Search

Your search keyword '"Laird, John B."' showing total 45 results
Start Over Author "Laird, John B."
45 results on '"Laird, John B."'

2. Hunting for the progenitor of SN 1006: High resolution spectroscopic search with the FLAMES instrument

Author

Kerzendorf, Wolfgang E., Schmidt, Brian P., Laird, John B., Podsiadlowski, Philipp, and Bessell, Michael S.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

Type Ia supernovae play a significant role in the evolution of the Universe and have a wide range of applications. It is widely believed that these events are the thermonuclear explosions of carbon-oxygen white dwarfs close to the Chandrasekhar mass (1.38 M\odot). However, CO white dwarfs are born with masses much below the Chandrasekhar limit and thus require mass accretion to become Type Ia supernovae. There are two main scenarios for accretion. First, the merger of two white dwarfs and, second, a stable mass accretion from a companion star. According to predictions, this companion star (also referred to as donor star) survives the explosion and thus should be visible in the center of Type Ia remnants. In this paper we scrutinize the central stars (79 in total) of the SN 1006 remnant to search for the surviving donor star as predicted by this scenario. We find no star consistent with the traditional accretion scenario in SN1006., Comment: 11 pages, accepted by ApJ

Published
2012
Full Text
View/download PDF

3. Rotation and Macroturbulence in Metal-poor Field Red Giant and Red Horizontal Branch Stars

Author

Carney, Bruce W., Gray, David F., Yong, David, Latham, David W., Manset, N., Zelman, R., and Laird, John B.

Subjects
Astrophysics
Abstract

We report the results for rotational velocities, Vrot sin i, and macroturbulence dispersion, zeta(RT), for 12 metal-poor field red giant branch stars and 7 metal-poor field red horizontal branch stars. The results are based on Fourier transform analyses of absorption line profiles from high-resolution (R ~ 120,000), high-S/N (~ 215 per pixel) spectra obtained with the Gecko spectrograph at CFHT. We find that the zeta(RT) values for the metal-poor RGB stars are very similar to those for metal-rich disk giants studied earlier by Gray and his collaborators. Six of the RGB stars have small rotational values, less than 2.0 km/sec, while five show significant rotation, over 3 km/sec. The fraction of rapidly rotating RHB stars is somewhat lower than found among BHB stars. We devise two empirical methods to translate the line-broadening results obtained by Carney et al. (2003, 2008) into Vrot sin i for all the RGB and RHB stars they studied. Binning the RGB stars by luminosity, we find that most metal-poor field RGB stars show no detectable sign, on average, of rotation. However, the most luminous stars, with M(V) <= -1.5, do show net rotation, with mean values of 2 to 4 km/sec, depending on the algorithm employed, and these stars also show signs of radial velocity jitter and mass loss., Comment: accepted for publication in the Astronomical Journal

Published
2007
Full Text
View/download PDF

4. Line Broadening in Field Metal-poor Red Giant and Red Horizontal Branch Stars

Author

Carney, Bruce W., Latham, David W., Stefanik, R. P., and Laird, John B.

Subjects
Astrophysics
Abstract

We report 349 radial velocities for 45 metal-poor field red giant and red horizontal branch stars. We have have identified one new spectroscopic binary, HD 4306, and one possible such system, HD 184711. We also report 57 radial velocities for 11 of the 91 stars reported on previously by Carney et al. (2003). As was found in the previous study, radial velocity "jitter" is present in many of the most luminous stars. Excluding stars showing spectroscopic binary orbital motion, all 7 of the red giants with M(V) <= -2.0 display jitter, as well as 3 of the 14 stars with -2.0 <= M(V) <= -1.4. We have also measured line broadening in all of the new spectra, using synthetic spectra as templates. The most luminous red giants show significant line broadening, as do many of the red horizontal branch stars, and we discuss briefly possible causes., Comment: To appear in the Astronomical Journal

Published
2007
Full Text
View/download PDF

5. A Survey of Proper Motion Stars. XVII. A Deficiency of Binary Stars on Retrograde Galactic Orbits and the Possibility that omega Centauri is Related to the Effect

Author

Carney, Bruce W., Aguilar, Luis A., Latham, David W., and Laird, John B.

