A multi-site campaign to measure solar-like oscillations in Procyon. II. Mode frequencies (2010)
Bedding, T. R., Kjeldsen, H., Campante, T. L., Appourchaux, T., Bonanno, A., Chaplin, W. J., ...
We have analyzed data from a multi-site campaign to observe oscillations in the F5 star Procyon. The data consist of high-precision velocities that we obtained over more than three weeks with eleven...
The asteroseismic potential of Kepler: first results for solar-type stars (2010)
Chaplin, W. J., Appourchaux, T., Elsworth, Y., Garcia, R. A., Houdek, G., Karoff, C., ...
We present preliminary asteroseismic results from Kepler on three G-type stars. The observations, made at one-minute cadence during the first 33.5d of science operations, reveal high signal-to-noise...
Kepler Asteroseismology Program: Introduction and First Results (2009)
Gilliland, Ronald L., Brown, T. M., Christensen-Dalsgaard, J., Kjeldsen, H., Aerts, C., Appourchaux, T., ...
Asteroseismology involves probing the interiors of stars and quantifying their global properties, such as radius and age, through observationsof normal modes of oscillation. The technical...
Karoff, C., Metcalfe, T. S., Chaplin, W. J., Frandsen, S., Grundahl, F., Kjeldsen, H., ...
Due to its unique long-term coverage and high photometric precision, observations from the Kepler asteroseismic investigation will provide us with the possibility to sound stellar cycles in a number...
Mode identification in rapidly rotating stars (2009)
Reese, D.R., Thompson, M.J., MacGregor, K.B., Jackson, S., Skumanich, A., Metcalfe, T.S.
Context: Recent calculations of pulsation modes in rapidly rotating polytropic models and models based on the Self-Consistent Field method have shown that the frequency spectrum of low degree...
Activity Cycles of Southern Asteroseismic Targets (2009)
Metcalfe, T. S., Judge, P. G., Basu, S., Henry, T. J., Soderblom, D. R., Knoelker, M., ...
The Mount Wilson Ca HK survey revealed magnetic activity variations in a large sample of solar-type stars with timescales ranging from 2.5 to 25 years. This broad range of cycle periods is thought to...
Sounding stellar cycles with Kepler - I. Strategy for selecting targets (2009)
Karoff, C., Metcalfe, T. S., Chaplin, W. J., Elsworth, Y., Kjeldsen, H., Arentoft, T., ...
The long-term monitoring and high photometric precision of the Kepler satellite will provide a unique opportunity to sound the stellar cycles of many solar-type stars using asteroseismology. This can...
A Stellar Model-fitting Pipeline for Solar-like Oscillations (2009)
Metcalfe, T. S., Creevey, O. L., Christensen-Dalsgaard, J.
Over the past two decades, helioseismology has revolutionized our understanding of the interior structure and dynamics of the Sun. Asteroseismology will soon place this knowledge into a broader...
Mode identification in rapidly rotating stars (2009)
Reese, D. R., Thompson, M. J., MacGregor, K. B., Jackson, S., Skumanich, A., Metcalfe, T. S.
Context: Recent calculations of pulsation modes in rapidly rotating polytropic models and models based on the Self-Consistent Field method (MacGregor et al. 2007) have shown that the frequency...
Pulsation modes in rapidly rotating stellar models based on the Self-Consistent Field method (2009)
Reese, D. R., MacGregor, K. B., Jackson, S., Skumanich, A., Metcalfe, T. S.
Context: New observational means such as the space missions CoRoT and Kepler and ground-based networks are and will be collecting stellar pulsation data with unprecedented accuracy. A significant...
Low-Energy Astrophysics: Stimulating the Reduction of Energy Consumption in the Next Decade (2009)
Marshall, P. J., Bennert, N., Rykoff, E. S., Shen, K. J., Steinfadt, J. D. R., Fregeau, J., ...
