-term modulation that might be attributed to a 1.5 M-Jup planet orbiting at 1.8 AU from the host, but more data are required to determine the precise orbital parameters of this companion.