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Full-Text Articles in Physical Sciences and Mathematics
A Spitzer White Dwarf Infrared Survey, F. Mullally, Ted Von Hippel, Et Al.
A Spitzer White Dwarf Infrared Survey, F. Mullally, Ted Von Hippel, Et Al.
Publications
We present mid-infrared photometry of 124 white dwarf stars with the Spitzer Space Telescope. Objects were observed simultaneously at 4.5 and 8.0 μm with sensitivities better than 0.1 mJy. This data set can be used to test models of white dwarf atmospheres in a new wavelength regime, as well as to search for planetary companions and debris disks.
The New Class Of Dusty Daz White Dwarfs, Ted Von Hippel, Et Al.
The New Class Of Dusty Daz White Dwarfs, Ted Von Hippel, Et Al.
Publications
Our mid-infrared survey of 124 white dwarfs with the Spitzer Space Telescope and the IRAC imager has revealed an infrared excess associated with the white dwarf WD 2115-560 naturally explained by circumstellar dust. This object is the fourth white dwarf observed to have circumstellar dust. All four are DAZ white dwarfs, i.e., they have both photospheric Balmer lines and photospheric metal lines. We discuss these four objects as a class, which we abbreviate "DAZd," where the "d" stands for "dust." Using an optically thick, geometrically thin disk model analogous to Saturn's rings, we find that the inner disk edges are …
Lp133-373 A New Chromospherically Active Eclipsing Dme Binary With A Distant, Cool White Dwarf Companion, T. R. Vaccaro, T. D. Oswalt, M. Rudkin, Adela Kawka, Stephane Vennes, Et Al.
Lp133-373 A New Chromospherically Active Eclipsing Dme Binary With A Distant, Cool White Dwarf Companion, T. R. Vaccaro, T. D. Oswalt, M. Rudkin, Adela Kawka, Stephane Vennes, Et Al.
Publications
We report the discovery of the partially eclipsing binary LP 133-373. Nearly identical eclipses along with observed photometric colors and spectroscopy indicate that it is a pair of chromospherically active dM4 stars in a circular 1.6 day orbit. Light and velocity curve modeling to our differential photometry and velocity data show that each star has a mass and radius of 0.340 ± 0.014 M☉ and 0.33 ± 0.02 R☉. The binary is itself part of a common proper motion pair with LP 133-374, a cool DC or possible DA white dwarf with a mass of 0.49-0.82 M☉, …
Lp 133-373: A New Chromospherically Active Eclipsing Dme Binary With A Distant, Cool White Dwarf Companion, T. R. Vaccaro, M. Rudkin, A. Kawka, S. Vennes, Terry D. Oswalt, Et Al.
Lp 133-373: A New Chromospherically Active Eclipsing Dme Binary With A Distant, Cool White Dwarf Companion, T. R. Vaccaro, M. Rudkin, A. Kawka, S. Vennes, Terry D. Oswalt, Et Al.
Publications
We report the discovery of the partially eclipsing binary LP 133-373. Nearly identical eclipses along with observed photometric colors and spectroscopy indicate that it is a pair of chromospherically active dM4 stars in a circular 1.6 day orbit. Light and velocity curve modeling to our differential photometry and velocity data show that each star has a mass and radius of 0:340 ± 0:014 MꙨ and 0:33 ± 0:02 RꙨ. The binary is itself part of a common proper motion pair with LP 133-374, a cool DC or possible DA white dwarf with a mass of 0.49Y0.82 M …
Discovery Of Photospheric Calcium Line-Strength Variations In The Dazd White Dwarf G29-38, Ted Von Hippel, Susan E. Thompson
Discovery Of Photospheric Calcium Line-Strength Variations In The Dazd White Dwarf G29-38, Ted Von Hippel, Susan E. Thompson
Publications
Metals in the photospheres of white dwarfs with Teff between 12,000 and 25,000 K should gravitationally settle out of these atmospheres in 1 ̶ 2 weeks. Temporal variations in the line strengths of these metals could provide a direct measurement of episodic metal accretion. Using archival VLT and Keck spectroscopy, we find evidence that the DAZd white dwarf G29-38 shows significant changes in its Ca П K line strength. At the two best-observed epochs, we find that the Ca line equivalent width (EW) = 165 ̶ 4 mǺ (in 1996.885) and 280 ± 8 mǺ (in 1999.653), which is …
New Techniques To Determine Ages Of Open Clusters Using White Dwarfs, E. J. Jeffery, Ted Von Hippel, Et Al.
New Techniques To Determine Ages Of Open Clusters Using White Dwarfs, E. J. Jeffery, Ted Von Hippel, Et Al.
Publications
Currently there are two main techniques for independently determining the ages of stellar populations: main-sequence evolution theory (via cluster isochrones) and white dwarf cooling theory. Open clusters provide the ideal environment for the calibration of these two clocks. Because current techniques to derive cluster ages from white dwarfs are observationally challenging, we discuss the feasibility of determining white dwarf ages from the brighter white dwarfs alone. This would eliminate the requirement of observing the coolest (i.e., faintest) white dwarfs. We discuss our method for testing this new idea, as well as the required photometric precision and prior constraints on metallicity, …