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Orbital periods of cataclysmic variables identified by the SDSS. V. VLT, NTT and Magellan observations of nine equatorial systems
John Southworth, B T Gaensicke, T R Marsh +6
We present VLT and Magellan spectroscopy and NTT photometry of nine faint cataclysmic variables (CVs) which were spectroscopically identified by the SDSS. We measure orbital period…
New Pulsating DB White Dwarf Stars from the Sloan Digital Sky Survey
A. Nitta, S. J. Kleinman, J. Krzesinski +8
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 pulsa…
Two More Candidate AM Canum Venaticorum (AM CVn) Binaries from the Sloan Digital Sky Survey
S. F. Anderson, A. C. Becker, D. Haggard +18
AM CVn systems are a select group of ultracompact binaries with the shortest orbital periods of any known binary subclass; mass-transfer is likely from a low-mass (partially-)degen…
The pulsation modes of the pre-white dwarf PG 1159-035
J. E. S. Costa, S. O. Kepler, D. E. Winget +74
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 1159-0…
Discovery of two new accreting pulsating white dwarf stars
Anjum S. Mukadam, B. T. Gänsicke, P. Szkody +4
We report the discovery of two new accreting pulsating white dwarf stars amongst the cataclysmic variables of the Sloan Digital Sky Survey: SDSSJ074531.91+453829.5 and SDSSJ091945.…
XMM-Newton Observations of the Cataclysmic Variable GW Lib
Eric J. Hilton, Paula Szkody, Anjum Mukadam +4
XMM-Newton observations of the accreting, pulsating white dwarf in the quiescent dwarf nova GW Librae were conducted to determine if the non-radial pulsations present in previous U…
Abell 43: Longest period Planetary Nebula Nucleus variable
J. -E. Solheim, G. Vauclair, A. S. Mukadam +2
Based on 24h high speed photometry of the hybrid PG 1159 star Abell 43, we have detected 6 sighificant pulsations with periods between 2380 s and 6075 s. A short (4h) run on the al…
HST and Optical Observations of Three Pulsating Accreting White Dwarfs in Cataclysmic Variables
Paula Szkody, Anjum Mukadam, Boris T. Gaensicke +8
Ultraviolet observations using the Solar Blind Channel on the Hubble Space Telescope provide light curves and low resolution spectra of three pulsating white dwarfs in the cataclys…
Mean ZZ Ceti pulsation period gauges stellar temperature
Anjum S. Mukadam, M. H. Montgomery, A. Kim +3
The mean pulsation period of ZZ Ceti stars increases with decreasing effective temperature as we traverse from the blue to the red edge of the instability strip. This well-establis…
Measuring the evolution of the most stable optical clock G 117-B15A
S. O. Kepler, J. E. S. Costa, B. G. Castanheira +7
We report our measurement of the rate of change of period with time dP/dt for the 215 s periodicity in the pulsating white dwarf G 117-B15A, the most stable optical clock known. Af…
Ensemble Characteristics of the ZZ Ceti stars
Anjum S. Mukadam, M. H. Montgomery, D. E. Winget +2
We present the observed pulsation spectra of all known non-interacting ZZ Ceti stars (hydrogen atmosphere white dwarf variables; DAVs) and examine changes in their pulsation proper…
Whole Earth Telescope observations of BPM 37093: a seismological test of crystallization theory in white dwarfs
A. Kanaan, A. Nitta, D. E. Winget +3
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 instabilit…
Re-defining the Empirical ZZ Ceti Instability Strip
Anjum S. Mukadam, D. E. Winget, Ted von Hippel +3
We use the new ZZ Ceti stars (hydrogen atmosphere white dwarf variables; DAVs) discovered within the Sloan Digital Sky Survey (Mukadam et al. 2004) to re-define the empirical ZZ Ce…
A Catalog of Spectroscopically Identified White Dwarf Stars in the First Data Release of the Sloan Digital Sky Survey
S. J. Kleinman, Hugh C. Harris, Daniel J. Eisenstein +23
We present the full spectroscopic white dwarf and hot subdwarf sample from the SDSS first data release, DR1. We find 2551 white dwarf stars of various types, 240 hot subdwarf stars…
Observations of the pulsating subdwarf B star Feige 48: Constraints on evolution and companions
M. D. Reed, S. D. Kawaler
Since pulsating subdwarf B (sdBV or EC14026) stars were first discovered (Kilkenny et al, 1997), observational efforts have tried to realize their potential for constraining the in…
ROTSE-III Observations of the Early Afterglow From GRB 030329
D. A. Smith, E. S. Rykoff, C. W. Akerlof +12
Using two identical telescopes at widely separated longitudes, the ROTSE-III network observed decaying emission from the remarkably bright afterglow of GRB 030329. In this report w…
A CCD Time-Series Photometer
R. E. Nather, Anjum. S. Mukadam
We describe a high speed time-series CCD photometer for the prime focus of the 82-in (2.1 m) telescope at McDonald Observatory, and summarize the observational results we have obta…
The Everchanging Pulsating White Dwarf GD358
S. O. Kepler, R. E. Nather, D. E. Winget +43
We report 323 hours of nearly uninterrupted time series photometric observations of the DBV star GD 358 acquired with the Whole Earth Telescope (WET) during May 23rd to June 8th, 2…
Discover of the "missing" mode in HR 1217 by the Whole Earth Telescope
D. W. Kurtz, S. D. Kawaler, R. L. Riddle et al.
HR 1217 is a prototypical rapidly oscillating Ap star that has presented a test to the theory of nonradial stellar pulsation. Prior observations showed a clear pattern of five mode…
Evolutionary Timescale of the DAV G117-B15A: The Most Stable Optical Clock Known
S. O. Kepler, Anjum Mukadam, D. E. Winget +5
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 v…