A rival for Babcock's star: the extreme 30-kG variable magnetic field in the Ap star HD 75049 (2009)
Elkin, V. G., Mathys, G., Kurtz, D. W., Hubrig, S., Freyhammer, L. M.
The extraordinary magnetic Ap star HD75049 has been studied with data obtained with the ESO VLT and 2.2-m telescopes. Direct measurements reveal that the magnetic field modulus at maximum reaches...
A 3-D study of the photosphere of HD99563: I. Pulsation analysis (2009)
Freyhammer, L. M., Kurtz, D. W., Elkin, V. G., Mathys, G., Savanov, I., Zima, W., ...
We have used high-speed spectroscopy of the rapidly oscillating Ap (roAp) star HD99563 to study the pulsation amplitude and phase behaviour of elements in its stratified atmosphere over one 2.91-d...
Bruntt, H., Kurtz, D. W., Cunha, M. S., Brandao, I. M., Handler, G., Bedding, T. R., ...
We present a detailed study of the pulsation of alpha Circini, the brightest of the rapidly oscillating Ap stars. We have obtained 84 days of high-precision photometry from four runs with the star...
Hubrig, S., Mathys, G., Kurtz, D. W., Schoeller, M., Elkin, V. G., Henrichs, H. F.
We obtained thirteen spectropolarimetric observations of the strongly magnetic rapidly oscillating Ap star HD154708 over three months with the multi-mode instrument FORS1, installed at the 8-m Kueyen...
Interferometric and seismic constraints on the roAp star alpha Cir (2008)
Brandao, I. M., Bruntt, H., Cunha, M., Kurtz, D. W.
We present new constraints on the rapidly oscillating Ap star alpha Cir, derived from a combination of interferometric and photometric data obtained with the Sydney University Stellar Interferometer...
A search for rapid pulsations in the magnetic cool chemically peculiar star HD3980 (2008)
Elkin, V. G., Kurtz, D. W., Freyhammer, L. M., Hubrig, S., Mathys, G.
The Ap star HD3980 appears to be a promising roAp candidate based on its fundamental parameters, leading us to search for rapid pulsations with the VLT UV-Visual Echelle Spectrograph (UVES). A...
On the spectroscopic nature of the cool evolved Am star HD151878 (2008)
Freyhammer, L. M., Elkin, V. G., Kurtz, D. W.
Recently, Tiwari, Chaubey, & Pandey (2007) detected the bright component of the visual binary HD151878 to exhibit rapid photometric oscillations through a Johnson B filter with a period of 6 min...
Discovery of 17 new sharp-lined Ap stars with magnetically resolved lines (2008)
Freyhammer, L. M., Elkin, V. G., Kurtz, D. W., Mathys, G., Martinez, P.
Chemically peculiar A stars (Ap) are extreme examples of the interaction of atomic element diffusion processes with magnetic fields in stellar atmospheres. The rapidly oscillating Ap stars provide a...
The fundamental parameters of the roAp star α Circini (2008)
Bruntt, H., North, J. R., Cunha, M., Brandão, I. M., Elkin, V. G., Kurtz, D. W., ...
We have used the Sydney University Stellar Interferometer to measure the angular diameter of α Cir. This is the first detailed interferometric study of a rapidly oscillating A (roAp) star, α Cir...
The Current Status of Asteroseismology (2008)
Aerts, C., Christensen-Dalsgaard, J., Cunha, M., Kurtz, D. W.
Stellar evolution, a fundamental bedrock of modern astrophysics, is driven by the physical processes in stellar interiors. While we understand these processes in general terms, we lack some important...
The fundamental parameters of the roAp star alpha Circini (2008)
Bruntt, H., North, J. R., Cunha, M., Brandao, I. M., Elkin, V. G., Kurtz, D. W., ...
We have used the Sydney University Stellar Interferometer (SUSI) to measure the angular diameter of alpha Cir. This is the first detailed interferometric study of a rapidly oscillating A (roAp) star,...
Parallaxes of L and T dwarfs (2008)
D. W. Kurtz, G. E. Bromage, R. L. Smart
Abstract. We discuss a new program to measure the parallaxes of a number of L and T dwarfs, objects that bridge the gap between M dwarfs and planets. This pilot project tests the feasibility of using...
doi:10.1017/S1743921305001420 The black-drop effect explained (2008)
D. W. Kurtz, Jay M. Pasachoff, Glenn Schneider, Leon Golub
Abstract. The black-drop effect bedeviled attempts to determine the Astronomical Unit from the time of the transit of Venus of 1761, until dynamical determinations of the AU obviated the need for...
A search for rapid pulsations among 9 luminous Ap stars (2008)
Freyhammer, L. M., Kurtz, D. W., Cunha, M. S., Mathys, G., Elkin, V. G., Riley, J. D.
The rapidly oscillating Ap stars are of importance for studying the atmospheric structure of stars where the process of chemical element diffusion is significant. We have performed a survey for rapid...
Gonzalez, J. F., Hubrig, S., Kurtz, D. W., Elkin, V., Savanov, I.
Asteroseismology has the potential to provide new insights into the physics of stellar interiors. We have obtained UVES high time resolution observations of the delta Scuti star HD21190 and of the Ap...
