Todd J. Henry

The CRIRES Search for Planets Around the Lowest-Mass Stars. I. High-Precision Near-Infrared Radial Velocities with an Ammonia Gas Cell (2009)

Bean, Jacob L., Seifahrt, Andreas, Hartman, Henrik, Nilsson, Hampus, Wiedemann, Guenter, Reiners, Ansgar, ...

Radial velocities measured from near-infrared spectra are a potentially powerful tool to search for planets around cool stars and sub-stellar objects. However, no technique currently exists that...

Astrometry - Challenging our Understanding of Stellar Structure and Evolution (2009)

Benedict, G. Fritz, Henry, Todd J., Olling, Rob

Stellar mass plays a central role in our understanding of star formation and aging. Stellar astronomy is largely based on two maps, both dependent on mass, either indirectly or directly: the...

Ground-Based Astrometry 2010-2020 (2009)

Henry, Todd J., Monet, David G., Shankland, Paul D., Reid, Mark J., Van Altena, William, Zacharias, Norbert

We discuss the opportunities for astronomical discovery via ground-based astrometry carried out in the United States during the 2010-2020 decade. We describe imminent scientific breakthroughs that...

Cool Subdwarf Investigations II: Multiplicity (2009)

Jao, Wei-Chun, Mason, Brian D., Hartkopf, William I, Henry, Todd J., Ramos, Stephanie N.

Cool subdwarfs of types K and M are the fainter counterparts of cool main sequence dwarfs that dominate the Galactic population. In this paper we present the results of an optical speckle survey of...

The Solar Neighborhood. XXI. Parallax Results from the CTIOPI 0.9m Program: 20 New Members of the 25 Parsec White Dwarf Sample (2009)

Subasavage, John P., Jao, Wei-Chun, Henry, Todd J., Bergeron, P., Dufour, P., Ianna, Philip A., ...

We present accurate trigonometric parallaxes for 20 new members of the 25 pc white dwarf sample as part of the DENSE project (Discovery and Evalution of Nearby Stellar Embers,...

The High Angular Resolution Multiplicity of Massive Stars (2008)

Mason, Brian D., Hartkopf, William I., Gies, Douglas R., Henry, Todd J., Helsel, John W.

We present the results of a speckle interferometric survey of Galactic massive stars that complements and expands upon a similar survey made over a decade ago. The speckle observations were made with...

Taking the Measure of the Universe : precision astrometry with SIM PlanetQuest (2008)

Unwin, Stephen C., Shao, Michael, Tanner, Angelle M., Allen, Ronald J., Beichman, Charles A., Boboltz, David, ...

Precision astrometry at microarcsecond accuracy has application to a wide range of astrophysical problems. This paper is a study of the science questions that can be addressed using an instrument...

The Solar Neighborhood. XX. Discovery and Characterization of 21 New Nearby White Dwarf Systems (2008)

Subasavage, John P., Henry, Todd J., Bergeron, P., Dufour, P., Hambly, Nigel C.

We present medium resolution spectroscopy and multi-epoch VRI photometry for 21 new nearby (< 50 pc) white dwarf systems brighter than V ~ 17. Of the new systems, ten are DA (including a wide double...

Cool Subdwarf Investigations (CSI) I: New Thoughts for the Spectral Types of K and M Subdwarfs (2008)

Jao, Wei-Chun, Henry, Todd J., Beaulieu, Thomas D., Subasavage, John P.

Using new spectra of 88 K and M-type subdwarfs, we consider novel methods for assigning their spectral types and take steps toward developing a comprehensive spectral sequence for subdwarf types K3.0...

Taking the measure of the universe: precision astrometry with SIM PlanetQuest (2008)

Unwin, Stephen C., Shao, Michael, Tanner, Angelle M., Allen, Ronald J., Beichman, Charles A., Boboltz, David, ...

Precision astrometry at microarcsecond accuracy has applications for a wide range of astrophysical problems. This paper is a study of the science questions that can be addressed using an instrument...

THE VERY LOW MASS COMPONENT OF THE GLIESE 105 SYSTEM (2007)

David A. Golimowski, Todd J. Henry, John E. Krist, Daniel J. Schroeder, Geoffrey W. Marcy, Debra A. Fischer, ...

Multiple-epoch, multicolor images of the astrometric binary Gliese 105A and its very low mass companion Gliese 105C have been obtained using the Hubble Space Telescopes Wide Field Planetary Camera 2...

