J/A+A/544/L6 Images of two DQ white dwarfs (Vornanen+, 2012)
Photometry of two DQ white dwarfs. Search for spots.
Vornanen T., Berdyugin A.
<Astron. Astrophys. 544, L6 (2012)>
=2012A&A...544L...6V 2012A&A...544L...6V
ADC_Keywords: Stars, white dwarf ; Photometry
Keywords: white dwarfs - starspots - stars: atmospheres
Abstract:
The intensity profiles of the C2 Swan bands in cool DQ white dwarfs
cannot be adequately fitted with models that otherwise succesfully
reproduce spectral features of the molecule CH in these stars. Initial
modelling showed that a two-component atmosphere in the style of a
spot might be able to solve the problem.
We photometrically observed the two cool DQ white dwarfs GJ1117 and
EGGR78 to search for variability caused by stellar spots.
We have not found any such variability, but we estimate the effects of
hypothetical spots on lightcurves. We also estimate detection
probabilities for spots in different configurations. Alternative
explanations of the problem are needed and briefly discussed.
Description:
For our observations we used the 35cm Schmidt-Cassegrain Celestron
telescope attached to the side of the 60cm KVA (Kungliga
Vetenskapsakademien) telescope in Observatorio del Roque de Los
Muchachos (ORM) on the island of La Palma in the Canary Islands.
Objects:
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RA (2000) DE Designation(s)
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11 18 15.11 -03 14 05.9 EGGR78 = EGGR 78
08 59 14.76 +32 57 12.1 GJ1117 = GJ 1117
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 31 25 Observing log
fits/* . 25 Directories with FITS images
images.dat 51 882 List of all FITS images, in "fits" subdirectory
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Name Star name
9- 18 A10 "YYYY-MM-DD" Date Observation date
20- 21 I2 --- NB Number of B images
23- 24 I2 --- NR ? Number of R images
26- 31 I06 --- Dir Directory containing the fits images in
subdirectory fits
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Byte-by-byte Description of file: images.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Name Star name ("EGGR78" or "GJ1117")
8 A1 --- F [BR] Filter (B or R)
10- 31 A22 --- FileName Name of FITS file, in "fits" subdirectory
33- 51 A19 "datime" ObsDate Date and time of observation
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Acknowledgements:
Tommi Vornanen, ttvorn(at)utu.fi
(End) Patricia Vannier [CDS] 03-Aug-2012