Subjects
Astrophysics
Abstract

We find a deficiency of binary stars moving on strongly retrograde Galactic orbits. No binary deficiencies are seen for U or W velocities, however. From theoretical analyses, we rule out preferential disruption of pre-existing binary stars due to encounters with massive perturbers. We also rule out globular clusters as the source of the effect since prograde motions are more likely to create such an effect. We search for star streams and find one possible candidate, but it is not on a retrograde orbit and probably represents the remains of a cluster that has passed too near the Galactic center. Based on a very small number of stars, we find that about the right fraction of stars on retrograde Galactic orbits share some chemical similarities to the cluster omega Cen, suggesting that its parent galaxy could be the explanation., Comment: To appear in the Astronomical Journal (March 2005 issue)

Published
2004
Full Text
View/download PDF

6. Metal-poor Field Blue Stragglers: More Evidence for Mass Transfer

Author

Carney, Bruce W., Latham, David W., and Laird, John B.

Subjects
Astrophysics
Abstract

We report radial velocity studies of five candidate metal-poor field blue stragglers, all known to be deficient in lithium. Four of the five stars are single-lined spectroscopic binaries, with periods ranging from 302 to 840 days, and low orbital eccentricities, in agreement with similar behavior found for other blue straggler candidates by Preston & Sneden (2000) and Carney et al. (2001). The limited data available for lithium abundances indicate that all blue straggler candidates have depleted lithium abundances. Our results show higher values of v(rot) sin i for the binary stars than comparable temperature constant-velocity stars. The orbital periods are too long for tidal effects to now be important, implying that spin-up during mass transfer when the orbital separations and periods were smaller is that cause of the enhanced rotation., Comment: To appear in Astronomical Journal (January 2005 issue)

Published
2004
Full Text
View/download PDF

7. An abundance of small exoplanets around stars with a wide range of metallicities

Author

Buchhave, Lars A., Latham, David W., Johansen, Anders, Bizzarro, Martin, Torres, Guillermo, Rowe, Jason F., Batalha, Natalie M., Borucki, William J., Brugamyer, Erik, Caldwell, Caroline, Bryson, Stephen T., Ciardi, David R., Cochran, William D., Endl, Michael, Esquerdo, Gilbert A., Ford, Eric B., Geary, John C., Gilliland, Ronald L., Hansen, Terese, Isaacson, Howard, Laird, John B., Lucas, Philip W., Marcy, Geoffrey W., Morse, Jon A., Robertson, Paul, Shporer, Avi, Stefanik, Robert P., Still, Martin, and Quinn, Samuel N.

Published
2012
Full Text
View/download PDF

12. Chemical Composition of the Planet-harboring Star TrES-1

Author

Sozzetti, Alessandro, Torres, Guillermo, Carney, Bruce W., Laird, John B., Latham, David W., and Yong, David

Subjects
Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

We present a detailed chemical abundance analysis of the parent star of the transiting extrasolar planet TrES-1. Based on high-resolution Keck HIRES and Hobby-Eberly Telescope HRS spectra, we have determined abundances relative to the Sun for 16 elements

Published
2006
Full Text
View/download PDF

13. A Keck HIRES Doppler Search for Planets Orbiting Metal‐Poor Dwarfs. I. Testing Giant Planet Formation and Migration Scenarios

Author

Laird, John B., Sozzetti, Alessandro, Latham, David W., Carney, Bruce W., Boss, Alan P., Torres, Guillermo, Stefanik, Robert P., and Korzennik, Sylvain G.

Subjects
Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

We describe a high-precision Doppler search for giant planets orbiting a well-defined sample of metal-poor dwarfs in the field. This experiment constitutes a fundamental test of theoretical predictions which will help discriminate between proposed giant planet formation and migration models. We present here details on the survey as well as an overall assessment of the quality of our measurements, making use of the results for the stars that show no significant velocity variation.

Published
2006
Full Text
View/download PDF

14. High-Resolution Spectroscopy of the Transiting Planet Host Star TrES-1

Author

Laird, John B., Yong, David, Torres, Guillermo, Latham, David W., Sozzetti, Alessandro, Carney, Bruce W., Prieto, Carlos Allende, Charbonneau, David, and Brown, Timothy M.

Abstract

We report on a spectroscopic determination of the stellar parameters and chemical abundances for the parent star of the transiting planet TrES-1. Based on a detailed analysis of iron lines in our Keck and HET spectra we derive $T_\mathrm{eff} = 5250\pm 75$ K, $\log g = 4.6\pm 0.2$, and [Fe/H] $= 0.00\pm 0.09$. By measuring the \ion{Ca}{2} activity indicator and by putting useful upper limits on the Li abundance we constrain the age of TrES-1 to be $2.5\pm 1.5$ Gyr. By comparing theoretical stellar evolution models with the observational parameters we obtain $M_\star = 0.89\pm 0.05$ $M_\odot$, and $R_\star = 0.83\pm 0.05$ $R_\odot$. Our improved estimates of the stellar parameters are utilized in a new analysis of the transit photometry of TrES-1 to derive a mass $M_p = 0.76\pm 0.05$ $M_\mathrm{J}$, a radius $R_p = 1.04^{+0.08}_{-0.05}$ $R_\mathrm{J}$, and an inclination $i = 89^\circ.5^{+0.5}_{-1.3}$. The improved planetary mass and radius estimates provide the grounds for new crucial tests of theoretical models of evolution and evaporation of irradiated extrasolar giant planets. Comment: 14 pages, 3 figures, Astrophysical Journal Letters, accepted