The Trigonometric Parallax of the Brown Dwarf Planetary System 2MASSW J1207334-393254 (2007)

Gizis, John E., Jao, Wei-Chun, Subasavage, John P., Henry, Todd J.

We have measured a trigonometric parallax to the young brown dwarf 2MASSW J1207334-393254. The distance [54.0 (+3.2,-2.8) pc] and space motion confirm membership in the TW Hydrae Association. The...

Taking the Measure of the Universe: Precision Astrometry with SIM PlanetQuest (2007)

Unwin, Stephen C., Shao, Michael, Tanner, Angelle M., Allen, Ronald J., Beichman, Charles A., Boboltz, David, ...

Precision astrometry at microarcsecond accuracy has application to a wide range of astrophysical problems. This paper is a study of the science questions that can be addressed using an instrument...

The Solar Neighborhood. XIX. Discovery and Characterization of 33 New Nearby White Dwarf Systems (2007)

Subasavage, John P., Henry, Todd J., Bergeron, P., Dufour, P., Hambly, Nigel C., Beaulieu, Thomas D.

We present spectra for 33 previously unclassified white dwarf systems brighter than V = 17 primarily in the southern hemisphere. Of these new systems, 26 are DA, 4 are DC, 2 are DZ, and 1 is DQ. We...

The Solar Neighborhood. XVIII. Discovery of new proper motion stars with 0.40 arcsec yr^-1 > mu >= 0.18 arcsec yr^-1 between declinations -90 degrees and -47 degrees (2007)

Finch, Charlie T., Henry, Todd J., Subasavage, John P., Jao, Wei-Chun, Hambly, Nigel C.

We report 1606 new proper motion systems in the southern sky (declinations -90 degrees to -47 degrees with 0.40 arcsec yr^-1 > mu >= 0.18 yr^-1. This effort is a continuation of the...

Identifying and Characterizing New Nearby White Dwarfs (2006)

Subasavage, John P., Henry, Todd J., Bergeron, Pierre, Dufour, Patrick, Hambly, Nigel C., Beaulieu, Thomas D.

How confident are we that all of the nearest white dwarfs (WDs) have been identified? In an effort to answer this question, we have begun an initiative to identify and characterize new nearby WDs,...

A Re-appraisal of the Habitability of Planets Around M Dwarf Stars (2006)

Tarter, Jill C., Backus, Peter R., Mancinelli, Rocco L., Aurnou, Jonathan M., Backman, Dana E., Basri, Gibor S., ...

Stable, hydrogen-burning, M dwarf stars comprise about 75% of all stars in the Galaxy. They are extremely long-lived and because they are much smaller in mass than the Sun (between 0.5 and 0.08...

The Solar Neighborhood XVII: Parallax Results from the CTIOPI 0.9m Program -- Twenty New Members of the RECONS 10 Parsec Sample (2006)

Henry, Todd J., Jao, Wei-Chun, Subasavage, John P., Beaulieu, Thomas D., Ianna, Philip A., Costa, Edgardo, ...

Astrometric measurements for 25 red dwarf systems are presented, including the first definitive trigonometric parallaxes for 20 systems within 10 pc of the Sun, the horizon of the RECONS sample. The...

Spitzer/IRAC Photometry of M, L, and T Dwarfs (2006)

Patten, Brian M., Stauffer, John R., Burrows, Adam, Marengo, Massimo, Hora, Joseph L., Luhman, Kevin L., ...

We present the results of a program to acquire photometry for eighty-six late-M, L, and T dwarfs using the Infrared Array Camera (IRAC) on the Spitzer Space Telescope. We examine the behavior of...

Two Suns in The Sky: Stellar Multiplicity in Exoplanet Systems (2006)

Raghavan, Deepak, Henry, Todd J., Mason, Brian D., Subasavage, John P., Jao, Wei-Chun, Beaulieu, Thom D., ...

We present results of a reconnaissance for stellar companions to all 131 radial-velocity-detected candidate extrasolar planetary systems known as of July 1, 2005. CPM companions were investigated...

The Solar Neighborhood XV: Discovery of New High Proper Motion Stars with mu >= 0.4"/yr between Declinations -47 degrees and 00 degrees (2005)

Subasavage, John P., Henry, Todd J., Hambly, Nigel C., Brown, Misty A., Jao, Wei-Chun, Finch, Charlie T.

