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AAVSO Special Notice #91: BZ UMa Monitoring for Polarization Measurements AAVSO HOME > publications > special notice

AAVSO Special Notice #91

BZ UMa Monitoring for Polarization Measurements
January 14, 2008

Photometric and visual observations of the dwarf novae BZ UMa are
requested this week in support of an observing run using the new
Dual-Beam Imaging Polarimeter (DBIP) on the University of Hawaii's
88-inch telescope (2.2m) on Mauna Kea.

Operators of the telescope and instrument have agreed to include   
BZ UMa in observations planned during DBIP engineering tests on
January 17, 2008 (UT). Currently, BZ UMa is in quiescence but is
approaching the end of its typical supercycle, meaning an outburst
may occur soon. Nightly visual and photometric observations until
January 16 (UT) are needed to confirm that BZ UMa is not in

Also, time series photometric observations are needed from 05:00 - 16:00
UT on January 17, 2008. The polarimeter measurements will take   
place sometime during that window, with increasing likelihood
towards the latter half of the window. We would like to have  
precise observations with high temporal resolution during the 
polarimeter exposures. Since BZ UMa will be faint and we will   
be looking for short period fluctuations, a filter is not needed.
So feel free to remove it to lower your exposure time, which
should be as short as possible to get an SNR>100.

Recent positive observations of BZ UMa:

   Date             Mag         Band      Observer
Jan. 13.2086  16.097  +/-0.106    V    KQR (Richard Kinne)   
Jan. 10.1951  16.058  +/-0.114    V    KQR (Richard Kinne )
Dec. 15.3679  16.19   +/-0.07     V    MDW (Walter J. MacDonald II)
Nov. 24.4212  16.36   +/-0.02    Unf.  BXS (Steve Brady)

Charts and a table of photometric measurements for comparison
stars can be drawn via the Variable Star Plotter. Just put in "BZ
UMa" in the form at the URL below:

BZ UMa is an enigmatic dwarf novae with properties of both a UGSU
system and an intermediate polar. The AAVSO ran observing
campaigns in 2004 and 2005 that revealed new, but inconclusive
behavior. Last year it underwent a rare superoutburst that had
previously not been observed since consistent observations of BZ
UMa began in 1976. But there is still the question of the origin
of its X-Rays, peculiar emission lines and a possible polarization
detection in 1980. We hope this polarization measurement using
modern and more sensitive equipment will help shed light on this

As per policy for AAVSO originated campaigns, if a paper results
from these observations then observers will be thanked in the
paper and significant contributors will be included as coauthors.

This Special Notice was prepared by: A. Price


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