In this paper we address the consumption of energy by astronomers while performing their professional duties. Although we find that astronomy uses a negligible fraction of the US energy budget, the...
A Stellar Model-fitting Pipeline for Asteroseismic Data from the Kepler Mission (2009)
Metcalfe, T. S., Creevey, O. L., Christensen-Dalsgaard, J.
Over the past two decades, helioseismology has revolutionized our understanding of the interior structure and dynamics of the Sun. Asteroseismology will soon place this knowledge into a broader...
Temporal Variability of Stars and Stellar Systems (2009)
Lister, T. A., Metcalfe, T. S., Brown, T. M., Street, R. A.
Although the Sun is our closest star by many orders of magnitude and despite having sunspot records stretching back to ancient China, our knowledge of the Sun's magnetic field is far from complete....
New Pulsating DB White Dwarf Stars from the Sloan Digital Sky Survey (2008)
Nitta, A., Kleinman, S. J., Krzesinski, J., Kepler, S. O., Metcalfe, T. S., Mukadam, Anjum S., ...
We are searching for new He atmosphere white dwarf pulsators (DBVs) based on the newly found white dwarf stars from the spectra obtained by the Sloan Digital Sky Survey. DBVs pulsate at hotter...
Sullivan, WET Collaboration: D. J., Metcalfe, T. S., O'Donoghue, D., Winget, D. E., Kilkenny, D., Van Wyk, F., ...
We present the analysis of a total of 177h of high-quality optical time-series photometry of the helium atmosphere pulsating white dwarf (DBV) EC 20058-5234. The bulk of the observations (135h) were...
The pulsation modes of the pre-white dwarf PG 1159-035 (2008)
Costa, J. E. S., Kepler, S. O., Winget, D. E., O'Brien, M. S., Kawaler, S. D., Costa, A. F. M., ...
Context. PG 1159-035, a pre-white dwarf with T_(eff) ≃ 140 000 K, is the prototype of both two classes: the PG 1159 spectroscopic class and the DOV pulsating class. Previous studies of PG 1159-035...
The pulsation modes of the pre-white dwarf PG 1159-035 (2007)
Costa, J. E. S., Kepler, S. O., Winget, D. E., O'Brien, M. S., Kawaler, S. D., Costa, A. F. M., ...
PG 1159-035, a pre-white dwarf with T_eff=140,000 K, is the prototype of both two classes: the PG1159 spectroscopic class and the DOV pulsating class. Previous studies of PG 1159-035 photometric data...
Oscillations in Procyon A: First results from a multi-site campaign (2007)
Hekker, S., Arentoft, T., Kjeldsen, H., Bedding, T. R., Christensen-Dalsgaard, J., Reffert, S., ...
Procyon A is a bright F5IV star in a binary system. Although the distance, mass and angular diameter of this star are all known with high precision, the exact evolutionary state is still unclear....
Perez, J. M. Gonzalez, Metcalfe, T. S.
We present a new method that investigates the evolutionary history of the pulsating DB white dwarf GD358 using asteroseismology. This is done considering the internal C/O profile, which describes the...
Asteroseismic Signatures of Small Convective Cores (2007)
We present an analytical study of the effect of small convective cores on the oscillations of solar-like pulsators. Based on an asymptotic analysis of the wave equation near the center of the star,...
Asteroseismic Signatures of Stellar Magnetic Activity Cycles (2007)
Metcalfe, T. S., Dziembowski, W. A., Judge, P. G., Snow, M.
Observations of stellar activity cycles provide an opportunity to study magnetic dynamos under many different physical conditions. Space-based asteroseismology missions will soon yield useful...
MacGregor, K. B., Jackson, Stephen, Skumanich, Andrew, Metcalfe, T. S.
We conduct a systematic examination of the properties of models for chemically homogeneous, differentially rotating, main-sequence stars of mass 1-2 M_sun. The models were constructed using a code...