We report the discovery of 152 new high proper motion systems (mu >= 0.4"/yr) in the southern sky (Declination = -47 degrees to 00 degrees) brighter than UKST plate R_{59F} =16.5 via our...

The Solar Neighborhood XIII: Parallax Results from the CTIOPI 0.9-m Program -- Stars with mu >= 1"/year (MOTION Sample) (2005)

Jao, Wei-Chun, Henry, Todd J., Subasavage, John P., Brown, Misty A., Ianna, Philip A., Bartlett, Jennifer L., ...

We present the first set of definitive trigonometric parallaxes and proper motions from the Cerro Tololo Inter-American Observatory Parallax Investigation (CTIOPI). Full astrometric reductions for...

The Solar Neighbourhood XI: The trigonometric parallax of SCR 1845--6357 (2004)

Deacon, Niall R., Hambly, Nigel C., Henry, Todd J., Subasavage, John P., Brown, Misty A., Jao, Wei-Chun

We present a trigonometric parallax for the nearby star SCR1845--6357, an extremely red high proper motion object discovered by Hambly et al. (2004) and identified via accurate photoelectric...

The Solar Neighborhood XII: Discovery of New High Proper Motion Stars with 1.0"/yr > mu >= 0.4"/yr between Declinations -90 degrees and -47 degrees (2004)

Subasavage, John P., Henry, Todd J., Hambly, Nigel C., Brown, Misty A., Jao, Wei-Chun

We report the discovery of 141 new high proper motion systems (1.0"/yr > mu >= 0.4"/yr) in the southern sky (Declination = -90 degrees to -47 degrees) brighter than UKST plate R_{59F} = 16.5 via our...

The Solar Neighborhood X: New Nearby Stars in the Southern Sky and Accurate Photometric Distance Estimates for Red Dwarfs (2004)

Henry, Todd J., Subasavage, John P., Brown, Misty A., Beaulieu, Thomas D., Jao, Wei-Chun, Hambly, Nigel C.

Photometric VRI and spectroscopic (6000-9500 A) observations of high proper motion stars discovered during the first phase of the SuperCOSMOS RECONS (SCR) search are used to estimate accurate...

The Solar Neighborhood VI: New Southern Stars Identified by Optical Spectroscopy (2001)

Henry, Todd J., Walkowicz, Lucianne M., Barto, Todd C., Golimowski, David A.

Broadband optical spectra are presented for 34 known and candidate nearby stars in the southern sky. Spectral types are determined using a new method that compares the entire spectrum with spectra of...

Studies of multiple stellar systems - IV. The triple-lined spectroscopic system Gliese 644 (2001)

Mazeh, Tsevi, Latham, David W., Goldberg, Elad, Torres, Guillermo, Stefanik, Robert P., Henry, Todd J., ...

We present a radial-velocity study of the triple-lined system Gliese 644 and derive spectroscopic elements for the inner and outer orbits with periods of 2.9655 and 627 days. We also utilize old...

The Very Low Mass Component of the Gliese 105 System (2000)

Golimowski, David A., Henry, Todd J., Krist, John E., Schroeder, Daniel J., Marcy, Geoffrey W., Fischer, Debra A., ...

Multiple-epoch, multicolor images of the astrometric binary Gliese 105A and its very low mass companion Gliese 105C have been obtained using the Hubble Space Telescope's Wide Field Planetary Camera 2...

Interferometric Astrometry of the Low-mass Binary Gl 791.2 (= HU Del) Using Hubble Space Telescope Fine Guidance Sensor 3: Parallax and Component Masses (2000)

Benedict, G. Fritz, McArthur, Barbara E., Franz, Otto G., Wasserman, Lawrence H., Henry, Todd J.

With fourteen epochs of fringe tracking data spanning 1.7y from Fine Guidance Sensor 3 we have obtained a parallax (pi_abs=113.1 +- 0.3 mas) and perturbation orbit for Gl 791.2A. Contemporaneous...

High-Resolution Spectroscopy of Some Very Active Southern Stars (1998)

Soderblom, David R., King, Jeremy R., Henry, Todd J.

We have obtained high-resolution echelle spectra of 18 solar-type stars that an earlier survey showed to have very high levels of Ca II H and K emission. Most of these stars belong to close binary...