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Special Notice #46: GW Lib fading

May 8, 2007

Reports from VSNET, as well as AAVSO observers MTH, PYG and CLW01, indicate that GW Lib is undergoing a rapid fade from its outburst. Sonoita observations show fading at 1.5mag/day, with a Vmag of about 13.1 at JD2454228.9. At the current rate, GW Lib will be back to quiescent level within a day or two. Since this is the prime time for monitoring the return of the white dwarf pulsations, we request observers to carefully monitor GW Lib during this fade. In addition, WZ Sge stars are known for echo outbursts, where the star will increase in brightness again after the fade. In other words, we are in a period where GW Lib will show lots of activity on all time scales.

You should continue to obtain S/N=50 observations, primarily with a V filter, but if you cannot do so within a minute or two exposure, then switch to unfiltered observations during this faint period. Visual observers should continue monitoring, as rebrightenings can happen on fast timescales and you may be the only observer watching when such an event starts.

The F-scale chart is ok for visual and V-band CCD observers; if you are observing at Rc or Ic, you can obtain the Rc,Ic magnitudes for stars from 9th to 14th magnitude from the SRO calibration file at

Be sure to indicate the magnitudes used in the comment field when uploading your data.

Good luck and clear skies!

Arne Henden


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