Creevey, O. L., Monteiro, M. J. P. F. G., Metcalfe, T. S., Brown, T. M., Jiménez-Reyes, S. J., Belmonte, J. A.
How important is an independent diameter measurement for the determination of stellar parameters of solar-type stars? When coupled with seismic observables, how well can we determine the stellar...
Calibrating the Solar Dynamo: Magnetic Activity Cycles of Southern Sun-like Stars (2006)
Metcalfe, T. S., Henry, T. J., Knolker, M., Soderblom, D. R.
The solar magnetic activity cycle is responsible for periodic episodes of severe space weather, which can perturb satellite orbits, interfere with communications systems, and bring down power grids....
The White Dwarf Luminosity Function from SDSS Imaging Data (2005)
Harris, Hugh C., Munn, Jeffrey A., Kilic, Mukremin, Liebert, James, Williams, Kurtis A., Von Hippel, Ted, ...
A sample of white dwarfs is selected from SDSS DR3 imaging data using their reduced proper motions, based on improved proper motions from SDSS plus USNO-B combined data. Numerous SDSS and followup...
An asteroseismic test of diffusion theory in white dwarfs (2005)
Metcalfe, T. S., Nather, R. E., Watson, T. K., Kim, S. -L., Park, B. -G., Handler, G.
The helium-atmosphere (DB) white dwarfs are commonly thought to be the descendants of the hotter PG1159 stars, which initially have uniform He/C/O atmospheres. In this evolutionary scenario,...
Kanaan, A., Nitta, A., Winget, D.E., Kepler, S.O., Montgomery, M.H., Metcalfe, T.S., ...
The definitive version of this paper is available from www.aanda.org
Kanaan, A., Nitta, A., Winget, D. E., Kepler, S. O., Montgomery, M. H., Metcalfe, T. S.
BPM 37093 is the only hydrogen-atmosphere white dwarf currently known which has sufficient mass (~ 1.1 M_sun) to theoretically crystallize while still inside the ZZ Ceti instability strip (T_eff ~...
The White Dwarf Luminosity Function: The Shape of Things to Come (2004)
Von Hippel, T., Kilic, M., Munn, J., Harris, H., Williams, K., Liebert, J., ...
We describe a new survey for cool white dwarfs that supplements Sloan Digital Sky Survey photometry with USNO proper motions and follow-up spectroscopy. To date we have discovered and...
The Crystal Method: Asteroseismology of BPM 37093 (2004)
Metcalfe, T. S., Montgomery, M. H., Kanaan, A.
More than 40 years have passed since Ed Salpeter and others predicted that the carbon/oxygen cores of the coolest white dwarf stars in our Galaxy will theoretically crystallize. This effect has a...
Asteroseismology of Sun-like Stars - A Proposal (2004)
Metcalfe, T. S., Brown, T. M., Christensen-Dalsgaard, J.
In the past decade, helioseismology has revolutionized our understanding of the interior structure of the Sun. In the next decade, asteroseismology will place this knowledge into context, by...
Metcalfe, T. S., Montgomery, M. H., Kanaan, A.
It was predicted more than 40 years ago that the cores of the coolest white dwarf stars should eventually crystallize. This effect is one of the largest sources of uncertainty in white dwarf cooling...
Winget, D. E., Sullivan, D. J., Metcalfe, T. S., Kawaler, S. D., Montgomery, M. H.
We demonstrate that plasmon neutrinos are the dominant form of energy loss in model white dwarf stars down to T_eff ~ 25,000 K, depending on the stellar mass. The lower end of this range overlaps the...
Probing the core and envelope structure of DBV white dwarfs (2003)
Metcalfe, T. S., Montgomery, M. H., Kawaler, S. D.
We investigate the global pulsation properties of DBV white dwarf models that include both the double-layered envelope structure expected from time-dependent diffusion calculations, as well as a...
The core/envelope symmetry in pulsating stars (2003)
Montgomery, M. H., Metcalfe, T. S., Winget, D. E.
