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Photometric variability of the unique magnetic white dwarf GD 356
GD 356 is a magnetic white dwarf (B= 13 MG) that uniquely displays weakresolved Zeeman triplets of Hα and Hβ in emission. As such,GD 356 may be the only known white dwarf with some kind of chromosphere,although accretion from the interstellar medium or more exoticmechanisms cannot be ruled out. Here, we report the detection of lowamplitude (+/-~0.2 per cent) near-sinusoidal photometric (V-band)variability in GD 356, with a period of 0.0803 d (~115 min). Weinterpret this as the rotation period of the star. We model thevariability with a dark spot (by analogy with star spots) covering 10per cent of the stellar surface. It seems likely that this spot is alsothe site of the Zeeman emission, requiring the presence of a temperatureinversion. We show that the spot is never totally visible or obscured,and that both polar and equatorial spots produce good fits to the datawhen viewed at high and low inclination respectively.
| VI photometry of selected SAO stars
Johnson V- and I-band photoelectric photometry has been obtained for 158SAO stars in a continuing program in support of the Near InfraredPhotographic Sky Survey. These data are utilized in the calibration ofthe survey photographs and are presented here to assist other programsreliant upon access to photometry in the photographic infrared.
| Photometrie de la comete Arend-Roland.
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Observation and Astrometry data
| Constellation: | Pisces |
| Right ascension: | 00h18m03.61s |
| Declination: | +00°36'59.9" |
| Apparent magnitude: | 7.145 |
| Proper motion RA: | -3 |
| Proper motion Dec: | 5.7 |
| B-T magnitude: | 8.634 |
| V-T magnitude: | 7.268 |
Catalogs and designations:
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