Browsing by Subject "techniques: radial"

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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.
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, Michael
We 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.
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, Michael
Precise 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.
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.
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.
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.
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.