We demonstrate that there is an inherent symmetry in the way high-overtone stellar pulsations sample the core and the envelope, which can potentially lead to an ambiguity in the asteroseismologically...
Metcalfe, T. S., Charbonneau, P.
Genetic algorithms are a class of heuristic search techniques that apply basic evolutionary operators in a computational setting. We have designed a fully parallel and distributed hardware/software...
We have identified seven independent pulsation modes in the helium-atmosphere variable (DBV) white dwarf star CBS 114, based on 65 hours of time-resolved CCD photometry from the 0.75-m telescope at...
Handler, G., Metcalfe, T. S., Wood, M. A.
We have acquired 65 h of single-site time-resolved CCD photometry of the pulsating DB white dwarf star CBS 114 and 62 h of two-site high-speed CCD photometry of another DBV, PG 1456+103. The...
Measuring ^{12}C(&alpha,&gamma)^{16}O from White Dwarf Asteroseismology (2002)
Metcalfe, T. S., Salaris, M., Winget, D. E.
During helium burning in the core of a red giant, the relative rates of the 3&alpha and ^{12}C(&alpha,&gamma)^{16}O reactions largely determine the final ratio of carbon to oxygen in the resulting...
Constraints on 12C(alpha,gamma)16O from White Dwarf Seismology (2001)
Metcalfe, T. S., Salaris, M., Winget, D. E.
For many years, astronomers have promised that the study of pulsating white dwarfs would ultimately lead to useful information about the physics of matter under extreme conditions of temperature and...
Preliminary Constraints on 12C(alpha,gamma)16O from White Dwarf Seismology (2001)
Metcalfe, T. S., Winget, D. E., Charbonneau, P.
For many years, astronomers have promised that the study of pulsating white dwarfs would ultimately lead to useful information about the physics of matter under extreme conditions of temperature and...
The effect of 3-He diffusion on the pulsational spectra of DBV models (2000)
Montgomery, M. H., Metcalfe, T. S., Winget, D. E.
We consider envelopes of DB white dwarfs which are not composed of pure 4-He, but rather a mixture of 3-He and 4-He. Given this assumption, the same diffusive processes which produce a relatively...
Genetic-Algorithm-based Asteroseismological Analysis of the DBV White Dwarf GD 358 (2000)
Metcalfe, T. S., Nather, R. E., Winget, D. E.
White dwarf asteroseismology offers the opportunity to probe the structure and composition of stellar objects governed by relatively simple physical principles. The observational requirements of...
Evolutionary Timescale of the DAV G117-B15A: The Most Stable Optical Clock Known (2000)
Kepler, S. O., Mukadam, Anjum, Winget, D. E., Nather, R. E., Metcalfe, T. S., Reed, M. D., ...
We observe G117-B15A, the most precise optical clock known, to measure the rate of change of the main pulsation period of this blue-edge DAV white dwarf. Even though the obtained value is only within...
The Asteroseismology Metacomputer (1999)
Metcalfe, T. S., Nather, R. E.
We have developed a specialized computational instrument for fitting models of pulsating white dwarfs to observations made with the Whole Earth Telescope. This metacomputer makes use of inexpensive...
The White Dwarf Luminosity Function from Sloan Digital Sky Survey Imaging Data (1998)
Harris, Hugh C., Munn, Jeffrey A., Kilic, Mukremin, Liebert, James, Kleinman, S. J., Metcalfe, T. S., ...
A sample of white dwarfs is selected from the Sloan Digital Sky Survey (SDSS) Data Release 3 using their reduced proper motions, based on improved proper motions from combined SDSS and USNO-B data....
The Orbital and Absolute Magnitude Distributions of Main Belt Asteroids (1998)
We have developed a model-independent analytical method for debiasing the four-dimensional (a,e,i,H) distribution obtained in any asteroid observation program and have applied the technique to...