Search Publications
A Hubble Space Telescope Survey of Extended [O III] λ5007 Emission in a Far-Infrared Selected Sample of Seyfert Galaxies: Observations
Hutchings, J. B.; Schmitt, H. R.; Donley, J. L. +2 more
We present a Hubble Space Telescope (HST) survey of extended [O III] emission for a sample of 60 Seyfert galaxies (22 Seyfert 1 galaxies and 38 Seyfert 2 galaxies), selected based on their far-infrared properties. The observations for 42 of these galaxies were done in a snapshot survey with WFPC2. The remaining 18 were obtained from the HST archiv…
New Members of the TW Hydrae Association, β Pictoris Moving Group, and Tucana/Horologium Association
Zuckerman, B.; Song, Inseok; Bessell, M. S.
We have identified five new members of the TW Hydrae association (TWA), 11 new members of the β Pic moving group, and 11 new Tucana/Horologium association members. These are the three youngest (<~30 Myr) known kinematic stellar groups near the Earth. Newly identified β Pic group members are located mostly in the northern hemisphere, and they ha…
Solar active regions: SOHO/CDS and TRACE observations of quiescent coronal loops
Mason, H. E.; Del Zanna, G.
This study focuses on the diagnostic capabilities of the TRACE and SOHO-CDS instruments to describe the physical characteristics of quiescent solar active regions. In particular we concentrate on the 1 MK loops, best seen in the TRACE EUV 173 Å passband. These are high-lying structures which can remain stable over timescales of hours to days. We p…
The age, life expectancy, and space density of Post Common Envelope Binaries
Gänsicke, B. T.; Schreiber, M. R.
We present a sample of 30 well observed Post Common Envelope Binaries (PCEBs). Deriving the cooling age of the white dwarfs, we show that the PCEB population is dominated by young systems. Having calculated the orbital evolution of the systems under the assumption of two different prescriptions for the angular momentum loss, we find that most of t…
Star cluster formation and disruption time-scales - I. An empirical determination of the disruption time of star clusters in four galaxies
Lamers, H. J. G. L. M.; Boutloukos, S. G.
We have derived the disruption times of star clusters from cluster samples of four galaxies, M51, M33, the Small Magellanic Cloud (SMC) and the solar neighbourhood. If the disruption time of clusters in a galaxy depends only on their initial mass as tdis(yr) =t4dis(Mcl/104 Msolar)
Hubble Space Telescope Observations of Binary Very Low Mass Stars and Brown Dwarfs
Kirkpatrick, J. Davy; Burgasser, Adam J.; Gizis, John E. +4 more
We present analysis of Hubble Space Telescope (HST) images of 82 nearby field late M and L dwarfs. We resolve 13 of these systems into double M/L dwarf systems and identify an additional possible binary. Combined with previous observations of 20 L dwarfs, we derive an observed binary fraction for ultracool dwarfs of 17+4-3%, …
Multiwavelength Observations of Flares on AD Leonis
Hawley, Suzanne L.; Valenti, Jeff A.; Johns-Krull, Christopher M. +9 more
We report results from a multiwavelength observing campaign conducted during 2000 March on the flare star AD Leo. Simultaneous data were obtained from several ground- and space-based observatories, including observations of eight sizable flares. We discuss the correlation of line and continuum emission in the optical and ultraviolet wavelength reg…
Spectral Irradiance Calibration in the Infrared. XIII. ``Supertemplates'' and On-Orbit Calibrators for the SIRTF Infrared Array Camera
Megeath, S. T.; Stauffer, John; Cohen, Martin +2 more
We describe the technique that will be used to develop a set of on-orbit calibrators for the Infrared Array Camera (IRAC) and demonstrate the validity of the method for stars with spectral types either K0-M0 III or A0-A5 V. For application to SIRTF, the approach is intended to operate with all available optical, near-infrared (NIR), and mid-infrar…
Acceleration of the solar wind as a result of the reconnection of open magnetic flux with coronal loops
Fisk, L. A.
There are compelling observations of a clear anticorrelation between solar wind flow speed and coronal electron temperature, as determined from solar wind ionic charge states. A simple theory is presented which can account for these observations, including the functional form of the correlation: Solar wind flow speed squared varies essentially lin…
Locating the Launching Region of T Tauri Winds: The Case of DG Tauri
Li, Zhi-Yun; Blandford, Roger D.; Krasnopolsky, Ruben +1 more
It is widely believed that T Tauri winds are driven magnetocentrifugally from accretion disks close to the central stars. The exact launching conditions are uncertain. We show that a general relation exists between the poloidal and toroidal velocity components of a magnetocentrifugal wind at large distances and the rotation rate of the launching s…