Browsing by Subject "evolved stars"
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Item The Abundances Of Polyacetylenes Toward CRL618(2011-02) Fonfria, J. P.; Cernicharo, J.; Richter, Matthew J.; Lacy, John H.; Lacy, John H.We present a mid-infrared high spectral resolution spectrum of CRL618 in the frequency ranges 778-784 and 1227-1249 cm(-1) (8.01-8.15 and 12.75-12.85 mu m) taken with the Texas Echelon-cross-Echelle Spectrograph (TEXES) and the Infrared Telescope Facility (IRTF). We have identified more than 170 rovibrational lines arising from C2H2, HCN, C4H2, and C6H2. We have found no unmistakable trace of C8H2. The line profiles display a complex structure suggesting the presence of polyacetylenes in several components of the circumstellar envelope (CSE). We derive total column densities of 2.5x10(17), 3.1x10(17), 2.1x10(17), 9.3x10(16) cm(-2), and less than or similar to 5x10(16) cm(-2) for HCN, C2H2, C4H2, C6H2, and C8H2, respectively. The observations indicate that both the rotational and vibrational temperatures in the innermost CSE depend on the molecule, varying from 100 to 350 K for the rotational temperatures and 100 to 500 K for the vibrational temperatures. Our results support a chemistry in the innermost CSE based on radical-neutral reactions triggered by the intense UV radiation field.Item Characterization Of The HD 17156 Planetary System(2009-08) Barbieri, M.; Alonso, R.; Desidera, S.; Sozzetti, A.; Fiorenzano, A. F. M.; Almenara, J. M.; Cecconi, M.; Claudi, R. U.; Charbonneau, D.; Endl, M.; Granata, V.; Gratton, R.; Laughlin, G.; Loeillet, B.; Exoplanet Amateur, Consortium; Endl, M.Aims. We present data to improve the known parameters of the HD 17156 system (peculiar due to the eccentricity and long orbital period of its transiting planet) and constrain the presence of stellar companions. Methods. Photometric data were acquired for 4 transits, and high precision radial velocity measurements were simultaneously acquired with the SARG spectrograph at TNG for one transit. The template spectra of HD 17156 was used to derive effective temperature, gravity, and metallicity. A fit of the photometric and spectroscopic data was performed to measure the stellar and planetary radii, and the spin-orbit alignment. Planet orbital elements and ephemeris were derived from the fit. Near infrared adaptive optic images were acquired with the AdOpt module of TNG. Results. We found that the star has a radius of R(S) = 1.44 +/- 0.03 R(circle dot) and the planet R(P) = 1.02 +/- 0.08 R(J). The transit ephemeris is T(c) = 2 454 756.73134 +/- 0.00020 + N . 21.21663 +/- 0.00045 BJD. Analysis of the Rossiter-Mclaughlin effect shows that the system is spin orbit aligned with an angle beta = 4.8 degrees +/- 5.3 degrees. The analysis of high resolution images did not reveal any stellar companion with a projected separation between of 150 and 1 000 AU from HD 17156.Item A H I Imaging Survey Of Asymptotic Giant Branch Stars(2013-04) Matthews, L. D.; Le Bertre, T.; Gerard, E.; Johnson, M. C.; Johnson, M. C.We present an imaging study of a sample of eight asymptotic giant branch stars in the H I 21 cm line. Using observations from the Very Large Array, we have unambiguously detected H I emission associated with the extended circumstellar envelopes of six of the targets. The detected H I masses range from M-H (I) approximate to 0.015-0.055 M-circle dot. The Hi morphologies and kinematics are diverse, but in all cases appear to be significantly influenced by the interaction between the circumstellar envelope and the surrounding medium. Four stars (RX Lep, Y UMa, Y CVn, and V1942 Sgr) are surrounded by detached H I shells ranging from 0.36 to 0.76 pc across. We interpret these shells as resulting from material entrained in a stellar outflow being abruptly slowed at a termination shock where it meets the local medium. RX Lep and TX Psc, two stars with moderately high space velocities (V-space > 56 km s(-1)), exhibit extended gaseous wakes (similar to 0.3 and 0.6 pc in the plane of the sky), trailing their motion through space. The other detected star, R Peg, displays a peculiar >horseshoe-shaped> H I morphology with emission extended on scales up to similar to 1.7 pc; in this case, the circumstellar debris may have been distorted by transverse flows in the local interstellar medium. We briefly discuss our new results in the context of the entire sample of evolved stars that has been imaged in H I to date.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 PuZZling Li-Rich Red Giant Associated With NGC 6819(2015-03) Carlberg, Joleen K.; Smith, Verne V.; Cunha, Katia; Majewski, Steven R.; Meszaros, Szabolcs; Shetrone, Matthew; Prieto, Carlos Allende; Bizyaev, Dmitry; Stassun, Keivan G.; Fleming, Scott W.; Zasowski, Gail; Hearty, Fred; Nidever, David L.; Schneider, Donald P.; Holtzman, Jon A.; Frinchaboy, Peter M.; Shetrone, MatthewA Li-rich red giant (RG) star (2M19411367+4003382) recently discovered in the direction of NGC 6819 belongs to the rare subset of Li-rich stars that have not yet evolved to the luminosity bump, an evolutionary stage where models predict Li can be replenished. The currently favored model to explain Li enhancement in first-ascent RGs like 2M19411367+4003382 requires deep mixing into the stellar interior. Testing this model requires a measurement of C-12/C-13, which is possible to obtain from Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectra. However, the Li-rich star also has abnormal asteroseismic properties that call into question its membership in the cluster, even though its radial velocity and location on color-magnitude diagrams are consistent with membership. To address these puzzles, we have measured a wide array of abundances in the Li-rich star and three comparison stars using spectra taken as part of the APOGEE survey to determine the degree of stellar mixing, address the question of membership, and measure the surface gravity. We confirm that the Li-rich star is a RG with the same overall chemistry as the other cluster giants. However, its log g is significantly lower, consistent with the asteroseismology results and suggestive of a very low mass if the star is indeed a cluster member. Regardless of the cluster membership, the C-12/C-13 and C/N ratios of the Li-rich star are consistent with standard first dredge-up, indicating that Li dilution has already occurred, and inconsistent with internal Li enrichment scenarios that require deep mixing.Item Retired A Stars and Their Companions. VII. 18 New Jovian Planets(2011-12) Johnson, J. Aasher; Clanton, Christian; Howard, Andrew W.; Bowler, Brendan P.; Henry, Gregory W.; Marcy, Geoffrey W.; Crepp, Justin R.; Endl, Michael; Cochran, William D.; MacQueen, Phillip J.; Wright, Jason T.; Isaacson, Howard; Endl, Michael; Cochran, William D.; MacQueen, Phillip J.We report the detection of 18 Jovian planets discovered as part of our Doppler survey of subgiant stars at Keck Observatory, with follow-up Doppler and photometric observations made at McDonald and Fairborn Observatories, respectively. The host stars have masses 0.927 <= M(star)/M(circle dot) <= 1.95, radii 2.5 <= R(star)/R(circle dot) <= 8.7, and metallicities -0.46 <= [Fe/H] <= +0.30. The planets have minimum masses 0.9 M(Jup) <= M(P) sin i less than or similar to 13 M(Jup) and semimajor axes a >= 0.76 AU. These detections represent a 50% increase in the number of planets known to orbit stars more massive than 1.5M(circle dot) and provide valuable additional inFormation about the properties of planets around stars more massive than the Sun.