Photometry of two DQ white dwarfs. Search for spots

@article{Vornanen2012PhotometryOT,
  title={Photometry of two DQ white dwarfs. Search for spots},
  author={Tommi Vornanen and Andrei V. Berdyugin},
  journal={Astronomy and Astrophysics},
  year={2012},
  volume={544}
}
Swan bands in cool DQ white dwarfs cannot be adequately fitted with models that otherwisesuccesfully reproduce spectral features of the molecule CH in these stars. Initial modelling showed that a two-component atmospherein the style of a spot might be able to solve the problem.Methods.We photometrically observed the two cool DQ white dwarfs GJ1117 and EGGR78 to search for variability caused by stellarspots.Results.We have not found any such variability, but we estimate the effects of hypothetical… 

Figures and Tables from this paper

Finding rocky asteroids around white dwarfs by their periodic thermal emission
Since white dwarfs are small, the contrast between the thermal emission of an orbiting object and a white dwarf is dramatically enhanced compared to a main sequence host. Furthermore, rocky objects

References

SHOWING 1-10 OF 10 REFERENCES
Detailed Spectroscopic and Photometric Analysis of DQ White Dwarfs
We present an analysis of spectroscopic and photometric observations of cool DQ white dwarfs based on improved model atmosphere calculations. In particular, we revise the atmospheric parameters of
Rotational period of WD 1953 - 011- A magnetic white dwarf with a star-spot
TLDR
V-band photometry of WD 1953-011 shows variations that are likely to be due to a star-spot on the MWD, analogous to a sunspot, which is affecting the temperature at the surface, and therefore its photometric magnitude.
Rotation and magnetism in white dwarfs
New rotational ephemerides for four isolated magnetic white dwarfs are derived from more than a decade of polarimetric monitoring. The stars span the period range 99 min-17.9 days and effectively
GJ 841B—THE SECOND DQ WHITE DWARF WITH POLARIZED CH MOLECULAR BANDS
We report a discovery of the circularly polarized CH A 2Δ-X 2Π and B 2Σ–-X 2Π molecular bands in the spectrum of the DQ white dwarf (WD) GJ 841B. This is only the second such object since the
Seismic evidence for the loss of stellar angular momentum before the white-dwarf stage
TLDR
It is shown that the pulsating white dwarf PG 1159-035 rotates as a solid body with the relatively long period of 33.61 ± 0.59 h, which implies that it has lost essentially all of its angular momentum, thus favouring theories which suggest important angular momentum transfer and loss in evolutionary phases before the white-dwarf stage.
Molecular magnetic dichroism in spectra of white dwarfs.
TLDR
New spectropolarimetric observations of the cool magnetic helium-rich white dwarf G99-37 and novel calculations of the magnetic dichroism appearing in molecular bands in the presence of a strong magnetic field conclude that the developed technique is an excellent tool for studying magnetic fields on cool magnetic stars.
Polarimetric Study of the Massive Interacting Binary W Serpentis: Discovery of High-Latitude Scattering Spot/Jet
We present multicolor (UBVRI) polarimetry and additional B-band CCD polarimetry of the peculiar, strongly interacting binary W Ser, with good coverage over the 14.16 day orbital period in the three
The molecular Zeeman effect and diagnostics of solar and stellar magnetic fields. III. Theoretical spectral patterns in the Paschen-Back regime
An overview of the theory of the Zeeman eect in diatomic molecules for the limiting Hund's cases (a) and (b) is given and a numerical approach for the intermediate coupling case (a{b) is developed.
Studies in astronomical time series analysis. II - Statistical aspects of spectral analysis of unevenly spaced data
Detection of a periodic signal hidden in noise is frequently a goal in astronomical data analysis. This paper does not introduce a new detection technique, but instead studies the reliability and
Least-squares frequency analysis of unequally spaced data
The statistical properties of least-squares frequency analysis of unequally spaced data are examined. It is shown that, in the least-squares spectrum of gaussian noise, the reduction in the sum of