Published
2004
Full Text
View/download PDF

17. A NEW SPECTROSCOPIC AND PHOTOMETRIC ANALYSIS OF THE TRANSITING PLANET SYSTEMS TrES-3 AND TrES-4

Author

Sozzetti, Alessandro, primary, Torres, Guillermo, additional, Charbonneau, David, additional, Winn, Joshua N., additional, Korzennik, Sylvain G., additional, Holman, Matthew J., additional, Latham, David W., additional, Laird, John B., additional, Fernandez, José, additional, O'Donovan, Francis T., additional, Mandushev, Georgi, additional, Dunham, Edward, additional, Everett, Mark E., additional, Esquerdo, Gilbert A., additional, Rabus, Markus, additional, Belmonte, Juan A., additional, Deeg, Hans J., additional, Brown, Timothy N., additional, Hidas, Márton G., additional, and Baliber, Nairn, additional

Published
2009
Full Text
View/download PDF

30. The Spectroscopic Orbit of the Planetary Companion Transiting HD 209458

Author

Mazeh, Tsevi, primary, Naef, Dominique, additional, Torres, Guillermo, additional, Latham, David W., additional, Mayor, Michel, additional, Beuzit, Jean-Luc, additional, Brown, Timothy M., additional, Buchhave, Lars, additional, Burnet, Michel, additional, Carney, Bruce W., additional, Charbonneau, David, additional, Drukier, Gordon A., additional, Laird, John B., additional, Pepe, Francesco, additional, Perrier, Christian, additional, Queloz, Didier, additional, Santos, Nuno C., additional, Sivan, Jean-Pierre, additional, Udry, Stéphane, additional, and Zucker, Shay, additional

Published
2000
Full Text
View/download PDF

35. Spectroscopic Binaries in the Halo

Author

Latham, David W., primary, Mazeh, Tsevi, additional, Stefanik, Robert P., additional, Davis, Robert J., additional, Carney, Bruce W., additional, Torres, Guillermo, additional, and Laird, John B., additional

Published
1992
Full Text
View/download PDF

39. A KECK HIRES DOPPLER SEARCH FOR PLANETS ORBITING METAL-POOR DWARFS. II. ON THE FREQUENCY OF GIANT PLANETS IN THE METAL-POOR REGIME

Author

Torres, Guillermo, Stefanik, Robert P., Laird, John B., Sozzetti, Alessandro, Boss, Alan P., Latham, David W., Korzennik, Sylvain G., and Carney, Bruce W.

Subjects
13. Climate action
Abstract

We present an analysis of three years of precision radial velocity (RV) measurements of 160 metal-poor stars observed with HIRES on the Keck 1 telescope. We report on variability and long-term velocity trends for each star in our sample. We identify several long-term, low-amplitude RV variables worthy of followup with direct imaging techniques. We place lower limits on the detectable companion mass as a function of orbital period. Our survey would have detected, with a 99.5% confidence level, over 95% of all companions on low-eccentricity orbits with velocity semiamplitude K 100 m s–1, or Mpsin i 3.0 M J(P/yr)(1/3), for orbital periods P 3 yr. None of the stars in our sample exhibits RV variations compatible with the presence of Jovian planets with periods shorter than the survey duration. The resulting average frequency of gas giants orbiting metal-poor dwarfs with –2.0[Fe/H]–0.6 is fp < 0.67% (at the 1σ confidence level). We examine the implications of this null result in the context of the observed correlation between the rate of occurrence of giant planets and the metallicity of their main-sequence solar-type stellar hosts. By combining our data set with the Fischer & Valenti (2005) uniform sample, we confirm that the likelihood of a star to harbor a planet more massive than Jupiter within 2 AU is a steeply rising function of the host's metallicity. However, the data for stars with –1.0[Fe/H]0.0 are compatible, in a statistical sense, with a constant occurrence rate fp 1%. Our results can usefully inform theoretical studies of the process of giant-planet formation across two orders of magnitude in metallicity.

Catalog

Books, media, physical & digital resources
See catalog results