Broadband Linear Polarisation Of Cp Stars (2007)
Sky Survey, S. Bagnulo, M. J. Stift, F. Leone, D. W. Kurtz, P. Martinez
. In recent years, an interesting new technique for the diagnosis of stellar magnetic fields has been developed, which employs the frequency integrated linear polarisation signal over a spectral...
Asteroseismology and Interferometry (2007)
Cunha, M. S., Aerts, C., Christensen-Dalsgaard, J., Baglin, A., Bigot, L., Brown, T. M., ...
Asteroseismology provides us with a unique opportunity to improve our understanding of stellar structure and evolution. Recent developments, including the first systematic studies of solar-like...
Joshi, Santosh, Mary, D. L., Martinez, Peter, Kurtz, D. W., Girish, V., Seetha, S., ...
To search photometric variability in chemically peculiar A type stars in the northern hemisphere. High-speed photometric observations of Ap and Am star candidates have been carried out from ARIES...
New measurements of magnetic fields of roAp stars with FORS1 at the VLT (2003)
Hubrig, S., Szeifert, T., Schoeller, M., Mathys, G., Kurtz, D. W.
Magnetic fields play a key role in the pulsations of rapidly oscillating Ap (roAp) stars since they are a necessary ingredient of all pulsation excitation mechanisms proposed so far. This implies...
Hubrig, S., Kurtz, D. W., Bagnulo, S., Szeifert, T., Schoeller, M., Mathys, G., ...
With FORS1 at the VLT we have tried for the first time to measure the magnetic field variation over the pulsation cycle in six roAp stars to begin the study of how the magnetic field and pulsation...
Discovery of unusual pulsations in the cool, evolved Am stars HD 98851 and HD 102480 (2003)
Joshi, Santosh, Girish, V., Sagar, R., Kurtz, D. W., Martinez, P., Kumar, B., ...
The chemically peculiar (CP) stars HD 98851 and HD 102480 have been discovered to be unusual pulsators during the ``Naini Tal Cape Survey'' programme to search for pulsational variability in CP...
Discover of the "missing" mode in HR 1217 by the Whole Earth Telescope (2001)
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 modes with alternating...
HD 12098 - A new norhtern hemisphere roAp star (2001)
Girish, V., Seetha, S., Martinez, P., Joshi, S., Ashoka, B. N., Kurtz, D. W., ...
We present the analysis of 65 hours of high speed photometric observations of HD 12098 taken from State Observatory, Naini Tal and Gurushikhar Observatory, Mt.Abu on sixteen nights spanning from...
Discovery of pulsations in HD 98851 (2001)
Joshi, S, Girish, V, Martinez, P, Sagar, R, Ashoka, B. N, Gupta, S. K, ...
Using the UPSO 1-m Sampurnanand reflector telescope equipped with a fast photometer, we observed the chemically peculiar (CP) star HD 98851 for a total of around 30 hours on 5 different nights...
HD 12098 a new far-northern roAp star (2001)
Girish, V, Joshi, S, Seetha, S, Ashoka, B. N, Martinez, P, Chaubey, U. S, ...
The rapidly oscillating Ap (roAp) stars are cool, magnetic, chemically peculiar stars which pulsate in non-radial p-modes in the period range 4-16 min and have Johnson B amplitudes less than 8 mmag....
Naini Tal-Cape survey for pulsating chemically peculiar stars - A status report (2001)
Seetha, S, Chaubey, U. S, Girish, V, Joshi, S, Ashoka, B. N, Gupta, S. K, ...
The "Naini Tal-Cape survey for rapidly oscillating Ap stars", to search the northern hemi-sphere sky for pulsating stars was initiated in 1997. This is a collaboration between India and South Africa....
Alcock, C., Allsman, R., Alves, D. R., Axelrod, T., Becker, A., Bennett, D., ...
More than 1300 variables classified provisionally as first overtone RR Lyrae pulsators in the MACHO variable star database of the Large Magellanic Cloud (LMC) have been subjected to standard...
Survey for roAp stars in the northern sky from Naini Tal (2000)
Ashoka, B. N, Seetha, S, Raj, E, Chaubey, U. S, Gupta, S. K, Joshi, S, ...
Of the 31 known rapidly oscillating Ap (roAp) stars, 28 are in the southern sky and majority of them were discovered at SAAO indicating that a systematic survey also is needed in the northern sky....
Cepheid Variables in the LMC and SMC (1999)
Alcock, C., Allsman, R. A., Alves, D. R., Axelrod, T. S., Becker, A. C., ...
In this paper, we will review major new results regarding classical Cepheids, in the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC). Specifically, we discuss recent work regarding...
Alves, D. R., Becker, A., Bennett, D. P., Cook, K. H., Freeman, K. C., ...
Using the novel data set of the MACHO project, we show that three ``Blazhko Effect'' RR Lyrae stars show nearly-pure amplitude modulation of a single pulsation mode. This is strong observational...
Some recent results for the roAp stars (1998)
Three topics are discussed: 1) Photometric observations of the rapidly oscillating Ap stars have shown that the pulsation amplitude drops dramatically as a function of wavelength from the blue to the...
Understanding the Cool DA White Dwarf, G29-38 (1997)
Kleinman, S. J., Nather, R. E., Winget, D. E., Clemens, J. C., Bradley, P. A., Kanaan, A., ...
The white dwarfs are promising laboratories for the study of cosmochronology and stellar evolution. Through observations of the pulsating white dwarfs, we can measure their internal structures and...